Synthesis and characterization of molecular complexes of cimetidine with water soluble 1,4-benzoquinones

• This is the first attempt on the study of CT complexes of cimetidine with water soluble 1,4-benzoquinones.
• 1,4-benzoquinones possessing different alkoxy substituents, are used as electron acceptors.
• Correlation obtained between formation constants of the CT complexes with Taft’s polar and steric constants.

The molecular complexes of novel water soluble 1,4-benzoquinones possessing different alkoxy substituents, with cimetidine drug have been investigated using various spectral techniques such as UV–Vis, 1H NMR, FT-IR. The stoichiometry of the CT complexes was found to be 1:1, in all the cases. The Density Functional Theory calculations supported the experimental observations. Correlation of formation constants (K) of the CT complexes with Taft’s polar (σ⁎) and steric (Es) constants 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.