A second monoclinic polymorph of 2,3-di­phenyl­pyrazine

Albishri, A.K.; Eltayeb, N.E.; Lasri, J.; Hökelek, T.; McKay, A.P.

doi:10.1107/S2056989026000460

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ISSN: 2056-9890

Volume 82| Part 2| February 2026| Pages 194-197

https://doi.org/10.1107/S2056989026000460

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A second monoclinic polymorph of 2,3-diphenylpyrazine

Abdulkarim K. Albishri,^a Naser E. Eltayeb,^b,^c Jamal Lasri,^b ^* Tuncer Hökelek ^d and Aidan P. McKay ^e

^aDepartment of Chemistry, College of Science and Arts, King Abdulaziz University, Rabigh 21911, Saudi Arabia, ^bDepartment of Chemistry, Rabigh College of Science and Arts, King Abdulaziz University, Jeddah 21589, Saudi Arabia, ^cDepartment of Chemistry, Faculty of Pure and Applied Sciences, International University of Africa, Khartoum 2469, Sudan, ^dDepartment of Physics, Hacettepe University, 06800 Beytepe, Ankara, Türkiye, and ^eEaStCHEM School of Chemistry, University of St Andrews, Fife, KY16 9ST, United Kingdom
^*Correspondence e-mail: [email protected]

Edited by W. T. A. Harrison, University of Aberdeen, United Kingdom (Received 3 December 2025; accepted 18 January 2026; online 23 January 2026)

The title compound, C₁₆H₁₂N₂ (I), crystallizes in the space group P2₁/c with one molecule in the asymmetric unit, in which the dihedral angles between the planes of the pyrazine ring and pendant phenyl rings are 53.12 (3) and 33.28 (3)°. In the crystal, pairwise C—H⋯N hydrogen bonds link the molecules into centrosymmetric dimers and aromatic π–π stacking interactions between the pyrazine rings of adjacent molecules and C—H⋯π interactions help to consolidatate the packing. Compound I is a polymorph of the previously reported form of 2,3-diphenylpyrazine [Kitano et al. (1983 ). Acta Cryst. C39, 136–139], which crystallizes in the space group C2/c with two molecules in the asymmetric unit. The Hirshfeld surfaces and energy frameworks of the two polymorphs are compared and the bonding modes of the molecules as ligands are surveyed.

Keywords: 2,3-diphenylpyrazine; crystal structure; hydrogen bonding; π-stacking; Hirshfeld surface.

CCDC reference: 2524118

1. Chemical context

The title compound I belongs to the class of organic compounds known as pyrazines or 1,4-diazines (Mason, 1887 ; Ohta et al., 1982 ). Pyrazine derivatives are of interest due to their pharmaceutical activities and natural occurence (Sammes, 1975 ; Cheeseman & Werstiuk, 1972 ). The syntheses and reactivities of pyrazine analogues have been investigated by Akita & Ohta (1982 ). Currently, our research focuses on the syntheses, reactivities and anticancer activities of a variety of cyclic and acyclic imine (C=N)-type compounds (e.g. Eltayeb et al., 2025 ) and the crystal structure determination of I was undertaken as part of these studies. Compound I is a polymorph of the previously reported form of 2,3-diphenylpyrazine (Kitano et al., 1983) with Cambridge Structural Database (CSD; Groom et al., 2016 ) refcode BOHPOD in the space group C2/c with two molecules in the asymmetric unit.

2. Structural commentary

Compound I crystallizes in the space group P2₁/c with one molecule in the asymmetric unit (Fig. 1). It contains a pyrazine ring, A (N1/N4/C2–C6), and pendant phenyl rings, B (C7–C12) and C (C13–C18), oriented at dihedral angles of A/B = 53.12 (3)°, A/C = 33.28 (3)° and B/C = 64.72 (3)°. The B and C rings are rotated in the same sense from the A ring plane due to steric hinderence between them and the C7—C2—C3—C13 torsion angle is −12.78 (16)°. The pyrazine ring in I is distinctly twisted, with an r.m.s. deviation of 0.043 Å for the six atoms and C6—N1—C2—C3 and C6—C5—N4—C3 torsion angles of 4.82 (15) and 2.75 (16)°, respectively.

Figure 1
The molecular structure of I, showing displacement ellipsoids at the 50% probability level.

