Ln–Cd heterometal organic–inorganic hybrid materials based on diverse Ln–Cd oxo-cluster chains: syntheses, structures and visible luminescence

Abstract

Three novel Ln–Cd heterometal organic–inorganic hybrid materials, [LnCd(phen)(ox)_1.5(SO₄)(H₂O)₂]·H₂O (type I: Ln = Sm 1a; Eu 1b; phen = 1,10-phenanthroline; H₂ox = oxalic acid) and [EuCd₂(Meimdc)₂(Ac)(H₂O)₂]·H₂O (type II: 2; H₃Meimdc = 2-methyl-imidazole-4,5-dicarboxylic acid; HAc = acetic acid) have been successfully synthesized under hydrothermal conditions. The type I compounds are the first examples of Ln–Cd heterometal organic–inorganic hybrid sulfate–carboxylates with a lattice bilayer structure. The extended structure of type II consists of EuCd(Meimdc) and Cd₂(Meimdc) helices cross-linked through Ln–Cd oxo-cluster chains, showing a 3D microporous architecture with left-/right-handed helical tubes (L1/R1) and channels (L2/R2) along the b axis. The luminescence properties of complexes 1b and 2 exhibit the characteristic emission bands of Eu³⁺ ions. The photoluminescence spectra of 1b and 2 show characteristic line-splitting at room temperature, depending on the site-symmetry of Eu³⁺ ions in the complexes.