Novel Pathway to Synthesize Unsymmetrical 2,3,9,10,16,17,23-heptakis(alkoxyl)-24-mono(dimethylaminoalkoxyl)phthalocyanines

Abstract

A new pathway by means of transetherification has been developed to synthesize novel unsymmetrical 2,3,9,10,16,17,23-heptakis(alkoxyl)-24-mono(dimethylaminoalkoxyl)phthalocyanine compounds. Cyclic tetramerization of 4,5-di(alkoxyl)phthalonitrile in refluxing dimethylamino-alcohol with high boiling point such as dimethylaminoethanol (DMAE) and 1-dimethylamino-2-propanol in the presence of lithium and pyrazino[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile followed by treatment with acetic acid led to the isolation of a series of unsymmetrical metal free 2,3,9,10,16,17,23-heptakis(alkoxyl)-24-mono(dimethylaminoalkoxyl)phthalocyanine compounds H(2){Pc(OR)(7)[OR'N(CH(3))(2)]} [R = C(4)H(9), C(5)H(11), C(8)H(17) and R' = C(2)H(4); R = C(4)H(9) and R' = CH(CH(3))CH(2)] (1-4). Metal insertion into unsymmetrical metal free phthalocyanines (Pc's) using Cu(OAc)(2)·H(2)O in dimethylformamide (DMF) at 140 °C easily afforded corresponding unsymmetrical phthalocyaninato copper complexes Cu{Pc(OR)(7)[OR'N(CH(3))(2)]} (5-8) in good yields. These novel unsymmetrical phthalocyanine compounds have been characterized by a series of spectroscopic methods including (1)H NMR, electronic absorption, IR, and mass spectroscopy in addition to elemental analysis. Their electrochemistry was also studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. The present result will be helpful for designing and preparing unsymmetrical phthalocyanines with potential applications in dye-sensitized solar cells.