Three new pseudohalide bridged dinuclear Zn(II), Cd(II) complexes of pyrimidine derived Schiff base ligands: Synthesis, crystal structures and fluorescence studies

One new dinuclear Zn(II) complex, [(N3)Zn(L1)(μ1,1-N3)]2 (1), and a dinuclear Cd(II) complex, [(N3)Cd(L1)(μ1,1-N3)]2 (2), of the potentially tridentate NNN-donor Schiff base ligand N-(4,6-dimethyl-pyrimidin-2-yl)-N′-(1-pyridin-2-yl-ethylidine)-hydrazine (L1) and another dinuclear Cd(II) complex [(NCS)Cd(L2)(μ1,3-NCS)]2 (3) of a similar NNN donor Schiff base ligand, N-(4,6-dimethyl-pyrimidin-2-yl)-N′-pyridin-2-ylmethylene-hydrazine (L2), have been synthesized and characterized by elemental analyses, IR, 1H NMR, fluorescence spectroscopy and single crystal X-ray crystallography. The fluorescence spectral changes observed upon addition of the Zn(II) ion to a mixture of L1 and azide showed high selectivity towards the Zn(II) ion over other metal ions. The ligands L1 and L2 are [1 + 1] condensation products of 2-hydrazino-4,6-dimethyl pyrimidine with 2-acetyl pyridine and pyridine-2-carbaldehyde, respectively. In the complexes 1 and 2 the two Zn(II) and Cd(II) centers are held together by μ1,1-bridged azide ions, while in 3 the two Cd(II) centers are bridged by μ1,3-thiocyanate ions. Complex 1 shows high chelation enhanced fluorescence compared to 2 and 3. All the metal centers have a distorted octahedral geometry.