Ultrafast transient absorption spectra with probing in the deep-UV/near-UV range (212-400 nm) are measured for methanol and acetonitrile solutions containing copper(II) chloride complexes. Following 255 nm and 266 nm photolysis of methanol and acetonitrile solution, respectively, a monochlorocomplex is preferentially excited to the ligand-to-metal charge transfer (LMCT) excited state. Experimental results demonstrate that the Franck-Condon LMCT excited state undergoes internal conversion via back electron transfer (major pathway) giving rise to the vibrationally hot ground-state parent complex. Vibrational relaxation of hot parent complexes occurs within 5 ps. Copper-chloride homolitical bond dissociation (minor pathway) yields the copper(I) solvated and chlorine atom/solvent charge-transfer complexes. Insights into ligand substitution mechanisms of Cu(II) are acquired by monitoring the re-equilibration processes involving dichloro- and unsubstituted forms of Cu(II) complexes present in solution, which lead to recovery of the hole in the monochlorocomplex ground-state population caused by photoexcitation.

Ultrafast photochemistry of copper(II) chlorocomplexes in methanol and acetonitrile solutions

243rd National Meeting (2012)

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