Crystal structure, Hirshfeld surface analysis and inter­action energy and DFT studies of 4-[(prop-2-en-1-yl­oxy)meth­yl]-3,6-bis­(pyridin-2-yl)pyridazine

Filali, M.; Sebbar, N.K.; Hökelek, T.; Mague, J.T.; Chakroune, S.; Ben-Tama, A.; El Hadrami, E.M.

doi:10.1107/S2056989019011186

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ISSN: 2056-9890

Volume 75| Part 9| September 2019| Pages 1321-1326

https://doi.org/10.1107/S2056989019011186

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Crystal structure, Hirshfeld surface analysis and interaction energy and DFT studies of 4-[(prop-2-en-1-yloxy)methyl]-3,6-bis(pyridin-2-yl)pyridazine

Mouad Filali,^a Nada Kheira Sebbar,^b,^c ^* Tuncer Hökelek,^d Joel T. Mague,^e Said Chakroune,^a Abdessalam Ben-Tama ^a and El Mestafa El Hadrami ^a

^aLaboratoire de Chimie Organique Appliquée, Université Sidi Mohamed Ben Abdallah, Faculté des Sciences et Techniques, Route d'Immouzzer, BP 2202, Fez, Morocco, ^bLaboratoire de Chimie Bioorganique Appliquée, Faculté des Sciences, Université Ibn Zohr, Agadir, Morocco, ^cLaboratoire de Chimie Organique Hétérocyclique URAC 21, Pôle de Compétence Pharmacochimie, Av. Ibn Battouta, BP 1014, Faculté des Sciences, Université Mohammed V, Rabat, Morocco, ^dDepartment of Physics, Hacettepe University, 06800 Beytepe, Ankara, Turkey, and ^eDepartment of Chemistry, Tulane University, New Orleans, LA 70118, USA
^*Correspondence e-mail: nadouchsebbarkheira@gmail.com

Edited by A. J. Lough, University of Toronto, Canada (Received 29 July 2019; accepted 10 August 2019; online 20 August 2019)

The title compound, C₁₈H₁₆N₄O, consists of a 3,6-bis(pyridin-2-yl)pyridazine moiety linked to a 4-[(prop-2-en-1-yloxy)methyl] group. The pyridine-2-yl rings are oriented at a dihedral angle of 17.34 (4)° and are rotated slightly out of the plane of the pyridazine ring. In the crystal, C—H_Pyrd⋯N_Pyrdz (Pyrd = pyridine and Pyrdz = pyridazine) hydrogen bonds and C—H_Prpoxy⋯π (Prpoxy = prop-2-en-1-yloxy) interactions link the molecules, forming deeply corrugated layers approximately parallel to the bc plane and stacked along the a-axis direction. Hirshfeld surface analysis indicates that the most important contributions for the crystal packing are from H⋯H (48.5%), H⋯C/C⋯H (26.0%) and H⋯N/N⋯H (17.1%) contacts, hydrogen bonding and van der Waals interactions being the dominant interactions in the crystal packing. Computational chemistry indicates that in the crystal, the C—H_Pyrd⋯N_Pyrdz hydrogen-bond energy is 64.3 kJ mol⁻¹. 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. The HOMO–LUMO behaviour was elucidated to determine the energy gap.

Keywords: crystal structure; pyridine; pyridazine; π-stacking; DFT; Hirshfeld surface.

CCDC reference: 1946685

1. Chemical context

3,6-Di(pyridin-2-yl)pyridazine and its derivatives are aromatic heterocyclic organic compounds. The syntheses of 3,6-di(pyridin-2-yl)pyridazine and its derivatives based on polyheterocycles have attracted considerable attention from pharmacists in the last few decades as they function as important pharmacophores in medicinal chemistry and pharmacology (Filali et al., 2019 ). 5-[3,6-Di(pyridin-2-yl)pyridazine-4-yl]-2′-deoxyuridine-5′-O-triphosphate can be used as a potential substrate for fluorescence detection and imaging of DNA (Kore et al., 2015 ). The systems containing this moiety have also shown remarkable corrosion inhibitory (Khadiri et al., 2016 ). Heterocyclic molecules such as 3,6-bis(2′-pyridyl)-1,2,4,5-tetrazine have been used in transition-metal chemistry (Kaim & Kohlmann, 1987 ). It is a bidentate chelate ligand popular in coordination chemistry and complexes of a wide range of metals, including iridium and palladium (Tsukada et al., 2001 ). As a continuation of our research work devoted to the development of 3,6-di(pyridin-2-yl)pyridazine derivatives (Filali et al., 2019), we report herein the synthesis and the molecular and crystal structures along with the Hirshfeld surface analysis and the intermolecular interaction energies and density functional theory (DFT) calculations for 4-[(prop-2-en-1-yloxy)methyl]-3,6-bis(pyridin-2-yl)pyridazine.

