Aggregation effect of Thiazine dyes over Singlet Oxygen quantum yield.

VARA, JIMENA; CRISTINA S. ORTIZ

Córdoba

Congreso; Tercera Reunión Internacional de Ciencias Farmacéuticas (RICiFa); 2014

UNITEFA

Thiazine dyes are used for coloring substrates in biological and medical studies and are promising compounds for photosensitizing applications. Recent identification of the monomeric species of these dyes, in our laboratory, showed that the monomer described in literature corresponds to different dimers. Due to the aggregation of photosensitizers reduce the production of singlet oxygen (1O2), the objective of this study was evaluated the 1O2 quantum yield (ΦΔ) of the monomeric and dimeric species of two Thiazines: Azure B (AzB) and monobrominated Azure B (AzBBr). Phosphorescence decay of 1O2 and photooxidation of 9,10-dimethylanthracene (DMA) were used as methodology. Monomeric and dimeric forms were analyzed in N,N-dimethylformamide (DMF) and Methanol (MeOH) employing Rose Bengal (RB) and Methylene Blue (MB) as references. Monomeric species of AzBBr and AzB presented high ΦΔ by luminescence (1.0 and 0.72, respectively) and low values by photooxidation of DMA (0.09 and 0.29, respectively). Moreover, the dimeric species showed similar values of ΦΔ by both methodologies (AzBBr: 0.7 and AzB: 0.3, approximately). Furthermore, the bromination increased ΦΔ of these compounds. To understand the differences obtained to monomers, scavenging effect of AzBBr monomer was evaluated by photooxidation of DMA using RB as photosensitizer. These results indicated that AzBBr monomer could act as physical quencher due to ΦΔ decreased 20% in presence of this dye. This behavior could be associated to these dyes have NN-Dimethylaniline as part of its chemical structure. In addition, dimeric species of AzBBr and AzB presented high ΦΔ because the aromatic amine is involving in different interaction forces that stabilize their aggregates. For this reason, the amines could be less available for the formation of exciplex with 1O2 which trigger the deactivation of excited molecule. In conclusion, the dimeric forms are better 1O2 generator than its respective monomer and could be optimal candidates for use in Photodynamic Therapy.