Synthesis and spectral study of tetra(2,3-thianaphtheno)-porphyrazine, its tetra-tert-butyl derivative and their Mg(II), Al(III), Ga(III) and In(III) complexes

Starting from easily available thiophenols (PhSH (1a), 4-tert-butyl-PhSH (1b)) and oxalylchloride we have prepared 2,3-thianaphtenequinones 2a,b which were then successively converted to thianaphthene-2,3-dicarboxylic acids 4a,b their imides 10a,b, diamides 9a,b and finally to thianaphthene-2,3-dicarbonitriles 11a,b — the key precursors for the series of novel porphyrazines bearing four 2,3-annulated thianaphthene moieties. The free-bases 12a,b were obtained by cyclotetramerization of the dinitrile 11a,b in the presence of lithium in n-pentanol, while the reaction with magnesium(II) butoxide in n-butanol leads to the Mg(II) complex 13a. Complexes with Al(III) (14a,b), Ga(III) (14a,b) and In(III) (14a,b) were obtained by the template cyclotetramerization of the dinitriles 11a,b in a melt with the corresponding (hydroxy)acetates. Tetra(2,3-thianaphtheno)porphyrazine 12a and its metal complexes 13a–15a are only sparingly soluble in common organic solvents, the solubility is enhanced for their tert-butyl substituted derivatives 12b, 14b–16b. The study of the electronic absorbtion spectra has revealed that the extension of the porphyrazine π-chromophore by fusion of four thianaphthene fragments due to the angular type of their annulation (similar to that found in 1,2-naphthalocyanines) and negative inductive effect of the sulfur atoms has an effect on its spectral properties which is less than in the case of the isoelectronic naphthalene rings fusion and is comparable with the influence of four benzene rings in phthalocyanines.