Photoelectrochemistry and Reversible H-J Interconversion of Porphyrin Nanostructures at an Electrified Soft Interface

NaMeS students are invited to IPC PAS Seminar within Dream Chemistry Lecture Series delivered by:

 

Prof. Micheál D. Scanlon

The Bernal Institute and Department of Chemical Sciences,

School of Natural Sciences, University of Limerick, Ireland

Thursday, 21st November, 2019, 10.00

 

Assembly hall of the IPC PAS

Abstract

Certain soft interfaces formed between aqueous and organic electrolyte solutions of low miscibility (e.g., trifluorotoluene) are electrochemically active in the sense that it is possible to precisely control the Galvani potential difference between the two adjacent liquids (i.e., to “polarise” or electrify the interface), and thus drive charge transfer reactions. Such interfaces are denoted interfaces between two immiscible electrolyte solutions (ITIES). The ITIES can be controllably electrified by application of a potential either externally through the use of electrodes immersed in both phases or through a common ion dissolved in the organic and aqueous phases.

Synthetic molecular assemblies at soft interfaces exhibit macroscale long-range order and so provide routes to biomimetic analogues that minimise concentration quenching. In this presentation, I will describe a new route to the facile assembly of free-standing layered crystalline films of zinc(II) meso-tetrakis(4-carboxyphenyl)porphyrin interfacial nanostructures. I will demonstrate the reversible structural rearrangement of these porphyrin supramolecular structures floating at the liquid-liquid interface from a H- to J-type configuration upon varying the interfacial Galvani potential difference. The latter structural changes were observed in situ by UV/vis and potential modulated fluorescence spectroscopies (both under total internal reflection at the electrified soft interface).

The porphyrin interfacial nanostructures exhibit significant photocurrents in situ at an electrified liquid | liquid interface, providing a new paradigm for realisation of light-harvesting antennae in artificial photosynthetic technologies. To explore this possibility, photo-induced electron transfer between organic electron donors, like ferrocene derivatives, and aqueous electron acceptors, like O₂, is achieved by controllably modulating the voltage across the interface.