Enzyme inhibition,radical scavenging,and spectroscopic studies of vanadium(IV)–hydrazide complexes

Spectroscopic, enzyme-inhibition, and free-radical scavenging properties of a series of hydrazide ligands and their vanadium(IV) complexes have been investigated. Analytical and spectral data indicate the presence of a dimeric unit with two oxovanadium(IV) ions (VO²⁺) coordinated with two hydrazide ligands along with two water molecules. All complexes are stable in the solid state, but exhibit varying degrees of stability in solution. Binding of the coordinating solvent such as DMSO is indicated at the 6th position of vanadium in the dimeric unit followed by conversion to a monomeric intermediate species, [VOL(DMSO)3]1+ (L = hydrazide ligand). The free hydrazide ligands are inactive against snake venom phosphodiesterase I (SVPD), whereas oxovanadium(IV) complexes of these ligands show varying degrees of inhibition and are found to be non-competitive inhibitors. The superoxide and nitric oxide radical scavenging properties have been determined. Hydrazide ligands are inactive against these free radicals, whereas their V(IV) complexes show varying degrees of inhibition. Structure–activity relationship studies indicate that the electronic and/or steric factors that change the geometry of the complexes play an important role in their inhibitory potential against SVPD and free radicals.     

Synthesis, spectroscopy, and biological properties of vanadium(IV)-hydrazide complexes

The synthesis, spectroscopic, enzyme-inhibition, and free-radical-scavenging properties of a series of vanadium(IV) complexes, compounds 1-10, were investigated. These complexes exhibit a dimeric structure with hydrazide ligands coordinated in a bidentate fashion. All complexes are stable in the solid state, but exhibit varying degrees of stability in solution. In coordinating solvent such as DMSO, stepwise binding of two solvent molecules at the 6th positions trans to the V double bond O bond of the dimeric unit is observed. The dimeric compounds are converted to monomeric species in which both solvent molecules and the hydrazide ligands are coordinated to the V(IV) center. The free hydrazide ligands 11-20 were inactive against alpha-glucosidase, but the V(IV) complexes showed varying degrees of inhibition, depending on the type of ligand. The DPPH-radical-scavenging activities of 1-20 were determined, which indicated that steric and/or electronic effects responsible for changes in geometry play important roles in terms of antioxidant potential.     

Synthesis and characterization of mononuclear oxovanadium(IV) complexes and their enzyme inhibition studies with a carbohydrate metabolic enzyme phosphodiesterase I

The increasing interest in vanadium coordination chemistry is based on its well-established chemical and biological functions. A beta-diketonato complex of oxovanadium(IV) is known to be having numerous catalytic applications and also exhibits promising insulin mimetic properties. In continuation of our structure activity relationship studies of metal complexes, we report herein the synthesis and characterization of the vanadium complexes of beta-diketonato ligand system with systematic variations of electronic and steric factors. Two complexes, VO(tmh)(2) (tmh = 2,2,6,6,-tetramethyl-3,5-heptanedione), and VO(hd)(2) (hd = 3,5-heptanedione) were synthesized and characterized by using different spectroscopic techniques. Elemental and mass spectral analysis supports the presence of two beta-diketonato ligands per VO(2+) unit. UV-Vis spectra in different solvents indicate coordination of coordinating solvent molecules at sixth position resulting in red shift of the band I transition. NMR and IR spectra reveal binding of coordinating solvent molecule at vacant sixth position trans to oxo group without releasing beta-diketonato ligands. Enzyme inhibition studies of these and other related oxovanadium(IV) complexes with beta-diketonato ligand system are conducted with snake venom phosphodiesterase I (SPVDE). All of these complexes showed significant inhibitory potential and were found to be non-competitive inhibitors against this enzyme.     

Platinum(II) complexes of 4-methoxy- and 4-chlorobenzoic acid hydrazides. Synthesis, characterization, and cytotoxic effect

The complexes [Pt(NH₃)(pmbah)Cl₂], [Pt(NH₃)(pcbah)Cl₂], [Pt(pmbah₂X₂] and [Pt(pcbah)₂X₂] (pmbah = 4-methoxybenzoicacid hydrazide, pcbah = 4-chlorobenzoic acid hydrazide; X = Cl, Br, I) have been synthesized and characterized by elemental analysis, electric conductivity, ¹H NMR, IR, and electronic spectra. A cis-square planar structure with hydrazide ligands coordinated via the NH₂ groups has been proposed for these compounds. The complexes, but not the free ligands, have shown a strong growth inhibitory effect in Friend leukemia cells in vitro, most of which are more active than cisplatin.     

