- Installation of internal electric fields by non-redox active cations in transition metal complexes
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Local electric fields contribute to the high selectivity and catalytic activity in enzyme active sites and confined reaction centers in zeolites by modifying the relative energy of transition states, intermediates and/or products. Proximal charged functio
- Kang, Kevin,Fuller, Jack,Reath, Alexander H.,Ziller, Joseph W.,Alexandrova, Anastassia N.,Yang, Jenny Y.
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- Synthesis of Some Schiff Bases
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Six new Schiff bases having the ONNO donor system have been synthesized from the condensation of biacetyl monooxime, benzil, o-vanillin, 9,10-phenanthrenequinone, ethanolamine, 1,3-diaminopropan-2-ol, and ethylenediamine.Their characterization has been ba
- Ghose, Bhupendra N.
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- Selective Metal-Ligand Bond-Breaking Driven by Weak Intermolecular Interactions: From Metamagnetic Mn(III)-Monomer to Hexacyanoferrate(II)-Bridged Metamagnetic Mn2Fe Trimer
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Metal-ligand coordination interactions are usually much stronger than weak intermolecular interactions. Nevertheless, here, we show experimental evidence and theoretical confirmation of a very rare example where metal-ligand bonds dissociate in an irreversible way, helped by a large number of weak intermolecular interactions that surpass the energy of the metal-ligand bond. Thus, we describe the design and synthesis of trinuclear Mn2Fe complex {[Mn(L)(H2O)]2Fe(CN)6},2- starting from a mononuclear Mn(III)-Schiff base complex: [Mn(L)(H2O)Cl] (1) and [Fe(CN)6]4- anions. This reaction implies the dissociation of Mn(III)-Cl coordination bonds and the formation of Mn(III)-NC bonds with the help of several intermolecular interactions. Here, we present the synthesis, crystal structure, and magnetic characterization of the monomeric Mn(III) complex [Mn(L)(H2O)Cl] (1) and of compound (H3O)[Mn(L)(H2O)2]{[Mn(L)(H2O)]2Fe(CN)6}·4H2O (2) (H2L = 2,2′-((1E,1′E)-(ethane-1,2-diylbis(azaneylylidene))bis(methaneylylidene))bis(4-methoxyphenol)). Complex 1 is a monomer where the Schiff base ligand (L) is coordinated to the four equatorial positions of the Mn(III) center with a H2O molecule and a Cl- ion at the axial sites and the monomeric units are assembled by π-πand hydrogen-bonding interactions to build supramolecular dimers. The combination of [Fe(CN)6]4- with complex 1 leads to the formation of linear Mn-NC-Fe-CN-Mn trimers where two trans cyano groups of the [Fe(CN)6]4- anion replace the labile chloride from the coordination sphere of two [Mn(L)(H2O)Cl] complexes, giving rise to the linear anionic {[Mn(L)(H2O)]2Fe(CN)6}2- trimer. This Mn2Fe trimer crystallizes with an oxonium cation and a mononuclear [Mn(L)(H2O)2]+ cation, closely related to the precursor neutral complex [Mn(L)(H2O)Cl]. In compound 2, the Mn2Fe trimers are assembled by several hydrogen-bonding and π-πinteractions to frame an extended structure similar to that of complex 1. Density functional theoretical (DFT) calculations at the PBE1PBE-D3/def2-TZVP level show that the bond dissociation energy (-29.3 kcal/mol) for the Mn(III)-Cl bond is smaller than the summation of all the weak intermolecular interactions (-30.1 kcal/mol). Variable-temperature magnetic studies imply the existence of weak intermolecular antiferromagnetic couplings in both compounds, which can be can cancelled with a critical field of ca. 2.0 and 2.5 T at 2 K for compounds 1 and 2, respectively. The magnetic properties of compound 1 have been fit with a simple S = 2 monomer with g = 1.959, a weak zero-field splitting (|D| = 1.23 cm-1), and a very weak intermolecular interaction (zJ = -0.03 cm-1). For compound 2, we have used a model with an S = 2 monomer with ZFS plus an S = 2 antiferromagnetically coupled dimer with g = 2.009, |D| = 1.21 cm-1, and J = -0.42 cm-1. The metamagnetic behavior of both compounds is attributed to the weak intermolecular π-πand hydrogen-bonding interactions.
