McCusker Catherine E, Castellano Felix N
Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, North Carolina 27695, United States.
Inorg Chem. 2015 Jun 15;54(12):6035-42. doi: 10.1021/acs.inorgchem.5b00907. Epub 2015 Jun 2.
The current investigation compares the photochemical upconversion sensitization properties of two long lifetime Cu(I) metal-to-ligand charge transfer (MLCT) chromophores to 3 distinct anthryl-based triplet acceptors. The sensitizers Cu(dsbtmp)2 (1, dsbtmp = 2,9-di(sec-butyl)-3,4,7,8-tetramethyl-1,10-phenanthroline) and Cu(dsbp)2 (2, dsbp = 2,9-di(sec-butyl-1,10-phenanthroline) were selectively excited in the presence of anthracene, 9,10-diphenylanthracene (DPA), and 9,10-dimethylanthracene (DMA) in degassed dichloromethane solutions. In all instances, triplet energy transfer was observed from selective excitation of the Cu(I) MLCT chromophore to each respective anthryl species. The bimolecular triplet-triplet energy transfer quenching rate constants were extracted from dynamic Stern-Volmer analyses in each case, yielding values below the diffusion limit in dichloromethane. However, the Stern-Volmer quenching constants (KSV's) were sizable enough (up to ∼2300 M(-1) with 1 as a sensitizer) to support efficient photochemical upconversion. As such, visible to near-UV photochemical upconversion was observed in every instance, along with the anticipated quadratic-to-linear incident light power dependence when pumping at 488 nm. The latter verified that it is indeed sensitized triplet-triplet annihilation responsible for the generation of the anthryl-based singlet fluorescence. Photochemical upconversion quantum efficiencies were evaluated using a relative actinometric method as both a function of incident light power density as well as anthryl acceptor/annihilator concentration. When 1 was used as the sensitizer, upconversion quantum yields as large as 9.2% and 17.8% were observed for DMA and DPA, respectively. Finally, the combination of 1 with DMA was shown to be quite robust, showing no obvious signs of decomposition during 12 h of continuous 488 nm photolysis.
当前的研究比较了两种具有长寿命的铜（I）金属到配体电荷转移（MLCT）发色团与三种不同的基于蒽的三重态受体的光化学上转换敏化特性。在脱气的二氯甲烷溶液中，在蒽、9,10-二苯基蒽（DPA）和9,10-二甲基蒽（DMA）存在的情况下，对敏化剂Cu(dsbtmp)2（1，dsbtmp = 2,9-二（仲丁基）-3,4,7,8-四甲基-1,10-菲咯啉）和Cu(dsbp)2（2，dsbp = 2,9-二（仲丁基）-1,10-菲咯啉）进行选择性激发。在所有情况下，均观察到从铜（I）MLCT发色团的选择性激发到各自的蒽基物种的三重态能量转移。通过动态斯特恩-沃尔默分析分别提取了双分子三重态-三重态能量转移猝灭速率常数，得到的值低于二氯甲烷中的扩散极限。然而，斯特恩-沃尔默猝灭常数（KSV's）足够大（以1作为敏化剂时高达约2300 M(-1)），以支持有效的光化学上转换。因此，在每种情况下都观察到了可见光到近紫外光的光化学上转换，以及在488 nm泵浦时预期的二次到线性入射光功率依赖性。后者证实了确实是敏化的三重态-三重态湮灭导致了基于蒽的单重态荧光的产生。使用相对光度测量法评估了光化学上转换量子效率，该效率是入射光功率密度以及蒽基受体/湮灭剂浓度的函数。当使用1作为敏化剂时，对于DMA和DPA，分别观察到高达9.2%和17.8%的上转换量子产率。最后，1与DMA的组合显示出相当稳定，在连续488 nm光解12小时期间没有明显的分解迹象。
