Quenching of Singlet Oxygen by Carotenoids via Ultrafast Superexchange Dynamics
journal contributionposted on 12.06.2020, 13:04 by Hiroyuki Tamura, Hiroshi Ishikita
We analyze the quenching mechanism of singlet molecular oxygen (1O2) by carotenoids, namely lycopene, β-carotene, astaxanthin, and lutein, by means of quantum dynamics calculations and ab initio calculations. The singlet carotenoid (1Car) and 1O2 molecules can form a weakly bound complex via donation of electron density from the highest occupied molecular orbital (HOMO) of the carotenoid to the πg* orbitals of 1O2. The Dexter-type superexchange via charge transfer states (Car•+/O2•–) governs the 1O2 quenching. The Car•+/O2•– states are substantially higher in energy (2–4 eV) than the initial 1Car/1O2 states. The quantum dynamics calculations indicate an ultrafast 1O2 quenching on a timescale of subpicosecond owing to the strong electronic couplings in the carotenoid/O2 complexes. The superexchange mechanism via the Car•+/O2•– states dominates the 1O2 quenching, although the direct two-electron coupling can also play a certain role.
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singlet carotenoidquantum dynamics calculationsHOMODexter-type superexchangeultrafast 1 O 2 quenchingUltrafast Superexchange Dynamicselectron densitySinglet Oxygenβ- carotenecharge transfer statesπ gab initio calculations1 Car1 O 2 quenching1 O 21 O 2 moleculesquenching mechanismsuperexchange mechanism