Dibasic Tridentate Research Articles

Synthesis, characterisation, in vitro antimicrobial, antioxidant and anti-inflammatory activities of diorganotin(IV) complexes derived from salicylaldehyde Schiff bases

A new series of diorganotin(IV) complexes of 4-((2-hydroxybenzylidene)amino)-[1,1′-biphenyl]-3-ol (H2L1), 4-((2-hydroxy-5-nitrobenzylidene)amino)-[1,1′-biphenyl]-3-ol (H2L2), 4-((3-bromo-2-hydroxy-5-nitrobenzylidene)amino)-[1,1′-biphenyl]-3-ol (H2L3) and 4-((3,5-dibromo-2-hydroxybenzylidene)amino)-[1,1′-biphenyl]-3-ol (H2L4) Schiff base ligands with general formula R2SnL (where R = Me, Et, Bu and Ph) were synthesized. Structural aspect of these synthesized compounds have been described with the help of elemental analysis and spectroscopic techniques like FT-IR, UV–Vis, NMR, Mass and fluorescence. Schiff bases coordinated to tin metal as dibasic tridentate ligand through imine nitrogen and two phenolic oxygen atoms forming pentacoordinated complexes. Metal complexes gave low molar conductance value describing their non-electrolytic nature. Thermal decomposition of the complexes resulted in the formation of SnO2 as end product. The in vitro antimicrobial activities have been evaluated against Gram positive bacteria, Gram-negative bacteria and two fungal strains. The screening evaluation showed that organotin(IV) complexes have better antimicrobial activity. The free radical scavenging ability of the compounds was invest by in vitro antioxidant assay involving DPPH radical and was found to be moderately good. The anti-inflammatory activity was done by egg albumin method and percentage inhibition of protein denaturation was calculated. By comparing the biological activities of the synthesized compounds it was found that metal complexes were more potent than the free ligands and compounds 16, 20 were having more potential as drugs.

Synthesis, Electronic Spectral Study and Antifungal Evaluation of Mixed Ligand Complexes of Dibasic Tridentate Schiff Base and Naphthoic Acid with Transition Metal Ions

Transition metal complexes of Mn(II), Co(II) and Cu(II) with dibasic tridentate Schiff base derived from the condensation of thiosemi-carbazide with acetoacetanilide as primary ligand and 1-hydroxy-2-naphthoic acid as co-ligand have been synthesized. The mixed ligand complexes of the above mentioned metal ions were characterized by analytical, magnetic and electronic spectral study. The transition metal complexes were also evaluated for antifungal activity against Drechslera tetramera, Fusarium oxysporum and Aternaria alternata at different concentrations.

Cr(III), Mn(II), Co(II), Ni(II) and Cu(II) complexes of 7-((1H-benzo[d]imidazol-2-yl)diazenyl)-5-nitroquinolin-8-ol.synthesis, thermal, spectral, electrical measurements, molecular modeling and biological activity

The titled new azo-compound namely, 7-((1H-benzo [d]imidazol-2-yl) diazenyl)-5-nitroquinolin-8-ol, and its Cr(III), Mn(II), Co(II), Ni(II) and Cu(II) complexes have been designed and prepared. These compounds were characterized by spectral and analytical techniques. The IR spectral data suggested that the free compound behaves as dibasic tridentate via deprotonated OH, NH and N atom of azo group. Cr(III) and Ni(II) complexes have octahedral, Mn(II) and Cu(II) complexes have square planar while Co(II)complex has tetrahedral geometry. The molecular parameters were calculated to secure the geometry of the complexes. The thermal studies have been undertaken as an additional information to confirm the structure of the studied complexes. The kinetic and thermodynamic parameters of the thermal decomposition steps were evaluated using three mechanistic equations at different heating rates (5–15 °C/min). The activities of the ligand and its complexes have been tested as antimicrobial strains. All complexes have higher biological activity than free ligand. The solid state electrical conductivity of the metal complexes was measured.

