cas 1761-56-4, 2-SALICYLIDENEAMINOPHENOL | Articles data

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Synthesis, structure, and magnetic properties of a tetradecanuclear manganese complex
A new [Mn14(μ4-O)4(μ3-OH) 4(L)4(O2CPh)14(OMe) 2]·2CH2Cl2 (1·2CH 2Cl2) cluster, where H2L = N-salicylidene-o- aminophenol, was synthesized by reacting the [Mn6O2(O 2CPh)10(DMF)4] precursor with tridentate ligands. The structure of the tetradecanuclear complex features a [Mn II6MnIII8(μ4-O) 4(μ3-OH)4]24+ core which is comprised of a non-planar rod-like [MnII2Mn III6(μ4-O)4(μ3-OH) 2]12+ unit, with both sides bonded in the form of a [MnII2MnIII(μ3-OH)]6+ triangle. Direct current (dc) magnetic susceptibility measurements of the complex indicate the existence of intramolecular antiferromagnetic interactions between the metal ions, with a ground state of S = 2. The complex exhibits frequency-dependent out-of-phase signals in alternating current (ac) magnetic susceptibility measurements, suggesting slow magnetic relaxations.
Huang, Siang-Hua,Jhan, Siang-Yu,Yang, Chen-I,Tsai, Hui-Lien
p. 245 - 251
(2013)
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Heterometallic octanuclear REIII3NiII 5 (RE = DyIII, GdIII and YIII) clusters with slow magnetic relaxation for the dysprosium derivative
Reactions of rare earth benzoate and nickel perchlorate with a Schiff-base ligand, 2-([(2-hydroxyphenyl)imino]methyl) phenol (H2L), in the presence of triethylamine yielded three heterobimetallic octanuclear clusters of general formula [RE3Ni5L5(PhCOO) 3(μ3-OH)5(μ3-OCH 3)(CH3OH)4(H2O)]·xCH 3OH·yH2O (RE = DyIII, x = 4, y = 4 (1), RE = GdIII, x = 5, y = 4 (2), RE = YIII, x = 5, y = 3 (3)). Single-crystal X-ray diffraction reveals that the metal core of each cluster consists of two distorted [RE2Ni2O4] cubane-like moieties and a heterobimetallic triangular [RE2NiO 2] unit, with RE ions arranged in a typical triangular fashion. Variable-temperature solid state magnetic susceptibilities of these complexes were measured in the temperature range 2-300 K and the results indicate that an overall ferromagnetic interaction among the metal ions is operative for compounds 2 and 3. Under zero external field, the Dy3Ni5 compound shows a frequency dependence of the out-of-phase (χ′′) signals, which indicates slow relaxation of the magnetization.
Wang, Huiyu,Ke, Hongshan,Lin, Shuang-Yan,Guo, Yang,Zhao, Lang,Tang, Jinkui,Li, Yun-Hui
p. 5298 - 5303
(2013)
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DNA binding and cytotoxicity of two Cu(II) complexes containing a Schiff base ligand along with 1,10-phenanthroline or imidazole as a coligand
We report the synthesis, characterization and biological activities of the compounds [CuL(o-phen)] (1) and [CuL(Imz)] (2), (H2L = o-HOC6H4C(H)=NC6H4OH-o, o-phen = 1,10-phenanthroline, and Imz = imidazole). Both the compounds 1 and 2 have been characterized by X-ray crystallography. A four-line EPR pattern originating from the interaction of the unpaired electron with the central 63/65Cu nucleus (I = 3/2) with Aiso values of 7.3 and 8.5 mT, respectively for 1 and 2 in DMF at RT suggests their monomeric nature in solution. These compounds undergo irreversible oxidation–reduction. Biological studies show intercalative DNA binding and remarkable cell cytotoxicity as well as anticancer activity. IC50 values of 1 and 2 for the human lung cancer A549 cell line (0.67 and 0.59 μM, respectively) and for the breast cancer MCF7 cell line (6.30 and 8.88 μM, respectively) are found to be very promising. Compounds 1 and 2 appear to be more potent for the human lung cancer A549 cell line than some anticancer drugs tested for this cell line. Most importantly, 1 and 2 are found to be remarkably less toxic for the human lung embryonic normal cell line L132 as evident from the cell viabilities in presence of these two compounds.
Koley, Manjuri K.,Parsekar, Sidhali Uday,Duraipandy, Natarajan,Kiran, Manikantan Syamala,Varghese, Babu,Manoharan, Periakaruppan T.,Koley, Aditya P.
p. 211 - 221
(2018)
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Salicylimine-based fluorescent chemosensor for aluminum ions and application to bioimaging
In this study, an assay to quantify the presence of aluminum ions using a salicylimine-based receptor was developed utilizing turn-on fluorescence enhancement. Upon treatment with aluminum ions, the fluorescence of the sensor was enhanced at 510 nm due to formation of a 1:1 complex between the chemosensor and the aluminum ions at room temperature. As the concentration of Al 3+ was increased, the fluorescence gradually increased. Other metal ions, such as Na+, Ag+, K+, Ca2+, Mg2+, Hg2+, Mn2+, Co2+, Ni 2+, Cu2+, Zn2+, Cd2+, Pb 2+, Cr3+, Fe3+, and In3+, had no such significant effect on the fluorescence. In addition, we show that the probe could be used to map intracellular Al3+ distribution in live cells by confocal microscopy.
Kim, Soojin,Noh, Jin Young,Kim, Ka Young,Kim, Jin Hoon,Kang, Hee Kyung,Nam, Seong-Won,Kim, So Hyun,Park, Sungsu,Kim, Cheal,Kim, Jinheung
p. 3597 - 3602
(2012)
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N-(2-Hydroxyphenyl)salicylaldimine
The title compound, 2-(salicylideneaminophenol, C13H11NO2, a potential tridentate ligand, has two crystallographically independent molecules in the asymmetric unit, one of which is disordered.Intramolecular hydrogen bonds occur between the pairs of atoms O(16) and N(8) , and O(1) and O(16) , the H atoms essentially being bonded to the O atoms.
Elerman, Yalcin,Elmali, Ayhan,Atakol, Orhan,Svoboda, Ingrid
p. 2344 - 2346
(1995)
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Oxo-bridged bis oxo-vanadium(V) complexes with tridentate Schiff base ligands (VOL)2O (L = SAE, SAMP, SAP): Synthesis, structure and epoxidation catalysis under solvent-free conditions
The dinuclear V(V) complexes (VOL)2O (L = SAE (1), SAMP (2), SAP (3)) have been synthesized from VO(acac)2 and the corresponding tridentate ligands LH2 in methanol under reflux conditions and subsequent air oxidation in organic solvent. They have been characterized by IR and NMR spectroscopy, by thermogravimetric analysis, and by single crystal X-ray diffraction for 1 and 2. DFT calculations were carried out for a better understanding of the vibrational pattern, principally the V-O related vibrations. Complex [VO(SAP)]2O (3) catalyzes the epoxidation of cyclooctene by TBHP in water in the absence of any added solvent with good selectivity.
Cordelle, Cindy,Agustin, Dominique,Daran, Jean-Claude,Poli, Rinaldo
p. 144 - 149
(2010)
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Degradation of organic pollutants in waters by a water-insoluble iron(III) Schiff base complex
To degrade organic pollutants in water with hydrogen peroxide (H2O2) under visible light (λ ≥ 420 nm), a novel water-insoluble iron Schiff base complex, iron(III)-bis-salicylaldehyde-o-aminophenol (Fe-SAP), was prepared and characterized using NMR, MS, IR, and UV-Vis spectroscopy. Rhodamine B (RhB) and salicylic acid were used as probes to characterize the photocatalytic system. High catalytic activity of Fe-SAP was observed over a wide range of pH values from 3 to 9. Scavenging studies of reactive oxygen species (ROS) and ESR experiments indicate that the primary ROS from photocatalytic conversion of H2O2 is 1O2, rather than .OH. To date, there have been few reports on the generation of 1O2 by iron organic complexes for the oxidative decomposition of organics. The catalyst stability and reusability are good, most likely because the water-insoluble Fe-SAP is able to reduce the damage to its organic ligands by .OH. Given these favorable characteristics, Fe-SAP exhibits excellent potential for practical application in removing refractory organic pollutants and pollutants of emerging concern from water and wastewater.
Song, Quan,Ma, Wan-Hong,Jia, Man-Ke,Johnson, David,Huang, Ying-Ping
p. 70 - 76
(2015)
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Tridentate ONS vs. ONO salicylideneamino(thio)phenolato [MoO2L] complexes for catalytic solvent-free epoxidation with aqueous TBHP
Comparison of molybdenum precatalysts with salicylideneaminothiophenolato (SATP; a tridentate ONS ligand) and salicylideneaminophenolato (SAP; a tridentate ONO ligand) in the solvent-free epoxidation of cyclooctene with aqueous TBHP yields better activity for the former. The DFT study of the catalytic cycle shows that the SATP catalyst follows the same pathway recently established for the SAP analogue and with a slightly smaller activation barrier in agreement with the experimental results.
Wang, Weili,Vanderbeeken, Thibaut,Agustin, Dominique,Poli, Rinaldo
p. 26 - 30
(2015)
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Spectrophotometric and conductometric study of the complexation of N-salicylidene-2-aminophenol with Cu2+in methanol + 1,4-dioxane binary solutions
