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Cyclopentadithiophene derivatives: a step towards an understanding of thiophene copolymer excited state deactivation pathways†
Materials Chemistry Frontiers ( IF 6.0 ) Pub Date : 2017-11-10 00:00:00 , DOI: 10.1039/c7qm00440k
João Pina 1, 2, 3, 4, 5 , Anika Eckert 6, 7, 7, 8, 9 , Ullrich Scherf 6, 7, 7, 8, 9 , Adelino M. Galvão 5, 10, 11, 12 , J. Sérgio Seixas de Melo 1, 2, 3, 4, 5
Affiliation  

We have carried out the excited state characterization of cyclopentadithiophene (CPDT) and its didodecyl-substituted derivative (C12CPDT) to obtain detailed insights into their photophysical pathways. These are the cis analogues of α,α′-bithiophene (α2), which normally exists in the more stable s-trans geometry. We report absorption, fluorescence, phosphorescence, and triplet-singlet difference spectra, together with quantum yields (fluorescence, phosphorescence and singlet oxygen). Fast time-resolved fluorescence and transient absorption techniques (ps-TCSPC and fs-TA) were used to characterize the initial excited state dynamics of the CPDTs and α2. In general, the two CPDTs show similar spectral and photophysical properties to α2, although phosphorescence is absent in α2 (the trans conformer). From TDDFT calculations it is shown that the large Stokes shift (SS) observed for CPDT and C12CPDT (planar in S0 and S1) is due to a bond length change in the C–C bond connecting the two thiophene units, which decreases from 146 to 137 pm. With α2 this change is accompanied by a change in the dihedral angle (25.5° in S0 to 0.2° in S1).

中文翻译:

环戊二噻吩衍生物:迈向了解噻吩共聚物激发态失活途径的一步

我们已经进行了环戊二噻吩(CPDT)及其双十二烷基取代衍生物(C 12 CPDT)的激发态表征,以了解其光物理途径的详细见解。这些是α,α'-联噻吩(α2)的顺式类似物,通常以更稳定的反式存在几何学。我们报告了吸收,荧光,磷光和三重态-单重谱的差异,以及量子产率(荧光,磷光和单线态氧)。快速时间分辨荧光和瞬态吸收技术(ps-TCSPC和fs-TA)用于表征CPDT和α2的初始激发态动力学。通常,两个CPDT显示出与α2相似的光谱和光物理性质,尽管α2(反式构象体)中不存在磷光。从TDDFT计算中可以看出,对于CPDT和C 12 CPDT(在S 0和S 1中为平面),观察到了较大的斯托克斯位移(SS))是由于连接两个噻吩单元的C–C键的键长变化从146 pm降至137 pm。对于α2,此变化伴随着二面角的变化(S 0中为25.5°到S 1中为0.2° )。
更新日期:2017-11-10
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