Synthesis, Spectral Characterization and Crystal Structures of Dioxidomolybdenum(VI) Complexes Derived from Nicotinoylhydrazones

Cis-dioxidomolybdenum(VI) complexes [MoO2L1(DMSO)] (1), [MoO2L2(H2O)]·DMF (2) and [MoO2L3(DMF)] (3) were synthesized by solution based reactions of aroylhydrazones (H2L1 = 5-chloro-2-hydroxybenzaldehyde nicotinoylhydrazone, H2L2 = 2-hydroxy-5-iodobenzaldehyde nicotinoylhydrazone and H2L3 = 3,5-dichloro-2-hydroxybenzaldehyde nicotinoylhydrazone) with bis(acetylacetonato)dioxidomolybdenum(VI) complex, [MoO2(acac)2] in presence of DMSO or DMF. The synthesized aroylhydrazones and their molybdenum complexes were characterized by elemental analysis, spectroscopic techniques (FT-IR, UV–Vis, 1H NMR) and conductivity measurements. Finally the three dimensional structures of the complexes were confirmed by single crystal X-ray diffraction studies. Crystal structures of 1, 2 and 3 were solved by direct methods and refined with full-matrix least-squares calculations using the SHELXS97 and SHELXL2014 software programs respectively. Complex 1 got crystallized in monoclinic space group, P21/c with Z = 4, whereas complexes 2 and 3 in triclinic space group, P $$\overline {1}$$ with Z = 2. The ligands, H2L1−3 showed coordination to the metal ion in a dibasic tridentate manner through deprotonated phenolate oxygen, azomethine nitrogen and enolate oxygen.

A novel biocompatible NiII tethered moiety as a glucose uptake agent and a hit against methicillin-resistant Staphylococcus aureus

In the efforts to develop a biocompatible transition metal complex as a drug alike for some of the prevailing non-communicable diseases (NCDs) and communicable diseases (CDs), a novel binuclear NiII compound [{NiII(hpdbal-sbdt)}2] (2) has been synthesized by the reaction of Ni(OAc)2.4H2O and H2hpdbal-sbdt (1) [1 is a dibasic tridentate ONS2− donor Schiff base ligand obtained by the condensation of 2-hydroxy-5-(phenyldiazenyl)benzaldehyde (Hhpdbal) and S-benzyldithiocarbazate (Hsbdt)]. Both ligand 1 and compound 2 were structurally characterized in the solid and solution state using various spectroscopic techniques like ATIR, 1H NMR, 13C NMR, TGA, FESEM, EDS and CHNS analysis. The antidiabetic activity of H2hpdbal-sbdt (1) and [{NiII(hpdbal-sbdt)}2] (2) were assessed using 2-NBDG uptake assay. The assay results showed 85% and 95% of fluorescent glucose uptake by insulin resistant HePG2 cells treated with compounds 1 and 2 respectively. The 2-NBDG uptake by the cells treated with the compound 2 was observed to be comparable to the standard antidiabetic drug metformin. Compounds 1 and 2 were also tested against five bacterial and two fungi strains in order to evaluate pathogen killing activity. Compound 2 showed significant inhibitory action towards the methicillin-resistant Staphylococcus aureus (MRSA) strain with an MIC value of 2 μg/mL whereas the ligand 1 was found to be inactive. Furthermore, the interactive nature of compound 2 with a model serum carrier protein bovine serum albumin (BSA) was studied using a multi-spectroscopic approach which provided an insight into the nature and extent of binding, conformational changes and the quenching of amino acid residues of the protein.

Trinuclear Dioxidomolybdenum(VI) Complexes of Tritopic Phloroglucinol‐Based Ligands and Their Catalytic Applications for the Selective Epoxidation of Olefins

