Date of Award
Summer 6-13-2025
Document Type
Thesis (Ph.D.)
Department or Program
Chemistry
First Advisor
Ivan Aprahamian
Abstract
Photochromic materials have drawn increasing interest for their ability to control functional systems and biological processes using light. Molecular switches enable precise, reversible regulation of the systems in which they are embedded. To achieve robust and versatile switching, careful tuning of molecular structure and activation conditions is essential. Hydrazones represent a promising class of photoswitches, offering synthetic accessibility, strong thermal and photochemical stability, and a modular framework that supports further development for materials and biological applications. This work begins by examining a family of heterocyclic hydrazones to determine how structural variations affect photoswitching efficiency and thermal half-lives. Comparisons with phenyl-based analogues help identify second-generation switches with enhanced bistability. These findings establish general design principles for improving the performance of hydrazone-based molecular switches. Next, the focus shifts to triazole-containing hydrazones, taking advantage of the triazole’s prominence in click chemistry. By varying the linkage pattern between the triazole and hydrazone core (1,4 vs. 1,5), the impact of steric and electronic effects on switching behavior is revealed. This part of the study introduces the first hydrazone photoswitch featuring a zero-length linker between electron-donating and -withdrawing groups, enabling a compact and highly modular design for integration into functional materials. The third section targets vibrational sensing applications by designing alkynefunctionalized hydrazones for Raman spectroscopy. Upon light-induced isomerization, these switches exhibit distinct and controllable shifts in alkyne stretching frequencies. Through structural refinement, a subclass of candidates is developed for use in optical data storage and Raman-based imaging platforms. Finally, this thesis explores the use of mechanical force as a stimulus for E/Z isomerization around the hydrazone C=N bond. Building on a fluorescent scaffold, new mechanophores are created to support reversible, dual-mode switching triggered by either light or mechanical input. These systems offer a pathway toward responsive materials capable of sensing and reporting mechanical stress in real time.
Recommended Citation
Sosnin, Daniil, "Advancing The Functional Diversity of Hydrazone Photoswithces" (2025). Dartmouth College Ph.D Dissertations. 368.
https://digitalcommons.dartmouth.edu/dissertations/368
