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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Infrared Intensification and Hydrogen Bond Stabilization: Beyond Point Charges
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Infrared Intensification and Hydrogen Bond Stabilization: Beyond Point Charges

机译：红外增强和氢键稳定：超出点电荷

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摘要

Infrared band intensification of the A-H bond stretching mode of A-H center dot center dot center dot B acid-base systems has long been known to be the most spectacular spectral change occurring on hydrogen bonding. A QTAIM/CCTDP model is reported here to quantitatively explain the electronic structure origins of intensification and investigate the correlation between experimental enthalpies of formation and infrared hydrogen bond stretching intensifications amply reported in the literature. Augmented correlation-consistent polarized triple-zeta quantum calculations at the MP2 level were performed on complexes with HF and HCl electron acceptors and HF, HCl, NH3, H2O, HCN, acetonitrile, formic acid, acetaldehyde, and formaldehyde electron donor molecules. The A-H stretching band intensities are calculated to be 3 to 40 times larger than their monomer values. Although the acidic hydrogen atomic charge is important for determining the intensities of HF complexes relative to HCl complexes with the same electron donor, they are not important for infrared intensifications occurring on hydrogen bond formation for a series of bases with a common acid. Charge transfers are found to be the most important factor resulting in the intensifications, but dipolar polarization effects are also significant for each series of complexes. A mechanism involving intra-acid and intermolecular electron transfers as well as atomic polarizations is proposed for understanding the intensifications. The calculated sums of the intermolecular electron transfer and acid dipolar polarization contributions to the dipole moment derivatives for each series of complexes are highly correlated with their enthalpies of formation and H-bond intensifications. This could be related to increasing electron transfer from base to acid that correlates with the calculated hydrogen bonding energies and may be a consequence of the A-H bond elongation on complex formation having amplitudes similar to those expected for the A-H vibration.
机译：A-H中心点中心点中心点B酸碱系统的A-H键拉伸模式的红外波浪强化已知是在氢键上发生的最壮观的光谱变化。 Qtaim / CCTDP模型在这里报告了定量解释了强化的电子结构起源，并研究了在文献中充分报道的形成和红外氢键舒展强度的实验焓与红外氢键之间的相关性。在用HF和HCl电子受体和HF，HCl，NH 3，H 2 O，HCN，乙腈，甲酸，乙醛和甲醛电子给体分子中对MP2水平进行MP2水平的增强相关 - 一致的偏振三Zeta量子计算。 A-H拉伸带强度计算为比其单体值大的3至40倍。尽管酸性氢原子电荷对于用相同的电子供体的HCl络合物确定HF复合物的强度是重要的，但对于用常用酸的一系列碱的氢键形成，它们对红外强化并不重要。发现电荷转移是最重要的因素，导致强化，但双极极化效应对于每种复合物也是显着的。提出了一种涉及酸内和分子间电子转移以及原子偏振的机制，以了解强化。对偶极电矩衍生物的分子间电子转移和酸偶极偏振贡献的计算总和与它们的形成和H键强度的焓高度相关。这可能与从碱中的电子转移增加到酸，其与计算出的氢键能量相关，并且可以是A-H键伸长在具有类似于A-H振动的那些类似的复杂形成上的粘合伸长率。

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