1-Phenyldiazenyl-8-Phenylhydrazononaphthalene-7(8H)-One-2-ol: Co-Existence of Azo-Hydroxy and Hydrazo-Keto Forms

Abstract  

The compound crystallizes in the triclinic P`1] P\bar{1} space group and unit cell dimensions of a = 8.158 ?, b = 12.490 ?, c = 17.129 ?; α = 93.24°, β = 94.72°, γ = 97.61° and Z = 4. The structure was solved by direct methods and refined to an R1 value of 0.0890 on 2,278 observed reflections. There are two molecules in the asymmetric residue unit of the compound. In the title compound C₂₂H₁₆N₄O₂, two diazene groups at C1 and C8 and two hydroxy groups at C2 and C7 bring into play a unique azo-hydrazo equilibrium in which azo-hydroxy and hydrazo-keto forms co-exist in the molecule. The hydrazone H atom and the keto O atom are linked by an intramolecular N–H···O hydrogen bond on the other hand the hydroxy H atom and the azo N atom are linked by two intramolecular O–H···N hydrogen bonds.