Framework coordination polymers of tetra(4-carboxyphenyl)porphyrin and lanthanide ions in crystalline solids

Abstract

Targeted synthesis of framework coordination polymers was achieved by reacting meso-tetra(4-carboxyphenyl)porphyrin with common salts of lanthanide metal ions. The large size, high coordination numbers and strong affinity for oxo ligands of the latter, combined with favourable hydrothermal reaction conditions in acidic environments, allowed the formation of open three-dimensional single-framework architectures in which the tetra-dentate porphyrin units are inter-coordinated by multinuclear assemblies of the bridging metal ions, which serve as construction pillars, into infinite architectures. Three different modes of coordination polymerisation were characterized by single-crystal X-ray diffraction. They differ by the nuclearity of the metal connectors. All structures exhibit, however, layered organization of the porphyrin-metal domains, and periodically spaced solvent accessible channel voids that penetrate through these layers throughout the corresponding crystals. Thermal analysis provided additional insight into the stability of these polymeric materials.