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Updated: Jul 1, 2025

Determination of the Photoisomerization Quantum Yield of a Hydrazone Photoswitch

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Published on: February 7, 2022

1,2-BF₂ Shift and Photoisomerization Induced Multichromatic Response.

Qingkai Qi¹, Shiqing Huang², Xiaogang Liu²

¹Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States.

Journal of the American Chemical Society

|March 1, 2024

Summary

Researchers developed adaptive materials that change color with heat or light. A novel thermal shift transforms a photoswitch into a fluorophore, enabling multicolor modulation in smart surfaces and anticounterfeit devices.

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Area of Science:

Materials Science
Organic Chemistry
Photochemistry

Background:

Adaptive materials with multichromatic responses are valuable for applications like smart surfaces and anticounterfeit technologies.
Azo-based photoswitches offer tunable optical properties but often require specific activation methods.

Purpose of the Study:

To report a novel thermal 1,2-BF2 shift enabling a visible-light-activated azo-BF2 photoswitch to transform into a BF2-hydrazone fluorophore (BODIHY).
To investigate the mechanism and conditions for this transformation in solution and solid-state.
To demonstrate multicolor modulation using this system in a cross-linked polymer film.

Main Methods:

Synthesis and characterization of azo-BF2 compounds.
Spectroscopic analysis (UV-Vis, fluorescence) to monitor transformations.
Density Functional Theory (DFT) calculations to elucidate reaction mechanisms and energy barriers.
Fabrication and testing of cross-linked polydimethylsiloxane films incorporating the photoswitch system.

Main Results:

A thermal 1,2-BF2 shift was observed, converting azo-BF2 photoswitches to BODIHY fluorophores.
The shift is catalyzed by proximate oxygen and driven by electronic effects, not steric ones.
Theoretical calculations revealed accessible energy barriers for the trans → BODIHY transformation at room temperature.
Multicolor modulation was achieved in polymer films using light and heat stimuli.

Conclusions:

The discovered reaction cascade offers a sophisticated yet simple system for creating adaptive, color-changing materials.
This work expands the utility of azo-BF2 compounds for advanced optical applications.
The findings pave the way for new smart surfaces and anticounterfeit strategies.