Photoproperties of alkoxy-substituted phthalocyanines with deep-red optical absorbance.
Triplet-state properties of 1,4,8,11,15,18,22,25-octa-n-butoxyphthalocyanine and its zinc derivative were determined for the first time. The T1 state of the metal-free phthalocyanine was characterized by a short lifetime (tau T = 17 microseconds) and low quantum yield (phi T = 0.095), and quenching of the triplet by O2 occurred with a bimolecular rate constant (kT sigma = 1.3 x 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 tau T (60 microseconds) and phi T (0.5). Quenching by O2 produced singlet oxygen with nearly 100% efficiency, and kT sigma (1.7 x 10(9) M-1s-1) was close to the spin-statistical diffusion-controlled limit. Phosphorescence measurements showed the energy of the T1 state of ZnPc(OBu)8 to be 100 kJ/mol, which is 6 kJ/mol above the 1 delta g state of O2. 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.
W E
WE
Ford
B D
BD
Rihter
M E
ME
Kenney
M A
MA
Rodgers
D007211:Indoles; D009942:Organometallic Compounds; D010778:Photochemotherapy / Q000379:methods*; D013057:Spectrum Analysis; D013329:Structure-Activity Relationship; D015032:Zinc
D007211:Indoles; D009942:Organometallic Compounds; C061188:zinc 1,4,8,11,15,18,22,25-octa-n-butoxyphthalocyanine; C061186:1,4,8,11,15,18,22,25-octa-n-butoxyphthalocyanine; D015032:Zinc