Resonance Raman studies of the peroxotitanate(IV) complexes K2(Ti(O2)(SO4)2)·5H2O and K2(Ti(O2)(C2O4)2)·3H2O

The resonance Raman spectra of K₂(Ti(O₂)(SO₄)₂)·5H₂O and K₂(Ti(O₂)(C₂O₄)₂)·3H₂O are recorded. The results are consistent with the triangular structure of the peroxotitanium unit, Ti(O₂), with C_2ν symmetry. The ν(OO), ν_s(TiO) and ν_as(TiO) are observed around 890, 610 and 535 cm⁻¹, respectively. The resonance effects are shown to be associated with the 425 nm absorption band. This band is assigned to the O₂²⁻ → Ti(IV) charge-transfer transition. The calculated force constant values for the O₂²⁻ and TiO bonds are 320 and 275 N m⁻¹, respectively.     

Antibacterial,antifungal and in vitro antileukaemia activity of metal complexes with thiosemicarbazones

1‐phenyl‐3‐methyl‐4‐benzoyl‐5‐pyrazolone 4‐ethyl‐thiosemicarbazone (HL) and its copper(II), vanadium(V) and nickel(II) complexes: [Cu(L)(Cl)]·C₂H₅OH·( 1 ), [Cu(L)₂]·H₂O ( 2 ), [Cu(L)(Br)]·H₂O·CH₃OH ( 3 ), [Cu(L)(NO₃)]·2C₂H₅OH ( 4 ), [VO₂(L)]·2H₂O ( 5 ), [Ni(L)₂]·H₂O ( 6 ), were synthesized and characterized. The ligand has been characterized by elemental analyses, IR, ¹H NMR and ¹³C NMR spectroscopy. The tridentate nature of the ligand is evident from the IR spectra. The copper(II), vanadium(V) and nickel(II) complexes have been characterized by different physico‐chemical techniques such as molar conductivity, magnetic susceptibility measurements and electronic, infrared and electron paramagnetic resonance spectral studies. The structures of the ligand and its copper(II) ( 2 , 4 ), and vanadium(V) ( 5 ) complexes have been determined by single‐crystal X‐ray diffraction. The composition of the coordination polyhedron of the central atom in 2 , 4 and 5 is different. The tetrahedral coordination geometry of Cu was found in complex 2 while in complex 4 , it is square planar, in complex 5 the coordination polyhedron of the central ion is distorted square pyramid. The in vitro antibacterial activity of the complexes against Escherichia coli, Salmonella abony, Staphylococcus aureus, Bacillus cereus and the antifungal activity against Candida albicans strains was higher for the metal complexes than for free ligand. The effect of the free ligand and its metal complexes on the proliferation of HL‐60 cells was tested.     

Preparation and properties of some new 6-heteropoly-tellurate compounds of tungsten and molybdenum containing vanadium

Methods for preparing the following compounds (NH₄)₇TeW₅VO₂₄·5H₂O, (NH₄)₈TeW₄V₂O₂₄·xH₂O, (NH₄)₉TeV₃W₃O₂₄·xH₂O and (NH₄)₇TeMo₅VO₂₄·8H₂O are described. The compounds thus prepared were examined for thermal behavior, IR, Raman, UV, X-ray, NMR and reaction with base.     

Bis(oxalato)dioxovanadate(V) and Bis(oxalato)oxoperoxo-vanadate(V) Complexes: Spectroscopic Characterization and Biological Activity

Two structurally related vanadium(V) complexes, K₃[VO₂(C₂O₄)₂]·3H₂O and K₃[VO(O₂)(C₂O₄)₂]·1/2H₂O, were thoroughly characterized by infrared, Raman, and electronic spectroscopies. The effect of both complexes on the viability of the human MG-63 osteosarcoma cells was tested using the MTT assay. The monoperoxo complex shows a very strong antiproliferative activity (at 100-μM concentration, this complex diminished the cell viability ca. 80 %), whereas the dioxo complex was inactive.     

