Convenient syntheses and characterization of fluorophilic perfluorooctyl-propyl amines and ab initio calculations of proton affinities of related model compounds

A convenient and effective method for the preparation of perfluorooctyl-propyl amines ([Rf8(CH2)3]nNH3−n (1–3), n=1,2,3; Rf8(CH2)3NHMe (4); [Rf8(CH2)3]2NMe (5); Rf8(CH2)3NMe2 (6); Rf8=F(CF2)8) via a step by step alkylation with Rf8(CH2)3I is described. The fluorophilicity values of 1–6 were determined by GC and range from 0.79±0.07 (1) to 5.3±0.2 (3). Systematic ab initio calculations of proton affinities of model compounds (7a–j) using Hartree–Fock and density functional theory imply that the inserted trimethylene spacer unit efficiently reduces the electron-withdrawing effect of the perfluorinated segment. All structures were verified by multinuclear one- and two-dimensional NMR experiments involving both homo- (19F–19F) and hetero-nuclear (1H–13C, 1H–15N, 19F–13C) correlations based on the GMQFCOPS and inverse 1H and/or 19F detected GHSQC, GHMQC sequences with broadband adiabatic 13C-decoupling.