A monoclinic polymorph of 4-(2H-1,3-benzodioxol-5-yl)-1-(4-methylphenyl)-1H-pyrazol-5-amine

A second polymorph (monoclinic with Z′ = 1) of the title compound is reported in which the conformation resembles one of the independent molecules of the original triclinic polymorph (Z′ = 2).


Structural commentary
The molecule in (mI), Fig. 1, comprises a central and almost planar pyrazolyl ring (r.m.s. deviation of the five atoms = 0.0043 Å ) flanked by an N-bound p-tolyl group and a C-bound 1,3-benzodioxolyl fused ring system. In the latter, the fivemembered dioxolyl ring adopts an envelope conformation with the methylene-C17 atom being the flap; the C17 atom lies 0.318 (2) Å out of the least-squares plane defined by the O1, O2, C14 and C15 atoms (r.m.s. deviation = 0.0005 Å ). The dihedral angles between the central ring and the N-and Cbound six-membered rings are 50.06 (5) and 27.27 (5) , respectively. The dihedral angle between the six-membered rings is 77.31 (4) , indicating an overall twisted arrangement. In general terms, the relative disposition of the amino and dioxolyl substituents may be described as being syn.
While (mI) crystallizes with Z 0 = 1, the triclinic polymorph, (tI), crystallizes with Z 0 = 2 (Gajera et al., 2013). In the latter, the molecules have quite different conformations. In one of the independent molecules, the amino and dioxolyl substituents are syn, as for (mI), and in the other these substituents are anti. These differences in molecular conformations are highlighted in Fig. 2. The syn/anti distinction is quite clear from this overlap diagram where the dioxolyl ring obviously occupies a different position in the second independent mol-ecule of (tI, blue image). Also evident from Fig. 2 are variations in the relative dispositions of six-membered rings. These variations are quantified in Table 1.

PXRD study
In order to ascertain the nature of the crystalline residue isolated from recrystallization of (I) from ethyl acetate solution, a powder X-ray diffraction (PXRD) experiment was performed on a PANalytical Empyrean XRD system with Cu K1 radiation ( = 1.54056 Å ) in the 2 range of 5 to 50 with a step size of 0.026 . The pattern was analyzed with X'Pert HighScore Plus (PANalytical, 2009). This analysis indicated that the ratio of (mI) to (tI) in the overall sample was 49.1:50.9. This distribution suggests that effectively in the sample there is a 3:1 ratio of molecules with a syn disposition of the amino and dioxolyl substituents to those with a trans arrangement.  The molecular structure of the molecule found in the monoclinic polymorph showing the atom-labelling scheme and displacement ellipsoids at the 70% probability level. Table 1 Dihedral angle ( ) data for the three independent molecules in (mI) and (tI).
Structure pyrazolyl/p-tolyl pyrazolyl/benzo-C 6 p-tolyl/benzo-C 6 (mI) 50.06 ( Figure 2 Overlay diagram of the title compound, (mI), red image, with the two independent molecules in (tI), green (molecule a) and blue (b) images. The molecules have been overlapped so that the central pyrazolyl rings are coincident.

Figure 3
A view of a supramolecular helical chain aligned along the b axis and mediated by amino-pyrazolyl N-HÁ Á ÁN hydrogen bonds shown as blue dashed lines.

Supramolecular features
The most notable feature of the crystal packing in (mI) is the formation of supramolecular helical chains aligned along the b axis and mediated by amino-pyrazolyl N-HÁ Á ÁN hydrogen bonds, Fig. 3 and Table 2. The chains are consolidated into layers in the bc plane by pyrazolyl-tolyl C10-HÁ Á Á and methylene-benzo-C 6 C17-HÁ Á Á interactions, Table 2. The layers inter-digitate along the a axis whereby the dioxolyl rings face each other, Fig. 4. The C-HÁ Á ÁO interactions are at distances beyond the standard criteria (Spek, 2009). In the packing scheme just described, no specific role is found for the second amino-H2N atom. To a first approximation, the mode of association between molecules in (tI) is similar in that supramolecular chains are formed. These comprise alternating independent molecules a and b that are connected by aminopyrazolyl N-HÁ Á ÁN hydrogen bonds. The difference is that in (tI), the chains have a zigzag topology. Chains in (tI) are connected by C-HÁ Á ÁO and C-HÁ Á Á interactions.

Analysis of the Hirshfeld surfaces
In order to investigate further the nature of the crystal packing in (mI) and (tI), an analysis of the Hirshfeld surfaces (Spackman & Jayatilaka, 2009)  Unit-cell contents shown in projection down the c axis. The N-HÁ Á ÁN and C-HÁ Á Á interactions are shown as blue and purple dashed lines, respectively.

Figure 6
Relative contributions of various intermolecular contacts to the Hirshfeld surface area in (a) mI, and of (tI) molecules (b) a and (c) b.

Synthesis and crystallization
The title compound was synthesized according to the same synthetic process as described in the original report (Gajera et al., 2013). Single crystals suitable for X-ray measurements in the form of light-brown prisms were obtained from its ethyl acetate solution at room temperature.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. Carbon-bound H-atoms were placed in calculated positions (C-H = 0.95-0.99 Å ) and were included in the refinement in the riding model approximation, with U iso (H) set to 1.2-1.5U eq (C). The N-bound H atoms were located in a difference Fourier map but were refined with a distance restraint of N-H = 0.88AE0.01 Å , and with U iso (H) set to 1.2U eq (N).

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.