Four trinuclear dioxidomolybdenum(VI) complexes, [{MoVIO2(H2O)}3ptk(bhz)3] (1), [{MoVIO2(H2O)}3ptk(fah)3] (2), [{MoVIO2(H2O)}3ptk(inh)3] (3), and [{MoVIO2(H2O)}3ptk(nah)3] (4), based on the tritopic central 2,4,6‐triacetylphloroglucinol (H3ptk) ligands H6ptk(bhz)3 (I), H6ptk(fah)3 (II), H6ptk(inh)3 (III) and H6ptk(nah)3 (IV) (Hbhz = benzoylhydrazide, Hfah = 2‐furanoylhydrazide, Hinh = isonicotinoylhydrazide and Hnah = nicotinoylhydrazide), respectively, are presented. All of the synthesized ligands, as well as their complexes, have been characterized by elemental, thermal, and electrochemical analyses, spectroscopic techniques (FTIR, UV/Vis, 1H and 13C NMR), and single‐crystal X‐ray studies of [{MoVIO2(H2O)}{MoVIO2(MeOH)}2ptk(bhz)3]·2H2O·1.25MeOH (1a) and [{MoVIO2(EtOH)}3ptk(fah)3]·3EtOH (2a). Each pocket of the ligands coordinates in a dibasic tridentate fashion through two oxygen atoms and one nitrogen atom to each metal center. Due to the presence of tridentate binding pockets in the ligands, each metal center conserves its octahedral structure by coordinating with water molecules in the synthesized complexes or by other solvent(s) in the crystal structures. These complexes were evaluated for the epoxidation of terminal and internal alkenes in the presence of H2O2 using NaHCO3 as a promoter. Under the optimized reaction conditions, all alkenes were converted to the corresponding epoxides selectively in good yield and high turnover number.

Biological evaluation of new organoruthenium(II) metallates containing 3-acetyl-8-methoxy-2H-chromen-2-one appended CNS donor Schiff bases

A series of four new, cyclometallated ruthenium (II) complexes was synthesized from 3-acetyl-8-methoxy-2H-chromen-2-one functionalized 4(N)- substituted thiosemicarbazones and characterized through various spectral and analytical methods. The molecular structures of the complexes 1, 2 and 4 were determined by single-crystal X-ray diffraction analysis, which confirmed that the complexes possess a distorted octahedral geometry with the ligands coordinating in a dibasic tridentate fashion via C, N and S atoms. DNA [Calf Thymus DNA (CT-DNA)] and protein [Bovine Serum Albumin (BSA) and Human Serum Albumin (HSA)] binding studies indicated an intercalative mode of binding with DNA and static quenching mechanism with proteins. The compounds cleaved plasmid DNA (pBR322) without application of any external agent and acted well as free radical scavengers. A good spectrum of antimicrobial activity was observed against four bacterial and five fungal pathogens. Two cancerous cell lines, MCF-7 (human breast cancer) and A549 (human lung carcinoma) were employed to test their in vitro cytotoxic activity using MTT assay. The complexes (1–4) showed better activity with lower IC50 values over cisplatin. Further non toxic nature of the complexes have been examined with human normal keratinocyte cell line HaCaT. Further, the results of Lactate dehydrogenase release (LDH) and Nitric Oxide (NO) release supported the cytotoxic nature of the compounds. The results of all the biological studies carried out implied that the complex 3 bearing an ethyl substituent was observed to be the best.

Synthesis, characterization, molecular modeling, antioxidant and microbial properties of some Titanium(IV) complexes of schiff bases

The titanium(IV) complexes of Schiff bases derived from aroylhydrazine e.g. benzoylhydrazine, salicyloylhydrazine, nicotinic acid hydrazide with aldehyde or ketone are reported and characterized based on UV–vis spectroscopy, (Infra-red) IR spectra, 1H NMR spectra, mass spectra, magnetic susceptibility and molar conductance measurements. Complexes are found to possess 1:2 (metal:ligand) stoichiometry. The prepared ligands were act as dibasic tridentate ligands. On the basis of experimental evidences octahedral geometry has been proposed for prepared complexes. Geometry was confirmed by the optimized structure obtained from computational study. The synthesized ligands, in comparison to their titanium(IV) complexes, were also screened for their microbial and antioxidant properties.

