Solid-State Supramolecular Chemistry of Porphyrins. Ligand-Bridged Tetraphenylmetalloporphyrin Dimers

Eight new crystalline materialsbased on ligand-bridged dimers of either Zn(II)- orCo(II)-tetraphenylporphyrins have been prepared andcharacterized by X-ray diffraction analysis. These supramolecular entities have a ``wheel-and-axle'' typeshape, the elongated bidentate ligands1,3-diaminopropane, 1,4-diaminobutane, 4,4'-bipyridyl, 1,2-bis(4-pyridyl)ethene or1,2-bis(4-pyridyl)ethane coordinating axially on bothsides to the metal centers of the porphyrin species. They vary from one another by the length of the ligandspacer, the distance between the two porphyrincomponents ranging from 9.4 Å to 14.0 Å. Theintermolecular organization in these structures ischaracterized by a similar chain motif in whichadjacent oligomeric units interlock into one another. In spite of the steric constraint imposed by thebridging ligand, this packing preserves the typicalcorrugated stacked arrangement of the porphyrinframeworks which has been commonly observed inclathrates of monomeric tetraarylporphyrins. It alsoinduces in most cases large voids between theinterlocked motifs, causing enclathration of solventmolecules in the crystal lattice. The experimentallyestablished geometries of these oligomers and theircrystal packing modes provide useful information forfurther crystal engineering efforts of polymericmultiporphyrin domains.