Synthesis, Characterization, and Electrochemistry of the Manganese(I) Complexes of meso-Substituted [14]Tribenzotriphyrins(2.1.1)

Metalation of 6,13,20,21-tetraaryl-22H-[14]tribenzotriphyrins(2.1.1) (TriP, 1 a–d) with [Mn(CO)5Br] provided MnI tricarbonyl complexes of [14]tribenzotriphyrins(2.1.1) 2 a–d in 85–93 % yield. The complexes were characterized by mass spectrometry and UV/Vis absorption, IR, and NMR spectroscopy. Single-crystal X-ray analyses revealed that 2 b and 2 c adopt bowl-shaped conformations. The redox properties of [(TriP)MnI(CO)3] (2 a–d) were studied by cyclic voltammetry. Each compound undergoes two reversible one-electron reductions to form a porphyrin π anion radical and a dianion in CH2Cl2. Two oxidation waves were observed, the first of which corresponds to a metal-centered electron-transfer process. The redox potentials of 2 a–d are consistent with the optical spectroscopic data and the relatively narrow HOMO–LUMO gaps that were predicted in DFT calculations. The optical spectra can be assigned by using Michl’s perimeter model. TDDFT calculations predict the presence of several metal-to-ligand charge-transfer bands in the L-band region between 500 and 700 nm.