Homopiperazine Pt(II) adducts with DNA bases and nucleosides:: Crystal structure of [PtII(homopiperazine)(9-ethylguanine)2](NO3)2

A series of platinum(II) mono- and diadducts of the type [Pt-II(hmp)XCl]NO3 and [Pt-II(hmp)X-2](NO3)(2) (where hmp = homopiperazine and X = adenine, 9-ethylguanine, 7-methylguaninine, cytosine, 1-methylcytosine, or cytidine), have been synthesized and characterized by elemental analysis and by H-1, C-13, and Pt-195 nuclear magnetic resonance spectroscopy. The crystal structure of diadduct [Pt-II(homopiperazine)(9-ethylguanine)(2)](NO3)(2) was determined using a single crystal X-ray diffraction method. In this complex, platinum had a slightly distorted square planar geometry owing to the presence of a geometrically strained 5-membered ring. The two adjacent corners of the platinum plane were occupied by the two amino nitrogens of limp, whereas the other two equatorial positions were occupied by two nitrogen atoms of two 9-ethylguanine. The 9-methylguanine ligands are oriented in a head to tail fashion between 9-ethylguanine and platinum coordination plane possessing approximate C-2 molecular symmetry. (c) 2006 Elsevier Ltd. All rights reserved.