Zhang Yuzhen, Hauke Cory E, Crawley Matthew R, Schurr Bradley E, Fulong Cressa Ria P, Cook Timothy R
Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260, USA.
Dalton Trans. 2017 Aug 14;46(30):9794-9800. doi: 10.1039/c7dt01817g. Epub 2017 Jul 5.
The emission of platinum-alkynyl complexes with terminal pyridyl moieties changes upon simple alkylation reactions. Due to growing interest in photovoltaics, photocatalysis, and light-emitting devices, understanding the nature of these changes is important to develop simple synthetic pathways for the rational design of photophysically active molecules. Herein, the choice of ligand isomer, methylation, and Pt-coordination environment on phosphorescent quantum yields, lifetimes, and associated radiative and non-radiative rate constants of eight organometallic complexes were studied. Single-crystal X-ray diffraction experiments and computational studies provide evidence for stabilization of metallo-cumulene resonance forms whose increased rigidities manifest in the observed photophysical changes. This effect is more pronounced for 4-ethynylpyridyl complexes over 3-ethynylpyridyl variants since the metallo-cumulene form shifts electron density to the electronegative N-atom at the para site. Furthermore, the use of σ-donating N-heterocyclic carbenes to complete the Pt-coordination environment enhanced the quantum yield of phosphorescence as high as 39% (λ = 512 nm) with a lifetime of 21.2 μs.
带有末端吡啶基部分的铂 - 炔基配合物的发射在简单的烷基化反应后会发生变化。由于对光伏、光催化和发光器件的兴趣日益增加，了解这些变化的本质对于开发用于合理设计光物理活性分子的简单合成途径很重要。在此，研究了配体异构体的选择、甲基化以及铂配位环境对八种有机金属配合物的磷光量子产率、寿命以及相关的辐射和非辐射速率常数的影响。单晶X射线衍射实验和计算研究为金属累积烯共振形式的稳定提供了证据，其增加的刚性在观察到的光物理变化中表现出来。对于4 - 乙炔基吡啶配合物，这种效应比3 - 乙炔基吡啶变体更明显，因为金属累积烯形式将电子密度转移到对位的电负性氮原子上。此外，使用给σ电子的N - 杂环卡宾来完成铂配位环境，使磷光量子产率提高到高达39%（λ = 512 nm），寿命为21.2 μs。