Improving anti-trypanosomal activity of 3-aminoquinoxaline-2-carbonitrile N1,N4-dioxide derivatives by complexation with vanadium

New vanadium complexes of the type [V(IV)O(L)(2)], where L are 3-aminoquinoxaline-2-carbonitrile N(1),N(4)-dioxide derivatives, were prepared as an effort to obtain new anti-trypanosomal agents improving the bioactivity of the free ligands. Complexation to vanadium of the quinoxaline ligands leads to excellent antiprotozoal activity, similar to that of the reference drugs nifurtimox and benznidazole and in all cases higher than that of the corresponding free ligands. In addition, it is for the first time that the V((IV))O-quinoxaline complexes are reported as a family of anti-Trypanosoma cruzi agents. Finally, the anti-trypanosomal activity of these vanadium complexes could be explained on the basis of their lipophilicity and the electronic characteristics of the quinoxaline substituents.     

Vanadium(IV/V) speciation of pyridine-2,6-dicarboxylic acid and 4-hydroxy-pyridine-2,6-dicarboxylic acid complexes: potentiometry,EPR spectroscopy and comparison across oxidation states

Evaluation of stability of vanadium(IV) and (V) complexes under similar conditions is critical for the interpretation and assessment of bioactivity of various vanadium species. Detailed understanding of the chemical properties of these complexes is necessary to explain differences observed their activity in biological systems. These studies are carried out to link the chemistry of both vanadium(IV) and (V) complexes of two ligands, 2,6-pyridinedicarboxylic acid (dipicolinic acid, H(2)dipic) and 4-hydroxy-2,6-pyridinedicarboxylic acid (H(2)dipic-OH). Solution speciation of the two 2,6-pyridinedicarboxylic acids with vanadium(IV) and vanadium(V) ions was determined by pH-potentiometry at I=0.2 M (KCl) ionic strength and at T=298 K. The stability and the metal affinities of the ligands were compared. Vanadium(V) complexes were found to form only tridentate coordinated 1:1 complexes, while vanadium(IV) formed complexes with both 1:1 and 1:2 stoichiometries. The formation constant reflects hindered coordination of a second ligand molecule, presumably because of the relatively small size of the metal ion. The most probable binding mode of the complexes was further explored using ambient and low temperature EPR spectroscopy for vanadium(IV) and 51V NMR spectroscopy for vanadium(V) systems. Upon complex formation the pyridinol-OH in position 4 deprotonates with pK approximately 3.7-4.1, which is approximately 6 orders of magnitude lower than that of the free ligand. The deprotonation enhances the ligand metal ion affinity compared to the parent ligand dipicolinic acid. In the light of the speciation and stability data of the metal complexes, the efficiency of the two ligands in transporting the metal ion in the two different oxidation states are assessed and discussed.     

Copper complexes with heterocyclic sulfonamides: synthesis, spectroscopic characterization, microbiological and SOD-like activities: crystal structure of [Cu(sulfisoxazole)2(H2O)4] . 2H2O

The synthesis, characterization and comparative biological study of a series of antibacterial copper complexes with heterocyclic sulfonamides were reported. Two kinds of complexes were obtained with the stoichiometries [Cu(L)2] . H2O and [Cu(L)2(H2O)4] . nH2O. They were characterized by infrared and electronic spectroscopies and the crystal structure of [Cu(sulfisoxazole)2(H2O)4] . 2H2O was determined by single crystal X-ray diffraction. It crystallized in the C2/c with Z = 8 monoclinic space group C2/c with Z = 8. The Cu(II) is in a slightly tetragonal distorted octahedron formed by four oxygen atoms from water molecules and two nitrogen atoms from two isoxazole rings. The antimicrobial activity was evaluated for all the synthesized complexes and ligands using the agar dilution test. The results showed that the complexes with five-membered heterocyclic rings were more active than the free sulfonamides while the pyrimidine, pyridine and pyridazine complexes had similar or less activity than the free ligands. In order to find an explanation for this behavior lipophilicity and superoxide dismutase-like activity were tested, showing that the [Cu(sulfamethoxazol)2(H2O)4] . 3H2O presented the highest antimicrobial potency and a superoxide dismutase-like activity comparable with pharmacological active compounds.     

