Molecular modeling and spectroscopic investigation of a neurotransmitter: Epinephrine

The investigation of possible number of conformational structures of gas phase epinephrine molecule has been performed using tedious potential energy scanning with respect to different dihedrals. All the theoretical computations were carried through first principles Density Functional Theory (DFT) method. While calculating optimized geometrical parameters and vibrational frequencies the 6-31++G(d, p) was consumed as a standard basis set. The FTIR and FTRaman spectra for epinephrine molecules were also recorded in the spectral region 400-4000 cm^-1 and 50-4000 cm^-1 respectively and correlated with the theoretical spectra of most preferred structure of epinephrine. The potential energy distribution was also computed using the normal coordinate analysis method to understand the vibrational dynamics of the epinephrine. The neutral bond orbital (NBO) analysis was performed for epinephrine and epinephrine hydrochloride to check out the stabilization of predicted electronic structures. The investigation regarding the strength and effect of N⋯H hydrogen bond in hydrochloride was also performed. The HOMO-LUMO energy gap was calculated to predict the chemical reactivity of molecule.