Cationic Exchange Reactions Involving Dilithium Phthalocyanine

Dilithium phthalocyanine (Li₂Pc) consists of an aromatic macrocycle possessing a doubly negative charge and two Li⁺ counterions. One Li⁺ ion is easily displaceable while the other remains coordinated to the phthalocyanine ring. The displaceable Li⁺ cation can be exchanged with other cations, such as a singly charged tetra-alkyl ammonium cation, by using several variations of a general procedure. It has been demonstrated that tetraalkylammonium lithium phthalocyanines (TAA-LiPcs) can be successfully and reproducibly synthesized with yields ranging from 54.5% up to 64.3%. All TAA-LiPcs demonstrated poor solubilities from approximately <0.2 mg/mL to 5 mg/ml in the solvents tested (with the exception of tetrapropylammonium lithium phthalocyanine and tetrahexylammonium lithium phthalocyanine). All of the TAA-LiPcs synthesized were dark-purple in color, with the exception of tetraheptylammonium lithium phthalocyanine and tetraoctylammonium lithium phthalocyanine. These two compounds were dark –blue in color. Melting points varied greatly from >370.4°C to 157.9°C and depended greatly upon the alkyl-chain length of the exchanged cation.