Synthesis,inhibitory activity and molecular docking studies of two Cu(II) complexes against Helicobacter pylori urease

Two mononuclear copper(II) complexes, [Cu(C₁₅H₁₆NO₂)₂] (1) and [Cu(C₆H₉N₂O₄)₂·3H₂O] (2·3H₂O), were synthesised and structurally characterised by single-crystal X-ray analysis. The copper(II) atom adopts a square-planar environment in complex 1, while the geometry in 2·3H₂O could be described as the distorted square pyramidal. Complexes 1 and 2·3H₂O were evaluated for their inhibitory activities against Helicobacter pylori (H. pylori) urease in vitro. They both were found to have strong inhibitory activities against H. pylori urease comparable to that of acetohydroxamic acid (AHA). A docking simulation was performed to position 2 into the H. pylori urease active site to determine the probable binding conformation.     

Host-guest Interactions in Intercalates Zr(HPO4)2·2C2H5OH and VOPO4·2C2H5OH

Molecular mechanics simulations using Cerius² modelling environment combined with vibrational spectroscopy (IR and Raman) have been used to study the host-guest interactions in zirconium and vanadyl phosphate intercalated with ethanole. The strategy of investigation is based on the comparison of vibrational spectra for the host compound, intercalate and guest species. This comparison confirmed the rigidity of VOPO₄- and Zr(HPO₄)₂-layers during the intercalation and provided us with the basis for the strategy of modelling. Molecular mechanics simulations revealed the structure of intercalates and enabled to analyse the host-guest interaction energy and bonding geometry. The bilayer arrangement of ethanole molecules in the interlayer space with two differently bonded ethanole molecules has been found in both intercalates. The average interaction energy ethanole-layer for two differently bonded ethanole molecules is : 127.5 and 135.7 kcal·mol^-1 in Zr(HPO₄)₂·2C₂H₅OH, respectively 94.0 and 104.4 kcal·mol^-1 in VOPO₄·2C₂H₅OH. The Coulombic contribution to the ethanole-layer interaction energy is predominant in all cases, but the hydrogen bonding contribution is much higher in Zr(HPO₄)₂·2C₂H₅OH than in VOPO₄·2C₂H₅OH. Present results of modelling enabled the interpretation of vibrational spectra and explanation of small changes in positions and shapes of spectral bands, in infrared and Raman spectra, proceeding from the host structure to intercalates.     

Reactions of VCl3, VCl4 and TiX4 (XCl,Br) with benzofuroxan and its 5-methyl-, 5-chloro- and 5-methoxi-derivatives. I.

By means of the reaction between VCl₃ and benzofuroxan the compound VCl₃·2C₆H₄N₂O₂ was obtained, while in reaction with TiX₄ (XCl, Br) the compounds with stoichiometry TiX₄·C₆H₄N₂O₂ (X Cl, Br) were obtained.Furthermore, with some benzofuroxan derivatives (5-methyl, 5-chloro and 5-methoxi) the complexes MCl₄·2YC₆H₃N₂O₂ (MTi, V; YCH₃O, Cl, CH₃), TiCl₄·YC₆H₃N₂O₂ (YCH₃O, CH₃) and TiBr₄·YC₆H₃N₂O₂ (YCH₃O, Cl, CH₃) have been isolated.The compounds were characterized by elementary analysis, cryoscopic molecular weight determination in nitrobenzene, magnetic measurements and IR, Vis and EPR spectroscopy.     

Experimental and Theoretical Studies of Calcium Fructoborate

Calcium fructoborate samples of composition Ca(C₆H₁₀O₆BO)₂·3.5H₂O were characterized by chemical analysis, infrared and Raman spectroscopy, and thermoanalytical (thermogravimetric and differential thermal analysis) data. Theoretical studies, using density functional theory, were made for seven different structural models of the fructoborate moiety, and the most stable structure could be derived from these calculations. The results of the theoretical study also allow improving the assignment of the vibrational spectra of the compound.     