Synthesis, structural studies and catalytic activity of a series of dioxidomolybdenum(VI)-thiosemicarbazone complexes

Reaction of the thiosemicarbazone ligands, [4-(p-bromophenyl)thiosemicarbazone of salicylaldehyde (H2L1), 4-(p-X-phenyl)thiosemicarbazone of o-vanillin {X = F (H2L2), X = Cl (H2L3) and X = OMe (H2L4)}, 4-(p-bromophenyl)thiosemicarbazone of 5-bromosalicylaldehyde (H2L5), and 4-(p-chlorophenyl)thiosemicarbazone of o-hydroxynaphthaldehyde (H2L6)] with [MoO2(acac)2] afforded a series of new oxidomolybdenum(VI) complexes [Mo(VI)O2L1–6(solv)] (1–6) {where solv (solvent) = DMSO (1, 3, 5 & 6) and H2O (2 & 4)}. The molecular structures of 2 and 3 were determined by X-ray crystallography, demonstrating the dibasic tridentate behavior of ligands. The cyclic voltammogram pattern is similar for 1–6, which includes two irreversible reduction processes within the potential window −0.71 to −0.66 V and −0.92 to −0.85 V corresponding to the metal centered reduction from Mo(VI)/Mo(V) and Mo(V)/Mo(IV) respectively. Catalytic potential of 1–6 was tested for the oxidation of styrene and cyclohexene. The effect of various parameters such as the amount of catalyst, oxidant, NaHCO3, and solvent was checked to optimize the conditions for the best performance of the catalyst. 100% product selectivity for the formation of cyclohexene oxide from cyclohexene and ∼98–99% product selectivity for the oxidation of styrene to styrene oxide was observed.

New transition metal complexes of 2,4-dihydroxybenzaldehyde benzoylhydrazone Schiff base (H2dhbh): Synthesis, spectroscopic characterization, DNA binding/cleavage and antioxidant activity

New complexes [VO2(Hdhbh)] (1), [VO(phen)(dhbh)].1.5H2O (2), [Zn(Hdhbh)2] (3), [MoO2(dhbh)(D)] (D = H2O (4) or MeOH (5)), [Ru(PPh3)(dhbh)Cl(H2O)] (6), and [Pd(Hdhbh)Cl]·H2O (7) (H2dhbh = Schiff base derived from 2,4-dihydroxybenzaldehyde and benzoylhydrazone) have been isolated and characterized by IR, 1H NMR, Mass, UV–Visible and ESR spectroscopy. They were also investigated by cyclic voltammetry, thermal and magnetic measurements and the structure of complex cis-[MoO2(dhbh)(H2O)] (4) was solved by X-ray crystallography. Analytical data showed that H2dhbh behaves as monobasic/or dibasic tridentate ligand via phenolate O, azomethine N and amide O/or deprotonated amide O atoms. Antioxidant activity of the complexes has been evaluated against DPPH (2,2-diphenyl-1-picrylhydrazyl) radical and it has been found that oxovandium (IV) complex (2) displays the highest radical scavenging potency comparable to ascorbic acid as a standard antioxidant. The DNA binding properties of the ligand and its complexes have been investigated by electronic spectroscopy together with DNA cleavage by gel electrophoresis whose results showed also that vanadium (IV) complex (2) has a significant oxidative cleavage among other complexes.

Synthesis and Antifungal Study of Mixed Ligand Complex of Ni(II) with Dibasic Tridentate Schiff Base as Primary and Naphthoic Acid as Co-ligand

Synthesis and Antifungal Study of Mixed Ligand Complex of Ni(II) with Dibasic Tridentate Schiff Base as Primary and Naphthoic Acid as Co-ligand

Dioxidomolybdenum(VI) complexes bearing sterically constrained aroylazine ligands: Synthesis, structural investigation and catalytic evaluation