The complexation reaction between N-salicylidene-2-aminophenol, abbreviated as SAP, with the Cu2+ was studied in binary mixtures of methanol and 1,4-dioxane using conductometric and spectrophotometric methods at different temperatures. The stability constants (Kf) for the 1:1 complex, Cu2+- -SAP, were calculated from computer fitting of the absorbance and molar conductance data against various mole ratios (cM:cL or cL:cM) in different binary solvent mixtures. A non-linear behaviour was observed for the variation of log Kf for the complex against the solvent composition. Various thermodynamic parameters (Δ H, ΔS and ΔG) for the formation of the Cu2+-SAP complex were determined from the temperature dependence of the stability constants (Kf). The overall results showed that the complexation reaction is entropy driven and is affected by the nature and composition of the mixed solvents.
Biswas, Rashmidipta,Brahman, Dhiraj,Sinha, Biswajit
p. 1263 - 1277
(2015)
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Experimental and theoretical investigation of ground state intramolecular proton transfer (GSIPT) in salicylideneaniline Schiff base derivatives in polar protic medium
Ground state intramolecular proton transfer process has been comprehensively investigated in three salicylideneaniline Schiff base derivatives (SB1, SB2, and SB3) using experimental and theoretical methods. It has been confirmed that all the three Schiff base molecules in the ground electronic state exist in the enol form in non-polar and polar aprotic solvents. Keto form is being populated by the polar protic solvent through ground state intramolecular proton transfer (GSIPT) process. Ground state equilibrium between the enol and keto tautomers for SB1 and SB3 is mainly governed by the proton donating ability of the solvent. Ground state equilibria between the enol and keto tautomers of SB2 which is a positional isomer of SB3 is governed by the polarity and proton donating ability of the solvents. Excited state intramolecular proton transfer (ESIPT) process is also evidenced in all the three Schiff base molecules. Theoretical calculations at the B3LYP/cc-pVDZ level in the gas phase and in different solvents using polarisable continuum model (PCM) have failed to establish the GSIPT process. Microsolvation of individual enol and keto conformers has been investigated considering upto three solvent molecules. The energetics of the individual conformers together with the corresponding transition state have been calculated. It has been confirmed that the keto conformer is more stable compared to the enol conformer in microsolvated cluster of three methanol molecules. Lowering of activation energy for the enol to keto tautomerisation in the presence of methanol also supports the experimental observation for GSIPT process. TDDFT/B3LYP/cc-pVDZ single point calculations for microsolvated clusters of enol and keto form of the Schiff base molecules exhibit an excellent agreement with the experimentally obtained absorption spectra. Difference in spectral nature of the Schiff base molecules has been explained using natural bond orbital (NBO) analysis. Quantum theory of atoms in molecules (QTAIM) has also been utilised to understand the GSIPT process in detail.
Das, Bijoya,Chakraborty, Amrita,Chakraborty, Shamik
(2020)
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Spectroscopy and a theoretical study of colorimetric sensing of fluoride ions by salicylidene based Schiff base derivatives
Three colorimetric anion sensors based on salicylidene Schiff bases (salicylaldehyde-o-aminophenol [SA1], 3,5-dimethyl-salicylaldehyde-o-aminophenol [SA2], and 3,5-dichloro-salicylaldehyde-o-aminophenol [SA3] were comprehensively studied based on experimental methods combined with theoretical calculations. All derivatives showed high sensitivity for colorimetric detection of fluoride ions (F?) with a binding stoichiometry of 1:1 in acetonitrile solutions. The color of the sensor solutions visibly changed from light yellow to orange red in the presence of F?. From the experimental results, SA1 and SA2 showed higher potential as F? sensors than SA3 due to their higher selectivity with a limit of detection (LOD) as low as 8 × 10?5, 21 × 10?5 and 7 × 10?5 M, respectively. The optimized structure and electronic transitions were confirmed by DFT and TDDFT studies. In this study, F? detection mechanism is proposed based on experimental and the density functional theory (DFT) calculation.
Hannongbua, Supa,Koonwong, Amonchat,Nakwanich, Buchitar,Poo-arporn, Rungtiva. P.,Prompinit, Panida,Suramitr, Anwaraporn,Suramitr, Songwut
(2021)
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Solvent vapor-induced polarity and ferroelectricity switching
Vapor-induced crystal to crystal transformation between non-polar [Fe(sap)(acac)(sol)] (H2sap = 2-salicylideneaminophenol, acac = acethylacetate, sol = MeOH, pyridine) and polar [Fe(sap)(acac)(DMSO)] was demonstrated. It provides an example of switchable ferroelectric behaviour attributted to the structural phase transition triggered by solvent vapour.
Akiyoshi, Ryohei,Hayami, Shinya,Kobayashi, Fumiya,Kosumi, Daisuke,Lindoy, Leonard F.,Nakamura, Masaaki
p. 10509 - 10512
(2020)
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Experimental and theoretical study of antioxidative properties of some salicylaldehyde and vanillic Schiff bases
The antioxidative capacity and structure-activity relationships of ten Schiff bases were investigated experimentally and theoretically. All compounds contain the aniline moiety, while the aldehyde part is either salicylaldehyde or vanillin. The DPPH assay was used to test the potential antioxidative activity of these compounds, and DFT study was used to investigate their electronic structures and provide insight into their structure-activity relationships. The effect of the position of the hydroxy, as well other groups present, on the antioxidative activity was examined. The possible radical scavenging mechanism was determined in polar (water and methanol), and nonpolar (benzene) solvents. Based on the experimental and computational results, compounds 7 and 8 exhibit the highest radical scavenging properties.
Petrovi?, Zorica D.,Orovi?, Jelena,Simijonovi?, Du?ica,Petrovi?, Vladimir P.,Markovi?, Zoran
p. 24094 - 24100
(2015)
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Syntheses, structural, spectroscopic and magnetic properties of polynuclear Fe(III) complexes containing N and O donor ligands
Syntheses, X-ray structural and spectroscopic properties are reported for [{Fe(L)2}3Fe] (1), [Fe2(L)2(ClCH2COO)2(H2O)] (2) and [Fe(L)(HL)]2 (3) [H2L = a tridentate ONO-donor ligand N-(2-hydroxyphenyl)salicylidenimine]. For (2) and (3), variable temperature magnetic susceptibilities have been measured and modeled. Both are antiferromagnetic overall. Compound 1 has a tetranuclear Fe4O6 core with Fe(III) species at the vertices of a triangle and the fourth Fe(III) at the center of the triangle. The central Fe(III) is surrounded by six phenoxo bridges that connect it to the three peripheral Fe(III) centres. In complex 2, the two six-coordinate Fe(III) centers are bridged by a chloroacetate and two phenoxy oxygens. The remaining three coordination sites on each iron are occupied by a terminal phenoxy oxygen, an imino nitrogen and, in one case, by a water oxygen while in the other by a terminal chloroacetate oxygen. Comparison of 2 with compounds of similar core structure reveals transition between antiferromagnetic and ferromagnetic coupling occurs at a bridgehead angle between ～97°and ～102°. The asymmetric unit of compound 3 consists of two symmetry-independent mononuclear species (Z′ = 2) joined by two statistically equivalent short (2.429(2) and 2.432(2) ?) O?H?O bridges, each involving two phenolic oxygens and a strongly bound H atom. Unprecedented weak antiferromagnetic coupling between the two high spin Fe(III) species via these very strong hydrogen bonds was detected.
Dutta, Amit Kumar,Biswas, Subhendu,Dutta, Supriya,Dawe, Louise N.,Lucas, C. Robert,Adhikary
p. 141 - 149
(2016)
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A DFT and experimental study of the spectroscopic and hydrolytic degradation behaviour of some benzylideneanilines
The spectroscopic and hydrolytic degradation behaviour of some N-benzylideneanilines are investigated experimentally and theoretically via high quality density function theoretical (DFT) modelling techniques. Their absorption and vibrational spectra, accurately predicted by DFT calculations, are highly dependent on the nature of the substituents on the aromatic rings, hence, though some of their spectroscopic features are similar, energetic differences exist due to differences in their electronic structures. Whereas the o-hydroxy aniline derived adducts undergo hydrolysis via two pathways, the most energetically economical of which is initiated by a fast enthalpy driven hydration, over a conservative free energy (ΔG?) barrier of 53 kJ mol?1, prior to the rate limiting entropy controlled lysis step which occurs via a conservative barrier of ca.132 kJ mol?1, all other compounds hydrolyse via a slower two-step pathway, limited by the hydration step. Barriers heights for both pathways are controlled primarily by the structure and hence, stability of the transition states, all of which are cyclic for both pathways.
Nelson, Peter N.,Robertson, Tahjna I.
(2021/10/12)