N-substituted ethylcarbamate complexes of thorium(IV) and lanthanum(III) nitrates

N-substituted ethylcarbamates form with thorium nitrate the complexes Th(NO₃)₄·3RHNC(O)OC₂H₅ (where R = CH₃, C₂H₅, C₆H₅(CH₃)CH) and with lanthanum nitrate the complexes La(NO₃)₃· 2RR′NC(O)OC₂H₅·3H₂O (where R = CH₃, C₂H₅, C₆H₅(CH₃)CH; R′ = H and R = CH₃, C₆H₅; R′ = C₂H₅ or R = R′ = CH₃). In addition the anhydrous La(NO₃)₃·3(C₂H₅)₂NC(O)OC₂H₅ has been isolated. From the IR spectra it is deduced that the carbamates coordinate the metal through the carbonyl oxygen atom and that the nitrato groups act as chelated ligands. ¹H nmr spectral data of the complexes are reported and discussed.     

Synthesis,crystal structure and biological evaluation of spectroscopic characterization of Ni(II) and Co(II) complexes with N‐salicyloil‐N′‐maleoil‐hydrazine as anticholinergic and antidiabetic agents

[Ni(C₁₁H₉N₂O₅)₂(H₂O)₂]?3(C₃H₇NO) ( 1 ) and [Co(C₁₁H₉N₂O₅)₂(H₂O)₂]?3(C₃H₇NO) ( 2 ) are synthesized and characterized by elemental analysis, FT‐IR spectra, magnetic susceptibility, and thermal analysis. In addition, the crystal structure of Ni(II) complex is presented. Both complexes show distorted octahedral geometry. In 1 and 2, metal ions are coordinated by two oxygen atoms of salicylic residue and two nitrogen atoms of maleic amide residue from two ligands, and two oxygen atoms from two water molecules. In this paper, both compounds showed excellent inhibitory effects against human carbonic anhydrase (hCA) isoforms I, and II, α‐glycosidase, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE). Compounds 1 and 2 had Ki values of 18.36 ± 4.38 and 26.61 ± 7.54 nM against hCA I and 13.81 ± 3.02 and 29.56 ± 6.52 nM against hCA II, respectively. On the other hand, their Ki values were found to be 487.45 ± 54.18 and 453.81 ± 118.61 nM against AChE and 199.21 ± 50.35 and 409.41 ± 6.86 nM against BChE, respectively.     

Spectroscopic and magnetic properties of a Ni(II) complex with citric acid

The complex compound K₂[Ni(cit)(H₂O)₂]₂·4H₂O (cit = triionized citrate ion) seems to be a good model for the investigation of Ni(II)/citrate interactions that are of interest in relation to nickel metabolism and bioaccumulation. Its infrared and Raman spectra were recorded and analyzed on the basis of its structural peculiarities. The magnetic susceptibility, investigated in the temperature range between 1.9 and 300 K, shows the absence of magnetic interactions between the two metal centers present in this structure.     

Synthesis,structures and characterization of the dinuclear nickel(II) complexes containing N,N,N′,N′-tetrakis[(1-ethyl-2-benzimidazolyl)methyl]-2-hydroxy-1,3-diaminopropane and an azide ion

Two dinuclear nickel(II) complexes, [Ni₂(L-Et)(N₃)(H₂O)₃](NO₃)₂ · 2H₂O (1) and [Ni₂(L-Et)(μ-1,3-N₃)(H₂O)₂](NO₃)₂ · 4H₂O (2) containing (HL-Et = N,N,N′,N′-tetrakis[(1-ethyl-2-benzimidazolyl)methyl]-2-hydroxy-1,3-diaminopropane), have been synthesized and characterized by their IR and UV–Vis spectra and magnetic susceptibilities. The crystal structures of [Ni₂(L-Et)(N₃)(H₂O)₃](NO₃)₂ · CH₃OH (1′) and [Ni₂(L-Et)(μ-1,3-N₃)(H₂O)₂](NO₃)₂ · 2C₂H₅OH (2′) similar to 1 and 2 were determined by X-ray crystallography. In 1′, the two nickel(II) ions are bridged by only an alkoxo group of L-Et⁻, while an azido and an alkoxo connect two nickel(II) ions in 2′. Magnetic susceptibility measurements (2–300 K) showed a weak ferromagnetic exchange coupling between the two nickel(II) ions (2J = 10.1 cm⁻¹) for 1. On the other hand, antiferromagnetic interactions were observed for 2 (2J = −15.8 cm⁻¹).     

