Spectroscopic studies (FTIR, FT-Raman and UV–Visible), normal coordinate analysis, NBO analysis, first order hyper polarizability, HOMO and LUMO analysis of (1R)-N-(Prop-2-yn-1-yl)-2,3-dihydro-1H-inden-1-amine molecule by ab initio HF and density function

•FT-IR and FT-Raman spectra of 1RNDPA in solid phase were recorded and analyzed.•The vibrational wave numbers were computed using B3LYP and HF methods.•The vibrational assignment and spectroscopic analysis have been carried out.•The HOMO, LUMO energy gap were theoretically predicted.•The NBO analysis explained the intramolecular hydrogen bonding.

The Fourier transform infrared (FT-IR) and FT-Raman of (1R)-N-(Prop-2-yn-1-yl)-2,3-dihydro-1H-inden-1-amine (1RNPDA) were recorded in the regions 4000–400 cm−1 and 4000–100 cm−1 respectively. A complete assignment and analysis of the fundamental vibrational modes of the molecule were carried out. The observed fundamental modes have been compared with the harmonic vibrational frequencies computed using HF method by employing 6-31G(d,p) basis set and DFT(B3LYP) method by employing 6-31G(d,p) basis set. The vibrational studies were interpreted in terms of Potential Energy Distribution (PED). The complete vibrational frequency assignments were made by Normal Co-ordinate Analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). The first order hyper polarizability (β0) of this molecular system and related properties (α, μ, and Δα) are calculated using B3LYP/6-31G(d,p) method based on the finite-field approach. The thermodynamic functions of the title compound were also performed at the above methods and basis set. A detailed interpretation of the infrared and Raman spectra of 1RNPDA is reported. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated using the GIAO method confirms with the experimental values. Stability of the molecule arising from hyper-conjugative interactions and charge delocalization has been analyzed using Natural Bond Orbital (NBO) analysis. UV–vis spectrum of the compound was recorded and electronic properties such as excitation energies, oscillator strength and wavelength were performed by TD-DFT/B3LYP using 6-31G(d,p) basis set. The HOMO and LUMO energy gap reveals that the energy gap reflects the chemical activity of the molecule. The observed and calculated wave numbers are formed to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically constructed spectra.

Graphical abstract1RNPDA is used for the treatment is an irreversible inhibitor of mono amine oxidize. It is used as a mono-therapy in early Parkinson’s disease or as an adjunct therapy in more advanced cases. It is chemically called as (1R)-N-(Prop-2-yn-1-yl)-2, 3-dihydro 1H-inden-1-amine. An extensive work has been carried out on the title compound and its derivatives in recent year. At present, vibrational spectroscopy is used not only for the functional group identification of organic compounds, but also to investigate the molecular conformation, reaction kinetics.Figure optionsDownload full-size imageDownload as PowerPoint slide