^a Laboratory of Coordination Chemistry, Shenyang Institute of Chemical Technology, Shenyang, Liaoning 110142, China 
^b School of Chemistry, Northeast Normal University, Changchun, Jilin 130024, China

A copper(II) complex of type {[Cu(phen)(py)(H2O)2]?2H2O}n (where phen＝1,10-phenanthroline, py＝pyridine-3,4-dicarboxylate) has been synthesized by a normal temperature volatilization method and structurally determined by single-crystal X-ray crystallography. The crystal belongs to monoclinic system, space group P2(1)/c with the crystal cell parameters of a＝7.5258(4) ?, b＝12.3184(7) ?, c＝21.0000(12) ?, α＝90.00°, β＝98.0720(10)°, γ＝90.00°, V＝1927.53(19) ?3 and Z＝4. The final reliability factors are R＝0.0398 and wR＝0.1138 for 3771 reflections with I＞2σ(I0). Its mode of interaction with DNA and the binding constants have been determined by fluorescence, ultraviolet spectra and viscometry.