Hydrogen-Bonded Porphyrinic Solids: Supramolecular Networks of Octahydroxy Porphyrins

Symmetrically substituted octahydroxy porphyrins, tetrakis(3′,5′-dihydroxyphenyl)porphyrin, H2T(3′,5′DHP)P, tetrakis(2′,6′-dihydroxyphenyl)porphyrin, H2T(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 metalloor free base porphyrin, and the nature of the solvate (i.e., guest) dramatically influence structural features. A one-dimensional, columnar structure is found for H2T(3′,5′-DHP)P‚5EtOAc. With benzonitrile as solvate, the structure of H2T(3′,5′-DHP)P‚7C6H5CN 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 mto the o-phenyl positions, an essentially two-dimensional layered structure is formed for H2T(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 H2T(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‚3CH2Cl2 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‚5C6H5CH3, 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 Å2. The pore volumes of these channels are exceptionally large: as much as 67% of the unit cell volume.