2. Structural commentary

The title molecule contains two pyridine and one pyradizine rings (Fig. 1). The pyradizine ring of the 3,6-bis(pyridin-2-yl)pyridazine unit is linked to the 4-[(prop-2-en-1-yloxy)methyl] moiety (Fig. 1). Pyridazine ring A (N1/N2/C1–C4) is oriented at dihedral angles of 2.64 (3) and 15.06 (4)°, respectively, to the pyridine rings B (N3/C5–C9) and C (N4/C10–C14), while the dihedral angle between the two pyridine rings is 17.34 (4)°. Atom C15 is at a distance of 0.0405 (12) Å from the best plane of pyridazine ring. The 4-[(prop-2-en-1-yloxy)methyl] moiety is nearly co-planar with the pyradizine ring, as indicated by the O1—C15—C2—C3 torsion angle of −2.59 (14)°.

Figure 1
The molecular structure of the title compound with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.

3. Supramolecular features

In the crystal, C—H_Pyrd⋯N_Pyrdz (Pyrd = pyridine, Pyrdz = pyridazine) hydrogen bonds and C—H_Prpoxy⋯Cgⁱ [symmetry code: (i) 1 − x, 1 − y, 1 - z; Cg is the centroid of pyridine ring B (N3/C5–C9); Prpoxy = prop-2-en-1-yloxy] (Table 1) interactions link the molecules, forming deeply corrugated layers approximately parallel to the bc plane and stacked along the a-axis direction (Figs. 2 and 3).

Table 1
Hydrogen-bond geometry (Å, °)

Cg is the centroid of pyridine ring B (N3/C5—C9).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C8—H8⋯N1^vi	0.966 (16)	2.585 (16)	3.4104 (15)	143.4 (12)
C15—H15B⋯Cg^v	0.994 (15)	2.990 (15)	3.8760 (13)	149.0 (11)
Symmetry codes: (v) -x+1, -y+1, -z+1; (vi) $[-x+1, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ .

Figure 2
A partial packing diagram viewed along the a-axis direction with C—H_Pyrd⋯N_Pyrdz hydrogen bonds and C—H_Prpoxy⋯π interactions shown, respectively, as light blue and green dashed lines.

Figure 3
A partial packing diagram viewed along the c-axis direction with C—H_Pyrd⋯N_Pyrdz hydrogen bonds and C—H_Prpoxy⋯π interactions shown, respectively, as light-blue and green dashed lines.

4. Hirshfeld surface analysis

In order to visualize the intermolecular interactions, a Hirshfeld surface (HS) analysis (Hirshfeld, 1977 ; Spackman & Jayatilaka, 2009 ) was carried out by using CrystalExplorer17.5 (Turner et al., 2017 ). In the HS plotted over d_norm (Fig. 4), white areas indicate contacts with distances equal to the sum of van der Waals radii, and red and blue areas indicate distances shorter (in close contact) or longer (distinct contact) than the van der Waals radii (Venkatesan et al., 2016 ). The bright-red spots appearing near N1 and hydrogen atoms H8 and H15B indicate their roles as donors and/or acceptors; they also appear as blue and red regions corresponding to positive and negative potentials on the HS mapped over electrostatic potential (Spackman et al., 2008 ; Jayatilaka et al., 2005 ) shown in Fig. 5. The blue regions indicate positive electrostatic potential (hydrogen-bond donors), while the red regions indicate negative electrostatic potential (hydrogen-bond acceptors). The shape-index of the HS is a tool to visualize π–π stacking by the presence of adjacent red and blue triangles; if there are no adjacent red and/or blue triangles, then there are no π–π interactions. Fig. 6 clearly suggest that there are no π–π interactions in (I).

Figure 4
View of the three-dimensional Hirshfeld surface of the title compound plotted over d_norm in the range −0.1063 to 1.1444 a.u.

Figure 5
View of the three-dimensional Hirshfeld surface of the title compound plotted over electrostatic potential energy in the range −0.0500 to 0.0500 a.u. using the STO-3 G basis set at the Hartree–Fock level of theory. Hydrogen-bond donors and acceptors are shown as blue and red regions, respectively, around the atoms, corresponding to positive and negative potentials.

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

The overall two-dimensional fingerprint plot, Fig. 7a, and those delineated into H ⋯ H, H⋯C/C⋯H, H⋯N/N⋯H, C⋯C, H⋯O/O⋯H, O⋯C/C ⋯ O and C⋯N/N⋯C contacts (McKinnon et al., 2007 ) are illustrated in Fig. 7 b–h, respectively, together with their relative contributions to the Hirshfeld surface. The most important interaction is H⋯H (Table 2), contributing 48.5% to the overall crystal packing, which is reflected in Fig. 7b as widely scattered points of high density, due to the large hydrogen content of the molecule, with the tips at d_e + d_i ∼2.39 Å. In the presence of C—H⋯π interactions, the pair of characteristic wings in the fingerprint plot delineated into H⋯C/C⋯H contacts (26.0% contribution), Fig. 7c, has a pair of spikes with the tips at d_e + d_i = 2.72 Å. The pair of the scattered points of wings in the fingerprint plots delineated into H⋯N/N⋯H (17.1% contribution), Fig. 7d, has a symmetrical distribution of points with the edges at d_e + d_i = 2.50 Å. The C⋯C contacts, Fig. 7e, have an arrow-shaped distribution of points with the tip at d_e = d_i = 1.76 Å. The pair of characteristic wings in the fingerprint plot delineated into H⋯O/O⋯H contacts (1.7% contribution) Fig. 7f, has a pair of spikes with the tips at d_e + d_i = 2.82 Å. Finally, in the fingerprint plots delineated into C⋯O/O⋯C (1.3%) and C⋯N/N⋯C (1.2%) contacts, Fig. 7g and Fig. 7h, the tips are at d_e = d_i = 1.65 Å and 3.87 Å, respectively.

