One complex {[Cd2(phen)2(H2O) 2(C6H5NO2)2] ·(ClO4)n has been synthesized by means of hydrothermal way with 4-pyridinecarboxylic acid(PMDA) and 1,10-phen anthroline(phen) and characterized. It crystallizes in the Monoclinic space group P21/n, with a=1.180 30(14) nm, b=1.362 84(17) nm, c = 1.360 23(16) nm, β=113.554(2)°, V=2.0057(4) nm3, Dc= 1.762 g·cm-3, Z=4, F(000)=1 056. Final GooF=1.048, R1=0.0306, wR2=0.079 3. The crystal structure shows that the cadmium ion is coordinated with three oxygen atoms from two 4-pyridinecarboxylic acid molecu...