Cyclometallated platinum(II) complexes as luminescent switches for calf-thymus DNA

Intercalation of [Pt-II(dpp-C,N,N')(MeCN)](+) 1 (dpp-C,N,N' = C-deprotonated 2,9-diphenyl-1,10-phenanthroline) and [Pt-2(II)(pby-C,N,N')(2)(mu-dppm)l(2+) 2 (pby-C,N,N') C-deprotonated 6-phenyl-2,2'-bipyridine, dppm = diphenylphosphinomethane) into calf-thymus DNA leads to a dramatic enhancement of the photoluminescence of the platinum(II) complexes (I/I-0 = 271 1, 117 2); a much weaker DNA binding affinity of 2 [K = (4.2 +/- 0.3) x 10(4) dm(3) mol(-1)] than of 1 [K = (1.0 +/- 0.1) x 10(6) dm(3) mol(-1)] is observed.