Elementary processes triggered in curcumin molecule by gas-phase resonance electron attachment and by photoexcitation in solution.

This article focuses on the investigation of electron- and photon-induced elementary processes in curcumin (CUR), a naturally occurring polyphenolic pigment known for its antioxidant and photodynamic properties. Using dissociative electron attachment (DEA) spectroscopy under gas-phase conditions and chemically induced dynamic nuclear polarization (CIDNP) in solution, the study characterizes the formation and stability of CUR molecular negative ions and radical species, primarily in its enol tautomeric form. Density functional theory (DFT) calculations support the experimental findings, estimating the adiabatic electron affinity of CUR to be about 1 eV and elucidating the energetics of fragmentation and electron attachment to specific π* molecular orbitals. The results reveal that proton-coupled electron transfer between CUR molecules occurs under UV irradiation, contributing to the understanding of CUR's molecular mechanisms relevant to its biological activities and phototherapeutic applications.