Reaction of Phenanthrene‐9,10‐dione with Phenanthrene‐9,10‐diol: Synthesis and Characterization of the First ortho‐Quinhydrone Derivative

Treatment of phenanthrene‐9,10‐dione (PQ) with phenanthrene‐9,10‐diol (PQH₂), as prepared by catalytic hydrogenation of PQ, in toluene solution or in the solid state afforded crystalline ‘9,10‐phenanthrenequinhydrone’ (PQH), the first example of an ortho‐quinhydrone. PQH was characterized by analytical and spectroscopic methods, including X‐ray and CP/MAS ¹³C‐NMR analyses. The crystal structure of PQH showed pairs of planar molecules linked by H‐bonds and organized in columns parallel to the crystallographic axis a. The solid‐state structure of PQH was compared with those of the parent compounds, PQ and PQH₂, the latter being reported for the first time. PQH was found to be stable in the solid state only, the components PQ and PQH₂ being formed upon dissolution in media of even low polarity such as toluene.