The Fluorescence of N-Phenylpyrrole in an Argon/Acetonitrile Matrix

N-Phenylpyrrole (PP) was studied in an argon matrix at 14−30 K. The absorption and fluorescence excitation spectra are structureless, while the emission spectrum shows distinct vibrational structure. When a small amount of the polar molecule acetonitrile is added to the PP/argon matrix, UV excitation leads to two separate emission bands the relative intensity of which is strongly excitation wavelength dependent. Control experiments using a nonpolar molecule (ethylene) and dimethylaminobenzonitrile help to assign the spectra. Both emission bands are assigned to transitions from an electronically excited charge-transfer state that has two distinct minima.