The Jahn-Teller Effect - Fundamentals and Implications for Physics and Chemistry
The Jahn-Teller Effect - Fundamentals and Implications for Physics and Chemistry
复制标题
扬-特勒效应 - 物理和化学的基础知识和启示
DOI：
10.1007/978-3-642-03432-9_11
复制
发表时间：
2009
期刊：
影响因子：
--
通讯作者：
McKinlay R
中科院分区：
文献类型：
--
作者：
McKinlay R
过渡金属羰基配合物表现出广泛的电子振动耦合诱导的现象，其中一些只是最近才开始理解通过国家的最先进的光谱，以及理论和计算研究。历史上，Jahn-Teller效应被用来解释结构信息，如基态几何和最低能量自旋态。我们将回顾重要的早期工作，了解二元过渡金属羰基配合物的结构方面，然后继续讨论最新的时间分辨的工作，以及旨在解释这些结果的计算研究。最近的时间分辨实验已经表明，各种意想不到的功能产生的光解金属羰基的第一，第二和第三行的周期表，也倍增金属-金属键合羰基。这些实验表明，不饱和金属羰基在单重态自旋状态下产生;无辐射弛豫如此之快，以至于排除了自旋轨道引起的高自旋流形的变化。这种不饱和金属羰基化合物可能具有可接近的Jahn-Teller简并几何形状，这些圆锥形交叉点被认为是超快无辐射衰变的关键。这是一个令人兴奋的发展，因为这些系统自然地将Jahn-Teller效应与光化学结合在一起。这种低自旋简并在经典无机化学中通常不会发现;在这里，它们是通过光化学方法实现的，从激发到光产物的确切机制仍然没有完全理解。在现代计算工作中，我们讨论了当前最先进的计算方法，需要正确地描述在基态和激发态的金属-羰基键合，由此产生的势能面，超快光解离和随后的无辐射衰变（包括锥形交叉）的机制。我们详细讨论了与Cr（CO）6和Fe（CO）5的光化学有关的Jahn-Teller效应。在这些例子中，有用的群论工具，如外核原理将被举例说明。几个新的结果将包括在各个适当的点在整个教程审查。
Transition metal carbonyl complexes exhibit a wide-range of vibronic coupling induced phenomena, some of which has only recently begun to be understood via state-of-the-art spectroscopic, as well as theoretical and computational investigations. Historically the Jahn–Teller effect has been used to explain structural information such as ground-state geometries and the lowest energy spin-state. We will review important early work on understanding structural aspects of binary transition metal carbonyl complexes, and then move on to discuss the most recent time-resolved work, and computational studies aimed at explaining these results. The recent time-resolved experiments of have shown that a variety of unexpected features arise from photodissociation of metal carbonyls of the first, second and third rows of the periodic table, and also multiply metal–metal bonded carbonyls. These experiments show that an unsaturated metal carbonyl is produced in the singlet spin-state; the radiationless relaxation being so fast as to preclude a spin–orbit induced change to the high-spin manifold. Such unsaturated metal carbonyls may have accessible geometries that are Jahn–Teller degenerate, and these conical intersections are believed to be the key to ultrafast radiationless decay. This is an exciting development as these systems naturally bring together aspects of the Jahn–Teller effect with photochemistry. Such low-spin degeneracies are not normally found in classical inorganic chemistry; here they are reached photochemically, the exact mechanism from excitation to photoproduct still not fully understood. In relation to modern computational work we discuss current state-of-the-art computational methodologies required to correctly describe metal–carbonyl bonding in the ground and excited states, the resulting potential energy surfaces, and mechanisms of ultrafast photodissociation and subsequent radiationless decay (including conical intersections). We discuss in detail the Jahn–Teller effect in relation to the photochemistry of Cr(CO)6, and Fe(CO)5. Throughout these examples useful group theoretical tools such as the epikernel principle will be exemplified. Several new results will be included at various appropriate points throughout this tutorial review.