Self-assembly patterns of porphyrins in crystals. Structures of hydrogen-bonding and coordination polymers of manganese tetra(carboxyphenyl)porphyrin

Abstract

Crystallizations of manganese-tetra(4-carboxyphenyl)porphyrin chloride from different reaction environments led to the formation of new extended polymeric architectures sustained either by cooperative hydrogen-bonding or by self-coordination of the porphyrin units. In one mode the manganese ion in the metalloporphyrin core coordinates axially from both sides to water molecules. The porphyrin species then associate to each other into open layered arrays by multiple hydrogen bonding between the carboxylic functions of adjacent units. The offset-stacked layers are tightly inter-linked (at an average spacing of 3.94 Å) by additional hydrogen bonding between the apical water ligands of one array and the carboxylic groups of neighboring assemblies. Thus resulting interporphyrin organization represents a single-framework hydrogen-bonding polymer. The interporphyrin voids within the layers are accommodated by guest solvent components. In another mode, an unprecedented two-dimensional coordination polymer is assembled from the tetra-acid building blocks by direct coordination of the metalloporphyrin cores and carboxylic groups to the corresponding topical sites of adjacent species. Stacking of the polymeric layered arrays in the condensed crystalline phase incorporates molecules of crystallization solvent within the inter-layer voids.