Host–guest interaction between new nitrooxoisoaporphine and β-cyclodextrins: Synthesis, electrochemical, electron spin resonance and molecular modeling studies

A new nitrooxoisoaporphine derivative was synthetized and characterized by cyclic voltammetry and electron spin resonance. Its aqueous solubility was improved by complexes formation with β-cyclodextrin, heptakis(2,6-di-O-methyl)-β-cyclodextrin and (2-hydroxypropyl)-β-cyclodextrin. In order to assess the inclusion degree reached by nitrooxoisoaporphine in cyclodextris cavity, the stability constants of formation of the complexes were determined by phase-solubility measurements obtaining in all cases a type-AL diagram. Moreover, electrochemical studies were carried out, where the observed change in the EPC value indicated a lower feasibility of the nitro group reduction. Additionally, a detailed spatial configuration is proposed for inclusion of derivate within the cyclodextrins cavity by 2D NMR techniques. Finally, these results are further interpreted by means of molecular modeling studies. Thus, theoretical results are in complete agreement with the experimental data.

The inclusion complexes of new nitrooxoisoaporphine with β-cyclodextrin, hydroxypropyl-β-cyclodextrin and dimethyl-β-cyclodextrin, have been investigated using cyclic voltammetry, 1H NMR, 2D NMR, ESR and molecular modeling studies.Figure optionsDownload as PowerPoint slideHighlights
► A new nitrooxoisoaporphine derivative was synthesized.
► Electrochemical mechanisms were elucidated by cyclic voltammetry.
► Hyperfine splitting patterns were established by ESR spectroscopy.
► Nitrooxoisoaporphine-β-cyclodextrin inclusion complex was formed.
► Inclusion geometries were revealed by 2D-NMR and molecular modeling.