Concordia University Wisconsin, 12800 N. Lakeshore Drive, Mequon, Wisconsin 53097, USA.
Phys Chem Chem Phys. 2013 Oct 21;15(39):16736-45. doi: 10.1039/c3cp52418c. Epub 2013 Aug 29.
Infrared Predissociation (IRPD) spectra of Cl(-)(NMA)1(H2O)0-2Ar2 combined with Born-Oppenheimer Molecular Dynamics (BOMD) IR spectra have been acquired, providing the structure and dynamics of these systems. We show that the chloride ion is bound to the hydrogen of the amide N-H group, forming a strong ionic hydrogen bond, weakening the N-H stretch, and shifting it to lower frequency. The presence of water molecules enhances the ionic hydrogen bond by binding to the amide carbonyl oxygen of NMA and shifts the N-H stretch further to lower frequency. The BOMD IR spectra can recapture all, but about 100 cm(-1), of the 600 to 700 cm(-1) shifts due to the strong N-H stretch anharmonicities observed in experiments. This residual error was found to be due to the lack of zero point energy in the classical treatment of motion in the BOMD method.
已获得 Cl(-)(NMA)1(H2O)0-2Ar2 的红外预解离 (IRPD) 光谱与玻恩-奥本海默分子动力学 (BOMD) IR 光谱相结合，提供了这些系统的结构和动力学信息。我们表明，氯离子与酰胺 N-H 基团的氢结合，形成强离子氢键，削弱 N-H 伸缩，使其向低频移动。水分子的存在通过与 NMA 的酰胺羰基氧结合增强了离子氢键，进一步将 N-H 伸缩向更低的频率移动。BOMD IR 光谱可以捕捉到实验中观察到的强 N-H 伸缩非谐性导致的 600 到 700 cm(-1) 移动的全部，但约 100 cm(-1) 除外。这一残留误差是由于 BOMD 方法中运动的经典处理中缺乏零点能造成的。
