Guzmán David, Papadopoulos Ilias, Lavarda Giulia, Rami Parisa R, Tykwinski Rik R, Rodríguez-Morgade M Salomé, Guldi Dirk M, Torres Tomás
Departamento de Química Orgánica, Universidad Autónoma de Madrid, Cantoblanco, 28049, Madrid, Spain.
Department of Chemistry and Pharmacy, Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058, Erlangen, Germany.
Angew Chem Int Ed Engl. 2021 Jan 18;60(3):1474-1481. doi: 10.1002/anie.202011197. Epub 2020 Nov 18.
Due its complementary absorptions in the range of 450 and 600 nm, an energy-donating hexaaryl-subporphyrazine has been linked to a pentacene dimer, which acts primarily as an energy acceptor and secondarily as a singlet fission enabler. In the corresponding conjugate, efficient intramolecular Förster resonance energy transfer (i-FRET) is the modus operandi to transfer energy from the subporphyrazine to the pentacene dimer. Upon energy transfer, the pentacene dimer undergoes intramolecular singlet fission (i-SF), that is, converting the singlet excited state, via an intermediate state, into a pair of correlated triplet excited states. Solvatochromic fluorescence of the subporphyrazine is a key feature of this system and features a red-shift as large as 20 nm in polar media. Solvent is thus used to modulate spectral overlap between the fluorescence of subporphyrazine and absorption of the pentacene dimer, which controls the Förster rate constant, on one hand, and the triplet quantum yield, on the other hand. The optimum spectral overlap is realized in xylene, leading to Förster rate constant of 3.52×10 s and a triplet quantum yield of 171 % ±10 %. In short, the solvent polarity dependence, which is a unique feature of subporphyrazines, is decisive in terms of adjusting spectral overlap, ensuring a sizable Förster rate constant, and maximizing triplet quantum yields. Uniquely, this optimization can be achieved without a need for synthetic modification of the subporphyrazine donor.
由于其在450至600纳米范围内的互补吸收，一种供能的六芳基取代亚卟啉与并五苯二聚体相连，该并五苯二聚体主要作为能量受体，其次作为单线态裂变促进剂。在相应的共轭物中，高效的分子内福斯特共振能量转移（i-FRET）是将能量从亚卟啉转移到并五苯二聚体的作用方式。能量转移后，并五苯二聚体发生分子内单线态裂变（i-SF），即通过一个中间态将单线态激发态转化为一对相关的三线态激发态。亚卟啉的溶剂化显色荧光是该系统的一个关键特征，在极性介质中具有高达20纳米的红移。因此，溶剂一方面用于调节亚卟啉荧光与并五苯二聚体吸收之间的光谱重叠，从而控制福斯特速率常数；另一方面用于调节三线态量子产率。在二甲苯中实现了最佳的光谱重叠，导致福斯特速率常数为3.52×10 s，三线态量子产率为171%±10%。简而言之，亚卟啉独特的溶剂极性依赖性在调整光谱重叠、确保可观的福斯特速率常数以及最大化三线态量子产率方面起着决定性作用。独特的是，这种优化无需对亚卟啉供体进行合成修饰即可实现。
