Crystal structure and DFT study of (E)-2,6-di-tert-butyl-4-{[2-(pyridin-2-yl)hydrazin-1-yl­idene)meth­yl}phenol

Faizi, M.S.H.; Haque, A.; Dege, M.; Dege, N.; Malysheva, M.L.

doi:10.1107/S2056989017011707

research communications

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ISSN: 2056-9890

Volume 73| Part 10| October 2017| Pages 1449-1452

https://doi.org/10.1107/S2056989017011707

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Crystal structure and DFT study of (E)-2,6-di-tert-butyl-4-{[2-(pyridin-2-yl)hydrazin-1-ylidene)methyl}phenol

Md. Serajul Haque Faizi,^a ^* Ashanul Haque,^a Mustafa Dege,^b Necmi Dege ^c and Maria L. Malysheva ^d

^aDepartment of Chemistry, College of Science, Sultan Qaboos University, PO Box 36 Al-Khod 123, Muscat, Sultanate of , Oman, ^bSpraying Systems Company Turkey, Esentepe Mah. Kore Şehitleri Cad. Kaya Aldoğan Sok., Serhan apt. No:3 Daire:3 Şişli / İstanbul, Turkey, ^cOndokuz Mayıs University, Arts and Sciences Faculty, Department of Physics, Atakum 55139 Samsun, Turkey, and ^dDepartment of Chemistry, Taras Shevchenko National University of Kyiv, 64, Vladimirska Str., Kiev 01601, Ukraine
^*Correspondence e-mail: maria_malysheva@mail.univ.kiev.ua

Edited by P. C. Healy, Griffith University, Australia (Received 23 July 2017; accepted 9 August 2017; online 12 September 2017)

The title compound, C₂₀H₂₇N₃O, was synthesized by condensation reaction of 3,5-di-tert-butyl-4-hydroxybenzaldehyde and 2-hydrazinylpyridine, and crystallizes in the centrosymmetric monoclinic space group C2/c. The conformation about the C=N bond is E. The dihedral angle between the rings is 18.1 (3)°. An intermolecular N—H⋯N hydrogen bond generates an R₂²(8) ring motif. In the crystal, N—H⋯N hydrogen bonds connect pairs of molecules, forming dimers. Density functional theory (DFT) optimized structures at the B3LYP/6–311 G(d,p) level are compared with the experimentally determined molecular structure in the solid state.

Keywords: crystal structure; hydrazine; 2- hydrazinopyridine; 3,5-di-tert-butyl-4-hydroxybenzaldehyde; hydrogen bonding; Schiff base.

CCDC reference: 1567740

1. Chemical context

Sterically hindered phenol anti-oxidants are widely used in polymers and lubricants. They can protect polymers by increasing both their process stability and their long-term stability against oxidative degradation (Yamazaki & Seguchi, 1997 ; Silin et al., 1999 ). Hydrazones and Schiff bases have attracted much attention for their excellent biological properties, especially for their potential pharmacological and antitumor properties (Küçükgüzel et al., 2006 ; Khattab, 2005 ; Karthikeyan et al., 2006 ; Okabe et al., 1993 ). Furthermore, 3,5-di-tert-butyl-2-hydroxybenzaldehyde-derived Schiff bases shows proton tautomerization, which plays an important role in many fields of chemistry and biochemistry. The tautomerization in salicylideneanilines has been the subject of particular interest because it is closely related to thermochromism and photochromism. While salicylideneanilines are widely used as precursor compounds for the design of various type new metal complexes, they are also convenient model compounds for studying theoretical aspects of coordination chemistry and photochemistry, as well as for designing molecular architectures by means of molecular motifs capable of hydrogen-bond formation. The present work is a part of an ongoing structural study of Schiff bases and their utilization in the synthesis of quinoxaline derivatives (Faizi et al., 2016a ), fluorescence sensors (Faizi et al., 2016b ) and azoimine compounds (Faizi et al., 2015 , 2017 ). We report herein on the synthesis and crystal structure and DFT computational calculation of the new title Schiff base compound with a sterically hindered phenol, (I). The results of calculations by density functional theory (DFT) on (I) carried out at the B3LYP/6-311 G(d,p) level are compared with the experimentally determined molecular structure in the solid state.

