Structural patterns in clathrates and crystalline complexes of zinc-tetra(4-chlorophenyl)porphyrin and zinc-tetra(4-fluorophenyl)porphyrin

Twelve new crystalline materials based on zinc-tetra(4-chlorophenyl)porphyrin (8 compounds) and zinc-tetra(4-fluorophenyl)prophyrin (4 compounds) building blocks have been prepared and characterized by X-ray diffraction analysis. Several different modes of guest solvent incorporation into the porphyrin lattice, including enclathration (of solvents of low polarity) and complex formation (with strong Lewis bases), and of intermolecular organization have been detected. Unique interporphyrin architectures, affected by directional Cl...Cl interactions, characterize most of the known solid structures of the chlorosubstituted materials. A small number of the latter, as well as the fluorosubstituted derivatives, exhibit interporphyrin arrangements of the type which are commonly observed in the clathrates of unsubstituted tetraphenylmetalloporphyrins. The pore structure of these compounds is affected to a large extent by the nature of the incorporated solvate and, consequently, the degree of coordination of the metal center. In crystals of four-coordinate porphyrins the solvent guest components are usually incorporated into channel-type cavities formed between columns and layers of densely stacked hosts. In five-coordinate and six-coordinate materials the guest sites coincide with the axial coordination sites of the porphyrin metal atoms. The latter structures reveal a tight fit between adjacent layers of the complexed entities, the axial ligands of one layer being incorporated into localized interporphyrin cavities of another layer. Dipolar forces play also an important role in the interporphyrin organization.