- Goswami, Somen,Singha, Soumen,Saha, Indrajit,Chatterjee, Abhishikta,Dey, Subrata K.,Gómez García, Carlos J.,Frontera, Antonio,Kumar, Sanjay,Saha, Rajat,Saha, Rajat
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- Spin Coupling and Magnetic Anisotropy in 1D Complexes with Manganese(III) Units and Carboxylate Bridges – Synthesis, Analysis, Calculations, and Models
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We report the synthesis, structure and magnetic properties of a series of MnIII complexes with N,N′-ethylenebis(5-methoxysalicylideneiminate) (5MeO-salen) and acetate ligands, namely, [Mn2(5MeO-salen)2(CH3COO)]X
- Cimpoesu, Fanica,Spataru, Tanta,Buta, Cristina Maria,Borrmann, Horst,Moga, Olivia Georgeta,Ferbinteanu, Marilena
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- The functionality of the hybrid systems driven by molecular dimension of the guest copper Schiff-base complexes entrapped in Zeolite-Y
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On encapsulation inside the supercage of zeolite-Y planar Cu (II)–Schiff base complexes show the modified structural, optical and functional properties. The electronic effect of the different substituent groups present in the catalyst plays the decisive r
- Kumari, Susheela,Choudhary, Archana,Ray, Saumi
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- Copper(II) Complexes With Bis-Schiff Bases: Synthesis, Crystal Structures, and Antibacterial Activities
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Reaction of copper perchlorate with the tridentate Schiff bases N,N’-bis(5-methoxysalicylidene)-1,2-ethanediamine (H2L1) and N,N’-bis(5-chlorosalicylidene)-1,3-propanediamine (H2L2), afforded a dinuclear complex
- Zhang, Xin-Li
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- Synthesis, structural characterization, and antibacterial activity of Cu(II) and Zn(II) complexes with tetradentate Schiff bases
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Biological activity study on Cu(II) and Zn(II) complexes is a challenging issue because of the activity of ligands could be modulated by complexation. A new dinuclear copper(II) complex, [Cu2(L1)2]·2CH3OH (1), a
- Liu, Huan-Yu
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- Enhanced catalytic activity and magnetization of encapsulated nickel Schiff-base complexes in zeolite-Y: A correlation with the adopted non-planar geometry
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Square planar Ni(ii)-Schiff base complexes when encapsulated in a supercage of zeolite Y have shown altered optical, magnetic properties and catalytic activities in comparison to their corresponding free states. Different characterization techniques like
- Choudhary, Archana,Das, Bidisa,Ray, Saumi
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- Experimental and theoretical structural determination, spectroscopy and electrochemistry of cobalt (III) Schiff base complexes: immobilization of complexes onto Montmorillonite-K10 nanoclay
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Abstract: The [Co(5-XSalen)(PEt3)(H2O)]ClO4 (where Salen?=?bis(salicylaldehyde)1,2-ethylenediamine and X?=?H, MeO, NO2, Br) complexes were successfully synthesized and characterized by different techniques such
- Kianfar, Ali Hossein,Tavanapour, Sanaz,Eskandari, Kiamars,Azarian, Mohammad Hossein,Mahmood, Wan Ahmad Kamil,Bagheri, Maryam
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- Three novel mononuclear Mn(III)-based magnetic materials with square pyramidal: Versus octahedral geometries
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A series of new manganese schiff base complexes have been prepared and characterized by single crystal X-ray diffraction studies, which showed that all the three complexes are mononuclear; 1 and 2 have square pyramidal geometry, whereas 3 has an octahedra
- Dolai, Malay,Mondal, Abhishake,Liu, Jun-Liang,Ali, Mahammad
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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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- Alteration of electronic effect causes change in rate determining step: Oxovanadium(IV)–salen catalyzed sulfoxidation of phenylmercaptoacetic acids by hydrogen peroxide
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Sulfoxidation of a series of phenylmercaptoacetic acids (PMAA) by hydrogen peroxide catalysed by oxovanadium(IV)–salen complexes has been carried out spectrophotometrically in 100% acetonitrile medium. The formation and involvement of hydroperoxovanadium(
- Kavitha,Subramaniam
