Krishna K. Manar

Intermolecular anagostic interactions in group 10 metal dithiocarbamates

New functionalized homoleptic xanthate and dithiocarbamates of the form [M(L)2] (M = Ni(II), L = L1 (4-methoxyphenethylxanthate) 1, L2 (4-ethoxycarbonylpiperidine-1-dithiocarbamate) 2, L3 (N,N′-difurfuryldithiocarbamate) 3; M = Pt(II), L3, 4, M = Pd(II), L4 (N-benzyl-N′-3-methylpyridyldithiocarbamate) 5) have been synthesized and characterized using microanalyses, and their structures have been investigated by X-ray crystallography. All five complexes are centrosymmetric with the central metal in a distorted square planar structure; the distortion varies in the order Pt > Pd > Ni. In 3, 4 and 5 the ligand framework and crystal packing effects force the methylene proton on the substituents into close proximity with the metal centers, forming intermolecular C–H⋯M (M = Ni, Pt and Pd) anagostic interactions and generating a 1-D polymeric chain; 4 and 5 are the first examples containing Pt and Pd that exhibit such interactions. Similar anagostic interactions are also observed in 2 but are rather weaker. These interactions have been supported by theoretical calculations. The xanthate complex 1 displays unique S⋯S intermolecular interactions leading to a 1-D polymeric chain, while no significant intermolecular interactions involving the metal centres have been found. The supramolecular structures are sustained by weaker O⋯H, S⋯H, C–H⋯π and C–H⋯π (chelate, CS2M) interactions. 1 is weakly conducting (σrt = 1.39 × 10−7 S cm−1) but shows semiconductor behaviour in the 303–363 K range. The platinum complex 4 shows luminescent properties in solution.

Influence of ligand environments on the structures and luminescence properties of homoleptic cadmium(II) pyridyl functionalized dithiocarbamates

Novel homoleptic pyridyl-3(N) functionalised dithiocarbamate complexes having polymeric, [Cd(L)2] (L = L1, C5H4NCH2NCS2CH2C6H5 (1), L2, (C5H4NCH2)2NCS2 (2), L3, C5H4NCH2NCS2CH2C4H3O (3) and L4, C5H4NCH2NCS2CH2C4H3S (4)); dinuclear, [Cd(L)2]2 (L = L5, (C8H6NCH2NCS2CH2NC5H4) (5)) and trinuclear, [Cd(L6)2]3 (L6 = CH3C6H4CH2NCS2CH2C4H3O) (6)) structures have been synthesised and characterized by elemental analysis, IR, UV-vis, and 1H and 13C NMR spectroscopy and their structures have been elucidated by X-ray crystallography. In 1–4, the cadmium(II) ions are six-co-ordinate with two bidentate dithiocarbamate ligands (L1–L4) in an equatorial plane and axially bonded by Py(N) of the dithiocarbamate ligands on adjacent molecules, thus adopting a distorted octahedral geometry (CdS4N2) in 2-D polymeric structures. Complexes 1 and 2 are isomorphous and have similar structures to those of 3 and 4, although they differ significantly in architecture and topology. In 3 and 4, the metal atoms occupy centrosymmetric sites. In marked contrast to these polymeric structures, complex 5 derived from ligand L5 containing a bulky indolyl substituent proved to be a dinuclear complex. In 5, the metal atom has a square pyramidal geometry. As in 1–4, the dithiocarbamate ligand in 5 is uniquely bonded to the metal centres in a μ2,κ3-N,S,S bridging-chelating fashion. Ligand L6 containing furfuryl and tolulyl substituents yielded a spectacular centrosymmetric trinuclear complex 6 with the central metal atom in an octahedral environment and the two outer metal atoms in square pyramidal environments in which the dithiocarbamate ligands are bonded in a μ2,κ2-S,S chelating-bridging and S,S chelating manner within the same molecule. To the best of our knowledge, 1–4 and 5 and 6 are the first examples of 2-D coordination polymeric, dinuclear and trinuclear cadmium dithiocarbamates. All the complexes show bright luminescence emission in the solid state; the coordination polymers 1 and 2 are strongly luminescent.

Effect of functionalities on the crystal structures of new zinc(II) dithiocarbamates: a combined anti-leishmanial and thermal decomposition study

