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Bressan, Giovanni 
ORCID: https://orcid.org/0000-0001-7801-8495, Siddiqui, Khalid, Ashworth, Eleanor K., Chakraborty, Pratip ORCID: https://orcid.org/0000-0002-0248-6193, Banerjee, Dipanjan, Braun, Erico M., Meech, Stephen R. ORCID: https://orcid.org/0000-0001-5561-2782 and Bull, James N. ORCID: https://orcid.org/0000-0003-0953-1716
(2026)
Photomolecular rotor dynamics of the oxindole-based photoprotective bacterial pigment violacein.
Physical Chemistry Chemical Physics, 28 (2).
pp. 1260-1268.
ISSN 1463-9076
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Abstract
Conjugated molecules incorporating the oxindole motif offer a versatile scaffold for designing highperformance, light-responsive materials that exploit photomolecular rotor motion. Violacein, a purple coloured oxindole-based pigment produced by bacterial strains in superglacial Antarctic ice melts, serves as a natural photoprotectant. Using ultrafast spectroscopy combined with explicitlysolvated potential energy surfaces, we characterise the excited-state relaxation mechanism in violacein to involve initial relaxation to planar locally excited (LE) state(s), followed by passage through a twisted charge-transfer (CT) state along the molecular rotor coordinate to a nearby isomerising-like conical intersection seam. Propagation over the excited-state barrier connecting the LE and CT states along the photomolecular rotor axis leads to a strong viscosity dependence of the excited state lifetimes (ca. 4 ps in acetonitrile and 100 ps in ethylene glycol). These dynamics, leading to efficient electronic-to-vibrational energy conversion, coupled with a fast rate for thermal conversion of the possible Z photoisomer back to the starting E isomer, confer violacein with desirable photoprotectant properties.
| Item Type: | Article |
|---|---|
| Additional Information: | Data availability: The data that support the findings of this study are available from the corresponding author upon reasonable request. Funding information: This work was funded by an EPSRC New Investigator Award (EP/W018691 to JNB) and an EPSRC Grant (EP/X011410/1 to SRM). GB is grateful to the Leverhulme Trust for funding him through an Early Career Fellowship (Grant no. ECF2023-195). EMB thanks the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for his studentship (SWE 200581/2025-2). |
| Faculty \ School: | Faculty of Science > School of Chemistry, Pharmacy and Pharmacology |
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| Depositing User: | LivePure Connector |
| Date Deposited: | 16 Dec 2025 15:30 |
| Last Modified: | 18 Jun 2026 20:49 |
| URI: | https://ueaeprints.uea.ac.uk/id/eprint/101428 |
| DOI: | 10.1039/D5CP04151A |
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