Jensen Jesper Dahl, Louie Shayan, He Yanmei, Chen Junsheng, Nuckolls Colin, Laursen Bo W
Nano-Science Center & Department of Chemistry, University of Copenhagen Universitetsparken 5, DK-2100 Copenhagen Ø Denmark
Department of Chemistry, Columbia University, New York New York 10027 USA.
Chem Sci. 2025 Apr 23;16(21):9525-9534. doi: 10.1039/d5sc01397f. eCollection 2025 May 28.
In this manuscript, we create a new hetero dyad consisting of two electron acceptors with nearly isoenergetic HOMO and LUMO levels, namely perylene diimide (PDI) and aza dioxa triangulenium (ADOTA). This dyad system displays an unusual and reversible excited state electron transfer process. Upon excitation, the dyad shows complete energy transfer from the locally excited PDI to the ADOTA moiety in ∼1 ps, followed by photoinduced electron transfer (PET), forming oxidized PDI and reduced ADOTA. While this PET process is fast ( ≈ 150 ps), the reversibility establishes an equilibrium between fluorescent locally excited ADOTA and the dark charge shifted PET state. We investigate the formation of and decay from this unusual reversible excited state electron transfer system by fs transient absorption and time-resolved fluorescence spectroscopy in different solvent mixtures because the solvent modulates the deactivation rate of the PET state. Electrochemistry confirms that both the local HOMOs and LUMOs of PDI and ADOTA are nearly isoenergetic but can be shifted by solvent polarity, which elucidates the reason for the unusual reversible electron transfer process and its sensitivity to the solvent. We further investigate near degeneracy of the LUMOs through spectroscopy of the chemically reduced dyad. We find that there is an equilibrium between the reduction of the cationic ADOTA to a neutral dyad, which is favored in DCM. However, in DMF, we find reduction of the PDI leads to formation of the zwitterionic dyad.
在本论文中，我们构建了一种新型异质二聚体，它由两个具有近乎等能量的最高占据分子轨道（HOMO）和最低未占据分子轨道（LUMO）的电子受体组成，即苝二酰亚胺（PDI）和氮杂二氧杂三角鎓（ADOTA）。该二聚体系统展现出一种不同寻常且可逆的激发态电子转移过程。激发后，二聚体在约1皮秒内显示出从局部激发的PDI到ADOTA部分的完全能量转移，随后发生光诱导电子转移（PET），形成氧化的PDI和还原的ADOTA。虽然这个PET过程很快（约150皮秒），但其可逆性在荧光局部激发的ADOTA和暗电荷转移的PET态之间建立了平衡。我们通过飞秒瞬态吸收光谱和时间分辨荧光光谱在不同溶剂混合物中研究了这种不同寻常的可逆激发态电子转移系统的形成和衰减，因为溶剂会调节PET态的失活速率。电化学证实PDI和ADOTA的局部HOMO和LUMO几乎是等能量的，但可被溶剂极性移动，这阐明了这种不同寻常的可逆电子转移过程及其对溶剂敏感的原因。我们通过化学还原二聚体的光谱进一步研究了LUMO的近简并性。我们发现阳离子ADOTA还原为中性二聚体之间存在平衡，这在二氯甲烷（DCM）中更有利。然而，在N,N - 二甲基甲酰胺（DMF）中，我们发现PDI的还原导致两性离子二聚体的形成。
