M.K. Bharty

Ni(II) and Co(III) complexes of 5-methyl-1,3,4-thiadiazole-2-thiol: syntheses, spectral, structural, thermal analysis, and DFT calculation

Two new complexes, [Ni(en)2(mtt)2] (1) and [Co(en)2(mtt)2](mtt) (2) (Hmtt = 5-methyl-1,3,4-thiadiazole-2-thiol and en = ethylenediamine), have been synthesized and characterized by various physicochemical techniques. Complexes 1 and 2 crystallize in monoclinic and orthorhombic system with space groups P 21/n and P 21 21 21, respectively. The molecular structures of 1 and 2 show that the metal ions are six-coordinate bonded through four equatorial nitrogens of two en and two axial nitrogens of mtt ligands. The crystal structures of the complexes reveal that mtt is present in thione form and bound to the metal ion through the thiadiazole nitrogen. The crystal structures of the complexes are stabilized by various intermolecular hydrogen bonding providing supramolecular architecture. Complex 2 is also stabilized by weak π···π interactions occurring between two thiadiazole rings. The bioefficacies of the ligand and complexes have been examined against the growth of bacteria to evaluate their antimicrobial potential. The biological results suggest that 2 is more active than the ligand and 1 against the tested bacteria. The geometries of the ligand and the complexes have been optimized by the DFT method and the results are compared with the X-ray diffraction data. The Co(III) complex exhibits an irreversible Co(III)/Co(II) process while the Ni(II) complex displays quasi-reversible Ni(II)/Ni(III) redox processes with large peak separation as compared to that expected for a one electron process which is thought to be coupled with some chemical reaction. Graphical abstract

Ag(I), Cu(II), Co(III) and Hg(II) complexes and metal-assisted products derived from 4-methyl-piperidine-carbodithioate: syntheses, structures, thermal analyses, redox behaviour and fluorescence properties

Four new complexes [Ag2(4-mpipdtc)2(PPh3)2] (1), [Cu(4-mpipdtc)2] (2), [Co(4-mpipdtc)3]·CHCl3 (3) and [PhHg(4-mpipdtc)] (4) and two new products, bis(4-methyl piperidinethiocarbonyl) disulfide {(4-mpipdtc)2} (5) and (4-methyl-piperidin-1-yl) carbothioylsulfanyl-methyl (4-methyl)-piperidine-1-carbodithioate {CH2(4-mpipdtc)2} (6) have been obtained in this study. The syntheses of compounds 5 and 6 were assisted by Mn(II) and Ag(I) ions, respectively, and were obtained from potassium 4-methyl-piperidine-carbodithioate {K+(4-mpipdtc)−} {where, 4-mpipdtc− = 4-methyl piperidine carbodithioate}. All new compounds have been characterized by elemental analyses, IR, NMR, magnetic susceptibility and single X-ray crystallography techniques. These compounds are stabilized by intermolecular C–H⋯S, S⋯S, C–H⋯π and C–H⋯N interactions. The most interesting feature in complex 4 is that the ligand bound phenylmercury cation is stabilized via intermolecular as well as intramolecular Hg⋯S secondary interactions. Compounds 3 and 5 are highly fluorescent in a solution when compared to the free ligand and emit violet/violet-blue light at 372 and 413 nm upon excitation at 328 and 300 nm, respectively. The course of the thermal degradation of complexes 1–4 have been investigated by TG-DTA, which indicates that metal sulphide is formed as the final residue. The results obtained from the electronic structure calculations at the density functional theory level corroborate our experimental findings obtained from the IR data. Frontier molecular orbital analysis reveals that complexes 1 and 3 are softer and more reactive than complexes 2 and 4. Cyclic voltammetry shows that complex 2 exhibits a reversible Cu(II)/Cu(I) redox process at 0.515 V, whereas the ligand and complexes 1, 3 and 4 show irreversible redox behaviour.

