Quantification of Conventional and Nonconventional Charge-Assisted Hydrogen Bonds in the Condensed and Gas Phases

Charge-assisted hydrogen bonds (CAHBs) play critical roles in many systems from biology through to materials. In none of these areas has the role and function of CAHBs been explored satisfactorily because of the lack of data on the energy of CAHBs in the condensed phases. We have, for the first time, quantified three types of CAHBs in both the condensed and gas phases for 1-(2'-hydroxylethyl)-3-methylimidazolium acetate ([C(2)OHmim][OAc]). The energy of conventional OH center dot center dot center dotOAc CAHBs is similar to 10 kcal. mol(-1), whereas nonconventional C(sp2)H center dotOAc and C(sp3)H center dot center dot center dotOAc CAHBs are weaker by similar to 5-7 kcal.mol(-1). In the gas phase, the strength of the nonconventional CAHBs is doubled, whereas the conventional CAHBs are strengthened by