New and Efficient Arrays for Photoinduced Charge Separation Based on Perylene Bisimide and Corroles

Abstract

The bichromophoric systems C2-PI, C3-PI, and C3-PPI consisting of corrole and perylene bisimide units and representing one of the rare cases of elaborate structures based on corrole, have been synthesized. Corroles C2 and C3 are, respectively, meso-substituted corroles with 2,6-dichlorophenyl and pentafluorophenyl substituents at the 5 and 15 positions. The three dyads were prepared by divergent strategy with the corrole-forming reaction as the last step of the sequence. C2-PI and C3-PI differ in the nature of the corroles, whereas C3-PI differs from C3-PPI in the presence of a further phenyl unit in the linker between photoactive units. The dyads display spectroscopic properties which are the superposition of the component spectra, indicating a very weak electronic coupling. Excitation of the corrole unit leads to charge separation with a rate which decreases from 2.4 x 10(10), to 5.0 x 10(9), and to 4.9 x 10(7) s(-1) for C2-PI, C3-PI, and C3-PPI, respectively, where the reaction is characterized by a delta G degrees >0. Excitation of the perylene bisimide unit is followed by competing reactions of: 1) energy transfer to the corrole unit, which subsequently deactivates to the charge-separated state and; 2) electron transfer to directly form the charge-separated state. The ratio of electron-to-energy-transfer rates is 9:1 and 1:1 for C3-PI and C3-PPI, respectively. The yield of charge separation is essentially 100 % for C2-PI and C3-PI, and approximately 50 % (excitation of peryleneimide) or 15 % (excitation of the corrole) for C3-PPI. The lifetime of the charge-separated state, observed for the first time in corrole-based structures, is 540 ps for C2-PI, 2.5 ns for C3-PI, and 24 ns for C3-PPI, respectively. This is in agreement with an inverted behavior, according to Marcus theory.

Synthetic, Structural, and Photophysical Exploration of meso‐Pyrimidinyl‐Substituted AB2‐Corroles

“…[32] In the compounds studied here it can therefore be reasonable that a CT state that involves the corrole ring as the donor subunit-it is known that corroles are able to play the role of electron donor in chargeseparated processes [33] and, in general, to be oxidized at relatively mild potentials [34] -and the pyrimidinyl group as the acceptor can lie at a similar energy as the emitting p-p* corrole-based excited state and contribute to deactivation of the excited state by means of nonradiative processes, even without perturbing the luminescence spectra. In fact, upperlying states can have an effect on the dynamic properties of lower-lying excited states, even in the absence of sizeable perturbation of excited-state level energies.…”

Functional Arrays for Light Energy Capture and Charge Separation

“…The array could still be improved with respect to the absorption properties; in fact, by using a perylene bisimide as electron acceptor, the redox properties were almost unaltered whereas light absorption in the 450–550 nm range increased greatly for the contribution of the bisimide (Figure ) 57. We tested two dyads with short or long spacers, in order to establish the better construct to be used as a building block for more complex structures.…”

Two-photon absorption spectroscopy of corroles

“…Compared to porphyrins, the corroles exhibit several interesting properties, such as higher fluorescence quantum yield, larger Stokes shift, absence of phosphorescence, and increased extinction in the red part of the spectrum. Coordination chemistry [28], synthesis [29], chemical transformations [30], electrochemistry [31] and various applications [32], as well as basic photophysical properties of corroles [33][34][35] have been reported. However, to our best knowledge, no studies of two-photon absorption properties of corroles were published so far.…”