3. Supramolecular features

In the crystal of I, pairwise C6—H6⋯N1ⁱ hydrogen bonds (Table 1) link the molecules into centrosymmetric dimers (Fig. 2) enclosing R₂²(6) loops. Aromatic π–π stacking interactions between the pyrazine rings of adjacent molecules, with an inter-centroid distance of 3.5711 (6) Å (slippage = 1.213 Å), and C—H⋯π interactions (Table 1) help to consolidate the crystal packing. In polymorph BOPHOD, only directional C—H⋯π interactions are present and the densities of I and BOPHOD of 1.278 and 1.233 Mg m⁻³, respectively, suggest that I is the more stable.

Table 1
Hydrogen-bond geometry (Å, °)

Cg2 and Cg3 are the centroids of the C7–C12 and C13–C18 rings, respectively.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C6—H6⋯N1ⁱ	0.95	2.52	3.3740 (15)	149
C12—H12⋯Cg3ⁱⁱ	0.95	2.97	3.7734 (12)	143
C16—H16⋯Cg2ⁱⁱⁱ	0.95	2.99	3.8974 (13)	159
Symmetry codes: (i) ; (ii) ; (iii) .

Figure 2
A partial packing diagram of I, showing an inversion dimer linked by pairwise C—H⋯N hydrogen bonds (dashed lines). The other H atoms have been omitted for clarity.

4. Hirshfeld surface analysis

Hirshfeld surface analyses for I and II {catena-poly[[(μ₂-2,3-diphenylpyrazine)silver(I)] tetrafluoroborate nitromethane solvate]; CSD refcode EQOYIS; Schultheiss et al., 2003 } were carried out using CrystalExplorer (Version 17.5; Spackman et al., 2021 ; Spackman et al., 2008 ; McKinnon et al., 2007 ; Turner et al., 2015 ). The Hirshfeld surface for I is shown in Fig. 3, where the bright-red spots correspond to the respective donors and acceptors noted above. The Hirshfeld surfaces for the two molecules in BOHPOD are shown in Figs. S1(a) and S1(b) in the supporting information. The contact-type percentages from the two-dimensional fingerprint plot for I (Fig. 4) and II (Figs. S3) are listed in Table 2. These data show that the contact percentages are similar, with H⋯H and C⋯H/H⋯C dominating in each case.

Table 2
Comparison of the contact-type percentages for title compound I and BOHPOD, where the asymmetric unit contains two crystallographically independent molecules, A and B

Contact	I	BOHPOD (A)	BOHPOD (B)
H⋯H	54.0	47.7	55.1
H⋯C/C⋯H	30.0	34.1	31.6
H⋯N/N⋯H	9.7	14.7	12.2
C⋯C	2.7	1.5	0.8
N⋯N	1.8	0.1	0.0
C⋯N/N⋯C	1.7	1.9	0.3

Figure 3
The three-dimensional Hirshfeld surface of I plotted over d_norm in the range from −0.17 to 1.34 a.u.

Figure 4
Two-dimensional fingerprint plots for I, showing (a) all interactions, and delineated into the different contact types (b)–(g).

5. Interaction energy calculations and energy frameworks

The CE-B3LYP/6-31G(d,p) energy model available in CrystalExplorer was used to calculate the intermolecular interaction energies in I. The interaction energies (in kJ mol⁻¹) were calculated to be −7.6 (E_ele), −2.4 (E_pol), −40.4 (E_dis), +27.0 (E_rep) and −28.3 (E_tot) for the C6—H6⋯N1ⁱ hydrogen-bond interaction. Energy frameworks were constructed for E_ele (red cylinders), E_dis (green cylinders) and E_tot (blue cylinders) [Figs. 5(a), 5(b) and 5(c)], and their evaluation indicate that the stabilization is dominated by dispersion energy contributions in the crystal structure of I. A similar calculation for BOHPOD (Figs. S4 and S5) indicates that the stabilization is also dominated by the dispersion energy contributions.

Figure 5
The energy frameworks for a cluster of molecules of I, viewed down the a-axis direction, showing (a) electrostatic energy, (b) dispersion energy and (c) total energy diagrams. The cylindrical radius is proportional to the relative strength of the corresponding energies and they were adjusted to the same scale factor of 80 with a cut-off value of 5 kJ mol⁻¹ within 2 × 2 × 2 unit cells.

