Hydrogen-bonded supramolecular motifs in crystal structures of trimethoprim barbiturate monohydrate (I) and 2-amino-4,6-dimethylpyrimidinium barbiturate trihydrate (II)

In the present study, we report the crystal structures of two organic salts, namely 2,4-diamino-5-(3′,4′,5′-trimethoxybenzyl)pyrimidinium (TMP) barbiturate monohydrate (TMPBAR) (I), 2-amino-4,6-dimethylpyrimidinium (AMPY) barbiturate trihydrate (AMPYBAR) (II). In both complexes, one ring nitrogen of TMP and AMPY are protonated as a result of proton transfer from the−CH₂ group of barbituric acid. In compound (I), the TMP cation and barbiturate anion are paired through twoN−H···O and one N−H···N hydrogen bonds. This pair further self-organizes through N−H···O hydrogen bonds to generate an array of six hydrogen bonds. These arrays are further cross-linked by N−H···O hydrogen bonds forming a sheet-like structure. The water molecule is also embedded in the sheet via O−H···O and C−H···O hydrogen bonds, forming a rosette-like supramolecular motif. TMP cations are also bridged by alternating water molecules via C−H···O and O−H···N hydrogen bonds. In compound (II), the symmetrical barbiturate anions self-organize on both sides through N−H···O hydrogen bonds generating a supramolecular chain. These chains are cross-linked by the three water molecules. A pair of barbiturate anions and two water molecules constitute an array of four hydrogen bonds (DADA quadruple array). These arrays are cross-linked by another water molecule. 2-Amino-4,6-dimethylpyrimidine cations are paired through N−H···N hydrogen bonds. These pairs are bridged by three water molecules generating a supramolecular ribbon. The barbiturate chains and base pairs are arranged in an alternate manner via N−H···O and O−H···O hydrogen bonds to generate a 3-D network.     

Sparfloxacindium tetrabromidocuprate(II) monohydrate crystal structure

Structure solution has been carried out for a compound containing doubly charged sparfloxacindium cation, namely ((C₁₉H₂₄F₂N₄O₃)[CuBr₄] · H₂O (I), where C₁₉H₂₂F₂N₄O₃ is sparfloxacin. The crystals of I are orthorhombic with a = 14.533(4) Å, b = 12.557(4) Å, c = 29.370(9) Å, V = 2360(3) ų, space group Pbca, Z = 8. In compound I, unlike in similar compounds of other fluoroquinolones, the second proton is attached to the sparfloxacin through the amino nitrogen atom instead of being attached through the ketone oxygen atom. This specific protonation feature of SfH is manifested in the specifics of supramolecular organization of I.