Aminophenol Schiff base derivative and preparation method and application thereof
The invention discloses an aminophenol Schiff base derivative and a preparation method and application thereof. Wherein, R is H. Substituted alkyl of OH, alkoxy, 1 -4 carbon atoms or substituted alkyl 1-4 carbon atoms. The aminophenol Schiff base derivative has a molecular structure completely different from an existing antifungal drug, provides a new idea for research and development of antifungal drugs, and simultaneously shows good anti-cancer activity.
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Paragraph 0032-0036

(2021/10/20)

Efficient catalytic reduction of 4-nitrophenol using copper(Ii) complexes with n,o-chelating schiff base ligands
The reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride was used as a model to test the catalytic activity of copper(II) complexes containing N,O-chelating Schiff base ligands. In this study, a series of copper(II) complexes containing respective Schiff base ligands, N′-salicylidene-2-aminophenol (1), N′-salicylidene-2-aminothiazole (2), and N,N′-bis(salicylidene)-o-phenylenediamine (3), were synthesized and characterized by elemental analysis, Fourier transform infrared (FT-IR), and UV-Visible (UV-Vis) and electron paramagnetic resonance (EPR) spectroscopies. The results from the 4-nitrophenol reduction showed that 3 has the highest catalytic activities with 97.5% conversion, followed by 2 and 1 with 95.2% and 90.8% conversions, respectively. The optimiza-tion of the catalyst amount revealed that 1.0 mol% of the catalyst was the most optimized amount with the highest conversion compared to the other doses, 0.5 mol% and 1.5 mol%. Recyclability and reproducibility tests confirmed that all three complexes were active, efficient, and possess excellent reproducibility with consistent catalytic performances and could be used again without a major decrease in the catalytic activity.
Abdullahi, Muhammad Sabiu,Endot, Nor Azam,Garba, Hassan Wafi,Jamil, Mohamad Shazwan Shah
(2021/10/05)

Ligand coordination sphere effect of Schiff base cis-dioxomolybdenum(VI) complexes in selective catalytic oxidation of alcohols
Several cis-dioxomolybdenum(VI) complexes with Schiff bases-derived ligands were synthesized and fully characterized. The catalytic performances of these complexes were tested in the alcohol oxidation under solvent-free condition using H2O2 as oxidant giving high results. The influence of the oxygen, sulfur, and nitrogen atom within the coordination sphere around the molybdenum center was studied (S?>?N?>?O). From this study, we suggest that there exists a relationship between the electronegativity of the atom and the catalytic performance in alcohol oxidation.
Liu, Haiwen,Zhuo, Zihan,Zhang, Yan,Wei, Hang,Zhang, Wenxin,Li, Tong,Mao, Zuodong,Wang, Weili
p. 1253 - 1261
(2021/08/13)

Molecular structural, vibrational assignments, electronic structure and DFT calculations, and molecular docking of N-benzylideneaniline and N-salicylidene-o-aminoaphenol Schiff bases
Two Schiff bases N-benzylidenaniline (BZA) and N-salicylidene-o-aminoaphenol (SAP) were synthesized. Structure of SAP was determined by Xrd analysis. It was found that SAP crystallized with two molecules perpendicular to each other and connected by inter- and intramolecular hydrogen bonding. The compound crystallized in the triclinic space group P-1 with a Z value of 2. Geometry optimization of BZA and SAP were investigated by DFT (Gaussian 09W) and REDF2 (Spartan 14). The optimized structure of SAP is consistent with that obtained from the Xrd analysis. Quantum global reactivity descriptors of the two compounds were calculated using the HOMO and LUMO energy values. IR, Raman and theoretical calculations (DFT method) of the vibrational modes of the two derivatives in the wavenumber range 1700–200 cm?1 using Gaussian 09W and Spartan 14 software were carried out. Molecular docking of the two reported compounds with either B-DNA (1ZEW) or protein (4MZI) were studied.
Abo-Aly, Mohamed M.,Lasheen, Alaa A. M.,Ramadan, Ramadan M.
(2021/10/15)

Arene diruthenium(II)-mediated synthesis of imines from alcohols and amines under aerobic condition
The utility and selectivity of the newly synthesized dinuclear arene Ru(II) complex were demonstrated towards the synthesis of imines from coupling of alcohols and amines in the aerobic condition. Analytical and various spectral methods have been used to establish the unprecedented formation of the new thiolato-bridged dinuclear ruthenium complex. The molecular structure of the titled complex was evidenced with aid of X-ray crystallographic technique. A wide range of imines were obtained in good-to-excellent yields up to 98% and water as the by-product through an acceptorless dehydrogenative coupling of alcohols with amines. The catalytic reaction operated a concise atom economical without any oxidant with 1 mol% of the catalyst load. Further, the role of base, solvent and catalyst loading of the coupling reaction has been investigated. A plausible mechanism has been described and was found to proceed via the formation of an aldehyde intermediate. Short synthesis of antibacterial drug N-(salicylidene)-2-hydroxyaniline illustrated the utility of the present protocol.
Tamilthendral, Veerappan,Ramesh, Rengan,Malecki, Jan Grzegorz
(2020/12/15)

Synthesis, spectroscopic, antibacterial and antioxidant activities of Pd(Ii) mixed-ligand complexes containing tridentate schiff bases
Pd(II) complexes of the form [PdLNH3] (where L = N-salicylidene-o-aminophenol (L1), N-(5-methoxysalicylidene-o-aminophenol) (L2) and N-(2-hydroxy-1-naphthalidene)-o-aminophenol) (L3) containing ammonia and ONO tridentate Schiff bases were synthesized. These complexes were characterized by elemental analysis, infrared, ultraviolet-visible, proton and carbon-13 spectroscopies. The NMR spectra showed that the Schiff bases coordinated to the palladium(II) ion through the two deprotonated phenolic oxygen and azomethine nitrogen atoms. The presence of ammonia molecules in these complexes were indicated by the IR and 1H NMR spectra. The spectral data suggested a square planar geometry for the complexes. The biological studies revealed that the complexes displayed better antibacterial and antioxidant activities than the parent Schiff bases.
Demehin,Oladipo,Semire
p. 413 - 426
(2020/11/13)

The preparation of new palladium (II) complexes with Schiff base type ligands and its impregnated Al2O3 materials: As the catalysts for degradation/reduction of organic dyes
The removal of organic dyes used in many sectors such as textile, paper, leather, and packaging from water sources is very important in terms of preventing the spread of industrial pollutants to the environment. Transition metal complexes supported to an inorganic solid material are frequently used for the degradation/reduction of organic dyes causing this pollution. In this study, new Pd (II) complexes with Schiff base ligands were synthesized and structurally characterized by nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), mass spectrometry (MS), and single-crystal X-ray diffraction (sc-XRD) spectroscopic methods. Then, the Al2O3-impregnated materials of these Pd (II) complexes were prepared and characterized by scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), FT-IR, and thermogravimetry (TG) techniques. The catalytic activities of the synthesized Pd (II) complexes and their Al2O3-impregnated materials were comparatively analyzed to investigate the degradation/reduction of organic dyes (2-nitroaniline, 4-nitroaniline, 4-nitrophenol, eosin yellow, and methylene blue). The catalytic results indicate that Al2O3-impregnated materials are very active catalysts for the degradation/reduction of organic dyes under those circumstances. Conversions of up to 98% for all substrates were obtained after 5 min at ambient temperature.
Selvi, Gizem,Tercan, Melek,?zdemir, Nam?k,Dayan, Osman
(2020/09/09)