6. Database survey

A survey of the Cambridge Structural Database (CSD, July 2025 update; Groom et al., 2016) revealed several structures where 2,3-diphenylpyrazine can act as a ligand, either N-bonded or N,C-bonded, or as an anion. They include refcode BOHPOD (Kitano et al., 1983), II (EQOYIS; Schultheiss et al., 2003), III (HABSAI; Hrovat et al., 2020 ), IV (IFELOX; Zhu et al., 2018 ), V (IQUJAJ; Shi et al., 2025 ), VI (KAQHES; Luo et al., 2017 ), VII (LEXDAW; Tian et al., 2018 ), VIII (LEXDEA; Tian et al., 2018), IX (LEXDIE; Tian et al., 2018), X (LEXFEC; Tian et al., 2018), XI (LEXFIG; Tian et al., 2018), XII (REJLAW; Tian et al., 2016 ), XIII (REJLIE; Tian et al., 2016) and XIV (VIBXAF; Steel & Caygill, 1990 ). The dihedral angles between the central and pendant rings for these structures are given in the supporting information.

7. Synthesis and crystallization

Ethylenediamine (60.1 mg, 1.0 mmol) was added to a solution of benzil (210.2 mg, 1.0 mmol) in ethanol (50 ml). The reaction mixture was refluxed for 4 h, cooled to room temperature for precipitation and then filtered. Yellow crystals of I suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution (yield 88%; m.p. 115–116 °C). Elemental analysis calculated (%) for C₁₆H₁₂N₂: C 82.73, H 5.21, N 12.06; found: C 82.75, H 5.19, N 12.08. The report of Kitano et al. (1983) unfortunately does not mention the synthesis or (re)crystallization conditions for II.

8. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3. The H-atom positions were calculated geometrically (C—H = 0.95 Å) and refined using a riding model by applying the constraint U_iso(H) = 1.2U_eq(C).

Table 3
Experimental details

Crystal data
Chemical formula	C₁₆H₁₂N₂
M_r	232.28
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	173
a, b, c (Å)	6.2885 (2), 25.4882 (9), 7.5554 (3)
β (°)	94.403 (4)
V (Å³)	1207.43 (8)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.08
Crystal size (mm)	0.22 × 0.09 × 0.02

Data collection
Diffractometer	Rigaku XtaLAB P200K
Absorption correction	Multi-scan (CrysAlis PRO; Rigaku OD, 2024 )
T_min, T_max	0.812, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	26279, 3011, 2387
R_int	0.031
(sin θ/λ)_max (Å⁻¹)	0.696

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.039, 0.097, 1.03
No. of reflections	3011
No. of parameters	163
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.21, −0.17
Computer programs: CrysAlis PRO (Rigaku OD, 2024), SHELXT2018 (Sheldrick, 2015a ), SHELXL2019 (Sheldrick, 2015b ) and OLEX2 (Dolomanov et al., 2009 ).

Supporting information

CCDC reference: 2524118

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S2056989026000460/hb8177sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989026000460/hb8177Isup2.hkl

Additional figures. DOI: https://doi.org/10.1107/S2056989026000460/hb8177sup3.pdf

Supporting information file. DOI: https://doi.org/10.1107/S2056989026000460/hb8177Isup4.cml

checkCIF report

Computing details top

2,3-Diphenylpyrazine top

Crystal data top

C₁₆H₁₂N₂	F(000) = 488
M_r = 232.28	D_x = 1.278 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 6.2885 (2) Å	Cell parameters from 7919 reflections
b = 25.4882 (9) Å	θ = 2.7–29.0°
c = 7.5554 (3) Å	µ = 0.08 mm⁻¹
β = 94.403 (4)°	T = 173 K
V = 1207.43 (8) Å³	Prism, colourless
Z = 4	0.22 × 0.09 × 0.02 mm

Data collection top

Rigaku XtaLAB P200K diffractometer	3011 independent reflections
Radiation source: Rotating Anode, Rigaku FR-X	2387 reflections with I > 2σ(I)
Rigaku Osmic Confocal Optical System monochromator	R_int = 0.031
Detector resolution: 5.8140 pixels mm^-1	θ_max = 29.6°, θ_min = 2.8°
shutterless scans	h = −8→8
Absorption correction: multi-scan (CrysAlis PRO; Rigaku OD, 2024)	k = −33→35
T_min = 0.812, T_max = 1.000	l = −7→10
26279 measured reflections

