Structure and spectral properties of dinuclear zinc complex containing semicarbazonate ligands

The dinuclear Zn2+ complex [Zn(HSSC)OAc]2·2DMF (H2SSC = salicylaldehyde semicarbazone; HOAc = acetic acid; DMF = N,N-dimethylfomamide) was prepared and structurally characterized by single crystal X-ray. The basic structural unit of the complex is a dinuclear complex [Zn(HSSC)OAc]2 in which the semicarbazone ligand adopts the phenol-imine form. The deprotonated phenol group forms a one-atom bridge between the two zinc centers, and both of the zinc centers are five-coordinated. The local coordination environment of Zn2+ can be approximately considered as square pyramidal. UV spectral studies show that the H2SSC provides strong binding of Zn2+ in a 1:1 ratio in solution. The conditional binding constant of the complex is lg KZn–L = 12.89 ± 0.76 in 0.05 M Tris–HCl buffer at pH 7.4. The H2SSC exhibits an enhanced fluorescence effect by the addition of Zn2+, and affords an excellent selectivity for Zn2+ under physiological conditions.