Surface enhanced Raman scattering investigation of two novel piperazine carbodithioic acids adsorbed on Ag and ZnO nanoparticles

In this work piperazine-1-carbodithioic acid (PZCDT) and piperazine-1,4-dicarbodithioic acid (PZbCDT) were synthesized. These analytes PZCDT and PZbCDT have chair conformations, which is expected to give specific surface-enhanced Raman scattering (SERS) effects on individual bands. SERS, UV-Visible, TEM and DFT methods have proved that the dithiocarbamate moiety is a potential and suitable functional group for silver and ZnO nanoparticles (AgNPs and ZnONPs). The enhancement mechanism and enhancement factors in both SERS@AgNPs and SERS@ZnONPs are also discussed. Two new strong bands appear at 1630, 1286 cm−1 with very large intensity in SERS@AgNPs, which signifies the conversion of the C–N bond of the dithiocarbamate moiety into CN bonds. The SERS signatures that are observed are quite different in SERS@AgNPs and SERS@ZnONPs.

N′-[Bis(benzyl­sulfan­yl)methyl­idene]-4-meth­oxy­benzohydrazide

In the title compound, C23H22N2O2S2, the dihedral angles between the 4-methoxy-substituted phenyl ring and the other two phenyl rings are 84.4 (4) and 77.7 (1)°, respectively, while the dihedral angle between the two phenyl rings is 57.5 (2)°. The amino group is not involved in an N—H hydrogen bond. The crystal packing is established by intermolecular C—H⋯O packing interactions involving a relatively rare weak three-center hydrogen bond between the keto O atom and H atoms of the two nearby phenyl rings, which link the molecules into chains running along the a axis. Additional weak intermolecular hydrogen-bond interactions between the 4-methoxy O atom and one of the phenyl rings and provide added stability to the crystal packing.

NNS tridentate thiosemicarbazide and 1,3,4-thiadiazole-2-amine complexes of some transition metal ions: syntheses, structure and fluorescence properties

Abstract The reactions of Zn(II), Mn(II), and Ni(II) acetates with 1-picolinoyl-4-phenyl-3-thiosemicarbazide (Hppts) yielded [Zn(ppts)2]·CHCl3 (3), [Mn(ppts)2]·THF (4), and [Ni(ppts)2]·THF (5), respectively, but HgCl2 gave a cyclized product N-phenyl-5-(pyridin-2-yl)-1,3,4-oxadiazole-2-yl-amine (2). The treatment of Hppts with conc. H2SO4 formed N-phenyl-5-(pyridin-2-yl)-1,3,4-thiadiazole-2-yl-amine (1). Hppts is a nonfluorescent material, but 3, 4 and the cyclized products 1,3,4-oxadiazole/1,3,4-thiadiazole are fluorescent. The cyclized ligand N-phenyl-5-(pyridin-2-yl)-1,3,4-thiadiazole-2-amine (1) formed [Zn(2-Hppt)2(OAc)2] (6) and [Cd2(2-Hppt)2(OAc)2(μ-OAc)2] (7) in which Cd(II) has a binuclear acetate-bridged seven coordinate pentagonal bipyramidal geometry. Complex 7 is also a fluorescent material with maximum emission at 425 nm at an excitation wavelength of 254 nm.

Crystal structure of 5-(furan-2-yl)-N-phenyl-1,3,4-oxa­diazol-2-amine

The title compound, C12H9N3O2, was obtained as a cyclized oxadiazole derivative from substituted thiosemicarbazide in the presence of manganese(II) acetate. The furan ring is disordered over two orientations, with occupancies of 0.76 (2) and 0.24 (2). The dihedral angles between the central oxadiazole ring and the pendant phenyl ring and furan ring (major disorder component) are 3.34 (18) and 5.7 (6)°, respectively. A short intramolecular C—H⋯O contact generates an S(6) ring. In the crystal, inversion dimers linked by pairs of N—H⋯N hydrogen bonds generate R 2 2[8] loops. The dimers are linked by C—H⋯π and π–π interactions [range of centroid–centroid distances = 3.291 (2)–3.460 (8) Å], generating a three-dimensional network.

