Singlet oxygen electronic states

Burke M, Edge R, Land EJ, McGarvey DJ, and Truscott TG. 2001. One-electron reduction potentials of dietary carotenoid radical cations in aqueous micellar environments. FEBS Letters 500(3) 132-136. Bystritskaya EV and Karpukhin ON. 1975. Effect of the aggregate state of a medium on the quenching of singlet oxygen. Doklady Akademii Nauk SSSR 221 1100-1103. 

Moreover, carotenoids may quench electronically excited states and scavenge free radicals formed in the retina, and therefore protect biomolecules from oxidative damage. Due to the low energy level of the first excited triplet state ( Car), carotenoids (Car) can act as efficient acceptors of triplet state energy from photosensitizers (S) (Equation 15.1), such as all-tra .s-retinal, the photosensitizers of lipofuscin (Rozanowska et al., 1998), or singlet oxygen C02) (Equation 15.2) (Cantrell et al., 2003) ... 

Singlet oxygen C ) differs from the predominant oxygen molecule in that O2 is in the ground state or triplet state and its outer two unshared electrons have parallel spins (sometimes designated 302), which is nearly unreactive toward other molecules, while singlet oxygen... 

Hindered amines, such as 4-(2,2,6,6-tctramcthylpiperidinyl) decanedioate, serve as radical scavengers and will protect thin films under conditions in which ultraviolet absorbers are ineffective. Metal salts of nickel, such as dibutyldithiocarbamate, are used in polyolefins to quench singlet oxygen or electronically excited states of other species in the polymer. Zinc salts function as peroxide decomposers. 

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