Mechanistic Features of the Oxidation-Reductive Coupling of Alcohols Catalyzed by Oxo-Vanadium Complexes
The oxo-vanadium-catalyzed redox disproportionation of activated alcohols (oxidation-reductive coupling, Ox-RC) produces carbonyl compounds and hydrocarbon dimers. A mechanistic study of this novel reaction is reported herein. Following our initial disclosure, new findings include the following: (1) The [(salimin)VO2]--catalyzed Ox-RC of Ph2CHOH in the presence of fluorene affords the products of H-atom abstraction and all possible hydrocarbon dimers. (2) Electronic substituent effects on the relative rates of Ox-RC with respect to 4-X-BnOH reactants and Bu4N[(Y-salimin)VO2] catalysts (1a-c) reveal (a) a correlation of the oxidation rate of X-BnOH reactants with the radical σ parameter and (b) correlation of the oxidation rate for (Y-salimin)VO2- with the standard Hammett σ parameter. (3) The ease of electrochemical reduction of 1a-c is Y = NO2 > OMe > H. (4) Ambient 1H NMR studies of the interaction of 1 with alcohols suggest only a weak equilibrium association. (5) Density functional theory computational modeling of the Ox-RC reaction supports a ping-pong-type catalytic pathway, beginning with alcohol oxidation by (salimin)VO2-, preferably by stepwise-H-atom transfer from the alcohol to 1, affording the carbonyl product and the reduced (salimin)V(III)(OH)2-. The reduction half-reaction likely begins with condensation of the latter species with R2CHOH to give the alkoxide complex (salimin)V(OR)OH- homolysis of the R···OV(III)(salimin) bond affords (salimin)V(IV)OH(O)- and the R-radical; the latter dimerizes and the former can disproportionate via H-transfer to reform catalyst (salimin)VO2- (1) and (salimin)V(OH)2-.
Steffensmeier, Eric,Swann, Matthew T.,Nicholas, Kenneth M.
p. 844 - 854
(2019/01/04)

V(V)-Schiff base species induce adipogenesis through structure-specific influence of genetic targets
Vanadium has been known to exhibit numerous functions in biological systems, projecting exogenous activity linked to regulatory roles in cell metabolism and insulin mimesis. Poised to probe into the vanadium adipogenic potential, reflecting on efficient anti-diabetic drugs, research was launched in our labs to pursue the (a) synthesis of diversely structured Schiff base ligands, as vanadium chelating binders, containing a variably configured o-vanillin core with a specified common organic o-aminophenol tether, (b) synthesis of a family of well-defined soluble vanadium-Schiff base compounds, bearing the above mentioned Schiff ligands (and in one case 4,4'-bipyridine), (c) study of their toxicity profile and adipogenic activity in 3T3-L1 fibroblasts toward mature adipocytes, and (d) determination of molecular biological targets linked to the vanadium-induced cell differentiation process, thereby unravelling factors impacting signaling pathways influencing insulin mimesis. The results suggest that (a) all emerging vanadospecies contain V(V) mononuclear centers bound to Schiff bases (and 4,4'-bipyridine), (b) a welldefined (solid-state and solution) physicochemical profile of all species justifies their selection in biological studies, (c) the vanadium toxicity profile is strongly related to the form of V(V) (complexed forms, substrate-ligand nature), (d) there is a structure-specific behavior of vanadium influencing adipogenesis, and (e) molecular target loci are also influenced by vanadoforms in a structure-specific fashion, thereby collectively projecting an interwoven role of factors emanating from vanadium and impacting cell differentiation and insulin mimetic activity. The so far accrued knowledge constitutes the basis for further development of biomarker-driven structure-specific vanadodrugs, contributing through insulin biomimicry to therapeutic technologies in Diabetes mellitus.
Tsave,Halevas,Yavropoulou,Yovos,Hatzidimitriou,Psycharis,Ypsilantis,Stathi,Salifoglou
supporting information
p. 17872 - 17890
(2019/12/30)

Fe3O4@SiO2@Im[Cl]Mn(III)-complex as a highly efficient magnetically recoverable nanocatalyst for selective oxidation of alcohol to imine and oxime
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
p. 230 - 249
(2019/03/28)

Iron(III) Complexes of Vitamin B6 Schiff Base with Boron-Dipyrromethene Pendants for Lysosome-Selective Photocytotoxicity
Iron(III) complexes of a vitamin B6 Schiff base and NNN-donor ligands with pendant boron-dipyrromethene (BODIPY) moieties; namely, [Fe(L1–3)(L4,5)](NO3) (1–4), where L1 is benzyl-bis[(pyridin-2-yl)methyl]methanamine (bzdpa in 1), L2 is a noniodinated BODIPY-appended dipicolylamine ligand (in 2, 3), L3 is the diiodinated BODIPY analogue in 4, L4 is a vitamin B6 Schiff base, namely 3-hydroxy-5(hydroxymethyl)-4-{[(2-hydroxyphenyl)imino]methyl}-2-methylpyridine (in 1, 3, and 4), and L5 is 2-[(2-hydroxyphenylimino)-methyl]phenol (in 2) as a nonpyridoxal Schiff base, were prepared, characterized, and their cellular localization and cytotoxic activity in light and in the dark were studied. The diiodo–BODIPY complex 4 displays remarkable photoinduced cytotoxicity in visible light (400–700 nm), with IC50 values within 0.11–0.25 μm and about 200-fold lower dark toxicity. Complex 3, being fluorescent, was used for cellular imaging by confocal microscopy. Complex 4 shows supercoiled pUC19 DNA cleavage activity through the generation of singlet oxygen (1O2) as the reactive oxygen species (ROS). Selective uptake of the complexes is observed from competitive cellular incorporation assays in cancer and noncancer cells. The complexes also show no apparent toxicity up to 100 μm in the immortal human lung epithelial cells HPL1D in both light and the dark. Complex 3 shows preferential accumulation in lysosomes, giving a Pearson's correlation coefficient value of about 0.7.
Sahoo, Somarupa,Podder, Santosh,Garai, Aditya,Majumdar, Shamik,Mukherjee, Nandini,Basu, Uttara,Nandi, Dipankar,Chakravarty, Akhil R.
supporting information
p. 1522 - 1532
(2018/04/20)

In vitro and in vivo anti-inflammatory properties of imine resveratrol analogues
Resveratrol is a natural polyphenol found mainly on red grapes and in red wine, pointed as an important anti-inflammatory/immunomodulatory molecule. However, its bioavailability problems have limited its use encouraging the search for new alternatives agents. Thus, in this study, we synthetize 12 resveratrol analogues (6 imines, 1 thioimine and 5 hydrazones) and investigated its cytotoxicity, antioxidant activity and in vitro anti-inflammatory/immunomodulatory properties. The most promising compounds were also evaluated in vivo. The results showed that imines presented less cytotoxicity, were more effective than resveratrol on DPPH scavenger and exhibited an anti-inflammatory profile. Among them, the imines with a radical in the para position, on the ring B, not engaged in an intramolecular hydrogen-interaction, showed more prominent anti-inflammatory activity modulating, in vivo, the edema formation, the inflammatory infiltration and cytokine levels. An immunomodulatory activity also was observed in these molecules. Thus, our results suggest that imines with these characteristics presents potential to control inflammatory disorders.
Zimmermann-Franco, Danielle Cristina,Esteves, Bruna,Lacerda, Leticia Moroni,Souza, Isabela de Oliveira,Santos, Juliana Alves dos,Pinto, Nícolas de Castro Campos,Scio, Elita,da Silva, Adilson David,Macedo, Gilson Costa
p. 4898 - 4906
(2018/09/11)

