Monosolvation of R-1-phenyl-2,2,2-trifluoroethanol with amines: Configurational effects on the excitation, ionization, and fragmentation of diastereomeric complexes

Wavelength and mass selected resonant two-photon ionization spectra of molecular clusters between R-1-phenyl-2,2,2-trifluoroethanol (FER) and methylamine (M) or the enantiomers of 2-aminobutane (A(R) and A(S)) were recorded after supersonic molecular beam expansion and analyzed with the aid of ab initio molecular orbital calculations. The experimental results agree with theoretical calculations pointing to the predominance of the two most stable conformers of monosolvated FER whose CF3 group establishes intense NH center dot center dot center dot F interactions with the selected amines so as to orient them away from the aromatic ring. This reduces the enantio selectivity of FER toward the 2-aminobutane enantiomers as compared to that exhibited by the R-1-phenylethanol (E-R) analogue, where obviously NH center dot center dot center dot F interactions are absent.