Intraclustcr proton-transfc~was~bserved for mixed clusters of toluene and p-xylene with polar solvent molecules (NH 3 , CH 30H, 0 20) after~esonant two-photon IOmza~lOn.of the aromatic moiety. The transfer is deduced from the appearance of protonated solvent clusters, showing the R2PI spectra of their mixed cluster precursors. This process, observable only in combination with subsequent dissociation is cluster size dependent. The minimum number of solvent molecules necessary for a transfer to take place depends on the solvent's proton solvation energy.
Substitution reactions in mixed van der Waals aggregates, consisting of halobenzenes and polar molecules are studied by resonant two‐photon ionization (R2PI). From the optical fingerprints in the ion‐yield curves of the product ions we are able to assign their neutral precursors. The ipso substitution reactions have been found to depend both on the number and type of solvent molecules and on the halogen present and are discussed by an addition‐elimination mechanism. Dissociative electron transfer is found to play an important role in the reaction mechanism and in the size dependence of the reactivity.
After resonant two‐photon ionization of mixed clusters of substituted aromatics with polar and unpolar solvents we observed very selective intracluster relaxation reactions. They are assumed to take place in the cationic complexes. The selectivity of a nucleophilic substitution reaction of halogenated benzenenes with nucleophiles is rationalized by different isomeric structures of the neutral aggregates. Proton transfer from ionized methylated benzenes to polar solvents is found to be governed by the solvent's proton solvation energetics. Electron transfer, at present studied only for ether compounds as solvent, takes place, if the ionization potential of the solute is larger than of the solvent.
ChemInform Abstract (studied in a continuous, seeded supersonic beam, containing He as carrier gas and mixed clusters of toluene and p-xylene with polar solvent molecules NH3, MeOH, D2O).
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