Organometallic complexes with biological molecules. XVII. Triorganotin(IV) complexes with amoxicillin and ampicillin

Novel triorganotin(IV) complexes of two beta-lactamic antibiotics, 6-[D-(-)-beta-amino-p-hydroxyphenyl-acetamido]penicillin (=amoxicillin) and 6-[D-(-)-alpha-aminobenzyl]penicillin (=ampicillin), have been synthesized and investigated both in solid and solution states. The complexes corresponded to the general formula R(3)Sn(IV)antib*H(2)O (R=Me, n-Bu, Ph; antib=amox=amoxicillinate or amp=ampicillinate). Structural investigations about configuration in the solid state have been carried out by interpreting experimental IR and 119Sn M?ssbauer data. In particular, IR results suggested polymeric structures both for R(3)Sn(IV)amox.H(2)O and R(3)Sn(IV)amp*H(2)O. Moreover, both antibiotics appear to behave as monoanionic bidentate ligands coordinating the tin(IV) atom through ester-type carboxylate, as well as through the beta-lactamic carbonyl. Evidence that in none of these compounds water molecules were involved in coordination, was provided by thermogravimetric investigations. On the basis of 119Sn M?ssbauer spectroscopy it can be inferred that tin(IV) was pentacoordinate in all of the complexes in the solid state, showing an equatorial R(3)Sn(IV) trigonal bipyramidal (tbp) configuration. The nature of the complexes in solution state was investigated by using 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, while an 119Sn spectrum was obtained for n-Bu(3)Sn(IV)amp*H(2)O. Although 1H- and 13C-NMR measurements suggested that in dimethyl sulfoxide (DMSO)-d(6) solution the polymeric structure collapsed, due to a solvolysis process of the beta-lactamic carbonyl bonding to the organometallic moiety, the complexes have been shown to maintain the same trigonal bipyramidal configuration at tin(IV) atom by the coordination of a DMSO molecule. Cytotoxic activity of these novel semisynthetic antibiotic derivatives has been tested towards spermatocyte chromosomes of the mussel Brachidontes pharaonis (Mollusca: Bivalvia) using two different chromosome-staining techniques such as Giemsa and CMA(3). The occurrence of typical colchicinized-like (c-like) mitoses on slides obtained from animals exposed to organotin compounds, directly confirmed the high mitotic spindle-inhibiting potency of these chemicals. In addition, by comparative analysis of spermatocyte chromosomes from untreated specimens (negative controls) and specimens treated with the triorganotin(IV) complexes, structural damages such as 'achromatic lesions' and 'chromosome breakages' have been identified.     

Synthesis,spectral characterization,in vitro microbial and cytotoxic studies of lanthanum(III) and thorium(IV) complexes with 1,2,4-triazole Schiff bases

A series of metal complexes of La(III) and Th(IV) have been synthesized with newly derived biologically active ligands. These ligands were synthesized by the condensation of 3-substituted-4-amino-5-hydrazino-1,2,4-triazole with 8-formyl-7-hydroxy- 4-methylcoumarin. The structure of the complexes has been proposed by elemental analyses, spectroscopic data i.e. i.r., ¹H nmr, Uv-Vis, FAB-mass and thermal studies. The elemental analyses of the complexes conform to the stoichiometry of the type [La(L)·3H₂O]·2H₂O and [Th(L)(NO₃)·2H₂O]·2H₂O where (L = L^I-L^IV). All the complexes are soluble in DMF and DMSO and are non-electrolytes in DMF and DMSO. All these ligands and their complexes have also been screened for their antibacterial (Escherichia coli, Staphylococcus aureus, Staphylococcus pyogenes and Pseudomonas aeruginosa) and antifungal activities (Aspergillus niger, Aspergillus flavus and cladosporium) by the MIC method. The brine shrimp bioassay was also carried out to study their invitro cytotoxic properties.     

