Synthesis and characterization of dicationic 4,4′-bipyridinium dichloride ordered mesoporous silica nanocomposite and its application in the preparation of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives

Abstract

The sol–gel method was used for the synthesis of a dicationic 4,4′-bipyridine silica hybrid nanocomposite. In order to introduce 4,4′-bipyridine into the skeleton framework of an ordered mesoporous silica (SBA-15), first, the N,N′-bis(triethoxysilylpropyl)-4,4′-bipyridinium dichloride precursor was synthesized by the reaction of 3-chloropropyltriethoxysilane with 4,4′-bipyridine to give (TEOS)₂BiPy²⁺ 2Cl⁻. The organic–inorganic hybrid nanocomposite, SBA@BiPy²⁺ 2Cl⁻, was then synthesized by the hydrolysis and polycondensation of the precursor and tetraethyl orthosilicate under mild acidic conditions. The nanocomposite was characterized by FT-IR spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET). The characteristic results of FT-IR, XRD and TGA confirmed the coexistence of silica and 4,4′-bipyridinium dichloride networks. The catalytic ability of SBA@BiPy²⁺ 2Cl⁻ as a novel environmentally safe heterogeneous nanoreactor for the preparation of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives via a one-pot multicomponent method under solvent-free conditions has been described. The catalyst can be reused without an obvious loss of catalytic activity.