Ultrafast Photoinduced Symmetry-Breaking Charge Separation and Electron Sharing in Perylenediimide Molecular Triangles

Abstract

We report on a visible-light-absorbing chiral molecular triangle composed of three covalently linked 1,6,7,12-tetra(phenoxy)perylene-3,4:9,10-bis(dicarboximide) (PDI) units. The rigid triangular architecture reduces the electronic coupling between the PDIs, so ultrafast symmetry-breaking charge separation is kinetically favored over intramolecular excimer formation, as revealed by femtosecond transient absorption spectroscopy. Photoexcitation of the PDI triangle dissolved in CH2Cl2 gives PDI(+•)-PDI(-•) in τCS = 12.0 ± 0.2 ps. Fast subsequent intramolecular electron/hole hopping can equilibrate the six possible energetically degenerate ion-pair states, as suggested by electron paramagnetic resonance/electron-nuclear double resonance spectroscopy, which shows that one-electron reduction of the PDI triangle results in complete electron sharing among the three PDIs. Charge recombination of PDI(+•)-PDI(-•) to the ground state occurs in τCR = 1.12 ± 0.01 ns with no evidence of triplet excited state formation.

Thionated perylene diimides with intense absorbance in the near-IR

“…1,2 These properties have led to their exploitation in various applications such as organic field-effect transistors, chemical sensors, 3 thin-film transistors, 4 complex supramolecular systems 5,6 and, increasingly, organic photovoltaics (OPVs). 7 Recent interest in OPVs has begun to outstrip that of traditional silicon based solar cells due to their low cost, synthetic adaptability and processing ability.…”

Templated Chromophore Assembly on Peptide Scaffolds: A Structural Evolution

“…[5] The supramolecular mixingo fd yes, [6] affording organogels, [7] supramolecular polymers, [8] co-crystals, [9] metal-organic frameworks, [10] is av ery handy approach for engineering simple LH systems( dyads) with high donor-to-acceptorr atios. On the other hand, the covalenta ssembly of dyes offers ac ontrolled route as chromophores can be assembled into robust multidimensionala rchitectures such as multilayers, [11] dendrimers [12] and macrocycles, [13] through either static or dynamic covalent linkages, [11d,e, 14] allowing for the efficient light collection and energy-transfer control. Recently,t he use of ap re-organized template (e.g.,p roteins, [15] nucleic acids, [15a, 16] micelles, [17] inorganic scaffolds) [18] to organize distinct chromophores has been widely explored for light harvesting.…”

Solvent tuning of photochemistry upon excited-state symmetry breaking

“…Excitedstate symmetry breaking (ES-SB) can be viewed as the decoherence of a multipolar exciton evenly delocalized over all branches of the molecule that eventually results in its confinement on a single branch. This phenomenon has seen a growing interest over the past few years, and was extensively investigated in linear quadrupolar rod-like molecules [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] . Attempts to identify a spectroscopic signature of ES-SB using electronic transient absorption in the UV-Vis region failed, because localized and delocalized states exhibit similar spectra 39,[45][46][47][48] .…”