Inorganic-organic hybrid compounds: synthesis and structures of new metal organic polymers synthesized in the presence of mixed dicarboxylates

A hydrothermal reaction of a mixture of 1,2-dicyanobenzene (1,2-DCB), 1,4-benzene-dicarboxylic acid (1,4-BDC) along with the corresponding lanthanide salts at a pH of 5, gives rise to a new series of carboxylate coordination polymers, [M-2(H2O)(4){(1,2BDC)(2)(1,4BDC)}], (M = La, Pr, Gd, Dy, and Y), which are three-dimensional in structure. The 1,2-DCB oxidized to the corresponding dicarboxylic acid, phthalic acid (1,2-BDC), during the reaction. The structures are of two types with the larger La and Pr lanthanides forming type-1 and the smaller ones, Gd, Dy, and Y, forming type-2. While La and Pr have an idealized D-3h triply capped trigonal prism coordination environment, Gd, Dy, and Y have a distorted dodecahedral arrangement with respect to the oxygen atoms. The three-dimensional structure consists of a column of M atoms connected through the 1,2-BDC, and is cross-linked through 1,4-BDC giving rise to rhombic one-dimensional channels. The water molecules, bound to the M atoms, project into the channels. The compounds also illustrate the lanthanide contraction principle. The compounds have been characterized using powder X-ray diffraction, TGA, IR, and photoluminescence measurements. Our continuing investigations clearly reveal that related compounds can be formed with all the rare earth metal ions. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.