DFT simulations and vibrational analysis of FT-IR and FT-Raman spectra of 2,4-diamino-6-hydroxypyrimidine

Quantum mechanical calculations of energies, geometries and vibrational wavenumbers of 2,4-diamino-6-hydroxypyrimidine (2,4DA6HP) were carried out by using ab initio HF and density functional theory (DFT/B3LYP) method using 6-311G(d,p) basis set. The optimized geometrical parameters obtained by B3LYP method show good agreement with experimental X-ray data. The best level of theory in order to reproduce the experimental wavenumbers is B3LYP method with the 6-311G(d,p) basis set. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. A detailed interpretation of the infrared spectra of 2,4DA6HP was also reported. The calculated HOMO and LUMO energies show that charge transfer occurs in the molecule. The entropy of the title compound is also performed at HF/6-311G(d,p) and B3LYP/6-311G(d,p) levels of theory. The theoretical spectrograms for FT-IR and FT-Raman spectra of the title molecule have been constructed.