D. Corinti ; A. Maccelli ; B. Chiavarino ; P. Maitre ; D. Scuderi ; E. Bodo ; S. Fornarini ; M-E. Crestoni
J. Chem. Phys. 150 (16) 165101 (2019). DOI

Travail réalisé sur le site de l’Université Paris Sud.

Abstract

Curcumin (Cur) is a natural polyphenol with a wide spectrum of biological activities and appealing therapeutic potential. Herein, it has been delivered by electrospray ionization as gaseous protonated species, [Cur + H](+), and as a Cu(a) complex, [Cu(Cur- F)](+), a promising antioxidant and radical scavenger. The gas phase structures were assayed by infrared multiple photon dissociation (IRMPD) spectroscopy in both the fingerprint (800-2000 cm(-1)) and hydrogen stretching (3100-3750 cm(-1)) ranges. Comparison between the experimental features and linear IR spectra of the lowest energy structures computed at the B3LYP/6-311+G(d,p) level reveals that bare [Cu(Cur - H](+) exists in a fully planar and symmetric arrangement, where the metal interacts with the two oxygens of the syn-enolate functionality of deprotonated Cur and both OCH3 groups are engaged in H-bonding with the ortho OH. The effect of protonation on the energetic and geometric determinants of Cur has been explored as well, revealing that bare [Cur + NI’. may exist as a mixture of two close-lying isomers associated with the most stable binding motifs. The additional proton is bound to either the diketo or the keto-enol configuration of Cur, in a bent or nearly planar arrangement, respectively.