Polak Daniel W, Andrews Iain, Salvadori Enrico, Musser Andrew J, Auty Alexander, Chekulaev Dimitri, Weinstein Julia A, Heeney Martin, Clark Jenny
Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield S3 7RH, U.K.
Department of Chemistry and Centre for Processable Electronics, Imperial College London, White City Campus, London W12 0BZ, U.K.
J Am Chem Soc. 2025 Jan 8;147(1):662-668. doi: 10.1021/jacs.4c12877. Epub 2024 Dec 23.
Activated intramolecular singlet fission is known to occur in the conjugated polymer polythienylene-vinylene (P3TV). Instead, efficient intersystem crossing has been observed in a short 3-alkyl(thienylene-vinylene) dimer. Here, we investigate a series of oligomers covering the conjugation length gap between the dimer and polymer. We confirm that the polymer and longer oligomers undergo activated intramolecular singlet fission, while the shorter oligomers with less than 3 units predominantly undergo efficient intersystem crossing. For the longer oligomers, the intermediate state of singlet fission is assigned to the 3A covalent state of triplet pair character, as predicted by several computational studies. Our results point to potential pitfalls when assigning triplet production pathways solely with transient absorption spectroscopy.
已知活化的分子内单线态裂变会在共轭聚合物聚噻吩撑乙烯（P3TV）中发生。相反，在一种短链的3-烷基（噻吩撑乙烯）二聚体中观察到了高效的系间窜越。在此，我们研究了一系列覆盖二聚体和聚合物之间共轭长度差距的低聚物。我们证实，聚合物和较长的低聚物会发生活化的分子内单线态裂变，而少于3个单元的较短低聚物主要发生高效的系间窜越。对于较长的低聚物，单线态裂变的中间态被指定为具有三重态对特征的3A共价态，这与几项计算研究的预测一致。我们的结果指出了仅用瞬态吸收光谱法确定三重态产生途径时可能存在的陷阱。
