Facile method for spectroscopic examination of radical ions of hydrophilic carotenoids.
Hydrophilic carotenoids, unusual members of an intrinsically hydrophobic family, and their radical ions are important reactants. An all-optical method for generating singly charged radical ions of a hydrophilic carotenoid (Car) is described. It relies on photolyzing an aqueous mixture of Car and a photoionizable auxiliary solute (A), and making conditions conducive to the capture, by Car, of the hydrated electron (e(aq)(-)) or the positive hole in A(*)(+) or both. When A is Trolox (TOH), only e(aq)(-) can be captured, since TOH (*)(+) deprotonates too rapidly to be a hole donor; when A is Trolox methyl ether (TOMe), both Car(*)(-) and Car(*)(+) are formed, since TOMe (+) lives long enough to transfer its positive hole to Car; formation of Car(*)(-) is prevented under aerobic conditions.
Naqvi
K Razi
KR
Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491, Trondheim, Norway. razi.naqvi@ntnu.no
Melø
Thor Bernt
TB
Jávorfi
Tamás
T
González-Pérez
Sergio
S
Arellano
Juan B
JB
D000097:Acetonitriles / Q000737:chemistry; D000838:Anions; D002338:Carotenoids / Q000737:chemistry*; D002627:Chemistry, Physical / Q000379:methods; D004563:Electrochemistry / Q000379:methods; D004583:Electrons; D005609:Free Radicals; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D007477:Ions; D008027:Light; D010777:Photochemistry / Q000379:methods*; D011522:Protons; D012997:Solvents / Q000737:chemistry; D013053:Spectrophotometry / Q000379:methods*
D000097:Acetonitriles; D000838:Anions; D005609:Free Radicals; D007477:Ions; D011522:Protons; D012997:Solvents; D002338:Carotenoids; C032159:acetonitrile