- Selective dopamine chemosensing using silver-enhanced fluorescence
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Condensation product of salicylaldehyde and 1,3 propylenediamine becomes a diiminic Schiff base, which is oxidized by AgNO3 in alkaline solution, and in turn, stable Ag(0) is produced at room temperature. Under this condition, the solution exhibits intense silver nanoparticle enhanced fluorescence (SEF) with the em at 412 nm. Dopamine is selectively detected down to the nanomolar level via exclusive fluorescence quenching of the SEF. Dopamine-infested solution regains the fluorescence [i.e., SEF in the presence of Hg(II) ions]. Thus dopamine and Hg(II) in succession demonstrate "turn off/on" fluorescence due to the change in the scattering cross section of Ag(0) and gives a quantitative measure of dopamine in real samples. The proposed method is free from interferences of common biocompetitors.
- Ganguly, Mainak,Mondal, Chanchal,Jana, Jayasmita,Pal, Anjali,Pal, Tarasankar
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- Synthesis and in vitro antioxidant evaluation of new bis(α-aminoalkyl)phosphinic acid derivatives
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Diamines were added to arylaldehydes in ethanol, which resulted in corresponding diimines. Novel bis-1-aminophosphinic acid compounds were synthesized through the interaction of diimines and hypophosphorous acid. The new compounds were characterized by elemental analyses, FT-IR and1H,13C and31P NMR techniques. The in vitro antioxidant activity of the newly synthesized compounds were measured and found to exhibit significantly higher antioxidant activity than the standard.
- Sarac, Kamiran,Orek, Cahit,Cetin, Ahmet,Dastan, Taner,Koparir, Pelin,Dastan, Sevgi Durna,Koparir, Metin
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- Hetero-metallic trinuclear nickel(II)-cadmium(II) complexes of a salicylaldimine ligand with thiocyanate, cyanate and azide ions: Isolation of a pair of polymorphs with thiocyanate ion
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Four new trinuclear hetero-metallic nickel(II)-cadmium(II) complexes [(NiL)2Cd(NCS)2] (1A and 1B), [(NiL)2Cd(NCO) 2] (2) and [(NiL)2Cd(N3)2] (3) have been synthesized using [NiL] as a so-called "ligand complex" (where H2L = N,N′-bis(salicylidene)-1,3-propanediamine) and structurally characterized. Crystal structure analyses reveal that all four complexes contain a trinuclear moiety in which two square planar [NiL] units are bonded to a central cadmium(II) ion through double phenoxido bridges. The Cd(II) is in a six-coordinate distorted octahedral environment being bonded additionally to two mutually cis nitrogen atoms of terminal thiocyanate (in 1A and 1B), cyanate (in 2) and azide (in 3). Complexes 1A and 1B have the same molecular formula but crystallize in very different monoclinic unit cells and can be considered as polymorphs. On the other hand, the two isoelectronic complexes 2 and 3 are indeed isomorphous and crystallize only in one form. Their conformation is similar to that observed in 1A.
- Das, Lakshmi Kanta,Drew, Michael G.B.,Ghosh, Ashutosh
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- Preparation and structural characterization of hetero-dinuclear Schiff base copper(II)-zinc(II) complexes and their inhibition studies on Helicobacter pylori urease
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A series of hetero-dinuclear CuII-ZnII complexes, [CuZnCl2L1] (1), [CuZnCl2L2] (2), [CuZnBr2L3] (3), [CuZnBr2L4(DMF)] (4), [CuZnCl2L4] (5), [CuZnCl2L5] (6), [CuZnCl2L3] (7) and [CuZnBr2L1] (8), where L1, L2, L3, L4 and L5 are the deprotonated forms of N,N′-bis(3-ethoxysalicylidene) -1,3-propanediamine (H2L1), N,N′-bis(2- hydroxynaphthylmethylidene)-1,3-propanediamine (H2L2), N,N′-bis(3-methoxysalicylidene)-1,3-propanediamine (H2L 3), N,N′-bis(salicylidene)-1,3-propanediamine (H 2L4) and N,N′-bis(salicylidene)-1,4-butanediamine (H2L5), respectively, have been synthesized and characterized by physico-chemical methods and single-crystal X-ray diffraction. The complexes were tested for their urease inhibitory activity. Complexes 1 and 8 show effective urease inhibitory activity with IC50 values of 2.2 and 10.7 μM. The molecular docking study of the complexes with the Helicobacter pylori urease was performed.
- You, Zhong-Lu,Lu, Yao,Zhang, Na,Ding, Bo-Wen,Sun, Hui,Hou, Peng,Wang, Che
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- The impact of anion-modulated structural variations on the magnetic coupling in trinuclear heterometallic CuII-CoII complexes derived from a salen-type Schiff base ligand
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Three new trinuclear heterometallic [(CuIIL)2Co IIX2] complexes [H2L = N,N′- bis(salicylidene)-1,3-propanediamine and X = thiocyanate (1), benzoate (2), or azide (3)] have been synthesized by reacting the metalloligand [CuL] with Co(ClO4)2·6H2O and the NH 4+ or Na+ salt of the corresponding anion in methanol. Structural characterization reveals that the central CoII ion is connected to two terminal metalloligands through μ1,1- diphenoxido bridges in all three complexes. However, two monodentate thiocyanato ions, which are mutually cis coordinated to the Co atom in 1, generate a "bent" structure, whereas the trans-coordinated syn-syn bridging benzoato (1κO:2κO′) and the end-on bridging azido (μ1,1) coligands in 2 and 3, respectively, produce linear structures. The changes in the number and nature of the bridges with a shortening of the distances between the metal centers leads to a concomitant decrease of the average CuII-O-CoII bridging angle from 99.3(2) to 97.1(4) and 91.5(1)° for 1, 2 and 3, respectively. Variable-temperature magnetic susceptibility measurements show the presence of a dominant antiferromagnetic coupling between the Cu-Co pairs in all three complexes. However, a steady decrease of the magnitude of the exchange coupling constant (JCu-Co) is observed from -33.4 (for 1) to -11.4 (for 2) and -2.15 cm-1 (for 3). This trend suggests that larger Cu-O-Co angles are associated with stronger antiferromagnetic coupling. Anion-mediated geometrical variations generate three heterometallic complexes with distinct trinuclear Cu2Co cores as a result of different diphenoxido bridging angles between the CuII and CoII ions. Magnetic studies reveal decreased antiferromagnetic exchange interactions associated with a decrease of this bridging angle. Copyright
- Ghosh, Soumavo,Aromí, Guillem,Gamez, Patrick,Ghosh, Ashutosh
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- Antiferro- to ferromagnetic crossover in diphenoxido bridged NiII2MnII complexes derived from N2O2 donor Schiff base ligands
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Three new trinuclear NiII-MnII complexes have been synthesized using three different "metalloligands" [NiL1], [NiL2] and [NiL3] derived from the Schiff bases H2L1 = N,N′-bis(salicylidene)-1,3-pentanediamine, H2L2 = N,N′-bis(salicylidene)-1,3-propanediamine and H2L3 = N,N′-bis(salicylidene)-1,3,-diaminopropan-2-ol), respectively. In all three complexes, [(NiL1)2Mn(OOCPh)2(H2O)2]·CH3OH (1), [(NiL2)2Mn(OOCPh)2(CH3OH)2]·CH3OH (2) and [(NiL3)2Mn(OOCPh)2(H2O)2]·CH3OH (3), in addition to the double phenoxido bridge, the two terminal NiII atoms are linked to the central MnII by means of a syn-syn bridging benzoate, giving rise to a linear structure. Complex 1 with Ni-O-Mn angle of 97.35° exhibits antiferromagnetic interactions (JNi-Mn = -0.60 cm-1) whereas ferromagnetic exchange is observed in 2 and 3 (JNi-Mn = +2.00 and +1.10 cm-1 respectively) having Ni-O-Mn angle 97.34° (in 2), 97.27° (in 3). Theoretical calculations have been performed in order to understand the effect of structural parameters that can tune the magnetic properties of this type of complexes such as small differences in the Ni-O-Mn angle and/or slight variations in intermolecular contacts within the crystal.
- Seth, Piya,Figuerola, Albert,Jover, Jesús,Ruiz, Eliseo,Ghosh, Ashutosh
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- Structure and spin-spin interactions in a linear trinuclear Ni(II) complex
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[Ni3(C2H3O2)2(C 3H8NO)2L2] [(L=N,N'-1,3-propyl-disalicylaldimine), (C2H3O2)=acetate, (C3H8NO)=hydroxymethyl-dimethylamine] has been synthesized and ils crystal structure determined, [C44H54N6O10Ni3], triclinic, space group P1?, a = 9.560(1), b = 10.681(1), c = 12.200(1) ?, α = 112.17(1), β = 101.25(1), γ = 90.32(1)°, V = 1127.3 ?3 Z = 1. The molecule is linearly trinuclear with octahedral coordination of each nickel ion. The Ni-Ni distance is 3.048(1) ?. Each nickel(II) atom is in an octahedral coordination. Magnetic susceptibility measurements in the range 4.2 1 = -2.2 cm-1) and between the terminal Ni atoms (J2 = -1.7 cm-1).
- Elmali, Ayhan,Elerman, Yalcin,Svoboda, Ingrid,Fuess, Hartmut,Griesar, Klaus,Haase, Wolfgang
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- An investigation of some Schiff base derivatives as chemosensors for Zn(II): The performance characteristics and potential applications
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The fluorescence properties of four simple Schiff bases (LH2, LDMH2, LH2 H and LDMHH2) and their potential application as chemosensors for the detection of zinc ion in aqueous solution have been investigated. While LH2 and LDMH2 have displayed specific recognition to Zn(II), the reduced derivatives (LH2 H and LDMHH2) of these ligands have shown no fluorescence response due to the lack of C[dbnd]N group. The Job plots, fluorescence titration experiments and ESI-MS results indicate the formation of 1:1 complexes between sensors and Zn(II). The analytic methods based on LH2 and LDMH2 as chemosensors have been proposed and optimized to detect Zn(II) ions in aqueous solution. The optimized methods have shown a good range of linearity, high precision, good accuracy and low detection limit. As an alternative to these methods, LH2 and LDMH2 have the capability to detect Zn(II) ions by naked eye under UV lamp. Moreover, LH2-Zn and LDMH2-Zn complexes have the ability to be a staining agent for identifying the radiation treatment of food by DNA comet assay.
- Ergun, Ece,Ergun, ümit,?leri, ?zgür,Kü?ükmüzevir, Muhammed Fatih
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- Rare trinuclear NiII2MII complexes (MII?=?Mn, Fe and Co) with a reduced Schiff base ligand: Synthesis, structures and magnetic properties
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Three new trinuclear hetero-metallic NiII2MII complexes with MII = Mn, Fe and Co have been synthesized using a [NiLR] “metalloligand”, where H2LR = N,N′-bis(2-hydroxybenzyl)-1,3-propanediamine. All complexes have been characterized by elemental analysis, spectroscopic methods, single crystal XRD and magnetic and electrochemical studies. In the three complexes, in addition to the double phenoxido bridges, the two terminal NiII atoms are linked to the central MII [M = Mn(1), Fe(2) and Co(3)] ion by means of a bridging carboxylato co-anion, giving rise to a linear NiII-MII-NiII structure. Variable temperature magnetic susceptibility measurements show the presence of weak ferromagnetic and antiferromagnetic exchange interactions mediated through the double phenoxido bridges with J values of +8.5 and ?3.0 cm?1 for complexes 1 and 2, respectively. Compound 3 shows the presence of antiferromagnetic interactions. Cyclic voltammetry shows a common quasi-reversible one electron oxidation corresponding to the Ni(II)/Ni(III) process in 1–3 and an irreversible M(II)/M(III) oxidation for Mn(1) and Fe(2).
