Comprehensively Understanding Isomorphism and Photoluminescent Nature of Two-Dimensional Coordination Polymers of Cd(II) and Mn(II) with 1,1′-Ethynebenzene-3,3′,5,5′-tetracarboxylic Ligand

Abstract

Four isomorphic two-dimensional (2D) homo- and heterometallic coordination polymers (CPs), [(CdxMn1–x)3(HEBTC)2(DMSO)6] with x = 1 (1), 1/3 (2), 0.5 (3), and 2/3 (4) were prepared by conventional one-pot self-assembly approach, using Cd2+ or mixtures of Cd2+ and Mn2+ with 1,1′-ethynebenzene-3,3′,5,5′-tetracarboxylic (H4EBTC) under solvothermal conditions. The crystal structures of four isomorphic CPs are composed of center-symmetric trinuclear metal clusters building units linked by HEBTC3– ligands, extending into (3, 6)-connected topological 2D nets. Four CPs are isomorphic to the Mn–CP, [Mn3(HEBTC)2(DMSO)6], we recently reported. The solid-state photoluminescence of 1–4 shows dual emissions at ambient condition, where the emission bands centered at ca. 390 and 562 nm in 1 are assigned to the fluorescence and phosphorescence within HEBTC3– ligand, respectively; however, the emission bands centered at around 397 and 470 nm in 2–4 are attributed to fluorescence, corresponding to electron transition within HEBTC3– ligand and MLCT transition between HEBTC3– ligand and Mn2+ ion. In addition, the origin of isomorphism between 1 and Mn–CP is also discussed.