Guest and solvent modulated photo-driven charge separation and triplet generation in a perylene bisimide cyclophane.

ABSTRACT: Cofacial positioning of two perylene bisimide (PBI) chromophores at a distance of 6.5 Å in a cyclophane structure prohibits the otherwise common excimer formation and directs photoexcited singlet state relaxation towards intramolecular symmetry-breaking charge separation (τ_CS = 161 ± 4 ps) in polar CH₂Cl₂, which is thermodynamically favored with a Gibbs free energy of ΔG_CS = -0.32 eV. The charges then recombine slowly in τ_CR = 8.90 ± 0.06 ns to form the PBI triplet excited state, which can be used subsequently to generate singlet oxygen in 27% quantum yield. This sequence of events is eliminated by dissolving the PBI cyclophane in non-polar toluene, where only excited singlet state decay occurs. In contrast, comple

SUBMITTER: Spenst P 

PROVIDER: S-EPMC6021749 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature