Dibasic Tridentate Research Articles

Synthesis, Spectral, Catalytic, and Bioactivity Studies of Ruthenium(III) Complexes Containing ONO Donor Schiff Base Ligands

New hexa-coordinated ruthenium(III) complexes of the type [RuX(EPh3)2L] (X Cl or Br; E P or As; L deprotonated dibasic tridentate Schiff base ligand) have been synthesized by the reactions of [RuCl3(PPh3)3], [RuCl3(AsPh3)3] or [RuBr3(AsPh3)3] with the appropriate Schiff bases. The Schiff bases were synthesized by the condensation of anthranilic acid with acetyl acetone/salicylaldehyde/o-vanillin/o-hydroxy acetophenone. The complexes were characterized by elemental analyses, spectral (FT-IR, electronic and EPR) electrochemical, and magnetic moment data. Catalytic activity of the complexes in the oxidation of alcohols and the antibacterial activity of the ligands and the complexes have also been studied.

Reactivity of tris(acetylacetonato) iron(III) with tridentate [ONO] donor Schiff base as an access to newer mixed-ligand iron(III) complexes

Two new mixed-ligand iron(III) complexes, [Fe(L n )(acac)(C 2H 5OH)] incorporating coordinated ethanol from the reaction solvent were accessed from the reaction of [Fe(acac) 3] with [ONO] donor dibasic tridentate unsymmetrical Schiff base ligands derived from condensation of 2-hydroxy-1-napthaldehyde with 2-aminophenol (H 2L 1) or 2-aminobenzoic acid (H 2L 2). The thermal study (TGA–DTA) provided evidence for weakly bound ethanol which is readily substituted by neutral N-donor molecule imidazole, benzimidazole or pyridine to produce an array of newer complexes, [Fe(L n )(acac)X] ( n = 1, 2; X = Im, Bim, Py). The compounds were characterized by elemental analyses, FT-IR, UV–vis, solution electrical conductivity, FAB mass, 1H and 13C NMR spectroscopy. Room temperature magnetic susceptibility measurements ( μ eff ∼ 5.8 B.M.) are consistent with spin-free octahedral iron(III) complexes. Cyclic voltammetry of ethanol complexes revealed a quasi-reversible one electron redox response (Δ E p > 100 mV) for the Fe(III)/Fe(II) couple. Low half wave redox potential ( E 1/2) values suggested easy redox susceptibility. The ground state geometries of the ethanol and imidazole complexes have been ascertained to be distorted octahedral by density functional theory using DMol3 program at BLYP/DNP level.

Synthesis, characterization, potentiometry, and antimicrobial studies of transition metal complexes of a tridentate ligand

Complexes of Cu(II), Ni(II), Co(II), Mn(II), and Fe(III) with the tridentate Schiff base, 4-hydroxy-3(1-{2-(benzylideneamino)-phenylimino}-ethyl)-6-methyl-2H-pyran-2-one (HL) derived from 3-acetyl-6-methyl-(2H)-pyran-2,4(3H)-dione (dehydroacetic acid or DHA), o-phenylenediamine, and benzaldehyde were characterized by elemental analysis, molar conductivity, magnetic susceptibility, thermal analysis, X-ray diffraction, IR, 1H-NMR, UV-Vis spectroscopy, and mass spectra. From analytical data, the stiochiometry of the complexes was found to be 1 : 2 (metal : ligand) with octahedral geometry. The molar conductance values suggest nonelectrolytes. X-ray diffraction data suggest monoclinic crystal systems. IR spectral data suggest that the ligand is dibasic tridentate with ONN donors. To investigate the relationship between formation constants of metal complexes and antimicrobial activity, the dissociation constants of Schiff base and stability constants of its binary metal complexes have been determined potentiometrically in THF–water (60 : 40) at 30 ± 1°C and at 0.1 mol L−1 NaClO4 ionic strength. The potentiometric titrations suggest 1 : 1 and 1 : 2 complexation. Antibacterial and antifungal activities in vitro were performed against Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Trichoderma with determination of minimum inhibitory concentrations of ligand and metal complexes. The structure–activity correlation based on stability constants of metal complexes is discussed. Activity enhances upon complexation and the order of activity is in accord with the stability order of metal ions.

