Light-to-heat conversion materials generate great interest due to their widespread applications, notable exemplars being solar energy harvesting and photoprotection. Another more recently identified potential application for such materials is in molecular heaters for agriculture, whose function is to protect crops from extreme cold weather and extend both the growing season and the geographic areas capable of supporting growth, all of which could help reduce food security challenges. To address this demand, a new series of phenolic-based barbituric absorbers of ultraviolet (UV) radiation has been designed and synthesised in a sustainable manner. The photophysics of these molecules has been studied in solution using femtosecond transient electronic and vibrational absorption spectroscopies, allied with computational simulations and their potential toxicity assessed by in silico studies. Following photoexcitation to the lowest singlet excited state, these barbituric absorbers repopulate the electronic ground state with high fidelity on an ultrafast time scale (within a few picoseconds). The energy relaxation pathway includes a twisted intramolecular charge-transfer state as the system evolves out of the Franck–Condon region, internal conversion to the ground electronic state, and subsequent vibrational cooling. These barbituric absorbers display promising light-to-heat conversion capabilities, are predicted to be non-toxic, and demand further study within neighbouring application-based fields.
The authors acknowledge the FET-Open grant BoostCrop (grant agreement 828753), the entire BoostCrop (https://boostcrop.eu/) team for their interest in the work and the Warwick Centre for Ultrafast Spectroscopy (WCUS) for the use of transient vibrational absorption spectroscopy (TVAS) and Fluorolog 3 apparatus. T. T. A. thanks the University of Warwick for a PhD studentship through the Chancellor Scholarship. D. J. L. C. thanks EPSRC and the De Beers Group for a PhD studentship facilitated through the Centre for Doctoral Training in Diamond Science and Technology. M. T. do C., J. M. T., and M. B. thank the Centre de Calcul Intensif d’Aix-Marseille for granting access to its high-performance computing resources. B. R., C. P., M. M. M. and F. A. thank the Agence Nationale de la Recherche (grant number ANR-17-CE07-0046), as well as the Grand Reims, Conseil Départemental de la Marne, and the Grand Est region for nancial support. V. G. S. thanks the Royal Society and Leverhulme Trust for a Royal Society Leverhulme Trust Senior Research Fellowship.
© The Royal Society of Chemistry.