Refinement top

Refinement on F²	Primary atom site location: dual
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.039	H-atom parameters constrained
wR(F²) = 0.097	w = 1/[σ²(F_o²) + (0.0426P)² + 0.2327P] where P = (F_o² + 2F_c²)/3
S = 1.03	(Δ/σ)_max < 0.001
3011 reflections	Δρ_max = 0.21 e Å⁻³
163 parameters	Δρ_min = −0.17 e Å⁻³
0 restraints

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
N1	0.22049 (15)	0.45593 (4)	0.09624 (13)	0.0358 (2)
N4	0.56788 (15)	0.49704 (3)	0.29880 (12)	0.0332 (2)
C2	0.37217 (16)	0.42424 (4)	0.17179 (14)	0.0281 (2)
C3	0.54118 (16)	0.44465 (4)	0.28378 (13)	0.0274 (2)
C5	0.42219 (19)	0.52761 (4)	0.21441 (14)	0.0359 (3)
H5	0.441288	0.564571	0.218955	0.043*
C6	0.24486 (19)	0.50752 (4)	0.12082 (16)	0.0380 (3)
H6	0.137428	0.530775	0.072621	0.046*
C7	0.34590 (17)	0.36787 (4)	0.12216 (13)	0.0293 (2)
C8	0.50968 (18)	0.34009 (4)	0.05075 (15)	0.0360 (3)
H8	0.643471	0.356536	0.039207	0.043*
C9	0.4783 (2)	0.28844 (5)	−0.00368 (16)	0.0430 (3)
H9	0.590011	0.269856	−0.053831	0.052*
C10	0.2851 (2)	0.26396 (4)	0.01483 (16)	0.0444 (3)
H10	0.264447	0.228505	−0.021280	0.053*
C11	0.1226 (2)	0.29118 (5)	0.08586 (17)	0.0441 (3)
H11	−0.009944	0.274330	0.099417	0.053*
C12	0.15138 (18)	0.34301 (4)	0.13762 (15)	0.0359 (3)
H12	0.037361	0.361700	0.184020	0.043*
C13	0.69606 (16)	0.41323 (4)	0.39840 (13)	0.0275 (2)
C14	0.89935 (17)	0.43358 (4)	0.44188 (15)	0.0331 (2)
H14	0.940374	0.465469	0.388999	0.040*
C15	1.04192 (18)	0.40806 (5)	0.56072 (17)	0.0411 (3)
H15	1.179558	0.422512	0.589169	0.049*
C16	0.9848 (2)	0.36156 (5)	0.63825 (17)	0.0433 (3)
H16	1.082815	0.343962	0.719784	0.052*
C17	0.7840 (2)	0.34079 (4)	0.59647 (16)	0.0405 (3)
H17	0.744329	0.308866	0.649905	0.049*
C18	0.63994 (18)	0.36615 (4)	0.47724 (15)	0.0333 (2)
H18	0.502664	0.351456	0.449107	0.040*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0348 (5)	0.0320 (5)	0.0400 (5)	0.0054 (4)	−0.0009 (4)	0.0013 (4)
N4	0.0421 (5)	0.0245 (4)	0.0328 (5)	−0.0017 (4)	0.0023 (4)	0.0005 (3)
C2	0.0291 (5)	0.0261 (5)	0.0291 (5)	0.0015 (4)	0.0031 (4)	0.0009 (4)
C3	0.0309 (5)	0.0243 (5)	0.0274 (5)	−0.0001 (4)	0.0050 (4)	0.0007 (4)
C5	0.0501 (7)	0.0232 (5)	0.0347 (6)	0.0040 (4)	0.0054 (5)	0.0012 (4)
C6	0.0423 (6)	0.0312 (6)	0.0404 (6)	0.0101 (5)	0.0029 (5)	0.0037 (5)
C7	0.0332 (5)	0.0270 (5)	0.0267 (5)	0.0013 (4)	−0.0045 (4)	−0.0001 (4)
C8	0.0378 (6)	0.0324 (6)	0.0375 (6)	0.0024 (5)	0.0010 (5)	−0.0015 (5)
C9	0.0555 (7)	0.0334 (6)	0.0398 (7)	0.0110 (5)	0.0012 (6)	−0.0041 (5)
C10	0.0628 (8)	0.0265 (5)	0.0418 (7)	−0.0010 (5)	−0.0100 (6)	−0.0042 (5)
C11	0.0454 (7)	0.0368 (6)	0.0485 (7)	−0.0098 (5)	−0.0073 (6)	−0.0015 (5)
C12	0.0344 (6)	0.0340 (6)	0.0382 (6)	−0.0014 (4)	−0.0036 (5)	−0.0031 (5)
C13	0.0310 (5)	0.0251 (5)	0.0264 (5)	0.0004 (4)	0.0010 (4)	−0.0035 (4)
C14	0.0334 (5)	0.0291 (5)	0.0368 (6)	−0.0022 (4)	0.0032 (5)	−0.0039 (4)
C15	0.0328 (6)	0.0433 (7)	0.0456 (7)	0.0012 (5)	−0.0062 (5)	−0.0091 (5)
C16	0.0488 (7)	0.0408 (6)	0.0382 (6)	0.0118 (5)	−0.0108 (5)	−0.0029 (5)
C17	0.0549 (7)	0.0286 (5)	0.0370 (6)	0.0036 (5)	−0.0024 (5)	0.0035 (5)
C18	0.0374 (6)	0.0275 (5)	0.0344 (6)	−0.0028 (4)	−0.0008 (5)	0.0001 (4)