Synthesis, characterization, electrochemistry, catalytic, and antimicrobial studies of ruthenium(III) complexes containing ONO donor ligands

A series of ruthenium(III) complexes [RuX(EPh3)2L] (where X = Cl or Br; E = P or As; L = deprotonated dibasic tridentate ligand) were prepared by the reaction of [RuX3(EPh3)3] with Schiff bases (H2L1–H2L4). The ligands were prepared by the condensation of N-4 phenyl/methyl semicarbazide with o-vanillin/o-hydroxy acetophenone. The complexes were characterized by elemental, physico-chemical, and electrochemical methods. Catalytic studies of these complexes for the oxidation of alcohols and aryl–aryl coupling were carried out. Antimicrobial experiments were also carried out.

In Vitro Antibacterial and Antifungal Activities of Some Sulfur–Nitrogen–Oxygen and Oxygen–Nitrogen–Oxygen Donor Bifunctional Tridentate Schiff Bases and Their Boron(III) Complexes

Antimicrobial properties of sulfur, nitrogen, and oxygen bonded organoboron (III) complexes with biologically potent ligands viz., 2-hydroxy-N-phenyl benzamide hydrazine carboxamide(HO∩N∩OH), 2-hydroxy-N-phenyl benzamide hydrazine carbothioamide (HO∩N∩SH), and 2-hydroxy-N-phenyl benzamide hydrazine carbodithioic acid (HO∩N∩SH), have been studied. The unimolar and bimolar reactions of triisopropoxy borane with dibasic tridentate ligands resulted in the formation of colored solids, which have been characterized by elemental analysis, molecular weight determinations, and conductance measurements. The UV, IR, and NMR (1H, 13C, and 11B) spectral studies indicate a tetra-coordinated geometry for the resulting complexes. The ligands and their complexes have been screened for their fungicidal and bactericidal activities, and the results indicate that they exhibit significant antimicrobial properties. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Synthesis, characterization, and biological activity of metal complexes of azohydrazone ligand

A new azohydrazone, 2-hydroxy-N′-2-hydroxy-5-(phenyldiazenyl)benzohydrazide (H3L) and its copper(II), nickel(II), cobalt(II), manganese(II), zinc(II), cadmium(II), mercury(II), vanadyl(II), uranyl(II), iron(III), and ruthenium(III) complexes have been prepared and characterized by elemental and thermal analyses as well as spectroscopic techniques (1H-NMR, IR, UV-Vis, ESR), magnetic, and conductivity measurements. Spectral data showed a neutral bidentate, monobasic bidentate, monobasic tridentate, and dibasic tridentate bonding to metal ions via the carbonyl oxygen in ketonic or enolic form, azomethine nitrogen, and/or deprotonated phenolic hydroxyl oxygen. ESR spectra of solid vanadyl(II) complex (2), copper(II) complexes (3–5), and (7) and manganese(II) complex (10) at room temperature show isotropic spectra, while copper(II) complex (6) shows axial symmetry with covalent character. Biological results show that the ligand is biologically inactive but the complexes exhibit mild effect on Gram positive bacteria (Bacillus subtilis), some octahedral complexes exhibit moderate effect on Gram negative bacteria (Escherichia coli), and VO(II), Cd(II), UO(II), and Hg(II) complexes show higher effect on Fungus (Aspergillus niger). When compared to previous results, metal complexes of this hydrazone have a mild effect on microorganisms due to the presence of the azo group.

Syntheses and characterization of coordination compounds of N-(2-mercaptoethyl)-4-(3' -carboxy-2' -hydroxyphenyl)·2·azetidinone

