Favale Joseph M, Hauke Cory E, Danilov Evgeny O, Yarnell James E, Castellano Felix N
Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204, USA.
Dalton Trans. 2020 Aug 7;49(29):9995-10002. doi: 10.1039/d0dt02100h. Epub 2020 Jul 9.
The manipulation of the triplet excited state manifold leads to large differences in the photophysical properties within a given class of metal-organic chromophores. By the appropriate choice of ancillary ligand, large changes can be made both to the order and nature of the lowest excited states and therefore to the resulting photophysical properties. Herein, a series of four bis-2-phenylpyridine (ppy) cyclometalated Ir(iii) compounds bearing two arylisocyanide ligands were synthesized and photophysically characterized to understand the effects of using ancillary ligands featuring systematic changes in π-conjugation. By varying the arylisocyanide ligands, the photoluminescence quantum yield ranged from 5% to 49% and the excited state lifetime ranged between 24 μs and 2 ms. These variations in photophysical response are consistent with lowering the triplet ligand-centered (LC) state of the arylisocyanide ligand as the π system was extended, confirmed by 77 K photoluminescence emission spectra and ultrafast transient absorption experiments. The latter analysis gleaned detailed insight into the importance of the interplay of the LC state of the phenylpyridine and arylisocyanide ligands in these polychromophic Ir(iii) molecules.
对三重激发态流形的操控会导致给定类别的金属有机发色团在光物理性质上产生很大差异。通过适当选择辅助配体，可以使最低激发态的顺序和性质发生很大变化，从而使光物理性质也发生相应变化。在此，合成了一系列四种带有两个芳基异氰化物配体的双 - 2 - 苯基吡啶（ppy）环金属化铱（III）化合物，并对其进行了光物理表征，以了解使用具有π共轭系统系统变化的辅助配体所产生的影响。通过改变芳基异氰化物配体，光致发光量子产率在5%至49%之间，激发态寿命在24 μs至2 ms之间。这些光物理响应的变化与随着π体系扩展芳基异氰化物配体的三重配体中心（LC）态降低相一致，这通过77 K光致发光发射光谱和超快瞬态吸收实验得到证实。后一种分析深入了解了在这些多色铱（III）分子中苯基吡啶和芳基异氰化物配体的LC态相互作用的重要性。