2. Structural commentary

The molecular structure of (I), shown in Fig. 1, is not planar, with the dihedral angle between the pyridyl and tert-butyl substituted benzene rings being 18.19 (3)°. The N—N and N—C bond lengths are of 1.396 (7) and 1.253 (7) Å, respectively, indicate single- and double-bond character for these bonds. The C1—O1 bond length of 1.370 (6) Å indicates single-bond character. The conformation about the C15=N1 bond is E with an N2—N1—C15—C4 torsion angle of 177.9 (5)°. Bond distances for (I) are comparable to those found in closely related structures (Fun et al., 2013 ). It appears that the hydroxy group is prevented from forming a hydrogen bond because of steric hindrance by the tert-butyl groups.

Figure 1
The molecular structure of the title compound, with the atom labelling. Displacement ellipsoids are drawn at the 40% probability level.

3. Supramolecular features

In the crystal, molecules are connected by pairs of N—H⋯N hydrogen bonds (Fig. 2, Table 1), forming dimers with graph set R₂² (8). In addition, weak C—H⋯O hydrogen bonds and C—H⋯π interactions connect the dimers, forming chains along [100] (Fig. 3). There are no other significant intermolecular contacts present.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2—H2⋯N3ⁱ	0.86	2.23	3.062 (8)	162
Symmetry code: (i) $[-x+{\script{1\over 2}}, -y-{\script{1\over 2}}, -z+1]$ .

Figure 2
Molecules of the title compound forming a dimer through N—H⋯N hydrogen bonds, generating an R₂²(8) ring motif.

Figure 3
Part of the structure exhibiting weak C—H⋯O hydrogen bonds and C—H⋯π interactions (shown as dashed lines) along a axis.

4. DFT study

The DFT quantum-chemical calculations were performed at the B3LYP/6-311 G(d,p) level (Becke, 1993 ) as implemented in GAUSSIAN09 (Frisch et al., 2009 ). DFT structure optimization of (I) was performed starting from the X-ray geometry and the values compared with experimental values (see Table 2). From these results we can conclude that basis set 6-311 G(d,p) is well suited in its approach to the experimental data.

Table 2
Comparison of selected observed (X-ray data) and calculated (DFT) geometric parameters (Å, °)

Parameter	X-ray	B3LYP/6–311G(d,p)
O1—C1	1.370 (6)	1.370
C15—N1	1.253 (7)	1.252
N3—C20	1.386 (8)	1.386
N1—N2	1.396 (7)	1.395
N3—C16	1.292 (8)	1.292
C16—N2—N1	122.6 (6)	122.7
C15—N1—N2	118.8 (6)	118.9
N1—C15—C4	121.9 (6)	121.9
N2—N1—C15—C4	177.9 (5)	177.8

The DFT study of (I) shows that the HOMO and LUMO are localized in the plane extending from the whole pyridine ring to the phenol ring. The electron distribution of the HOMO-1, HOMO, LUMO and the LUMO+1 energy levels are shown in Fig. 4. The HOMO molecular orbital exhibits both σ and π character, whereas HOMO-1 is dominated by π-orbital density. The LUMO is mainly composed of σ-density while LUMO+1 has both σ and π electronic density. The HOMO–LUMO gap was found to be 0.1562 a.u. and the frontier molecular orbital energies, E_HOMO and E_LUMO are −0.201 and −0.045 a.u., respectively.

Figure 4
Electron distribution of the HOMO-1, HOMO, LUMO and LUMO+1 energy levels for the title compound.

