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

Abstract

The single crystal of a supramolecule, {Eu 2( p-BDC) 3(Phen) 2(H 2O) 2} n ( p-BDC=1,4-benzenedicarboxylate), with characteristic luminescence of Eu 3+ was obtained by means of soft chemistry. The crystal structure determination reveals that each Eu 3+ 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 Eu 3+ center and a distorted square antiprism coordination polyhedron. Four bridges, two carboxylates of μ 4- p-BDC and two of μ 3- p-BDC, connect two Eu atoms into a binuclear unit. Moreover, the μ 3- p-BDC integrates the binuclear building blocks at the direction of b axis and the μ 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 5D 1→ 5D 0 energy transfer path within Eu 3+ ion. Both luminescence spectra and crystal structure lead to the conclusion that the local symmetry around the Eu 3+ ion is C 1 and that more than one Eu 3+ ion sites having slight environmental difference are present.