Spectrophotometric studies of charge-transfer complexes formed with ions N,N'-alkyldiyl-bis(pyridinium) derivatives and iodide.

The charge-transfer complexes (CTC) between electron donor iodide and pyridinium dimers and monomers as acceptors have been studied spectrophotometrically in acetonitrile, DMSO and water. The dimers were: N,N'-alkyldiyl-bis(4-cyanopyridinium) and N,N'-alkyldiyl-bis(2-bromopyridinium), and the monomers were: N-alkyl-4-cyanopyridinium and N-alkyl-2-bromopyridinium, bridged by n methylene spacers. The formation constant (K), molar absorptivity (ε), fluorescence-quenching constant (K) were determined.

Evaluation of the photodynamic activity of xanthene dyes on Artemia salina described by chemometric approaches.

The development of drugs for photodynamic therapy (PDT) is an important area of research due to their growing use in medical applications. Therefore, it is important to develop new bioassay methods for PDT photosensitizers that are inexpensive, easy to handle and highly sensitive to environmental conditions. Xanthene dyes (fluorescein, rose bengal B, erythrosine B and eosin Y) with LED light sources were investigated using Artemia salina as a bioindicator of photodynamic activity.

Self-aggregation processes of 1,6-diphenyl-1,3,5-hexatriene in water/ethanol mixtures with high water percentages.

This work describes the behavior of 1,6-diphenyl-1,3,5-hexatriene (DPH) in ethanol/water mixtures. The dependence of DPH photophysical properties (absorption and fluorescence emission) on the water percentage in ethanol indicates that DPH undergoes self-aggregation processes in solvent conditions above a critical water content. Evidence such as an additional absorption band, Beer's law deviation, kinetic behavior, and other experimental results obtained from temperature variation and surfactant addition demonstrated the presence of several types of DPH aggregates.

pKa determinations of xanthene derivates in aqueous solutions by multivariate analysis applied to UV-Vis spectrophotometric data.

Xanthenes form to an important class of dyes which are widely used. Most of them present three acid-base groups: two phenolic sites and one carboxylic site. Therefore, the pKa determination and the attribution of each group to the corresponding pKa value is a very important feature.

Spectroscopic, redox and magnetic properties of a tetraiminediphenolate iron(II) macrocyclic complex: a model compound for iron proteins.

The title complex [Fe(II)(tidf-H2)(H2O)2](ClO4)2*H(2)O (tidf-H2 = tetraiminediphenolate ligand) has been prepared from a transmetallation reaction between [Mg2(tidf)](NO3)2*4H2O and an iron(II) salt in methanolic solutions under inert atmosphere conditions. It was characterized by analytical, magnetic and spectroscopic methods (Mossbauer, FTIR, UV-vis), by cyclic voltammetry as well as spectroelectrochemistry.