Synthesis, characterization, structures and antioxidant activity of nicotinoyl based organoselenium compounds

A series of nicotinoyl based organoselenium compounds, [2-NC5H3(3-COOH)Se]2 (1), [2-NC5H3(3-CO)Se–Se] (2), [2-NC5H3(3-CONH2)Se]2 (3), [2-NC5H3(3-CONHPh)Se]2 (4), [2-NC5H3(3-CONHpyrimidine)Se]2 (5), [2-NC5H3(3-CONHPh)SeBr] (6) and [2-NC5H3(3-CONHPh)SeI] (7) have been synthesized and characterized by absorption, IR, NMR (1H, 13C{1H}, 77Se{1H}) and mass spectrometry. The crystal structures of [2-NC5H3(3-CO)Se–Se] (2) and [2-NC5H3(3-CONHPh)Se]2 (4) have been determined. The structure of (4) revealed the existence of two intra-molecular Se⋯X (X = O and N) interactions, as a result of this, C–Se–Se–C torsion angle is unusually large (180°). The GPx mimicking activity of these compounds has been evaluated using methods based on 1H NMR spectroscopy and HPLC. Free radical scavenging ability of the compounds was examined by DPPH and deoxyribose assay. All these studies indicated that the compound (3) not only showed highest GPx activity but also has a very good free radical scavenging ability thus making it a novel structure for development of nicotine based antioxidants.