Luminescence enhancement of terbium(III) perchlorate by 2,2′‐dipyridyl on bis(benzylsulfinyl)methane complex and luminescence mechanism

A novel ternary complex, Tb₂L₄·L′·(ClO₄)₆·8H₂O, has been synthesized using bis(benzylsulfinyl)methane as the first ligand L and 2,2′‐dipyridyl as the second ligand L′. The ternary complex was characterized by element analysis, molar conductivity, coordination titration analysis, infrared, thermogravimetric‐differential scanning calorimetric and ultraviolet spectra. The results indicated that the composition of the complex was Tb₂L₄·L′·(ClO₄)₆·8H₂O (L = C₆H₅CH₂SOCH₂SOCH₂C₆H₅; L′ = Dipy). Fourier transform infrared results revealed that the perchlorate group was bonded with the Tb(III) ion by the oxygen atom, and the coordination was bidentate. The fluorescent spectra illustrated that the complex displayed characteristic fluorescence in the solid state. After the introduction of the second ligand, 2,2‐dipyridyl, the relative emission intensity and fluorescence lifetime of the ternary complex Tb₂L₄·L′·(ClO₄)₆·8H₂O were enhanced compared to the binary complex TbL_2.5(ClO₄)₃·3H₂O. This indicated that the presence of both organic ligand bis(benzylsulfinyl)methane and the second ligand 2,2‐dipyridyl could sensitize the fluorescence intensity of Tb(III) ion, and introduction of the 2,2‐dipyridyl group resulted in an enhancement of the fluorescence of the Tb(III) ternary rare earth complex. The strongest characteristic fluorescence emission intensity of the ternary complex was 9.36 times that of the binary complex. The phosphorescence spectra and fluorescence lifetime of the complex were also measured. Copyright © 2014 John Wiley & Sons, Ltd.     

Kinetics of Inhibition of Rabbit Intestine Alkaline Phosphatase by Heteroligand Peroxo Complexes of Vanadium(V) and Tungsten(VI)

The present work was undertaken to examine and compare some biologically important properties of peroxo compounds of V(V) and W(VI) containing biogenic species as ancillary ligand. New anionic peroxovanadate(V) complex of the type Na[VO(O₂)₂(triglycine)]·3H₂O (pV1) and a molecular peroxotungstate(VI) [WO(O₂)₂(triglycine)]·3H₂O (pW1) were synthesized and characterized for the purpose and their stability in solution was ascertained. Studies on kinetics of inhibition of alkaline phosphatase activity by the newly synthesized compounds and series of dipeptide and amino acid containing peroxo complexes of vanadium and tungsten synthesized previously by us viz., Na[VO(O₂)₂(gly-gly)(H₂O)]·H₂O (gly-gly = glycyl-glycine), Na[VO(O₂)₂(asn)]·H₂O (asn = asparagine), Na[VO(O₂)₂(gln)]·H₂O (gln = glutamine), and [WO(O₂)₂(gly-gly)(H₂O)]·3H₂O, revealed that each of these species is a potent mixed-type inhibitor of the enzyme. Significant difference was noted between the peroxovanadium (pV) and peroxotungsten (pW) compounds in terms of their oxidant activity with reduced glutathione.     

Multispectroscopic insight,morphological analysis and molecular docking studies of CuII-based chemotherapeutic drug entity with human serum albumin (HSA) and bovine serum albumin (BSA)

