Laser-induced fluorescence spectroscopy of ethyl and methyl p-aminobenzoates weakly bound complexes with polar solvents (CH2F2, CH3F and CHF3) Original Research Article

Weakly bound complexes derived from the combination of ethyl and methyl p-aminobenzoates (ABEE, ABME) with various polar halomethanes (CH2F2, CHF3, CH3F) have been studied by low- and high-resolution nanosecond laser-induced fluorescence spectroscopy. The complexes were prepared in a jet pulsed supersonic expansion. Both blue- and red-shifted bands have been observed for ABME/ABEE-(CH2F2, CHF3) complexes and interpreted as resulting from dipole-dipole and H-bonding interactions. Partially resolved rovibronic bands provided by high-resolution pulsed laser-induced fluorescence, in addition to spectral shifts, have been used to determine relative positions of host and solvent components and also as the final criteria to establish the proposed geometry of the complexes. ABME/ABEE-(CH3F) complexes depict a different spectral pattern, showing a comparatively large red-shift structured band. This effect has been assigned to the selective deep of one of the potential energy wells produced by dipole-dipole stabilisation, effect also found in other H-bond weakly bound complexes. A discussion of the geometries of the complexes in relation to the anisotropy of the H-bonding and dipole-dipole intermolecular forces is presented.