- Hazari, Alokesh,Ghosh, Tanmoy Kumar,Gómez-García, Carlos J.,Ghosh, Ashutosh
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- Kinetics and mechanism of the ligand exchange reaction between tetradentate schiff base N,N'-ethylen-bis (salicylaldimine) and Ni(N,N'-propylen-bis(salicylaldimine))
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Visible spectrophotometry is used to study the kinetics of ligand exchange in the system Ni(salpn)/H2salen with or without triethylamine (NEt3) and H2O in dimethylformamide (DMF) solvent at 25 ± 0.1 °C and 0.01MNaNO3 [H2salen and H2salpn are N,N'-ethylen-bis(salicylaldimine) and N,N'-propylen-bis(salicylaldimine), respectively]. It was found that the reaction rate is of the first-order with respect to Ni(salpn). In addition, the effect of NEt3 andH2Oon the rate of the reaction was examined. The rate of the ligand exchange reaction was accelerated by adding NEt3 to the reaction mixture. However, the ligand exchange rate was not changed by adding H2O to the mixture reaction. The effects of NEt3 and H2O on the ligand exchange rate show that deprotonation/protonation of the H2salen ligand and anionic form of H2salen is important. On the basis of these results, the reaction mechanism is discussed.
- Vafazadeh, Rasoul,Bagheri, Maryam
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- The effect of electronegativity upon the coordination sphere; heterodinuclear Ni(II) complexes with ONNO type Schiff bases, octahedral, square pyramidal and square planar coordination of Ni(II)
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NiL.MX2 heterodinuclear complexes with a nuclear structure of NiII-MII (M = Zn, Cd, X = Cl, Br, I) were prepared in the dioxane medium by the use of an ONNO type ligand, Bis-N,N′(salicylidene)-1,3-propanediamine (LH2). The complexes prepared were characterized by the use of infrared (IR) spectroscopy, thermogravimetry (TG), semi-micro nitrogen, metal and halogen analysis. The molecular structures and unit cell properties of the compounds were elucidated by the X-ray diffraction (XRD) method. In parallel to the literature, MX2 group was observed to form μ? bridges with the phenolic oxygens of the organic ligand. The coordination sphere of NiL heterodinuclear complex in NiL group was observed to change depending upon the electronegativities of the atoms in MX2 group. The electronegativities of the atoms in the MX2 group affect the coordination sphere of NiL group of the heterodinuclear complex, and in parallel with the electronegativities of the atoms in MX2 group, it was observed that NiL unit coordinated the solvent molecules and the coordination sphere changed. In addition to this, the coordination bonds get smaller as the number of donor atoms nearby NiL decreased. Using Gaussian 09 software, the theoretical bond lengths and bond angles were calculated and compared with the experimental data. With Gaussian 09 software, it was determined how the occupancy levels of d orbitals of the metal atoms changed by coordination of Ni(II) ion. Also, the change of the differences between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) levels of the complexes was monitored.
- ?nal, Emine Kübra,Acar, Nurcan,Atakol, Orhan,Gürp?nar, Kübra,Gürsoy Tuncer, Yaprak,Naz?r, Hasan,Svoboda, Ingrid
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- Structural and Magnetic Analysis of Retrosynthetically Designed Architectures Built from a Triply Bridged Heterometallic (CuL)2Co Node and Benzenedicarboxylates
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The flexible trinuclear metallatecton {(CuL)2Co}2+ [H2L = N,N′-bis(salicylidene)-1,3-propanediamine] has been used as a building block, and its coordinative interaction with ortho-, meta-, and para-benzenedicarboxylates (BDCs) has been investigated to evaluate the positional isomeric effect of these carboxylate ligands on the resulting compounds. Structural characterization reveals that o-H2BDC produces a discrete trinuclear complex, namely [(CuL)2Co(o-HBDC)2]·H2O (1). As expected from the retrosynthetic design, one-dimensional (1D) coordination polymers, i.e., [{(CuL)2Co(m-BDC)}·CH3OH]∞ (2) and [{(CuL)2Co(p-BDC)}·2CH3OH]∞ (3), are obtained with m-BDC and p-BDC linkers, respectively. In all three complexes, the triply bridged bimetallic trinuclear coordination clusters are linear and solely a syn-syn bridging mode is observed for the carboxylates. In 2, the nodes are connected sidewise and are inclined toward each other to be accommodated by the 120-angular m-BDC units, whereas in 3, the linear p-BDC linkers connect the parallel nodes diagonally. These differences in connectivity give rise to one-dimensional "great wall"-like chains for 2 and to quasi-linear coordination chains for 3. These distinct one-dimensional propagations induced by the different BDC isomers influence the three-dimensional columnar packing of 2 and 3. Magnetic susceptibility measurements and fitting of the results confirm that these three compounds are made by analogous magnetic building blocks, with very similar antiferromagnetic intramolecular magnetic exchange (with J in the -16.96 to -11.80 cm-1 range, using the -2JS1S2 convention). The structural homogeneity of the magnetic fragment within this family of compounds has allowed magnetostructural correlations to be explored, which has not previously been attempted.
- Ghosh, Soumavo,Aromí, Guillem,Gamez, Patrick,Ghosh, Ashutosh
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- Playing with different metalloligands [NiL] and Hg to [NiL] ratios to tune the nuclearity of Ni(II)-Hg(II) complexes: Formation of di-, tri-, hexa- and nona-nuclear Ni-Hg clusters
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Five new hetero-metallic nickel(II)-mercury(II) complexes, [(NiL1)HgCl2] (1), [(NiL1)2HgCl2] (3), [(NiL1)2Hg(N3)2] (4), [{(NiL2)2Hg(N3)(μ1,1-N3)}2] (5) and [{(NiL2)2Hg(N3)(μ1,1-N3)HgCl2}2{Hg(N3)(μ1,1-N3)}] (6) have been synthesized by reacting metalloligands [NiL1] or [NiL2] (where H2L1 is N,N′-bis(salicylidene)-1,2-ethylenediamine and H2L2 is N,N′-bis(salicylidene)-1,3-propanediamine) with HgX2 (X- = Cl- or N3-) at different molar ratios. All five complexes have been characterised by X-ray single-crystal structural, elemental and spectroscopic analyses. In complex 1, the Hg(II) ion is coordinated to two phenoxido oxygen atoms of one [NiL1] moiety and two terminal chloride ions to form a NiHg dinuclear complex. In the trinuclear complexes 3 and 4, the central Hg(II) ion is coordinated by two terminal [NiL1] units through two phenoxido oxygens from each and two terminal chloride (in 3) or azide (in 4) ions. The centrosymmetric hexanuclear complex 5 consists of two trinuclear [(NiL2)2Hg(N3)(μ1,1-N3)] units, where the phenoxido bridges connect two terminal Ni(II) atoms of the trinuclear units. In these trinuclear units, one azido ligand adopts a μl,1-briding mode between Hg and Ni whereas the other one is terminal. In the nonanuclear complex 6, two tetranuclear [{(NiL2)2Hg(N3)(μ1,1-N3)}HgCl2] units are linked to a central Hg(II) positioned on a two fold axis, via chlorido, azido, and phenoxido bridges. The tetranuclear unit is formed by the addition of a HgCl2 molecule to a trinuclear [(NiL2)2 Hg(N3)(μ1,1-N3)] unit, similar to that present in 5. Complex 5 shows weak ferromagnetic interactions (J = +2.1 cm-1) between the two octahedral Ni(II) ions through double phenoxido bridges with a Ni-O-Ni bond angle of 95.87(11)°.
- Das, Lakshmi Kanta,Gómez-García, Carlos J.,Drew, Michael G.B.,Ghosh, Ashutosh
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- The investigations of thermal behavior, kinetic analysis, and biological activity of trinuclear complexes prepared ONNO-type Schiff bases with nitrito and nitrato μ-bridges
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By using bis-N,N′(salicylidene)-1,3-diaminopropane and reduced form of this ligand bis-N,N′(2-hydroxybenzylidene)-1,3-diaminopropane, we prepared eight trinuclear complexes in the core form of NiII–NiII–NiII and NiII–CuII–NiII. Complexes have been characterized with element analysis, IR spectroscopy and NMR spectroscopy methods and also investigated with Thermogravimetry (TG). It was observed that thermal characteristics of the complexes prepared by the reduced form of Schiff base are different from complexes prepared by the Schiff base. According to TG, two thermal reactions between 120 and 180?°C endothermic separation of coordinative dimethylformamide molecules and then around 300?°C exothermic decomposition of molecule were observed for Schiff base-prepared complexes. On the other hand, the complexes resulted from reduced Schiff base reactions were shown decomposed around 250–270?°C by exothermic thermal reaction. Kinetic parameters of decompositions were determined by isothermal and non-isothermal kinetic methods, Coats–Redfern (CR), Ozawa, Ozawa–Flynn–Wall (OFW) and Kissenger–Akahira–Sunose (KAS). Departing from these values, thermodynamic parameters were calculated and the results were interpreted. It was concluded that the complexes prepared with reduced Schiff bases are more strained structures. Biological activities of these complexes were also inspected, and antibacterial and antifungal activities were tested against four different bacterial strains (E. coli, P. aureginosa, S. aureus and E. feacalis) and a fungus species (C. albicans).
- Acar, Nurcan,Atakol, Orhan,Sopac?, ?aziye Betül,Duman, Demet Cansaran,Svoboda, Ingrid,?z, Sevi
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- Synthesis, structure and magnetic properties of Ni(II)-Co(II) heterodinuclear complexes with ONNO type Schiff bases as ligands
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Four new heterodinuclear Ni(II)-Co(II) complexes, NiL·CoCl 2·(DMF)2 (I), NiL·CoBr2· (DMF)2 (II), NiL′·CoCl2·(DMF) 2 (III) and NiLDM·CoCl2(DMF)2 (IV), have been prepared in non-aqueous DMF using the ONNO type Schiff bases N,N′-bis(2-hydroxyphenylidene)-1,3-propanediamine (LH2), N,N′-bis(2-hydroxyphenylidene)-1,4-butanediamine (L′H2) and N,N′-bis(2-hydroxyphenylidene)-2,2′-dimethyl-1,3-propanediamine (LDMH2), and the inorganic salts NiCl2 and CoCl 2. The complexes were characterized by elemental analysis, IR spectroscopy, thermogravimetry and X-ray diffraction. An XRD study revealed that the Ni(II) ion is situated at the center of a distorted octahedral coordination sphere formed by two iminic nitrogen and two phenolic oxygen atoms of the ONNO type Schiff base and two other oxygen atoms belonging to coordinated DMF molecules. On the other hand, the Co(II) ion is situated inside a distorted tetrahedral coordination sphere, members of which being the two halogen atoms and two oxygen atoms, bonded to form a μ-bridge. The magnetic susceptibility of the complexes was studied using a SQUID magnetometer between 2.0 and 300 K at B = 0.1 T, and the magnetization data were taken up to B = 7 T at T = 2.0 and 4.6 K. The exchange interaction between the metal centers is of a ferromagnetic nature (typically JCo-Ni/hc = +2 cm-1) and at low temperature single-ion zero-field splitting applies (DNi/hc = +8 cm-1, DCo/hc = +14 cm-1).
- ?z, Sevi,Titi?, Ján,Nazir, Hasan,Atakol, Orhan,Bo?a, Roman,Svoboda, Ingrid,Fuess, Hartmut
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- Hydroxide-bridged Diiron(III) Complexes of Tetraaminodiphenol Macrocyclic Ligands: Structure and Properties
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Some dinuclear iron(III) complexes derived from two tetraaminophenol macrocyclic ligands, one (H2L1) contains two -NH(CH2)3NH- and the other (H2L2) one -NH(CH2)3NH- and one -NH(CH2)2NH- units, and an acyclic tetradentate ligand 3 N,N'-bis(2-hydroxybenzyl)-1,3-diaminopropane> have been synthesised and studied.In all of the macrocyclic complexes 1)2>2 1, 12>*2H2O 2, 1)(H2O)2>3*H2O 3, 2)2>4*2H2O 4, 22>*2H2O 5 and 32> 6 only N2O2 donation to the metal centres occurs, while the two unco-ordinated amino nitrogens either remain singly protonated (2 and 5) or one (1) or both of these (3 and 4) is doubly protonated.Variable-temperature magnetic susceptibility data for 1, 4 and 6 indicate weak antiferromagnetic-exchange interactions in each case with J values of: -5.5 (1), -7.3 (4) and -11.8 cm-1 (6).The isomer-shift and quadrupole-splitting values for 1 at 77 K are 0.46 and 0.43 mm s-1, respectively.The redox chemistry of 1 has been studied by cyclic voltammetry and its crystal structure has been determined: monoclinic, space group P21/c, a = 13.448(1), b = 14.847(1), c = 13.442(1) Angstroem, β = 91.48(1) deg, Z = 2, R = 0.048 and R' = 0.050.The two edge-sharing FeO4N2 octahedra are distorted and connected by a centre of inversion.
