Spectral and theoretical studies on the molecular complexes of azacyclonol with new π-acceptors, alkoxysubstituted 1,4-benzoquinones

The molecular complexes of a series of new electron acceptors, 1,4-benzoquinones possessing variety of alkoxy substituents, with azacyclonol have been investigated using various spectral techniques such as UV–Vis, 1H NMR, FT-IR, fluorescence and LC–MS. The stoichiometry of the complexes was determined by Job’s continuous variation method and was found to be 1:1, in all the cases. The results of equilibrium, and kinetic studies were well supported by ab initio DFT calculations. Correlation of formation constants of the complexes with Taft’s polar and steric constants indicated that both these factors play significant role in governing the reactivity. Also, the results indicated that an increase in electron releasing property of the alkoxy group makes these acceptors increasingly weaker while an increase in steric property of the substituent decreased the formation constant.