Geometric parameters (Å, º) top

N1—C2	1.3434 (13)	C10—H10	0.9500
N1—C6	1.3352 (15)	C10—C11	1.3776 (18)
N4—C3	1.3495 (13)	C11—H11	0.9500
N4—C5	1.3280 (14)	C11—C12	1.3856 (16)
C2—C3	1.4065 (14)	C12—H12	0.9500
C2—C7	1.4908 (14)	C13—C14	1.3953 (14)
C3—C13	1.4867 (14)	C13—C18	1.3970 (15)
C5—H5	0.9500	C14—H14	0.9500
C5—C6	1.3728 (17)	C14—C15	1.3819 (16)
C6—H6	0.9500	C15—H15	0.9500
C7—C8	1.3923 (15)	C15—C16	1.3817 (18)
C7—C12	1.3905 (15)	C16—H16	0.9500
C8—H8	0.9500	C16—C17	1.3832 (18)
C8—C9	1.3888 (16)	C17—H17	0.9500
C9—H9	0.9500	C17—C18	1.3873 (16)
C9—C10	1.3824 (18)	C18—H18	0.9500

C6—N1—C2	117.58 (10)	C11—C10—H10	120.1
C5—N4—C3	117.61 (9)	C10—C11—H11	119.8
N1—C2—C3	120.82 (9)	C10—C11—C12	120.35 (11)
N1—C2—C7	114.29 (9)	C12—C11—H11	119.8
C3—C2—C7	124.88 (9)	C7—C12—H12	119.8
N4—C3—C2	120.00 (9)	C11—C12—C7	120.50 (11)
N4—C3—C13	114.35 (9)	C11—C12—H12	119.8
C2—C3—C13	125.60 (9)	C14—C13—C3	118.97 (9)
N4—C5—H5	118.9	C14—C13—C18	118.41 (10)
N4—C5—C6	122.12 (10)	C18—C13—C3	122.37 (9)
C6—C5—H5	118.9	C13—C14—H14	119.5
N1—C6—C5	121.26 (10)	C15—C14—C13	120.99 (10)
N1—C6—H6	119.4	C15—C14—H14	119.5
C5—C6—H6	119.4	C14—C15—H15	119.9
C8—C7—C2	121.11 (10)	C16—C15—C14	120.16 (11)
C12—C7—C2	119.95 (9)	C16—C15—H15	119.9
C12—C7—C8	118.85 (10)	C15—C16—H16	120.2
C7—C8—H8	119.9	C15—C16—C17	119.62 (11)
C9—C8—C7	120.28 (11)	C17—C16—H16	120.2
C9—C8—H8	119.9	C16—C17—H17	119.7
C8—C9—H9	119.9	C16—C17—C18	120.59 (11)
C10—C9—C8	120.26 (11)	C18—C17—H17	119.7
C10—C9—H9	119.9	C13—C18—H18	119.9
C9—C10—H10	120.1	C17—C18—C13	120.23 (10)
C11—C10—C9	119.74 (11)	C17—C18—H18	119.9

