Intramolecular charge transfer in jet-cooled methyl 4-N,N-dimethylaminobenzoate·(water)n clusters studied by infrared depletion spectroscopy observed in the dispersed fluorescence

Jet-cooled clusters of methyl 4-N,N-dimethylaminobenzoate (DMABME) with one to three water molecules were investigated using a combination of laser-induced fluorescence (LIF), resonant two-photon ionization (R2PI), and IR depletion spectroscopy. The aim was to identify the minimum amount of water molecules at which DMABME undergoes intramolecular charge transfer (ICT) in the excited state. The comparison of IR depletion spectra observed both in the signals of the ionized clusters and in the ICT emission band reveals that ICT sets in with more than one water molecule. Ground state geometries of the complexes are suggested on the base of the obtained IR spectra and simple semi-empirical calculations.