Inhibition of copper-mediated aggregation of human γD-crystallin by Schiff bases
Abstract: Protein aggregation, due to the imbalance in the concentration of Cu2+ and Zn2+ ions is found to be allied with various physiological disorders. Copper is known to promote the oxidative damage of β/γ-crystallins in aged eye lens and causes their aggregation leading to cataract. Therefore, synthesis of a small-molecule ‘chelator’ for Cu2+ with complementary antioxidant effect will find potential applications against aggregation of β/γ-crystallins. In this paper, we have reported the synthesis of different Schiff bases and studied their Cu2+ complexation ability (using UV–Vis, FT-IR and ESI-MS) and antioxidant activity. Further based on their copper complexation efficiency, Schiff bases were used to inhibit Cu2+-mediated aggregation of recombinant human γD-crystallin (HGD) and β/γ-crystallins (isolated from cataractous human eye lens). Among these synthesized molecules, compound 8 at a concentration of 100 μM had shown ~95% inhibition of copper (100?μM)-induced aggregation. Compound 8 also showed a positive cooperative effect at a concentration of 5–15 μM on the inhibitory activity of human αA-crystallin (HAA) during Cu2+-induced aggregation of HGD. It eventually inhibited the aggregation process by additional ~20%. However, ~50% inhibition of copper-mediated aggregation of β/γ-crystallins (isolated from cataractous human eye lens) was recorded by compound 8 (100 μM). Although the reductive aminated products of the imines showed better antioxidant activity due to their lower copper complexing ability, they were found to be non-effective against Cu2+-mediated aggregation of HGD. Graphical Abstract: [Figure not available: see fulltext.]
Chauhan, Priyanka,Muralidharan, Sai Brinda,Velappan, Anand Babu,Datta, Dhrubajyoti,Pratihar, Sanjay,Debnath, Joy,Ghosh, Kalyan Sundar
p. 505 - 517
(2017/06/05)

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
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
p. 1917 - 1933
(2017/08/15)

Co(II) Schiff base complex decorated on polysalicylaldehyde as an efficient, selective, heterogeneous and reusable catalyst for epoxidation of olefins in mild and self-coreductant conditions
Abstract: A new Co(II)-Schiff base complex was decorated on a polysalicylaldehyde (PSA) framework and used as a selective and efficient catalyst for the epoxidation of alkenes in the presence of O2 as a green source of oxygen without aco-reductant. The catalyst was characterized step by step by FTIR, UV–Vis, 1H NMR, TGA, CHN, XPS and EDX analyses. Loading an amount of Co ions in the catalyst as well as its leaching amount were studied by an ICP-OES instrument. The catalyst demonstrated excellent activity for the of a variety of alkenes in a mild, inexpensive and efficient protocol. Also, the catalyst can be simply recovered from the reaction mixture and reused for several times without any noteiceable loss in its activity. Reaction parameters including temperature, oxygen flow volume, catalyst amount and solvent were screened by reaction time. Catalytic studies including XPS spectroscopy and some blank experiments were performed to obtain an initial insight into the reaction mechanism. Also, the reactivity of the novel catalyst was evaluated as the turnover frequency. Graphical Abstract: A new and efficient protocol have been developed for the selective epoxidation of olefins using a heterogeneous recyclable Co(II)-Schiff base complex of polysalicylaldehyde in mild and self-coreductant conditions by molecular oxygen.
Kazemnejadi, Milad,Shakeri, Alireza,Nikookar, Mahsa,Mohammadi, Mohammad,Esmaeilpour, Mohsen
p. 6889 - 6910
(2017/10/05)

Towards a global greener process: from solvent-less synthesis of molybdenum(vi) ONO Schiff base complexes to catalyzed olefin epoxidation under organic-solvent-free conditions
Nine Schiff base ligands derived from o-hydroxyaldehydes (2-hydroxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde, 2-hydroxy- 1-naphthaldehyde) and nine corresponding dioxomolybdenum(vi) complexes, cis-[MoO2L(CH3OH)] or cis-[MoO2L(CH3OH)]·CH3OH and dinuclear [MoO2L]2, have been prepared using the conventional solution-based method as well as mechanochemically, by liquid assisted grinding (LAG). All products have been characterised by means of IR spectroscopy, thermal analyses and also by powder and five molybdenum complexes by single crystal X-ray diffraction. The crystal structure analysis of mononuclear complexes reveal distorted octahedral Mo(vi) coordination by ONO donor atoms from a dianionic tridentate Schiff base ligand, two oxido oxygen atoms from the MoO22+ moiety and an oxygen atom from the MeOH molecule trans to the oxido oxygen atom. Due to the trans effect of the oxido oxygen atom, Mo-O(MeOH) is the longest bond distance within the Mo coordination sphere and it expected to be the point of maximum reactivity of the complexes. All complexes have been studied as pre(catalysts) for the epoxidation of cis-cyclooctene, cyclohexene and (R)-limonene using aqueous tert-butyl peroxide (TBHP) as the oxidant and in the absence of an organic solvent.
Cindri?, Marina,Pavlovi?, Gordana,Katava, Robert,Agustin, Dominique
supporting information
p. 594 - 602
(2017/02/05)

Aluminum complexes containing salicylbenzoxazole ligands and their application in the ring-opening polymerization of: Rac -lactide and ?-caprolactone
Two series of four-coordinate aluminum (1a-9a) and five-coordinate aluminum (1b-9b) complexes were successfully synthesized via the reactions between the corresponding salicylbenzoxazole ligands and 1 or 0.5 equivalents of AlMe3, respectively. The synthesized aluminum complexes were characterized by 1H and 13C NMR spectroscopy and elemental analysis. The solid-state structures of complexes 7a and 1b were determined using single crystal X-ray diffraction. Upon addition of 1 equivalent of benzyl alcohol, all complexes were efficient initiators for the ring-opening polymerization (ROP) of rac-lactide (rac-LA) and ?-caprolactone (?-CL). The polymerizations were living with a good control over molecular weights and molecular weight distributions. Under immortal polymerization conditions, all four-coordinate aluminum complexes (1b-9b) exhibited a living polymerization with the obtained molecular weights proportional to the ratio of monomer/benzyl alcohol and the PDIs were narrow. Kinetic studies revealed that both rac-LA and ?-CL polymerizations mediated by all complexes were first-order in monomers. The effects of ligand structure and coordination geometry on the catalytic activity and stereoselectivity were discussed. A good isoselectivity control was achieved for the polymerizations mediated by complexes 4b (Pm = 0.75), 5b (Pm = 0.74), and 9b (Pm = 0.74).
Sumrit, Pattarawut,Chuawong, Pitak,Nanok, Tanin,Duangthongyou, Tanwawan,Hormnirun, Pimpa
supporting information
p. 9250 - 9266
(2016/06/14)

Influence of Tuned Linker Functionality on Modulation of Magnetic Properties and Relaxation Dynamics in a Family of Six Isotypic Ln2 (Ln = Dy and Gd) Complexes
A coordination complex family comprising of six new dinuclear symmetric lanthanide complexes, namely, [Ln2(Lx)2(L′)2(CH3OH)2]·yG (H2Lx: three related yet distinct Schiff-base linkers; x = 1-3, according to the nomenclature of the Schiff-base linker employed herein. HL′: 2,6-dimethoxyphenol. yG refers to crystallographically assigned guest solvent species in the respective complexes; y = number of solvent molecules; LnIII = Dy/Gd) were isolated employing a mixed-ligand strategy stemming out of a strategic variation of the functionalities introduced among the constituent Schiff-base linkers. The purposeful introduction of three diverse auxiliary groups with delicate differences in their electrostatic natures affects the local anisotropy and magnetic coupling of LnIII ion-environment in the ensuing Ln2 dinuclear complexes, consequentially resulting into distinctly dynamical magnetic behaviors among the investigated new-fangled family of isotypic Ln2 complexes. Among the entire family, subtle alterations in the chemical moieties render two of the Dy2 analogues to behave as single molecule magnets, while the other Dy2 congener merely exhibits slow relaxation of the magnetization. The current observation marks one of the rare paradigms, wherein magnetic behavior modulation was achieved by virtue of the omnipresent influence of subtly tuned linker functionalities among the constituent motifs of the lanthanide nanomagnets. To rationalize the observed difference in the magnetic coupling, density functional theory and ab initio calculations (CASSCF/RASSI-SO/POLY-ANISO) were performed on all six complexes. Subtle difference in the bond angles leads to difference in the J values observed for Gd2 complexes, while difference in the tunnel splitting associated with the structural alterations lead to variation in the magnetization blockade in the Dy2 complexes.
Mukherjee, Soumya,Lu, Jingjing,Velmurugan, Gunasekaran,Singh, Shweta,Rajaraman, Gopalan,Tang, Jinkui,Ghosh, Sujit K.
p. 11283 - 11298
(2016/11/17)

