Synthesis, characterization and crystal structures of a pair of azido-bridged polynuclear Schiff base copper(II) complexes with urease inhibitory activity

A pair of azido-bridged Schiff base copper complexes, [CuL1(& mu;(1,3)-N-3)](n) & BULL; nClO(4)(1) and [Cu-2(L2)(2)(& mu;(1,1)-N-3)(2)] & BULL; 2ClO(4)(2) (L1 = N,N-diethyl-N & PRIME;-(1-pyridin-2-ylmethylidene)ethane-1,2-diamine, L2 = N-isopropyl-N & PRIME;-(1-pyridin-2-ylmethylidene)ethane-1,2-diamine) have been obtained by the same synthetic procedures, but with slightly different Schiff bases. The structures of the complexes have been characterized by IR spectra, elemental analysis, and single crystal X-ray determination. Each Cu atom in the complexes is five-coordinate in a square pyramidal configuration involving the three N atoms of the Schiff base ligand and two N atoms from two bridging azide ligands. The azide ligands adopt end-to-end bridging mode in (1), and end-on bridging mode in (2). The different coordination modes of the azide ligands in the two complexes are assigned to the steric effects of the terminal groups (two ethyl groups for (1) and one isopropyl group for (2)) in the Schiff base ligands. The urease inhibitory activities of the complexes were evaluated. Both of them showed potent inhibition against jack bean urease.