TAKING ADVANTAGE OF RIGHT ANGLES IN N1,N7-DIPLATINATED PURINE NUCLEOBASES - TOWARD MOLECULAR SQUARES, RECTANGLES, AND MEANDERS

Di- and trinuclear complexes of trans-a(2)Pt(II) (a = NH3 or NH2CH3) a nd the purine model nucleobases 9-methyladenine (9-MeA), 9-ethyladenin e (9-EtA), 9-methylguanine (9-MeGH), and 9-ethylguanine (9-EtGH) have been prepared and characterized. The following five compounds have bee n studied using X-ray crystallography: trans-[(NH3)(2)Pt(9-EtA-N7)(9-M eGH-N7)](NO3)(2). 1.4H(2)O (1b), trans, rans-{[Cl(NH2CH3)(2)Pt](2)-(9- EtA-N1,N7)}(ClO4)(2) (2), trans, 2)Pt](N1-9-MeA-N7)Pt(NH3)(2)(9-MeGH-N 7)}(ClO4)(3). nH(2)O (a = NH2CH3, n = 1 (3a); a = NH3, n = 1.8 (3b)), and trans, trans, H3)(2)Pt](2)(N1-9-MeA-N7)(2)Pt(NH3)(2)}-(ClO4)(4). H 2O (5). In all diplatinated adenine species (2, 3a, 3b, and 5) the Pt- N(1) and Pt-N(7) vectors are approximately at right angles, therefore making these complexes potential building blocks for molecular squares , rectangles, and meanders. Two open nucleobase quartets, 4 and 6, con sisting of three trans-diamineplatinum(II) entities and four purine nu cleobases (two bridging 9-MeA's and two terminal. 9-MeGH (4) and 9-EtG H (6), respectively) have been isolated and characterized by elemental analysis and H-1 and Pt-195 NMR spectroscopy.