The interaction studies of Cu^II nalidixic acid–DACH chemotherapeutic drug entity, [C₃₆H₅₀N₈O₆Cu] with serum albumin proteins, viz., human serum albumin (HSA) and bovine serum albumin (BSA) employing UV–vis, fluorescence, CD, FTIR and molecular docking techniques have been carried out. Complex [C₃₆H₅₀N₈O₆Cu] demonstrated strong binding affinity towards serum albumin proteins via hydrophobic contacts with binding constants, K?=?3.18?×?10⁵ and 7.44?×?10⁴ M^–1 for HSA and BSA, respectively implicating a higher binding affinity for HSA. The thermodynamic parameters ΔG, ΔH and ΔS at different temperatures were also calculated and the interaction of complex [C₃₆H₅₀N₈O₆Cu] with HSA and BSA was found to be enthalpy and entropy favoured, nevertheless, complex [C₃₆H₅₀N₈O₆Cu] demonstrated higher binding affinity towards HSA than BSA evidenced from its higher binding constant values. Time resolved fluorescence spectroscopy (TRFS) was carried out to validate the static quenching mechanism of HSA/BSA fluorescence. The collaborative results of spectroscopic studies indicated that the microenvironment and the conformation of HSA and BSA (α–helix) were significantly perturbed upon interaction with complex [C₃₆H₅₀N₈O₆Cu]. Hirshfeld surfaces analysis and fingerprint plots revealed various intermolecular interactions viz., N–H····O, O–H····O and C–H····O linkages in a 2–dimensional framework that provide crucial information about the supramolecular architectures in the complex. Molecular docking studies were carried out to ascertain the preferential binding mode and affinity of complex [C₃₆H₅₀N₈O₆Cu] at the target site of HSA and BSA. Furthermore, only for Transmission electroscopy microscopy micrographs of HSA and BSA in presence of complex [C₃₆H₅₀N₈O₆Cu] revealed major protein morphological transitions and aggregation which validates efficient delivery of complex by serum proteins to the target site.

Communicated by Ramaswamy H. Sarma     

Metal complexes of 1-methyl-3,4-diphenylpyrazole,a ligand formed by the reaction between benzil and N,N,-dimethylhydrazine

New complexes of the general formulae MnX₂L₂ (X = Cl,Br), MnBr₂L₃, CoX₂L₂ (X = Cl, Br, I, NCS, NO₃), NiX₂L₂ (X = Cl, NO₃), NiBr₂L₃·H₂O, NiL₂L₄·H₂O, CuCl₂L, CuBr₂L₂·H₂O, Cu(NO₃)₂L₂, ZnX₂L₂ (X = Cl, Br, NO₃, Zn(NCS)₂L₂·H₂O, CdX₂L₂ (X = I, NO₃) and HgCl₂L, where L is 1-methyl-3,4-diphenylpyrazole, have been prepared and characterized by elemental analysis, conductivity measurements, magnetic moments and spectral (¹H-NMR, IR and electronic) studies. The ligands is formed by the reaction between benzil and N,N-dimethylhydrazine. The nitrogen of the >CN bond is the donor atom to the metal ions. The bis-ligand halide complexes are pseudotetrahedral, while the nitrate complexes contain octahedrally coordinated metal ions. The IR spectra of MCl₂L (M = Cu, Hg) are indicative of the presence of both terminal and bridging metal-halogen bonds supporting polymeric structures. The stereochemistry and the nature of the nickel(II) complexes are markedly dependent upon the anions; the chloride complex is pseudotetrahedral, the iodide square planar, the nitrate polymeric octahedral, while the proposed structural formula for NiBr₂L₃·H₂O comprises Nickel(II) atoms present in both square planar and octahedral coordination environments.     

Coordination properties of α-hydroxy carboxylic acids. Part I. Binuclear niobium (V) complex acids and some salts

The conditions of dissolution of freshly precipitated niobium (V) oxide in α-hydroxy carboxylic acids glycolic, lactic, malic and tartaric were investigated. The dissolution is a function of the molar ratio α-hydroxy carboxylic acid/hydrated niobium(V) oxide, pH of the solution, temperature and time. From solutions of α-hydroxy monocarboxylic acids at 2 < pH < 3 the binuclear complexes H₃O[Nb₂O₄(C₂H₂O₃)(C₂H₃O₃)]·H₂O and H₃O[Nb₂O₄(C₃H₄O₃)(C₃H₅O₃)]·H₂O were isolated. Colourless, poorly-crystalline complexes are 1:1 electrolytes and, according to i.r. spectral evidence, the binuclearity in their structures is achieved through oxygen bridges. With α-hydroxy dicarboxylic acids crystalline M[Nb₂O₃(C₄H₃O₅)(C₄H₄O₅)]·nH₂O and poorly crystalline complexes, M₂[Nb₂O₂(C₄H₂O₆)₂]·nH₂O, M = H₃O⁺, NH₄⁺ were prepared as 1:1 electrolytes for the former and 1:2 electrolytes for the latter. Analytical, spectral, conductometric and potentiometric titration data give evidence for binuclear malatoniobate(V) and tartratoniobate(V) anions with bridging complex-forming agents.     

