Redox potentials of puckered 1,4-benzoquinone

The present study explores the conformational dependence of the redox potentials of 1,4-benzoquinone (1,4-BQ) molecule employing density functional theory (DFT). The basic 38 conformers of 1,4-BQ (2 chairs, 6 boats, 6 skew-boats, 12 half-chairs, 12 envelopes) were extracted following the IUPAC nomenclature by Berces et al. and were optimized at B3LYP/6-31+G(d), M06-2X/6-31+G(d) and wB97X-D/6-31+G(d) levels of theory. The quantitative analysis was made using the spherical polar coordinates (d, θ, and ϕ) and structural parameters. The electrochemical performance is explored through the calculation of free energies and redox potentials using conductor-like polarizable continuum model (C-PCM). A good correlation is found between the conformers with more negative lowest unoccupied molecular orbital (LUMO) energies and their redox potentials. The results put emphasis on the variation of redox potential with respect to conformational change of 1,4-BQ molecule and the importance of using B3LYP functional along with the ethylene carbonate solvent for effective electrochemical performance. Graphical abstract The present study highlights the conformational dependence of structure and redox potentials of 1,4-benzoquinone molecule using quantum chemical techniques. It was observed that the planar molecule obtained the highest redox potential followed by skew 2 S 6 , 6 S 2 and boat 3,6 B, B 3,6 , B 2,5 conformers that have more negative LUMO energies. Further, it was noted that the redox potentials of 1,4-BQ conformers are more effectively predicted at the B3LYP/6-31+G* level of theory employing ethylene carbonate solvent.