Premium
PHOTOPROPERTIES OF ALKOXY‐SUBSTITUTED PHTHALOCYANINES WITH DEEP‐RED OPTICAL ABSORBANCE
Author(s) -
Ford W. E.,
Rihter B. D.,
Kenney M. E.,
Rodgers M. A. J.
Publication year - 1989
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1989.tb04160.x
Subject(s) - alkoxy group , absorbance , chemistry , photochemistry , organic chemistry , chromatography , alkyl
— Triplet‐state properties of 1,4,8,11,15,18,22,25‐octa‐n‐butoxy phthalocyanine and its zinc derivative were determined for the first time. The T 1 state of the metal‐free phthalocyanine was characterized by a short lifetime (τ T = 17 µs) and low quantum yield (φ T = 0.095), and quenching of the triplet by O 2 occurred with a bimolecular rate constant ( k Tσ = 1.3 times 10 8 M ‐1 s ‐1 ) that is indicative of an endogonic reaction. The zinc complex (ZnPc(OBu) 8 ) was markedly better as a triplet photosensitizer with respect to both t T (60 µs) and φ T (0.5). Quenching by O 2 produced singlet oxygen with nearly 100% efficiency, and k Tσ (1.7 times 10 9 M ‐1 s ‐1 ) was close to the spin‐statistical diffusion‐controlled limit. Phosphorescence measurements showed the energy of the T 1 state of ZnPc(OBu) 8 to be 100 kJ/mol, which is 6 kJ/mol above the l δ g state of O 2 . These photoproperties, together with Q‐band absorption maxima in the mid‐700 nm range indicate that metal‐centered 1,4,8,11,15,18,22,25‐octaalkoxyphthalocyanines have excellent potential as sensitizers in photodynamic therapy.