Abstract
The physicochemical and antioxidant properties of seven carotenoids: antheraxanthin, β-carotene, neoxanthin, peridinin, violaxanthin, xanthrophyll and zeaxanthin were studied by theoretical means. Then the Optoelectronic properties and interaction of chlorophyll-carotenoid complexes are analysed by TDDFT and IGMPLOT. Global reactivity descriptors for carotenoids and chlorophyll (Chla, Chlb) are calculated via conceptual density functional theory (CDFT). The higher HOMO–LUMO (HL) gap indicated structural stability of carotenoid, chlorophyll and chlorophyll-carotenoid complexes. The chemical hardness for carotenoids and Chlorophyll is found to be lower in the solvent medium than in the gas phase. Results showed that carotenoids can be used as good reactive nucleophile due to lower µ and ω. As proton affinities (PAs) are much lower than the bond dissociation enthalpies (BDEs), it is anticipated that direct antioxidant activity in these carotenoids is mainly due to the sequential proton loss electron transfer (SPLET) mechanism with dominant solvent effects. Also lower PAs of carotenoid suggest that antioxidant activity by the SPLET mechanism should be a result of a balance between proclivities to transfer protons. Reaction rate constant with Transition-State Theory (TST) were estimated for carotenoid-Chlorophyll complexes in gas phase. Time dependent Density Functional Theory (TDDFT) showed that all the chlorophyll (Chla, Chlb)–carotenoid complexes show absorption wavelength in the visible region. The lower S1–T1 adiabatic energy gap indicated ISC transition from S1 to T1 state.
Highlights
The physicochemical and antioxidant properties of seven carotenoids: antheraxanthin, β-carotene, neoxanthin, peridinin, violaxanthin, xanthrophyll and zeaxanthin were studied by theoretical means
As Magnesium is present in Chlorophyll, Chla and Chlb are optimized with CAM-B3LYP/Lanl2dz27:6-31G**, wB97xD/Lanl2dz:6-31G** and M062x/Lanl2dz:6-31G** methods with G16 software programme in gas phase
The reactivity of seven carotenoids is studied by DFT-based global reactivity descriptors using Chemical reactivity theory (CRT)
Summary
The physicochemical and antioxidant properties of seven carotenoids: antheraxanthin, β-carotene, neoxanthin, peridinin, violaxanthin, xanthrophyll and zeaxanthin were studied by theoretical means. Chlorophyll and carotenoid pigments can be used as important optical molecular probes to observe different phases of plant performances and its development[1]. The synthesized plant carotenoids accumulate exclusively in plastids, and most importantly, chloroplast and chromoplast[2] Carotene and xanthophylls, both the oxygenated derivatives of carotenes are health promoters and have ability to quench singlet oxygen and scavenge toxic free radicals preventing or reducing damage to living cells. The physicochemical and antioxidant properties of seven carotenoids: antheraxanthin (a), β-carotene (b), neoxanthin (n), peridinin (p), violaxanthin (v), xanthrophyll (x) and zeaxanthin (z) are studied by DFT method. The optoelectronic properties and interaction of these seven carotenoids were studied with chlorophyll Chla, Chlb. The absorption properties for carotenoid, chlorophyll and chlorophyllcarotenoid have been studied by TDDFT method in water
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