Dimerization of 1,8-Diaminonaphthalene. DFT Theoretical, Ifra-red, raman and Inelastic Neutron Scattering Studies

Infra-red (IR), Raman (R) and inelastic neutron scattering (INS) studies were performed on solid 1,8-diaminonaphthalene. Calculations by using HF and DFT methods showed that very good reproduction of the dimeric structure found in the solid state yields the DFT method on the B3LYP/6-31G** level. The characteristic motif of dimers is an eight-membered ring with two intramolecular (highly bent) and two intermolecular N-H___Nhydrogen bridges. The four outer N-H groups remain non-bonded. This leads to a complicated pattern of vibrational spectra. No agreement between calculated and experimental (IR, R) spectra in the range of (NH2) vibrations was found.Arelatively good coincidence of experimental and theoretically predicted spectra is observed in the middle and low frequency regions, especially when analysing the INS spectra for dimeric species. The dimerization leads to a marked change in modes connected with torsional vibrations of NH2 groups.