5. Database survey

There are very few examples of similar compounds in the literature. To the best of our knowledge, the similar compound synthesized by (Cuadro et al., 1998 ) for biological evaluation of 5-lipoxygenase inhibitors has not been structurally characterized. Two very similar compounds have been reported, one synthesized from 2-hydrazinylpyridine and 4-tert-butyl-2,6-diformylphenol (Li et al., 2013 ) as a fluorescent chemosensor for Zn^II and applications in live cell imaging. The other compound is the Schiff base 2,4-di-tert-butyl-6-{[2-(pyridin-2-yl)hydrazono]methyl}phenol used for stabilization of oxidovanadium(IV) (Kundu et al., 2013 ).A search of the Cambridge Structural Database (CSD, Version 5.37, update May 2016; Groom et al., 2016 ) shows that these compounds have not been characterized by X-ray diffraction.

6. Synthesis and crystallization

A mixture of 3,5-di-tert-butyl-4-hydroxybenzaldehyde 0.100 g (0.427 mmol) and 2-hydrazinylpyridine 0.046 g (0.427 mmol) in methanol was refluxed for 3 h in the presence of a catalytic amount of glacial acetic acid. After cooling, the red-coloured precipitate was washed with hot methanol several times, and then dried, giving a red-coloured shiny crystalline compound in 86% yield (0.120 g). Red block-like crystals of the title compound were obtained by slow evaporation of a solution in dichloromethane and ethanol (5:1 v/v).

7. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3. All C-bound hydrogen atoms were included in calculated positions with C—H = 0.93 (aromatic) or 0.96 Å (methylene) and allowed to ride, with U_iso(H) = 1.2U_eq(C). The N-bound H atom was located in a difference-Fourier map but was also allowed to ride in the refinement with N—H = 0.86 Å and U_iso(H) = 1.2U_eq(N).

Table 3
Experimental details

Crystal data
Chemical formula	C₂₀H₂₇N₃O
M_r	325.44
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	296
a, b, c (Å)	29.5091 (15), 6.2270 (4), 20.2703 (10)
β (°)	91.130 (4)
V (Å³)	3724.0 (4)
Z	8
Radiation type	Mo Kα
μ (mm⁻¹)	0.07
Crystal size (mm)	0.33 × 0.24 × 0.08

Data collection
Diffractometer	Stoe IPDS 2
Absorption correction	Integration (X-RED32; Stoe & Cie, 2002 )
T_min, T_max	0.978, 0.994
No. of measured, independent and observed [I > 2σ(I)] reflections	17357, 3468, 1430
R_int	0.097
(sin θ/λ)_max (Å⁻¹)	0.606

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.101, 0.321, 0.96
No. of reflections	3468
No. of parameters	222
No. of restraints	4
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.95, −0.34
Computer programs: X-AREA and X-RED32 (Stoe & Cie, 2002), SHELXT (Sheldrick 2015a ), SHELXL2016 (Sheldrick, 2015b ), ORTEP-3 for Windows and WinGX (Farrugia, 2012 ) and PLATON (Spek, 2009 ).

Supporting information

CCDC reference: 1567740

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989017011707/hg5492sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017011707/hg5492Isup2.hkl

checkCIF report

Computing details top

Data collection: X-AREA (Stoe & Cie, 2002); cell refinement: X-AREA (Stoe & Cie, 2002); data reduction: X-RED32 (Stoe & Cie, 2002); program(s) used to solve structure: SHELXT (Sheldrick 2015a); program(s) used to refine structure: SHELXL2016 (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: WinGX (Farrugia, 2012) and PLATON (Spek, 2009).

(E)-2,6-Di-tert-butyl-4-{[2-(pyridin-2-yl)hydrazin-1-ylidene)methyl}phenol top

Crystal data top

C₂₀H₂₇N₃O	F(000) = 1408
M_r = 325.44	D_x = 1.161 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 29.5091 (15) Å	Cell parameters from 10906 reflections
b = 6.2270 (4) Å	θ = 1.4–26.8°
c = 20.2703 (10) Å	µ = 0.07 mm⁻¹
β = 91.130 (4)°	T = 296 K
V = 3724.0 (4) Å³	Stick, red
Z = 8	0.33 × 0.24 × 0.08 mm

