Hydrogen bonded and non-hydrogen bonded van der Waals clusters: Comparison between clusters of pyrazine, pyrimidine, and benzene with various solvents

Solute–solvent clusters of pyrazine, pyrimidine, and benzene (solutes) and CnH2n+2 (n=1,2), NH3, and H2O (solvents) are studied by the techniques of supersonic molecular jet spectroscopy and two-color time-of-flight mass spectroscopy (two-color TOFMS). Spectral shifts, van der Waals (vdW) modes, dissociation energies, and vdW mode–solute mode vibronic couplings are characterized for most of the observed clusters. Based on these data and previous results for hydrocarbon systems, cluster geometries can be suggested. Lennard-Jones potential (6-12-1) calculations are also performed for these clusters and in all instances for which comparisons can be readily made, calculated and experimentally estimated geometries and binding energies agree completely. Clusters of N-heterocyclic solutes and H2O are not observed experimentally. Systematics and trends among the clusters reported herein and those previously reported are discussed and analyzed.