The benzoquinone-hydrobenzoquinone complex (quinhydrone) is a DA-type CT-complex which exist as one-dimensional hydrogen bonded networks. Vibrational spectra suggest that in this complex, a proton and an electron are cooperatively transferred (PET) to give semiquinone radicals under conditions of high pressure.
To better understand this PET type phase transition at the molecular level, we have undertaken ab-initio molecular orbital calculations of this system using the UHF/3-2lG* basis set. Semi qualitative basic properties, such as optimized molecular geometries, electronic structures, and molecular energies were calculated for relevant quinone related model species (hydroquinone, quinone, hydroquinone cation radical, quinone anion radical, semiquinone anion, semiquinone cation, semiquinone radical, semiquinone dimer, hydrogen bonded hydroquinone-quinone complex, etc.).