Nickel(II) Schiff base complexes: Synthesis, characterization and catalytic activity in Kumada-Corriu cross-coupling reactions
The syntheses of ten new Ni(II) complexes 5a-5j with H2L tridentate (ONO) Schiff-base ligand (2-((2-oxybenzylidene)amino)phenolate) have been described and fully characterized by means of elemental analysis, FT-IR, electronic, 1H NMR and 13C NMR spectroscopy and single-crystal X-ray diffraction. In all [Ni(L)B] complexes (where B are imidazole, 4-benzylpyridine, 2-methyl-5-ethylpyridine, 3-hydroxymethylpyridine, 2-methylbenzimidazole, 2,6-dimethylpyridine, 4-methylpyridine, 2-isopropylbenzimidazole, 4-methylpiperidine or triphenylphosphine) the Schiff base completely deprotonates and coordinates to the metal ion as a dianionic tridentate ligand via the donor oxygens and nitrogen atoms. The coordination number of Ni(II) atoms is four with distorted square-planar stereochemistry. This is in a good agreement with the ligand field band position in their electronic spectra, as well as with the X-ray structure analysis for all complexes under study. Six selected complexes are used as catalysts for Kumada-Corriu cross-coupling reactions and exhibit a moderate to good catalytic activity in the synthesis of biaryl derivatives.
Kuchtanin, Vladimír,Kle??íková, Lucia,?oral, Michal,Fischer, Róbert,R??i?ková, Zdeňka,Rakovsky, Erik,Monco?, Ján,Seg?a, Peter
p. 90 - 96
(2016/07/06)

OH-substituted tridentate ONO Schiff base ligands and related molybdenum(VI) complexes for solvent-free (ep)oxidation catalysis with TBHP as oxidant
Molybdenum complexes with ONO tridentate Schiff base ligands based on salicylideneaminophenolato (SAP) backbone with OH substitution on the salicyl arene ring have been synthesized and characterized. The molecular structures of the full series of OH substituted molybdenum complexes were determined by X-ray crystallography as monomers stabilized by one solvent molecule, [MoO2L(D)]. All dimeric complexes [MoO2L]2 were tested for the epoxidation of cyclooctene and cyclohexene under organic solvent-free conditions using aqueous TBHP as oxidant. The position of the OH on the SAP-modified ligand influenced the catalytic activity of the respective complexes. DFT calculations for the catalytic cycle yield energy spans in agreement with the experimentally observed activity trend.
Wang, Weili,Daran, Jean-Claude,Poli, Rinaldo,Agustin, Dominique
p. 117 - 126
(2016/04/04)

Schiff base triphenylphosphine palladium (II) complexes: Synthesis, structural elucidation, electrochemical and biological evaluation
The complexes N-(2-oxidophenyl)salicylideneiminatotriphenylphosphine palladium(II) (1) and N-(2-sulfidophenyl)salicylideneiminato triphenylphosphine palladium(II) (2) of tridentate Schiff bases derived from salicylaldehyde and an amino- or thiophenol, have been synthesized and characterized by various spectroscopic, analytical and electro-analytical techniques. X-ray single crystal analysis of complex 1 has revealed its square planar geometry. The thermal analysis has shown the absence of coordinated water and final degradation product is PdO. The alkaline phosphatase studies have indicated that enzymatic activity is concentration dependent which is inversely proportional to the concentration of the compounds. The biological assays (brine shrimp cytotoxicity, DPPH) have reflected their biologically active and mild antioxidant nature. However, results of DNA protection assay have shown that they possess moderate protective activity against hydroxyl free radicals (OH). The voltammetric studies ascertain two-electron reduction of the compounds through purely diffusion controlled process and reveal intercalative mode of drug DNA interactions.
Shabbir, Muhammad,Akhter, Zareen,Ahmad, Iqbal,Ahmed, Safeer,Shafiq, Maryam,Mirza, Bushra,McKee, Vickie,Munawar, Khurram Shahzad,Ashraf, Ahmad Raza
p. 250 - 258
(2016/04/26)

Palladium catalyzed synthesis method of 2-(2 '-hydroxy phenyl) benzoxazole
The present invention discloses a palladium-catalyzed synthesis method of 2-(2 '-hydroxy phenyl) benzoxazole, HBO is shorted for 2-(2 '-hydroxy phenyl) benzoxazole in English, a chemical molecular formula is C14H13NO2 , the molecular structural formula is as shown in the specification, the synthesis method is as follows: firstly a condensation reaction is performed to obtain a red needle-like crystal Schiff base intermediate 1; then the intermediate 1 is oxidized for ring formation reaction to obtain the final compound HBO. The method has the following beneficial effects: the synthesis method is simple in process, readily available in raw materials, easy to implement, mild in reaction conditions, high in product yield and less in by-products, and has a wide range of application.
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Paragraph 0024; 0032; 0033; 0034; 0035

(2016/10/27)

Hepta-coordinated heteroleptic derivatives of zirconium(IV): Synthesis, structural characterization and ring opening polymerization of ε-caprolactone
A series of new hepta-coordinated heteroleptic derivatives of zirconium(IV) of the types [(CH3COCHCOCH3)2ZrL] (1, 3, 5 and 7) and [(C6H5COCHCOC6H5)2ZrL] (2, 4, 6 and 8) (L?=?a dianionic [ONO]-tridentate ancillary ligand) was synthesized quantitatively by reacting Zr(OPri)4·PriOH with the tridentate Schiff's base ligands H2Lx(H2L1?=?C13H11NO2; H2L2?=?C13H10BrNO2; H2L3?=?C14H13NO3; H2L4?=?C17H13NO2) and β-diketones (acetylacetone/dibenzoylmethane) in a 1:1:2 stoichiometry using dry benzene and ethanol as solvents. All these newly synthesized solid derivatives were fairly soluble in common organic solvents. They were characterized by elemental analyses, FTIR and NMR (1H and13C) spectral studies. Single crystal XRD data of complexes 1, 2, 3 and 5 indicated the hepta-coordination and monomeric nature of these complexes. Furthermore, all these derivatives were tested for the ring opening polymerization of ε-caprolactone. The dibenzoylmethane derivatives were inactive in polymerizing ε-caprolactone unlike the acetylacetonate complexes. The molecular weight and polydispersity index values of polycaprolactone were obtained by GPC analysis. Kinetic studies for the rate of polymerization of ε-caprolactone by these catalytically active zirconium(IV) complexes authenticated the first order dependence of the polymerization rate on the monomer concentration. Among these, complex 3, with an electronegative bromine atom on the Schiff's base moiety, exhibited the best catalytic activity with a conversion of >95% in 2?h.
Vuppalapati, Giri Prasanth,Rathore, Ravindranath S.,Pathak, Madhvesh,Kulathu Iyer, Sathiyanarayanan
p. 163 - 171
(2016/09/28)

