Effect of N-salicylidene hydrazide protonation on the solid state structural diversity of its Cu(ii), Ni(ii) and Zn(ii) complexes

Abstract

We present here ten coordination compounds isolated from reactions of divalent metal ions (Cu^II, Ni^II and Zn^II) with the Schiff base ligand H₂L derived from salicylaldehyde and ω-hydroxy carbonic acid hydrazide. Protonation levels of the ligand has played significant roles in affecting the coordination conformations of the metallosupramolecular compounds in solid state. Four kinds of complexes have been obtained: monomeric [M(HL)₂] and dimeric [M₂(HL)₂(X)₂]/[M₂(HL)₂](X)₂ (X = anion) containing monodeprotonated ligand, and polymeric _∞¹M(L) and dimeric [Zn₂L₂] compounds with the doubly deprotonated form of the ligand. The structures of the free ligand H₂L and its complexes [Zn(HL)(H₂L)]·(NO₃)·EtOH (Zn-1a), [Cu₂(HL)₂(NO₃)₂] (Cu-3a), [Cu₂(HL)₂(SiF₆)] (Cu-3b) and [Ni₂(HL)₂(EtOH)(H₂O)](NO₃)₂(Ni-3a) were elucidated by single-crystal X-ray diffraction. The reactivity of [Ni(HL)₂] complex in the presence of a competitive ligand was investigated.