Preparation of [meso-tetraphenylchlorophinato]nickel(II) by stepwise deformylation of [meso-tetraphenyl-2,3-diformyl-secochlorinato]nickel(II): conformational consequences of breaking the structural integrity of nickel porphyrins

The stepwise, Wilkinson’s catalyst-induced decarbonylation of [meso-tetraphenyl-2,3-diformylsecochlorinato]Ni(II) (4) to produce the monoformylated pigment [meso-tetraphenyl-2-formylsecochlorinato] (5) and [meso-tetraphenylchlorophinato]Ni(II) (6) is described. Thus, we have shown how to degrade one pyrrolic unit of the starting material, [meso-tetraphenylporphyrinato]Ni(II) (2) in three steps to an aldimine linkage. The conformational changes of the porphyrinic macrocycle during the course of this degradation, as determined by comparison of the X-ray crystal structures of the compounds, are discussed. A comparative study delineates the UV–Vis spectroscopical consequences. In addition, the chemical reactivity of [meso-tetraphenylchlorophinato]Ni(II) (6) suggests the existence of an azepine-derived pyrrole-modified porphyrins (11, 12).

Graphical abstractThe step-wise deformylation of [2,3-diformylsecochlorinato]Ni(II) to [chlorophinato]Ni(II) is described. A comparative analysis of the conformation, as determined by single crystal crystallography, and the UV–Vis spectra of these and related chromophores details the conformational and electronic effects that the degradation of the porphyrinic framework structure entail.Figure optionsDownload full-size imageDownload as PowerPoint slide