Triplet State Energy of the Carotenoid Bixin Determined by Photoacoustic Calorimetry

A. DE O. RIOS; A.Z. MERCADANTE; C.D. BORSARELLI

DYES AND PIGMENTS

Elsevier

Lugar: Amsterdam; Año: 2007 vol. 74 p. 561 - 565

0143-7208

The triplet state energy level of the natural cis carotenoid bixin (methyl hydrogen 9’Z-6, 6’-diapocarotene-6,6’-dioate) was determined using laser-induced photoacoustic calorimetry (PAC) in acetonitrile/methanol (1:1) solution. An energy-transfer process with anthracene as sensitizer in O2-saturated solution was used to populate the carotenoid triplet state. The energy balance of the system allowed the calculation of the triplet energy content of bixin as ET = 18  2 kcal/mol. The result is discussed in relation with both its singlet molecular oxygen quenching and cis  trans isomerization abilities. The quantum yield,  = 0.69, for the formation either of the triplet state or the singlet molecular oxygen by the sensitizer anthracene was also determined.