Development of Visible-light-responsive Organic Photochromic Systems in Aqueous Media

Maity, Manik Lal (2026) Development of Visible-light-responsive Organic Photochromic Systems in Aqueous Media. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Manik Lal Maity (20RS053)) 20RS053.pdf - Submitted Version Restricted to Repository staff only Download (24MB)

Abstract

The thesis primarily aims to address two fundamental problems associated with the operation of organic photoswitches in aqueous media: poor-aqueous compatibility and frequent reliance on ultraviolet (UV) light for activation. Although many established photoswitches display excellent performance in organic solvents, their use in aqueous environments is often limited by low solubility, aggregation, and rapid degradation. Moreover, most of the conventional photoswitches are activated by UV light in at least one of the bidirectional switching and thus imposes additional drawbacks, including limited penetration depth, phototoxicity, and reduced applicability in biologically relevant systems. Overcoming both these aforementioned constraints is essential for advancing photochromic systems toward biological applications. The introductory chapter, Chapter 1 deals with the principles and the recent developments of the ionic photoswitches in aqueous media. It also addresses the potential challenges associated with the design strategies and practical limitations of these systems, as well as guidelines for improved photoswitching performance. Chapter 2 demonstrates the development of novel dimethyldihydropyrene phosphonium salts, an alternative approach for all-visible bidirectional efficient switching in fully aqueous media. Chapter 3 deals with a fundamental concept of a solvent- and component-dependent all-photonic orthogonal switching mechanism in a mixture of the same class of photoswitches. An in-depth analysis of solvent- and component-dependent entropy-enthalpy synergy for the thermal reversal process is thoroughly investigated. Chapter 4 demonstrates with the different singlet oxygen reactivity with the dimethyldihydropyrene phosphine system, which is not observed for traditional C-C linked dimethyldihydropyrene system, unlocking additional storage of singlet oxygen for C-P linked dimethyldihydropyrene. Chapter 5 reveals the development of visible-light-switchable chalcone-flavylium photochromic systems in water, achieved by preferentially irradiating at the tail end of the absorption spectra in a mild approach.

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