Paras WANJARI
defended his PhD thesis
on 9 december 2025
Self-assembled proton, ion and water channels with photo regulated transmembrane transport properties
In front of the jury:
– M. Mihail BARBOIU, Directeur de Recherche, CNRS, IEM – Directeur de thèse
– Mme. Hennie VALKENIER, Research Associate, FNRS, University libre de Bruxelles – Rapporteur
– M. Guillaume VIVES, Maître de Conférences HDR, CNRS, Sorbonne Université – Rapporteur
– M. Sébastien ULRICH, Charge de Recherche, CNRS, IBMM – Examinateur
– Mme. Niculina HADADE, Professeur, Babes-Bolyai University – Examinateur
Abstract:
Proton and water transport across biological membranes are fundamental to cellular homeostasis, energy conversion, and signal regulation. Inspired by natural systems such as aquaporins and proton channels, this thesis presents the design and development of synthetic, photoresponsive supramolecular channels capable of selectively transporting protons and water. While significant progress has been made in light-gated ion transport, photo-controlled proton and water conduction remain largely unexplored. Addressing this gap, this work integrates photoswitchable molecular units with proton-conducting imidazole architectures to achieve tunable, light-controlled transmembrane transport. Three molecular systems are developed, each employing a distinct strategy for achieving selective and reversible transport.
Chapter 2 introduces acylhydrazone–imidazole channels that modulate proton and water transport via reversible E–Z photoisomerization. Three derivatives (C4, C8, C12) self-assemble into hydrogen-bonded architectures forming selective, light-gated pathways. Structural and spectroscopic analyses confirm efficient photoswitching, while functional assays demonstrate high proton selectivity, complete ion exclusion, and tunable transport. Molecular simulations reveal that supramolecular water clusters, stabilized by acylhydrazone–imidazole interactions, facilitate coupled proton–water relay. Notably, the Z isomer exhibits enhanced transport relative to the E form, attributed to its greater structural flexibility and dynamic behaviour.
Chapter 3 expands this approach using a bis(imidazole-amide)-tetrafluoro-azobenzene framework, where photoinduced E–Z conversion of azobenzene enables reversible modulation of transport. The system supports efficient and selective proton and water conduction while excluding alkali cations and anions, establishing precise light-driven control. The Z isomer consistently shows superior activity, demonstrating the adaptability of azobenzene photoswitches in governing transmembrane function.
Chapter 4 examines semicarbazone-based imidazole derivatives designed to mimic I-quartet-like assemblies. Two families—imidazole-2-yl and imidazole-4-yl semicarbazones—were synthesized to investigate how subtle structural changes affect ion selectivity and transport behaviour. The imidazole-2-yl derivatives exhibit strong chloride binding and transport in their Z form, while the E isomers remain inactive. Conversely, the imidazole-4-yl analogues favor selective proton and water transport, with the E form outperforming the Z configuration. These results highlight how minor variations in molecular geometry and hydrogen-bond orientation can drastically influence transport efficiency and selectivity.
Overall, this thesis establishes a coherent molecular design strategy for photo-regulated proton and water transport in synthetic channels. By combining hydrogen-bonding motifs, proton-conducting imidazole units, and photoswitchable linkers, it introduces the first tunable systems that merge structural responsiveness with functional selectivity in proton and water transport. The insights gained advance the understanding of supramolecular channel design and lay the groundwork for stimuli-responsive materials with potential applications in biomimetic membranes, artificial photosystems, and controlled ion transport in living systems.
