Subbiah Govindarajan

Acetate and malonate complexes of cobalt(II), nickel(II) and zinc(II) with hydrazinium cation

The hydrazinium(1+) metal acetates and malonate dihydrates of the molecular formula [(N2H5)2M(CH3COO)4] and (N2H5)2[M(OOCCH2COO)2(H2O)2] respectively, whereM=Co, Ni or Zn, have been prepared and characterized by chemical analyses, conductance, magnetic, spectral, thermal and X-ray powder diffraction studies. The magnetic moments and electronic spectra indicate that these complexes are of high-spin octahedral variety. The infrared spectra show that the hydrazinium ions are coordinated in the case of acetate complexes, whereas in the malonate complexes the hydrazinium ions are out side the coordination sphere. These complexes undergo exothermic decomposition in the temperature range 150–450°C to give the respective metal oxide as the final residue. The X-ray powder diffraction patterns of the malonate complexes indicate isomorphism among them.

Preparation and Thermal behaviour of Transition Metal Complexes of 4,5-Imidazoledicarboxylic Acid

Some new transition metal imidazolehydrogendicarboxylate hydrates of empirical formula M(Himdc)2·nH2O (H2imdc=4,5-imidazoledicarboxylic acid), where n=2 for M=Mn, Ni, Zn, Cd and n=3 for M=Co, have been prepared in aqueous solution. The compounds have been characterized by analytical, electronic and IR spectroscopic, thermal analysis and X-ray powder diffraction studies. Electronic spectroscopic data suggest that the Co and Ni compounds are of spin free (high spin) type with octahedral geometry. For these compounds, the IR bands in the region 1750-1710 cm-1 has been assigned to stretching vibrations of the non-ionized carboxylic group, confirming that the ligand is monoionized. IR spectra also suggest the unidentate co-ordination behaviour of carboxylate (vasy =1570 and vsym=1390 cm-1) groups of the imidazoledicarboxylate monoanion. The thermal behaviour of these compounds has been studied by simultaneous TG-DTA techniques. All of these compounds are dihydrates except cobalt which is a trihydrate. Thermal decomposition studies show that they lose two water molecules endothermally in the range 200-270°C to give their anhydrous compounds, indicating that these water molecules are coordinated to the metal. The anhydrous compounds further decompose exothermally in the range 300-620°C to leave the respective metal oxides via the metal oxalate intermediates. Whereas the manganese compound undergoes pyrolytic cleavage in a single step to give the manganese carbonate as the final residue. Isomorphic nature of these compounds is evident from XRD data. Six-coordination for the metal atoms has been proposed based on the thermal analysis, visible and IR spectroscopic results.

Thermal, spectral and magnetic studies on glycine complexes of cobalt(II), nickel(II) and zinc(II) with hydrazine

Hydrazinium metal glycinates [(N2H52M(NH2CH2COO)4] and bis(hydrazine)metal glycinates, [M(NH2CH2COO)2(N2H4)2], whereM=Co, Ni or Zn have been prepared and characterized by chemical analyses, magnetic moments and vibrational and electronic spectra. The thermal behaviour of these compounds has been studied by thermogravimetry and differential thermal analyses. These complexes decompose with high exothermicity giving metal powder as the final residue. The X-ray powder data of each set of complexes show isomorphism among themselves.

Hydrazinium Oxydiacetates and Oxydiacetate Dianion Complexes of Some Divalent Metals with Hydrazine

Hydrazinium oxydiacetate salts of formulae N2H5(Hoda)⋅H2oda, N2H5(Hoda) and (N2H5)2oda (H2oda=oxydiacetic acid) and complexes of the types, M(oda)⋅2N2H4⋅xH2O (where M=Co, Ni and Cd; x=0 for Co and Ni;x=1 for Cd) and Zn(oda)⋅N2H4⋅H2O have been prepared and characterized by analytical, spectral, thermal and X-ray powder diffraction data. IR data document the existence of N2H+5 ion in the simple salts and the bidentate coordination of both hydrazine and dianion in the complexes. Complete decomposition of hydrazinium salts takes place via oxydiacetic acid intermediate. Cobalt and nickel complexes decompose in a single step, whereas zinc and cadmium complexes decompose through hydrazinate intermediates. However, all the metal complexes yield metal oxide as the final residue. Isomorphic nature of the cobalt and nickel complexes is evident from XRD data.