Seven new dioxidomolybdenum(VI) complexes [MoO2L1(X)].X (1) and [MoO2L2–7(X)] (2–7) [Where X=EtOH in case of 1 and 5 and X=DMSO in case of 2–4 and 6, 7] of aroylazines containing a bulky 3-hydroxy-2-naphthoic substituent, were isolated and structurally characterized. The aroylazine ligands H2L1–7 were derived from the condensation of 3-hydroxy-2-naphthoic acid hydrazide with several substituted aromatic aldehydes/ketones. All the synthesized ligands and metal complexes were successfully characterized by elemental analysis, IR, UV–Vis and NMR spectroscopy. X-ray structures of 1–6 revealed that the ligands coordinate to the metal center as a dibasic tridentate ligand. Cyclic voltammetry of the complexes shows two irreversible reductive responses within the potential window −0.50 to −1.36V, due to MoVI/MoV and MoV/MoIV processes. The synthesized complexes 1–7 were used as catalysts for the oxidation of benzoin, and for the oxidative bromination of salicylaldehyde, as a functional mimic of haloperoxidase. It was found that the percentage of conversion increased significantly in the presence of catalysts 1–7 which contained bulky substituents, and showed high percentage of conversion (>90%) with high turnover frequency (>1100h−1) than previously reported catalysts. Benzil, benzoic acid and benzaldehyde-dimethylacetal were formed selectively for the oxidation of benzoin. Formation of 5-bromosalicylaldehyde and 3,5-dibromosalicylaldehyde took place during the oxidative bromination of salicylaldehyde in presence of H2O2 asan oxidant and therefore 1–7 act as functional models of vanadium dependent haloperoxidases.

Bis{cis‐[MoO2]} Complexes of 4,6‐Diacetyl Resorcinol Bis(hydrazone)and Their Catalytic Application for the Three Components Dynamic Covalent Assembly via Hantzsch Reaction

AbstractFour binuclear dioxidomolybdenum(VI) complexes with Schiff base ligands, H4dar(bhz)2 (I), H4dar(inh)2 (II), H4dar(nah)2 (III) and H4dar(fah)2 (IV) (H2dar=4,6‐diacetyl resorcinol and Hbhz=benzoylhydrazide, Hinh=isonicotinoylhydrazide, Hnah=nicotinoylhydrazide, and Hfah=2‐furoylhydrazide) have been prepared by the reaction of ligand with [MoVIO2(acac)2] (Hacac=acetylacetone) in 1:2 ratio in methanol. Isolated complexes[(MoVIO2)2{dar(bhz)2}(H2O)2] (1), [(MoVIO2)2{dar(inh)2}(H2O)2] (2), [(MoVIO2)2{dar(nah)2}(H2O)2] (3) and [(MoVIO2)2{dar(fah)2}(H2O)2] (4) are characterized by elemental (CHN) analysis, spectral (FT‐IR, UV‐vis, 1H and 13C NMR) and thermogravimetric analysis. Single crystal X‐ray diffraction analysis of complexes 1, 2 and 4 confirms their binuclear structure and distorted octahedral geometry around each molybdenum where ligands behave as bis(dibasic tridentate) coordinating through phenolic oxygen, azomethine nitrogen and enolic oxygen atoms of each unit. These complexes have successfully been used as catalyst precursors in solvent as well as solvent free conditions for the one‐pot three components (ethylacetoacetate, benzaldehyde and ammonium acetate) dynamic covalent assembly, via Hantzsch reaction using hydrogen peroxide as an oxidant.

Synthesis, characterization and bioactivity ¬¬¬¬Zn2+, Cu2+, Ni2+, Co2+, Mn2+, Fe3+, Ru3+, VO2+ and UO22+ complexes of 2-hydroxy-5-((4-nitrophenyl)diazenyl)benzylidene)-2-(p-tolyl- amino)acetohydrazide

Novel azo-acetohydrazide complexes of Zn2+, Cu2+, Ni2+, Co2+, Mn2+, Fe3+, Ru3+, VO2+ and UO22+ with 2-hydroxy-5-((4-nitrophenyl)diazenyl)benzylidene)-2-(p-tolylamino)acetohydrazide have been prepared. All the compounds were analytically and spectroscopically characterized by various techniques. The data of molar conductance indicated the prepared complexes are nonelectrolyte in nature except complexes (10) and (11). The spectroscopic data point out that the behavior of ligand towards metal ions are neutral or monobasic bidentate, and dibasic tridentate ligand linked to the metal ions through oxygen atom of ketonic or enolic carbonyl group, azomethine nitrogen atom and/or deprotonated phenolic group forming either octahedral or tetragonally distorted octahedral geometry. X-ray powder diffraction analysis of complexes (2) and (3) indicate that the complexes are crystalline in nature and have monoclinic structures. The microbicides activities of all compounds evaluated by well diffusion method versus Escherichia coli and Aspergillus niger at different concentration. The bioactivities data elucidated that as the concentration of the tested solutions increases the activities increase. KEY WORDS: Azo-acetohydrazide, Azo-hydrazone, Metal complexes, Bioactivity, X-ray diffraction analysis Bull. Chem. Soc. Ethiop. 2017, 31(1), 75-91.DOI: http://dx.doi.org/10.4314/bcse.v31i1.7

