Amine-assisted solubilization of unsubstituted zinc phthalocyanine for film deposition purposes

Typical zinc phthalocyanines (ZnPc) exhibit poor solubility in common solvents and, hence, are processed into thin films mostly from the vapor phase. The present work discloses how these limitations can be effectively overcome. Specifically, highly concentrated molecular solutions of unsubstituted ZnPc are prepared by combining a weakly structured ZnPc polymorph with binary liquid systems composed of a π-accepting solvent and a simple nitrogenous base, such as ammonia or tertiary aliphatic amine. The amine-assisted solubilization of ZnPc is rationalized by quantitative analysis of optical spectra and electrostatic potential maps of the dye molecule. A volatile aminoalcohol is proposed in order to rationally modify the habit of ZnPc crystallites and concurrently to produce uniform deposition of the crystallites by drop-casting the dye solutions onto a glass substrate. Finally, a versatile algorithm for wet-processed ZnPc films is declared.