Intermolecular hydrogen bonds between 1,4-benzoquinones and HF molecule: Synergetic effects, reduction potentials and...

Some biological activities of quinones can be attributed to the H-bonding ability of acceptor oxygen atoms. According to the results obtained from the quantum mechanical calculations performed on a wide variety of complexes between the 1,4-benzoquinone (BQ) derivatives and HF molecules, the interplay between H-bonds and individual H-bond interaction energies (E_HB) can be affected by the substituents placed on the six-membered ring of BQ. The total binding energies of complexes become more negative by the electron donating substituents (EDSs) while the changes are reversed by the electron withdrawing substituents (EWSs). The mutual interplay between the X-BQ⋯(HF)_n (n=1-3) interactions has been investigated using the geometrical parameters, synergetic energies (SE) and the E_HB values. Hydrogen bonding decreases the reduction potentials (E⁰_red) and increases the electron affinities (EA) of X-BQ derivatives. Linear relationships have been observed between the E⁰_red (and EA) values and the Hammett constants of substituents.