Photophysics and Electrochemistry of Biomimetic Pyranoflavyliums: What Can Bioinspiration from Red Wines Offer?

Eli Misael Espinoza,Frank Herbert Quina,Valentine Ivanov Vullev,Gustavo Thalmer De Medeiros Silva,Mimi Karen Billones,John Anthony Clark,Cassio Pacheco Da Silva

doi:10.3390/photochem2010003

Abstract

Natural dyes and pigments offer incomparable diversity of structures and functionalities, making them an excellent source of inspiration for the design and development of synthetic chromophores with a myriad of emerging properties. Formed during maturation of red wines, pyranoanthocyanins are electron-deficient cationic pyranoflavylium dyes with broad absorption in the visible spectral region and pronounced chemical and photostability. Herein, we survey the optical and electrochemical properties of synthetic pyranoflavylium dyes functionalized with different electron-donating and electron-withdrawing groups, which vary their reduction potentials over a range of about 400 mV. Despite their highly electron-deficient cores, the exploration of pyranoflavyliums as photosensitizers has been limited to the “classical” n-type dye-sensitized solar cells (DSSCs) where they act as electron donors. In light of their electrochemical and spectroscopic properties, however, these biomimetic synthetic dyes should prove to be immensely beneficial as chromophores in p-type DSSCs, where their ability to act as photooxidants, along with their pronounced photostability, can benefit key advances in solar-energy science and engineering.

Highlights

Instituto de Química, Universidade de São Paulo, Avenida Lineu Prestes 748, Cidade Universitaŕia, Department of Biochemistry, University of California, Riverside, CA 92521, USA
Product purity was examined using reverse-phase high-pressure liquid chromatography (HPLC) equipped with a Promosil C-18 column and photodiode-array detector
Values in parentheses are obtained from the bathochromic edge of the optical absorption spectra. f The optical absorption and excitation spectra do not match in their bathochromic regions, the crossing point does not represent the energy between the ground and the lowest singlet excited state

Summary

Introduction

We survey the optical and electrochemical properties of synthetic pyranoflavylium dyes functionalized with different electrondonating and electron-withdrawing groups, which vary their reduction potentials over a range of about 400 mV. Despite their highly electron-deficient cores, the exploration of pyranoflavyliums as photosensitizers has been limited to the “classical” n-type dye-sensitized solar cells (DSSCs) where they act as electron donors. DSSCs, where their ability to act as photooxidants, along with their pronounced photostability, can benefit key advances in solar-energy science and engineering Due to their inherent photostability and a broad variety of optical and electronic properties, naturally occurring plant dyes are an important source of inspiration for structure–.

Methods

Results

Discussion

Conclusion