A Two-Dimensional Zinc(II)-Schiff Base Coordination Polymer Formed by Six-Membered Metallacyclic Repeating Motif: Structural Aspects, Thermal and Photophysical Properties

A dicyanoamide-bridged 2D polynuclear zinc(II) complex having formula [Zr-2(L)(mu-dca-kappa N-1 kappa N-5)(2)](n), 1 has been synthesized using the Schiff base ligand N,N'-bis(salicylidene)-1,3-diaminopentane, (H2L) and sodium dicyanoamide [Na(dca)]. The complex presents a 2D hexagonal structure formed by 1,5-dca singly bridged helical chains connected through double 1,5-dca bridges. The ligand and the complex are well characterized by elemental analyses, IR and UV-vis spectroscopy. Thermogravimetric analysis is performed to investigate the thermal stability of the metal-organic framework. Photoluminescence studies of the Schiff base ligand in methanol and of the zinc(II) complex 1 in solid state show the presence of blue emission. The emission of the ligand occurs from an excited state involving an intramolecular proton-transfer process as a result of keto-enol tautomerisation and the zinc(II) complex emits from a ligand-centered excited state.