Table 2
Selected interatomic distances (Å)

O1⋯C11ⁱ	3.2992 (16)	C3⋯C11ⁱ	3.5866 (17)
O1⋯H3	2.232 (14)	C6⋯C12^iv	3.5808 (18)
O1⋯H11ⁱ	2.850 (16)	C8⋯C10^vi	3.5797 (17)
N1⋯C8ⁱⁱ	3.4105 (15)	C11⋯C15ⁱ	3.5633 (18)
N4⋯C15	2.7895 (16)	C1⋯H7ⁱⁱ	2.925 (17)
N1⋯H8ⁱⁱ	2.586 (15)	C6⋯H16B^v	2.933 (15)
N1⋯H11	2.441 (16)	C9⋯H15B^v	2.842 (15)
N1⋯H15Aⁱ	2.713 (14)	C18⋯H8^vii	2.920 (16)
N2⋯H18Bⁱⁱⁱ	2.86 (2)	H6⋯H9^viii	2.56 (2)
N2⋯H13^iv	2.744 (17)	H8⋯N1^vi	2.586 (16)
N2⋯H6	2.455 (15)	H11⋯H16Aⁱ	2.57 (2)
N3⋯H3	2.522 (14)	H12⋯C6^ix	2.886 (18)
N3⋯H15B^v	2.652 (15)	H12⋯H14^x	2.53 (3)
N4⋯H15A	2.632 (14)	H13⋯H18B^xi	2.55 (3)
N4⋯H15B	2.485 (14)	H15A⋯H16A	2.36 (2)
C1⋯C7ⁱⁱ	3.5853 (17)	H15B⋯H16B	2.38 (2)
C2⋯C10ⁱ	3.5420 (15)	H16A⋯H18A	2.33 (2)
Symmetry codes: (i) -x, -y+1, -z+1; (ii) $[-x+1, y-{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (iii) x, y, z+1; (iv) $[-x, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (v) -x+1, -y+1, -z+1; (vi) $[-x+1, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (vii) $[-x+1, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (viii) $[x, -y+{\script{3\over 2}}, z+{\script{1\over 2}}]$ ; (ix) $[-x, y-{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (x) $[x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (xi) $[-x, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Figure 7
The full two-dimensional fingerprint plots for the title compound, showing (a) all interactions, and delineated into (b) H⋯H, (c) H⋯C/C⋯H, (d) H⋯N/N⋯H, (e) C⋯C, (f) H⋯O/O⋯H, (g) C⋯O/O⋯C and (h) C ⋯ N/N⋯C interactions. The d_i and d_e values are the closest internal and external distances (in Å) from given points on the Hirshfeld surface.

The Hirshfeld surface representations with the function d_norm plotted onto the surface are shown for the H⋯H, H⋯C/C⋯H and H⋯N/N⋯H interactions in Fig. 8a--c, respectively.

Figure 8
The Hirshfeld surface representations with the function d_norm plotted onto the surface for (a) H⋯H, (b) H⋯C/C⋯H and (c) H⋯N/N⋯H interactions.

The Hirshfeld surface analysis confirms the importance of H-atom contacts in establishing the packing. The large number of H⋯H, H⋯C/C⋯H and H ⋯ N/N⋯H interactions suggest that van der Waals interactions and hydrogen bonding play the major roles in the crystal packing (Hathwar et al., 2015 ).

5. Interaction energy calculations

The intermolecular interaction energies were calculated using the CE–B3LYP/6–31G(d,p) energy model available in CrystalExplorer17.5 (Turner et al., 2017), where a cluster of molecules would need to be generated by applying crystallographic symmetry operations with respect to a selected central molecule within the radius of 3.8 Å by default (Turner et al., 2014 ). The total intermolecular energy (E_tot) is the sum of electrostatic (E_ele), polarization (E_pol), dispersion (E_dis) and exchange-repulsion (E_rep) energies (Turner et al., 2015 ) with scale factors of 1.057, 0.740, 0.871 and 0.618, respectively (Mackenzie et al., 2017 ). The hydrogen-bonding interaction energy (in kJ mol⁻¹) was calculated as −15.0 (E_ele), −3.2 (E_pol), −81.9 (E_dis), 40.9 (E_rep) and −64.3 (E_tot) for the C—H_Pyrd⋯N_Pyrdz hydrogen bond.

