摘要：The two complexes [Cu(C5H2N2O4) (H2O)3] @ 2H2O (1) and [Ni(C5H2N2O4) (H2O)4] @ H2O (2) were syn-thesized 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, mono-clinic P21, a=0.57710(1) nm, b=1.76863(6) nm, c=1.09955(4) nm, 3=98.600(2)°, V=1.109.63(6) nm3, Z=4, Dc=1.842g@cm-3, μ(Mo Kα)=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) =1.538mm-1, F(000) =1248, R = 0. 0545, wR = 0. 1305. The X-ray analyses revealed that the Cu (Ⅱ) and Ni (Ⅱ) atoms are both coordi-nated by carboxylic O atom and contiguous N atom of the pyrimidine ring. In complex 1 the Cu (Ⅱ) atom has aslightly distorted square pyramid coordination environment with additional three water molecules, while in complex2 the Ni (Ⅱ) atom adopts a slightly distorted octahedral geometry with additional four water molecules. Thethree-dimensional frameworks of the two complexes are formed by intermolecular hydrogen bonding interactions.