We present ultrafast pump/deep-UV probe data revealing the radiationless relaxation pathways of a model monochloro complex of copper(II) in methanol solutions ([CuII(MeOH)5Cl]+) promoted into its ligand-to-metal charge-transfer excited state upon 255-nm excitation. A small fraction of the electronically excited species undergoes homolysis of the Cu-Cl bond. Re-equilibration processes involving dichloro- and unsubstituted forms of Cu(II) complexes present in solution provide insights into ground-state ligand substitution mechanisms of Cu(II). However, the majority of the initially excited species returns to the electronic ground state via back electron transfer on a sub-200-fs time scale. This is followed by vibrational relaxation of hot parent complexes within 5 ps. In addition, photochemical reaction paths and ligand substitution reactions following excitation of solvated MBr62- (M = Pt, Ir, and Os) complexes will be discussed. In particular, photoexcited aqueous PtBr62- undergoes ligand loss and subsequent nearly barrierless aquation with a time constant of 15 ps to form 1PtBr5(H2O)- in a 40% quantum yield.

Excited states relaxation and dynamics of ligand substitution in monochloro complexes of copper(II) and halogenated complexes of third-row transition metals

243rd National Meeting (2012)

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