A second polymorph of (Z)-3-amino-4-(2-phenylhydrazinylidene)-1H-pyrazol-5(4H)-one

Abstract

The molecule of the title compound, C9H9N5O, is approximately planar (the r.m.s. deviation of all non-H atoms is 0.08 Å). The amine substituent is pyramidal at the N atom. An intramolecular N—Hhydrazine...O=C hydrogen bond is present. In the crystal, molecules are connectedviaN—H...N and N—H...O hydrogen bonds, forming infinite layers parallel to (010). This polymorph is triclinic, space groupP-1, whereas the previously reported form was monoclinic, space groupP21/c[Elgemeieet al.(2013).Acta Cryst. E69, o187], with stepped layers and a significantly lower density.