A dioxane solution of N-(2-mercaptoethyl)-3-carboxy-2-hydroxybenzylideneimine, LH 3 (I) on reacting with chloroacetyl chloride in the presence of triethylamine, undergoes cyclization to form N-(2-mercaptoethyl)-4-(3'-carboxy-2'-hydroxyphenyl)-2-azetidinone, L'H 3 (II). A MeOH solution of L'H 3 reacts with Mn, Co II , Ni II , Cu II , II , II , Zr IV , MoO 2 2+ and UO 2 2+ ions to form the complexes [M(L'H).MeOH] 2 (where M = Mn, Co II or Ni II ), [Cu(L'H)] 2 , [M'(L'H)] (where M' = II , Cd, MoO 2 2+ or UO 2 2+ ) and [Zr(OH) 2 (L'H)] 2 . The compounds have been characterized on the basis of elemental analyses, molar conductance, molecular weight, spectral (IR, UV-Visible) studies and magnetic susceptibility measurements. L'H 3 behaves as a dibasic tridentate OON donor ligand in [Cu(L'H)] 2 , while it acts as a dibasic tetradentate OONS donor ligand in rest of the compounds. The complexes [M(L'H).MeOH] 2 (where M = Mn, Co II or Ni II ), [Cu(L'H)] 2 and [Zr(OH) 2 (L'H)] 2 are dimers, and the complexes [M'(L'H)] (where M' = Zn, Cd, MoO 2 2+ or UO 2 2+ ) are monomers. The dimeric complex [Cu(L'H)] 2 exhibits subnormal magnetic moment and is involved in antiferromagnetic exchange, while all other complexes are magnetically dilute. The octahedral structure for Mn II , Co, Ni II. MoO 2 2+ and UO 2 2+ complexes, square planar structure for Cu II complex, tetrahedral structure for Zn and Cd complexes, and pentagonal bipyramidal structure for Zr IV complex have been suggested.

2-(2-Hydroxy)phenylazo derivatives of some 1,3-dicarbonyl compounds and their metal complexes

2-Hydroxyphenylazo derivatives of three 1,3-dicarbonyl compounds (acetylacetone, methylacetoacetate and acetoacetanilide) have been synthesized and characterised. Analytical, IR, 1 H NMR and mass spectral data indicate that the compounds exist in the intramolecularly hydrogen bonded keto-hydrazone form. Dibasic tridentate coordination of these compounds in their [M 2 L 2 ] complexes (M = Ni II , Cu II and Zn) has been established on the basis of analytical and spectral data.

Dinuclear Oxidovanadium(IV) and Dioxidovanadium(V) Complexes of 5,5′‐Methylenebis(dibasic tridentate) Ligands: Synthesis, Spectral Characterisation, Reactivity, and Catalytic and Antiamoebic Activities

AbstractThe synthesis of dinuclear oxidovanadium(IV) and dioxidovanadium(V) complexes of two hydrazones [CH2(H2sal‐nah)2 (I) and CH2(H2sal‐inh)2 (II)] derived from 5,5′‐methylenebis(salicylaldehyde) [CH2(Hsal)2] and nicotinic acid hydrazide (nah) or isonicotinic acid hydrazide (inh) is described. The compounds were characterised in the solid state and in solution, namely by spectroscopic techniques (IR, UV/Vis, EPR, 1H, 13C and 51V NMR). It has been demonstrated that the dioxidovanadium(V) complexes K2[CH2{VVO2(sal‐nah)}2]·2H2O (3), Cs2[CH2{VVO2(sal‐nah)}2]·2H2O (4) and Cs2[CH2{VVO2(sal‐inh)}2]·2H2O (5) of I and II are active in the oxidative bromination of salicylaldehyde by H2O2, therefore acting as functional models of vanadium‐dependenthaloperoxidases, and it has also been shown that the corresponding oxidovanadium(IV) complexes [CH2{VIVO(sal‐nah)(H2O)}2] (1) and [CH2{VIVO(sal‐inh)(H2O)}2] (2) are catalyst precursors for the catalytic oxidation, by peroxide, of methyl phenyl sulfide and diphenyl sulfide, yielding the corresponding sulfoxide and sulfone. Plausible intermediates involved in these catalytic processes are established by UV/Vis, EPR and 51V NMR studies. The dioxidovanadium(V) complexes along with ligands I and II were also screened against HM1:1MSS strains of Entamoeba histolytica. The results showed that the IC50 values of compounds 3 and 5 are lower than the IC50 value of metronidazole. The toxicity studies against human cervical (HeLa) cell lines showed that compounds 3 and 5 are not much toxic but are more toxic than metronidazole. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Ligational behavior of thiosemicarbazone, semicarbazone and thiocarbohydrazone ligands towards VO(IV), Ce(III), Th(IV) and UO2(VI) ions: Synthesis, structural characterization and biological studies

