High-pressure conditions for improved synthesis of phthalocyanines

Abstract

Improved rates of formation and yields of phthalocyanines are observed when the reaction between phthalonitrile and a metal salt is carried out at pressures around 10 kbar. The reaction also benefits from the presence of a superbase, 1,5-diazabicycio[4.3.0]non-5-ene or 1,8-diazabicyclo[5.4.0]undec-7-ene, and a reducing agent, hydroquinone. In addition to providing superior yields of metallophthalocyanines from a variety of metal salts, these improvements permit the synthesis of phthalocyanines otherwise difficult to obtain. High pressure combined with a reducing agent is particularly advantageous. In the absence of a metal salt, good yields of metal-free phthalocyanine were obtained.