Chemical Structure of Pyridine Complexes Of Oxo(5,10,15,20-Tetraphenyl-21H,23H-Porphinato) Niobium(V) Chloride According to Formation Thermodynamics/Kinetics And Spectroscopy Data

Abstract

The equilibrium and the rate of stepwise reactions in the course of pyridine (Py) coordination by oxo(5,10,15,20-tetraphenylporphinato)niobium(V) chloride ((Cl)О=NbTPP) in toluene and the chemical structure of reaction products are studied using time-dependent titration, chemical kinetics, UV/Vis, IR, ¹H NMR, and mass spectrometry methods. The interaction with Py is a complex system of simple, fast, reversible reactions of pyridine coordination (K₁ = 2.2.10⁵ l²/mol², K² = 5.2 l/mol) with subsequent nonreversible displacement of chloride ions into the second coordination sphere and cis–trans isomerization of axial ligands. A complete quantitative description of the interaction is obtained and spectral parameters were determined for intermediate and final products. Based on these data, the chemical structure of the latter is determined. The prospect of using (Cl)₃NbTPP as a receptor for nitrogenous bases, the “building blocks” of pharmaceuticals and food components, as well as environmental pollutants, is substantiated. The obtained results are useful for the design of dye-sensitized solar cells (DSSCs), since the above reaction is a model of the self-assembly process of dipolar systems based on metalloporphyrins and pyridyl derivatives of carbon nanoforms.