[Studies on infrared and UV-vis spectra of azametallacrown complexes containing Mn(III), Fe(III) or Co(III)].

IR and UV-vis spectral properties of azametallacrown complexes containing Mn(III), Fe(III) or Co(III) were investigated. The relation between the main IR bands in 400-4,000 cm-1 and the structure of azametallacrown complexes were discussed. The absorption bands of nu(C=O), nu(NH), delta(NH) + nu(CN) and delta(NH) which existed in the IR spectra of the ligands disappeared in the IR spectra of the complexes. A strong band found at--1,600 cm-1 is assigned to [symbol: see text]C=N-N=C[symbol: see text] group. Bands at approximately 1,560 cm-1 and -1,410 cm-1 are attributed to nu(C=N) and nu(CO), respectively. These results suggest that the ligands in solid state may exit as keto form, and the ligands in the solution may first undergo isomerization to enol form and then coordinated to metal centers through deprotonation. The bands found at -204 and 220-256 nm can be assigned to pi-pi* or pi-pi* transitions of the pi conjugation in [symbol: see text]C=N-N=C[symbol: see text] framework and benzene ring. The absorption maxima at 274-350 nm could be assigned to metal-toligand charge transfer (MLCT) transition. The d-d transition band for the metal atoms was observed at -500 nm.