Luminescent lanthanide(III) carboxylate-phosphonates with helical tunnels

Hydrothermal reactions of lanthanide(III) salts with H(4)PMIDA (N-(phosphonomethyl) iminodiacetic acid) led to seven new isostructural lanthanide(III) carboxylate phosphonates, namely, Ln(HPMIDA)(H2O)(2) center dot H2O (Ln = Gd, 1; Tb, 2; Dy, 3; Y, 4; Er, 5; Yb, 6; Lu, 7). Their structures feature a novel 3D framework. The lanthanide( III) ion is eight-coordinated by a chelating HPMIDA in a tetradentate fashion ( 1 N and 3 O), one carboxylate oxygen and one phosphonate oxygen from two other HPMIDA anions, and two aqua ligands. The HPMIDA anion is hexadentate. It chelates with a Ln( III) ion tetradentatedly and also bridges with two other Ln( III) ions. The phosphonate group is singly protonated. One of the carboxylic groups is unidentate, whereas the other is bidentate bridging. Compound 2 exhibits very strong characteristic emission bands for the terbium( III) ion in the visible region under 380 nm excitation, with the Tb (D-5(0)) lifetime for lambda(ex,em) = 380 and 488 nm being about 1 ms. Compounds 1 and 5 display very broad ligand-centered emission bands in the blue light region.