Mono- and binuclear VO(IV), Ce(III), Th(IV) and UO(2)(VI) complexes of thiosemicarbazone, semicarbazone and thiocarbohydrazone ligands derived from 4,6-diacetylresorcinol were synthesized. The structures of these complexes were elucidated by elemental analyses, IR, UV-vis, ESR, (1)H NMR and mass spectra as well as conductivity and magnetic susceptibility measurements and thermal analyses. The thiosemicarbazone (H(4)L(1)) and the semicarbazone (H(4)L(2)) ligands behave as dibasic pentadentate ligands in case of VO(IV) and UO(2)(VI) complexes, tribasic pentadentate in case of Ce(III) complexes and monobasic pentadentate in case of Th(IV) complexes. However, the thiocarbohydrazone ligand (H(3)L(3)) acts as a monobasic tridentate ligand in all complexes except the VO(IV) complex in which it acts as a dibasic tridentate ligand. The antibacterial and antifungal activities were also tested against Rhizobium bacteria and Fusarium-Oxysporium fungus. The metal complexes of H(4)L(1) ligand showed a higher antibacterial effect than the free ligand while the other ligands (H(4)L(2) and H(3)L(3)) showed a higher effect than their metal complexes. The antifungal effect of all metal complexes is lower than the free ligands.

Synthesis and spectral studies of nickel(II) complexes derived from disalicylaldehyde oxaloyldihydrazone

The mononuclear nickel(II) complex [Ni(H2slox)(H2O)3] (1) and polymeric dinuclear complexes [Ni2(slox)(A4)] {A = H2O (2), py (3), 2-pic (4), 3-pic (5) and 4-pic (6)} and the discrete binuclear complexes [Ni2(slox)(NN)3] {NN = bpy (7) and phen (8)} have been synthesized from disalicylaldehyde oxaloyldihydrazone (H4slox) in methanol. All of the complexes are nonelectrolytes. Complexes 1, 7, and 8 are paramagnetic while binuclear 2–6 possess anomalously low μ eff value, indicating considerable metal–metal interaction. Discrete binuclear 7 and 8 have no interaction between the two nickel(II) ions. The anomalously low magnetic moment values in 2–6 are explained as metal–metal interaction via phenoxide bridge. Such metal–metal interactions are less in 7 and 8 due to coordination of bipyridine and phenanthroline molecules which do not allow phenoxide bridging. The dihydrazone coordinates to the metal center as a dibasic tridentate ligand in keto-enol form in staggered configuration in 1, while in the remaining complexes the dihydrazone is tetrabasic hexadentate in enol form in anticis configuration. The metal center has a tetragonally distorted octahedral stereochemistry.

Synthesis, spectroscopic, redox, catalytic and antimicrobial properties of some ruthenium(II) Schiff base complexes

A new series of mixed ligand semicarbazone or thiosemicarbazone complexes of Ru(II) having the general formula [RuCO(EPh3)(B)L] (where E = P or As; B = PPh3, AsPh3 or Pyridine; L = dibasic tridentate ligand derived by the condensation of ethylacetoacetate/methylacetoacetate and thiosemicarbazide/semicarbazide) have been synthesized and characterized by physico-chemical, spectroscopic and electrochemical studies. A comparative study on the catalysis of oxidation of benzyl alcohol, cyclohexanol, cinnamyl alcohol, n-butanol, n-propanol and iso-butyl alcohol has been done with N-methylmorpholine-N-oxide and molecular oxygen as co-oxidants. Catalytic activity studies of the complexes in coupling reactions have been carried out. The antibacterial properties of the complexes have also been examined.