New homoleptic zinc(II) dithiocarbamates, [Zn(L)2] (L = N-ferrocenyl-N-methyl dithiocarbamate (L1) 1, (N-(benzo[d][1,3]dioxol-5-ylmethyl)-N-furfuryl) dithiocarbamate (L2) 2, N-(benzo[d][1,3]dioxol-5-ylmethyl)-(N-benzyl) dithiocarbamate (L3) 3, N-(benzo[d][1,3]dioxol-5-ylmethyl)-(N-methyl) dithiocarbamate (L4) 4, N-ethylmorpholine-(N-4-methoxyphenylmethyl) dithiocarbamate (L5) 5 and N-(benzo[d][1,4]dioxol-6-ylmethyl)-(N-benzylmethyl) dithiocarbamate (L6) 6, have been synthesized and characterized by elemental analyses and spectroscopy (IR, UV-vis, 1H and 13C{1H} NMR). X-ray crystallography revealed different dimeric structures for (1 and 2) and (3, 4, and 5) adopting distorted tetrahedral and TBP/SP coordination geometries, respectively, in which the dithiocarbamate ligands are bonded to the metal centers both in terminal S,S-chelating and μ2,κ2S,S-bridging and μ2,κ2-S,S-chelating–bridging arrangements. 6 is a mononuclear complex showing a distorted tetrahedral geometry. The supramolecular frameworks in these complexes have been sustained by C–H⋯S, C–H⋯O, C–H⋯π, π⋯π, C–H⋯π (ZnCS2, chelate) and H⋯H interactions. The anti-leishmanial activities of the complexes have been screened; 4 and 6 showed potential anti-promastigote and anti-amastigote activities with IC50 values of 0.66 ± 0.22, 1.48 ± 0.10 μg mL−1 and IC50 2.98 ± 0.30, 2.51 ± 0.10 μg mL−1, respectively. Cytotoxicity assays on both complexes showed toxicity on promastigotes but lower toxicity against the RAW 264.7 cell line at different concentrations. All the complexes show luminescence characteristics in CH2Cl2 solution at room temperature arising from the metal perturbed intra-ligand charge transfer (ILCT) states. Their TG analyses show single step decomposition with formation of binary ZnS and ternary FeZn2S3 materials which have been examined by PXRD, SEM and EDAX.

Influence of ligand environment on the structure and properties of silver(I) dithiocarbamate cluster-based coordination polymers and dimers

Luminescent silver(I) homo- and heteroleptic pyridyl functionalised dithiocarbamate (dtc) complexes of the form, [{Ag(L)}4]∞ (L = N-benzyl-N-methylpyridyldtc (L1) 1, bis-(N-methylpyridyl)dtc (L2) 2) and [Ag(L)PPh3]2 (L = L1 (3), L2 (4)) have been synthesized and characterized by elemental analysis, TGA, spectroscopy (IR, 1H, 13C and 31P NMR and UV-Vis) and X-ray crystallography. Complexes 1 and 2 are isomorphous and have a tetranuclear cluster-based coordination polymeric structure. In these tetranuclear silver(I) cluster subunits the four Ag atoms form a distorted tetrahedron. Complexes 3 and 4 are also isostructural and have centrosymmetric structures in which each Ag atom forms a distorted tetrahedral coordination geometry. All complexes are weakly conducting and exhibit semiconductor behaviour. 1–4 are strongly luminescent in solid phase; a correlation between their structure and luminescent properties has been established.

New planar trans-copper(II) β-dithioester chelate complexes: synthesis, characterization, anticancer activity and DNA-binding/cleavage studies

Abstract New planar trans-copper(II) β-dithioester complexes, [Cu(L)2] (L = methyl-3-hydroxy-(3-pyridyl)-2-propenedithioate (L1 in 1), methyl-3-hydroxy-(2-naphthyl)-2-propenedithioate (L2 in 2), methyl-3-hydroxy-3-(p-methoxyphenyl)-2-propenedithioate (L3 in 3), methyl-3-hydroxy-3-(p-fluorophenyl)-2-propenedithioate (L4 in 4), and methyl-3-hydroxy-3-(p-bromophenyl)-2-propenedithioate (L5 in 5)), have been synthesized and characterized by elemental (C, H, N and S) analysis, ESI-MS, IR, and UV-vis spectra. The structures of HL3 and its corresponding complex 3 have been determined by X-ray crystallography. Electrochemical behavior of all complexes has been studied by cyclic voltammetry. All five planar complexes show efficient DNA-binding and DNA (PBR322)-cleavage in a concentration-dependent manner (1 > 3 > 5 > 2 > 4). Cleavage efficiency is enhanced in the presence of H2O2 as well as ascorbic acid. However, the order of increased efficiency of Cu(II) chelates differs in the presence of H2O2 as 4 > 1 > 2 > 3 > 5. Among these complexes, the pyridyl- and methoxy-functionalized 1 and 3 have shown higher self-activating capability in DNA-cleavage. All complexes show significant variation in IC50 on MCF-7 cell line. Additionally, treatment with the complexes gradually increases apoptotic cell death in dose-dependent manner in RAW 264.7 cell line. These findings highlight potential cancer protective nature of these complexes.

Synthesis, characterization, DNA binding and cleavage activity of homoleptic zinc(II) β-oxodithioester chelate complexes

Abstract New homoleptic zinc(II) complexes, [Zn(L)2], where L = methyl-3-hydroxy-(3-pyridyl)-2-propenedithioate L1 1, and methyl-3-hydroxy-(4-pyridyl)-2-propenedithioate L2 2, have been synthesized and characterized by elemental (C, H, and N) analysis, ESI-MS, and (IR, UV–vis, NMR) spectroscopy; the structure of 1 has been deduced by X-ray crystallography. The DNA binding and cleavage activity of the complexes have been studied. The cleavage potential of pBR322 DNA by 1 and 2 has been checked. Complex 1, which contains nitrogen of the pyridine group in the 3-position enhances DNA cleavage potential in the presence of ascorbic acid; however, the complex is protective against DNA cleavage in the presence of DMSO or H2O2. Also, 1 causes cytotoxicity against the MCF-7 breast cancer cell line. The efficient cytotoxic activity and DNA cleavage ability of 1 in the presence of ascorbic acid shows its potential anticancer properties and the need for further investigations of its potential as an anticancer drug.