Donor Substituted Pyrazabole Monomers and Dimers: Design, Synthesis and Properties

Abstract

We report the design and synthesis of ferrocene and triphenylamine substituted D–π– A–π–D and D–π–A–π–A–π–D type of symmetrical pyrazabole monomers (3 and 5) and dimers (6 and 7). Their optical, thermal, electrochemical and computational properties were investigated. The electronic absorption spectra of pyrazaboles 3−7 exhibit absorption bands in UV region. The TGA study reveals that pyrazaboles 3−7 show good thermal stability and pyrazabole monomers are thermally more stable as compared to pyrazabole dimers. The electrochemical studies show that pyrazaboles 3−7 exhibits one reversible oxidation and two reduction waves. The theoretical investigation shows that the triphenylamine substituted pyrazaboles (5 and 7) exhibit low HOMO − LUMO gap values compared to ferrocenyl pyrazaboles (3 and 6).