Electrochemical and Computational Interpretations of Hydrogen-bonding of Naphthoquinones with Methanol

Cyclic Voltammetry technique was used to study the hydrogen bonding of MeOH with electroreduced naphthoquinones. The positive shift in both reduction waves of the compounds was investigated with the continuous increase in MeOH concentration. From the observed shifts, equilibrium constants and number of MeOH molecules bonded to anion and dianion of the naphthoquinone were calculated. The quinone-MeOH interactions were resolved as hydrogen bonding. Following the calculations substituent and solvent effects were addressed. To support experimental results computational studies were also carried out. The theoretical results obtained from CNDO/CI method rationalized and logically explained the observed positive shift in the peaks. Three types of computations were made (i) Theoretical U V spectral studies for the neutral, anion, dianion and their hydrogen bonded complexes, (ii) Geometries of neutral, anion, dianion and the corresponding hydrogen bonded complexes with MeOH. (iii) Charge transfer study so as to know about the transfer of charges during the formation of these complexes.