Three centrosymmetric diketopyrrolopyrroles possessing either two 2-(2′-methoxyphenyl)benzothiazole or two 2-(2′-methoxyphenyl)benzoxazolo-thiophene scaffolds were synthesized in a straightforward manner, and their photophysical properties were investigated. Their emission was significantly bathochromically shifted as compared with that of simple DPPs reaching 650 nm. Judging from theoretical calculations performed with time-dependent density functional theory, in all three cases the excited state was localized on the DPP core and there was no significant CT character. Consequently, emission was almost independent of solvents’ polarity. DPPs possessing 2,5-thiophene units vicinal to DPP core play a role in electronic transitions, resulting in bathochromically shifted absorption and emission. Interestingly, as judged from transient absorption dynamics, intersystem crossing was responsible for the deactivation of the excited states of DPPs possessing para linkers but not in the case of dye bearing meta linker.
三种具有两个2-(2'-
甲氧基苯基)
苯并噻唑或两个2-(2'-
甲氧基苯基)苯并
噁唑-
噻吩骨架的中心对称的二酮
吡咯烯被以直接的方式合成,并且研究了它们的光物理性质。与简单的
DPP相比,它们的发射明显向红移,达到了650纳米。根据用时变密度泛函理论进行的理论计算,在所有三种情况下,激发态局限于
DPP核心,并且没有明显的CT特性。因此,发射几乎不受溶剂极性的影响。具有
DPP核心邻位2,5-
噻吩单元的
DPP在电子跃迁中发挥作用,导致吸收和发射向红移。有趣的是,根据瞬态吸收动力学的判断,跃迁系统交叉导致了具有对位连接子的
DPP的激发态的失活,但在具有间位连接子的
染料的情况下并非如此。