在本文中,通过在 M06-2X-D3/6-31+G(d) 理论水平上采用密度泛函理论 (DFT),对纤维二糖的分子相互作用进行了详细的从头算研究。众所周知,氢键在纤维二糖的溶解中起着至关重要的主导作用。为了在分子水平上理解氢键的性质,我们考虑了以下溶剂:水、甲醇、醋酸盐 ([ \(\textrm{CH}_{3}\textrm{COO}\) ] \(^- \) ), 丙酸 ([ \(\mathrm {CH_{3}CH_{2}COO}\) ] \(^-\) ), 巯基乙酸盐 ([ \(\mathrm {HSCH_{2}COO}\) ] \(^-\)和丙氨酸 ([Ala] \(^-\)). 对纤维二糖-溶剂复合物进行了相互作用能、分子中原子的量子理论 (QTAIM) 分析、自然键轨道 (NBO) 和对称适应的 petrubation 理论 (SAPT0),以深入了解纤维二糖中氢键的性质. 结果表明,[ \(\mathrm {CH_{3}COO}\) ] \(^-\)离子破坏了纤维二糖中现有的分子内相互作用,并与其形成新的分子间相互作用。[纤维二糖-溶剂]复合物的计算相互作用能按以下顺序排列:[ \(\mathrm {CH_{3}COO}\) ] \(^-\) > [ \(\mathrm {CH_{3}CH_ {2}COO}\) ] \(^-\) > [ \(\mathrm {HSCH_{2}COO}\) ] \(^-\)> [Ala] \(^-\) > 甲醇 > 水,这与实验溶解度观察结果一致。QTAIM 拓扑参数表明 [Cellobiose - acetate] \(^-\)复合物的极性共价特征,计算的氢键能进一步证实了这一点。此外,SAPT0 计算的能量分量显示,虽然相互作用能主要由静电相互作用支配,但感应力也起着重要作用,再次证实了相关氢键的共价特性。总的来说,这些结果对在分子水平上理解氢键和纤维二糖的溶解具有深远的意义。
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Ab-initio study on the covalent nature of hydrogen bonding in cellobiose
In this paper, a detailed ab-initio study on molecular interactions of cellobiose is presented by employing density functional theory (DFT) at the M06-2X-D3/6-31+G(d) level of theory. It is well known that hydrogen bonding plays a vital and dominating role in the dissolution of cellobiose. To understand the nature of H-bonding at the molecular level, we have considered the following solvents: water, methanol, acetate ([\(\textrm{CH}_{3}\textrm{COO}\)]\(^-\)), propanoate ([\(\mathrm {CH_{3}CH_{2}COO}\)]\(^-\)), thioglycolate ([\(\mathrm {HSCH_{2}COO}\)]\(^-\) and alaninate ([Ala]\(^-\)). The interaction energy, quantum theory of atom in molecules (QTAIM) analysis, natural bond orbital (NBO) and symmetry-adapted petrubation theory (SAPT0) were performed on the cellobiose-solvent complexes to get insights into the nature of H-bonding in cellobiose. It is shown that the [\(\mathrm {CH_{3}COO}\)]\(^-\) ion breaks the existing intra-molecular interactions in cellobiose and forms new inter-molecular interactions with it. The computed interaction energy for [cellobiose-solvent] complexes is in the following order: [\(\mathrm {CH_{3}COO}\)]\(^-\) > [\(\mathrm {CH_{3}CH_{2}COO}\)]\(^-\) > [\(\mathrm {HSCH_{2}COO}\)]\(^-\) > [Ala]\(^-\) > methanol > water, which is in agreement with the experimental solubility observations. The QTAIM topological parameters indicate the polar covalent character of the [Cellobiose - acetate]\(^-\) complex, which is further confirmed by the calculated hydrogen bond energy. Furthermore, the energy components from SAPT0 calculations display that while the interaction energy is primarily dominated by the electrostatic interactions, induction force also plays a significant role, reconfirming the covalent character of the associated H-bonds. Overall, these results have profound implications on the understanding of H-bonding and dissolution of cellobiose at the molecular level.