Photophysical and photochemical properties of W(0) and Re(I) carbonyl complexes incorporating ferrocenyl-substituted pyridine ligands

Complexes of polypyridyl d(6)-metal (W-0 and Re-I) carbonyl complexes have received a great deal of attention because of their relatively straightforward synthetic procedures and their intriguing photophysical, photochemical, and electrochemical properties.' Ferrocene and its derivatives have been studied for their mixed-valence,(2) charge-transfer,(3) and electrochemical properties;(3a,4) their special redox-active features have also been used to develop electrochemical sensors.(5) However, while most of these studies are focused on homonuclear ferrocenes bridged by different organic spacers,(6) the incorporation of a ferrocene moiety within metal carbonyl complexes has been investigated much less.' A few studies have appeared which have primarily focused on the synthesis, electrochemistry, and potential application as nonlinear optical materials of such species,(7) but investigations of their photophysical and photochemical properties are lacking.(8) In this paper, we report the photophysical and photochemical proper-ties of several polypyridyl d(6)-metal (W-0 and Re-I) carbonyl complexes incorporating ferrocene end-capped pyridine ligands. The structures of these complexes and ligands are illustrated in Chart 1. Instruments 450-W mercury arc lamp using interference filters (Ealing Corp., 10-nm band-pass) to isolate the excitation wavelength. Typical light intensity was 5 x 10(-8) to 1 x 10(-7) einstein/ min. A Lexel Corp. model 95-4 argon ion laser (4 W all lines) was used to perform the photolysis at 458, 488, and 514 nm with typical laser powers of between 20 and 30 mW. The photochemical quantum efficiencies were calculated on the basis of the first 40% conversion of the reaction, and the errors were found to be within 10% (with quantum efficiencies above 10(-6)). Detailed procedures for the photolysis experiments and the calculation of the photochemical quantum yield have been described in previous papers.(10)