“Pinwheel-like” phthalocyanines with four non-peripheral chiral menthol units: Synthesis, spectroscopy, and electrochemistry

Abstract A pair of “pinwheel-like” metal free phthalocyanines, ( d )- and ( l )-1,8,15,22-tetrakis(2-isopropyl-5-methylcyclohexoxyl)phthalocyanine (1) were isolated for the first time from cyclic tetramerization of ( d )- and ( l )-3-(2-isopropyl-5-methylcyclohexoxyl)-1,2-dicyanobenzene (2) , respectively, in refluxing n -pentanol in the presence of lithium pentanoate followed by treatment with acetic acid. Owing to the steric hindrance of the bulky menthol groups, C4 tetra- α -substituted phthalocyanine 1 is the main phthalocyanine product generated and then could be purified readily by column chromatography. The newly prepared phthalocyanine has been characterized by a series of spectroscopic technique including MALDI-TOF mass, NMR, electronic absorption and IR spectroscopy in addition to elemental analysis. In addition, their electrochemical properties have also been studied by cyclic voltammetry measurement.