Three resorcin[4]arene-based lanthanide-coordination polymers with multifunctional photoluminescence sensing properties

Abstract

By utilizing a novel octacarboxylate-functionalized resorcin[4]arene as organic linkers, three lanthanide-coordination polymers, namely, [(CH₃)₂NH₂][Ln₂(HL)(H₂O)₇]·2H₂O (Ln = Tb (1), Eu (2) and Gd (3), H₈L = 2,8,14,20-tetra-pentyl-4,6,10,12,16,18,22,24-octa-carboxymethoxy-resorcin[4]arene) have been solvothermally synthesized and structurally characterized. Isostructural 1–3 display unique two dimensional sandwich-based layers built with Ln³⁺ cations and bowl-shaped HL⁷⁻ anions. Remarkably, 1 and 2 produce intensive green and red emissions respectively and long lifetimes thanks to the antenna effect of HL⁷⁻ anions. The energy level testing of 3 indicates that the newly designed ligand H₈L has a very efficient intersystem crossing process. More importantly, luminescent investigations reveal that 1 and 2 can selectively detect N,N′-dimethylformamide and Fe³⁺ ions with turn-on-type and turn-off-type responses, respectively.