Hydrothermal synthesis, structure, porosity, and luminescent properties of 3D coordination polymer of holmium with 1,4-phenylenediacetic acid [Ho-2(PDA)(3)(H2O)](n)center dot 2nH(2)O

摘要

Coordination polymer formulated as [Ho-2(P-DA)(3)(H2O)](n)center dot 2nH(2)O having three-dimensional network was hydrothermally synthesized (H(2)PDA is 1,4-phenylenediacetic acid). The polymer crystallizes in the monoclinic space group P 2(1)/c, unit cell parameters: a = 21.7025(2) angstrom, b = 10.03560(10) angstrom, c = 14.03430(10) angstrom, beta = 91.7110(10)degrees (Z = 4), and exhibits a three-dimensional porous framework. The polymer contains two and four crystallographically independent holmium(III) ions and 1,4-phenylenediacetate anions, respectively. The two types of Ho(III) ions adopt an extended zigzag orientation and act as nodes alternately, while three different carboxylate (COO-) groups bridge two adjacent Ho(III) ions. The coordination polymer chains are reinforced by well-directed hydrogen bonds involving guest water molecules. The polymer is mesoporous in nature with average pore size diameter of 5.6 nm. The polymer exhibits intense emission bands in visible region upon excitation at 390 nm. The polymer is thermally robust and undergoes thermal decomposition in well-defined steps.