Transition metal complexes of a Schiff base: synthesis, characterization, and antibacterial studies

Synthesis of a new Schiff base derived from 2-hydroxy-5-methylacetophenone and glycine and its coordination with compounds Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and UO2(VI) are described. The ligand and complexes have been characterized on the basis of analytical, electrical conductance, infrared, ESR and electronic spectra, magnetic susceptibility measurements, and thermogravimetric analysis. The ligand is a dibasic tridentate (ONO) donor in all the complexes except Zn(II), where it is a monobasic bidentate (OO) donor. The solid state DC electrical conductivity of ligand and its complexes have been measured over 313–398 K, and the complexes were semiconducting. Antibacterial activities of ligand and its metal complexes have been determined by screening the compounds against various Gram (+) and Gram (−) bacterial strains.

Synthesis, structural, and biological studies of some bivalent metal ion complexes with the tridentate Schiff base ligand

New complexes of a Schiff base derived from 2-hydroxy-5-chloroacetophenone and glycine with Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and UO2(VI) have been synthesized. The ligand and the complexes have been characterized on the basis of analytical data, electrical conductance, IR, ESR, and electronic spectra, magnetic susceptibility measurements and thermogravimetric analysis. The ligand acts as a dibasic tridentate (ONO) donor molecule in all the complexes except the Zn(II) complex, where it acts as a monobasic bidentate (OO) donor. Antibacterial activities of the ligand and its metal complexes have been determined by screening the compounds against various Gram(+) and Gram(−) bacterial strains. The solid state d.c. electrical conductivity of the ligand and its complexes has been measured over 313–398 K and the complexes were found to be of semiconducting nature.

Synthesis, spectral and magnetic studies of mono- and bi-nuclear metal complexes of a new bis(tridentate NO2) Schiff base ligand derived from 4,6-diacetylresorcinol and ethanolamine

A new bis(tridentate NO2) Schiff base ligand, H4L, was prepared by the reaction of the bifunctional carbonyl compound; 4,6-diacetylresorcinol (DAR) with ethanolamine. The ligand reacted with iron(III), cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), cerium(III) and uranyl(VI) ions, in absence and in presence of LiOH, to yield mono- and bi-nuclear complexes with different coordinating sites. The ligand and its metal complexes were characterized by elemental analyses, IR, 1H NMR, electronic, ESR and mass spectra, conductivity and magnetic susceptibility measurements as well as thermal analyses. In absence of LiOH, mononuclear complexes (2, 3 and 5–9) as well as binuclear complexes (1 and 4) were obtained. In mononuclear complexes, the ligand acted as a neutral, mono- and di-basic/bi- and tetra-dentate ligand while in binuclear complexes (1 and 4), the ligand acted as a bis(mono- or di-basic/tridentate) ligand. On the other hand, in presence of LiOH, only binuclear complexes (10–15) were obtained in which the ligand acted as a bis(dibasic tridentate) ligand. The metal complexes exhibited different geometrical arrangements such as octahedral, tetrahedral, square planar, square pyramidal and pentagonal bipyramidal arrangements.

Spectroscopic characterization and biological activity of metal complexes with an ONO trifunctionalized hydrazone ligand

A series of Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), La(III), Ru(III), Hf(IV), Zr(IV) and U(VI) complexes of phenylamino acetoacetylacetone hydrazone have been synthesized and characterized by elemental analyses, IR, UV–Vis, magnetic moments, conductances, thermal analyses (DTA and TGA) and ESR measurements. The IR data show that the ligand is neutral bidentate, monobasic bidentate, monobasic tridentate or dibasic tridentate towards the metal ion. Molar conductances in DMF indicate that the complexes are non-electrolytes. The ESR spectra of solid [(L)(HL)Cu2(NO3)(H2O)]·1/2H2O (10) and [(H2L)Cu(Cl)2(H2O)2] (11) show axial spectra with g∥ > g⊥ > 2.0023 indicating d(x² − y²) ground state with significant covalent bond character. However, [(HL)2Mn2(Cl)2(H2O)4·H2O (13) shows an isotropic spectrum, indicating manganese(II) to be octahedral. Antibacterial and antifungal tests of the ligand and some of its metal complexes revealed that the complexes are more potent bactericides and fungicides than the ligand.

