A second monoclinic polymorph for 3-amino-1-(4-meth-oxy-phen-yl)-9,10-dihydro-phenanthrene-2,4-dicarbonitrile.

The title compound, C(23)H(17)N(3)O, has been previously described in a monoclinic P2(1)/c polymorph with Z = 4 [Asiri, Al-Youbi, Faidallah, Ng & Tiekink (2011). Acta Cryst. E67, o2449]. In the new monoclinic P2(1)/n form, with Z = 8, there are two independent mol-ecules, A and B, in the asymmetric unit. In both mol-ecules, the cyclo-hexa-1,3-diene ring has a screw-boat conformation, whereas it is a distorted half-chair in the original polymorph. There is a fold in each mol-ecule, as indicated by the dihedral angle between the benzene rings of the 1,2-dihydro-naphthalene and aniline residues of 33.19 (10)° (mol-ecule A) and 30.6 (10)° (mol-ecule B). The meth-oxy-benzene ring is twisted out of the plane of the aniline residue to which it is connected [dihedral angles = 49.22 (10) and 73.27 (10)°, in A and B respectively]. In the crystal, the two independent mol-ecules self-associate via N-H⋯N hydrogen bonds, generating a 12-membered {⋯HNC(3)N}(2) synthon. These are connected into a supra-molecular tape in the (-101) plane by N-H⋯O(meth-oxy) inter-actions. In the P2(1)/c polymorph, supra-molecular layers are formed by N-H⋯N and N-H⋯O inter-actions.