Group 4 complexes of salicylbenzoxazole ligands as effective catalysts for the ring-opening polymerization of lactides, epoxides and copolymerization of ε-caprolactone with L-lactide
A series of salicylbenzoxazole pro-ligand 2-(5-X-benzoxazol-2-yl)-6-R1-4-R2-phenol, L1H-L4H were subjected to reaction with titanium, zirconium and hafnium alkoxides. The substituents (R1, R2, X) present in the pro-ligand back bone are (H, H, H) for L1H; (H, H, Cl) for L2H; (Br, Br, H) for L3H; and (Cl, Cl, H) for L4H. The mononuclear Ti complexes, 1a-4a of [M(L)2(OiPr)2] formulation were prepared by combining the pro-ligands L1H-L4H with Ti(OiPr)4 in dry toluene. However, with the addition of H2O (0.5?M equiv.), the controlled hydrolysis of Ti complex 4a in a mixed solvent of THF/toluene produced oxo-bridged dinuclear Ti complex 5a having [M(μ-O)(L)2(OiPr)]2 formulation in good yield (≥75%) using L4H as the pro-ligand. The composition of the mononuclear Zr and Hf complexes of L1H-L4H are found to be quite similar to that of the Ti complexes. Additionally, mononuclear Zr complexes 1b-4b and Hf complexes 1c-4c were prepared. The oxo-bridged dinuclear Zr and Hf complexes 5b and 5c were isolated from the controlled hydrolysis reactions of mononuclear Zr and Hf complexes 4b and 4c. All these complexes were well characterized and crystal structure of six of the fifteen complexes were determined. These complexes were used as initiators for the ring-opening polymerization (ROP) of rac-LA, copolymerization of L-LA with ε-CL and homopolymerization of rac-epoxides. In particular, the dinuclear Zr complex (5b) was found to exhibit extremely high activity in these polymerization studies. Iso-enriched polymers were observed upon using the Zr and Hf complexes of the pro-ligands L3H or L4H as the initiator. DFT studies have been carried out on the ROP of lactides initiated by the Ti, Zr and Hf complexes 1a, 1b and 1c. The results indicated that the activation barrier to reach the transition state using Zr complexes is lower and hence facile as compared to the Ti and Hf complexes.
Pappuru, Sreenath,Chakraborty, Debashis,Vijaya Sundar,Roymuhury, Sagnik K.,Ramkumar, Venkatachalam,Subramanian, Vinodh,Chand, Dillip Kumar
p. 231 - 247
(2016/09/21)

Mixed ligand complexes with 4-aminoantipyrine derivatives to combat natural antioxidant system: Synthesis, characterization and biological studies
Novel 4-aminoantipyrine based mixed ligand metal complexes with the Schiff bases of L1 (L1-4-aminoantipyrine with furfuraldehyde and L2/L3/L4/L5 are and L2-2-aminophenol with salicylaldehyde, L3-2-aminophenol with cinnamaldehyde, L4-2-aminobenzothiazole with salicylaldehyde, L5-2-aminobenzothiazole with cinnamaldehyde) were synthesized. The structures of the mixed ligand complexes were established by analytical and spectral techniques. They were screened for in vitro antimicrobial activity against of bacteria and fungi by disc diffusion method. The interaction of metal complexes with calf thymus-DNA (CT-DNA) was investigated by UV-visible, cyclic voltammetry, viscosity and thermal denaturation studies. DNA interaction studies suggest that metal complex binds to calf thymus-DNA through intercalation mode. Superoxide dismutase activity of these complexes has also been studied. The free ligands and their metal complexes have been tested for in vitro antioxidant activity by the reduction of 1,1-diphenyl-2-picryl hydrazyl (DPPH). The antioxidant activities of the complexes were studied and compared with the activity of ascorbic acid. Copper(II) complex showed superior antioxidant activity than other complexes.
Joseph,Rani, G. Ayisha Bibin
p. 790 - 802
(2015/02/05)

Iron(III) complexes of a pyridoxal Schiff base for enhanced cellular uptake with selectivity and remarkable photocytotoxicity
Iron(III) complexes of pyridoxal (vitamin B6, VB6) or salicylaldehyde Schiff bases and modified dipicolylamines, namely, [Fe(B)(L)](NO3) (1-5), where B is phenyl-N,N-bis((pyridin-2-yl)methyl)methanamine (phbpa in 1), (anthracen-9-yl)-N,N-bis((pyridin-2-yl)methyl)methanamine (anbpa in 2, 4) and (pyren-1-yl)-N,N-bis((pyridin-2-yl)methyl)methanamine (pybpa in 3, 5) (H2L1 is 3-hydroxy-5-(hydroxymethyl)-4-(((2-hydroxyphenyl)imino)methyl)-2-methylpyridine (1-3) and H2L2 is 2-[(2-hydroxyphenyl-imino)methyl]phenol), were prepared and their uptake in cancer cells and photocytotoxicity were studied. Complexes 4 and 5, having a non-pyridoxal Schiff base, were prepared to probe the role of the pyridoxal group in tumor targeting and cellular uptake. The PF6 salt (1a) of complex 1 is structurally characterized. The complexes have a distorted six-coordinate FeN4O2 core where the metal is in the +3 oxidation state with five unpaired electrons. The complexes display a ligand to metal charge transfer band near 520 and 420 nm from phenolate to the iron(III) center. The photophysical properties of the complexes are explained from the time dependent density functional theory calculations. The redox active complexes show a quasi-reversible Fe(III)/Fe(II) response near -0.3 V vs saturated calomel electrode. Complexes 2 and 3 exhibit remarkable photocytotoxicity in various cancer cells with IC50 values ranging from 0.4 to 5 μM with 10-fold lower dark toxicity. The cell death proceeded by the apoptotic pathway due to generation of reactive oxygen species upon light exposure. The nonvitamin complexes 4 and 5 display 3-fold lower photocytotoxicity compared to their VB6 analogues, possibly due to preferential and faster uptake of the vitamin complexes in the cancer cells. Complexes 2 and 3 show significant uptake in the endoplasmic reticulum, while complexes 4 and 5 are distributed throughout the cells without any specific localization pattern.
Basu, Uttara,Pant, Ila,Hussain, Akhtar,Kondaiah, Paturu,Chakravarty, Akhil R.
supporting information
p. 3748 - 3758
(2015/05/04)

Substituent effects on the absorption and vibrational spectra of some 2-hydroxy Schiff bases: DFT/TDDFT, natural bond orbital and experimental study
The electronic structure of salicylideneaniline (SA) and some of its derivatives are investigated both experimentally and theoretically. The equilibrium geometric structures of the studied compounds are determined at the B3LYP/6-311++Glevel of theory. A set of 12 substituted SA derivatives is considered in the present work. The choice of these substituents aims to create a push-pull system on the SA basic structure which would shade light onto its photo physics. The electronic absorption spectra of SA are recorded in the UV-VIS region, in both polar and nonpolar solvents. Assignments of the observed electronic transitions are facilitated via time-dependent density functional theory (TDDFT) computations at the same level of theory. Electronic configurations contributing to each excited state are identified and the relevant MOs are characterized. The extent of delocalization and intramolecular charge transfer are estimated and discussed in terms of natural bond orbitals (NBO) analysis and second order perturbation interactions between donor and acceptor MOs. Solvent effects on the electronic absorption spectra are discussed in terms of the difference in polarizabilities of the ground and excited states. FTIR spectra of SA and its derivatives are measured in KBr platelets. Detailed vibrational assignments are given based on the calculated potential energy distributions. "IR marker bands" that characterize the SA framework are identified. The effect of substituents, the nature of the characteristic "marker bands", and intensity quenching of some bands are discussed.
Elroby,Aboud,Aziz,Hilal
p. 414 - 427
(2015/08/06)

Comparison of chelating ability of NO-, NS-, ONS-, and ONO-type Schiff base derivatives and their stability constants of Bis-complexes with copper(II)
The present study includes important findings relating to the number of donor atoms, species of ligands, and stabilities of complexes. Stabilities of complexes between Cu(II) ion and NO-, NS-, ONS-, and ONO-type Schiff bases were compared. Acid-base properties of the Schiff bases were explained at 25 ± 0.1 ° C and ionic strength (I) of 0.1 M supported by NaCl. The Hyperquad computer program was used for calculation of dissociation and stability constants. The overall stability constants of their Cu(II) complexes were calculated and the various formed complexes between the Schiff bases with Cu(II) ion formulated as CuL2, CuHL2, CuH2L 2, and CuH-1L2(Cu (OH) L2). The complexes of ONS- and ONO-type tridentate ligands were more stable than those of NO- and NS-type bidentate ligands. TUeBITAK.
Atabey, Hasan,Findik, Esra,Sari, Hayati,Ceylan, Mustafa
p. 109 - 120
(2014/02/14)

Open-air N-arylation of N-H heterocycles with arylboronic acids catalyzed by copper(II) Schiff base complexes
Two copper Schiff base complexes, in both homogeneous and heterogeneous forms, were prepared and characterized by using elemental analysis, FTIR, UV-Vis spectroscopy and scanning electron microscopy. The catalytic performances of these complexes were studied in the N-arylation of N-H heterocycles with arylboronic acids in methanol without any added base at 40 °C under open air. The effects of various parameters such as solvent and temperature on the reaction system were studied. The reaction is applicable to a wide variety of N-H heterocycles and arylboronic acids. The heterogeneous catalyst was recovered by simple filtration, and reusability experiments showed that this catalyst can be used five times without much loss in the catalytic activity.
Islam,Dey, Ram Chandra,Roy, Anupam Singha,Paul, Sumantra,Mondal, Sanchita
p. 961 - 969
(2015/01/09)

