Effect of aza substitution on the photophysical and electrochemical properties of porphycenes: Characterization of the near-IR-absorbing photosensitizers 2,7,12,17-tetrakis(p-substituted phenyl)-3,6,13,16-tetraazaporphycenes.
The need for new photodynamic-therapy photosensitizers has stimulated the search of new families of compounds absorbing strongly in the 700-900 nm range, the region where tissue is most transparent to radiation capable to induce the photodynamic effect. Using computational chemistry techniques, 3,6,13,16-tetraazaporphycenes were previously identified as interesting target candidates. This work reports on the photophysical and electrochemical properties of selected members of this new family of macrocycles. Compared to porphycenes, the tetra-aza counterparts show stronger absorption in the near-infrared, lower-lying singlet and triplet excited states, and substantially larger internal conversion quantum yield (Phi(IC) = 0.93). Energy transfer to oxygen is observed, which results in the formation of the cytotoxic species singlet oxygen. The process is found to be reversible, consistent with a triplet-energy value close to that of singlet oxygen.
Rubio
Noemí
N
Grup d'Enginyeria Molecular, Institut Químic de Sarrià, Universitat Ramon Llull, Via Augusta 390, 08017 Barcelona, Spain.
Sanchez-García
David
D
Jiménez-Banzo
Ana
A
Rey
Oscar
O
Borrell
José I
JI
Teixidó
Jordi
J
Nonell
Santi
S
D001372:Aza Compounds / Q000737:chemistry*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004563:Electrochemistry; D005453:Fluorescence; D010777:Photochemistry; D017319:Photosensitizing Agents / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry*; D026082:Singlet Oxygen / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D019207:beta Carotene / Q000737:chemistry
C099499:2,7,12,17-tetraphenylporphycene; D001372:Aza Compounds; D017319:Photosensitizing Agents; D011166:Porphyrins; D019207:beta Carotene; D026082:Singlet Oxygen