A new family of cationic phthalocyanines containing four guanidinium groups was synthesized in pyridine–HCl at 120 °C; under these conditions zinc was removed from both the starting materials and products to reveal a new synthetic route to metal-free phthalocyanines.

Guanidino-modified phthalocyanines are evaluated in vitro (polymerase-stop assays and FRET) and in cultured cells as G4-DNA ligands and modulators of gene transcription.