Ligational behavior of two biologically active N-S donors toward oxovanadium(IV) ion and potentiation of their antibacterial activities by chelation to metal ions. Part III

Chelating behavior of two biologically active ligands, pyridine-2-carboxaldehyde thiosemicarbazone (PT) and pyridine-2-carboxaldehyde-(4-phenyl)thiosemicarbazone (PPT), toward oxovanadium(IV) ion has been studied. The ligands are found to react in the thioketo form (pH 2-4), yielding the complexes [VO(PT)X2](X = Cl-, Br-, ClO4-), [VO(PT)(SO4)H2O], [VO(PPT)2X]X (X = Cl-, Br-, ClO4-) and [VO(PPT)2SO4]. Reactions of [VO(PT)(SO4)H2O] and [VO(PPT)2X]X (X = Cl-, Br-, ClO4-) with a monodenate Lewis base (B) like pyridine lead to the formation of [VO(PT)(SO4)Py]H2O and [VO(PPT)2py]X2 respectively. Bonding sites of the donor molecules around the oxometal cation have been located. Nature of the EPR spectra and magnetic moment values point to the monomeric character of the complexes and suggest a distorted octahedral donor environment for the oxovanadium(IV) ion. Status of the metal-oxygen multiple bond in all the complexes has been computed in terms of the V-O(1) stretching force constant. The ligands themselves and most of their oxovanadium(IV) complexes are found to exert powerful in vitro antibacterial activities towards E. coli.     

Vanadium(V) complexes with hydrazides and their spectroscopic and biological properties

The present study explores the synthesis and inhibitory potential of vanadium(V) complexes of hydrazides (1c–12c) against oxidative enzymes including xanthine oxidase and lipoxygenase (LOX). In addition, non-enzymatic radical scavenging activities of these complexes were also determined. On the basis of spectral, elemental and physical data, synthesized vanadium(V) complexes are tentatively assigned to have an octahedral geometry with two hydrazide ligands and two oxo groups forming a negatively charged sphere complex with ammonium as counter ion. This is further verified by the conductivity studies of the complexes. Results show that hydrazide ligands (1–12) and their respective vanadium(V) complexes (1c–12c) posses scavenging and inhibition potential against DPPH and LOX, respectively. However, contrary to that uncoordinated ligands showed no activity against nitric oxide, superoxide and xanthine oxidase whereas their complexes showed varying degree of activity. These studies indicate that geometry of complex, nature and position of substituent groups play a vital role in scavenging and inhibition potential of these compounds.     

Oxovanadium(IV) complexes with aromatic aldehydes

The synthesis, structure and spectroscopic properties of complexes with the formula [V(IV)O(dsal)2(H2O)], where Hdsal = salicylaldehyde, o-vanillin and 3-ethoxysalicylaldehyde, are presented. The crystal and molecular structures of [V(IV)O(o-van)2(H2O)] (1) (o-Hvan = o-vanillin = 3-methoxysalicylaldehyde) is studied by single-crystal X-ray diffraction. Each molecule exhibits an octahedral geometry with the two o-van ligands coordinated cis to the V(IV)O2+ group. 1 is the first example of a structurally characterized vanadium complex involving O(aldehyde) as the donor atom and this enables a comparison between the bonding characteristics and the contributions of O(aldehyde), O(amide), O(carboxylate) and O(ketone) (in acetylacetone) to the parallel hyperfine coupling constant in VOL2 complexes.     

Synthesis and antitumour activity of platinum(II) and platinum(IV) complexes containing ethylenediamine-derived ligands having alcohol, carboxylic acid and acetate substituents. Crystal and molecular structure of [PtL4CL2].H20 where L4 is ethylenediamine-N,N'-diacetate

Several cisplatin analogues of ethylenediamine-derived ligands containing alcohol, carboxylic acid and acetate substituents have been prepared and characterised. Oxidation of some of these square planar platinum(II) complexes using aqueous hydrogen peroxide gave octahedral platinum(IV) complexes, containing trans hydroxo ligands. Acetylation of the hydroxo ligands was achieved by reaction with acetic anhydride, giving complexes which are analogues of the antitumour drug, JM-216. Oxidation of the complex [Pt(H2L4)Cl2], where H2L4 is ethylenediamine-N,N'-diacetic acid, with H2O2 gave the platinum(IV) complex [PtL4Cl2].H2O in which L4 is tetradentate as shown by a crystal and molecular structure. This complex was previously reported to be [Pt(HL4)(OH)Cl2] in which HL4 is tridentate. Several of the complexes were tested for antitumour activity against five human ovarian carcinoma cell lines. IC50 values range from 4.0 microM for cis,trans-PtCl2(OH)2(NH2CH2CH2NHCH2CH2OH) against the CH1 cell line to >25 microM indicating moderate to low activity relative to other platinum complexes.     