6. DFT calculations

The optimized structure of the title compound in the gas phase was generated theoretically via 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 ). The theoretical and experimental results were in good agreement (Table 3). The highest-occupied molecular orbital (HOMO), acting as an electron donor, and the lowest-unoccupied molecular orbital (LUMO), acting as an electron acceptor, are very important parameters for quantum chemistry. When the energy gap is small, the molecule is highly polarizable and has high chemical reactivity. The DFT calculations provide some important information on the reactivity and site selectivity of the molecular framework. E_HOMO and E_LUMO clarify the inevitable charge-exchange collaboration inside the studied material, and are given in Table 4 along with the electronegativity (χ), hardness (η), potential (μ), electrophilicity (ω) and softness (σ). The significance of η and σ is to evaluate both the reactivity and stability. The electron transition from the HOMO to the LUMO energy level is shown in Fig. 9. The HOMO and LUMO are localized in the plane extending from the whole 4-[(prop-2-en-1-yloxy)methyl]-3,6-bis(pyridin-2-yl)pyridazine ring. The energy band gap [ΔE = E_LUMO − E_HOMO] of the molecule is 4.1539 eV, and the frontier molecular orbital energies, E_HOMO and E_LUMO are −6.0597 and −1.9058 eV, respectively.

Table 3
Comparison of the selected (X-ray and DFT) geometric data (Å, °)

Bonds/angles	X-ray	B3LYP/6–311G(d,p)
O1—C15	1.4224 (13)	1.45001
O1—C16	1.4237 (14)	1.45647
N1—N2	1.3322 (13)	1.33754
N1—C1	1.3434 (15)	1.36030
N2—C4	1.3386 (14)	1.35694
N3—C9	1.3370 (15)	1.34713
N3—C5	1.3445 (14)	1.35667
N4—C10	1.3362 (15)	1.35644
N4—C14	1.3400 (17)	1.34940
C15—O1—C16	111.09 (9)	112.34477
N2—N1—C1	121.37 (9)	121.70569
N1—N2—C4	119.14 (9)	119.30129
C9—N3—C5	117.07 (10)	118.58051
C10—N4—C14	117.42 (11)	119.00361
N1—C1—C2	121.82 (10)	121.25910
N1—C1—C10	113.24 (10)	113.37034
N2—C4—C3	122.25 (10)	121.78580
N2—C4—C5	115.80 (10)	116.28262
C3—C4—C5	121.95 (10)	121.93158
N3—C5—C6	122.61 (10)	122.07926
N3—C5—C4	116.15 (10)	116.59443

Table 4
Calculated energies for the title compound

Total energy, TE (eV)	−26922.3681
E_HOMO (eV)	−6.0597
E_LUMO (eV)	−1.9058
Energy gap, ΔE (eV)	4.1539
Dipole moment μ (Debye)	1.6276
Ionization potential, I (eV)	6.0597
Electron affinity, A	1.9058
Electronegativity, χ	3.9827
Hardness, η	2.0769
Electrophilicity index, ω	3.8186
Softness, σ	0.4815
Fraction of electrons transferred, ΔN	0.7264

Figure 9
The energy band gap of the title compound.

7. Database survey

Silver(I) complexes supported by 3,6-di(pyridin-2-yl)pyridazine ligands have been reported (Constable et al., 2008 ). Three other metal complexes including 3,6-di(pyridin-2-yl)pyridazine have also been reported, namely aquabis[3,6-bis(pyridin-2-yl)pyridazine-κ²N¹,N⁶]copper(II) bis(trifluoromethanesulfonate) (Showrilu et al., 2017 ), tetrakis[μ-3,6-di(pyridin-2-yl)pyridazine]bis(μ-hydroxo)bis(μ-aqua)tetranickel(II) hexakis(nitrate) tetradecahydrate (Marino et al., 2019 ) and catena-[[μ₂-3,6-di(pyridin-2-yl)pyridazine]bis(μ₂-azido)dizaidodicopper monohydrate] (Mastropietro et al., 2013 ).

8. Synthesis and crystallization

THF (20 ml), [3,6-di(pyridin-2-yl)pyridazin-4-yl]methanol (3 mmol), 1.8 eq. of NaH and 0.04 eq. of 18-crown ether A were added to a conical flask and stirred for 10 min at room temperature. Then 1.2 eq of propargyl allyl chloride was added to the reaction mixture and stirred for 48 h. The solvent was then evaporated off and the required organic compound was obtained by liquid–liquid extraction using dichloromethane. The organic phase was dried with sodium sulfate (Na₂SO₄), and then evaporated. The product obtained was separated by chromatography on a column of silica gel. The isolated solid was recrystallized from hexane-dichloromethane (1:1) to afford colourless crystals (yield: 87%, m.p. 376 K).

9. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 5. The hydrogen atoms were located in a difference-Fourier map and refined freely.

Table 5
Experimental details

Crystal data
Chemical formula	C₁₈H₁₆N₄O
M_r	304.35
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	150
a, b, c (Å)	8.9420 (2), 15.1130 (3), 11.5829 (3)
β (°)	100.132 (1)
V (Å³)	1540.91 (6)
Z	4
Radiation type	Cu Kα
μ (mm⁻¹)	0.68
Crystal size (mm)	0.26 × 0.24 × 0.08

Data collection
Diffractometer	Bruker D8 VENTURE PHOTON 100 CMOS
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.86, 0.95
No. of measured, independent and observed [I > 2σ(I)] reflections	11678, 3051, 2688
R_int	0.029
(sin θ/λ)_max (Å⁻¹)	0.625

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.037, 0.101, 1.04
No. of reflections	3051
No. of parameters	273
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.18, −0.15
Computer programs: APEX3 and SAINT (Bruker, 2016 ), SAINT (Bruker, 2016), SHELXT (Sheldrick, 2015a ), SHELXL2018 (Sheldrick, 2015b ), DIAMOND (Brandenburg & Putz, 2012 ) and SHELXTL (Sheldrick, 2008 ).

