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Photochemical Electrocyclic Reactions: Stereochemistry

Photochemical Electrocyclic Reactions: Stereochemistry

The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation

Thermal and Photochemical Electrocyclic Reactions: Overview

Thermal and Photochemical Electrocyclic Reactions: Overview

Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.

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Updated: Jan 9, 2026

Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties

Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties

Published on: January 8, 2016

Stimuli-Responsive Photoacid Polyelectrolytes.

Carlo Gericke¹, Edmondo M Benetti¹, Barbara Fresch²

¹Laboratory for Macromolecular and Organic Chemistry, Department of Chemical Sciences, University of Padova, via Marzolo 1, Padova, 35131, Italy.

Angewandte Chemie (International Ed. in English)

|December 10, 2025

Summary

This summary is machine-generated.

Spiropyran polymers show light-induced pH changes in water. Their composition controls photoacidity, enabling robust light-to-protonic energy conversion devices.

Keywords:

Merocyanine photoacids Molecular switches Photoacidity Polyelectrolytes Spiropyrans

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Last Updated: Jan 9, 2026

Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties

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Published on: January 8, 2016

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Preparation of Light-responsive Membranes by a Combined Surface Grafting and Postmodification Process

Preparation of Light-responsive Membranes by a Combined Surface Grafting and Postmodification Process

Published on: March 21, 2014

Area of Science:

Polymer Chemistry
Photochemistry
Materials Science

Background:

Spiropyran polymers exhibit diverse stimuli-responsive behaviors.
Photoacid characteristics of spiropyran polymers in aqueous media are underexplored.

Purpose of the Study:

To synthesize and investigate spiropyran-containing polyelectrolyte copolymers.
To understand the photoacidic properties and hydrolytic stability of these copolymers in water.

Main Methods:

Synthesis of poly(3-sulfopropyl methacrylate) copolymers with spiropyran units.
Characterization of copolymer behavior in aqueous solutions.
Investigation of light-induced proton dissociation and pH fluctuations.

Main Results:

Polymer constitution enhances the hydrolytic stability of protonated merocyanine units.
Polymer composition allows programming of photoacidity.
Light exposure induces reversible proton dissociation, causing pH fluctuations up to 3 units.

Conclusions:

Spiropyran copolymers offer tunable photoacidity in aqueous environments.
These materials demonstrate potential for light-to-protonic energy conversion applications.