Solvent-free synthesis of soluble, near-IR absorbing titanyl phthalocyanine derivatives

Solvent-free synthesis of a series of alkylthio-substituted titanyl phthalocyanine (TiOPc) derivatives starting from the corresponding phthalonitriles (Pn) is reported. This methodology eliminates the formation of the unmetalated phthalocyanine (H2Pc), a side product that makes purification difficult. The alkylthio groups on the reported derivatives enhance solubility in common organic solvents and shift the absorption to the near-IR region.