Supporting information

CCDC reference: 1946685

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S2056989019011186/lh5915sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989019011186/lh5915Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989019011186/lh5915Isup3.cdx

Supporting information file. DOI: https://doi.org/10.1107/S2056989019011186/lh5915Isup4.cml

checkCIF report

Computing details top

Data collection: APEX3 (Bruker, 2016); cell refinement: SAINT (Bruker, 2016); data reduction: SAINT (Bruker, 2016); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: DIAMOND (Brandenburg & Putz, 2012); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

4-[(Prop-2-en-1-yloxy)methyl]-3,6-bis(pyridin-2-yl)pyridazine top

Crystal data top

C₁₈H₁₆N₄O	F(000) = 640
M_r = 304.35	D_x = 1.312 Mg m⁻³
Monoclinic, P2₁/c	Cu Kα radiation, λ = 1.54178 Å
a = 8.9420 (2) Å	Cell parameters from 9267 reflections
b = 15.1130 (3) Å	θ = 4.9–74.5°
c = 11.5829 (3) Å	µ = 0.68 mm⁻¹
β = 100.132 (1)°	T = 150 K
V = 1540.91 (6) Å³	Plate, colourless
Z = 4	0.26 × 0.24 × 0.08 mm

Data collection top

Bruker D8 VENTURE PHOTON 100 CMOS diffractometer	3051 independent reflections
Radiation source: INCOATEC IµS micro-focus source	2688 reflections with I > 2σ(I)
Mirror monochromator	R_int = 0.029
Detector resolution: 10.4167 pixels mm^-1	θ_max = 74.5°, θ_min = 4.9°
ω scans	h = −10→10
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	k = −18→18
T_min = 0.86, T_max = 0.95	l = −14→13
11678 measured reflections

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F² > 2σ(F²)] = 0.037	All H-atom parameters refined
wR(F²) = 0.101	w = 1/[σ²(F_o²) + (0.0534P)² + 0.3637P] where P = (F_o² + 2F_c²)/3
S = 1.04	(Δ/σ)_max < 0.001
3051 reflections	Δρ_max = 0.18 e Å⁻³
273 parameters	Δρ_min = −0.15 e Å⁻³
0 restraints	Extinction correction: SHELXL2018 (Sheldrick, 2015b), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: dual space	Extinction coefficient: 0.0046 (5)

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.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > 2sigma(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² 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 (Å²) top

