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

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-alpha-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. (C) 2018 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.