Syntheses and crystal structures of methyl 2-pyridylmethylidenehydrazinecarbodithioate and of its copper(II) complex: Supramolecular arrays exhibiting pseudo-helical arrangement controlled by hydrogen bonding or S center dotcenter dot center dot S contact

A copper(II) complex of the Schiff base methyl 2-pyridylmethylidenehydrazin ecarbodithioate (HNNS), derived from 2-pyridinecarbaldehyde and methyl hydr azinecarbodithioate, was synthesized and characterized by elemental analyse s, IR, UV-vis spectra and cyclic voltammetric measurements, X-Ray diffracti on studies showed that the ligand HNNS (1) crystallizes in the orthorhombic space group Pna2(1), with a = 17.611(2), b = 9.285(1), c = 6.208(1) Angstr om; V = 1015.1(2) Angstrom(3), Z = 4, final R = 0.03 for 1169 independent r eflections. Complex [Cu(NNS)(2)] (2) crystallizes in monoclinic space group P2(1)/c, with a = 11.898(2), b = 9.798(2), c = 18.091(4) Angstrom; beta = 103.18(3)degrees, V = 2053.3(7) Angstrom(3), Z = 4 final R = 0.0505 for 346 0 observed reflections. Intermolecular interactions play important roles in the overall packing of the molecules in the crystal lattice. In 1, an exte nded one-dimensional helical chain is formed via hydrogen bondings (N ... N 2.971 Angstrom), while S ... S contacts (3.485 Angstrom) assemble the heli cal chains in 2. The assembly process of 2 is enantioselective, since the c omplex assumes either the Delta or Lambda enantiomorph due to the mer-confi guration of the unsymmetrical tridentate Schiff base, and the Delta isomer aggregates only with the Delta isomer and the Lambda only with Lambda to gi ve helical structures described as Delta Delta Delta Delta ... and Lambda L ambda Lambda Lambda ..., respectively.