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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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- A mononuclear nickel(II) complex and a dinuclear manganese(III) complex derived from N,N'-bis(5-methoxysalicylidene)-1,2-ethanediamine: Synthesis, crystal structures and catalytic epoxidation property
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Synthesis and characterization of a mononuclear nickel(II) complex [NiL] · CH3OH (I) and a dinuclear manganese(III) complex [Mn2L2(NCS)2] (II) derived from the bis-Schiff base N,N'-bis(5-methoxysalicylidene)-1,2
- Wei
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- Oxovanadium(IV)-salen ion catalyzed H2O2 oxidation of tertiary amines to n-oxides- critical role of acetate ion as external axial ligand
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The oxovanadium(IV)-salen ion catalyzed H2O2 oxidation of N,N-dimethylaniline forms N-oxide as the product of the reaction. The reaction follows Michaelis-Menten kinetics and the rate of the reaction is accelerated by electron donating groups present in the substrate as well as in the salen ligand. This peculiar substituent effect is accounted for in terms of rate determining bond formation between peroxo bond of the oxidant and the N-atom of the substrate in the transition state. Trichloroacetic acid (TCA) shifts the λmax value of the oxidant to the red region and catalyzes reaction enormously. The cleavage of N£O bond by vanadium complex leads to moderate yield of the product. But the percentage yield of the product becomes excellent in the presence of TCA.
- Mathavan, Alagarsamy,Ramdass, Arumugam,Ramachandran, Mohanraj,Rajagopal, Seenivasan
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p. 315 - 326
(2015/04/14)
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- Selective H2O2 oxidation of organic sulfides to sulfoxides catalyzed by cobalt(III)-salen ion
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Abstract The catalytic activity of cobalt(III)-salen ion catalyzed selective H2O2 oxidation of organic sulfides to sulfoxides is examined using spectrophotometric technique. The catalytic reaction proceeds through Michaelis-Menten kinetics and the rate of the reaction is highly sensitive to the nature of the substituent present in the substrate as well as in the salen ligand. The product analyses show that the aryl methyl sulfides are selectively oxidized to the corresponding sulfoxides. Based on the spectral and kinetic studies two possible mechanisms have been proposed.
- Mary Imelda Jayaseeli,Ramdass, Arumugam,Rajagopal, Seenivasan
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- Functionalized Salen ligands linking with non-conjugated bridges: unique and colorful aggregation-induced emission, mechanism, and applications
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A series of novel, simple, and colorful Salen ligands (56 samples), salicylaldehyde-based bis-Schiff bases, linking with different non-conjugated alkyl bridges ((CH2)n, n = 2-9, 12; cyclohexyl) and containing different electron-accepting (-NO2, -F, and -Cl), electron-donating (-OMe, -OH, and -NEt2), or sterically hindering (-t-butyl) substituents or a π-extended system (naphthalene ring) have been designed and synthesized. The photophysical properties of these Salen ligands can be well-tuned by the introduction of side functional substituents, π-extended systems, and central N-alkyl chain bridges. It is unusual that they contain a small π-conjugated system but display strong blue, green, and red aggregation-induced emission (AIE) with large Stokes shifts (up to 162 nm) and high fluorescence quantum yields (up to 0.44 and 0.75 in water and in solid, respectively). Combining with their advantages of AIE and good stability and biocompatibility, the Salen ligands can be potentially used in mechanofluorochromism (crystal-defect-induced emission) and living cell imaging. Moreover, the inherent relationships between their chemical structures and AIE properties are studied, which provide unequivocal insights for the design of AIE-active dyes.
- Cheng, Jinghui,Li, Yuanxi,Sun, Rui,Liu, Jiaoyan,Gou, Fei,Zhou, Xiangge,Xiang, Haifeng,Liu, Jin
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supporting information
p. 11099 - 11110
(2015/11/09)
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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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- Facile, efficient, and diastereoselective synthesis of heterohelicene-like molecules
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A concise and efficient route to new and interesting heterohelicene-like molecules has been developed through the one-pot, cascade reductive coupling reaction of o-hydroxydiimines or o-nitrodiimines and triphosgene in the presence of TiCl4/Sm.
