School of Chemistry, Monash University, Clayton, Victoria, Australia.
J Phys Chem B. 2011 Dec 15;115(49):14659-67. doi: 10.1021/jp208150b. Epub 2011 Nov 9.
The nature of hydrogen bonding was compared in neutral complexes and negatively charged complexes consisting of either the HF molecule or the halide anion (fluoride and chloride) and the C-H bond in the methane molecule with a varying degree of fluorination (such as CH(4), CH(2)F(2), and CHF(3)). Both linear (C(3v) symmetry) and nonlinear (C(2v) symmetry) hydrogen-bonded complexes were studied. Symmetry-adapted perturbation theory was used to decompose interaction energies into fundamental components such as Coulomb, repulsion, induction and dispersion to analyze the interplay among these forces in stabilizing hydrogen bonding. In the linear charged complexes, both Coulomb attraction and induction significantly contributed to the stabilization of hydrogen bonding. In the nonlinear charged complexes, mainly Coulomb attraction contributed to the HB complex stabilization, with the inductive forces playing a less important role. Contrary to the neutral complexes, dispersion forces played only a marginal role in the charged complexes. Interplay between the fundamental forces was also investigated in the ion pairs of the imidazolium-based ionic liquid, [C(2)mim]Cl, that were categorized as either (1) typical ion-ion interaction, with the anion interacting from above or below the imidazolium plane; or (2) hydrogen-bonding interaction, with the anion interacting with the C2-H bond of the imidazolium cation. Both types of interactions were found to induce similar charge transfers, and the analysis of the energetic components revealed only a slight difference in the ion pairs studied: (1) both interactions were electrostatically driven, between 86% and 88% of the overall attractive energy, with the electrostatic component being slightly lower in the hydrogen-bonded ion pairs by ~8 kJ mol(-1); and (2) dispersion forces were found to be stronger in the typical ion-ion interactions by ~15 kJ mol(-1) and could be possible only due to the fact that the anion was able to move closer to the cation with no steric hindrance. From the experimental point of view, a vibrational red shift is expected in the hydrogen-bonded complexes of imidazolium-based ionic liquids, whereas the ion-ion interactions are more likely to produce a slight blue shift.
氢键的性质在由 HF 分子或卤化物阴离子（氟化物和氯化物）与甲烷分子中的 C-H 键组成的中性配合物和带负电荷的配合物中进行了比较，这些配合物的氟化程度不同（如 CH(4)、CH(2)F(2)和 CHF(3)）。研究了线性（C(3v)对称）和非线性（C(2v)对称）氢键配合物。使用对称性自适应微扰理论将相互作用能分解为基本成分，如库仑、排斥、诱导和色散，以分析这些力在稳定氢键中的相互作用。在线性带电配合物中，库仑吸引和诱导都对氢键的稳定有显著贡献。在非线性带电配合物中，主要是库仑吸引对 HB 配合物的稳定起作用，诱导力的作用较小。与中性配合物相反，色散力在带电配合物中只起次要作用。还研究了基于咪唑鎓的离子液体[C(2)mim]Cl 的离子对中的基本力相互作用，这些离子对分为（1）典型的离子-离子相互作用，阴离子从咪唑鎓平面上方或下方相互作用；或（2）氢键相互作用，阴离子与咪唑鎓阳离子的 C2-H 键相互作用。这两种类型的相互作用都被发现会引起相似的电荷转移，对能量成分的分析表明，在所研究的离子对中只有细微的差异：（1）两种相互作用都是静电驱动的，总吸引能的 86%至 88%，氢键离子对中的静电分量略低约 8 kJ mol(-1)；（2）发现色散力在典型的离子-离子相互作用中更强，约强 15 kJ mol(-1)，这可能是由于阴离子能够在没有空间位阻的情况下更接近阳离子。从实验的角度来看，基于咪唑鎓的离子液体的氢键配合物预计会发生振动红移，而离子-离子相互作用更可能产生轻微的蓝移。
