Intramolecular charge-transfer state of carotenoids siphonaxanthin and siphonein: function of non-conjugated acyl-oxy group.

摘要: We used ultrafast transient absorption spectroscopy to study excited-state dynamics of two keto-carotenoids, siphonaxanthin and siphonein. These carotenoids differ in the presence dodecanoyl-oxy group siphonein, which is attached C19 carbon on same side molecule as conjugated keto group. show that this group, though not conjugation, still capable modifying excited state properties. While spectroscopic properties siphonein are nearly identical a non-polar solvent, they become markedly different polar solvents. In having moiety, exhibits less pronounced vibrational bands spectrum has significantly enhanced characteristic features an intramolecular charge-transfer (ICT) spectra compared siphonaxanthin. The moiety also alters lifetimes S1/ICT state. For siphonaxanthin, 60, 20, 14 ps n-hexane, acetonitrile, methanol, whereas for these yield 11, 10 ps. Thus, we even non-conjugated functional can affect character By comparison with fucoxanthin acyl-oxy derivatives, position respect key feature determining whether polarity-dependent behavior or suppressed.