NMR study of substituent effects in platinum(II) intercalating agents

✍ Scribed by Robert T. C. Brownlee; W. David McFadyen; Maxwell J. O'Connor; Trevor J. Rook; Ian A. G. Roos; Laurence P. G. Wakelin

• Publisher: John Wiley and Sons
• Year: 1987
• Tongue: English
• Weight: 517 KB
• Volume: 25
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260250607

✦ Synopsis

A series of (4-X-thiophenolato) (2,2':6',2'-terpyridine)platinum(II) complexes [X = H, F, C1, Br, CH,, OCH3, NH,, N(CH3)2, NO,, COOCH3, CN, NH:& which have potential as DNA intercalators, have been synthesized. 13C and '95Pt NMR spectra of these complexes have been obtained in both D,O and DMSO-d6. The '95Pt shifts are highly sensitive to both solvent and distant substituent effects and span a chemical shift range of 72 ppm. The propagation and transmission of substituent effects within the complexes have been studied, and the '95Pt and thiophenolato C-1 13C chemical shifts correlated with Hammett substituent constants, using the dual substituent approach. The results show that the (terpy)Pt-S-group is an effective .rr-donor to the aromatic ring. Further, a normal substituent chemical shift effect is seen with the thiophenol C-1, wherebl electron-withdrawing groups cause a decrease in electron density, whereas the platinum centre shows the reverse effect, i.e. electron-withdrawing groups cause an increase in electron density. The latter effect has been explained in terms of a m-polarization eEect, with electron density from the terpyridine ligand being supplied to the platinum centre in response to demand by the thiophenol substituent.

KEY WORDS 13C NMR '95Pt NMR (4-X-thiophenolat0)(2,2",2~-terpyridine)platinum( 11) complexes Substituent effects