Chemosensoric properties of porphyrin analogues ionized forms by spectrophotometry and quantum chemistry: 5,10,15,20-tetraphenyl-21-thia- and 5,10,15,20-tetraphenyl-21,23-dithiaporphyrins

Modification of porphyrins by a replacement of N atom(s) with a heteroatom(s), resulted in so called heteroporphyrins, exhibits interesting physicochemical properties. In this work, the spectral properties of ions and neutral forms of 5,10,15,20-tetraphenyl-21,23-dithia porphyrin (S2PP) and 5,10,15,20-tetraphenyl-21-thia-porphyrin (HSPP) have been investigated. According to spectrophotometric analysis in acetonitrile – perchloric acid solution, the dication H2S2PP2+ reveals an ability to coordinate two ClO4- anions, which not happens for H3SPP2+. This fact observed in UV–Vis absorption spectra indicates the possibility of exhibiting chemosensory properties of S2PP molecules. Geometries of the neutral and ionized forms were derived from B3LYP/cc-pVTZ calculations. Perimeters of the cavities increase in the series: H2PP–HSPP–S2PP. This trend is kept for the ionized forms; protonation expands the cavity perimeter. Electron density distributions were analyzed in terms of quantum theory atoms in molecule (QTAIM). The UV-vis spectra simulated by TDDFT fits with the experimental results.