A novel coordination polymer of Cull with flexible ligands, namely, [Cu-3(mal)2(di-2-pyridlyktone)21 (1, H(2)mal = maleic acid), was synthesized and characterized by single-crystal X-ray diffraction, thermogravimetric analyses, elemental analysis and IR spectroscopy. The structure indicates that the complex crystallizes in monoclinic, space group P2(1)/c with a = 10.268(2), b = 17.737(3), c = 8.038(1) angstrom, beta = 98.275(2)degrees, V = 1448.6(4) angstrom(3), Z = 2, D-c = 1.883 Mg.m(3), mu = 2.260 mm(-1), F(000) = 826, and the final R = 0.0321 and wR = 0.0820. In 1, three Cull centers (Cu(1), Cu(2), Cu(1A)) are bridged by two uncommon mu(3)-bridging H2mal ligands, furnishing a centrosymmetric trimetallic unit. Via further Cu-O-COO(-) coordination interactions, extention of these trimetallic units in two directions gives rise to an infinite corrugated 2D layer. In addition, thermal stability and electrochemistry of 1 were studied.