Five porphyrin-core-dependent metal–organic frameworks and framework-dependent fluorescent properties

Abstract

The reaction of 5,10,15,20-tetra(carboxyphenyl)porphyrin (H₆TCPP) or metalated M-H₄TCPP (M = Co^II, Ni^II, Cu^II and V^IVO) with lead nitrate afforded five metal–organic frameworks (MOFs), [Pb₂(H₂TCPP)]·4DMF·H₂O (1), Pb₂(Co–TCPP)(H₂O)(DMF)]·1.5DMF (2), [Pb₂(Ni–TCPP)(DMF)(H₂O)]·1.5DMF·2H₂O (3), [Pb₂(Cu–TCPP)(DMF)(H₂O)]·1.5DMF·2H₂O (4) and [Pb₂(VO–TCPP)(H₂O)₂]·4DMF (5). Single crystal X-ray diffraction analysis revealed that the five MOFs based on the TCPP scaffolds differ in framework topologies and porphyrin configurations that are varied from flat to wavy to bowl-shaped. The porphyrin cores play a pivotal role in the formation of the distinct coordination frameworks by controlling the stacking fashion of the porphyrins, the coordination modes of TCPP and the coordination spheres of the Pb²⁺ cations. Solid-state photoluminescent experiments suggest that the emissions of these compounds are dependent on the framework structures, and are insensitive to the porphyrin cores.