Karlsson Joshua K G, Atahan Alparslan, Harriman Anthony, Tojo Sachiko, Fujitsuka Mamoru, Majima Tetsuro
Molecular Photonics Laboratory, School of Natural and Environmental Sciences (Chemistry) , Newcastle University , Bedson Building , Newcastle upon Tyne , NE1 7RU , United Kingdom and.
The Institute of Scientific and Industrial Research (SANKEN) , Osaka University , Ibaraki , Osaka 567-0047 , Japan.
J Phys Chem Lett. 2018 Jul 19;9(14):3934-3938. doi: 10.1021/acs.jpclett.8b02006. Epub 2018 Jul 3.
Exposing TIPS-pentacene in deaerated benzene to ionizing radiation generates a mixture of singlet- and triplet-excited states of the solute. The singlet undergoes radiative decay without spin conversion whereas the triplet undergoes radiationless decay on the microsecond time scale. The concentration of each species was established by dosimetry. The excited-singlet state is not observed on the nanosecond-time scale for a related fluorene-bridged bis(pentacene), but the triplet is present in high concentration. Failure to detect the excited-singlet state is attributed to fast intramolecular singlet-exciton fission (iSEF) which is found to produce two triplet species. A short-lived intermediate (τ = 145 ns) is identified as the species (T_T) having both pentacene units present as triplet states. The second transient is longer lived (τ = 7.5 μs) and is assigned to the corresponding species (T_G) with a single pentacene promoted to the triplet level. Dosimetry is used to conclude that iSEF partitions overwhelmingly in favor of T_G (70%) relative to T_T (25%). The total triplet yield from iSEF, therefore, is ca. 120% in this system, where the pentacene terminals are weakly coupled.
将TIPS-并五苯暴露于脱气苯中的电离辐射下会产生溶质的单线态和三线态激发态的混合物。单线态经历辐射衰变而不发生自旋转换，而三线态在微秒时间尺度上经历无辐射衰变。每种物质的浓度通过剂量测定法确定。对于相关的芴桥联双（并五苯），在纳秒时间尺度上未观察到激发单线态，但三线态以高浓度存在。未能检测到激发单线态归因于快速的分子内单线态激子裂变（iSEF），发现其产生两个三线态物质。一个短寿命中间体（τ = 145 ns）被确定为两个并五苯单元均以三线态存在的物质（T_T）。第二个瞬态寿命更长（τ = 7.5 μs），并被指定为单个并五苯被激发到三线态水平的相应物质（T_G）。剂量测定法用于得出结论，相对于T_T（25%），iSEF绝大多数情况下有利于T_G（70%）进行分配。因此，在这个并五苯末端弱耦合的体系中，iSEF产生的三线态总产率约为120%。
