Synthesis and evaluation of photophysical and electrochemical properties of vinyl chalcogenide derivatives of phenothiazines

DILELIO, MARINA CARDOSO; KAUFMAN, TEODORO S.; IGLESIAS, BERNARDO ALMEIDA; SILVEIRA, CLAUDIO C.

DYES AND PIGMENTS

ELSEVIER SCI LTD

Año: 2022 vol. 198 p. 109 - 982

0143-7208

The Wittig-Horner mediated syntheses of phenothiazines carrying vinylsulfide and vinylselenide motifs attachedto the aromatic ring(s) or connected to the central nitrogen atom of the heterocycle, and the subsequent study oftheir photophysical and electrochemical properties, are reported. These compounds were obtained as mixtures ofgeometric isomers, in good to excellent yields. To complete the study, a small set of vinylsulfoxide and vinylsulfonederivatives was also prepared from the corresponding oxidized phosphinoxides. The photophysicalproperties of the compounds were examined in solvents of varying polarity, in which they presented absorptionmaxima in the UV region, with molar absorptivity coefficients compatible with symmetry-allowed π?π* electronictransitions. The heterocyclic derivatives were fluorescent. Compounds bearing vinylsulfide moietiesassociated to the nitrogen atom of the heterocycle displayed less intense fluorescence than the phenothiazinederivatives carrying vinylchalcogenides bonded to the aromatic ring; the latter also exhibited more red-shiftedabsorption spectra, and Stokes shifts in the range 6115?8170 cm􀀀 1 with weak dependence of solvent polarity.The sulfoxide and sulfones displayed more red-shifted spectra than the corresponding sulfides. The cyclic voltammogramsof all derivatives exhibited a common pattern of reversible or quasi-reversible processes in theanodic region, related to the phenothiazine unit.