5,10,15,20-tetra(4-pyridyl)porphyrinato zinc coordination polymeric particles with different shapes and luminescent properties

Abstract

Micro-scale three-dimensional coordination polymer particles (CPPs) have been synthesized from the surfactant-assisted reaction of Zn(OAc)₂·2H₂O and 5,10,15,20-tetra(4-pyridyl)porphyrin (H₂TPyP) in DMF. The three-dimensional (3D) micro-prisms and micro-octahedra of the CPPs were obtained at different temperatures as found by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and a statistical analysis of the size distribution results. X-Ray diffraction (XRD) analysis revealed a circular hexametric cage structure cross-linked by a Zn–N axial coordination of the pyridyl ligands inside the micro-scale CPPs. Further support for this coordination polymerization mode of the micro-CPPs came from IR spectroscopy. The UV–vis spectra clearly show the formation of J-type aggregates in both the microstructures. The micro-CPPs show a stronger luminescence intensity over the individual porphyrin molecules, which is presumably due to the high surface area of the ZnTPyP-CPPs. Nevertheless, nitrogen adsorption/desorption isotherm measurements were performed to confirm the larger surface area and increased porosity of the micro-prisms and micro-octahedra relative to the self-assembled micro-rods of ZnTPyP, indicating the potential application of the two CPPs microstructures in the field of gas adsorption. The surfactant-assisted synthetic route appears to provide a promising method for the construction of highly organized three-dimensional organic micro-structures of 5,10,15,20-tetra(4-pyridyl)porphyrin derivatives.