Vibrational spectra, conformation and molecular transport of 5-amino-2,2,6,6-tetramethyl-4-hepten-3-one

In this research, the molecular structure and intramolecular hydrogen bonding (IHB) of 5-amino-2,2,6,6-tetramethyl-4-hepten-3-one (AMTMH) were studied using spectroscopic techniques (IR, Raman, UV, and NMR) and computational analysis (density functional theory (DFT) and the second-order Møller–Plesset (MP2) methods). The results of this study compared with those of 4-amino-3-penten-2-one (APO) and 3-methyl-4-amino-3-penten-2-one (3-MeAPO). The averaged calculated geometrical parameters of AMTMH (obtained by considering the populations of all conformers) agree with the averaged geometrical parameters obtained by X-ray crystallography of two conformations found in the crystal. Comparison of different parameters related to the IHB strength, such as NH stretching, experimental proton chemical shift, and deuterium isotope effects on 13C chemical shifts of AMTMH with those of APO and 3-MeAPO, suggests the following trend for the IHB strength: 3-MeAPO > AMTMH > APO. All normal modes of AMTMH were successfully assigned and compared to the corresponding band frequencies of APO. The appearance of more than one band for several vibrational normal modes is related to the coexistence of different conformers in the sample. The molecular transport results show that the conductivity of the enol form (on-state) to keto form (off-state) changes, which suggests that this system has the potential to function as a molecular switch. In addition, the experimental fluorescence and the calculated TD-DFT results confirmed both aminoketone and iminoenol forms are in the excited state.