Excited‐State Dynamics in Segregated Donor‐Acceptor Stacks Versus a Peri‐Bisdonor‐Acceptor System

Abstract

AbstractThe investigation of impact of through‐space/through‐bond electronic interaction among chromophores on photoexcited‐state properties has immense potential owing to the distinct emergent photophysical pathways. Herein, the photoexcited‐state dynamics of homo‐sorted π‐stacked aggregates of a naphthalenemonoimide and perylene‐based acceptor‐donor (NI‐Pe) system and a fork‐shaped acceptor‐bisdonor (NI‐Pe2) system possessing integrally stacked peri‐substituted donors was examined. Femtosecond transient absorption (fsTA) spectra of NI‐Pe monomer recorded in chloroform displayed spectroscopic signatures of the singlet state of Pe; 1Pe*, the charge‐separated state; NI−⋅‐Pe+⋅, and the triplet state of Pe; 3Pe*. The examination of ultrafast excited‐state processes of NI‐Pe aggregate in chloroform revealed faster charge recombination ( =1.75 ns) than the corresponding monomer ( =2.46 ns) which was followed by observation of a broad structureless band attributed to an excimer‐like state. The fork‐shaped NI‐Pe2 displayed characteristic spectroscopic features of the NI radical anion (λmax~450 nm) and perylene dimer radical cation (λmax~520 nm) upon photoexcitation in non‐polar toluene solvent in the nanosecond transient absorption (nsTA) spectroscopy. The investigation highlights the significance of intrinsic close‐stacked arrangement of donors in ensuring a long‐lived photoinduced charge‐separated state ( =1.35 μs) in non‐polar solvents via delocalization of radical cation between the donors.