Advanced Quantum Mechanical Methods for the Chiroptical Properties of Molecules in Solution

弗吉尼亚理工大学的T. Daniel Crawford获得了化学理论奖；化学系模型与计算方法项目旨在发展理论和计算方法，以准确预测溶液中手性分子的光学性质，这对计算化学来说仍然是一项具有挑战性的任务。手性分子是指两种不同的分子，它们的组成相同，但不能重叠，就像人的手一样。“左旋”分子和“右旋”分子是彼此的镜像。这些分子具有光学活性，它们可以顺时针或逆时针旋转平面偏振光。手性分子在化学的许多分支中扮演着重要的角色，包括控制生物功能的化学。Crawford和他的研究小组专注于开发强大而有效的方法来计算这些分子的特殊“手性”属性，其总体目标是为分配手性化合物的绝对立体化学构型提供实用而可靠的工具。这些研究在阐明分子结构与光致反应之间的密切关系方面具有重要意义，从而可能为化学界提供对光学活性本质的更深入了解。对于溶剂对分子性质的复杂影响，建模的最佳方法仍然难以捉摸，特别是对于旋光性（OR）、圆二色性（CD）、振动拉曼光学活性（ROA）和圆偏振发光（CPL）等对环境影响表现出高度敏感性的分子性质。该项目侧重于开发强大而高效的工具，用于液相中热学性质的高精度建模，包括隐式，显式和混合方法。隐式模型将被开发来近似体积溶质-溶剂相互作用，使用基于形状和密度的空腔与自一致推导的势耦合。将使用一种新的混合QM/MM方案来解释显式溶剂化效应，包括一种新的波函数嵌入周期方法。这些模型的有效实现将在很大程度上依赖于新兴的降标度方法，特别是在非共振光学活性的耦合簇线性响应方法中。

T. Daniel Crawford of Virginia Tech University is supported by an award from the Chemical Theory; Models and Computational Methods program in the Chemistry Division to develop theoretical and computational methods for the accurate prediction of the optical properties of chiral molecules in solution remains a challenging task for computational chemistry. A chiral molecule is one in which there are two different versions that are identical in composition but which cannot be superimposed, much like human hands. The "left-handed" and "right-handed" molecules are mirror images of one another. Such molecules are optically active, they can rotate plane-polarized light either clockwise or counter-clockwise. Chiral molecules play an important role in many branches of chemistry, including the chemistry that governs the functioning of living beings. Crawford and his research group focus on the development of robust and efficient methods for computing the special "chiroptical" properties of these molecules, with the overarching goal of providing practical and reliable tools for assigning absolute stereochemical configurations of chiral compounds. These studies are invaluable in the elucidating the intimate relationship between molecular structure and chiroptical response and thus may provide the chemical community with a deeper understanding of the nature of optical activity. The best approach for modeling the intimidating complexity of solvent effects on molecular properties remains elusive, especially for chiroptical properties such as optical rotation (OR), circular dichroism (CD), vibrational Raman optical activity (ROA), and circularly polarized luminescence (CPL), which exhibit an exquisite sensitivity to environmental effects. This project focuses on the development of robust and efficient tools for the high accuracy modeling of chiroptical properties in the liquid phase, including implicit, explicit, and hybrid approaches. Implicit models will be developed to approximate the bulk solute-solvent interaction using both shape- and density- based cavities coupled with potentials derived self-consistently. Explicit solvation effects will be accounted for using a new hybrid QM/MM scheme, including a novel wave-function-embedded periodic approach. Efficient implementation of these models will rely heavily on emerging reduced-scaling methods, particularly within the coupled cluster linear-response approach for non-resonant optical activity.