In the present work, we have synthesized and fully characterized the photophysical and photochemical properties of a selected group of N-methyl-b-carboline derivatives (9-methylb-carbolines and iodine salts of 2-methyl-and 2,9-dimethyl-bcarbolinium) in aqueous solutions, in the pH range 4.0-14.5. Moreover, despite the quite extensive studies reported in the literature regarding the overall photophysical behavior of Nunsubstituted bCs, this work constitutes the first full and unambiguous characterization of anionic species of N-unsubstituted bCs (norharmane, harmane and harmine), present in aqueous solution under highly alkaline conditions (pH > 13.0). Acid dissociation constants (K a ), thermal stabilities, room temperature UV-visible absorption and fluorescence emission and excitation spectra, fluorescence quantum yields (Ф F ) and fluorescence lifetimes (s F ), as well as quantum yields of singlet oxygen production (Ф D ) have been measured for all the studied compounds. Furthermore, for the first time to our knowledge, chemometric techniques (MCR-ALS and PARAFAC) were applied on these systems, providing relevant information about the equilibria and species involved. The impact of all the foregoing observations on the biological role, as well as the potential biotechnological applications of these compounds, is discussed.

Humic-like substances (HLS) extracted from urban wastes have been tested as auxiliaries for the photo-Fenton removal of thiabendazole (TBZ) under simulated sunlight. Experimental design methodology based on Doehlert matrices was employed to check the effects of hydrogen peroxide concentration, HLS amount as well as TBZ loading; this last parameter was studied in the range 25-100 mg/L, to include values below and above the limit of solubility at pH = 5. Very satisfactory results were reached when TBZ was above solubility if HLS and HO amounts were high. This could be attributed to an interaction of HLS-TBZ that enhances the solubility of the pollutant. Additional evidence supporting the latter interaction was obtained by fluorescence measurements (excitation emission matrices) and parallel factor analysis (PARAFAC).