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

Two new cadmium(II) coordination compounds, [Cd 4 (SBTC) 2 (2,2′‐bpy) 6 (H 2 O) 4 ](2,2′‐bpy) ( 1 ) (2,2′‐bpy = 2,2′‐bipyridyl) and {[K 2 Cd(SBTC)(H 2 O) 4 ](H 2 O) 2 } n ( 2 ), were synthesized using a novel ligand of 5‐sulfonyl‐1,2,4‐bezenetricarboxylic acid (H 4 ‐SBTC) featuring three carboxylate groups and one sulfonate group stationed on a phenyl central motif. Compound 1 is a discrete tetranuclear [Cd 4 (SBTC) 2 (2,2′‐bpy) 6 (H 2 O) 4 ] structure with a solvated 2,2′‐bpy molecule, wherein the four cadmium ions are bridged by two μ 3 ‐SBTC 4– ligands. The discrete tetranuclear [Cd 4 (SBTC) 2 (2,2′‐bpy) 6 (H 2 O) 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 SBTC 4– 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.