Solvent effect on the type (red-shifted or blue-shifted) of hydrogen bond

Abstract

Solvent (liquid xenon) effect on the four hydrogen-bonded complexes F 3C–H⋯NH 3, F 3C–H⋯N(CH 3) 3, F 3C–H⋯NCH, and F 3C–H⋯O(CH 3) 2 as well as on the two intramolecular hydrogen-bonded configurations, TG(T∣G′) conformer of 1-methoxy-2-(dimethylamino)-ethane (in which the C–H⋯O hydrogen bond is involved) and Z-conformer of 2-( N-methoxyl iminomethyl)-4(1 H)-pyridinone (in which the N–H⋯O hydrogen bond is involved), is investigated with polarized continuum model at B3LYP/6-311 + G(d, p) level of theory. Solvent effect on the type (red-shifted or blue-shifted) of hydrogen bond can be generally divided into six classes ( A– F). The solvent effect does not change the type of hydrogen bond when the frequency shift of the ν(X–H) (X = C or N) of the hydrogen bond donor caused by hydrogen bond formation in gas phase is considerably larger than both that of the hydrogen bond donor and that of the hydrogen-bonded complex caused by solvent effect. Classes B– E belong to this situation. The type of hydrogen bond will probably change when the former is considerably smaller than either value of the latter. Classes A and F belong to this situation. Our calculations show that solvent effect on the first to fifth hydrogen-bonded system belongs to class C, C, D, D, and E, respectively. For the sixth system, solvent effect changes the N–H⋯O hydrogen bond from the red-shifted type of the gas phase (Δ ν(N–H) = −17.1 cm −1) to the blue-shifted type of the solution phase (Δ ν(N–H) = 21.8 cm −1). This is the second theoretical instance of class A.