M.R. Prathapachandra Kurup

Structural studies of six and four coordinate zinc(II), nickel(II) and dioxovanadium(V) complexes with thiosemicarbazones

Three Zn(II) complexes of di-2-pyridyl ketone thiosemicarbazone, an octahedral Ni(II) complex of 2-acetylpyridine hexamethyleneiminyl-3-thiosemicarbazone, and a V(V) complex of 2-acetylpyridine morpholyl-3-thiosemicarbazone were prepared and characterized. Crystal structure of Ni(II) and V(V) complexes are reported. The ligand in the nickel complex is found to coordinate in the thione form with a pseudo octahedral geometry and the vanadium(V) complex has trigonal bipyramidal geometry.

Synthesis, spectral studies and structure of 2-hydroxyacetophenone nicotinic acid hydrazone

Abstract 2-Hydroxyacetophenone nicotinic acid hydrazone (H2ApNH) was synthesized as a part of our work, in search for non-linear optical crystal based on hydrazones, and studied spectroscopically. Complete NMR assignments for the hydrazone was made using COSY homonuclear and HMQC heteronuclear correlation techniques. Solid state reflectance was also studied in order to understand the electronic structure of the synthesized compound. The crystal and molecular structures of H2ApNH were determined. The compound crystallizes into an orthorhombic lattice with a non-centrosymmetric space group Pca21 with two crystallographically unique molecules of in an asymmetric unit. The geometry reveals quasi co planarity in the whole molecular skeleton with localization of the double bonds in the CN–N–CO with an E-configuration.

Synthesis, characterization and physiochemical information, along with antimicrobial studies of some metal complexes derived from an ON donor semicarbazone ligand

Eight new transition metal complexes of benzaldehyde-N(4)-phenylsemicarbazone have been synthesized and characterized by elemental analyses, molar conductance, electronic and infrared spectral studies. In all the complexes, the semicarbazone is coordinated as neutral bidentate ligand. (1)H NMR spectrum of [Zn(HL)(2)(OAc)(2)] shows that there is no enolisation of the ligand in the complex. The magnetic susceptibility measurements indicate that Cr(III), Mn(II), Fe(III), Co(II) and Cu(II) complexes are paramagnetic and Ni(II) is diamagnetic. The EPR spectrum of [Mn(HL)(2)(OAc)(2)] in DMF solution at 77K shows hyperfine sextet with low intensity forbidden lines lying between each of the two main hyperfine lines. The g values calculated for the [Cu(HL)(2)SO(4)] complex in frozen DMF, indicate the presence of unpaired electron in the d(x)(2) - (y)(2) orbital. The metal ligand bonding parameters evaluated showed strong in-plane sigma bonding and in-plane pi bonding. The ligand and complexes were screened for their possible antimicrobial activities.

Synthesis and spectral investigations of vanadium(IV/V) complexes derived from an ONS donor thiosemicarbazone ligand

Four oxovanadium and one dioxovanadium complex with 2-hydroxyacetophenone N(4)-phenylthiosemicarbazone (H(2)L) which are represented as [VOLphen].2H(2)O (1), [VOLbipy] (2), [VOLdmbipy] (3), [VOL](2) (4) and [VO(2)HL].CH(3)OH (5) have been synthesized and characterized by elemental analyses, electronic, infrared and EPR spectral techniques. In all the complexes 1-4 the ligand coordinates through phenolic oxygen, azomethine nitrogen and thiolate sulfur. But in complex [VO(2)HL].CH(3)OH, coordination takes place in thione form instead of thiolate sulfur. All the complexes except [VO(2)HL].CH(3)OH are EPR active due to the presence of an unpaired electron. In frozen DMF at 77K, all the oxovanadium(IV) complexes show axial anisotropy with two sets of eight line patterns.

Preparation, magnetic and EPR spectral studies of copper(II) complexes of an anticancer drug analogue

Ten new copper(II) complexes of five potential bisthiocarbohydrazone and biscarbohydrazone ligands were synthesized and physico-chemically characterized. The spectral and magnetic studies of compounds are consistent with the formation of asymmetric di-, tri- or tetranuclear copper(II) complexes of deprotonated forms of respective ligands. The variable temperature magnetic susceptibility measurements of all complexes show antiferromagnetic interactions between the Cu(II) centers, in agreement with very broad powder EPR spectra. However, frozen solution EPR spectral studies are found in contradiction with the solid-state magnetic studies and indicate that the complexes are not very stable in solutions; the possible fragmentations of complexes are found in agreement with MALDI MS results. The EPR spectral simulation of most of the compounds is in agreement with the presence of two uncoupled Cu(II) species in solution.

The molecular response of vanadium complexes of nicotinoyl hydrazone in cervical cancers--a possible interference with HPV oncogenic markers.

