Synthesis, spectral and cyclic voltammetric studies on (4,4′-bipyridyl)bis(di(2-hydroxyethyl)dithiocarbamato)zinc(II) and (4,4′-bipyridyl)bis(bis(N-methyl, N-ethanoldithiocarbamato)zinc(II) and their X-ray crystal structures

Synthesis, spectral and cyclic voltammetric characterization of [Zn-2(deadtc)(4)(4,4 ' -bipy)] (1) (deadtc = di(2-hydroxy- ethyl)dithiocarbamate anion) and [Zn-2(nmedtc)(4)(4,4 ' -bipy)] (2) (nmedtc = N-methyl, N-ethanoldithiocarbamate anion) are reported, The single crystal X-ray structures of the adducts have also been determined. IR spectra of complexes 1 and 2 show the thioureide v(C-N) bands at 1480 and 1489 cm(-1), respectively which are lower than the values observed for the parent dithiocarbamates. 4 reduction in the thioureide stretching frequency is due to the increase in coordination around the zinc ion and the resultant increase in electron density. The charge transfer transitions are observed in the region 260-320 nm. The X-ray crystal structures show that the two adducts are dimeric in nature. The zinc ions are five coordinated with the ZnS4N coordination environment in both complexes. Both adducts have two short Zn-S bonds which are close to those observed in the respective parent dithiocarbamate. The asymmetry introduced in Zn-S bond lengths in both adducts is due to the coordination of nitrogen from the 4,4 ' -bipyridine moiety. The Zn-N distances are 2.072(4) and 2.054(8) Angstrom for compounds 1 and 2, respectively. In complex 1, two sets of thioureide C-N distances are observed; one set averages to 1.328(5) Angstrom and the other which is longer, averages to 1.346(6) Angstrom. In complex 2 the thioureide C-N distance (mean of C(6)-N(7) and C(12)-N(13)) is 1.339(48) Angstrom) indicates the partial double bond nature. However, a longer C-N distance {C(6)-N(7)' :1.374(75) Angstrom) is also observed due to the disorder associated with the aliphatic chain of the ethanolic group on dithiocarbamate. All the C-S distances are symmetric in both complexes. Two of the C-S distances, namely S(3)-C(6) (1.702(5) Angstrom) in complex 1 and S(2)-C(6) (1.706(11) Angstrom) in 2, are different. The cyclic voltammetric studies show clearly the presence of excess electron density on the zinc ions in both adducts compared to the parent dithiocarbamates. (C) 2001 Elsevier Science B.V. All rights reserved.