Hydrogen-Bonded Porphyrinic Solids:  Supramolecular Networks of Octahydroxy Porphyrins

Symmetrically substituted octahydroxy porphyrins, tetrakis(3‘,5‘-dihydroxyphenyl)porphyrin, H 2 T(3‘,5‘-DHP)P, tetrakis(2‘,6‘-dihydroxyphenyl)porphyrin, H 2 T(2‘,6‘-DHP)P, and their Zn(II) and Mn(III) derivatives have been developed as building blocks for supramolecular hydrogen-bonded networks. The crystal structures of a series of these porphyrins exhibit unique structural features through assembly of porphyrin networks by means of directional hydrogen bonding. The position of the peripheral hydroxyl groups, the choice of metallo- or free base porphyrin, and the nature of the solvate (i.e., guest) dramatically influence structural features. A one-dimensional, columnar structure is found for H 2 T(3‘,5‘-DHP)P·5EtOAc. With benzonitrile as solvate, the structure of H 2 T(3‘,5‘-DHP)P·7C 6 H 5 CN changes substantially to a three-dimensional corrugated-sheet structure in order to accommodate a larger pore size. When the hydroxyl substituents are simply changed from the m - to the o - phenyl positions, an essentially two-dimensional layered structure is formed for H 2 T(2‘,6‘-DHP)P·4EtOAc. Zn[T(2‘,6‘-DHP)P](EtOAc) 2 ·2EtOAc has a two-dimensional layered structure, similar to that of its free base H 2 T(2‘,6‘-DHP)P interaction between the aryl rings of the adjacent layers. The crystal structures of both Zn[T(3‘,5‘-DHP)P] and Mn[T(3‘,5‘-DHP)P](Cl) exhibited three-dimensional hydrogen-bonding features. Zn[T(3‘,5‘-DHP)P](THF) 2 ·2THF·3CH 2 Cl 2 has a three-dimensional interconnected layered structure with metalloporphyrins arranged in a slipped stack orientation within the layers. In the structure of Mn[T(3‘,5‘-DHP)P](THF) 2· Cl·2THF·5C 6 H 5 CH 3, a chloride anion dictates the three-dimensional packing by bridging four metalloporphyrin molecules through Cl···HO bonding interactions. In all of these structures, large solvate-filled channels are present with cross-sections as large as 42 Å 2 . The pore volumes of these channels are exceptionally large: as much as 67% of the unit cell volume.