LAUSR

Ultrafast vibrational dynamics of monolayers from a rhenium carbonyl complex at solid–liquid interfaces is investigated with the help of 2D ATR IR spectroscopy in dependence of the solvation environment. By changing the solvent from methanol to acetonitrile, we observe a structural transition between two states and find that this transition is fully reversible. The two coexisting states are identified by distinct but closely spaced (∼15 cm–1) vibrational bands in the region of the A′(1) symmetric carbonyl stretch vibration. Surface-dilution experiments suggest that the newly formed state in acetonitrile is related to aggregation of molecules at the surface. The vibrational energy transfer rate between the two species (∼30 ps) is used as a structural measure, based on which the morphology is characterized as partially ordered dimers in an otherwise disordered but closely packed monolayer.