Mn(II) complexes of N′-(2-methoxybenzoyl)hydrazine carbodithioic acid ethyl ester: synthesis, spectral and structural characterization

Two new Mn(II) complexes [Mn(Hmbhce)2(o-phen)] (1) and [Mn(Hmbhce)2(bpy)] (2) based on N′-(2-methoxybenzoyl)hydrazine carbodithioic acid ethyl ester (H2mbhce) have been synthesized by reacting Mn(OAc)2·4H2O with H2mbhce in the presence of o-phen/bpy. The complexes have been characterized by elemental analyses, magnetic susceptibility measurement, IR, UV–Vis and single crystal X-ray data. Both complexes [Mn(Hmbhce)2(o-phen)] and [Mn(Hmbhce)2(bpy)] crystallize in monoclinic system with space group P 21/c and P 21/n, respectively. The single crystal X-ray structures of 1 and 2 show that the Mn(II) center is bonded with two (Hmbhce)− through carbonyl oxygen and deprotonated hydrazinic nitrogen, plus two nitrogen atoms from one o-phen/bpy co-ligand. The crystal structures of complexes 1 and 2 are stabilized by weak intramolecular N–H···O hydrogen bonding and C–H···π interactions giving supramolecular architectures.

Nickel(II) and copper(II) complexes of 5-o-tolyl-[1,3,4]-oxadiazole-2-thione and ethylenediamine: syntheses, spectral, and structural characterization

The reaction of potassium [N′-(2-methyl-benzoyl)-hydrazinecarbodithioate [K+(H2L)−] with metal acetate yielded M(H2L)2 (M = Ni, Cu), which on reaction with excess ethylenediamine (en) formed mononuclear mixed ligand complexes [Ni(en)2(tot)2] (1) and [Cu(en)2](tot)2 (2). The complexes have been characterized by elemental analyses, IR, magnetic susceptibility, and electronic spectral studies. Molecular structures of [Ni(en)2(tot)2] (1) and [Cu(en)2](tot)2 (2) showed 5-(o-tolyl)-[1,3,4]-oxadiazole-2-thione coordinated through oxadiazole nitrogen in 1 and ionically bonded via thiol sulfur in 2.

Crystal structure of N′-[bis­(ethyl­sulfan­yl)methyl­idene]-2-hy­droxy-4-meth­oxy­benzohydrazide

In the title compound, C13H18N2O3S2, the amide group is in the plane of the benzoyl ring with a C—N—N—C torsion angle of 177.63 (12)°. The two dithioate groups are in an anti conformation [torsion angles = 173.68 (8) and −9.98 (10)°]. An intramolecular N—H⋯O hydrogen bond is observed. In the crystal, an O—H⋯O hydrogen bond and a weak C—H⋯O contact involving the same acceptor atom generate an S(6) ring motif and give rise to chains along [010].

Square planar Ni(II) complexes of acetone N4-phenyl-thiosemicarbazone and in situ generated benzoyl thiosemicarbazide ligands: synthesis, spectral and structural characterizations, thermal behaviour and electrochemical studies

Two novel square planar complexes [Ni(Hapt)2] (1) and [Ni(btsc)] (2) have been synthesized from acetone N4-phenyl-thiosemicarbazone (Hapt) and benzoyl-3-thiosemicarbazide (Hbtsc) by the reaction of nickel(II) salt. The ligand and complexes have been characterized by various physicochemical methods. Complexes 1 and 2 crystallize in the monoclinic and orthorhombic systems with space group C2/c and Pbcn, respectively. In complexes 1 and 2 the nickel centre is coordinated through the nitrogen and sulphur atoms forming a square planar geometry. Complexes 1 and 2 are stabilized via various types of intermolecular interactions. The course of the thermal degradations of complexes 1 and 2 has been investigated by TGA which indicated that a metal sulphide/oxide is formed as the final residue. Cyclic voltammetric studies show that complex 1 exhibits a reversible Ni(II)/Ni(III) redox process at 0.525 V (E1/2 value at 20 mV s−1) while complex 2 shows reversible redox behavior with an E1/2 value of 0.43 V. Furthermore, efficient electrocatalytic properties of complexes 1 and 2 toward the oxidation of hydrazine and methanol are demonstrated after immobilizing the complexes into Nafion films. The electrocatalytic properties may find applications in industry, in methanol sensing and in methanol fuel cells.