1H,4H-1,4-Diphenylpyridazino[1,2-α]pyridazine-6, 9-dione

Crystals of C₂₀H₁₆N₂O₂ are orthorombic:P2₁2₁2₁,a = 28.1364(21),b = 7.6474(2),c = 7.5376(2) Å,Z = 4, = 6.4 cm^–1 (CuK radiation), andM = 316.36. The structure has been solved by direct methods and refined by two-block least-squares toR = R _w = 0.042. The conformation of ringB is a distorted envelope at N(10), and the phenyl rings have acis configuration with respect to the pyridazine ring. Thermal motion of the molecule has been analyzed in terms of the rigid-body TLS model.On leave from Departamento de Fisica, Facultad de Ciencias Exactas, U.N.L.P., calle 115 esq. 49, La Plata, Buenos Aires, Argentina.