	x	y	z	U_iso*/U_eq
O1	0.27225 (10)	0.47749 (5)	0.30640 (7)	0.0319 (2)
N1	0.19512 (11)	0.50876 (6)	0.70191 (8)	0.0283 (2)
N2	0.27872 (11)	0.58215 (6)	0.70850 (8)	0.0283 (2)
N3	0.49183 (11)	0.71463 (6)	0.53716 (8)	0.0299 (2)
N4	0.07708 (13)	0.31558 (7)	0.53457 (10)	0.0370 (3)
C1	0.17076 (12)	0.45900 (7)	0.60429 (10)	0.0249 (2)
C2	0.23110 (12)	0.48225 (7)	0.50338 (10)	0.0244 (2)
C3	0.31696 (12)	0.55846 (7)	0.51158 (10)	0.0257 (2)
H3	0.3616 (15)	0.5785 (9)	0.4416 (12)	0.030 (3)*
C4	0.33924 (12)	0.60672 (7)	0.61566 (9)	0.0244 (2)
C5	0.43278 (12)	0.68871 (7)	0.63070 (10)	0.0250 (2)
C6	0.45861 (13)	0.73441 (8)	0.73683 (10)	0.0292 (3)
H6	0.4125 (17)	0.7131 (10)	0.8002 (13)	0.040 (4)*
C7	0.54897 (14)	0.80913 (8)	0.74716 (11)	0.0329 (3)
H7	0.5668 (18)	0.8438 (11)	0.8229 (15)	0.049 (4)*
C8	0.61156 (14)	0.83614 (8)	0.65191 (11)	0.0326 (3)
H8	0.6740 (17)	0.8887 (10)	0.6564 (14)	0.042 (4)*
C9	0.57918 (14)	0.78700 (8)	0.54977 (11)	0.0323 (3)
H9	0.6207 (17)	0.8041 (10)	0.4814 (14)	0.043 (4)*
C10	0.07702 (12)	0.37891 (7)	0.61505 (10)	0.0269 (3)
C11	−0.00417 (14)	0.37100 (9)	0.70670 (11)	0.0346 (3)
H11	−0.0048 (18)	0.4190 (11)	0.7619 (14)	0.044 (4)*
C12	−0.08744 (15)	0.29497 (9)	0.71477 (12)	0.0404 (3)
H12	−0.147 (2)	0.2897 (11)	0.7774 (16)	0.058 (5)*
C13	−0.08794 (16)	0.22904 (9)	0.63254 (12)	0.0405 (3)
H13	−0.1415 (19)	0.1766 (12)	0.6368 (14)	0.050 (4)*
C14	−0.00414 (18)	0.24243 (9)	0.54512 (13)	0.0440 (3)
H14	−0.0035 (19)	0.1969 (11)	0.4852 (15)	0.052 (5)*
C15	0.20351 (13)	0.43087 (8)	0.39007 (10)	0.0279 (3)
H15A	0.0898 (16)	0.4252 (9)	0.3600 (12)	0.032 (3)*
H15B	0.2466 (16)	0.3702 (10)	0.4016 (12)	0.036 (4)*
C16	0.23624 (15)	0.43750 (8)	0.19364 (10)	0.0321 (3)
H16A	0.1233 (17)	0.4420 (9)	0.1637 (13)	0.037 (4)*
H16B	0.2670 (16)	0.3739 (10)	0.1992 (13)	0.038 (4)*
C17	0.32018 (17)	0.48569 (9)	0.11329 (11)	0.0377 (3)
H17	0.436 (2)	0.4884 (12)	0.1409 (17)	0.065 (5)*
C18	0.2574 (2)	0.51972 (11)	0.01194 (13)	0.0497 (4)
H18A	0.150 (2)	0.5087 (12)	−0.0128 (17)	0.065 (6)*
H18B	0.314 (2)	0.5515 (13)	−0.0442 (18)	0.068 (5)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0418 (5)	0.0330 (4)	0.0225 (4)	−0.0060 (3)	0.0099 (3)	−0.0033 (3)
N1	0.0316 (5)	0.0278 (5)	0.0259 (5)	−0.0019 (4)	0.0065 (4)	0.0011 (4)
N2	0.0321 (5)	0.0283 (5)	0.0251 (5)	−0.0025 (4)	0.0070 (4)	0.0001 (4)
N3	0.0351 (5)	0.0306 (5)	0.0249 (5)	−0.0051 (4)	0.0079 (4)	−0.0004 (4)
N4	0.0503 (7)	0.0280 (5)	0.0348 (6)	−0.0061 (4)	0.0129 (5)	−0.0010 (4)
C1	0.0243 (5)	0.0250 (5)	0.0252 (6)	0.0039 (4)	0.0035 (4)	0.0027 (4)
C2	0.0249 (5)	0.0246 (5)	0.0236 (6)	0.0045 (4)	0.0034 (4)	0.0014 (4)
C3	0.0272 (5)	0.0272 (5)	0.0230 (6)	0.0019 (4)	0.0051 (4)	0.0013 (4)
C4	0.0244 (5)	0.0259 (5)	0.0229 (5)	0.0027 (4)	0.0038 (4)	0.0020 (4)
C5	0.0243 (5)	0.0270 (5)	0.0235 (6)	0.0023 (4)	0.0034 (4)	0.0015 (4)
C6	0.0302 (6)	0.0339 (6)	0.0239 (6)	−0.0026 (5)	0.0059 (4)	−0.0009 (4)
C7	0.0361 (6)	0.0348 (6)	0.0274 (6)	−0.0041 (5)	0.0044 (5)	−0.0053 (5)
C8	0.0350 (6)	0.0297 (6)	0.0325 (7)	−0.0060 (5)	0.0047 (5)	−0.0006 (5)
C9	0.0381 (6)	0.0325 (6)	0.0277 (6)	−0.0065 (5)	0.0089 (5)	0.0015 (5)
C10	0.0264 (5)	0.0262 (5)	0.0274 (6)	0.0024 (4)	0.0026 (4)	0.0042 (4)
C11	0.0336 (6)	0.0361 (6)	0.0355 (7)	−0.0049 (5)	0.0101 (5)	−0.0016 (5)
C12	0.0378 (7)	0.0455 (7)	0.0399 (7)	−0.0096 (6)	0.0121 (6)	0.0032 (6)
C13	0.0434 (7)	0.0338 (7)	0.0437 (8)	−0.0110 (6)	0.0059 (6)	0.0055 (5)
C14	0.0603 (9)	0.0310 (6)	0.0424 (8)	−0.0107 (6)	0.0140 (6)	−0.0031 (6)
C15	0.0320 (6)	0.0270 (6)	0.0257 (6)	−0.0007 (4)	0.0079 (5)	−0.0004 (4)
C16	0.0412 (7)	0.0299 (6)	0.0254 (6)	0.0005 (5)	0.0066 (5)	−0.0052 (4)
C17	0.0486 (8)	0.0373 (7)	0.0293 (7)	0.0008 (6)	0.0131 (6)	−0.0040 (5)
C18	0.0689 (11)	0.0476 (8)	0.0355 (8)	0.0083 (7)	0.0170 (7)	0.0059 (6)

