Probing the Origins of Intrinsic Chiroptical Response and the Roles of Extrinsic Perturbations

在化学系化学结构，动力学和机制-A（CSDM-A）计划的支持下，耶鲁大学的帕特里克瓦卡罗教授正在探索分子手性的光谱特征，以了解其基本起源并促进其实际应用。当分子的化学结构与它们的镜像不完全相同时，分子是手性的，就像一个人的左手和右手不能重叠一样。当手性分子与光相互作用时，它们可以旋转其偏振，相反手性的分子在相反方向上旋转偏振。然而，使用这种偏振旋转来表征手性是具有挑战性的，因为样品通常是左手和右手分子的混合物，并且旋转的程度可能受到分子中原子的振动以及与周围溶剂分子的相互作用的影响。Vaccaro教授和他的团队将通过将实验测量与理论分析相结合来解决这一挑战，以研究原子运动和周围溶剂如何影响分子的手性性质。他们的发现可能与生物学中手性系统的研究以及不对称催化的先进方法有关。该项目还将为未来的科学家和教育工作者提供多学科的研究机会，并吸引来自地区K-12学校的学生和教师参与科学研究的各个方面。具有不同结构和电子基序的物种的电子圆双折射（ECB）将在溶剂化和隔离条件下进行探索，后者的工作依赖于超灵敏腔衰荡偏振测定法（CRDP）的变体。除了生成无溶剂的基准验证色散光学活性的理论预测，假定的作用所发挥的核自由度将被系统地解剖通过温度依赖性和光泵探测振动动力学，以及由同位素产生的手性（IEC）所产生的独特的光谱特征。除了解开非手性电子和手性核自由度之间的紧密耦合，必须负责IEC光学活性，振动范例将详细说明工程师同位素循环微分响应特性。分离和溶剂化的手性反应之间的关键联系将通过在可调的超临界流体中进行研究来建立，该超临界流体允许介质的物理化学性质在不改变分子间力的基本性质的情况下变化。在并行量子化学分析和分子动力学模拟的指导下，这些努力将描述孤立物种的光学活性，同时探索复杂的手性溶剂化现象。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) program in the Division of Chemistry, Professor Patrick Vaccaro of Yale University is exploring spectroscopic signatures of molecular chirality to understand their fundamental origins and facilitate their practical applications. Molecules are chiral when their chemical structure is not identical to their mirror image, much in the same way that one's left and right hands are not superimposable. When chiral molecules interact with light, they can rotate its polarization, with molecules of opposite handedness rotating the polarization in opposite directions. However, using this polarization rotation to characterize chirality is challenging, as samples are often a mixture of left- and right-handed molecules, and the degree of rotation can be affected by the vibration of atoms in the molecule and interaction with surrounding solvent molecules. Professor Vaccaro and his group will address this challenge by combining experimental measurements with theoretical analyses to study how the atomic motions and surrounding solvent affect chiroptical properties of molecules. Their discoveries could have relevance to the study of chiral systems in biology as well as advance approaches to asymmetric catalysis. The project will also provide multidisciplinary research opportunities for individuals destined to become our next generation of scientists and educators, as well as engage pupils and teachers from regional K-12 schools in various aspects of scientific research.The electronic circular birefringence (ECB) of species possessing diverse structural and electronic motifs will be probed under solvated and isolated conditions, with the latter work relying on variants of ultrasensitive cavity ring-down polarimetry (CRDP). Aside from generating solvent-free benchmarks for validating theoretical predictions of dispersive optical activity, the putative roles played by nuclear degrees of freedom will be dissected systematically through temperature-dependent and optical-pumping probes of vibrational dynamics, as well as by the unique spectral signatures arising from isotopically engendered chirality (IEC). In additional to unraveling the intimate coupling among achiral-electronic and chiral-nuclear degrees of freedom that must be responsible for IEC optical activity, vibronic paradigms will be elaborated to engineer isotopic circular-differential response properties. The crucial link between isolated and solvated chiroptical response will be forged by conducting studies in tunable supercritical fluids that allow the physicochemical properties of a medium to be varied without altering the basic nature of intermolecular forces. Guided by parallel quantum-chemical analyses and molecular-dynamics simulations, such efforts will describe optical activity in solitary species while simultaneously exploring complex chiral solvation phenomena.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.