- Nanda, Kausik K.,Dutta, Sujit K.,Baitalik, Sujoy,Venkatsubramanian, Krishnan,Nag, Kamalaksha
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- Polymorphism in hetero-metallic tri-nuclear CuII 2CdII complexes of salicylaldimine ligand: Structural analysis and theoretical study
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Three new trinuclear hetero-metallic copper(II)-cadmium(II) complexes [(CuL)2Cd (NCS)2] (1A and 1B), [(CuL)2Cd(NCO) 2] (2) have been synthesized using [CuL] as so-called "ligand complex" (where H2L = N,N′-bis(salicylidene)-1,3- propanediamine) and structurally characterized. Crystal structure analyses reveal that all three complexes have trinuclear entity in which two square planar [CuL] units are bonded to a cadmium ion through double phenoxido bridges. The Cd(II) is in a six-coordinate distorted octahedral environment being bonded additionally to two mutually cis nitrogen atoms of terminal thiocyanate (in 1A and 1B) and cyanate (in 2). Complexes 1A and 1B have the same molecular formula but crystallize in different monoclinic unit cells (P21/c for 1A and P21/n for 1B) and can be considered as polymorphs. On the other hand, complex 2 is crystallized only in one form and its conformation is similar to that observed in 1A. A theoretical investigation shows that 1A is slightly more (2.25 kcal/mol) stable than 1B. However, in the crystal lattice, 1A establishes a C-H/π interaction while 1B interacts through a C-H···S hydrogen bond to form dimer and the more favorable dimerization energy in the later (ca. 3 kcal/mol) compensates the difference in the relative energy of the polymorphs. Complex 2 crystallizes only in one form and conformation of the molecule is similar to 1A. Analyses of the noncovalent interactions of 2 show a weakening of the dimerization energy compared to 1A or 1B. Moreover, the H-bonding interaction that facilitates the formation of 1B is unlikely to be established in 2. Therefore this polymorph is not isolated.
- Das, Lakshmi Kanta,Biswas, Apurba,Frontera, Antonio,Ghosh, Ashutosh
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- Exploring the coordinative adaptation and molecular shapes of trinuclear Cu II 2 MII (M = Zn/Cd) complexes derived from salen type Schiff bases: Structural and theoretical studies
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Three new trinuclear hetero-metallic complexes [(CuL)2Zn(NCS)2] (1), [(CuLR)2Zn(NCS)(μ1,1-NCS)] (2) and [(CuLR)2Cd(μ1,3-NCS)2] (4) have been synthesized using [CuL] and [CuLR] as "metalloligands" (where H2L = N,N′-bis(salicylidene)-1,3-propanediamine and H2LR = N,N′-bis(2-hydroxybenzyl)-1,3-propanediamine). All three complexes are characterized by elemental analysis, spectroscopic methods and single crystal XRD. Complex 1 is an angular trinuclear species, in which two terminal four-coordinate square planar "metalloligands" [CuL] are coordinated to a central Zn(ii) through double phenoxido bridges along with two mutually cis nitrogen atoms of terminal isothiocyanate ions as is usually found in such complexes. In contrast, in complex 2, the two terminal "metalloligands" [CuLR] are square pyramidal, as one of the SCN- ions makes an unusual μ1,1-NCS bridge between copper centers while the other one coordinates to Zn(ii) through a N atom in a usual fashion making its geometry also square pyramidal. For 4 which possesses an angular trinuclear structure, in addition to double phenoxido bridges from two terminal [CuLR], both the SCN- ions are S-bonded to Cd(ii) and form a bridge (cis-μ1,3-SCN) between Cd(ii) and each of the terminal Cu(ii) ions. This structure is different from its unreduced analogue in which NCS- was N-terminal coordinated to Cd(ii) (3/3′). All the structures have been optimized using density functional theory (DFT) calculations. It has been found that for H2L, optimized structures like 1 and 2 differ only by 0.4 kcal mol-1 but the H2LR structure 2 is more stable by 5.5 kcal mol-1 than the structure resembling 1. For Cd(ii) complexes also, H2L optimized structures such as 3 and 4 do not differ significantly in energy (1.0 kcal mol-1) but the H2LR structure 4 is more stable than that of 3 by 4.6 kcal mol-1. In fact, structure 4 has been found to be the most stable one among the other possible isomers of H2LR.
- Hazari, Alokesh,Das, Lakshmi Kanta,Bauzá, Antonio,Frontera, Antonio,Ghosh, Ashutosh
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- Isolation of two different Ni2Zn complexes with an unprecedented cocrystal formed by one of them and a "coordination positional isomer" of the other
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A new homometallic trinuclear Ni(II) complex [(NiL)2Ni(NCS) 2] (1) and three heterometallic trinuclear Ni(II)-Zn(II)-Ni(II) complexes [(NiL)2Zn(NCS)2] (2), [(NiL)2Zn(NCS) 2(CH3OH)2]·2CH3OH (3) and {[(NiL)2Zn(NCS)2(CH3OH)2]} {[(NiL)2Zn(NCS)2]} (4) have been synthesized by using the "complex as ligand" approach with the "metalloligand" [NiL] (H2L = N,N′-bis(salicylidene)-1,3-propanediamine) and thiocyanate in different ratios. All the complexes have been structurally and magnetically characterized. In the isomorphous complexes 1 and 2, the two terminal square planar Ni atoms and the central octahedral nickel atom (in 1) or zinc atom (in 2) are arranged in a bent structure where two cis κN-SCN- thiocyanate ions are coordinated to the central atom. The chemical composition of 3 is very similar to that of 2 but, in 3, the central Zn atom is tetrahedral and the κN-SCN- thiocyanate ions occupy an axial position of each terminal nickel atom (which now are octahedral with the sixth position occupied by a methanol molecule). Complex 4 consists of two closely related trinuclear units 4A and 4B. In 4A, the coordination environments of the metals are identical to those of 3 whereas 4B is a "coordination position isomer" of complex 2 with the central square pyramidal Zn and one of the terminal square pyramidal Ni atoms coordinated by two κN-SCN- thiocyanate ions. Complex 4 is a unique example of a cocrystal formed by two similar trinuclear units (4A and 4B) where 4A is identical to an existing complex (3) and 4B is a "coordination position isomer" of another existing complex (2).
- Das, Lakshmi Kanta,Biswas, Apurba,Gomez-Garcia, Carlos J.,Drew, Michael G.B.,Ghosh, Ashutosh
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- An unprecedented "linear-bent" isomerism in tri-nuclear Cu 2IIZnII complexes with a salen type di-Schiff base ligand
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Two new trinuclear hetero-metallic copper(ii)-zinc(ii) complexes [(CuL)2Zn(N3)2] (1A and 1B) have been synthesized using [CuL] as a so-called "metalloligand" (where H 2L = N,N′-bis(salicylidene)-1,3-propanediamine) and structurally characterized. Complexes 1A and 1B have the same molecular formula but crystallize in different crystal systems (triclinic for 1A and monoclinic for 1B) with space group P1 for 1A and P21/c for 1B. 1A is an angular trinuclear species, in which two terminal four-coordinate square planar "metalloligand" [CuL] are coordinated to a central Zn(ii) through double phenoxido bridges. The Zn(ii) is in a six-coordinate distorted octahedral environment being bonded additionally to two mutually cis nitrogen atoms of terminal azide ions. In complex 1B, in addition to the double phenoxido bridge, the two terminal Cu(ii) ions are linked to the central Zn(ii) via a μ-l,l azido bridge giving rise to a square pyramidal environment around the Cu(ii) ions and consequently the structure becomes linear. These two species can be considered as "linear-bent" isomers. EPR spectra and ESI mass spectra show that the two isomers are identical in solution. The DFT calculation reveals that the energy of 1A is 7.06 kcal mol-1 higher than that of 1B. The existence of both isomers in the solid state suggests that crystal packing interactions in 1A are more efficient and probably compensate for the difference in energy.
- Das, Lakshmi Kanta,Park, Sung-Woo,Cho, Seung Joo,Ghosh, Ashutosh
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- Diiminic Schiff bases: An intriguing class of compounds for a copper-nanoparticle-induced fluorescence study
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The condensation products of salicylaldehyde and different diamines constitute an important class of diiminic Schiff bases (DSBs). This class of compounds has been rediscovered as reducing as well as capping agents under UV irradiation. UV irradiation of alkaline DSB solutions in the presence of water-soluble copper salts has been employed to produce copper nanoparticles (CuNPs). Intriguing CuNP-stimulated fluorescence behavior of the solution has been observed. Depending upon the nature of the spacer in between two iminic bonds, fluorescence enhancement or quenching is observed. Such surprising fluorescence contrast has been ascribed to far-field radiation and lossy surface waves. Making light of things: UV irradiation of alkaline diiminic Schiff base (DSB) solutions in the presence of water-soluble copper salts has been employed to produce copper nanoparticles (CuNPs). Fluorescence enhancement of the exposed DSBs was observed in the presence of in situ produced Cu0 (see figure). Copyright
- Ganguly, Mainak,Pal, Anjali,Negishi, Yuichi,Pal, Tarasankar
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- Two dinuclear NiII–CdII complexes of reduced ONNO-type Schiff bases: Synthesis, crystal structures, thermal kinetic analysis and DFT studies
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Two ONNO-type Schiff bases, bis-N,N′-(salicylidene)-1,3-diaminopropane and bis-N,N′-(2-hydroxyacetophenylidene)-1,3-propanediamine, were reduced using NaBH4 and converted to two phenol–amine-type tetradentate ligands, bis-N,N′-(2-hydroxybenzyl)-1,3-diaminopropane (LHH2) and bis-N,N′-[1(2-hydroxyphenyl)ethyl]-1,3-diaminopropane (LACHH2). These ligands were used to prepare two NiII–CdII heterodinuclear complexes, namely [DMF·NiLH·CdI2·DMF] and [DMF·NiLACH·CdBr2·DMF] in DMF medium. The molecular structure and unit cells of these complexes have been elucidated by the use of X-ray diffraction data. The thermogravimetric analysis of the compounds revealed that as the temperature is increased, the first coordinative DMF molecule was removed from the structure followed by a second coordinative DMF molecule with the complete decomposition of the complex. The activation energies and Arrhenius pre-exponential factor of these thermal reactions were determined by the use of isothermal Coats–Redfern, nonisothermal Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose methods. The results obtained for the first thermal reaction were similar since the structure of both complexes remained intact during this process. Also, the theoretical calculations of the bond lengths, bond angles and natural bond orbital analysis of both complexes were carried out using the algorithms embedded in Gaussian 09 software.
