Synthesis, X-ray structure analysis and density functional study of an unusual anhydrous 5,6-dimethylbenzo-1,3-imidazolium(H3) chloride

The heteroaromatic base 5,6-dimethylbenzo-1,3-imidazole (DMBI) proved to be a Brönsted base in an anhydrous ethanol solution, which contained fac,trans-[Ru(CO)3Cl2]2 at 55 C in air when the DMBI:Ru molar ratio was 2:1. The reaction produced colorless anhydrous single crystals of {(HDMBI)+Cl}, C9H11ClN2, which were collected and analyzed using X-ray diffraction (XRD) techniques. A network of N–HCl hydrogen bond type interactions linking the protonated hetero-aromatic base to the chloride anions (bridging bases) stabilizes the crystal and mimics the N–HCl interactions that play important roles in CCl channel biological systems. The shortest NCl contact distance and corresponding N–HCl angle are 3.073(3) Å and 173(3), respectively. The packing is also assisted by weaker C–HCl hydrogen bond-type interactions and an extensive network of pp stacking interactions involving HDMBI+ cations. Density functional calculations at the B3LYP/6-31G⁄⁄ and /6-311++G⁄⁄ levels for models of fragments of the crystal structure allowed for the evaluation of geometric parameters, hydrogen bond-type interaction formation energies, and infrared parameters for {(HDMBI)+Cl} and {(HDMBI)+Cl(HDMBI)+}.