Crystal structure and luminescence property of novel three-dimensional network of {Eu2(p-BDC)3(Phen)2(H2O)2}n

The single crystal of a supramolecule, {Eu-2(p-BDC)(3)(Phen)(2)(H2O)(2)}(n) (p-BDC = 1,4-benzenedicarboxylate), with characteristic luminescence of Eu3+ was obtained by means of soft chemistry. The crystal structure determination reveals that each Eu3+ ion is coordinated by five oxygen atoms of p-BDC anions, one oxygen atom from water molecule, and two nitrogen atoms of Phen, respectively, resulting in an eight-coordinated Eu3+ center and a distorted square antiprism coordination polyhedron. Four bridges, two carboxylates of mu(4)-p-BDC and two of mu(3)-p-BDC, connect two Eu atoms into a binuclear unit. Moreover, the mu(3)-p-BDC integrates the binuclear building blocks at the direction of b axis and the mu(4)-p-BDC polymerizes the structure roughly along the direction of the sum vector of axis b and c, respectively, forming two-dimensional layers. Hydrogen bonds between layers make the structure a three-dimensional network. The luminescence spectra measured under 77 K demonstrate the antenna effect of Phen and the D-5(1) --> D-5(0) energy transfer path within Eu3+ ion. Both luminescence spectra and crystal structure lead to the conclusion that the local symmetry around the Eu3+ ion is C, and that more than one Eu3+ ion sites having slight environmental difference are present. (C) 2003 Elsevier B.V. All rights reserved.