- S?nmez,Nazir,Emir,Svoboda,Aksu,Atakol
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- Synthesis, crystal structure, theoretical calculations and thermal characterization of two heterodinuclear NiII–ZnII complexes prepared from ONNO-type symmetrical Schiff base and its reduced derivative
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Two complexes in NiII–ZnII heterodinuclear form were prepared in DMF medium by the use of an ONNO-type symmetrical Schiff base bis-N,N′(salicylidene)-1,3-diaminopropane (LH2) and the reduced derivative of this ligand bis-N,N′(2-hydroxybenzylidene)-1,3-diaminopropane (LHH2). The fact that the complexes are in [NiL·ZnCl2·DMF2] and [NiLH·ZnCl2·(DMF)2] stoichiometry was verified with elemental and thermogravimetric analyses and IR spectroscopy. The structures of the complexes were determined by the use of X-ray diffraction. The two complexes were very similar, almost isostructure, and it was observed that Ni(II) ions in both complexes coordinated with two phenolic oxygens and two iminic nitrogen of organic ligand and formed an octahedral coordination between two DMF molecules. On the other hand, the Zn(II) ion was observed to be located in a tetrahedral coordination sphere coordinated with two phenolic oxygens between two halides. Although the molecular structures of the complexes are very similar, their thermal properties are quite different from of each other. The decomposition of [NiL·ZnCl2·(DMF)2] was observed between 140 and 190?°C by the removal of coordinative DMF molecules, leaving a residue of a mixture of NiL and ZnCl2 behind. The complex of the reduced ligand [NiLH·ZnCl2·(DMF)2] was observed to be stable up to 250?°C. After this temperature, the coordinative DMF molecules rapidly leave the structure before the degradation of NiLH. That is why the activation energies of the thermal reactions were evaluated by the use of isothermal and nonisothermal kinetic models: Coats–Redfern, Ozawa, Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose. Also the thermal differences between these two complexes were examined by the use of theoretical programs included in Gaussian 09 package. The ground-state energies calculations were carried out by the use of density functional theory method 631G(d) basis set. The calculated theoretical bond energies and angles were observed to be different compared with the experimental data. The HOMO and LUMO values of the complexes were also calculated. The difference between these two complexes was evaluated.
- Atakol, Arda,Nazir, Hasan,Svoboda, Ingrid,Aksu, M. Levent,Atakol, Orhan
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- Ferro- to antiferromagnetic crossover angle in diphenoxido- and carboxylato-bridged trinuclear NiII2-MnII complexes: Experimental observations and theoretical rationalization
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Three new trinuclear heterometallic NiII-MnII complexes have been synthesized using a [NiL] metalloligand, where H 2L = N,N′-bis(salicylidene)-1,3-propanediamine. The complexes [(NiL)2Mn(OCnn)2(CH3OH)2] ·CH3OH (1), [(NiL)2Mn(OPh)2(CH 3OH)2][(NiL)2Mn(OPh)2]·H 2O (2), and [(NiL)2Mn(OSal)2(CH 3OH)2]·2[NiL] (3) (where OCnn = cinnamate, OPh = phenylacetate, OSal = salicylate) have been structurally characterized. In all three complexes, in addition to the double phenoxido bridge, the two terminal NiII atoms are linked to the central MnII by means of a syn-syn bridging carboxylate, giving rise to a linear structure. Complexes 1 and 2 with Ni-O-Mn angles of 97.24 and 96.43°, respectively, exhibit ferromagnetic interactions (JNi-Mn = +1.38 and +0.50 cm-1, respectively), whereas 3 is antiferromagnetic (JNi-Mn = -0.24 cm-1), having an Ni-O-Mn angle of 98.51°. DFT calculations indicate that there is a clear magneto-structural correlation between the Ni-O-Mn angle and JNi-Mn values, which is in agreement with the experimental results.
- Seth, Piya,Figuerola, Albert,Jover, Jesus,Ruiz, Eliseo,Ghosh, Ashutosh
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- Salen and tetrahydrosalen derivatives act as effective inhibitors of the tumor-associated carbonic anhydrase XII - A new scaffold for designing isoform-selective inhibitors
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Salen and tetrahydrosalen derivatives possess metal-chelating properties and have been used as ligands in organic synthesis and as scaffolds for developing therapeutic agents. Fourteen such compounds were synthesized in order to explore their ability to inhibit the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1). Human (h) isoforms hCA I, hCA II, hCA IX and hCA XII were included in the investigation. Several aliphatic and aromatic spacers were introduced between the two chelating groups from salen/tetrahydrosalen in order to explore a diverse chemical space for designing CA inhibitors, which incorporate both phenol and polyamine fragments in their molecule. Some of these compounds showed CA inhibitory activity in the low micromolar-nanomolar range and a pronounced selectivity for inhibiting an isoform over-expressed in hypoxic tumors, hCA XII, over hCA I, II and IX.
- Carradori, Simone,De Monte, Celeste,D'Ascenzio, Melissa,Secci, Daniela,Celik, Gulsah,Ceruso, Mariangela,Vullo, Daniela,Scozzafava, Andrea,Supuran, Claudiu T.
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- Solvent-templated supramolecular isomerism in 2D coordination polymer constructed by NiII2CoII nodes and dicyanamido spacers: Drastic change in magnetic behaviours
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Two heterometallic coordination polymers (CPs) have been prepared using [NiIIL]2CoII (where H2L = N,N′-bis(salicylidene)-1,3-propanediamine) as nodes and dicyanamido spacers by varying the solvent for synthesis. Structural characterizations revealed that methanol assisted the formation of a two-dimensional (4,4) connected rhombic grid network of [(NiL)2Co(NCNCN)2] ∞ (1a) whereas relatively less polar acetonitrile afforded a different superstructure {[(NiL)2Co(NCNCN)2] ·CH3CN}∞ (1b) with a two-dimensional (4,4) connected square grid network. The presence of acetonitrile molecules in the structure of 1b seems to change the spatial orientation of the terminal metalloligands [NiL] from pseudo-eclipsed in 1a to staggered-like in 1b around the central Co(ii). These structural changes in the nodes together with the conformationally flexible dicyanamido spacers, which are cis coordinated to the Co(ii) in both trinuclear units, led to the differences in the final 2D network. Variable-temperature magnetic susceptibility measurements revealed that this supramolecular isomerism led to a drastic transition from spin-frustrated antiferromagnetism for 1a to a dominant ferromagnetic behaviour for 1b. The geometrical differences in Ni2Co coordination clusters (CCs) which are scalene triangular in 1a but nearly linear in 1b, are held responsible for the changes of the magnetic properties. The DFT calculations of exchange interactions between metal centres provide a clear evidence of the role played by the fundamental geometrical factors on the nature and magnitude of the magnetic coupling in these pseudo-polymorphic CPs.
- Ghosh, Soumavo,Mukherjee, Sandip,Seth, Piya,Mukherjee, Partha Sarathi,Ghosh, Ashutosh
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- Functional model for catecholase-like activity: A mechanistic approach with manganese(III) complexes of salen type Schiff base ligands
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Three new Mn(III) complexes [MnL1(OOCH)(OH2)] (1), [MnL2(OH2)2][Mn2L2 2(NO2)3] (2) and [Mn2L 21(NO2)2] (3) (where H 2L1 = H2Me2Salen = 2,7-bis(2-hydroxyphenyl)-2,6-diazaocta-2,6-diene and H2L2 = H2Salpn = 1,7-bis(2-hydroxyphenyl)-2,6-diazahepta-1,6-diene) have been synthesized. X-ray crystal structure analysis reveals that 1 is a mononuclear species whereas 2 contains a mononuclear cationic and a dinuclear nitrite bridged (μ-1κO:2κO′) anionic unit. Complex 3 is a phenoxido bridged dimer containing terminally coordinated nitrite. Complexes 1-3 show excellent catecholase-like activity with 3,5-di-tert-butylcatechol (3,5-DTBC) as the substrate. Kinetic measurements suggest that the rate of catechol oxidation follows saturation kinetics with respect to the substrate and first order kinetics with respect to the catalyst. Formation of bis(μ-oxo)dimanganese(III,III) as an intermediate during the course of reaction is identified from ESI-MS spectra. The characteristic six line EPR spectra of complex 2 in the presence of 3,5-DTBC supports the formation of manganese(II)-semiquinonate as an intermediate species during the catalytic oxidation of 3,5-DTBC.
- Seth, Piya,Drew, Michael G.B.,Ghosh, Ashutosh
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- Structure of μ-oxo-bis{{2,2′-[propane-1,3-diylbis (aminomethyl)]diphenolato}oxorhenium(V)}
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In the title compound, C34H40N407Re 2, each of the two Re(V) atoms is hexacoordinated by two amine nitrogens, two phenol oxygens, and two axial oxygens. The compound is a binuclear complex with an O=Re-O-Re=O backbone and nearly octahedral coordination geometry at each Re atom. The Re=O bond distance is 1.720(14) A and the Re-O bridge bond distance is 1.938(12) A. The equatorial plane Re-O bond distances are 1.992(14) and 2.012(13) A, whereas the Re-N bond distances are 2.129(15) and 2.187(16) A.
- Huang, Wen-Tao,Yao, Hsueh-Hua,Chen, Bor-Hann,Liao, Fen-Ling,Lo, Jem-Mau
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- Synthesis, crystal structure, thermal decomposition, and XPS studies of homo and heterotrinuclear Cu(II)–Cu(II)–Cu(II) and Cu(II)–Ni(II)–Cu(II) complexes obtained from salpn type ligands
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In this study, a mononuclear CuL complex was prepared by the use of bis-N,N′-(salicylidene)-1, 3-propanediamine (LH2) and Cu2+ ion. NiCl2 and NiBr2 salt were treated with this complex in dioxanewater medium and two new complexes [(CuL)2NiCl2(H2O)2] and [(CuL)2NiBr2(H2O)2)] with Cu(II)–Ni(II)–Cu(II) nucleus structure were obtained. In addition to this bis-N,N′-(2-hydroxybenzyl)-1,3-diaminopropane (LHH2) was prepared by the reduction of LH2 with NaBH4 in MeOH medium. The treatment of this reduced complex with Cu2+ ion resulted a complex [(CuLH)2CuCl2] with a structure of Cu(II)–Cu(II)–Cu(II). The complexes prepared were characterized by the use of elemental analysis, IR spectroscopy, thermogravimetric and X-ray diffraction methods. The crystal structures of [(CuL)2NiBr2(H2O)2] (СIF file CCDC 1448402) and [(CuLH)2CuCl2] (СIF file CCDC 1448401) complexes were elucidated. It was found that halogen ions are coordinated to terminal Cu2+ ions which are in a distorted square pyramid coordination sphere. It was determined that the central Cu(II), which joins terminal square pyramidal Cu(II), was coordinated only by the phenolic oxygens of the ligand while the central Ni(II) was coordinated by two phenolic oxygens of the organic ligand and two water molecules. These complexes were investigated by XPS and it was found that the terminal and central Cu2+ ions were different in Cu(II)–Cu(II)–Cu(II) complex. Also, the thermal degradation of the CuLH complex unit was observed to exothermic in contrast to the expectations.
- Acar,Atakol,Din?er Kaya,Svoboda,Yaz?c?o?lu,?z
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- Synthesis, structure and magnetic properties of homotrinuclear Ni(II) complexes with asymmetric Schiff-base ligands
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By using 1,3-propanediamine, 2-hydroxyacetophenone and salicylaldehyde an asymmetric ONNO type Schiff base, N(hydroxyphenylidene)-N′(2- hydroxyacetophenylidene)-1,3-propanediamine (H2metsalpn), has been prepared and isolated. This Schiff base has been reduced yielding N(2-hydroxybenzyl)-N′[1-(2-hydroxyphenyl)ethyl]-1,3-diaminopropane (H 2metsalpnH) These two ligands were used in preparing three trinuclear Ni(II) complexes with catena-[Ni3] structural motif, where DMF and carboxylato (formato, acetato, benzoato) ligands occur. These complexes were characterized by EA, IR, TG, DTA and MS data. The X-ray diffraction confirms that the Ni(II) central atoms are in a distorted octahedral coordination environment: the terminal centers possess {NiN2O 4} octahedral coordination sphere whereas the very central atom possesses {NiO6} chromophore. The coordinated DMF groups are liberated between 140-240 °C. The SQUID magnetometry confirms presence of weak exchange coupling of the antiferromagnetic nature, J/hc = -2 to -7 cm -1, with a moderate single-ion anisotropy reflected by the zero-field splitting D/hc = +4 to +7 cm-1.
