Crystal structure, Hirshfeld surface analysis, interaction energy and DFT studies of 4-[(4-allyl-2-methoxyphenoxy)methyl]-1-(4-methoxyphenyl)-1H-1,2,3-triazole

In the crystal structure, C—HMthphn⋯OMthphn (Mthphn = methoxyphenyl) hydrogen bonds form corrugated layers parallel to (100) that are connected along the a axis by C—H⋯π(ring) and π–π stacking interactions.

In the title molecule, C 20 H 21 N 3 O 3 , the allyl substituent is rotated out of the plane of its attached phenyl ring [torsion angle 100. 66 (15) ]. In the crystal, C-H Mthphn Á Á ÁO Mthphn (Mthphn = methoxyphenyl) hydrogen bonds lead to the formation of (100) layers that are connected into a three-dimensional network by C-HÁ Á Á(ring) interactions, together withstacking interactions [centroid-to-centroid distance = 3.7318 (10) Å ] between parallel phenyl rings. Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from HÁ Á ÁH (48.7%) and HÁ Á ÁC/CÁ Á ÁH (23.3%) interactions. Computational chemistry reveals that the C-H Mthphn Á Á ÁO Mthphn hydrogen bond energy is 47.1 kJ mol À1 . The theoretical structure, optimized by density functional theory (DFT) at the B3LYP/ 6-311 G(d,p) level, is compared with the experimentally determined molecular structure. The HOMO-LUMO behaviour was elucidated to determine the energy gap.
We report herein the synthesis, molecular and crystal structures of (I), along with the results of a Hirshfeld surface analysis, an interaction energy calculation, and a density functional theory (DFT) study.

Hirshfeld surface analysis
In order to visualize and quantify the intermolecular interactions in the crystal of (I), a Hirshfeld surface (HS) analysis (Hirshfeld, 1977;Spackman & Jayatilaka, 2009) was carried out by using Crystal Explorer 17.5 (Turner et al., 2017). In the HS plotted over d norm (Fig. 4), the white surface indicates contacts with distances equal to the sum of van der Waals radii, and the red and blue colours indicate distances shorter or longer than the van der Waals radii, respectively (Venkatesan et al., 2016). The bright-red spots appearing near hydrogen atoms (H6 and H19B), and near O3 indicate their roles in hydrogen bonding; they also appear as blue and red regions corresponding to positive (hydrogen-bond donors) and negative (hydrogen-bond acceptors) potentials on the HS mapped over electrostatic potential (Spackman et al., 2008;Jayatilaka et al., 2005), as shown in Fig. 5. The HS plotted over the shape-index (Fig. 6) Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
A portion of one layer viewed along the a axis, with C-H Mthphn Á Á ÁO Mthphn (Mthphn = methoxyphenyl) hydrogen bonds depicted by dashed lines.

Figure 1
The molecular structure of (I) with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.
actions (visualized as red and blue areas) in (I), as discussed above.
The overall two-dimensional fingerprint plot, Fig View of the three-dimensional Hirshfeld surface of the title compound plotted over d norm in the range of À0.2587 to 1.3813 a.u..

Figure 5
View of the three-dimensional Hirshfeld surface of the title compound plotted over electrostatic potential energy in the range À0.0500 to 0.0500 a.u..

Figure 6
Hirshfeld surface of the title compound plotted over shape-index.

DFT calculations
Density functional theory (DFT) using standard B3LYP functional and 6-311 G(d,p) basis-set calculations (Becke, 1993) as implemented in GAUSSIAN 09 (Frisch et al., 2009) was used to optimize the molecular structure of (I) in the gas phase. Theoretical and experimental results in terms of bond lengths and angles are in good agreement ( Table 2).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 4. Hydrogen atoms were located in a difference-Fourier map and were refined freely.  HOMO and LUMO of (I), and the energy band gap between them.   program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018/1 (Sheldrick, 2015b); molecular graphics: DIAMOND (Brandenburg & Putz, 2012); software used to prepare material for publication: publCIF (Westrip, 2010).

Special details
Experimental. The diffraction data were obtained from 3 sets of 400 frames, each of width 0.5° in ω, colllected at φ = 0.00, 90.00 and 180.00° and 2 sets of 800 frames, each of width 0.45° in φ, collected at ω = -30.00 and 210.00°. The scan time was 10 sec/frame. Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq O1 0.22952 (5