Ammonia-Free and One-Pot Synthesis of Di-Chloro Silicon Phthalocyanine and Naphthalocyanine

Abstract

Silicon phthalocyanines (SiPcs) and silicon naphthalocyanines (SiNcs) are promising and versatile organic materials with applications spanning across organic electronics, photocatalysis, and photodynamic therapy. Specifically, the availability for modification of periphery sites and axial positions enables tailoring for solubility, bandgap tuning, or even biological targeting. The dichlorinated species (Cl2-SiPc and Cl2-SiNc) are particularly attractive due to the facile substitution of the axial chloride groups. However, conventional syntheses rely on a two-step protocol that requires the use of an ammonia gas tank at high temperatures. Here, we report a safer, one-pot synthesis of Cl2-SiPc and Cl2-SiNc directly from unsubstituted phthalonitrile and 2,3-dicyanonaphthalene, respectively. By adapting the alternative route proposed by Lessard et al. which uses lithium bis(trimethylsilyl) amide (LiHMDS) in place of ammonia gas, we achieved up to a 45% macrocyclic conversion to-date. Overall, the adapted ammonia-free approach provides a synthetically relevant and sustainable platform for the preparation and functionalization of silicon phthalocyanines and naphthalocyanines. We also studied the microwave process and confirmed also that the silicon phthalocyanines can be formed via the microwave.