Intense greenish phosphorescence emission under ambient conditions in a two-dimensional lead(ii) coordination polymer with a 1,1′-ethynebenzene-3,3′,5,5′-tetracarboxylate ligand

Abstract

In this study, a new two-dimensional Pb²⁺-based coordination polymer (CP), [Pb₂(EBTC)(DMSO)₃] (1), where H₄EBTC is 1,1′-ethynebenzene 3,3′,5,5′-tetracarboxylic acid, was synthesized under solvothermal conditions. Structural analysis reveals that 1 crystallizes in the monoclinic space group C2/m, where two crystallographically different Pb²⁺ ions show a coordination geometry of bicapped trigonal prisms that are connected to a double-chain by the EBTC⁴⁻ ligands through carboxylate groups along the b-axis direction, and where successive double chains are held together to form a 2D layer via the Pb1 and Pb2 bicapped trigonal prisms sharing one edge or a triangle face along the c-axis direction. Interestingly, CP 1 emitted intense and long-lived greenish phosphorescence in the solid state at ambient conditions, with a quantum yield of 1.5% and a phosphorescence lifetime of 4.17 ms, and the emission mainly arose from the electron transition within the π-type orbitals of the EBTC⁴⁻ ligand. The emission bands assignment and photophysical process were further discussed according to the calculation of both the electronic band structures and density of states. This study gives a fresh impetus to achieve coordination polymer-based long-lived phosphorescence materials under ambient conditions.