Data collection top

Stoe IPDS 2 diffractometer	3468 independent reflections
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus	1430 reflections with I > 2σ(I)
Plane graphite monochromator	R_int = 0.097
Detector resolution: 6.67 pixels mm^-1	θ_max = 25.5°, θ_min = 1.4°
rotation method scans	h = −35→35
Absorption correction: integration (X-RED32; Stoe & Cie, 2002)	k = −7→7
T_min = 0.978, T_max = 0.994	l = −24→24
17357 measured reflections

Refinement top

Refinement on F²	4 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.101	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.321	w = 1/[σ²(F_o²) + (0.1794P)²] where P = (F_o² + 2F_c²)/3
S = 0.96	(Δ/σ)_max < 0.001
3468 reflections	Δρ_max = 0.95 e Å⁻³
222 parameters	Δρ_min = −0.34 e Å⁻³

Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
O1	0.44818 (13)	0.9043 (6)	0.53805 (18)	0.0870 (13)
C6	0.40894 (16)	0.6560 (8)	0.4671 (2)	0.0602 (12)
C1	0.41473 (17)	0.7532 (8)	0.5303 (2)	0.0643 (13)
N3	0.25835 (18)	−0.3445 (11)	0.4118 (3)	0.0956 (15)
C5	0.37623 (17)	0.4983 (8)	0.4620 (2)	0.0653 (13)
H5	0.371669	0.430688	0.421532	0.078*
C2	0.38832 (17)	0.6977 (7)	0.5845 (2)	0.0616 (13)
C7	0.43754 (17)	0.7232 (8)	0.4082 (2)	0.0652 (13)
C4	0.34989 (16)	0.4362 (8)	0.5145 (2)	0.0630 (13)
C3	0.35632 (17)	0.5396 (8)	0.5744 (2)	0.0682 (13)
H3	0.338180	0.500452	0.609405	0.082*
C11	0.39633 (18)	0.8015 (8)	0.6539 (2)	0.0692 (14)
C16	0.2803 (2)	−0.1665 (11)	0.4050 (3)	0.0854 (18)
C15	0.31797 (19)	0.2599 (9)	0.5093 (3)	0.0753 (15)
H15	0.299604	0.229578	0.544903	0.090*
N1	0.31443 (18)	0.1472 (10)	0.4583 (3)	0.1040 (17)
C9	0.48786 (17)	0.6685 (9)	0.4218 (3)	0.0788 (15)
H9A	0.498240	0.741762	0.460985	0.118*
H9B	0.491083	0.516377	0.427934	0.118*
H9C	0.505562	0.713463	0.385090	0.118*
C14	0.3634 (2)	0.7150 (10)	0.7038 (3)	0.0892 (18)
H14A	0.367140	0.562344	0.707671	0.134*
H14B	0.369399	0.781038	0.745907	0.134*
H14C	0.332975	0.746899	0.689537	0.134*
C8	0.4238 (2)	0.6008 (10)	0.3455 (2)	0.0842 (17)
H8A	0.442361	0.646829	0.309754	0.126*
H8B	0.427952	0.449608	0.352592	0.126*
H8C	0.392568	0.629283	0.334777	0.126*
C10	0.4322 (2)	0.9641 (8)	0.3928 (3)	0.0794 (15)
H10A	0.440539	1.046680	0.431129	0.119*
H10B	0.451519	1.002048	0.357028	0.119*
H10C	0.401251	0.993870	0.380523	0.119*
N2	0.2841 (2)	−0.0247 (10)	0.4575 (3)	0.1095 (18)
H2	0.267022	−0.043331	0.490969	0.131*
