Near-infrared absorbing π-extended hexadeca substituted phthalocyanines

Two new phthalonitriles 1 and 2, extended with biphenylethynyl and diphenylacetylenyl, were synthesized through a combination of Corey-Fuchs and palladium-catalyzed Sonogashira coupling reactions. The structures of 1 and 2 were revealed through single-crystal X-ray analysis. Cyclotetramerization of these phthalonitriles led to the corresponding 1,4,8,11,15,18,22,25-octabutoxy-2,3,9,10,16,17,23,24-octakis(biphenyl) and (diphenylacetylenyl) phthalocyanines. The longer substituent, namely diphenylacetylenyl, is slightly more effective than biphenyl in shifting the Q band to a longer wavelength. A cathodic shift in first oxidation potential indicated the destabilization of the HOMO energy levels that results from non-peripheral substitution and extended pi-conjugation. (C) 2019 Elsevier B.V. All rights reserved.