DFT Structural Analysis of Chamazulene

Abstract

A combined theoretical and experimental study on the structure, infrared, UV-Vis, 1H and 13C NMR data of chamazulene is presented. Theoretical geometry optimizations and some additional properties of chamazulene and their IR, UV-Vis, NMR spectra were calculated using the DFT B3LYP/6-31G(d) level. Calculations were done using software Spartan 10. Experimental data showed that chamazulene have absorption maximum at 340 nm to 530 nm. The position of max did not much differ from the theoretically calculated value. The calculated density of states showed excellent agreement with UV/Vis diffuse reflectance spectra predicting the absorption maximum at 310 nm (calculated 332 nm) to 530 nm (calculated 516 nm). The IR normal modes were assigned for the two very small sp2 CH valence bands and strong sp3 CH vibrations. The aromatic overtone vibrations can hardly be detected and also the C=C vibration is very weak. 1H NMR spectroscopy, showed resonances of the ring protons between 7 and 8 ppm. The methyl groups and the methylene group appear rather deshielded at 2.7 and 2.9 ppm. The calculations yielded reliable results that were in good correlation with experimental data. This study is a good basis for collaboration between experimentalists and quantum chemists.