Abstract

Electronic structures of four pyrene-derived N-heterocyclic carbene complexes of platinum(II) and gold(III) bearing cyclometallated 2,6-diphenylpyridine have been investigated theoretically. The structures of all complexes in gas phase have been first optimized. Different functionals and basis sets have been tested to find the best theoretical method. The results show that B3PW91 (LANL2DZ/6-31G*) combination give the best description of the molecules as compared with experimentally determined structural features. Using the calculation data from that best functional and mixed basis set combination, frontier molecular orbitals of the complexes have been examined. To gain understanding on the nature of electronic transitions in the UV-vis absorption spectra of the compounds, TD-DFT calculations have been carried out. A details analysis of the vertical excitation reveals that the nature of all the vertical electronic transitions in the complexes. Notably, the lowest energy transitions are π_cb + d_Pt → \(\pi _{{{\text{cb}}}}^{{\text{*}}}\) (for Pt¹ and Pt²) and π_CNC → d_Au + \(\pi _{{{\text{CNC}}}}^{{\text{*}}}\) (for Au¹ and Au²) charge transfer in nature. A sharp contrast in lowest energy triplet excited state for d⁸‑squared planar Au¹ and Pt¹ has been demonstrated. While no contribution from gold(III) d orbital to the SOMO and SOMO – 1 orbital of Au¹, there is significant contribution of platinum(II) d_yz orbital in the SOMO – 1 orbital of Pt¹, suggesting possible interaction of this singly occupied orbital with radical of π-symmetry substrates.

中文翻译：

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带有环金属化2,6-二苯基吡啶和P衍生的N-杂环卡宾的d 8-方形平面铂（II）和金（III）配合物的基态和激发态电子结构

摘要

从理论上研究了四个pyr衍生的N-杂环卡宾配合物的铂（II）和金（III）的环金属化2，6-二苯基吡啶的电子结构。气相中所有配合物的结构均已首先优化。已测试了不同的功能和基础集，以找到最佳的理论方法。结果表明，与实验确定的结构特征相比，B3PW91（LANL2DZ / 6-31G *）组合可提供最佳的分子描述。使用来自最佳功能和混合基集组合的计算数据，研究了配合物的前沿分子轨道。为了了解化合物在紫外可见吸收光谱中电子跃迁的性质，已进行了TD-DFT计算。垂直激发的详细分析表明，络合物中所有垂直电子跃迁的性质。值得注意的是，最低的能量跃迁为π_CB + d_的Pt → \（\ PI _ {{{\文本{CB}}}} ^ {{\文本{*}}} \）（对于铂¹和铂²）和π _CNC → d_的Au + \（ \ pi _ {{{{\ text {CNC}}}} ^ {{\ text {*}}} \\）（对于Au ¹和Au ²）本质上是电荷转移。已证明在d ⁸平方平面Au ¹和Pt ^1的最低能量三重态激发态中存在鲜明的对比。尽管金（III）d轨道对SOMO和SOMO无贡献– Au的1轨道^{如图1所示}，铂（II） d _yz轨道在Pt ¹的SOMO-1轨道中有重大贡献，表明该单占据的轨道与π对称底物的自由基可能发生相互作用。