Preparation, characterization and Microbicide activities of N'-((3-(hydroxyimino)butan-2-ylidene)-2-(phenylamino)acetohydrazide and its complexes

A series of fourteen metal complexes synthesized by reaction a new acetohydrazide oxime ligand with metal ions (CuII, NiII, CoII, MnII, FeIII, ZnII, RuIII, UO2VI and VO2VI). The Ligand, N''-((3-(hydroxyimino)butan-2-ylidene)-2-(phenylamino)acetohydrazide was prepared by refluxing equimolar amount of phenyl amino acetohydrazide with 2,3-butanedione monoxime. The synthesized compounds were characterized using elemental and thermal analyses, NMR, IR, U.V spectroscopy, magnetic and conductance measurements. The results demonstrated that complexes (2), (3), (5-7) and (10-12) were formed in 1L:1M molar ratio, while complexes (4), (8), (9), (13) and (14) were found to afford M2L formulae. The ligand acted either as a neutral bidentate, neutral, monobasic or dibasic tridentate and dibasic tetradentate ligand chelated to the metal ions via nitrogen atoms of aceto-amino and azomethine groups, carbonyl oxygen atom in its enolic or ketonic form and/or protonated or deprotonated oximino nitrogen atom, adopting aoctahedral, tetrahedral or square planar geometry around metal ions. The antimicrobial activity of the ligand as well as the metal complexes was examined using Amphotericin B and Amoxicillin as drug-standards against Aspergillum niger (A.niger) and Escherichia coli (E. coli) respectively. The ligand demonstrates a high cytotoxicity against A. niger whereas it recorded a moderate activity against E. coli. It is interestingly found that zinc(II) complex (6), copper(II) complexes (8, 10) recorded higher activities than the Amphotericin B drug with 122%, 116% and 111.1% percentages respectively against A. niger zinc(II) complex (6) was also the most sensitive complex against E. coli with (94.1 %) comparable to Amoxicillin.

Three novel Ni(II), VO(II) and Cr(III) mononuclear complexes encompassing potentially tridentate imine ligand: Synthesis, structural characterization, DNA interaction, antimicrobial evaluation and anticancer activity

Three novel Cr(III),VO(II) and Ni(II) imine complexes derived from the condensation of 2‐aminophenol (AP) with 2‐hydroxynaphthaldehyde (HN) were synthesized. The prepared HNAP imine ligand and its complexes were investigated via various physicochemical tools. The results suggest that the parent ligand behaves as a dibasic tridentate ONO ligand, when coordinated to Cr(III) in octahedral and to Ni(II) in tetrahedral geometry. In the case of VO(II), it coordinates in distorted square pyramidal geometry. Also, the prepared compounds were screened for their antimicrobial activities against pathogenic bacteria, Escherichia coli (−ve), Bacillus subtilis (+ve) and Staphylococcus aureus (+ve), and some types of fungi, Aspergillus niger, Candida glabrata and Trichophyton rubrum. The results indicate that the complexes show a stronger antimicrobial efficiency compared to the pro‐ligand. The interaction of the prepared complexes with calf thymus DNA was investigated using spectral, viscosity and gel electrophoresis measurements. The obtained results clearly demonstrate that the binding affinity with calf thymus DNA follows the order HNAPCr > HNAPV > HNAPNi. The cytotoxic activity of the prepared compounds on human colon carcinoma cells (HCT‐116 cell line), hepatic cellular carcinoma cells (HepG‐2cell line) and breast carcinoma cells (MCF‐7cell line) was examined. From these results it is found that the investigated complexes have potent cytotoxicity against growth of carcinoma cells compared to the corresponding imine pro‐ligand.

