Influence of co-ligands in synthesis, photoluminescence behavior and catalytic activities of zinc complexes of 2-((E)-((pyridin-2-yl)methylimino)methyl)phenol.

Four new zinc(II) complexes of a tridentate Schiff base ligand 2-((E)-((pyridin-2-yl)methylimino)methyl)phenol (HL), namely [Zn2L2Cl2] (1); [Zn2L2Br2] (2); [ZnL(SCN)(MeOH)] (3) and [Zn2L(OAc)3(MeOH)] (4) were synthesized with the view to study the role of co-ligands in controlling the structural diversity, photoluminescence property and catalytic activities. The complexes were characterized through common physicochem. techniques as well as by x-ray single crystal structural anal. All of them display interesting co-ligands mediated photoluminescence property the origin of which may be attributed due to ligand to metal charge transfer (LMCT) and the order of photoluminescence efficiency is 3 > 4 > 1-2. Catecholase and phosphatase activities of the complexes were studied in DMF medium using 3,5-di-tert-butylcatechol (3,5-DTBC) and 4-nitrophenylphosphate as substrates, resp. Co-ligands have prominent role on phosphatase activity of the complexes where the order of activity in terms of kcat value is 4 > 1 > 2 > 3. Only complex 4 is active in catalyzing the aerobic oxidn. of 3,5-DTBC. The presence of readily labile solvent mol. in one of the zinc centers of complex 4 perhaps takes the key role for initiating substrate-Zn interaction and thereby the activity. Radical pathway is the probable reason behind the catecholate activity as is evident from EPR study. Solid state thermal anal. suggests that ZnO is the thermally stable end product for complexes 1, 2 and 4, whereas it is ZnS in case of complex 3. [on SciFinder(R)]