Effect of the coordination of π-acceptor 4-cyanopyridine ligand on the structural and electronic properties of meso-tetra(para-methoxy) and meso-tetra(para-chlorophenyl) porphyrin cobalt(ii) coordination compounds. Application in the catalytic degradation of methylene blue dye

Abstract

To examine the influence of both the important π-acceptor character of the 4-cyanopyridine ligand and the nature of the para-substituted phenyls of meso-porphyrins on the electronic, electrochemical and structural properties of cobaltous metalloporphyrins, we prepared and fully characterized two coordination compounds: the (4-cyanopyridine)[meso-tetra(para-methoxyphenyl)porphyrinato]cobalt(II) and the (4-cyanopyridine)[meso-tetra(para-chlorophenyl)porphyrinato]cobalt(II) with the [Co^II(TMPP)(4-CNpy)] and [Co^II(TClPP)(4-CNpy)] formulas (complexes 1–2). The solution structures of compounds 1–2 were confirmed by ¹H NMR spectroscopy and mass spectrometry methods. They were further characterized by cyclic voltammetry and photoluminescence studies. The X-ray molecular structure data show that the Co-TClPP-4-NCpy derivative (2) exhibits high ruffling deformation compared to that of the Co-TMPP-4-CNpy species (1). Notably, the crystal packing of complex 1 shows the formation of Co⋯Co supramolecular dimers with a distance of 5.663 Å. As an application of our two cobaltous compounds, an investigation involving complexes 1–2 in the degradation of the methylene blue dye in the presence and absence of H₂O₂ in aqueous solutions was carried out. These promising results show that 1–2 can be used as catalysts in the degradation processes of dyes.