- Lin, Wei,Dou, Guo-Lan,Hu, Ming-Hua,Cao, Cheng-Pao,Huang, Zhi-Bin,Shi, Da-Qing
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supporting information
p. 1238 - 1241
(2013/04/23)
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- Cytotoxic dinuclear titanium-salan complexes: Structural and biological characterization
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Controlled hydrolysis of donor-substituted titanium-salan complexes led to the formation of well-defined dinuclear complexes. Structure determination by means of X-ray and NMR-studies revealed the presence of a single μ-oxo bridge and one labile alkoxide
- Immel, Timo A.,Grützke, Martin,Batroff, Ellen,Groth, Ulrich,Huhn, Thomas
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experimental part
p. 68 - 75
(2012/06/15)
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- Salophen and salen oxo vanadium complexes as catalysts of sulfides oxidation with H2O2: Mechanistic insights
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The application of V(V) catalysts in oxidation of sulfides with peroxides offers an efficient procedure, that is compatible with different functional groups, and leads to good yields and selectivities. However, the understanding of the factors affecting the reactivity of different catalysts is still far to be complete. An experimental and theoretical study on a series of V(V) complexes containing variously substituted salen and salophen ligands is reported with the aim to correlate the activity of the catalysts with the electronic character of the vanadium center. The results obtained indicate that steric factors play a major role in determining the outcome of the reaction, often overcoming the electronic effects. Theoretical results suggest the intervention in the catalytic cycle of an hydroperoxo vanadium species.
- Coletti,Galloni,Sartorel,Conte,Floris
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- Synthesis, structural, and insulin-enhancing studies of oxovanadium(iv) complexes
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Oxovanadium(iv) complexes with Schiff bases derived from substituted salicylaldehyde and diamine have been prepared and characterized. 1H NMR and IR spectral data revealed that the symmetrical Schiff base was isolated, and elemental analysis confirmed the
- Nejo, Adeola A.,Kolawole, Gabriel A.,Nejo, Ayorinde O.,Segapelo, Tebogo V.,Muller, Christo J.
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experimental part
p. 1574 - 1579
(2012/02/04)
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- APOPTOTIC AND ANTI-TUMOR ACTIVITIES OF METALLO-SALENS
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The present invention describes the synthesis and biochemical activities of metallo-salen compounds and their derivatives. The Mn(III)-salen and Fe(III)-salen derivatives of the present invention are potential anti-tumor agents, that affect cell viability, induce strong apoptotic activity, cause nuclear condensation, fragmentation, and ultimately death in breast cancer cells MCF-7.
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Page/Page column 5
(2010/01/31)
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- Salen-manganese complexes as catalytic scavengers of hydrogen peroxide and cytoprotective agents: Structure-activity relationship studies
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Synthetic catalytic scavengers of reactive oxygen species (ROS) may have broad clinical applicability. In previous papers, two salen-manganese complexes, EUK-8 and EUK-134, had superoxide dismutase (SOD) and catalase activities and prevented ROS-associate
- Doctrow, Susan R.,Huffman, Karl,Marcus, Catherine Bucay,Tocco, Georges,Malfroy, Evelyne,Adinolfi, Christy A.,Kruk, Henry,Baker, Keith,Lazarowych, Natalie,Mascarenhas, Julius,Malfroy, Bernard
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p. 4549 - 4558
(2007/10/03)
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- New compounds of tetradentate Schiff bases with vanadium(IV) and vanadium(V)
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A new range of potentially tetradentate proligands, H2L, derived from aromatic aldehydes and ketones and aliphatic diamines has been prepared. Their vanadyl(IV) and vanadyl(V) complexes [VO(L)] and [VO(L)]+, and also some adducts [VO(L)→VO(L)]+, have been synthesized. The structures of four selected complexes have been determined and it is shown that these must be a result of both steric and electronic factors that make prediction of conformation and stacking difficult. The adducts [VO(L)→VO(L)]+ have structures that persist in solution in dichloromethane, where they can undergo redox chemistry, but they apparently dissociate into their component complexes in the donor solvent acetonitrile. The Royal Society of Chemistry 1999.
- Choudhary, Nosheen F.,Connelly, Neil G.,Hitchcock, Peter B.,Leigh, G. Jeffery
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p. 4437 - 4446
(2007/10/03)
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