C13	0.3886 (2)	1.0443 (9)	0.6502 (3)	0.0920 (19)
H13A	0.408889	1.106044	0.618980	0.138*
H13B	0.357876	1.072581	0.636557	0.138*
H13C	0.394300	1.106719	0.692927	0.138*
C20	0.2570 (2)	−0.4838 (11)	0.3587 (4)	0.0966 (19)
H20	0.241637	−0.613249	0.362703	0.116*
C17	0.3004 (2)	−0.1115 (11)	0.3471 (4)	0.0971 (19)
H17	0.314885	0.020392	0.343305	0.117*
C12	0.4451 (2)	0.7483 (11)	0.6794 (3)	0.0922 (18)
H12A	0.450337	0.816345	0.721370	0.138*
H12B	0.466707	0.799996	0.648434	0.138*
H12C	0.448268	0.595631	0.684231	0.138*
C19	0.2775 (2)	−0.4384 (12)	0.3005 (3)	0.0912 (18)
H19	0.276520	−0.535037	0.265545	0.109*
C18	0.2992 (2)	−0.2481 (13)	0.2956 (3)	0.098 (2)
H18	0.313282	−0.211489	0.256542	0.117*
H1	0.4585 (7)	0.975 (3)	0.5674 (9)	0.22 (5)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.101 (3)	0.082 (3)	0.078 (2)	−0.042 (2)	0.008 (2)	−0.013 (2)
C6	0.065 (3)	0.054 (3)	0.061 (3)	−0.006 (2)	0.005 (2)	0.002 (2)
C1	0.074 (3)	0.056 (3)	0.063 (3)	−0.012 (3)	0.006 (2)	−0.005 (2)
N3	0.086 (3)	0.110 (4)	0.091 (3)	0.011 (3)	0.016 (3)	0.009 (3)
C5	0.080 (3)	0.057 (3)	0.058 (3)	−0.008 (3)	0.001 (2)	0.002 (2)
C2	0.073 (3)	0.049 (3)	0.063 (3)	0.001 (2)	0.003 (2)	−0.002 (2)
C7	0.074 (3)	0.061 (3)	0.061 (3)	−0.009 (2)	0.011 (2)	0.001 (2)
C4	0.066 (3)	0.054 (3)	0.069 (3)	−0.006 (2)	0.004 (2)	0.003 (2)
C3	0.069 (3)	0.064 (3)	0.072 (3)	−0.008 (3)	0.009 (2)	0.007 (3)
C11	0.083 (3)	0.064 (3)	0.062 (3)	−0.002 (3)	0.006 (3)	−0.002 (2)
C16	0.094 (4)	0.074 (4)	0.087 (4)	0.003 (4)	−0.014 (4)	−0.012 (4)
C15	0.084 (4)	0.070 (3)	0.071 (3)	−0.014 (3)	−0.003 (3)	−0.014 (3)
N1	0.096 (4)	0.099 (4)	0.116 (4)	−0.026 (3)	0.007 (3)	0.020 (3)
C9	0.075 (3)	0.079 (4)	0.082 (3)	−0.002 (3)	0.013 (3)	−0.002 (3)
C14	0.109 (4)	0.096 (4)	0.064 (3)	0.011 (4)	0.025 (3)	0.004 (3)
C8	0.101 (4)	0.089 (4)	0.062 (3)	−0.016 (3)	0.000 (3)	−0.006 (3)
C10	0.089 (4)	0.066 (3)	0.083 (3)	−0.006 (3)	0.010 (3)	0.015 (3)
N2	0.115 (4)	0.109 (4)	0.105 (4)	−0.034 (4)	0.020 (3)	−0.002 (3)
C13	0.130 (5)	0.062 (4)	0.084 (4)	0.003 (3)	0.015 (4)	−0.011 (3)
C20	0.087 (4)	0.089 (5)	0.114 (5)	−0.017 (4)	0.009 (4)	0.006 (4)
C17	0.096 (5)	0.089 (5)	0.106 (5)	−0.009 (4)	−0.003 (4)	0.010 (4)
C12	0.094 (4)	0.111 (5)	0.071 (3)	0.007 (4)	−0.005 (3)	−0.006 (3)
C19	0.083 (4)	0.106 (5)	0.085 (4)	−0.014 (4)	0.013 (3)	−0.022 (4)
C18	0.087 (4)	0.127 (6)	0.081 (4)	−0.013 (4)	0.007 (3)	−0.002 (4)

