Ion Pairing of Cationic and Anionic Ir(III) Photosensitizers for Photocatalytic CO₂ Reduction at Lipid–Membrane Surfaces

Abstract

We synthesized an ion pair comprising cationic and anionic Ir­(III) photosensitizers ([Ir1 +]­[Ir2 –]) for photocatalytic CO2 reduction and showed that the cationic component imparts stability, while the cyclometalating ligands in the anionic component ensure effective visible-light absorption. The triplet excited state of [Ir1 +] is the key photoredox species in this system and is mainly generated through the transfer of triplet excitation energy from the anionic moiety due to Coulombic interactions and appropriate triplet energy alignment between the two ionic components. The positive photosensitization effect of ion pairing was demonstrated by photocatalytic CO2 reduction in cooperation with a Re­(I) molecular catalyst incorporated into a vesicle membrane.

π-Electronic ion pairs: building blocks for supramolecular nanoarchitectonics viaiπ–iπ interactions

“…The resulting radical pairs, especially under photoirradiation, can serve as catalysts, with cation- and anion-derived radicals acting as reducing and oxidizing species, respectively. 101 Furthermore, columnar structures comprising identically charged species offer potential applications in efficient semiconductive materials. The electrostatic repulsion between identically charged species can be overcome by dispersion forces originating from π-electronic systems and dipole–dipole interactions in polarized charged species.…”

Bioinspired photocatalytic systems towards compartmentalized artificial photosynthesis

“…The key of this system is the transference of triplet excitation energy from [Ir 2 - ] to [Ir 1 + ] due to Coulombic interactions to generate the triplet excited state of [Ir 1 + ], which then reduces Re(dtb)(CO) 3 Cl to form the active catalytic species 137 . Finally, more complex compartmentalized systems have been reported for CO 2 conversion, including enzymes and full biologic metabolic pathways into artificial vesicles 136 , 138 , 139 .…”

Ion Pairing Enables Targeted Prodrug Activation via Red Light Photocatalysis: A Proof-of-Concept Study with Anticancer Gold Complexes

“…In the literature, it is known that electrostatic interaction is critical in determining the conformation, dynamics, and function of biomolecules . In the meantime, in photoredox catalysis, the counterions could significantly influence the charge distribution of cationic photocatalysts giving divergent photoreactivities. − Therefore, we conceived that the ion-pair strategy consisting of charged prodrugs and a long-wavelength-absorbing photosensitizer may boost the phototherapeutic efficacy [Scheme B­(ii)]. In view that reactive gold complexes are strong thiol-enzyme inhibitors − with promising anticancer potential to overcome cisplatin resistance − and its bioactivities can be effectively tuned by ligand modification for prodrug development, − we started to employ the gold-based metallodrug as a proof-of-concept study to demonstrate the power of ion pairing in photocatalytic prodrug activation.…”