CRYSTAL AND MOLECULAR-STRUCTURE OF (NITRATO)(1-METHYLCYTOSINE)SILVER(I) - UNUSUAL CROSS-LINKED POLYMER CONTAINING A HEAVY-METAL AND A MODIFIED NUCLEIC-ACID CONSTITUENT

A single-crystal X-ray diffraction analysis on the complex (nitrato)(l-methylcytosine)silver(I) is presented. Crystals of the complex are triclinic with the following crystal data: a = 10.474 (3) A, b = 11.141 (3) A, c = 3.642 (1) A, a = 97.33 (2)°, 13 = 95.82 (2)°, y = 16.16 (2)°, V= 409.2 A3, space group Pi, Z = 2 [for [Ag(C5H7N30)(N03)], mol wt 295.0], Intensity data were collected in the 6-28 scan mode on an automated diffractometer. The structure was solved by Patterson and Fourier methods and refined by full-matrix least squares to an R value of 0.033. The packing motif in the crystal is that of a.dimeric [Ag(l-methylcytosine)(N03)]2 complex with each of the 1-methylcytosine residues doubly cross-linked by two Ag+ ions through the base binding sites N(3) and 0(2). Propagation of this dimeric unit along the crystallographic c axis via a second type of Ag-0(2) bond and base-base overlap yields a two-stranded, cross-linked polymer with the base residues slightly out of register. An attempt is made to relate these observed properties to the binding of Ag(I) to regions of high G-C content in duplex DNA. © 1979, American Chemical Society. All rights reserved.