- ?z, Sevi,Acar, Nurcan,Svoboda, Ingrid,Titi?, Ján,Bo?a, Roman,Atakol, Orhan
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- Syntheses, structural characterization and biological activities of spiro-ansa-spiro-cyclotriphosphazenes
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The replacement reactions of the Cl-atoms in partly substituted spiro-ansa-spiro-cyclotriphosphazenes (7 and 8) with excess pyrrolidine, 4-(2-aminoethyl)morpholine, and 1,4-dioxa-8-azaspiro[4,5]decane in dry THF led to the formation of heterocyclic amine substituted cyclotriphosphazenes (9a-c and 10a-c). All cyclotriphosphazene derivatives were characterized by elemental analysis, FTIR, MS, 1D 1H, 13C and 31P NMR and 2D HSQC, and HMBC techniques, and the crystal structure of partly substituted cyclotriphosphazene 8 was verified by X-ray diffraction analysis. Cyclotriphosphazene derivatives (5-8, 9a-c, and 10a-c) were subjected to antimicrobial activity against seven clinic bacteria and one yeast strain, and the interactions of the phosphazenes with plasmid pBR322 DNA were investigated. Phosphazene derivatives [(5, 7, 8, 9b and 9c) and (10a and 10b)] caused a slight increase and substantial decrease in the mobility of form I DNA, respectively, while 9a caused retardation on gel. Cytotoxic, apoptotic and necrotic effects against L929 fibroblast and A549 lung cancer cells were also evaluated. While the highest toxic effect was obtained for 9a in L929 fibroblast cells and for 9c in A549 lung cancer cells at 100 μg mL-1 concentration, the highest apoptotic effect was determined for 10a in L929 fibroblast cells and for 9a in A549 lung cancer cells at the same concentration. It was found that 9a and 10b exhibited the most necrotic effects against L929 fibroblast and A549 lung cancer cells, respectively. The toxic and necrotic effects of the phosphazenes against A549 lung cancer cells were greater than those against L929 fibroblast cells, whereas, the apoptotic effect of the compounds was greater in L929 fibroblast cells than in A549 lung cancer cells.
- Ba?terzi, Nisan Sevin,Bilge Ko?ak, Selen,Okumu?, Aytu?,Kili?, Zeynel,H?kelek, Tuncer,?elik, ?mer,Türk, Mustafa,Ko?, L. Yasemin,A?ik, Leyla,Aydin, Betül
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- Use of Cu(II)-di-Schiff bases as metalloligands in the formation of complexes with Cu(II), Ni(II) and Zn(II) perchlorate
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One linear homo-metallic trinuclear [{CuL1(CH 3OH)}2Cu(ClO4)2] (1); five trinuclear hetero-metallic; bent [(CuL1)2Ni(H 2O)2](ClO4)2·H2O (2), linear [(CuL1)2Zn(ClO4)2] (3), bent [{CuL2(ClO4)}{CuL2(CH3OH)} Ni(CH3OH)2](ClO4)·(CH 3OH)·0.25(H2O) (4), triangular [(CuL 2){CuL2(CH3CN)}Ni(CH3CN) 2](ClO4)2 (5), triangular [(CuL 2)2Ni(H2O)2](ClO4) 2·3H2O (6) and one rare tetranuclear star-shaped [{CuL2(H2O)}2(CuL2)Zn](ClO 4)2·H2O (7) complexes have been synthesized by reacting the "metalloligand", [CuL1] or [CuL2] with corresponding metal perchlorate where the di-Schiff base ligands H2L1 = N,N′-bis(salicylidene)-1,3- propanediamine and H2L2 = (N,N′-bis(α- methylsalicylidene)-1,3-propanediamine. The structures of all the seven complexes have been determined by X-ray crystallography. Structural analysis shows that complexes 1-6 are discrete trinuclear species where phenoxido groups of two terminal "metalloligands" coordinate to a central Cu(II) in 1 or Ni(II) in 2, 4-6 or Zn(II) in 3. In 1 and 3 two trans axial positions of the central Cu(II) are weakly coordinated by the oxygen atoms of perchlorate anions and the molecules are linear. However, in 2, 4-6 two solvent molecules coordinate to the cis positions of the central Ni(II) to complete its distorted octahedral geometry that makes the molecules bent or triangular. On the other hand, complex 7 is a star-shaped tetranuclear species. In which three metalloligands bind a central Zn(II) ion through double phenoxido bridge.
- Biswas, Saptarshi,Ghosh, Ashutosh
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- Synthesis, characterization, crystal structure, thermal behavior, and biological activity of a new heterotrinuclear complex: [(NiL(NCS)(H2O))2Cd(DMF)2]
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A new trinuclear heterometallic nickel(II)-cadmium(II)-nickel(II) complex, [(NiL(NCS)(H2O))2Cd(DMF)2] (DMF: dimethylformamide) (1), has been synthesized by using NiL as the so-called metallo ligand where H2L = N,N′-bis(salicylidene)-1,3-diaminopropane, cadmium nitrate, and amonium thiocyanate. The title complex was characterized by various methods including elemental analyses, IR, 1H-NMR, 13C-NMR, TG-DTA, and X-ray diffraction techniques. The complex crystallizes in monoclinic space group P21/c, with unit cell dimensions a = 10.6217(3), b = 13.3487(4), c = 16.0043(4) ?, β = 93.823(2)°. The complex was screened for antimicrobial activities by the disc diffusion using DMF as solvent. The minimum inhibitory concentration values were calculated.
- Yardan, Alper,Karahan, Ahmet,Burcu Arslan,Hopa, Cigdem,Gokmen, Mukadderat,Kazak, Canan,Kurtaran, Raif
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- Fluorescent organic nanoparticles (FONs) for selective recognition of Al3+: Application to bio-imaging for bacterial sample
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The development of a novel chemo-sensor for the detection of Al3+ with high sensitivity in aqueous solution is widely considered an important research goal because of the importance of such probes in medicine, living systems and the environment. In this work, we describe a new fluorescent probe, a Schiff's base N,N′-propylenebis(salicylimine) (salpn) as fluorescent organic nanoparticles for Al3+. The study shows that salpn detects Al3+ with the detection limit as low as 1.24 × 10-3 mM, indicating that the chemo-sensor has high sensitivity in aqueous medium, and the fluorescence intensity increases with the increasing Al3+ concentration in the presence of the salpn-ONPs which act as chemo-sensors. The interference of common coexistent metal ions such as Mn2+, Mg2+, Co2+, Fe3+, Ni2+, Zn2+, Sr2+, Ag+, Sm3+, Al3+, Cd2+, Ba2+, Na+ and K+ was tested, showing that salpn-ONPs efficiently detect Al3+ ions with small interference from Cu2+ and Cr3+. Finally, the efficiency of salpn to as a fluorescent probe for Al ion in living systems was evaluated in Gram-negative and Gram positive bacteria, and con-focal laser scanning microscopy confirms its utility that this chemo-sensor efficiently detects Al3+ ion in Staphylococcus aureus enclosed by a single membrane.
- Huerta-Aguilar, Carlos Alberto,Raj, Pushap,Thangarasu, Pandiyan,Singh, Narinder
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- A new linear double phenoxide-bridged trinuclear Cu(II) Schiff base complex: Synthesis, crystallographic elucidation, magneto-structural correlation and DFT Study
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The tetradentate (ONNO) donor Schiff base ligand LH2, derived from the condensation of salicylaldehyde and 1,3-diaminopropane, has been synthesized and reacted with CuBr2 to yield a trinuclear complex with the molecular formula [Cu3L2Br2]. Single crystal X-ray diffraction study reveals that the two terminal copper atoms adopt a square pyramidal geometry, whereas the central copper atom, situated at the inversion centre, is surrounded by four phenoxide oxygen atoms in a square planar fashion. Variable temperature magnetic susceptibility measurement study shows strong antiferromagnetic intra-trimer interactions between the copper centers with a J value of -302 cm-1. EPR study of the complex depicts that, due to the exchange coupling between the copper ions, the EPR spectra were unresolved, having very broad resonances with g = 2.133. A theoretical DFT calculation was also carried out to supplement the experimental results.
- Saha, Sandeepta,Sasmal, Ashok,Roy Choudhury, Chirantan,Gómez-Garcia, Carlos J.,Garribba, Eugenio,Mitra, Samiran
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- H-bond assisted coordination bond formation in the 1D chains based on azido and phenoxido bridged tetranuclear Cu(II) complexes with reduced Schiff base ligands
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Two new 1D chains [(CuL1R)2Cu2(N3)2(μ1,1,3-N3)2]n (1) and [{(CuL2R)2Cu2(N3)2(μ1,1,3-N3)2}·(CH3)2CO]n (2) based on rare μ1,1,3-N3 bridged tetranuclear Cu(II) complexes, have been synthesized using [CuL1R] and [CuL2R] as “metalloligands” [where H2L1R = N,N′-bis(2-hydroxybenzyl)-1,3-propanediamine and H2L2R = N,N′-bis(2-hydroxybenzyl)-1,2-ethylenediamine]. Both complexes have been characterized by elemental analysis, spectroscopic methods, single crystal XRD, and magnetic study. In case of chain 1, the basic building block is a centrosymmetric tetranuclear unit whereas for 2, it is an asymmetric tetranuclear unit containing two types of square pyramidal Cu(II) centers (terminal and central). The μ1,1-N3 bridged central copper atoms of one tetranuclear unit are connected weakly to the axial position of the terminal copper atoms of neibouring units via the azide ions forming a rare μ1,1,3-N3 bridged novel 1D polymeric chain structure. Variable temperature magnetic susceptibility measurements show the presence of an overall strong antiferromagnetic exchange interactions mediated through the double phenoxido bridges with J values of ?123.8 and ?144.6 cm?1 for 1 and 2, respectively.
- Hazari, Alokesh,Diaz, Carmen,Ghosh, Ashutosh
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- Spectrochemical Properties and Solvatochromism of Tetradentate Schiff Base Complex with Nickel: Calculations and Experiments
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The nickel(II) complex with a tetradentate Schiff base ligand obtained by condensation of 1,3-propanediamine with salicylaldehyde (H2salpn) was studied in a variety of solvents at room temperature. The product, that is, the N′,N′′-propylenebis(salicylaldiminato)nickel(II) ([Ni(salpn)]) complex, is brown in color in the solid state. The properties of the ligand and complex were characterized by elemental analysis, solubility in common solvents, molar conductivities, and ultraviolet (UV) and visible (Vis) spectroscopy. The [Ni(salpn)] complex is easily soluble in common solvents such as chloroform, methanol, ethanol, dimethyl formamide, dimethyl sulfoxide, acetonitrile, dioxane, acetone, 2-propanol, and toluene—a necessary condition for observing solvatochromism. The molar conductivity values, equal to 0.0 S mol-1 cm2 in these solvents, point to a typical non-electrolyte behavior for this complex. Spectroscopic measurements were used to confirm the square-planar geometry of the species in solution and to determine the coordination properties of the donor atoms and their bonding abilities (CFM/AOM parameters), as well as trichromaticity coordinate calculations. The results obtained show that the interactions of the metal with the donors depend on the polarity of the solvent.
- Gonciarz, Agnieszka,?uber, Marian,Zwo?dziak, Jerzy
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- Design of end-on cyanato bridged trinuclear Cu(II) Schiff base complex with salen type Schiff base ligand: synthesis, structural investigation and DFT study
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One ONNO-donor tetradentate Schiff base ligand LH2 was derived from the condensation of salicylaldehyde and 1,3-diaminopropane and reacted with Cu(NO3)2·6H2O and NaNCO to yield one trinuclear complex with molecular formula [Cu3L2(μ1,1-NCO)2]. The synthesized complex was characterized by IR, UV–vis spectroscopy, and electrochemical analysis. Single-crystal X-ray diffraction study explores that the two terminal copper atoms adopt square pyramidal geometry, whereas the central copper atom situated at the inversion center is surrounded by four phenoxo oxygens and two end-on cyanato anions to adopt an octahedral geometry. The ONNO-tetradentate Schiff base ligand coordinates with the copper(II) ion via two oxygen atoms of the phenoxo-group and two nitrogen atoms from the imine moiety. A theoretical density functional theory (DFT) calculation was also carried out to supplement the experimental results. All the DFT calculations were done in gas phase.
