The two complexes [Cu(C5H2N2O4)(H2O)3]·2H2O (1) and [Ni(C5H2N2O4)(H2O)4]·H2O (2) were synthesized by self assembly reactions of Cu(NO3)2·3H2O or Ni(CH3COO)2·4H2O with orotic acid (2,6 dioxo 1,2,3,6 tetrahydro 4 pyrimidinecarboxylic acid), respectively. Their crystal structures were determined by single crystal X ray diffraction analyses. Crystallographic data for complex 1: C5H8N2CuO7·2H2O, Mr=307.7, monoclinic P21/n, a=0.57710(1)nm, b=1.76863(6)nm, c=1.09955(4)nm, β=98.600(2)°, V=1.109.63(6)nm3, Z=4 , Dc=1.842g·cm-3, μ(MoKα)=2.010mm-1, F(000)=628, R=0.0436, wR=0.1015, And for complex 2: C5H10N2NiO8·H2O, Mr=302.88, orthorhombic Pbcn, a=2.0763(1)nm, b=1.69355(9)nm, c=0.73478(4)nm, V=2.5837(2)nm3, Z=8, Dc=1.557g·cm-3, μ(MoKα)=1.538 mm-1, F(000)=1248, R=0.0545, wR=0.1305. The X ray analyses revealed that the Cu? and Ni? atoms are both coordinated by carboxylic O atom and contiguous N atom of the pyrimidine ring. In complex 1 the Cu? atom has a slightly distorted square pyramid coordination environment with additional three water molecules, while in complex 2 the Ni? atom adopts a slightly distorted octahedral geometry with additional four water molecules. The three dimensional frameworks of the two complexes are formed by intermolecular hydrogen bonding interactions. CCDC: 1, 204881; 2, 204882.
