Functional mono- and dinuclear peptide complexes featuring chemospecific κS- or η6-coordination of organometallic half-sandwich fragments
作者:Ralf Stodt、Susan Gencaslan、André Frodl、Claudia Schmidt、William S Sheldrick
DOI:10.1016/s0020-1693(03)00345-1
日期:2003.11
Treatment of the dipeptides H-Tyr-Trp-OH, H-Trp-Tyr-OH, H-Trp-Phe-OH and H-Phe-Tyr-OH with [(T,(6)- cymene)Ru(acetone)(3)].(CF3SO3)(2) (1) in CF3COOH leads to chemospecific eta(6)-coordination in the order of electron-donating ability Trp > Tyr > Phe in respective complexes of the type [(eta(6)-cymene)Ru(eta(6) -dipeptide)](CF3SO3)(2) (3-6) after 24-36 h at 20degreesC. An analogous thermodynamic chemospecificity was also established for the complexes [(eta(5) -Cp*)Ir(eta(6)-dipeptide)](CF3SO3)(2) (7, H-Phe-Trp-OH; 8, H-Phe-Tyr-OH). However, a time-dependent 1H NMR study of the reaction between [(eta(5) -Cp*)Ir(acetone)(3)] (CF3SO3)(2) (2) and H-Tyr-Phe-OH confirms an initial kinetic preference for eta(6)-coordination of the C-terminal arene, as is also apparent from product mixtures obtained after treating 2 with H-Trp-Phe-OH or H-Trp-Tyr-OH for 1-2 d at 50 degreesC. Dinuclear sandwich complexes of the type [(eta(5)-Cp *)Ir(mu(2)-H-Met-X-OH-eta(6)-X:kappa(2)N(M), S)Pt(en)](CF3SO3)(4) (9-11, X = Phe, Tyr, Trp) can be prepared in CF3COOH following initial N-terminal kappa(2)N(M), S chelation of the (en)Pt-II fragment by the methionine residue of the dipeptide. Chemospecific kappaS coordination of the [(eta(5)-Cp *)Ir(dppZ)](2+) fragment in [(eta(5)-Cp*)Ir(dppz) (H-2-HArg-Met-NH2-kappaS)](4+) (12), [(eta(5)-Cp*)Ir(dppz)}(2)(mu-H-2-Met -Met-OH-kappaS:kappaS')](5+) (13) and [(eta(5)-Cp*)Ir(dppz)(mu-H-Gly-Met-OH-kappaS:kappaN(G))Pt(terpy)](4+) (14) affords effective metallointercalators for DNA with binding constants K-b in the range 1.3-3.3 x 10(6) M-1 and marked melting temperature shifts DeltaT(m) of respectively 10.2, 15.2 and 11.2 degreesC. (C) 2003 Elsevier B.V. All rights reserved.