Crystalline assemblies of porphyrins with mixed bromophenyl and pyridyl meso-substituents and manifestation of supramolecular chirality induced by inter-porphyrin Br?N halogen bonds

摘要

Four new crystalline solids based on the zinc-5,15-bis(4′- bromophenyl)-10,20- bis(4′-pyridyl)porphyrin (ZnDBDPyP) and zinc/copper-5,10,15-tris(4′-bromophenyl)-20-(4′-pyridyl)-porphyrin (Zn/CuTBMPyP) platforms as building blocks, have been prepared and structurally analyzed by X-ray diffraction in order to examine whether the Br?N halogen bond can be effective in directing the supramolecular assembly of this functionalized porphyrins, in a similar way observed earlier for their iodophenyl-substituted analogs. The zinc ion in the porphyrin core was protected by an external ligand (pyridyl or methanol) to prevent its possible coordination to the pyridyl-porphyrin substituents. Neither the bis-pyridyl Zn(py)DBDPyP scaffold nor the Zn(MeOH)/CuTBMPyP exhibited inter-porphyrin halogen bonding in their corresponding crystals. Only the layered self-assembly of the Zn(py)TBMPyP building block was found to be uniquely directed by Br?N halogen bonds, as well as by Br?Br and Br?π interactions. This observation supports our notion that asymmetric functionalization of the tetraarylporphyrin scaffold, combined with directional interporphyrin interactions (as halogen bonding), represent a promising approach to supramolecular chirality.