Abstract
In the title molecule, C10H8N2O, the five-and six-membered rings form a dihedral angle of 10.14 (9)angstrom. The aldehyde group is almost coplanar with the pyrazole ring to which it is connected [O-C-C-C torsion angle = -179.35 (17)degrees]. In the crystal, inversion dimers are linked by four C-H center dot center dot center dot O interactions as the carbonyl O atom accepts two such bonds. The dimeric aggregates are linked into supramolecular layers in the ac plane by C-H center dot center dot center dot pi and pi-pi [ring centroid(pyrrole) center dot center dot center dot ring centroid(phenyl) = 3.8058 (10)angstrom] interactions.