Syntheses, crystal structures, photoluminescent and magnetic properties of complexes of zinc(II) and copper(II) with Schiff-base ligands derived from 2,6-diacetylpyridine

Two Schiff-base compounds, 2,6-diacetylpyridine bis(benzoylhydrazone) (abbr. DAPBH) and 2,6-diacetylpyridine bis(benzenesulfonylhydrazide) (abbr. DAPBSH), have been synthesized and characterized. The compound DAPBH reacted with zinc(II) and copper(II) nitrates to give the corresponding complexes 1 and 2; the reaction of DAPBSH with zinc(II) acetate and copper(II) nitrate produced complexes 3 and 4. Single crystal structural analysis revealed that 1 contains novel heptacoordinated zinc(II) species and the copper(II) ion in the crystal structure of 2 shows a rare heptacoordinated pentagonal bipyramidal geometry. Complexes 1 and 3 emit intense luminescence in solution, and a solvent dependent luminescent feature is observed for 1. In the solid state, complex 3 emits weak luminescence under 365 nm excitation from an ultraviolet lamp. Variable-temperature magnetic susceptibility measurements revealed that there are antiferromagnetic exchange interactions between the neighboring spins in 2 and 4.