Master Thesis: Linear Dichroism Spectroscopic and Theoretical Investigations of the compound Emodin (ncson)

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Master Thesis: Linear Dichroism Spectroscopic and Theoretical Investigations of the compound Emodin

Author: Nguyen Chi Son
Roskilde University, Denmark
Issue date: 2004

Abstract: The LD UV-VIS spectra of Emodin (1,3,8-trihydroxy-6-methyl anthraquinone) in stretched PE and PVA have been recorded and analysed. Orientation factor of the observed electronic transition were determined through stepwise reduction. The electronic transition moment direction of observed transition is determined by the assumption of molecule has Cs symmetry. The observed electronic transition moment directions belong to the “long” and “short” molecular symmetry axes. This information leads to the conclusion that Emodin still remembers the exited states of parent molecule, Chrysazin. When changing from PE solvent to PVA solvent, almost electronic transitions have small red shift by 200 – 500 cm-1, except a strong band at 44500 cm-1 don’t move anymore, the electronic transition moment directions of observed transitions still remain.

The LD UV-VIS spectra of Emodin anion in stretched PVA also have been recorded and analysed. The electronic transitions of anion are completely different the electronic transitions of neutral molecule because of redistribution of negative charge. The observed electronic transition moment directions do not belong to the “long” and “short” molecular symmetry axes.

The TD-DFT calculation, B3LYP/6-31G+(d,p)//B3LYP/6-31G(d,p), has a good agreement to the assignment of observed transitions in both transitions and its moment directions.

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