Versatile Reactivity and Theoretical Evaluation of Mono- and Dinuclear Oxidovanadium(V) Compounds of Aroylazines: Electrogeneration of Mixed-Valence Divanadium(IV,V) Complexes.

The substituted hydrazones H2L(1-4) (L(1-4) = dibasic tridentate ONO(2-) donor ligands) obtained by the condensation of 2-hydroxy-1-naphthaldehyde and 2-aminobenzoylhydrazine (H2hnal-abhz) (H2L(1)) , 2-hydroxy-1-naphthaldehyde and 2-hydroxybenzoylhydrazine (H2hnal-hbhz) (H2L(2)), 2-hydroxy-1-acetonaphthone and benzoylhydrazine (H2han-bhz) (H2L(3)), or 2-hydroxy-1-acetonaphthone and 2-aminobenzoylhydrazine (H2han-abhz) (H2L(4)) are prepared and characterized. Reaction of ammonium vanadate with the appropriate H2L(1-4) results in the formation of oxidoethoxidovanadium(V) [V(V)O(OEt)(L(1-4))] (1-4) complexes. All compounds are characterized in the solid state and in solution by spectroscopic techniques (IR, UV-vis, (1)H, (13)C, and (51)V NMR, and electrospray ionization mass spectrometry). Single-crystal X-ray diffraction analysis of 1, 3, and 4 confirms the coordination of the corresponding ligands in the dianionic (ONO(2-)) enolate tautomeric form. In solution, the structurally characterized [V(V)O(OEt)(L)] compounds transform into the monooxido-bridged divanadium(V,V) [(V(V)OL)2-μ-O] complexes, with the processes being studied by IR and (1)H, (13)C, and (51)V NMR. The density functional theory (DFT) calculated Gibbs free energy of reaction 2[V(V)O(OEt)(L(4))] + H2O ⇆ [(V(V)OL(4))2-μ-O] + 2EtOH is only 2-3 kcal mol(-1), indicating that the dinuclear complexes may form in a significant amount. The electrochemical behavior of the complexes is investigated by cyclic voltammetry, with the V(V)-V(IV) E1/2(red) values being in the range 0.27-0.44 V (vs SCE). Upon controlled potential electrolysis, the corresponding (L)(O)V(IV)-O-V(V)(O)(L) mixed-valence species are obtained upon partial reduction of the [(V(V)OL)2-μ-O] complexes formed in solution, and some spectroscopic characteristics of these dinuclear mixed-valence complexes are investigated using DFT calculations and by electron paramagnetic resonance (EPR), with the formation of V(IV)-O-V(V) species being confirmed by the observation of a 15-line pattern in the EPR spectra at room temperature.

Synthesis, Characterization and Biological Activity of Zn(II) Complexes with Dibasic Tridentate ONS-Donor Ligand

Synthesis, Characterization and Biological Activity of Zn(II) Complexes with Dibasic Tridentate ONS-Donor Ligand

Studies on mixed ligand complexes of iron (III) with dibasic tridentate schiff bases as primary and naphthoic acids as Co-Ligands

Studies on mixed ligand complexes of iron (III) with dibasic tridentate schiff bases as primary and naphthoic acids as Co-Ligands

Nickel complexes of Schiff bases derived from mono/diketone with anthranilic acid: Synthesis, characterization and microbial evaluation

The nickel(II) complexes of the dibasic tridentate Schiff bases viz. Sal-AnthraH2, HNP-AnthraH2, HAP-AnthraH2, HPP-AnthraH2, Acac-AnthraH2, Etac-AnthraH2, and Bzac-AnthraH2, have been synthesized and characterized by IR, 1H NMR, mass and electronic spectra, and magnetic and conductance studies. On the basis of analytical data, four-coordinate geometry was proposed for the prepared nickel(II) complexes. The complexes have been found to possess 1:1 stoichiometry. The bio-efficacy of the prepared complexes has been examined against the growth of bacteria and fungi in vitro to evaluate their antimicrobial potential.