Geometric parameters (Å, º) top

O1—C1	1.370 (6)	C9—H9A	0.9600
O1—H1	0.794 (15)	C9—H9B	0.9600
C6—C5	1.379 (6)	C9—H9C	0.9600
C6—C1	1.423 (6)	C14—H14A	0.9600
C6—C7	1.534 (7)	C14—H14B	0.9600
C1—C2	1.403 (7)	C14—H14C	0.9600
N3—C16	1.292 (8)	C8—H8A	0.9600
N3—C20	1.383 (8)	C8—H8B	0.9600
C5—C4	1.385 (7)	C8—H8C	0.9600
C5—H5	0.9300	C10—H10A	0.9600
C2—C3	1.377 (7)	C10—H10B	0.9600
C2—C11	1.561 (7)	C10—H10C	0.9600
C7—C8	1.530 (7)	N2—H2	0.8600
C7—C10	1.540 (7)	C13—H13A	0.9600
C7—C9	1.543 (7)	C13—H13B	0.9600
C4—C3	1.384 (7)	C13—H13C	0.9600
C4—C15	1.449 (7)	C20—C19	1.364 (9)
C3—H3	0.9300	C20—H20	0.9300
C11—C14	1.515 (7)	C17—C18	1.347 (9)
C11—C13	1.531 (7)	C17—H17	0.9300
C11—C12	1.555 (7)	C12—H12A	0.9600
C16—C17	1.369 (9)	C12—H12B	0.9600
C16—N2	1.386 (8)	C12—H12C	0.9600
C15—N1	1.253 (7)	C19—C18	1.351 (9)
C15—H15	0.9300	C19—H19	0.9300
N1—N2	1.396 (7)	C18—H18	0.9300

C1—O1—H1	136.7 (16)	C11—C14—H14A	109.5
C5—C6—C1	116.2 (4)	C11—C14—H14B	109.5
C5—C6—C7	122.0 (4)	H14A—C14—H14B	109.5
C1—C6—C7	121.7 (4)	C11—C14—H14C	109.5
O1—C1—C2	119.3 (4)	H14A—C14—H14C	109.5
O1—C1—C6	117.9 (4)	H14B—C14—H14C	109.5
C2—C1—C6	122.8 (4)	C7—C8—H8A	109.5
C16—N3—C20	117.4 (5)	C7—C8—H8B	109.5
C6—C5—C4	122.9 (4)	H8A—C8—H8B	109.5
C6—C5—H5	118.5	C7—C8—H8C	109.5
C4—C5—H5	118.5	H8A—C8—H8C	109.5
C3—C2—C1	116.7 (4)	H8B—C8—H8C	109.5
C3—C2—C11	121.5 (5)	C7—C10—H10A	109.5
C1—C2—C11	121.8 (4)	C7—C10—H10B	109.5
C8—C7—C6	111.8 (4)	H10A—C10—H10B	109.5
C8—C7—C10	107.0 (4)	C7—C10—H10C	109.5
C6—C7—C10	111.6 (4)	H10A—C10—H10C	109.5
C8—C7—C9	106.1 (4)	H10B—C10—H10C	109.5
C6—C7—C9	110.0 (4)	C16—N2—N1	122.6 (6)
C10—C7—C9	110.2 (4)	C16—N2—H2	118.7
C3—C4—C5	118.3 (4)	N1—N2—H2	118.7
C3—C4—C15	119.6 (5)	C11—C13—H13A	109.5
C5—C4—C15	122.0 (5)	C11—C13—H13B	109.5
C2—C3—C4	123.1 (5)	H13A—C13—H13B	109.5
C2—C3—H3	118.5	C11—C13—H13C	109.5
C4—C3—H3	118.5	H13A—C13—H13C	109.5
C14—C11—C13	106.7 (5)	H13B—C13—H13C	109.5
C14—C11—C12	107.6 (4)	C19—C20—N3	122.5 (6)
C13—C11—C12	111.2 (5)	C19—C20—H20	118.7
C14—C11—C2	111.5 (4)	N3—C20—H20	118.7
C13—C11—C2	110.3 (4)	C18—C17—C16	120.1 (7)
C12—C11—C2	109.5 (4)	C18—C17—H17	120.0
N3—C16—C17	122.2 (6)	C16—C17—H17	120.0
N3—C16—N2	119.8 (7)	C11—C12—H12A	109.5
C17—C16—N2	118.0 (6)	C11—C12—H12B	109.5
N1—C15—C4	121.9 (6)	H12A—C12—H12B	109.5
N1—C15—H15	119.1	C11—C12—H12C	109.5
C4—C15—H15	119.1	H12A—C12—H12C	109.5
C15—N1—N2	118.8 (6)	H12B—C12—H12C	109.5
C7—C9—H9A	109.5	C18—C19—C20	117.6 (6)
C7—C9—H9B	109.5	C18—C19—H19	121.2
H9A—C9—H9B	109.5	C20—C19—H19	121.2
C7—C9—H9C	109.5	C17—C18—C19	120.1 (6)
H9A—C9—H9C	109.5	C17—C18—H18	119.9
H9B—C9—H9C	109.5	C19—C18—H18	119.9

