Crystal and molecular structure of sodium picrate monohydrate

Abstract

Na⁺ [C₆H₂(NO₂)₃O]⁻ H₂O,M _r=269.11, monoclinic,C2/m (No. 12),a=13.065(1),b=20.065(2),c=3.6957(4) Å,β=90.75(1)°,V=968.7(1) ų,Z=4,D _m=1.848 g cm⁻³ (by flotation),D _x=1.845 g cm⁻³, λ(CuKα)=1.54184 Å,μ(CuKα)=17.5 cm⁻¹,F(000)=540,T=295 K,R=0.055,wR=0.060 for 879 observed reflections withI≥2.5σ(I). p]In the structure the picrate anion has exact twofold symmetry, the water molecule has exact mirror symmetry and the two sodium cations occupy special positions on inversion centers at (0, 1/2, 0) and (1/2, 1/2, 1/2). The phenyl ring together with the four substituent N and O atoms is strictly planar, but the phenyl ring is severely distorted from hexagonal symmetry, as is commonly observed in structures containing the picrate fragment. Both sodium ions are eight-coordinated with Na(1) and Na(2) in a cubic and distorted cubic arrangement, respectively. Na(1) coordinates to four charged phenoxide O atoms and four O atoms of nitro groups, and Na(2) to four O atoms of nitro groups and four water molecules. The water molecule donates two hydrogen bonds to symmetry-related O(2) atoms ofortho nitro groups. Two symmetry-related O(3) atoms ofortho nitro groups serve as acceptors in a very unusual asymmetric bifurcated C-H⋯O hydrogen bond.