Synthesis, Structure, and Luminescent Properties of the Cadmium Metal-Organic Coordination Polymer Based on 4,6-di(1,2,4-triazol-1-yl)-2,1,3-Benzoxadiazole

Abstract

4,6-Di(1,2,4-triazol-1-yl)-2,1,3-benzoxadiazole (4,6-Tr₂bod) is obtained for the first time with a 34% yield by the heteroarylation reaction with 4,6-dibromo-2,1,3-benzoxadiazole and 1H-1,2,4-triazole in the superbasic K₃PO₄/DMSO medium. By the interaction of the obtained 4,6-Tr₂bod ligand with thiophendicarboxylic acid (H₂TDC) and cadmium nitrate, 2D metal-organic coordination polymer (CP) {[Cd(TDC)(4,6-Tr₂bod)(H₂O)]·H₂O·DMF}_n is formed with a 39% yield. The obtained compounds are characterized by IR and NMR spectroscopy and the elemental analysis. By the single crystal X-ray diffraction analysis of CP formed it is found that the polymer crystallizes in the triclinic crystal system with space group \(P\bar{1}\) and has a 2D layered structure where chains of cadmium cations and thiophene-dicarboxylate anions are bridged by 4,6-Tr₂bod ligands. From the thermogravimetric analysis data it follows that this CP is thermally stable up to 335 °C. The study of the luminescent properties reveals that upon 320 nm excitation, the polymer demonstrates intense photoluminescence with the maximum at 502 nm, a quantum yield of 16%, and the excited state lifetime of 8.9 ns.