The consequences of photoexcitation of a platinum diimine bisacetylide complex and its triads with phenothiazine species (McGarrah, J. E.; Eisenberg, R. Inorg. Chem. 2003,42,4355-4365) were investigated by the photoinduced transient displacement current (PTDC) method, with the aim of understanding the role of solvent in defining the nature and extent of intratriad electron transfer. PTDC enables reports on the distance of charge separation in photoexcited states. Photoexcition of the triad, Pt(dbbpy)(CCC 6H 4CH 2(PTZ)) 2 (where dbbpy = 4,4'-di-terr-butyl- 2,2'-bipyridine), leads to formation of the 3MLCT excited state, which in CH 2Cl 2 is intramolecularly quenched by PTZ to form a charge-separated (CS) state, Pt(dbbpy .-)(CCC 6H 4CH 2(PTZ) CCC 6H 4CH 2(PTZ .+); the CS state features a dipole moment oriented in essentially the opposite direction to that of the ground state. In toluene the last step of charge separation is shut down. In THF these two transient states are equilibrated, approximately as a 1:1 mixture of 3MLCT and CS states, causing a complex, but instructive, PTDC response. The PTDC response for Pt(dbbpy)(CCC 6H 5) 2, on the other hand, is similar in all solvents and shows a negative signal corresponding to a long-lived, and comparatively nonpolar, 3MLCT state. The ground-state dipóle moment, μ g, weakly increases with solvent polarity, from ∼11.5 D in toluene to ∼15.5 D in THF and CH 2Cl 2.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry