Stepwise Mechanism of the Rhenium(V) Porphyrin Reaction with Pyridine, and the Chemical Structure of the Donor–Acceptor Complex

Abstract

Chemical thermodynamics and UV, visible, IR, 1H NMR, and mass spectrometry are used to study the complex reaction of (5,15-bis(4'-methoxyphenyl)-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphinato) (oxo)(chloro)rhenium(V) (O=Re(Cl)P) with pyridine (Py) and the chemical structure of the product. The nature and stoichiometry of the reaction are established and the quantitative parameters of two-way stepwise reactions are determined during a complex reaction. There is reversible replacement of Cl– ions by pyridine molecules with constant K1 of (4.7 ± 1.1) × 102 L/mol and the formation of cationic complex compound [O=Re(Py)P]+Cl– in the first stage. The second stage is the reversible addition of two pyridine molecules ([O=Re(Py)3P]+Cl–) with constant K2 = (0.10 ± 0.03) L2/mol2. The reaction studied is a model for processes in self-assembling systems based on metalloporphyrins and pyridyl derivatives of carbon nanoforms for the formation of active layers with photoinduced charge separation in hybrid solar cells.