Hydrogen-bonded porphyrinic solids: Supramolecular networks of octahydroxy porphyrins

Symmetrically substituted octohydroxy 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 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 H2T(3',5'-DHP)P.5EtOAc. with benzonitrile as solvate, the structure of H2T(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 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](THP)(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 ate present with cross-sections as large as 42 Angstrom(2). The pore volumes of these channels are exceptionally large: as much as 67% of the unit cell volume.