High-resolution electronic spectroscopy of some substituted N-phenylpyrrolidines and their solvated clusters in a supersonic jet: site selectivity and cluster structures

Abstract

High-resolution laser-induced fluorescence excitation spectra of a series of cycloalkylbenzoic acid esters and benzonitriles, and of their complexes with argon and a range of other ‘solvent’ molecules have been recorded under jet-cooled conditions. Power-saturation studies have established the presence of separately stabilised conformers in the isolated esters, while progressions of satellite features in the molecular complexes have been assigned to aggregates comprising both singly and multiply (n⩽ 4) solvated clusters. Rotational band-contour simulations, guided initially by the predictions of MNDO and molecular-mechanics calculations (for the bare molecules) supplemented by summed atom–atom pair potential calculations (for the complexes) have allowed assignment and structural analyses to be completed. Optimised results are presented for some selected systems. For non-polar solvents, where the intermolecular forces are weak, local site selectivity appears to be the rule.