X-ray crystal structure of C.I. Disperse Brown 1

Crystals of C.I. Disperse Brown 1, an aminoazobenzene derivative, were grown from an ethanol solution and the crystal structure was determined by single crystal X-ray diffraction analysis. The dye molecule crystallizes in the orthorhombic Fdd2 space group with the unit cell dimensions: a = 30.6593(17) Å, b = 32.2928(18) Å, c = 7.3738(4) Å, α = β = γ = 90°, V = 7300.6(7) Å3. Results showed that the 4-nitro-4′-aminoazobenzene skeleton is non-planar, with a dihedral angle of 45.53° between the phenyl rings presumably to minimize the repulsive force between Cl atoms in each ring. Several types of intra- and intermolecular hydrogen bonds, together with anti-parallel interlayer π–π stacking interaction also stabilize the molecular conformation. In particular, two aminoalcohol chains form a pseudo-cycle by strong O–H⋯O intramolecular hydrogen bond.