We have used transient two-dimensional infrared spectroscopy to study both the ground and excited electronic states of the photocatalyst, ReCl(CO)3(bpy), in tetrahydrofuran. In the ground state, the symmetric carbonyl stretch exhibits neither inhomogeneous broadening nor spectral diffusion, an observation we have made in many metal carbonyl complexes with more than two CO ligands. We attribute this inhomogeneity �immunity� to correlations between CO site energies and carbonyl couplings through back bonding. Strikingly, in the 3MLCT state, we observe both inhomogeneous broadening and 4 ps spectral diffusion consistent with the polarity and low viscosity of THF. The loss of inhomogeneity immunity likely arises from the rotation of the electronic wavefunction previously described by Vlcek et al. These results illustrate how transient 2D-IR spectroscopy provides insight into the changes in electron density resulting from optical excitation, charge transfer and energy transfer dynamics on electronic excited states.

Excited electronic state dynamics probed with ultrafast transient 2D-IR spectroscopy

245th National Meeting (2013)

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