TY - JOUR
T1 - Sensitized Triplet Formation of Chlorophyll-A and beta-Carotene
AU - Jensen, Nina Mejlhede
AU - Wilbrandt, Robert Walter
AU - Pagsberg, Palle Bjørn
PY - 1980
Y1 - 1980
N2 - The naphthalene-sensitized formation of triplet excited chlorophyll-a (Chl-a) and all-transß-carotene has been studied by pulse radiolysis. The rate constants for transfer of triplet energy from naphthalene to Chl-a and all-transß-carotene in benzene at 25°C are (3.6 ± 0.6)·109M-1 s-1 and (10.7 ± 1.2)·109M-1 s-1, respectively. The decays of the excited triplet states of naphthalene, Chl-a and all-transß-carotene all follow a mixed first-and second-order mechanism. The first-order rate constant for triplet decay is strongly dose dependent for naphthalene but only slightly dependent and independent of dose for Chl-a and all-transß-carotene, respectively. The rate constants for triplet-triplet annihilation are (1.4 ± 0.3)·109M-1 s-1 for Chl-a and (3.6 ± 0.4)·109M-1 s-1 for all-transß carotene. The nearly constant ratio k(ß-carotene)/k(Chl-a) for the bimolecular triplet energy transfer rate constants is discussed in terms of the molecular shapes of the two molecules. The energetics of the triplet-triplet annihilation of all-transß-carotene are discussed, and it is proposed that production of the excited 1AB state may be a major route in the annihilation process.
AB - The naphthalene-sensitized formation of triplet excited chlorophyll-a (Chl-a) and all-transß-carotene has been studied by pulse radiolysis. The rate constants for transfer of triplet energy from naphthalene to Chl-a and all-transß-carotene in benzene at 25°C are (3.6 ± 0.6)·109M-1 s-1 and (10.7 ± 1.2)·109M-1 s-1, respectively. The decays of the excited triplet states of naphthalene, Chl-a and all-transß-carotene all follow a mixed first-and second-order mechanism. The first-order rate constant for triplet decay is strongly dose dependent for naphthalene but only slightly dependent and independent of dose for Chl-a and all-transß-carotene, respectively. The rate constants for triplet-triplet annihilation are (1.4 ± 0.3)·109M-1 s-1 for Chl-a and (3.6 ± 0.4)·109M-1 s-1 for all-transß carotene. The nearly constant ratio k(ß-carotene)/k(Chl-a) for the bimolecular triplet energy transfer rate constants is discussed in terms of the molecular shapes of the two molecules. The energetics of the triplet-triplet annihilation of all-transß-carotene are discussed, and it is proposed that production of the excited 1AB state may be a major route in the annihilation process.
U2 - 10.1111/j.1751-1097.1980.tb04048.x
DO - 10.1111/j.1751-1097.1980.tb04048.x
M3 - Journal article
SN - 0031-8655
VL - 32
SP - 719
EP - 725
JO - Photochemistry and Photobiology
JF - Photochemistry and Photobiology
IS - 6
ER -