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Excited-state structure of copper phenanthroline-based photosensitizers
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2021-11-15 , DOI: 10.1039/d1cp02823e
Alexander Guda 1 , Johannes Windisch 2 , Benjamin Probst 2 , Jeroen A van Bokhoven 3, 4 , Roger Alberto 2 , Maarten Nachtegaal 3 , Lin X Chen 5, 6 , Grigory Smolentsev 3
Affiliation  

Cu diimine complexes present a noble metal free alternative to classical Ru, Re, Ir and Pt based photosensitizers in solution photochemistry, photoelectrochemical or dye-sensitized solar cells. Optimization of these dyes requires understanding of factors governing the key photochemical properties: excited state lifetime and emission quantum yield. The involvement of exciplex formation in the deactivation of the photoexcited state is a key question. We investigate the excited-state structure of [Cu(dmp)2]+ and [Cu(dsbtmp)2]+ (dmp = 2,9-dimethyl-1,10-phenanthroline, dsbtmp = 2,9-di-sec-butyl-3,4,7,8-tetramethyl-1,10-phenanthroline) using pump–probe X-ray absorption spectroscopy (XAS) and DFT. Features of XAS that distinguish flattened tetrahedral site and 5-coordinated geometry with an additional solvent near Cu(II) center are identified. Pump–probe XAS demonstrates that for both complexes the excited state is 4-coordinated. For [Cu(dmp)2]+ the exciplex is 0.24 eV higher in energy than the flattened triplet state, therefore it can be involved in deactivation pathways as a non-observable state that forms slower than it decays. For [Cu(dsbtmp)2]+ the excited-state structure is characterized by Cu–N distances of 1.98 and 2.07 Å and minor distortions, leading to a 3 orders of magnitude longer excited-state lifetime.

中文翻译:

菲咯啉铜基光敏剂的激发态结构

Cu 二亚胺配合物是溶液光化学、光电化学或染料敏化太阳能电池中经典 Ru、Re、Ir 和 Pt 基光敏剂的无贵金属替代品。这些染料的优化需要了解控制关键光化学特性的因素:激发态寿命和发射量子产率。激基复合物的形成参与光激发态的失活是一个关键问题。我们研究了 [Cu(dmp) 2 ] +和 [Cu(dsbtmp) 2 ] + (dmp = 2,9-二甲基-1,10-菲咯啉,dsbtmp = 2,9-di- sec-丁基-3,4,7,8-四甲基-1,10-菲咯啉)使用泵-探针 X 射线吸收光谱 (XAS) 和 DFT。确定了 XAS 的特征,该特征区分扁平四面体位点和 5 配位几何结构,在 Cu( II ) 中心附近有额外的溶剂。泵-探针 XAS 表明,对于这两种配合物,激发态都是 4 配位的。对于 [Cu(dmp) 2 ] +激基复合物的能量比平坦的三重态高 0.24 eV,因此它可以作为一种不可观察的状态参与失活途径,其形成速度比衰变慢。对于 [Cu(dsbtmp) 2 ] + 激发态结构的特征是 1.98 和 2.07 Å 的 Cu-N 距离和轻微的畸变,导致激发态寿命长 3 个数量级。
更新日期:2021-11-30
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