Formation, Chemical Structure, and Spectral Properties in the Ground and Excited States of Manganese(III) Porphyrin Complexes with Imidazole Derivatives

Abstract Manganese(III)porphyrins exhibit high axial coordination ability, which is widely used in the development of electron-optical materials and catalysts based on them. The axial coordination of imidazole, 4-(1H-imidazol-1-yl)benzaldehyde, and 1-N-methyl-2-(1H-imidazol-1-yl)-phenyl-3,4-fullero[60]pyrrolidine by (2,3,7,8,12,13,17,18-octaethylporphinato)chloromanganese(III) ((Cl)MnOEP) was studied in this work. The formation of complexes with stoichiometry 1 : 2 (for imidazole) and 1 : 1 (for imidazole derivatives) is established and their stability constants in toluene were determined to be (2.0 ± 0.4) × 104 L2/mol2 and 69.1 ± 8.3 L/mol, (2.2 ± 0.3) × 103 L/mol, respectively. The chemical structure of the complexes is confirmed using UV–vis and IR spectroscopy and MALDI-TOF mass spectrometry. The dynamics of processes in photoexcited complexes was studied by femtosecond transient absorption spectroscopy. The lifetimes of (Cl)MnOEP exited states were determined and the effect of axial complexation on the dynamics of their relaxation was shown. The obtained results are an important step towards the development of new functional materials for optoelectronics.