Synthesis, Crystal Structures and Spectral Characterization of Trans-Bisaquabis(o Cis-Aquabis(o and Aqua[bis(o-Vanillinato)

Abstract

trans-Bisaquabis(o-vanillinato)copper(II) (I), cis-aquabis(o-vanillinato)copper(II) (II) and aqua[bis(o-vanillinato)-1,2-ethylenediimin]copper(II) (III) complexes were synthesized and characterized by means of elemental analysis, IR and UV-vis spectroscopy, thermal analysis and X-ray diffraction techniques. The coordination geometry around Cu(II) is a octahedral with coordination number of six for I and is a square-pyramidal with coordination number of five for both II and III. In all three compounds, a three-dimensional structure is formed via C-H⋯O hydrogen-bond interactions and intermolecular π-π and π-ring interactions. The compounds I and III have two-dimensional hydrogen-bonded step-chain structure in xz-plane, while compound II has a zigzag chain structure in xy-plane. On the basis of the first DTA<inf>max</inf> of the anhydrous complexes of I and II, the thermal stability sequence is trans-isomer > cis-isomer. This fact should be related with the binding of the ligand. © 2006 Elsevier Ltd. All rights reserved.