- Saha, Sandeepta,Choudhury, Chirantan Roy,Pilet, Guillaume,Frontera, Antonio,Mitra, Samiran
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- Structural aspects of a trimetallic CuII derivative: cytotoxicity and anti-proliferative activity on human cancer cell lines
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A trimetallic CuII derivative, [Cu3(L)2(CF3COO)2] (1) (where H2L = N,N′-bis(salicylidene)-1,3-propanediamine), was prepared and characterized. In 1, the two terminal CuII ions are linked to the central CuII by trifluoroacetato and doubly bridging phenoxido. Both the square-pyramidal and octahedral geometries are observed among two different CuII centers in the linear arrangement of the trimetallic unit. Compound 1 is characterized by IR and UV-Vis spectra. Compound 1 has high cytotoxic activity in breast adenocarcinoma (MCF-7), colorectal carcinoma (HCT116) and particularly, in ovarian carcinoma (A2780) cell line compared to a lung adenocarcinoma cell line. The IC50 in A2780 cells is 25 times lower than the respective value for normal human primary fibroblasts demonstrating 1 has higher cytotoxicity towards cancer cells. Additionally, combination of DOX with 1 induces a higher loss of HCT116 cell viability compared with each drug alone.
- Das, Kuheli,Datta, Amitabha,Massera, Chiara,Roma-Rodrigues, Catarina,Barroso, Mariana,Baptista, Pedro V.,Fernandes, Alexandra R.
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- Two new heterodinuclear Schiff base complexes: Synthesis, crystal structure and thermal studies
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Two new heterodinuclear Schiff base complexes, [Hg(L)NiCl2(DMF)2] 1, and [Zn(L)NiCl2(DMF)2]2, where H2L= N,N'-bis(salicylidene)-1,3-diaminopropane and DMF = dimethylformamide have been synthesized and characterized using elemental analysis, IR spectroscopy, thermal analysis and X-ray diffraction. Structural studies on 1 and 2 reveal the presence of a heterodinuclear [NiIIHgII] unit and [ZnIINiII] in which the central metal ions are connected to each other by two phenolate oxygen bridges. For complex 1 the Ni(II) ion adopts an elongated octahedral geometry (NiN2O4) while the Hg(II) ion assumes a distorted tetrahedral arrangement (HgO2Cl2) whereas for complex 2 the Zn(II) ion adopts an elongated octahedral geometry (ZnN2O4) while the Ni(II) ion assumes a distorted tetrahedral arrangement (NiO2Cl2). There are intermolecular CAH.Cl AM interactions among the dinuclear complexes which are interconnected for 1 and 2. These intermolecular interactions result in the formation of a three dimensional structure for 1 and one dimensional zig-zag chains for 2.
- Yardan, Alper,Hopa, Cigdem,Yahsi, Yasemin,Karahan, Ahmet,Kara, Hulya,Kurtaran, Raif
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- Mixed valence trinuclear cobalt (II/III) complexes: Synthesis, structural characterization and phenoxazinone synthase activity
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Three new mixed valence trinuclear Co(II/III) compounds [Co3L2(μ2-C6H5CO2?)2(CH3CN)2](ClO4?)2·(CH3CN)3 (1) [Co3LR2(μ2-C6H5CO2?)2(C6H5CO2?)2]·(CH3CN)2 (2) and [Co3LR2(μ2-C6H5CH[dbnd]CH–CO2?)2(C6H5CH[dbnd]CH–CO2?)2]·((CH3)2CO)2 (3) have been synthesized by reacting the di-Schiff base ligand [H2L] or its reduced analog [H2LR] (where H2L?=?N,N′-bis(salicylidene)-1,3-propanediamine) and (H2LR?=?N,N′-bis(2-hydroxybenzyl)-1,3-propanediamine) with cobalt perchlorate hexahydrate and sodium benzoate or sodium cinnamate. The complexes have been characterized by IR, UV–Vis and single crystal X-ray diffraction analyses. All the complexes are linear trinuclear species [CoIII–CoII–CoIII] in which two terminal octahedral CoIIIN2O2 cores coordinate to the central octahedral CoII ion through μ2-phenoxido oxygen atom and the bridging carboxylato ions. In addition, the complexes (2 and 3) derived from reduced Schiff base ligand have, rather unusually, a terminally coordinated carboxylato ion to CoIII, which is acetonitrile molecule in case of complex (1) with unreduced ligand. Complex 2 has been found to be an excellent functional model for the phenoxazinone synthase activity, in the aerial oxidation of 2-aminophenol to the corresponding 2-aminophenoxazine-3-one chromophore in acetonitrile solvent medium. Detailed kinetic data analysis of this oxidation reaction reveals a fairly high phenoxazinone synthase activity of 2 with kcat?=?153.60?h?1.
- Hazari, Alokesh,Das, Avijit,Mahapatra, Prithwish,Ghosh, Ashutosh
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- Unprecedented structural variations in trinuclear mixed valence Co(ii/iii) complexes: Theoretical studies, pnicogen bonding interactions and catecholase-like activities
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Three new mixed valence trinuclear Co(ii/iii) compounds cis-[Co3L2(MeOH)2(N3)2(μ1,1-N3)2] (1), trans-[Co3L2(H2O)2(N3)2(μ1,1-N3)2]·(H2O)2 (2) and [Co3LR2(N3)3(μ1,3-N3)] (3) have been synthesized by reacting a di-Schiff base ligand (H2L) or its reduced form [H2LR] (where H2L = N,N′-bis(salicylidene)-1,3-propanediamine and H2LR = N,N′-bis(2-hydroxybenzyl)-1,3-propanediamine) with cobalt perchlorate hexahydrate and sodium azide. All three products have been characterized by IR, UV-Vis and EPR spectroscopies, ESI-MS, elemental, powder and single crystal X-ray diffraction analyses. Complex 1 is an angular trinuclear species in which two terminal octahedral Co(iii)N2O4 centers coordinate to the central octahedral cobalt(ii) ion through μ2-phenoxido oxygen and μ1,1-azido nitrogen atoms along with two mutually cis-oxygen atoms of methanol molecules. On the other hand, in linear trinuclear complex 2, in addition to the μ2-phenoxido and μ1,1-azido bridges with terminal octahedral Co(iii) centres, the central Co(ii) is bonded with two mutually trans-oxygen atoms of water molecules. Thus the cis-trans configuration of the central Co(ii) is solvent dependent. In complex 3, the two terminal octahedral Co(iii)N2O4 centers coordinate to the central penta-coordinated Co(ii) ion through double phenoxido bridges along with the nitrogen atom of a terminal azido ligand. In addition, the two terminal Co(iii) are connected through a μ1,3-azido bridge that participates in pnicogen bonding interactions (intermolecular N-N interaction) as an acceptor. Both the cis and trans isomeric forms of 1 and 2 have been optimized using density functional theory (DFT) calculations and it is found that the cis configuration is energetically more favorable than the trans one. However, the trans configuration of 2 is stabilized by the hydrogen bonding network involving a water dimer. The pnicogen bonding interactions have been demonstrated using MEP surfaces and CSD search which support the counter intuitive electron acceptor ability of the μ1,3-azido ligand. Complexes 1-3 exhibit catecholase-like activities in the aerial oxidation of 3,5-di-tert-butylcatechol to the corresponding o-quinone. Kinetic data analyses of this oxidation reaction in acetonitrile reveal that the catecholase-like activity follows the order: 1 (kcat = 142 h-1) > 3 (kcat = 99 h-1) > 2 (kcat = 85 h-1). Mechanistic investigations of the catalytic behaviors by X-band EPR spectroscopy and estimation of hydrogen peroxide formation indicate that the oxidation reaction proceeds through the reduction of Co(iii) to Co(ii). This journal is
- Hazari, Alokesh,Kanta Das, Lakshmi,Kadam, Ramakant M.,Bauz, Antonio,Frontera, Antonio,Ghosh, Ashutosh
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- Syntheses, spectral and chiral properties and DNA interactions of multi-heterocyclic di- And trinuclear boron complexes
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Tetrahedrally coordinated multi-heterocyclic boron complexes are stable, but much less investigated inorganic ring systems. In the present study, a series of dinuclear (2aI-2cI and 2aII-2cII) and trinuclear (3aI-3cI and 3aII-3cII) boron complexes were synthesized from SalenH2 type symmetrical bulky ligands [HOArCHN-R-NCHArOH; R = (CH2)n, n = 2 (1a), 3 (1b) and 4 (1c)], arylboronic acids (phenylboronic acid and 4-formylphenylboronic acid), and boric acid for the investigation of their spectral, stereogenic and DNA cleavage activities. The Salen-boron complexes have two equivalent chiral B-centers, giving rise to diastereoisomers. The stereogenic properties of these complexes were investigated by nuclear magnetic resonance (NMR) and circular dichroism (CD) spectroscopies. The stereoisomers were compared with each other for two different architectural types and a total of 12 Salen-boron complexes with seven- to nine-membered [(B-O-B)-(N-R-N)] heterocycles. The combination of NMR and CD spectra of the complexes shows that the boron complexes (2bI and 3bII) and (2bII and 3bI) from the (CH2)3 precursor give only a cis-meso (RS/SR) isomer and only one trans-enantiomer (RR or SS), respectively. The complexes (2cI, 3cI and 3cII) from the (CH2)4 precursor give only one enantiomer (RR or SS), whereas the boron complexes (2aI, 2aII, 3aI and 3aII) from the (CH2)2 precursor and (2cII) from the (CH2)4 precursor form two diastereoisomers as one enantiomer (RR or SS) and one meso (RS/SR). Furthermore, the DNA cleavage activities of the adducts were determined using agarose gel electrophoresis and UV absorption in order to compare the cleavage efficiency of the boron complexes depending on the type of complexes (dinuclear or trinuclear) and the number of members in the heterocyclic frameworks. In this assay, the seven-membered trinuclear boron complex (3bII) showed the highest cleavage efficiency. This journal is
- Bilge Ko?ak, Selen,Kaya, ?zgecan,Kili?, Zeynel,Coban, Burak,Yildiz, Ufuk,?o?ut, Bünyemin
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- Influence of the central metal ion in controlling the self-assembly and magnetic properties of 2D coordination polymers derived from [(NiL)2M]2+ nodes (M = Ni, Zn and Cd) (H2L = salen-type di-Schiff base) and dicyanamide spacers
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Three new 2D coordination polymers (CPs) 2∞[(NiL)2Ni(μ1,5-N(CN)2)2]n (1), 2∞[(NiL)2Cd(μ1,5-N(CN)2)2]n (2) and 2∞[(NiL)2Zn(μ1,5-N(CN)2)2]n (3) have been synthesized by reacting a [NiL] "metalloligand" (where H2L = N,N′-bis(salicylidene)-1,3-propanediamine) with three different metal(ii) (Ni, Cd and Zn) perchlorates and sodium dicyanamide, with identical molar ratios of the reactants. All three products have been characterized by IR and UV-Vis spectroscopies, elemental analyses, powder and single crystal X-ray diffraction and variable temperature magnetic measurements. The isomorphous compounds 1 and 2 consist of similar [(NiL)2M(μ1,5-N(CN)2)] (M = Ni for 1 and Cd for 2) angular trinuclear units in which two terminal "metalloligands" [NiL] coordinate to the central nickel(ii) (in 1) or cadmium(ii) (in 2) ion through phenoxido oxygen atoms. The μ1,5-bridging dicyanamido spacers connect the central Ni(ii) or Cd(ii) of one node to terminal Ni(ii) of two different nodes giving rise to 2D CPs. Compound 3 also contains trinuclear units with the same formula as those of 1 and 2: [(NiL)2M(μ1,5-N(CN)2)] (M = Zn in 3). The main differences are that these units are linear in 3 and the dicyanamide spacers link only the nickel atoms of neighbouring nodes. As in 1 and 2, these trinuclear units are connected to four other units via four μ1,5-bridging dicyanamido ligands, giving rise to 2D CP with a similar topology: a uninodal 4-connected underlying net with the sql (Shubnikov tetragonal plane net) topology and (44·62) point symbol. The magnetic properties show the presence of moderate intra-trimer antiferromagnetic interactions in 1 (J = -12.9 cm-1) and weak antiferromagnetic interactions between the terminal Ni(ii) ions in 2 (J = -2.4 cm-1). In 3 the Ni(ii) ions are well isolated by the central Zn(ii) ion and accordingly, only a very weak antiferromagnetic interaction through the single μ1,5-bridging dicyanamido ligands is observed (J = -0.44 cm-1, D = -3.9 cm-1). This journal is
- Das, Lakshmi Kanta,Gómez-García, Carlos J.,Ghosh, Ashutosh
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- Influences of polarizability effect of alkyl group and homoring competition effect of substituents on the NMR spectra of salen-type Schiff base
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Salen-type Schiff bases are a kind of important compounds and are widely used. In order to explore the effect of alkyl groups and substituents attached to aromatic ring on the chemical shifts, 63 title compounds were synthesized. Their 1H NMR and 13C NMR spectra were obtained; and the effects of the alkyl chain length and substituents on the chemical shifts (δH(CH=N), δC(CH=N), δH(OH), and δC(C-OH)) were studied. The results show that (1) the alkyl polarizability effect index (PEI) has an important influence on the chemical shifts of the above four atoms, with the increase of PEI, the values of δH(CH=N) and δc(CH=N) decrease, and the values of δH(OH) and δC(C-OH) increase. (2) The influence of substituent X attached to aromatic ring on the chemical shift is related to its position by taking OH or CH=N as reference. As for the effect of substituent on the chemical shifts, the effect of Hammett constant σ(X)-OH and excited-state substituent parameter (Formula presented.) with OH as reference are different from that ofσ(X)-CH=N and (Formula presented.) with CH=N as reference, and there is a “homoring competition effect” of the substituent. (3) The effect of the cross-interaction between X and OH on the chemical shift is also significantly different due to the different position of X. Quantitative correlation equations against chemical shifts were built for the four atoms, and the stability and prediction ability of the obtained equations were confirmed by leave-one-out cross validation.