Novel ruthenium complex K2[Ru(dmgly)Cl4].2H2O is toxic to C6 astrocytoma cell line, but not to primary rat astrocytes

A novel class of ruthenium (III) complexes of formulas K[Ru(sar)2Cl2].12H2O and K2[Ru(dmgly)Cl4].2H2O, containing bidentate chelates N-methylglycine (sarcosine, sar) or N,N-dimethylglycine (dmgly) and additional chloro ligands were synthesized. The complexes have been obtained by direct reaction of ruthenium(III) chloride with corresponding bidentate ligand followed by addition of base (KOH). These new complexes were characterized by elemental analysis, IR and electronic absorption spectroscopy. As astrocytomas, the most common of all brain tumors, are still very difficult to treat, we examined the influence of newly synthesized ruthenium-based complexes, as well as the earlier synthesized analogue platinum(IV) complexes [Pt(dmgly)2Cl2], [Pt(sar)2Br2] and [Pt(dmgly)2Br2], on rat astrocytoma C6 cells in vitro. Among these complexes only K2[Ru(dmgly)Cl4].2H2O and [Pt(dmgly)2Br2] markedly inhibited the viability of non-confluent C6 cells. Furthermore, only complex K2[Ru(dmgly)Cl4].2H2O was able to reduce viability in confluent C6 cultures. Importantly, this complex was not toxic to primary rat astrocytes or macrophages. Having in mind that appropriate chemotherapy should be effective against tumor cells without harming normal tissues, complex K2[Ru(dmgly)Cl4].2H2O could be a promising agent for developing therapeutics against astrocytomas.     

Spectrophotometric and ESR evidence for vanadium(IV) deferoxamine complexes.

Complexes of vanadium(IV), vanadyl, are reported to be formed with the trihydroxamic acid deferoxamine (H3DF+). One complex exhibits a reddish-violet color, with a major absorbance peak at 386 nm and a smaller peak at 520 nm. This complex is potentially useful for the microdetermination of vanadyl. The apparent molar absorptivity is 3.91 mM-1 cm-1, and the complex obeys Beer's law in the concentration range of 0.6-63 ppm. Electron spin resonance studies indicate the formation of two vanadyl complexes that are 1:1 in vanadyl and deferoxamine, but have two or three bound hydroxamate groups. ESR and spectrophotometric evidence indicate that the red, low pH form, involves an octahedral vanadium (4+) ion coordinated by three hydroxamate ligands. One of these hydroxamates is displaced by an oxygen at pH greater than 2.8 according to the following equilibria: VO2+ + H3DF+ in equilibrium with VIV(DF)2+ + H3O+, VIV(DF)2+ + H2O in equilibrium with VO(HDF)+ + H+, where pk2 = 2.8.     

Structural and functional characterization of seven spermicidal vanadium(IV) complexes: potentiation of activity by methyl substitution on the cyclopentadienyl rings.

In a systematic effort to identify and develop effective vanadocene(IV) complexes as a new class of contraceptive agents, the effect of methyl substitution in the cyclopentadienyl rings of Cpx2VCl2 on their spermicidal activity has been examined. The spermicidal activities of compounds Cpx2VCl2 [Cpx = Me5Cp (Cp*) (1), Cp (3), MeCp (Cp') (5)], as well as two of their corresponding vanadium(V) oxidation products Cp*V(O)Cl2 (2) and CpV(O)Cl2 (4), were examined by computer-assisted sperm analysis (CASA). These analyses have established that penta-substitution of the Cp ring by electron-donating methyl groups augments the spermicidal activity 10-fold. The corresponding V(V) oxo compounds, Cp*V(O)Cl2 (2) and CpV(O)Cl2 (4), tested under identical conditions did not show as effective spermicidal activity even though these complexes have a pseudo-tetrahedral geometry similar to the active vanadocene(IV) dichlorides. Two pseudo-octahedral V(IV) complexes with tris-pyrazolyl borate as ligand, (HBpz3)V(O)Cl.DMF (6) and (HB(3,5-Me2pz)3)V(O)Cl.DMF (7), were also found to exhibit potent spermicidal activity. Although some vanadium(IV) complexes may immobilize sperm due to the generation of .OH radicals, the lack of spermicidal activity of VOSO4 which generates .OH radicals, and the potent spermicidal activity of [Cp2V(acac)][O3SCF3] (8), and [Cp2V(DeDtc)][O3SCF3] (9) which do not generate .OH radicals, indicate that .OH radical mediated reactions may not be essential for the spermicidal activity of vanadium(IV) complexes.     

