Heavy metal ion interactions with deoxy nucleotides. X-ray crystal structures of orthorhombic and monoclinic forms of 2'-deoxy cytidine 5'-monophosphate complexed with Cd(II)

The crystal structures of two polymorphic complexes of Cd(II) with 2'-deoxy cytidine 5'-mono-phosphate (5'-dCMP) are reported and discussed The orthorhombic complex, Cd(5'-dCMP) (H₂O)₂] (1), crystallizes in space group P2₁2₁2₁ with cell dimensions a = 8.422(2), b = 24.428(8), c = 7.292(2) Å, and Z = 4, the monoclinic complex, Cd₂(5'-dCMP)₂(H₂O)₂]·3H₂O (2), crystallizes in space group C2 with a = 30.809(9), b = 5.369(2), c = 25.126(8) Å, β = 127.61(2)°, and Z = 4 Structure (1) has been solved by Patterson and Fourier methods, and structure (2) has been deduced from its isomorphous ribo-analog (J.K. Shiba and R. Bau, Inorg.Chem. 17, 3484 (1978)); and both have been refined by full-matrix least-squares methods to final R values of 0.052 for (1) and 0.103 for (2) using, respectively, 1273 and 2287 independent reflections. The orthorhombic complex (1) is three-dimensionally polymeric, with the Cd atom bound in a distorted octahedral arrangement to the cytosine base at N(3) and O(2) Cd-N(3) 2.29(1) and Cd-O(2) 2.64(1) Å], to two phosphate oxygens of different nucleotide molecules, and to two water molecules, each phosphate group links two Cd atoms, thereby producing an infinite -Cd-O-P-O-Cd-]_n spiraling column, which is additionally interconnected to neighboring columns via nucleotide bridges to give a layer-like polymeric structure. The monoclinic complex (2), which includes two crystallographically independent Cd(5'-dCMP) (H2O)] units, is also three-dimensionally polymeric, with each Cd atom bound in a distorted pentagonal bipyramidal arrangement to N(3) and O(2) of the base Cd-N(3) 2.35_av and Cd-O(2) 2.73_av Å], to four phosphate oxygens of three different nucleotide molecules, and to a water molecule, each phosphate group binds to three Cd atoms, thereby creating an infinite cross-linked spiral of sequences -Cd-O-P-O-Cd-]_n and -Cd-O-Cd-]_n that is further connected to adjacent spirals via nucleotide bridges to form large