Geometric parameters (Å, º) top

O1—C15	1.4224 (13)	C8—C9	1.3836 (17)
O1—C16	1.4237 (14)	C8—H8	0.966 (16)
N1—N2	1.3322 (13)	C9—H9	0.968 (15)
N1—C1	1.3434 (15)	C10—C11	1.3926 (17)
N2—C4	1.3386 (14)	C11—C12	1.3813 (18)
N3—C9	1.3370 (15)	C11—H11	0.968 (17)
N3—C5	1.3445 (14)	C12—C13	1.378 (2)
N4—C10	1.3362 (15)	C12—H12	0.974 (17)
N4—C14	1.3400 (17)	C13—C14	1.377 (2)
C1—C2	1.4151 (15)	C13—H13	0.931 (18)
C1—C10	1.4901 (15)	C14—H14	0.978 (17)
C2—C3	1.3782 (15)	C15—H15A	1.019 (14)
C2—C15	1.5075 (15)	C15—H15B	0.994 (15)
C3—C4	1.3930 (15)	C16—C17	1.4851 (18)
C3—H3	1.012 (14)	C16—H16A	1.011 (15)
C4—C5	1.4880 (15)	C16—H16B	0.999 (15)
C5—C6	1.3934 (16)	C17—C18	1.314 (2)
C6—C7	1.3813 (17)	C17—H17	1.03 (2)
C6—H6	0.959 (15)	C18—H18A	0.96 (2)
C7—C8	1.3836 (17)	C18—H18B	1.01 (2)
C7—H7	1.010 (17)

O1···C11ⁱ	3.2992 (16)	C3···C11ⁱ	3.5866 (17)
O1···H3	2.232 (14)	C6···C12^iv	3.5808 (18)
O1···H11ⁱ	2.850 (16)	C8···C10^vi	3.5797 (17)
N1···C8ⁱⁱ	3.4105 (15)	C11···C15ⁱ	3.5633 (18)
N4···C15	2.7895 (16)	C1···H7ⁱⁱ	2.925 (17)
N1···H8ⁱⁱ	2.586 (15)	C6···H16B^v	2.933 (15)
N1···H11	2.441 (16)	C9···H15B^v	2.842 (15)
N1···H15Aⁱ	2.713 (14)	C18···H8^vii	2.920 (16)
N2···H18Bⁱⁱⁱ	2.86 (2)	H6···H9^viii	2.56 (2)
N2···H13^iv	2.744 (17)	H8···N1^vi	2.586 (16)
N2···H6	2.455 (15)	H11···H16Aⁱ	2.57 (2)
N3···H3	2.522 (14)	H12···C6^ix	2.886 (18)
N3···H15B^v	2.652 (15)	H12···H14^x	2.53 (3)
N4···H15A	2.632 (14)	H13···H18B^xi	2.55 (3)
N4···H15B	2.485 (14)	H15A···H16A	2.36 (2)
C1···C7ⁱⁱ	3.5853 (17)	H15B···H16B	2.38 (2)
C2···C10ⁱ	3.5420 (15)	H16A···H18A	2.33 (2)

C15—O1—C16	111.09 (9)	N4—C10—C1	117.02 (10)
N2—N1—C1	121.37 (9)	C11—C10—C1	120.65 (10)
N1—N2—C4	119.14 (9)	C12—C11—C10	118.85 (12)
C9—N3—C5	117.07 (10)	C12—C11—H11	120.9 (9)
C10—N4—C14	117.42 (11)	C10—C11—H11	120.3 (10)
N1—C1—C2	121.82 (10)	C13—C12—C11	119.41 (12)
N1—C1—C10	113.24 (10)	C13—C12—H12	121.3 (10)
C2—C1—C10	124.93 (10)	C11—C12—H12	119.3 (10)
C3—C2—C1	116.06 (10)	C14—C13—C12	117.79 (12)
C3—C2—C15	119.63 (10)	C14—C13—H13	121.0 (10)
C1—C2—C15	124.29 (10)	C12—C13—H13	121.2 (10)
C2—C3—C4	119.36 (10)	N4—C14—C13	124.22 (13)
C2—C3—H3	119.3 (8)	N4—C14—H14	116.4 (10)
C4—C3—H3	121.3 (8)	C13—C14—H14	119.4 (10)
N2—C4—C3	122.25 (10)	O1—C15—C2	108.29 (9)
N2—C4—C5	115.80 (10)	O1—C15—H15A	109.5 (8)
C3—C4—C5	121.95 (10)	C2—C15—H15A	110.0 (8)
N3—C5—C6	122.61 (10)	O1—C15—H15B	110.2 (8)
N3—C5—C4	116.15 (10)	C2—C15—H15B	111.0 (8)
C6—C5—C4	121.24 (10)	H15A—C15—H15B	107.9 (11)
C7—C6—C5	119.03 (11)	O1—C16—C17	108.01 (10)
C7—C6—H6	122.1 (9)	O1—C16—H16A	109.7 (8)
C5—C6—H6	118.8 (9)	C17—C16—H16A	109.7 (8)
C6—C7—C8	118.99 (11)	O1—C16—H16B	109.5 (9)
C6—C7—H7	120.0 (9)	C17—C16—H16B	110.4 (8)
C8—C7—H7	121.0 (9)	H16A—C16—H16B	109.5 (12)
C9—C8—C7	118.05 (11)	C18—C17—C16	124.63 (15)
C9—C8—H8	121.2 (9)	C18—C17—H17	120.8 (11)
C7—C8—H8	120.7 (9)	C16—C17—H17	114.5 (11)
N3—C9—C8	124.25 (11)	C17—C18—H18A	116.3 (12)
N3—C9—H9	115.5 (9)	C17—C18—H18B	125.0 (12)
C8—C9—H9	120.3 (9)	H18A—C18—H18B	118.4 (16)
N4—C10—C11	122.32 (11)

