Structural characterization of the acridine–(H2O)n (n=1–3) clusters by fluorescence-detected infrared spectroscopy

The vibrational spectra of supersonically cooled acridine–(H2O)n (n=1–3) clusters in the electronic ground state have been measured by fluorescence-detected infrared spectroscopy. The observed O–H stretching fundamentals of the solvent have been analyzed with the aid of density functional theory calculations, to assign the structures of the clusters. In the n=1 cluster, the water molecule acts as a proton donor which is hydrogen-bonded to the N atom of acridine. The second (third) water in the higher clusters is further hydrogen-bonded to the first (second) one to form a linear `water chainʹ, which surrounds an edge of the acridine molecule approximately in the plane of the aromatic ring.