The Low Lying Electronic States of Dichloromaleic Anhydride

Abstract The polarized Raman and infrared spectra of dichloromaleic anhydride were studied and the assignments of the normal vibrations were reinvestigated based on the polarization behaviors of the spectral bands and on the normal coordinate calculation. Using the assignments the vibrational structure of the phosphorescence spectrum was analyzed and the phosphorescence lifetime was also measured. These results indicate that the lowest triplet state of this molecule is a 3(π, π*) state perturbed by closely located 3(n, π*) states. The near ultraviolet absorption and phosphorescence excitation spectra were measured and four absorption bands due to 3(n, π*)←1A1, 1A2(n, π*)←1A1, 1B1(n, π*)←1A1, and 1A1(π, π*)←1A1 transitions were found. The polarization experiment made on the 1A2(n, π*)←1A1 absorption suggests that this transition borrows the intensity from the 1A1(π, π*)←1A1 transition.