Hexavalent uranium dicarboxylates with hydrazine. Preparation, characterization and thermal studies

The uranium complexes of composition,UO2X⋅N2H4⋅H2O, X=succinate or glutarate, UO2X2⋅N2H4⋅H2O, X=Hadipate, Hpimelate, Hsuberate, Hazelate and Hsebacate and UO2X⋅N2H4, where X=malate and oxydiacetate have been prepared and characterized by analytical, spectral (IR and electronic), thermal and X-ray powder diffraction studies. Hydrazine acts as a monodentate ligand in uranyl succinate, glutarate, malate and oxydiacetate hydrazinates and bidentate in uranyl adipate, pimelate, suberate, azelate and sebacate hydrazinate hydrate complexes. The dicarboxylate anions bind the uranium through uni- and bidentate fashion depending upon the coordination polyhedra. All the dicarboxylate hydrazinate complexes in this series decompose to give U3O8 as the end product through their respective uranyl dicarboxylate intermediates. Malate and oxydiacetate compounds decompose exothermically in a single step. The coordinated water is confirmed from thermal data. The complexes of succinate to sebacate seem to possess hexagonal bipyramidal geometry around uranium, whereas pentagonal bipyramidal geometry has been proposed for both malate and oxydiacetate complexes.

Preparation and thermal reactivity of hydrazinium 2,n-pyridinedicarboxylates (n=3, 4, 5 and 6)

Hydrazinium 2,n-pyridinedicarboxylates of general compositions N2H5HA, (N2H5)2A·H2O and N2H5HA·H2A, where H2A=2,n-pyridinedicarboxylic acid (n=3, quinolinic acid;n=4, lutidinic acid; n=5, isocinchomeronic acid and n=6, dipicolinic acid) have been prepared by the neutralisation of aqueous solution of hydrazine hydrate with the respective acids, in stoichiometric ratios. Formation of these hydrazinium derivatives has been confirmed by analytical, IR spectral and thermal studies. Among these, the monohydrazinium salts are anhydrous whereas the dihydrazinium salts are monohydrated. While lutidinic and dipicolinic acids form all the three types of salts, the quinolinic and isocinchomeronic acids do not form N2H5HA·H2A and N2H5HA, respectively, except the other two types. Infrared spectra of these salts reveal N-N stretching frequencies of the hydrazinium ion in the region 970-950 cm-1. The simultaneous TG and DTA of these salts show that all of them decompose without clear melting and lose hydrazine endothermically between 200 and 280°C, except dihydrazinium isocinchomeronate monohydrate in which half of the hydrazine molecule is lost exothermically, to give pyridinemono- or dicarboxylic acid intermediate which further decomposes exothermically to gaseous products.

New cobalt(II) and nickel(II) complexes of benzyl carbazate Schiff bases: Syntheses, crystal structures, in vitro DNA and HSA binding studies

