Lateral, Chiral Tin(IV) Porphyrin Assemblies

The μ-Oxo stacks of tin(IV) porphyrins rearrange to staircase-type and lateral aggregates upon replacement of the oxygen ligands by chloride ions. The lateral aggregation of tin(IV) 2,18-dipropionate porphyrins in hydrochloric acid at pH 0–0.5 is favoured by 8,13-ethyl groups instead of the natural 8,13-vinyl groups of protoporphyrin IX and is impeded by hydrogen atoms at these positions. Replacement of axial chloride counterions to the tin(IV) central ions by cyanate counterions at pH 4.5 leads to similar aggregates if the cyanate ions are connected by hydrogen bonding to acetic or lactic acid. In this case, aggregation is not necessarily impeded by hydrogen atoms at positions 8 and 13. D- and L-lactic acid enforce chiral assemblies of the tin(IV) deuteroporphyrin 1a with mirror image CD (circular dichroism) spectra (θ ≈ 8 × 10 5 deg cm 2 dmol −1 ), whereas the gluconoyl hydrazide-substituted tin(IV) deuteroporphyrin 1d does not form aggregates at all.