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 (H13O6) {trans-[Cr(Me(2)tn)(2)Br-2])(2)Br-2(ClO4) (Me(2)tn = 2,2dimethyl-1,3-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 E-2(g) splitting can be reproduced by the modem ligand field theory. It is confirmed that nitrogen atoms of the Me(2)tn ligand have a strong sigma-donor character, but the bromide has weak sigma- and pi-donor properties toward chromium(III) ion.