Synthesis and aqueous solution properties of multinuclear oxo-bridged vanadium(IV/V) complexes

Reaction of the multifunctional phenolic ligands 2,5-bis[N,N-bis(carboxymethyl)aminomethyl]hydroquinone (H6cahq), 2,2'-bis[N,N-bis(carboxymethyl)aminomethyl]-4,4'-isopropylidenediphen ol(H6capd),2,2',2'-tris[N,N-bis(carboxymethyl)aminomethyl]-1,1 ,1-tris(4-hydroxyphenyl)ethane (H9catp) and the monofunctional 2-[N,N-bis(carboxymethyl)aminomethyl]-4-carboxyphenol (H3cacp), with VOSO4 and NaVO3 affords the oxo-bridged mixed-valence vanadium(IV/V) Na6[(VO)4(mu-O)2(mu-cahq)2] x Na2SO4 x 20H2O (1), HnNa(3-n)[(VO)2(mu-O)(mu-cacp)2] (2), HnNa(3-n)[(VO)4(mu-O)2(mu-capd)2] (3), HnNa(9-n)[(VO)6(mu-O)3(mu3-catp)2] (4). In addition to the synthesis, we report the infrared, magnetic, optical and electrochemical properties of these complexes. The hydrolytic stability at different pH values was also investigated using visible spectroscopy.     

Characterization of oxovanadium (IV) complexes of D-gluconic and D-saccharic acids and their bioactivity on osteoblast-like cells in culture

Oxovanadium (IV) complexes of the alpha-hydroxycarboxylic ligands D-gluconic and D-saccharic acids of stoichiometry Na(2)[VO(gluconate)(2)].H(2)O, K(2)[VO(saccharate)(2)].4H(2)O, Na(4)[VO(gluconate)(2)].2H(2)O and K(5)[VO(saccharate)(2)].4H(2)O were obtained in aqueous solutions; the first two in acid, the other two in alkaline media. They were characterized by infrared and UV-Vis spectroscopies, thermoanalytical (thermogravimetric and differential thermal analysis) data and magnetic susceptibility measurements. The complexes were found to be mononuclear, possessing the VO(2+) moiety, and the thorough analysis of the spectral data allowed the determination of the characteristics of the metal-to-ligand interactions. The biological activities of these complexes on the proliferation, differentiation and glucose consumption were tested on osteoblast-like cells in culture. Comparisons of these effects and those of the oxovanadium (IV) cation and the free ligands were performed. Different behaviors could be observed for the complexes obtained at acidic or alkaline pH-values, as well as for the different cellular types. The free ligands did not show any biological effect.     

Preparation, structural, spectroscopic, thermal and DFT characterization of cadmium(II) complexes with quinaldic acid

Cadmium(II) complex with quinaldic acid (quinH), [Cd(quin)₂(H₂O)₂] (1), was prepared by the reaction of cadmium(II) acetate and quinaldic acid in water-ethanol mixture, while another cadmium(II) complex, [Cd(quin)₂(DMSO)₂] (2), was prepared by the recrystallization of 1 in DMSO. Both complexes were characterized by IR spectroscopy and TGA/DTA methods. The crystal structure of 2 was determined by X-ray structure diffraction analysis. Cadmium(II) ion is octahedrally coordinated by two N,O-bidentate quinaldate ligands in equatorial and by two DMSO molecules in axial positions. Only weak intermolecular C-H···O hydrogen bonds and π-π stacking interactions as packing forces are present in the crystal structure of 2. The theoretical investigations included geometry optimizations of both complexes at DFT level (B3LYP and mPW1PW91 functionals) and calculations of vibrational frequencies. Calculated and experimental IR spectra were compared and characteristic bands assigned. The electronic properties of the complexes were investigated by the NBO analysis. Thermogravimetric studies showed the initial loss of two coordinated water molecules in 1 and of DMSO in 2 and then complete decomposition of quinaldate ligands for both 1 and 2.