Two Cadmium Coordination Compounds with 5‐Sulfonyl‐1,2,4‐benzenetricarboxylate Ligand: Syntheses, Structures, and Photoluminescence

Abstract

Two new cadmium(II) coordination compounds, [Cd4(SBTC)2(2,2′‐bpy)6(H2O)4](2,2′‐bpy) (1) (2,2′‐bpy = 2,2′‐bipyridyl) and {[K2Cd(SBTC)(H2O)4](H2O)2}n (2), were synthesized using a novel ligand of 5‐sulfonyl‐1,2,4‐bezenetricarboxylic acid (H4‐SBTC) featuring three carboxylate groups and one sulfonate group stationed on a phenyl central motif. Compound 1 is a discrete tetranuclear [Cd4(SBTC)2(2,2′‐bpy)6(H2O)4] structure with a solvated 2,2′‐bpy molecule, wherein the four cadmium ions are bridged by two μ3‐SBTC4– ligands. The discrete tetranuclear [Cd4(SBTC)2(2,2′‐bpy)6(H2O)4] motif is extended into a three‐dimensional (3D) supramolecular framework through hydrogen bonds and π–π interactions. In compound 2 the cadmium ions and potassium ions are interconnected by the SBTC4– ligands and bridging water molecules to give a complex 3D structure. The 3D structure is constructed by a rare 3D inorganic cadmium‐potassium‐oxide framework, in which the cadmium and potassium ions are bridged by the sulfonate groups and bridging water molecules. In the solid state, compounds 1 and 2 exhibit photoluminescence with emission maximum at 380 and 445 nm, respectively.

A Zn(II) Coordination Polymer for Fluorescent Turn-Off Selective Sensing of Heavy Metal Cation and Toxic Inorganic Anions

“…The free Hatyha ligand demonstrates the maximum emission centered at 382 nm when excited at 282 nm. The band may be originated from π → π * and/or n → π * transitions [ 27 ]. The luminescent band of CP 1 displays maximum emission at 390 nm ( λ ex = 292 nm).…”

“…Considering the d 10 electron configuration of Zn(II), it is difficult to be oxidized or reduced. Therefore, the emission may result from neither ligand-to-metal charge transfer nor metal-to-ligand charge transfer, but the fluorescence emission of CP 1 can be attributed to intraligand π → π * and/or n → π * charge transfer [ 27 ]. In addition, the emission band of CP 1 indicates red-shift of 8 nm in comparison with those of free Hatyha ligand.…”