Phthalocyanines (Pcs) and boron dipyrromethenes (BDPs) are two versatile classes of functional dyes suitable for design of artificial light harvesting and charge separation systems. In the present work, we report the results of photophysical investigations of two novel non-sandwich-type BDP-Pc heterotriads, in which two BDP or mono-styryl BDP moieties are linked to the central atom of a silicon(IV) phthalocyanine core (triad 4 and 5, respectively). It was found that the photophysical properties of the triads in toluene and N,N-dimethylformamide (DMF) are strongly affected by two different types of interaction between the BDP and the Pc parts, namely excitation energy transfer (EET) and photoinduced charge transfer (CT). The first process delivers the excitation to the first excited singlet state of the Pc-part upon initial BDP-part excitation. The probability of EET supersedes that of CT in toluene, whereas the latter transfer process dominates in BDP-part depopulation when triads are dissolved in polar DMF. The direct or indirect (via EET) population of Pc moiety is followed by the hole transfer to the charge-separated state in 4 (in DMF) and in 5 (in DMF and toluene). At the same time, it was found that CT is energetically unfavorable for the triad 4 in toluene upon excitation of the Pc-part. The charge-recombination in DMF occurs very fast with a decay time of 40 and 30 ps for 4 and 5, respectively, whereas toluene stabilizes the charge-separated state, prolonging the lifetime to 4.5 and 1.7 ns, respectively.
酞菁(Pcs)和
硼二
吡咯烷(
BDPs)是两种多功能功能
染料,适用于设计人工光收集和电荷分离系统。在本研究中,我们报告了两种新型非三明治型
BDP-Pc杂三聚体光物理研究的结果,其中两个
BDP或单
苯乙烯基
BDP部分与
硅(IV)
酞菁核心的中心原子相连(分别为三聚体4和5)。研究发现,三聚体在
甲苯和N,N-二甲基甲酰胺(
DMF)中的光物理性质受到
BDP和Pc部分之间两种不同相互作用类型(即激发能量转移(EET)和光诱导电荷转移(CT))的强烈影响。在初始
BDP部分激发时,第一个过程将激发传递到Pc部分的第一个激发单线态。在
甲苯中,EET的概率取代了CT的概率,而在三聚体溶解在极性
DMF中时,后者转移过程在
BDP部分去饱和中占主导地位。Pc部分的直接或间接(通过EET)填充之后,空穴转移到4(在
DMF中)和5(在
DMF和
甲苯中)的电荷分离状态。同时,研究发现,在Pc部分激发时,CT在能量上不利于
甲苯中的三聚体4。
DMF中的电荷复合发生得非常快,4