Structure of di(salicylaldehyde benzoylhydrazonato) zinc (II), an unusual staircase polymeric structure formed via E → Z isomerization on complexation

A bicomplex of salicylaldehyde benzoylhydrazone (SBH) with Zn(II) was synthesized in ethanol and single crystals were obtained in DMSO. The compound crystallizes in the orthorhombic system with the space group Pna2 1 (33) and crystal data: a = 22.573(3) A, b = 6.1208(5) A, c = 17.881(2) A, V = 2470.5(5) A 3 , Z = 4, d(calc) = 1.462 g.cm -3 , (2633 reflections with I > 2σ(I): final R = 0.0509; R w = 0.1099). The asymmetric unit is a nearly planar bicomplex built up from one Zn atom linked to two monodeprotonated SBH ligands. The compound can be described as formed of chains extended along the b axis. This linear polymeric character results from the linking of each asymmetric unit to two neighbouring ones via four (2 x 2) covalent Zn-O bonds involving three Zn atoms and four phenolic oxygens. These covalent bonds are related to the very unusual Z configuration of the ligand. The three-dimensional cohesion of the compound is obtained by van der Waals forces between the polymeric chains.