POLARIZED VACUUM ULTRAVIOLET SPECTRA OF CRYSTALLINE GLYCOLURIL - A UREA DIMERLIKE MOLECULE

摘要

Polarized ultraviolet reflection spectra of the a, b, and c crystal axes from the (010) and (100) faces of single crystals of glycoluril have been measured between 370 and 140 nm. Corresponding absorption spectra are obtained through Kramers-Kronig analysis of the reflection data. Four transitions are observed for the C-2v molecule as follows: transition I at 54 500 cm(-1), (183 nm), f=0.26, B-2 symmetry; II at 60 300 cm(-1) (166 nm), f=0.49, B-1 symmetry; IV at 64 300 cm(-1) (156 MI), f=similar to 0.12, Al symmetry; III at 66 100 cm(-1) (151 nm), f=similar to 0.24, B-2 symmetry. These assignments are in close agreement with the results of an Independent Systems calculation in which glycoluril is treated as a urea dimer-like molecule, and the previous assignments for urea by Campbell and Clark (J. Am. Chem. Sec. 1989, 111, 8131) are assumed. The results of calculations using the method of intermediate neglect of differential overlap configuration interaction (INDO/S-CI) and employing a modified parameterization are in satisfactory agreement with the experimental energies, oscillator strengths, and excited state symmetries for both urea and glycoluril. [References: 26]