Crystal structures and supramolecular features of 9,9-dimethyl-3,7-diazabicyclo[3.3.1]nonane-2,4,6,8-Tetraone, 3,7-diazaspiro[bicyclo[3.3.1]nonane-9,1′-cyclopentane]-2,4,6,8-Tetraone and 9-methyl-9-phenyl-3,7-diazabicyclo[3.3.1]nonane-2,4,6,8-Tetraone dimethylformamide monosolvate

Compounds (I), C9H10N2O4, (II), C1 1H12N2O4, and (III), C1 4H12N2O4-C3H7NO represent 9,9-disubstituted-3,7-diazabicyclo[3.3.1]nonane-2,4,6,8-Tetraone derivatives with very similar molecular geometries for the bicyclic framework: The dihedral angle between the planes of the imide groups is 74.87 (6), 73.86 (3) and 74.83 (6)° in (I)-(III), respectively. The dimethyl derivative (I) is positioned on a crystallographic twofold axis and its overall geometry deviates only slightly from idealized C2v symmetry. The spiro-cyclopentane derivative (II) and the phenyl/ methyl analog (III) retain only internal Cs symmetry, which in the case of (II) coincides with crystallographic mirror symmetry. The cyclopentane moiety in (II) adopts an envelope conformation, with the spiro C atom deviating from the mean plane of the rest of the ring by 0.548 (2) A ° . In compound (III), an N-H·O hydrogen bond is formed with the dimethylformamide solvent molecule. In the crystal, both (I) and (II) form similar zigzag hydrogen-bonded ribbons through double intermolecular N-H·O hydrogen bonds. However, whereas in (I) the ribbons are formed by two trans-Arranged O C-N-H amide fragments, the amide fragments are cis-positioned in (II). The formation of ribbons in (III) is apparently disrupted by participation of one of its N-H groups in hydrogen bonding with the solvent molecule. As a result, the molecules of (III) form zigzag chains rather than the ribbons through intermolecular N-H·O hydrogen bonds. The crystal of (I) was a pseudomerohedral twin. © Vatsadze et al. 2017.