title: Anharmonic vibrational analysis of 3,4-diaminopyridine and 3-aminopyridine by density functional theory calculations.
abstract: In this work, we will report a combined experimental and theoretical study on molecular structure and vibrational analysis of 3,4-diaminopyridine (3,4-DAP) and 3-aminopyridine (3-AP). The Fourier transform infrared and Fourier transform Raman spectra of 3,4-DAP were recorded in the solid phase. The molecular geometry, harmonic vibrational wavenumbers of 3-AP and 3,4-DAP in the ground-state have been calculated by using MP2 and density functional methods (B3LYP) using 6-311++G(d,p) as basis set. Predicted electronic absorption spectra 3,4-DAP from TD-DFT calculation have been analyzed comparing with the experimental UV-vis spectrum. The calculated HOMO and LUMO energies show that charge transfer occur in the molecule. A detailed interpretation of the infrared spectra of 3-AP and 3,4-DAP is reported. The theoretical spectrograms for FTIR and FT-Raman spectra of the title molecules have also been constructed. Comparison of the experimental spectra with anharmonic vibrational wavenumbers indicates that B3LYP results are more accurate.
authors.affiliation: Department of Physics (Engg), Annamalai University, Annamalai Nagar 608 002, India.
authors.forename: J
authors.initials: J
authors.lastname: Karpagam
authors.forename: N
authors.initials: N
authors.lastname: Sundaraganesan
authors.forename: S
authors.initials: S
authors.lastname: Kalaichelvan
authors.forename: S
authors.initials: S
authors.lastname: Sebastian
mesh_terms: D015761:4-Aminopyridine / Q000031:analogs & derivatives* / Q000737:chemistry; D000077770:Amifampridine; D000631:Aminopyridines / Q000737:chemistry*; D008958:Models, Molecular; D008962:Models, Theoretical; D015394:Molecular Structure; D026902:Potassium Channel Blockers / Q000737:chemistry; D011789:Quantum Theory; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013059:Spectrum Analysis, Raman / Q000379:methods; D013816:Thermodynamics; D014732:Vibration
chemical_list: D000631:Aminopyridines; D026902:Potassium Channel Blockers; C031283:3-aminopyridine; D015761:4-Aminopyridine; D000077770:Amifampridine