Abstract

A series of neutral and anionic platinum(II) complexes bearing Janus-type N-Heterocyclic carbenes (NHC) with different extents of π conjugation were constructed theoretically by bridging two cyclometallated platinum(II) centers using diNHC linkers. The diNHCs bind to Pt(II) in either in monodentate (neutral complex I, II) or bidentate (anionic complex III−V) fashion. Structures of all complexes were first optimized. Single point and TD-DFT calculations have been carried out using the gas-phased optimized geometries to gain insight into their electronic structures, possible electronic transitions, and to probe the influence of diNHC ligand design on the photo-responsiveness of the complexes. The response of complexes I−III is limited to UV light; however, complexes IV and V, which contain cyclometallated diNHCs, exhibit absorption bands in the visible region. Additionally, the emissive triplet excited state and the metal-center triplet excited states (³MC) were also investigated. Interestingly, the results suggest that the internal conversion triplet excited state to ³MC in I and III, which induces significant coordination geometry distortion, is energetically favorable for complexes I and III suggesting potentially photo-enhanced reactivities of these two complexes.

中文翻译：

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Janus型N-杂环卡宾双核铂(II)配合物的电子结构和光致几何畸变：理论研究

摘要

通过使用 diNHC 连接体桥接两个环金属化铂 (II) 中心，理论上构建了一系列具有不同 π 共轭程度的 Janus 型 N-杂环卡宾 (NHC) 的中性和阴离子铂 (II) 配合物。diNHC 以单齿（中性络合物I、II）或双齿（阴离子络合物III – V）方式与 Pt(II) 结合。首先对所有复合体的结构进行了优化。使用气相优化的几何结构进行了单点和 TD-DFT 计算，以深入了解其电子结构、可能的电子跃迁，并探讨 diNHC 配体设计对配合物光响应性的影响。配合物I – III的响应仅限于紫外光；然而，含有环金属化 diNHC 的配合物IV和V在可见光区域表现出吸收带。此外，还研究了发射三重激发态和金属中心三重激发态（^{3 MC）。}有趣的是，结果表明，I和III中三重激发态内部转换为³ MC ，这会引起显着的配位几何畸变，在能量上有利于配合物I和III，表明这两种配合物的潜在光增强反应性。