Modified clinoptilolite used for removing azomethines from wastewaters. II. Adsorption of azomethines from wastewaters on clinoptilolite
The native clinoptilolite volcanic tuff (NT) and its Na form (NaNT) as well as dealuminated clinoptilolite (DNT) and its Na form (DNaNT) were investigated as efficient adsorbents for separating the 2,2′-dihydroxydiphenyl azomethine from wastewaters. The effect of parameters such as the pH dye solution, contact time and temperature of adsorption process was examined. The studies show that the DNT and DNaNT samples have a higher capacity of adsorption in comparison with the NT and NaNT samples. Also, the amounts of azomethine dye retained on the dealuminated clinoptilolite are much higher at 60°C than at 40°C. Thus, the adsorbed amount of azomethine dye on DNT sample was about 85% at 60°C, pH=4 and contact time 60 min. (Graph Presented).
Cobzaru, Claudia,Cernatescu, Corina,Marinoiu, Adriana
p. 1089 - 1096
(2015/07/15)

Photoprotective activity of resveratrol analogues
Resveratrol is a promising agent for protecting human skin from UV radiation and to reduce the occurrence of cutaneous malignancies. We describe the photoprotective activity of six resveratrol analogues using the diffuse transmittance technique to determine the SPF and the protection against UVA radiation. The analogues presented a varied profile of photoprotection, the SPF ranging from 2 to 10 and the UVAPF from 0 to 9. Among the six compounds tested, the protection against UVB sunrays provided by compound B was more significant than the protection provided by resveratrol; compounds C, D, E and F show photoprotection similar to resveratrol.
Polonini, Hudson Caetano,Lima, Larissa Lavorato,Goncalves, Karla Mara,Do Carmo, Antonio Marcio Resende,Da Silva, Adilson David,Raposo, Nadia Rezende Barbosa
p. 964 - 968
(2013/04/10)

In situ modification of the Grubbs first generation catalyst: A highly controllable metathesis catalyst bearing tridentate Schiff base ligands
In this study, a practical and inexpensive procedure for the modification of the Grubbs first generation catalyst is reported. A highly controllable metathesis catalyst system was obtained by in situ modification of the Grubbs catalyst with tridentate Schiff base (ONO) ligands. The latent catalyst was activated by the addition of HCl, which allowed control of its initiation rate by varying the HCl/Ru ratio. Due to the superior control over the catalyst initiation step, improved molecular weight control in the ring-opening metathesis polymerization (ROMP) of cyclooctene (COE) was achieved using these complexes. ROMP polymers obtained by these catalyst systems have relatively narrow molecular weight distributions, and the molecular weight of the polymers can be controlled on a wide scale. In addition, the reversible inhibition and activation of the catalysts were studied the in ring-closing metathesis reaction (RCM) of diethyldiallylmalonate. RCM of diethyldiallylmalonate can be halted by the introduction of tridentate Schiff base ligands to the reaction medium. The reaction can be switched on again by the introduction of trace amounts of HCl.
?ztürk, Bengi ?zgün,Bucak, Emel,Karabulut, Solmaz
p. 53 - 62
(2013/07/11)

Cyanide as a powerful catalyst for facile synthesis of benzofused heteroaromatic compounds via aerobic oxidation
Highly efficient synthesis of benzofused heteroaromatic compounds via aerobic oxidation catalyzed by cyanide anion has been developed. The Schiff bases derived from 2-aminophenol and aldehydes provided the corresponding benzoxazoles in high yields in the presence of a catalytic amount of cyanide in an open flask under ambient conditions without the use of any external metal co-oxidants and bases. Furthermore, we have developed a catalytic sequential one-step protocol for the synthesis of benzoxazoles by adding a catalytic amount of NaCN to Schiff bases generated in situ from 2-aminophenol and aldehydes without the isolation of imine intermediates. This one-pot protocol was further extended to the synthesis of benzothiazoles from 2-aminothiophenol and aldehydes. A variety of aldehydes could be applied to this sequential one-pot protocol and the desired benzofused azole products were obtained in high yields.
Cho, Yeon-Ho,Lee, Chun-Young,Cheon, Cheol-Hong
p. 6565 - 6573
(2013/07/26)

Encapsulation of the BeII cation: Spectroscopic and computational study
The structures of a series of tetracoordinate beryllium(II) complexes with ligands derived from tertiary-substituted amines have been computationally modeled and their 9Be magnetic shielding values determined using the gauge-including atomic orbital (GIAO) method at the 6-311++g(2d,p) level. A good correlation was observed between calculated 9Be NMR chemical shifts when compared to experimental values in polar protic solvents, less so for the values recorded in polar aprotic solvents. A number of alternative complex structures were modeled, resulting in an improvement in experimental versus computational 9Be NMR chemical shifts, suggesting that in some cases full encapsulation on the beryllium atom was not occurring. Several of the synthesized complexes gave rise to unexpected fluorescence, and inspection of the calculated molecular orbital diagrams associated with the electronic transitions suggested that the rigidity imparted by the locking of certain conformations upon BeII coordination allowed delocalization across adjacent aligned aromatic rings bridged by BeII.
Shaffer, Karl J.,Davidson, Ross J.,Burrell, Anthony K.,McCleskey, T. Mark,Plieger, Paul G.
p. 3969 - 3975
(2013/05/09)

Synthesis, structural characterization, thermal studies, catalytic efficiency and antimicrobial activity of some M(II) complexes with ONO tridentate Schiff base N-salicylidene-o-aminophenol (saphH2)
The reactions of acetate salts of M(II) (M = Mn, Co, Ni, Cu and Zn) with N-salicylidene-o-aminophenol (saphH2) in ethyl alcohol afforded new four coordinated complexes with the general formula [M(II)(saph) (H2O)]. The complexes have been fully characterized by microanalysis, molar conductance, magnetic susceptibility, 1H NMR, IR, UV-Vis, ESR, mass spectra and thermogravimetric analysis (TGA). The experimental data have been shown that all complexes are mononuclear with the M(II) being coordinated by a dianionic tridentate Schiff base ligand, through the deprotonated two enolic oxygen and the azomethine nitrogen atoms. UV-Vis spectra and magnetic moments have been suggested square planar stereochemistry for Co(II) and Cu(II) complexes, and tetrahedral geometry has been suggested for Mn(II), Ni(II) and Zn(II) complexes. The new complexes have been tested for their abilities to catalyze aerial oxidation of benzaldehyde to benzoic acid. Finally, in view of the biological activity, antibacterial and antifungal tests of the ligand and its complexes have been carried out and the results were compared with some known antibiotics.
Abdel Aziz, Ayman A.,Salem, Abdel Naby M.,Sayed, Mostafa A.,Aboaly, Mohamed M.
experimental part
p. 130 - 138
(2012/03/22)

Ni nanoparticles: Mild and efficient catalyst for the chemoselective synthesis of 2-arylbenzimidazoles, 2-arylbenzothiazoles, and azomethines
(Chemical Equation Presented) A new and efficient method has been developed for the synthesis of biologically significant 2-arylbenzimidazoles, 2-arylbenzothiazoles, and azomethines using recyclable and inexpensive polyvinyl pyrrolidone (PVP)-stabilized Ni nanoparticles in ethylene glycol at room temperature in excellent yields. Copyright Taylor & Francis Group, LLC.
Khurana, Jitender M.,Sneha,Vij, Kanika
experimental part
p. 2606 - 2616
(2012/08/08)

DETERGENTS OR CLEANING AGENTS CONTAINING A BLEACH-ENHANCING TRANSITION METAL COMPLEX WHICH IS OPTIONALLY PRODUCED IN SITU
The aim of the invention is to improve the cleaning power of detergents and cleaning agents, especially with regard to bleachable stains, while avoiding any damage to the textile treated with said detergents and cleaning agents. For this purpose, a bleach catalyst in the form of a complex of Fe—, Mo—, Mn— and/or W with a ligand having a skeleton of formula (I) is used.
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(2012/10/23)