Toward Novel DNA Binding Metal Complexes: Structure and Basic Kinetic Data of [M(9MeG)2 (CH3OH)(CO)3]+ (M = 99Tc, Re)

To study the interaction of the fac-[M(CO)3 moiety (M = Tc, Re) with DNA bases, we reacted [M(OH2)3(CO)3 with 9-methylguanine (9-MeG), guanosine (G), and 2-deoxyguanosine (2dG). Two bases bind to the metal center via the N7 atoms. X-ray structure analysis of [99Tc(CH30H)(9-MeG)2(CO)3 (4) (monoclinic, 12/a, a = 28.7533(14) A, b = 8.0631(4) A, c = 32.3600(15) A, BETA = 91.543(6)°, V= 7499.6(6) A3 Z= 8) and [Re(OH2)(9-MeG)2(00)33-" (7) (monoclinic, P2 n, a = 12.2873(11) A, b = 16.0707(13) A, c= 14.1809(16) A, beta= 103.361(12)°, V= 2724.4(5) A Z = 4) reveals that the two bases are in a head-to-tail (HT) orientation. Kinetic studies show that the rates of substitution of the purine bases are comparable to that of one of the active forms of cisplatin. The bis-substituted complexes are generally less stable than the platinum adducts, and metalation of the bases is reversible.