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

Chemical thermodynamics and UV, visible, IR, H-1 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 K-1 of (4.7 +/- 1.1) x 10(2) 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)(3)P]Cl-+(-)) with constant K-2 = (0.10 +/- 0.03) L-2/mol(2). 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.