Fonseca S M, Pina J, Arnaut L G, Seixas de Melo J, Burrows H D, Chattopadhyay N, Alcacer L, Charas A, Morgado J, Monkman A P, Asawapirom U, Scherf U, Edge R, Navaratnam S
Departamento de Química, Universidade de Coimbra, 3004-535 Coimbra, Portugal.
J Phys Chem B. 2006 Apr 27;110(16):8278-83. doi: 10.1021/jp060251f.
Data are reported on the triplet states of a series of fluorene-based A-alt-B type alternating copolymers based on pulse radiolysis-energy transfer and flash photolysis experiments. From the pulse radiolysis experiments, spectra are given for eight copolymers involving phenylene, thiophene, benzothiadiazole, and oligothienylenevinylene groups. Quantum yields for triplet-state formation (PhiT) have been obtained by flash photolysis following laser excitation and in one case by photoacoustic calorimetry. In addition, yields of sensitized formation of singlet oxygen have been determined by time-resolved phosphorescence and are, in general, in excellent agreement with the PhiT values. In all cases, the presence of thiophene units is seen to increase intersystem-crossing quantum yields, probably because of the presence of the heavy sulfur atom. However, with the poly[2,7-(9,9-bis(2'-ethylhexyl)fluorene)-alt-1,4-phenylene] (PFP), thiophene S,S-dioxide (PFTSO2) and benzothiadiazole (F8BT) copolymers, low yields of triplet formation are observed. With three of the copolymers, the energies of the triplet states have been determined. With PFP, the triplet energy is virtually identical to that of poly[2,7-(9,9-bis(2'-ethylhexyl)fluorene)]. In contrast, with fluorene-thiophene copolymers PFaT and PF3T, the triplet energies are closer to those of thiophene oligomers, indicating that there is significant conjugation between fluorene and thiophene units but also that there is a more localized triplet state than with the homopolymers.
基于脉冲辐解 - 能量转移和闪光光解实验，报道了一系列芴基A-alt-B型交替共聚物的三重态数据。通过脉冲辐解实验，给出了八种包含亚苯基、噻吩、苯并噻二唑和低聚噻吩亚乙烯基基团的共聚物的光谱。三重态形成的量子产率（PhiT）通过激光激发后的闪光光解获得，在一种情况下通过光声量热法获得。此外，单线态氧敏化形成的产率通过时间分辨磷光测定，并且总体上与PhiT值非常吻合。在所有情况下，都观察到噻吩单元的存在会增加系间窜越量子产率，这可能是由于重硫原子的存在。然而，对于聚[2,7-(9,9-双(2'-乙基己基)芴)-alt-1,4-亚苯基]（PFP）、噻吩S,S-二氧化物（PFTSO2）和苯并噻二唑（F8BT）共聚物，观察到三重态形成的产率较低。对于其中三种共聚物，已经测定了三重态的能量。对于PFP，三重态能量实际上与聚[2,7-(9,9-双(2'-乙基己基)芴)]的能量相同。相比之下，对于芴 - 噻吩共聚物PFaT和PF3T，三重态能量更接近噻吩低聚物的能量，这表明芴和噻吩单元之间存在显著的共轭，但也表明存在比均聚物更局域化的三重态。
