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Thienylene-Based Diradicaloids: Electrochromic Ring-Closing of Dithienylethene-Based Bis-Amidinium Cation
Priyanka Saha1, Nicolas Chrysochos1, Benedict J Elvers2
1Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad, 500046, India.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|November 11, 2025
Summary
Thiophene diradicaloids with varying π-conjugated spacers show distinct triplet populations. A novel dithienylethene derivative enables electrochromic ring-closing, offering a light-alternative stimulus for photochromic systems.
Area of Science:
- Organic Chemistry
- Materials Science
- Photochemistry
Background:
- Thiophene's lower aromaticity favors quinoid forms in diradicaloids.
- Thiophene's reactivity enables photochromism in dithienylethene derivatives.
Purpose of the Study:
- Synthesize crystalline thiophene-based diradicaloids with varying π-conjugated spacers.
- Investigate the influence of π-conjugation on triplet population.
- Develop an electrochromic system for dithienylethene derivatives.
Main Methods:
- Modular synthesis of thienylene-, bithienylene-, and terthienylene-based diradicaloids.
- Electron Paramagnetic Resonance (EPR) spectroscopy to assess triplet states.
- Electrochemical reduction and oxidation studies.
Main Results:
- Diradicaloids with thienylene and bithienylene spacers are EPR inactive.
- Terthienylene-bridged diradicaloids show temperature-dependent EPR signals.
- A dithienylethene-based bis-amidinium cation undergoes electrochromic ring-closing to a diradicaloid.
Conclusions:
- π-conjugated spacers significantly influence triplet state populations in thiophene diradicaloids.
- Electrochromic switching provides an alternative to UV light for dithienylethene photochromism.
- Structurally characterized electrochromic behavior demonstrated for a novel dithienylethene system.
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