The electronic energies among different possible structures of 4-hydroxyacetanilide (paracetamol) (PA) molecule, were calculated using INDO
method and it has been concluded that its structure has Cs point group symmetry of the cis-form. The ionization potential, electron affinity, dipole
moment and binding energy have been calculated. The calculated electronic transitions of the cis-form of PA using SCF-CI method have good
coincidence with the electronic absorption spectrum.
The temperature effect on the electronic spectrum of PA confirms the presence of one conformer only. The electronic spectra of PA compound
were studied in different polar- and non-polar solvents and the hydrogen bonding as well as the orientation energies of the polar solvents were
determined from the mixed solvents studies.
Complexes of PA with various metal ions such as, Cu(II), Zn(II) or Fe(II) ions of ratio 2:1, respectively, have been prepared and their structure
has been confirmed by elemental analysis, atomic absorption spectra, IR spectra and 1H NMR spectra and finally it can be concluded that the
structure of the complexes has C2h point group symmetry in which two PA molecules are chelated to any one of the metal ions, Cu(II), Zn(II) and
Fe(II) ions.