NMR spectroscopic evidence for the self-association of some asymmetrically substituted phthalocyanines in solution

H-1 NMR data obtained for two series of asymmetrically octasubstituted metal-free and zinc phthalocyanines, bearing one or two hydroxyalkyl groups, indicate a degree of solution phase aggregation particular to the systems. The metal-free derivatives appear to stack cofacially through the interaction of their pi systems and give rise to unusually well resolved, solvent, temperature and concentration dependent H-1 NMR spectra. Structural features for the aggregates, in which the phthalocyanine rings are cofacial but offset in a particular way, are proposed based on the NMR data. The zinc derivatives appear to form dynamic aggregates in solution in which the oxygen borne by one of the substituents coordinates to the zinc at the centre of the core through an inter- and/or intramolecular interaction leading to the temperature dependent H-1 NMR spectra that are observed. Copyright (C) 2003 Society of Porphyrins & Phthalocyanines.