A one-pot
synthesis of cobalt(II) complexes of 5,10,15,20-tetraaryl-5,15-diazaporphyrins
(CoTADAPs) from the corresponding 5-aryl-1-arylamino-9-chlorodipyrrins
and cobalt(II) acetate is reported. The CoTADAPs exhibited characteristic
electrochemical behavior and catalyzed the intramolecular cyclization
of N-benzyl-N-Boc-3-diazopropan-1-amines,
probably via σ-CoIII–alkyl radical intermediates.
1,2,5,10-Tetraphenylanthra[2,3-b]phosphole
oxides
and 1-methyl-1,2,5,10-tetraphenylanthra[2,3-b]phospholium
salts were prepared, and their optical properties were investigated.
The substituent at the para position and the fused
anthracene moiety were found to exert significant impacts on the fluorescence
properties of the P-bridged 2-styrylanthracene skeleton.
Photophysical and photochemical properties of 1-methyl-1,2-diphenylbenzo[b]phospholium iodide (diPh-I) and 1-methyl-1,2,3-triphenylbenzo[b]phospholium iodide (triPh-I) were investigated by obtaining time-resolved fluorescence and the transient absorption spectra with sub-picosecond time-resolution. Unusually, fluorescence lifetimes of the triphenyl-substituted compound in various solvents were approximately 100 ps, which is several times shorter than the lifetime of diPh-I. Quantum chemical calculations suggest that the excited-state planarization of the dihedral angle between the benzo[b]phospholium backbone and the phenyl group at Cα possibly contributes to the non-radiative relaxation of triPh-I. In the case of diPh-I, the fluorescence excitation spectrum obtained in dichloromethane depended on the concentration, suggesting that diPh-I forms molecular aggregates in the ground state. The transient absorption spectra of diPh-I showed that, at various concentrations of dichloromethane, the dissociation dynamics of aggregation to produce the monomeric form in the excited state occurred over several picoseconds.
The fundamental properties of azaporphyrins can be modulated over a wide range by changing the number of meso‐nitrogen atoms. We report herein the first examples of 5,10,15,20‐tetraaryl‐5‐azaporphyrinium (MTAMAP) salts, which were prepared via metal‐templated cyclization of the corresponding zinc(II) and copper(II) complexes of 10‐aryl‐1‐chloro‐19‐benzoyl‐5,15‐dimesityl‐10‐azabiladiene‐ac. The inclusion of one meso‐nitrogen atom in the 5,10,15,20‐tetraarylporphyrin skeleton considerably changes the redox and optical properties as well as the degree of aromaticity of the porphyrin ring. The present findings suggest that MTAMAP salts would be promising scaffolds for the development of new azaporphyrin‐based ionic fluorophores and photosensitizers.
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