6-Nitro-[1,10]phenanthroline-1-ium nitrate: crystal structure, ab initio calculations and protonation character

The title compound, 6-nitro-1,10]phenanthroline-1-ium nitrate, has been synthesized and characterized by elemental analysis, electron absorption spectroscopy, IR, ¹H and ¹³C NMR spectroscopy. The X-ray crystal structure study showed that the compound crystallizes in the monoclinic system, space group Cc, with M_r=288.22 (C₁₂H₈N₄O₅), a=13.861(3), b=10.142(2), c=8.7320(17) Å, β=103.70(3)°, V=1192.6(4) Å³, Z=4, D_c=1.605 g/cm³, F(000)=592, μ(Mo Kα)=0.129 mm⁻¹, R=0.0439, wR=0.1125, GOF=1.110. In the crystal lattice, the molecules create a network structure through hydrogen bonds. Ab initio calculations of the structures, charges distribution, natural bond orbitals, topological analysis and thermodynamic functions of 5-nitro-1,10]phenanthroline and its protonated cation were performed at HF/6-311G** and B3LYP/6-311G** levels of theory. The calculation results are in a good agreement with the X-ray data and show that the protonated structure is stable. The calculation of second order optical nonlinearity was carried out and a higher molecular hyperpolarizability of 24.66×10⁻³⁰ esu was predicted.