Excited Charge Transfer Promoted Electron Transfer in all Perylenediimide Derived, Wide‐Band Capturing Conjugates: A Mimicry of the Early Events of Natural Photosynthesis

Abstract

Fundamental discoveries in electron transfer advance scientific and technological advancements. It is suggested that in plant photosynthesis, the primary donor, a chlorophyll dimer forms an initial excited symmetry‐breaking charge transfer state (1CT*) upon photoexcitation that subsequently promotes sequential electron transfer (ET) events. In the present study, we demonstrate the former photochemical event using an excited charge transfer molecule as a donor. For this, electron‐deficient perylenediimide (PDI) is functionalized with three electron‐rich piperidine entities at the bay positions resulting in a far‐red emitting CT molecule (DCT). Further, this molecule is covalently linked to another PDI (APDI) carrying no substituents at the bay positions resulting in wide‐band capturing DCT‐APDI conjugates. Selective excitation of the CT band of DCT in these conjugates leads to an initial 1DCT* that undergoes subsequent ET involving APDI resulting in DCT.+‐ APDI.‐ charge separation product (kCS ~ 109 s‐1). Conversely, when APDI was directly excited, ultrafast energy transfer (ENT) from 1APDI* to DCT (kENT ~ 1011 s‐1) followed by ET from 1DCT* to PDI is witnessed. The present findings, are key to understanding the intricate ET events taking place in complex natural photosynthetic systems possessing multiple photoactive entities.