Reaction of Bi(NO3)3 with quinoxaline in the presence of HI. Synthesis of 5,6,7,8-tetranitro-1,2,3,4-tetrahydroquinoxaline-2,3-diol by serendipity: Crystal structure, Hirshfeld and optical study of a novel energetic compound
Résumé
Treatment of an acetone solution of Bi(NO3)3 with quinoxaline (Qx) in the presence of hydroiodic acid produces in moderate yield the crystallographically characterized 1D-polymeric salt-like iodobismutate [(Qx-H+)BiI4]n (1), whose negative charge is balanced by mono-protonated quinoxalinium counterions. The main product is an unusual tetra(nitrated) quinoxaline derivative, namely 5,6,7,8-tetranitro-1,2,3,4-tetrahydroquinoxaline-2,3-diol (2), which was formed accidently under mild reaction conditions. The molecular structure of this organic compound 2 was determined by single-crystal X-ray diffraction and its strong intermolecular interactions giving rise to a supramolecular three-dimensional network were assessed by IR spectroscopy and a Hirshfeld surface analysis. Structural analysis reveals that the crystal structure is supported essentially by O‒H···O and N‒H···O intermolecular hydrogen bonds and additionally stabilized by N‒O···π interactions. The ground-state molecular structure of this novel organic heterocycle has been optimized by DFT calculation. The optical band gap, caused by intramolecular charge transfer (ICT) from the 1,2,3,4-tetrahydroquinoxaline-2,3-diol fragment to the nitro groups, has been estimated to be 2.04 eV. High density, positive heat of formation and very good thermal stability according to thermal analysis by TGA, DTA and DSC characterize tetranitro compound 2 as energetic material.