Spectroscopic Properties and Ligand Field Analysis of trans -Dibromo(2,2-dimethyl-1,3-diaminopropane)chromium(III) Moiety

The sharp-line absorption and emission spectra of(H 1 3 O 6 ){trans-[Cr(Me 2 tn) 2 Br 2 ]} 2 Br 2 (Cl0 4 ) (Me 2 tn = 2,2-dimethyl-l,3-diaminopropane) have been measured between 13000 cm - 1 and 16000 cm - 1 at 5 K. The 298 K infrared and visible absorption spectra have also been measured. The nine electronic bands due to spin-allowed and spin-forbidden transitions were assigned. Using observed transitions, a ligand field analysis has been performed to probe the ligand field properties of coordinated atoms in the title chromium(III) complex ion. The zero-phonon line in the sharp-line absorption spectrum splits into two components by 286 cm - 1 , and the large ""Eg splitting can be reproduced by the modern ligand field theory. It is confirmed that nitrogen atoms of the Me 2 tn ligand have a strong cr-donor character, but the bromide has weak σ- and π-donor properties toward chromium(III) ion.