C5—C6—C1—O1	177.4 (4)	C15—C4—C3—C2	175.1 (5)
C7—C6—C1—O1	−2.6 (7)	C3—C2—C11—C14	−3.1 (7)
C5—C6—C1—C2	−1.4 (7)	C1—C2—C11—C14	179.9 (5)
C7—C6—C1—C2	178.6 (5)	C3—C2—C11—C13	−121.5 (5)
C1—C6—C5—C4	0.4 (7)	C1—C2—C11—C13	61.6 (6)
C7—C6—C5—C4	−179.6 (5)	C3—C2—C11—C12	115.8 (6)
O1—C1—C2—C3	−177.8 (4)	C1—C2—C11—C12	−61.1 (6)
C6—C1—C2—C3	1.0 (7)	C20—N3—C16—C17	2.1 (9)
O1—C1—C2—C11	−0.7 (7)	C20—N3—C16—N2	−177.6 (6)
C6—C1—C2—C11	178.1 (4)	C3—C4—C15—N1	−172.4 (6)
C5—C6—C7—C8	1.9 (7)	C5—C4—C15—N1	4.0 (8)
C1—C6—C7—C8	−178.1 (5)	C4—C15—N1—N2	177.9 (5)
C5—C6—C7—C10	121.7 (5)	N3—C16—N2—N1	166.7 (6)
C1—C6—C7—C10	−58.3 (6)	C17—C16—N2—N1	−13.1 (9)
C5—C6—C7—C9	−115.6 (5)	C15—N1—N2—C16	−175.4 (6)
C1—C6—C7—C9	64.4 (6)	C16—N3—C20—C19	−0.5 (9)
C6—C5—C4—C3	1.0 (7)	N3—C16—C17—C18	−2.5 (10)
C6—C5—C4—C15	−175.5 (5)	N2—C16—C17—C18	177.3 (6)
C1—C2—C3—C4	0.5 (7)	N3—C20—C19—C18	−0.8 (10)
C11—C2—C3—C4	−176.6 (5)	C16—C17—C18—C19	1.1 (10)
C5—C4—C3—C2	−1.5 (8)	C20—C19—C18—C17	0.5 (10)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2···N3ⁱ	0.86	2.23	3.062 (8)	162

Symmetry code: (i) −x+1/2, −y−1/2, −z+1.

Comparison of selected observed (X-ray data) and calculated (DFT) geometric parameters (Å, °) top

Parameter	X-ray	B3LYP/6-311G(d,p)
O1—C1	1.370 (6)	1.370
C15—N1	1.253 (7)	1.252
N3—C20	1.386 (8)	1.386
N1—N2	1.396 (7)	1.395
N3—C16	1.292 (8)	1.292
C16—N2—N1	122.6 (6)	122.67
C15—N1—N2	118.8 (6)	118.85
N1—C15—C4	121.9 (6)	121.88

Acknowledgements

The authors are grateful to the National Taras Shevchenko University, Department of Chemistry, Volodymyrska str. 64, 01601 Kyiv, Ukraine, for financial support, and to Dr Musheer Ahmad and Dr Graham Smith for helpful discussions.

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