- Wei, Bai-ying,Cao, Chen-zhong,Cao, Chao-tun
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p. 701 - 712
(2021/02/12)
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- Iridium(I) homobinuclear complexes containing salen-type ligands as bridge
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New binuclear iridium(I) complexes with general formula [Ir2(η4-cod)2(μ-SB)] (1–12) derived from the reactions of tetradentate Schiff bases ligands [N,N′-ethylenebis(5-R-salicylideneimine)] (5,5′-R-salenH2), [N,N′-1,3-propylenebis(5-R-salicylideneimine)] (5,5′-R-salpenH2), and [N,N′-o-phenylenebis(5-R-salicylideneimine)] (5,5′-R-salphenH2) (R = H, MeO, Cl, NO2) with [Ir(cod)(μ-Cl)]2 were synthesized. The homobinuclear nature of this iridium complexes was supported by elemental analysis, FAB-Mass and 1H NMR spectrometry. Full characterization was accomplished by IR spectroscopy, 13C NMR and bidimensional NMR experiments (COSY, HSQC, HMBC and NOESY). In addition, iridium complex [(Ir(η4-cod)2(μ-5,5′-MeO-salen)] (2) was characterized by X-ray crystallography, showing that ethylene bridge is a s-trans conformation, and that the Schiff base ligand act as a bridging N,O-bidentate ligand toward two iridium atoms, and 1,5-cyclooctadiene (cod) ligand complete the coordination sphere of metal center. The effect of the substituent groups on salicylaldiminate fragments has been studied by 13C{1H} NMR shift and Hammett sigma correlations for each series of complexes.
- Alvarado-Monzón, José C.,López, Jorge A.,de Riquer, Gabriel A. Andreu,Cristobal, Crispin,Flores-Alamo, Marcos,Ruiz-Azuara, Lena
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p. 243 - 250
(2019/02/01)
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- Fe3O4@SiO2@Im[Cl]Mn(III)-complex as a highly efficient magnetically recoverable nanocatalyst for selective oxidation of alcohol to imine and oxime
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An efficient and environmentally friendly oxidation process for the one-pot preparation of oxime, imine and carbonyl compounds through alcohol oxidation in the presence of H2O2 and/or O2 have been developed by a melamine-Mn(III) Schiff base complex supported on Fe3O4@SiO2–Cl nanoparticles, named as Fe3O4@SiO2@Im[Cl]Mn(III)-complex nanocomposite, at room temperature. Direct oxidation of alcohol to carboxylic acid was performed using the catalyst in the presence of molecular O2 at room temperature in a different approach. The oxidation products were obtained with excellent yields and high TOFs. The properties of the catalyst were characterized by Fourier transform infrared spectroscopy (FTIR), elemental analysis (C, H, N), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), dynamic light scattering (DLS), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), inductive coupled plasma (ICP), cyclic voltammetry (CV), nuclear magnetic resonance (1H & 13C NMR), vibration sample magnetometer (VSM), Brunauer– Emmett–Teller (BET) and differential pulse voltammetry (DPV) analyses. The mechanism of the oxidation processes was investigated for the both H2O2 and O2 oxidants. The role of the imidazolium moiety in the catalyst as a secondary functionality was investigated. Chemoselectivity behavior of the catalyst was studied by some combinations. The catalyst could be recycled from the reaction mixture by a simple external magnet and reused for several times without any considerable reactivity loss.
- Kazemnejadi, Milad,Alavi, Seyyedeh Ameneh,Rezazadeh, Zinat,Nasseri, Mohammad Ali,Allahresani, Ali,Esmaeilpour, Mohsen
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p. 230 - 249
(2019/03/28)
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- Synthesis, structure and catalytic alcohol oxidation by ruthenium(III) supported by Schiff base and triphenylphosphine ligands
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Treatment of [RuCl2(PPh3)3] with two equiv. bi-dentate Schiff base N,O-LH-Cl (N,O-LH-Cl = 2[(3-chloro-phenylimino)-methyl]-phenol) or N,O-LH-NO2 (N,O-LH-NO2 = 2[(4-nitro-phenylimino)-methyl]-phenol) in the presence of triethylamine afforded cis-[RuCl(PPh3)(κ2-N,O-L-Cl)2] (1) and trans-[RuCl(PPh3)(κ2-N,O-L-NO2)2]·Et2O (2), respectively. Reactions of [RuCl2(PPh3)3] and equal equiv. tetra-dentate Schiff bases gave corresponding ruthenium(III) complexes [RuCl(PPh3)(salen)] (3) (H2salen = N,N′-disalicylidene-1,2-ethanediamine), [RuCl(PPh3)(salipn)]·2CH2Cl2 (4) (H2salipn = N,N′-disalicylidene-1,2-(1-methyl)ethanediamine), [RuCl(PPh3)(salpn)]·CH2Cl2 (5) (H2salpn = N,N′-disalicylidene-1,2-propanediamine), [RuCl(PPh3)(salphen)]·CH2Cl2 (6) (H2salphen = N,N′-disalicylidene-1,2-phenyldiamine), [RuCl(PPh3)(saltoln)]·CH2Cl2 (7) (H2saltoln = N,N′-disalicylidene-1,2-tolyldiamine) and [RuCl(PPh3)(salcyn)] (8) (H2salcyn = N,N′-disalicylidene-(R,R)-1,2-cyclohexanediamine). The molecular structures of complexes 1–5 and 7 have been determined by single-crystal X-ray crystallography. The catalytic oxidation properties of ruthenium(III) complexes 1–8 were tested towards alcohols in the presence of N-methylmorpholine-N-oxide.
- Tang, Li-Hua,Wu, Fule,Lin, Hui,Jia, Ai-Quan,Zhang, Qian-Feng
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p. 212 - 218
(2018/04/02)
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- Schiff base manganese compound, preparation method thereof and application thereof
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The present invention provides a Schiff base manganese compound, a preparation method thereof and an application thereof. The Schiff base manganese compound has a structure of a formula I. The provided Schiff base manganese compound has a NNOO tridentate coordination ability to form a metal active center binding site to obtain a tetracoordinate Schiff base manganese catalyst. The Schiff base manganese compound is used to catalyze a ring-opening polymerization of lactide and caprolactone; the Schiff base manganese catalyst has very high activity for the ring-opening polymerization of the lactide and caprolactone, can also realize the polymerization of the monomers at room temperature, at the same time has a certain selectivity to the racemic lactide and can slightly improve the regularity of the microscopic chain structure of the polymerization product. Under the action of the catalyst, a monomer conversion rate of polylactic acid can reach 89-96%; the stereoregularity Pm of the obtained polylactic acid can reach 0.43-0.60; and a monomer conversion rate of polycaprolactone can reach 90%-95%.
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Paragraph 0082; 0083
(2019/01/07)
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- Schiff base iron compound as well as preparation method and application thereof as catalyst
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The invention provides a schiff base iron compound as well as a preparation method and application thereof as a catalyst. The schiff base iron compound provided by the invention is of a structure of formula (I) as shown in the specification, in the formula (I), Y is -CH2-CH2-CH2 or R is -H or alkyl. The schiff base iron compound provided by the invention has the capability of NNOO quadridentation, then a metal activity center binding site is formed, and a quadridentation schiff base iron catalyst is prepared. The schiff base iron compound is used for catalyzing ring opening polymerization of lactide and caprolactone, very high catalysis activity is achieved, meanwhile very high racemize lactide selectivity is achieved, and the regulation of a microcosmic chain structure of a polymerization product is improved. Tests show that the monomer conversion rate of polylactic acid prepared by using the method provided by the invention can be up to 90%, and the monomer conversion rate of polycaprolactone is up to 99%. When the lactide is racemize lactide, the three-dimensional regularity (Pm) of obtained polylactic acid is up to 0.60.
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Paragraph 0096-0098
(2017/12/28)
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- Direct preparation of oximes and Schiff bases by oxidation of primary benzylic or allylic alcohols in the presence of primary amines using Mn(III) complex of polysalicylaldehyde as an efficient and selective heterogeneous catalyst by molecular oxygen
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The present work introduced the new strategy for direct preparation of Schiff base as well as oxime compounds through oxidation of primary benzylic or allylic alcohols in the presence of amines by complexation of Mn(III) to a polymeric Schiff base ligand based on polysalicylaldehyde (PSA-Schiff base-Mn(III) complex). As a new environmentally benign protocol, manganese heterogeneous polymeric catalytic system demonstrated promising oxidation of alcohols in ethanol using molecular oxygen. PSA was synthesized through polycondensation reaction of 2-hydroxy-5-chloromethyl-benzaldehyde and then treated with 2-aminophenol to form polymeric ligand. Average molecular weight of PSA was studied by an analytical method as well as GPC analysis. Formation of the catalyst was characterized step by step by FTIR, UV–Vis, 1H NMR, TGA, CHN and EDX analyses. Loading amounts of metal ions as well as leaching amount of the catalysis were studied by ICP-OES instrument. The catalyst shows up to high yields for oxidation of primary and secondary primary benzylic or allylic alcohols to carbonyl compounds, especially direct imine formation in a mild, inexpensive and efficient method which can be successfully recovered from the reaction mixture and reused for several times without any remarkable reactivity loss. Effect of solvent, temperature, catalyst amount and oxygen donors along with some blank experiments to elucidation of catalyst activity was evaluated in this work. Also chemoselectivity behavior of the catalyst was investigated with some combinations.
