Enhanced degradation of 2,6-dimethylphenol by photocatalytic systems using TiO2 assisted with H2O2 and Fe(III).

In this study, several photocatalytic degradation systems were investigated using 2,6-dimethylphenol (2,6-DMP) as a model compound. Highly reactive species are formed in four systems, Fe(III), TiO2, TiO2/H2O2 and TiO2/Fe(III) where complete degradation of 2,6-DMP was achieved under UV radiation. Photodegradation of the 2,6-DMP has been described by pseudo-first order kinetic model in the presence of TiO2. In UV/TiO2-H2O2 system, the addition of H2O2 in the TiO2 suspension improves the degradation rate of 2,6-DMP from 70% to 100% for a H2O2 concentration of 10-2 M in 3 h. In homogeneous system, HO• and Fe2+ can be generated by the irradiation of Fe(III) solution. The speciation of Fe(III) obtained from Visual MINTEQ soft showed the formation of several species and Fe(OH)2+ were the most predominant and active species in a pH range of 2.5-3.5. At a low concentration of TiO2 (30 mg L-1), an important positive effect due to the iron addition has been shown in TiO2/Fe(III) system, the entrance of metallic ions at different concentrations enhanced the photocatalytic activity of TiO2. A degradation percentage of 90% was achieved in the UV/TiO2-Fe(III) system under optimal conditions against 57% in UV/TiO2 system. Strong synergistic effect was observed in the UV/TiO2-H2O2 binary system. On the basis of literature, a pathway for 2,6-DMP degradation was proposed. The mechanism of degradation of the 2,6-DMP did not involve only HO• radicals, an interaction of Fe(III) in the excited state with 2,6-DMP occurred giving rise to the formation of 2,6-dimethylphenoxyl radical.

Carbazole derivatives containing chalcone analogues targeting topoisomerase II inhibition: First principles characterization and QSAR modelling.

Recently, a series of carbazole derivatives containing chalcone analogues (CDCAs) were synthetized as potent anticancer agents and apoptosis inducers. These compounds target the inhibition of topoisomerase II and present cytotoxic activities. After comparison to experiment, we validated the use of B3LYP, a density functional theory-based approach, to describe the structure and molecular properties of the carbazole subunit and CDCAs compounds of interest. Then, we derived relationships between the chemical descriptors and activity of these carbazole derivatives using multi-parameter optimization and quantitative structure activity relationships (QSAR) approaches. For the QSAR studies, we used multiple linear regression and artificial neural network statistical modelling. Our predicted activities are in good agreement with the experimental ones. We found that the most important parameter influencing the activity of the considered compounds is the octanol-water partition coefficient, highlighting the importance of flexibility as a key molecular parameter to favor cell membrane crossing and enhance the action of these CDCAs against topoisomerase II. Our results provide useful guidelines for designing new oral active CDCAs medicaments for cytotoxic inhibition.