C1—N1—N2—C4	0.15 (16)	C5—C6—C7—C8	−0.24 (18)
N2—N1—C1—C2	−0.61 (16)	C6—C7—C8—C9	0.57 (18)
N2—N1—C1—C10	178.92 (9)	C5—N3—C9—C8	−0.14 (18)
N1—C1—C2—C3	0.42 (15)	C7—C8—C9—N3	−0.4 (2)
C10—C1—C2—C3	−179.06 (10)	C14—N4—C10—C11	−0.41 (18)
N1—C1—C2—C15	−177.88 (10)	C14—N4—C10—C1	178.51 (11)
C10—C1—C2—C15	2.64 (17)	N1—C1—C10—N4	−164.56 (10)
C1—C2—C3—C4	0.20 (15)	C2—C1—C10—N4	14.96 (16)
C15—C2—C3—C4	178.58 (10)	N1—C1—C10—C11	14.38 (15)
N1—N2—C4—C3	0.49 (16)	C2—C1—C10—C11	−166.10 (11)
N1—N2—C4—C5	−179.18 (9)	N4—C10—C11—C12	0.07 (19)
C2—C3—C4—N2	−0.66 (16)	C1—C10—C11—C12	−178.81 (11)
C2—C3—C4—C5	179.00 (10)	C10—C11—C12—C13	0.1 (2)
C9—N3—C5—C6	0.51 (17)	C11—C12—C13—C14	0.0 (2)
C9—N3—C5—C4	−178.47 (10)	C10—N4—C14—C13	0.6 (2)
N2—C4—C5—N3	−178.91 (10)	C12—C13—C14—N4	−0.4 (2)
C3—C4—C5—N3	1.41 (15)	C16—O1—C15—C2	−173.64 (9)
N2—C4—C5—C6	2.09 (15)	C3—C2—C15—O1	−2.59 (14)
C3—C4—C5—C6	−177.59 (10)	C1—C2—C15—O1	175.66 (9)
N3—C5—C6—C7	−0.32 (18)	C15—O1—C16—C17	−176.11 (10)
C4—C5—C6—C7	178.61 (10)	O1—C16—C17—C18	−126.92 (14)

Symmetry codes: (i) −x, −y+1, −z+1; (ii) −x+1, y−1/2, −z+3/2; (iii) x, y, z+1; (iv) −x, y+1/2, −z+3/2; (v) −x+1, −y+1, −z+1; (vi) −x+1, y+1/2, −z+3/2; (vii) −x+1, y−1/2, −z+1/2; (viii) x, −y+3/2, z+1/2; (ix) −x, y−1/2, −z+3/2; (x) x, −y+1/2, z+1/2; (xi) −x, y−1/2, −z+1/2.

Hydrogen-bond geometry (Å, º) top

Cg is the centroid of pyridine ring B (N3/C5—C9).

D—H···A	D—H	H···A	D···A	D—H···A
C8—H8···N1^vi	0.966 (16)	2.585 (16)	3.4104 (15)	143.4 (12)
C15—H15B···Cg^v	0.994 (15)	2.990 (15)	3.8760 (13)	149.0 (11)

Symmetry codes: (v) −x+1, −y+1, −z+1; (vi) −x+1, y+1/2, −z+3/2.

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

Bonds/angles	X-ray	B3LYP/6-311G(d,p)
O1—C15	1.4224 (13)	1.45001
O1—C16	1.4237 (14)	1.45647
N1—N2	1.3322 (13)	1.33754
N1—C1	1.3434 (15)	1.36030
N2—C4	1.3386 (14)	1.35694
N3—C9	1.3370 (15)	1.34713
N3—C5	1.3445 (14)	1.35667
N4—C10	1.3362 (15)	1.35644
N4—C14	1.3400 (17)	1.34940
C15—O1—C16	111.09 (9)	112.34477
N2—N1—C1	121.37 (9)	121.70569
N1—N2—C4	119.14 (9)	119.30129
C9—N3—C5	117.07 (10)	118.58051
C10—N4—C14	117.42 (11)	119.00361
N1—C1—C2	121.82 (10)	121.25910
N1—C1—C10	113.24 (10)	113.37034
N2—C4—C3	122.25 (10)	121.78580
N2—C4—C5	115.80 (10)	116.28262
C3—C4—C5	121.95 (10)	121.93158
N3—C5—C6	122.61 (10)	122.07926
N3—C5—C4	116.15 (10)	116.59443

Calculated energies for the title compound top

Total energy, TE (eV)	-26922.3681
E_HOMO (eV)	-6.0597
E_LUMO (eV)	-1.9058
Energy gap, ΔE (eV)	4.1539
Dipole moment µ (Debye)	1.6276
Ionization potential, I (eV)	6.0597
Electron affinity, A	1.9058
Electronegativity, χ	3.9827
Hardness, η	2.0769
Electrophilicity index, ω	3.8186
Softness, σ	0.4815
Fraction of electrons transferred, ΔN	0.7264

Funding information

NSF–MRI grant No. 1228232 for the purchase of the diffractometer and Tulane University for support of the Tulane Crystallography Laboratory are gratefully acknowledged. TH is grateful to the Hacettepe University Scientific Research Project Unit (grant No. 013 D04 602 004).

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