- Kazemnejadi, Milad,Shakeri, Alireza,Mohammadi, Mohammad,Tabefam, Marzieh
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p. 1917 - 1933
(2017/08/15)
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- A rare doubly nitrato and phenoxido bridged trimetallic CuII complex: EPR, antiferromagnetic coupling and theoretical rationalization
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A rare trimetallic CuII complex, [Cu3(L)2(NO3)2] (1) has been afforded incorporating a [CuL] metalloligand, [where H2L = N,N′-bis(salicylidene)-1,3-propanediamine]. In 1, in addition to the double phenoxido bridge, the two terminal CuII atoms are linked to the central CuII by means of syn-anti bridging nitrate anions giving rise to a linear arrangement. Complex 1 exhibits strong antiferromagnetic coupling and shows an χMT value of 0.703 cm3 mol-1 K at 300 K. DFT computational studies reveal that there is a clear magneto-structural correlation between the Cu-O-Cu angle and the JCu-Cu values, which is in accordance with the experimental evidence. The biological effect of 1 on the viability of different human carcinoma cells was evaluated using MTT assay and the results indicate that this complex induces a decrease in cell-population growth of human colorectal carcinoma cells (COLO 205) with apoptosis.
- Datta, Amitabha,Das, Kuheli,Mane, Sandeep B.,Mendiratta, Shruti,El Fallah, Mohamed Salah,Garribba, Eugenio,Bauzá, Antonio,Frontera, Antonio,Hung, Chen-Hsiung,Sinha, Chittaranjan
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p. 54856 - 54865
(2016/07/06)
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- NOVEL METAL SALEN COMPLEX COMPOUND
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PROBLEM TO BE SOLVED: To provide a novel metal salen complex compound which is a self magnetic organic compound allowing for drug delivery. SOLUTION: This invention relates to a metal salen complex compound represented by the formula or a derivative thereof. The metal salen complex compound exhibits concentration-dependent antitumor effect on a human malignant mesothelioma cell (Meso1) and a rabbit tongue cancer cell (VX2). COPYRIGHT: (C)2015,JPOandINPIT
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Paragraph 0035; 0036
(2018/02/27)
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- Schiff base ligands and their transition metal complexes in the mixtures of ionic liquid + organic solvent: A thermodynamic study
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Schiff bases and their metal complexes in the mixtures of ionic liquid (IL) + organic solvent have shown great potential in attractive oxidation catalytic processes. The efficiency of such a process is strongly dependent on the various molecular interactions occurring between components. Thermodynamic properties of these systems can provide valuable information about structural interactions. Therefore, in this work, the interactions of the IL 1-hexyl-3-methylimidazolium chloride ([HMIm]Cl) with Schiff bases in organic solvents were studied through the measurements of density, viscosity, and electrical conductivity. The effect of solvent on the interactions was examined by the solutions of IL + BPIC Schiff base + solvent (C2H6O-C3H8O-C4H10O). Moreover, the influence of Schiff base ligand and Schiff base complex structures was probed by the solutions of IL + DMA + ligand (salcn/salpr/salen) and IL + DMA + complex (VO(3-OMe-salen)/VO(salophen)/VO(salen)), respectively. Using the experimental data, some important thermodynamic properties, such as standard partial molar volume (Vf,IL0), experimental slope (Sv), viscosity B-coefficient, solvation number (B/Vf,IL0), and limiting molar conductivity (Λ0) were calculated and discussed in terms of solute-solvent (IL-DMF/alcohol) and solute-cosolute (IL-Schiff base) interactions.
- Shekaari, Hemayat,Kazempour, Amir,Khoshalhan, Maryam
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p. 2179 - 2191
(2015/02/19)
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- Trinuclear heterometallic CuII-MnII complexes of a salen type Schiff base ligand: Anion dependent variation of phenoxido bridging angles and magnetic coupling
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Five new trinuclear heterometallic CuII-MnII complexes [(CuL)2Mn(O2CPh)2] (1), [(CuL) 2Mn(N3)2] (2), [(CuL)2Mn(NCO) 2] (3), [(CuL)2Mn(NO3)2] (4) and [(CuL)2Mn(Sal)2]·CH2Cl2 (5) have been synthesized with the di-Schiff base ligand H2L (where H2L = N,N′-bis(salicylidene)-1,3-propanediamine and Sal = salicylate). These complexes with different anionic co-ligands have been synthesized to attain a large variation in phenoxido bridging angles and to investigate its consequence on magnetic properties. Single crystal X-ray diffraction analyses reveal that complexes 1, 2, 4 and 5 are linear, whereas 3 has an angular geometry. Variable temperature magnetic susceptibility measurements suggest that all five complexes possess an overall antiferromagnetic interaction between CuII and MnII ions, which results in a final ferrimagnetic ground state with spin 3/2 in the Cu II-MnII-CuII trinuclear structure. The weakest antiferromagnetic interaction (JCu-Mn = -7.0 cm-1) is observed for 2 having the lowest value of the Cu-O-Mn angle (92.0°), while the strongest antiferromagnetic interaction (JCu-Mn = -26.5 cm -1) is observed for 3 having the largest Cu-O-Mn angle (101.4°). Complexes 1, 4 and 5 show average Cu-O-Mn angles of 98.2°, 97.6°and 97.7°, respectively, that lead to intermediate antiferromagnetic interactions (JCu-Mn = -9.6, -9.7, -9.3 cm-1 respectively). The Royal Society of Chemistry 2014.
- Seth, Piya,Ghosh, Soumavo,Figuerola, Albert,Ghosh, Asutosh
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p. 990 - 998
(2014/01/06)
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- The impact of anion-modulated structural variations on the magnetic coupling in trinuclear heterometallic CuII-CoII complexes derived from a salen-type Schiff base ligand
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Three new trinuclear heterometallic [(CuIIL)2CoIIX2] complexes [H2L = N,N′-bis(salicylidene)-1,3-propanediamine and X = thiocyanate (1), benzoate (2), or azide (3)] have been synthesized by reacting the metalloligand [CuL] with Co(ClO4)2·6H2O and the NH4+ or Na+ salt of the corresponding anion in methanol. Structural characterization reveals that the central CoII ion is connected to two terminal metalloligands through μ1,1-diphenoxido bridges in all three complexes. However, two monodentate thiocyanato ions, which are mutually cis coordinated to the Co atom in 1, generate a "bent" structure, whereas the trans-coordinated syn-syn bridging benzoato (1κO:2κO′) and the end-on bridging azido (μ1,1) coligands in 2 and 3, respectively, produce linear structures. The changes in the number and nature of the bridges with a shortening of the distances between the metal centers leads to a concomitant decrease of the average CuII-O-CoII bridging angle from 99.3(2) to 97.1(4) and 91.5(1)° for 1, 2 and 3, respectively. Variable-temperature magnetic susceptibility measurements show the presence of a dominant antiferromagnetic coupling between the Cu-Co pairs in all three complexes. However, a steady decrease of the magnitude of the exchange coupling constant (JCu-Co) is observed from -33.4 (for 1) to -11.4 (for 2) and -2.15 cm-1 (for 3). This trend suggests that larger Cu-O-Co angles are associated with stronger antiferromagnetic coupling. Anion-mediated geometrical variations generate three heterometallic complexes with distinct trinuclear Cu2Co cores as a result of different diphenoxido bridging angles between the CuII and CoII ions. Magnetic studies reveal decreased antiferromagnetic exchange interactions associated with a decrease of this bridging angle.
- Ghosh, Soumavo,Aromí, Guillem,Gamez, Patrick,Ghosh, Ashutosh
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p. 3341 - 3349
(2015/04/27)
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- Effect of hydroxyl group position on adsorption behavior and corrosion inhibition of hydroxybenzaldehyde Schiff bases: Electrochemical and quantum calculations
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The corrosion inhibition and adsorption of N,N′-bis(n- hydroxybenzaldehyde)-1,3-propandiimine (n-HBP) Schiff bases has been investigated on steel electrode in 1 M HCl by using electrochemical techniques. The experimental results suggest that the highest inhibition efficiency was obtained for 3-HBP. Polarization curves reveal that all studied inhibitors are mixed type. Density functional theory (DFT) at the B3LYP/6-31G(d,p) and B3LYP/3-21G basis set levels and ab initio calculations using HF/6-31G(d,p) and HF/3-21G methods were performed on three Schiff bases. By studying the effects of hydroxyl groups in ortho-, meta-, para- positions, the best one as inhibitor was found to be meta-position of OH in Schiff base (i.e., 3-HBP). The order of inhibition efficiency obtained was corresponded with the order of most of the calculated quantum chemical parameters. Quantitative structure activity relationship (QSAR) approach has been used and a correlation of the composite index of some of the quantum chemical parameters was performed to characterize the inhibition performance of the Schiff bases studied. The results showed that %IE of the Schiff bases was closely related to some of the quantum chemical parameters but with varying degrees/order. The calculated %IE of the Schiff base studied was found to be close to their experimental corrosion inhibition efficiencies.
- Danaee,Ghasemi,Rashed,Rashvand Avei,Maddahy
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p. 247 - 259
(2013/04/24)
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- Synthesis, X-ray crystallography, thermal studies, spectroscopic and electrochemistry investigations of uranyl Schiff base complexes
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Some tetradentate salen type Schiff bases and their uranyl complexes were synthesized and characterized by UV-Vis, NMR, IR, TG, C.H.N. and X-ray crystallographic studies. From these investigations it is confirmed that a solvent molecule occupied the fifth position of the equatorial plane of the distorted pentagonal bipyramidal structure. Also, the kinetics of complex decomposition by using thermo gravimetric methods (TG) was studied. The thermal decomposition reactions are first order for the studied complexes. To examine the properties of uranyl complexes according to the substitutional groups, we have carried out the electrochemical studies. The electrochemical reactions of uranyl Schiff base complexes in acetonitrile were reversible.
- Asadi, Zahra,Shorkaei, Mohammad Ranjkesh
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p. 344 - 351
(2013/04/10)
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- Use of metalloligands [CuL] (H2L = Salen type di-Schiff bases) in the formation of heterobimetallic copper(II)-uranyl complexes: Photophysical investigations, structural variations, and theoretical calculations
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Five heterobimetallic copper(II)-uranium(VI) complexes [(CuL 1)UO2(NO3)2] (1), [{CuL 1(CH3CN)}UO2(NO3)2] (2), [{CuL1(CH3COCH3)}UO2(NO 3)2] (3), [{CuL2(CH3CN)}UO 2(NO3)2](4), and [{CuL2(CH 3COCH3)}UO2(NO3)2] [{CuL2}UO2(NO3)2] (5) have been synthesized by reacting the Cu(II)-derived metalloligands [CuL1] and [CuL2] (where, H2L1 = N,N′-bis(α- methylsalicylidene)-1,3-propanediamine and H2L2 = N,N′-bis(salicylidene)-1,3-propanediamine) with UO2(NO 3)2·6H2O in 1:1 ratio by varying the reaction temperature and solvents. Absorption and fluorescence quenching experiments (steady-state and time-resolved) indicate the formation of 1:1 ground-state charge transfer copper(II)-uranium(VI) complexes in solution. X-ray single-crystal structure reveals that each complex contains diphenoxido bridged Cu(II)-U(VI) dinuclear core with two chelated nitrato coligands. The complexes are solvated (acetonitrile or acetone) in the axial position of the Cu(II) in different manner or desolvated. The supramolecular interactions that depend upon the co-ordinating metalloligands seem to control the solvation. In complexes 2 and 3 a rare NO3-···NO 3- weak interaction plays an important role in forming supramolecular network whereas an uncommon U=O···NO 3- weak interaction helps to self-assemble heterobinuclear units in complex 5. The significance of the noncovalent interactions in terms of energies and geometries has been analyzed using theoretical calculations.
- Ghosh, Soumavo,Biswas, Saptarshi,Bauza, Antonio,Barcelo-Oliver, Miquel,Frontera, Antonio,Ghosh, Ashutosh
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p. 7508 - 7523
(2013/07/26)
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