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A Soft On/Off Switch Based on the Electrochemically Reversible H-J Interconversion of a Floating Porphyrin Membrane

preprint
submitted on 06.04.2021, 23:21 and posted on 07.04.2021, 13:13 by Andrés F. Molina-Osorio, Sho Yamamoto, Alonso Gamero-Quijano, Hirohisa Nagatani, Micheal D. Scanlon

Soft molecular assemblies that respond reversibly to external stimuli are attractive materials as on/off switches, in optoelectronic, memory and sensor technologies. In this article, we present the reversible structural rearrangement of a soft porphyrin membrane under an electrical potential stimulus in the absence of solid-state architectures. The free-floating porphyrin membrane lies at the interface between immiscible aqueous and organic electrolyte solutions and is formed through interfacial self-assembly of zinc(II) meso-tetrakis(4-carboxyphenyl)porphyrins (ZnPor). A potential difference between the two immiscible electrolyte solutions induces the intercalation of bis(triphenylphosphoranylidene)ammonium cations from the organic electrolyte that exchange with protons in the porphyrin membrane. In situ UV/vis absorbance spectroscopy shows that this ionic intercalation and exchange induces a structural interconversion of the individual porphyrin molecules in the membrane from an H- to a J-type molecular configuration. These structural rearrangements are reversible over 30 potential cycles. In situ polarisation-modulation fluorescence spectroscopy further provides clear evidence of structural interconversion of the porphyrin membrane, as intercalation of the organic electrolyte cations significantly affects the latter’s emissive properties. By adjusting the pH of the aqueous phase, additional control of the electrochemically reversible structural interconversion can be achieved, with total suppression at pH 3.

Funding

Science Foundation Ireland (SFI) under Grant no. 13/SIRG/2137

European Research Council through a Starting Grant (Agreement no. 716792)

Irish Research Council Government of Ireland Postdoctoral Fellowship Award (Grant Number GOIPD/2018/252)

Grant-in-Aid for Scientific Research (C) (No.19K05541) from Japan Society for the Promotion of Science (JSPS)

JSPS Research Fellowship for Young Scientists (No.17J02009)

History

Email Address of Submitting Author

micheal.scanlon@ul.ie

Institution

University of Limerick

Country

Ireland

ORCID For Submitting Author

0000-0001-7951-7085

Declaration of Conflict of Interest

The authors declare that there is no conflict of interest.

Version Notes

This manuscript has been submitted to a journal for publications and is under review.

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