Improving the Photoinduced Charge Separation Parameters in Corrole–Perylene Carboximide Dyads by Tuning the Redox and Spectroscopic Properties of the Components

Abstract

A couple of corrole-perylene carboximide dyads (C2-PIa and C2-PIx) have been synthesized and their photoreactivity has been evaluated. We aimed at obtaining better performances for photoinduced charge separation, both in terms of efficiency and in terms of lifetime, with respect to formerly studied systems. The energy level of the charge-separated state was tuned by selecting perylene and corrole components with diverse redox and spectroscopic properties. High spectroscopic energy levels of the perylene carboximide derivatives (PIs) allow a fast charge separation to be maintained in competition with an energy-transfer process from the PI to the corrole unit. Yields and lifetimes of charge separation in toluene are, respectively, 75% and 2.5 μs for C2-PIa and 65% and 24 ns for C2-PIx. The results and the effect of solvent polarity are discussed in the framework of current energy- and electron-transfer theories.

Photoinduced Electron Transfer in an Amine–Corrole–Perylene Bisimide Assembly: Charge Separation over Terminal Components Favoured by Solvent Polarity

“…The CS lifetime values are not impressive for a triad displaying two‐step electron transfer, and certainly much longer lifetimes have been reported in the literature for other triads,11 and even for corrole‐based dyads 8c. g, 9 However, we have been successful in showing that the design of such a triad can indeed lead to an improvement in the CS lifetime with respect to the corresponding dyad. Most importantly, we have shown that solvent polarity can play an important role in stabilising the vicinal and distal CS states to a different extent, favouring a charge shift over the terminal units.…”

“…Energy transfer, and in many cases also electron transfer, leading to charge‐separated (CS) states with high efficiency and long lifetimes have been observed in corrole‐containing arrays 8. Recently, we have been able to improve the performance of a dyad based on corrole and perylene bisimides (PIs)8g by replacing PI with recently synthesised perylene imides with a different substitution pattern 9. The new PIs maintain the characteristics of this class of dyes (high extinction coefficients, ease of reduction, well‐characterised anion radical spectra, and strong luminescence), but display differences in their spectroscopic properties and, to some extent, their electrochemical properties 10.…”

Functional Arrays for Light Energy Capture and Charge Separation

“…The use of a more polar solvent (i.e., benzonitrile) makes the recombination to the ground state less inverted, and therefore faster, by stabilizing the CS state. The CS lifetimes in the more polar solvent are more than two orders of magnitude shorter than in toluene: 140 ps for C2‐PIx and 44 ns for C2‐PIa 58…”

“…Hence, we examined which corrole and which aromatic imide could be used in order to change such parameters. In Figure are reported dyads containing C2 , a differently substituted free‐base corrole easier to oxidize than the former C3 and a couple of “angular” perylene imides, characterized by a higher HOMO–LUMO gap than the former perylene bisimide and less prone to reduction 58. In particular, the PIa component has a reduction potential of ca.…”

Photoinduced processes in a dyad made of a linear and an angular perylene bisimide

“…9 PIa has also been used as an electron donor in a dyad comprising corrole and has provided a charge separated state lifetime of several microseconds, an impressive result if one considers the simple structure of the array and the close proximity of the reactants. 10 The reason for such behaviour has to be ascribed to a quite high driving force, of the order of 2 eV, together with a very small rearrangement of the molecular structure from the charge separated state to the ground state. This results in a reaction with the ΔG 0 largely exceeding the reorganizational energy and as such falling in the "inverted" region and, according to Marcus theory, in a slow recombination reaction.…”