Fluorobenzene and p-difluorobenzene microsolvated by methanol: An infrared spectroscopic and ab initio theoretical investigation

Abstract

Structure and vibrations of phenol(H 2 O) 7,8 studied by infrared-ultraviolet and ultraviolet-ultraviolet doubleresonance spectroscopy and ab initio theory J. Chem. Phys. 110, 9898 (1999); 10.1063/1.478863Infrared-depletion spectroscopy study on hydrogen-bonded fluorobenzene-methanol clusters Laser spectroscopy, i.e., resonant two-photon ionization ͑R2PI͒, IR/R2PI ion depletion and hole burning spectroscopy have been applied in an experimental study of heterogenous clusters consisting of fluorobenzene ͑FB͒ or p-difluorobenzene ͑pDFB͒, respectively, microsolvated by up to three methanol molecules. Their infrared ion depletion spectra were taken in the region of the OH and CH stretches of methanol. In these complexes the methanol molecules form subclusters, which are weakly hydrogen bonded to either the aromatic -system ( OH ) or to the fluorine substituent ( F ) and a CH group ( CH ). In FB•͑MeOH͒ 1 , pDFB•͑MeOH͒ 1 , pDFB•͑MeOH͒ 2 and one isomer of FB•͑MeOH͒ 2 the methanol subunits exclusively exhibit F and CH H-bonds. A further isomer of FB•͑MeOH͒ 2 exhibits a OH type interaction. For FB•͑MeOH͒ 3 and pDFB•͑MeOH͒ 3 ͑1:3͒ complexes the methanol subcluster may take on either a chainlike or a ringlike conformation. In the chainlike isomer of FB•͑MeOH͒ 3 the methanol trimer interacts with the chromophore via a OH H-bond while with the corresponding pDFB cluster a F H-bond is formed. High level ab initio calculations, still feasible for molecular clusters of this size, have also been carried out to supplement the experimental investigations. These calculations include complete geometry optimizations of FB•͑MeOH͒ n ͑nϭ1-2͒ and pDFB•͑MeOH͒ 1 at the MP2/6-31ϩG* and B3LYP/ 6-31ϩG* levels of theory. The minimum energy structures of the microsolvates together with their harmonic vibrational spectra allow a reliable assignment of the experimentally observed spectra and the determination of structure of the complexes.

Infrared spectroscopy of mass-selected neutral molecular systems without chromophore: the formamide monomer and dimer

“…Rydberg electrons are thus transferred to species possessing an excess internal energy and that strongly influences the electron capture process. The IR excitation is thus monitored through the depletion of the anion signal, as in IR-UV-MS experiments in which a depletion of the cation signal is similarly induced by the IR resonant 'burning' of the vibrational ground state [6].…”

Phenylacetylene: A Hydrogen Bonding Chameleon

“…The intermolecular structures of hydrogen-bonded complexes of water and methanol with benzene, [66] and several substituted benzenes, such as fluorobenzene, [67] phenol, [68] 2-pyridone [69] and others, are known to be identical, and phenylacetylene is the only known exception. The most important question that arises at this stage is "what is the underlying factor that makes phenylacetylene interact with water and methanol differently?"…”

Diode laser spectroscopy of the ν7a band of fluorobenzene

“…For example, the role of fluorobenzene in p-hydrogen bonding complexes [1][2][3][4], or in cation-aromatic interactions [5] has been investigated. The importance of these systems arises largely from their role in issues such as molecular recognition, protein structural organization and protein-ligand interactions [1,5].…”