Tunneling in novel hydroxycarbenes

基于Giessen（实验有机化学家和光谱学家）和Budapest（计算量子化学家）团队的互补背景和专业知识，我们提出了一个联合项目，该项目独特地结合了设计的新型碳烯的制备、检测、光谱以及计算表征，这些碳烯在低温（低至6 K）的大屏障下表现出增强的氢和可能的重原子隧道。低温基质的极低温度和惰性气体环境非常适合于单基态表面上的量子化学反应速率和隧穿（量子反应动力学）研究。所提出的全维和降维反应动力学计算有望指导新的实验，并且当与复杂的电子结构计算相结合时，应该揭示在几分钟到几天的时间尺度上，在0 K附近的大障碍下，控制增强量子力学隧道的因素。提出的研究旨在回答的问题包括：(a)电子取代基效应如何改变新型不饱和羟基碳烯中的h隧穿速率；(b)可为可观测的h隧穿提供多大的屏障；(c)氢键可以用来调节h隧穿速率吗？提出的研究计划的新方面包括：(a)系统地制备一系列电子相关的取代的，目前未知的羟基羰基；(b)取代羟基羰基的合成路线的发展；(c)利用最先进的量子化学（包括突破性的电子结构、核运动和反应动力学计算），研究电子对隧穿的影响；(d)含5个或更多原子和/或其PES上的多个极小值的碳烯的旋转振动谱的变分测定；(e)基于可用性的微规范速率常数的量子化学计算，该计算基于一种与时间无关的机制，类似于允许确定一套几乎完整的平稳旋转振动波函数和能级的机制。

Building on the complementary backgrounds and expertise of the Giessen (experimental organic chemists and spectroscopists) and the Budapest (computational quantum chemists) groups, we propose a joint program that uniquely combines the preparation, detection, and spectroscopic as well as computa-tional characterization of designed novel carbenes exhibiting enhanced hydrogen and possibly heavy-atom tunnelling under large barriers at low cryogenic temperatures (down to 6 K). The very low temperatures and the noble gas environment of cryogenic matrices are ideally suited for quantum chemical reaction rate and tunnelling (quantum reaction dynamics) studies on single ground-state surfaces. The proposed full- and reduced-dimensionality reaction dynamics computations are expected to guide new experiments and, when augmented with sophisticated electronic structure computations, should shed light on the factors that govern enhanced quantum mechanical tunnelling under large barriers near 0 K on timescales of minutes to days. Questions the proposed research aims to answer include: (a) how do electronic substituent effects alter the rates of H-tunnelling in novel unsaturated hydroxycarbenes; (b) how large a barrier can be afforded for observable H-tunnelling; and (c) can hydrogen bonding be used to tune the rate of H-tunneling? Novel aspects of the proposed research program include: (a) systematic preparation of a series of electronically related substituted, currently unknown hydroxycarbenes; (b) development of synthetic routes to substituted hydroxycarbenes; (c) studying the electronic effects on tunnelling, utilizing the most advanced levels of quantum chemistry (including ground-breaking electronic structure, nuclear motion, and reaction dynamics computations); (d) variational determination of rovibrational spectra of carbenes containing five or more atoms and/or multiple minima on their PES; (e) quantum chemical computation of microcanonical rate constants based on the availability based on a time-independent machinery similar to that which allows determination of a nearly complete set of stationary rotational-vibrational wave functions and energy levels.