Solution Study of a Structurally Characterized Monoalkoxo-Bound Monooxo-Vanadium(V) Complex: Spontaneous Generation of the Corresponding Oxobridged Divanadium(V,V) Complex and its Electroreduction to a Mixed-Valence Species in Solution

An interesting transformation of a structurally characterized monooxoalkoxovanadium(V) complex [VO(OEt)L] (LH 2 = a dibasic tridentate ONO donor ligand) in solution leading to the formation of the corresponding monooxobridged divanadium(V,V) complex (VOL) 2O is reported. This binuclear species in solution is adequately characterized by elemental analysis, measurement of conductance (in solution), various spectroscopic (UV-vis, IR, NMR, and mass spectrometry) techiniques and by cyclic voltammetry. The corresponding mixed-valence vanadium(IV,V) species has been generated in CH 3CN solution by controlled potential electrolysis of (VOL) 2O. This mixed-valence species is identified and studied by EPR technique (at room temperature and at liquid nitrogen temperature) and also by UV-vis spectroscopy. This study may be regarded as a general method of obtaining monooxo-bridged binuclear vanadium(V,V) species from the corresponding mononuclear monooxoalkoxovanadium(V) complexes of some selected dibasic tridentate ONO chelating ligands, which can be utilized as the precursor of monooxobridged divanadium(IV,V) mixed-valence species in solution obtainable by controlled potential electrolysis.

Reactions of 2-(1-carboxyl-2-hydroxyphenyl)thiazolidine with chromium(III) salts leading to newer synthesis of chromium(III) complexes

Reactions of 2-(L-carboxyl-2-hydroxyphenyl)thiazolidine with different chromium(III) salts [CrCl3 · 6H2O, K3[Cr(SCN)6], NH4[Cr(NH3)2(SCN)4] · H2O, [Cr(urea)6]Cl3 · 3H2O and [Cr(CH3COO)2H2O]2] under varied reaction conditions afforded many new mixed-ligand chromium(III) complexes. The ligand is a tridentate dibasic NSO donor except for complexes 1 and 4 where two moles of the ligand are present for each molecule of complex, one functioning as a dibasic tridentate (NSO) and the other as a monobasic bidentate (NS) (phenolic OH and carboxylic COOH groups remaining uncoordinated). The complexes have been characterized by elemental analyses, magnetic susceptibilities, molar conductances, molecular weights and spectroscopic (IR, Uv-vis) data. The ligand field parameters and NSH Hamiltonian parameters suggest tetragonal geometries of the complexes.

Synthesis, spectral and thermal studies of tin(IV) complexes using 2-benzimidazolylmercaptoaceto hydrazone type of ligands

The metal complexes of Sn IV with 2-benzimidazolylmercaptoaceto hydrazones of 1 : 2 metal to ligand stoichiometry have been synthesized. Molar conductance data reveal their non-electrolytic nature. The spectral studies show that the ligands react in enol form and behave as dibasic tridentate ONO donor. The thermal stabilities of the complexes have been studied by TG and their kinetic parameters calculated using Coats-Redfern and MKN methods. From these results, a coordination number six for tin ion in the complexes of the type SnL 2 have been proposed.

Synthesis, spectroscopic characterization and biological activity of the metal complexes of the Schiff base derived from phenylaminoacetohydrazide and dibenzoylmethane

A new series of mono and binuclear Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), La(III), Ru(III), Hf(IV), ZrO(II) and UO 2(II) complexes of phenylaminodibenzoylhydrazone have been synthesized and characterized by elementals analyses, IR UV–vis spectra, magnetic moments, conductances, thermal analyses (DTA and TGA) and electron spin resonance (ESR) measurements. The IR spectral data show that, the ligand behaves as a neutral bidentate type ( 15 and 16), monobasic bidentate type ( 6), or monobasic tridentate type ( 5, 7, 8, 10, 11, 13, 14, 17– 21) or dibasic tridentate type 2– 4, 9 and 12 towards the metal ion. Molar conductances in DMF solution indicate that, the complexes are non-electrolytes. The ESR spectra of solid complexes ( 9 and 10) show axial and non-axial types indicating a d ( x 2 − y 2 ) ground state with significant covalent bond character. However, complexes ( 11 and 12), show isotropic type, indicating manganese(II) octahedral geometry. Antibacterial and antifungal tests of the ligand and its metal complexes are also carried out and it has been observed that the complexes are more potent bactericides and fungicides than the ligand.