AIMS Hydrazones belonging to the class of NNO donor Schiff bases are reported to have extensive anti-viral activity and anti-neoplastic activity against certain cancers such as colon cancer, hepatocellular carcinoma and testicular cancer. Here we aim to study the possible effects of two novel nicotinoyl hydrazones on Human papillomavirus (HPV) infected cervical cancers. MAIN METHODS The effect of vanadium complexes on the proliferation of SiHa and HeLa cells was analyzed using MTT assay. The apoptotic potentials of the complexes were assessed by their ability to induce DNA condensation as well as loss of mitochondrial membrane potential. Caspase activity assay and DNA content analysis were performed to understand the mechanism of apoptotic induction. RT-PCR analysis of cell cycle genes, GADD45, p53, p21 and HPV specific oncogenes, E6 and E7 were used to elucidate the molecular mechanism of the complexes. KEY FINDINGS OVK 49 exhibits an increased apoptosis inducing potential when compared to OVK 89 in HPV16 positive SiHa cells compared to HPV18 positive HeLa. A down regulation for E6 and E7 mRNA transcripts along with the induction of p53 protein in SiHa cells were observed when treated with OVK 49 indicating that OVK 49 might have promising anti-cancer activity against HPV16 positive cervical cancers. SIGNIFICANCE This is the first study demonstrating that vanadium complexes could induce a p53 dependent apoptotic mechanism in high risk HPV16-positive cervical cancers.

Design and characterization of Cu(II) complexes from 2-benzoylpyridine benzhydrazone: Crystallographic evidence for coordination versatility

The syntheses and characterization of six copper(II) complexes of 2-benzoylpyridine benzhydrazone in the form of [Cu(BPB)(2)], [Cu(BPB)Cl].H(2)O, [Cu(BPB)Br], [Cu(2)(BPB)(2)](ClO(4))(2).4H(2)O, [Cu(BPB)N(3)].H(2)O, and [Cu(BPB)NCS].H(2)O.CH(3)OH are reported. The analytical methods used for the characterization of complexes include partial elemental analyses, IR, electronic and EPR spectra, conductivity measurements, magnetic susceptibility measurements and single crystal X-ray diffraction. From the crystal structure, it is clear that the hydrazone adopts the E conformation about the azo bond to attach to the metal through the N(py)-N(azo)-O chelating system. In the EPR spectra of complexes in DMF at 77K four hyperfine quartets in the parallel region could be resolved and a half field signal is observed at 1500 G for complex [Cu(2)(BPB)(2)](ClO(4))(2).4H(2)O in polycrystalline state at 298 K which gives evidence for its binuclear nature indicating a weak interaction between the two Cu(II) ions.

Copper(II) complexes derived from di-2-pyridyl ketone-N4-phenyl-3-semicarbazone: Synthesis and spectral studies

Five copper(II) complexes [CuLCl](2).CuCl(2).4H(2)O (1), [CuLOAc] (2), [CuLNO(3)](2) (3), [CuLN(3)] (4) and [CuLNCS].3/2H(2)O (5) of di-2-pyridyl ketone-N(4)-phenyl-3-semicarbazone (HL) were synthesized and characterized by elemental analyses and electronic, infrared and EPR spectral techniques. In all these complexes the semicarbazone undergoes deprotonation and coordinates through enolate oxygen, azomethine and pyridyl nitrogen atoms. All the complexes are EPR active due to the presence of an unpaired electron. EPR spectra of all the complexes in DMF at 77K suggest axial symmetry and the presence of half field signals for the complexes 1 and 3 indicates dimeric structures.

Salicylaldehyde 4,4'-(hexane-1,6-diyl)thiosemicarbazone.

The title compound, C14H19N3OS, is in the thioketo form, with the thione S and hydrazine N atoms cis with respect to each other so that the S atom is involved in inter- and intramolecular hydrogen bonds simultaneously. Intermolecular C-H...S and C-H...O hydrogen bonds result in one-dimensional polymeric chains of molecules along the a axis. A weak C-H...pi ring interaction binds the polymeric chains together.

Versatile binding properties of a di-2-pyridyl ketone nicotinoylhydrazone ligand: Crystal structure of a Cu(II) complex

Six new copper complexes of di-2-pyridyl ketone nicotinoylhydrazone (HDKN) have been synthesized. The complexes have been characterized by a variety of spectroscopic techniques and the structure of [Cu(DKN)(2)]·H(2)O has been determined by single crystal X-ray diffraction. The compound [Cu(DKN)(2)]·H(2)O crystallized in the monoclinic space group P2(1) and has a distorted octahedral geometry. The IR spectra revealed the presence of variable modes of chelation for the investigated ligand. The EPR spectra of compounds [Cu(2)(DKN)(2)(μ-N(3))(2)] and [Cu(2)(DKN)(2)(μ-NCS)(2)] in polycrystalline state suggest a dimeric structure as they exhibited a half field signal, which indicate the presence of a weak interaction between two Cu(II) ions in these complexes.