Crystal and molecular structure of a diradical, 1,3-dinitro-4,6-di[3-(2,2,5,5-tetramethyl)-pyrrolidinyl-N-oxide]aminobenzene monohydrate

The crystal structure of 1,3-dinitro-4,6-di3-(2,2,5,5-tetramethyl)pyrrolidinyl-N-oxide] aminobenzene monohydrate has been determined by single-crystal X-ray diffraction methods using the 1793 unique reflections for which 3 ° < 2θ < 40 ° andI > 3σ(I), and refined to a conventionalR index of 0.032. Counter methods using MoKα radiation were employed. Crystals form in the triclinic space groupP¯1 (No. 2) witha = 16.160(10),b = 11.686(6),c = 7.211(5) Å, α = 95.87(5) °, β = 98.67(5) °, and γ = 107.74(4) °. All hydrogen atom positions were determined. Intramolecular hydrogen-bonding between the nitro and amino groups has, in part, caused the central 20 atoms of the molecule, counting hydrogen atoms, to lie in an approximate plane. The benzene ring is distorted by its substituents to the symmetrymm2(C _2v ). The internal angles of the benzene ring range from 116.1 ° to 124.7 ° (esd = 0.3 °), and its bonds are between 1.368 Å and 1.436 Å (esd = 0.004 Å) in length. Four of the five atoms in each pyrrolidine ring are nearly coplanar; the remaining atom, the carbon bonded to the amine nitrogen in each case, lies approximately 0.53 Å from the corresponding plane. The best four-atom planes of the two pyrrolidine rings are each near to perpendicular to the central plane, giving the molecule a lobster-like appearance; they are each rotated approximately 15 °, in opposite senses, from perpendicular. The intramolecular distance between the two pyrrolidine nitrogen atoms, to which the unpaired charges can be assigned, is 7.68 Å. One of the nitroso oxygen atoms is hydrogen-bonded by two symmetry-equivalent water molecules. The inversion center necessitates that the remaining hydrogen atoms of these water molecules both hydrogen-bond to a symmetry-equivalent nitroso oxygen atom to give a hydrogen-bonded four-oxygen ring.