In the present study, new Schiff base complexes with the composition [M(NCS)2(L1)2]·nH2O, where M=Co (n=0) (1) and Ni (n=2) (2); [M(NCS)2(L2)2], M=Co (3) and Ni (4) as well as [M(NCS)2(L3)2], M=Co (5) and Ni (6); (L1=benzyl 2-(propan-2-ylidene)hydrazinecarboxylate, L2=benzyl 2-(butan-2-ylidene)hydrazinecarboxylate and L3=benzyl 2-(pentan-3-ylidene)hydrazinecarboxylate) have been synthesized by a template method. The complexes were characterised by analytical methods, spectroscopic studies, thermal and X-ray diffraction techniques. The structures of all the complexes explore that the metal(II) cation has a trans-planar coordination environment, the monomeric units containing a six-coordinated metal center in octahedral geometry with N-bound isothiocyanate anions coordinated as terminal ligands. Furthermore, the binding of the two Schiff base ligands to the metal centers involves the azomethine nitrogen and the carbonyl oxygen in mutually trans configuration. The binding interactions of all the complexes with Calf thymus-deoxyribonucleic acid (CT-DNA) and human serum albumin (HSA) have been investigated using absorption and emission spectral techniques. The CT-DNA binding properties of these complexes reveal that they bind to CT-DNA through a partial intercalation mode and the binding constant values were calculated using the absorption and emission spectral data. The binding constant values (~10×106moldm-3) indicate strong binding of metal complexes with CT-DNA. HSA binding interaction studies showed that the cobalt and nickel complexes can quench the intrinsic fluorescence of HSA through static quenching process. Also, molecular docking studies were supported out to apprehend the binding interactions of these complexes with DNA and HSA which offer new understandings into the experimental model observations.

New Schiff bases derived from benzyl carbazate with alkyl and heteroaryl ketones

The condensation reaction of benzyl carbazate with the ketones, viz., dimethylketone, dipropylketone, cyclobutanone, cyclopentanone, cyclohexanone, cycloheptanone, 2-acetylpyridine, 3-acetylpyridine and 4-acetylpyridine, yielded the Schiff bases [benzyl 2-(propan-2-ylidene)hydrazinecarboxylate (1), benzyl 2-(heptan-4-ylidene)hydrazinecarboxylate (2), benzyl 2-(cyclobutanylidene)hydrazinecarboxylate (3), benzyl 2-(cyclopentnylidene)hydrazinecarboxylate (4), benzyl 2-(cyclohexanylidene)hydrazinecarboxylate (5), benzyl 2-(cycloheptanylidene)hydrazinecarboxylate (6), benzyl 2-(1-(pyridine-2-yl) ethylidene)hydrazinecarboxylate (7), benzyl 2-(1-(pyridine-3-yl) ethylidene)hydrazinecarboxylate (8) and benzyl 2-(1-(pyridine-4-yl) ethylidene)hydrazinecarboxylate (9)], respectively. These were all characterized by elemental analysis, FT-IR and NMR (1H and 13C) spectroscopic methods, and in addition, the structures of compounds 4, 8 and 9 have been confirmed by single-crystal X-ray diffraction studies, and their crystal structures are shown to be stabilized by hydrogen bonding. The thermal properties of all the Schiff bases have been studied in air and all of them underwent melting followed by endo- and exothermic decomposition processes to yield an ethanimine (CH3–CH=NH) intermediate which in turn decomposes exothermically to give gaseous products. In a nitrogen atmosphere, these compounds also show similar thermal behavior but with the absence of an intermediate. A docking study of compounds 2, 4 and 9 with human BChE provides useful structural information on their inhibition properties.

Amino­guanidinium hydrogen succinate

The title compound, CH7N4 +·C4H5O4 −, is a molecular salt containing discrete aminoguanidinium and succinate ions. The aminoguanidinium cation is nearly planar, with a maximum deviation of 0.035 (1) Å. The dihedral angle between the aminoguanidinium cation and the succinate anion is 3.35 (6)°. The crystal packing exhibits intermolecular N—H⋯O and O—H⋯·O hydrogen bonds.

Amino-guanidinium hydrogen fumarate.

The title compound, CH7N4 +·C4H3O4 −, is a molecular salt in which the aminoguanidinium cations and fumarate monoanions are close to planar, with maximum deviations of 0.011 (1) and 0.177 (1) Å, respectively. The crystal packing is stabilized by intermolecular N—H⋯O and O—H⋯O hydrogen bonds.