Crystal and molecular structures of cyclomaltoheptaose inclusion complexes with HI and with methanol

β-Cyclodextrin (β-CD; cyclomaltoheptaose; cyclohepta-amylose; C₄₂H₇₀O₃₅) crystallises from aqueous solutions of HI and of MeOH in the form of stout prisms, which are isomorphous to each other with monoclinic space-group P2₁; cell constants for C₄₂H₇₀O₃₅ · 2HI · 8 H₂O: a = 21.25(3), b = 10.28(2), c = 15.30(2) Å, β = 113.25(9)°, and Z = 2; and for C₄₂H₇₀O₃₅ · MeOH · 6.5 H₂O: a = 21.03(3), b = 10.11(2), c = 15.33(2) Å, β = 111.02(9)°, and Z = 2. X-ray counter data were used to determine the structures of both crystals, which belong to the cage type, with β-CD molecules in nearly identical, “round” shapes. In the HI complex, one I^- is located inside, and one outside, the β-CD cavity; in the MeOH complex, the MeOH is within the cavity. The cavity is closed at the O-2,O-3 side by adjacent β-CD molecules, and at the O-6 side by water molecules hydrogen-bonded to the guest and to surrounding β-CD molecules. Interstices between β-CD molecules are filled by water of hydration molecules in distorted co-ordination.     

Synthesis and characterization of 5,5,7,12,12,14-hexamethyl- 1,4,8,11-tetraazacyclotetradecane-N′,N‴-diacetic acid and its transition metal complexes; crystal structure of the nickel(II) monohydrogen bromide monohydrate complex of this macrocycle

The synthesis and characterization of a new 14- membered tetraazamacrocylic ligand 5,5,7,12,12,14- hexamethyl-1,4,8,11-tetraazacyclotetradecane-N′,N‴- diacetic acid (H₂L²) are reported. Cobalt(III),nickel(II) and copper(II) complexes with this ligand were prepared and their IR and visible spectra studied.The molecular structure of the complex NiL²· HBr·H₂O was proved by single-crystal X-ray analysis. The compound crystallizes in the space group P2₁/n, with cell parameters a = 16.7109(13), b = 9.0539(9), c = 17.0277(13) Å, β = 107.46(6)° and Z = 4. The structure was solved by direct and Fourier methods and refined by full matrix least square calculation to R = 0.042 for 4355 observed reflections (I > 3σ(I)). The complex shows a cis-octahedral geometry with the macrocycle coordinated in a folded configuration to four sites around the central nickel atom. The two carboxylate groups of the side chain are on the same side of the approximate plane of the macrocycle.     

Sugar complexes with alkaline earth metal ions. Synthesis,structure, and spectroscopic studies of Mg(II), Sr(II), and Ba(II) complexes of d-glucur

Interaction between D-glucuronic acid and alkaline earth metal ions leads to the formation of the complexes such as M(D-glucuronate)X· nH₂O and M(D-glucuronate)₂ · nH₂O, where M = Mg(II), Sr(II), and Ba(II), X = Cl^? or Br^?, and n = 2–4. Owing to the distinct spectral similarities with the structurally known Ca(D-gluguronate)Br · 3H₂O compound, the metal cations bind to three sugar moieties (through O₆, O₅ of the first, O₆', O₄ of the second, and O₁, O₂ of the third residue) and to two H₂O molecules, forming an eight-coordination geometry around each metal ion, in M(D-glucuronate)X · nH₂O (except for Mg(II) ion, which is six-coordination). The metal ions in M(D-glucuronate)₂-nH₂O show six-coordination in different structural environments. The strong hydrogen bonding network of the free acid is weakened upon metalation and the sugar moiety crystallizes as α-anomer, in these series of metal-sugar complexes.