N1—C2—C3—N4	−8.41 (15)	C5—N4—C3—C13	−173.21 (9)
N1—C2—C3—C13	168.90 (10)	C6—N1—C2—C3	4.82 (15)
N1—C2—C7—C8	125.29 (11)	C6—N1—C2—C7	−173.66 (10)
N1—C2—C7—C12	−51.08 (13)	C7—C2—C3—N4	169.91 (9)
N4—C3—C13—C14	−29.59 (13)	C7—C2—C3—C13	−12.78 (16)
N4—C3—C13—C18	144.59 (10)	C7—C8—C9—C10	−0.88 (18)
N4—C5—C6—N1	−6.40 (18)	C8—C7—C12—C11	1.19 (16)
C2—N1—C6—C5	2.32 (16)	C8—C9—C10—C11	0.69 (18)
C2—C3—C13—C14	152.97 (10)	C9—C10—C11—C12	0.44 (18)
C2—C3—C13—C18	−32.85 (16)	C10—C11—C12—C7	−1.39 (18)
C2—C7—C8—C9	−176.47 (10)	C12—C7—C8—C9	−0.06 (16)
C2—C7—C12—C11	177.64 (10)	C13—C14—C15—C16	0.21 (18)
C3—N4—C5—C6	2.75 (16)	C14—C13—C18—C17	0.35 (16)
C3—C2—C7—C8	−53.13 (15)	C14—C15—C16—C17	−0.12 (18)
C3—C2—C7—C12	130.50 (11)	C15—C16—C17—C18	0.15 (18)
C3—C13—C14—C15	174.09 (10)	C16—C17—C18—C13	−0.27 (18)
C3—C13—C18—C17	−173.86 (10)	C18—C13—C14—C15	−0.32 (16)
C5—N4—C3—C2	4.39 (15)

Hydrogen-bond geometry (Å, º) top

Cg2 and Cg3 are the centroids of the C7–C12 and C13–C18 rings, respectively.

D—H···A	D—H	H···A	D···A	D—H···A
C6—H6···N1ⁱ	0.95	2.52	3.3740 (15)	149
C12—H12···Cg3ⁱⁱ	0.95	2.97	3.7734 (12)	143
C16—H16···Cg2ⁱⁱⁱ	0.95	2.99	3.8974 (13)	159

Symmetry codes: (i) −x, −y+1, −z; (ii) x−1, y, z; (iii) x+1, y, z+1.

Comparison of the percentages for title compound I and BOHPOD, where its asymmetric unit contains two crystallographically independent molecules, A and B top

Contact	(I)	BOHPOD (A)	BOHPOD (B)
H···H	54.0	47.7	55.1
H···C/C···H	30.0	34.1	31.6
H···N/N···H	9.7	14.7	12.2
C···C	2.7	1.5	0.8
N···N	1.8	0.1	0.0
C···N/N···C	1.7	1.9	0.3

Comparison of the dihedral angles (°) between the central and pendant rings for some structures top

Compound	α	α	α	α	α	α	α	α
I	53.12 (3)	33.28 (3)	–	–	–	–	–	–
III	56.56	57.73	–	–	–	–	–	–
V	13.58	54.30	–	–	–	–	–	–
VI	24.09	22.75	–	–	–	–	–	–
VII	62.45	68.83	43.77	55.12	42.85	51.17	57.23	51.87
VIII	56.47	30.59	56.33	72.22	44.84	66.42	52.59	53.31
IX	53.25	50.38	–	–	–	–	–	–
X	66.72	65.00	61.37	54.57	57.76	46.71	52.78	64.28
XI	57.69	31.21	56.67	54.09	74.66	23.83	–	–

Acknowledgements

The authors would like to thank D. B. Cordes for fruitful discussions. TH is grateful to Hacettepe University Scientific Research Project Unit.

Funding information

Funding for this research was provided by: Hacettepe Üniversitesi (grant No. 013 D04 602 004).

References

Akita, Y. & Ohta, A. (1982). Heterocycles 19, 329–331. CAS Google Scholar
Cheeseman, G. W. H. & Werstiuk, E. S. G. (1972). Adv. Heterocycl. Chem. 14, 99–209. CrossRef CAS Google Scholar
Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339–341. Web of Science CrossRef CAS IUCr Journals Google Scholar
Eltayeb, N. E., Hökelek, T. & Lasri, J. (2025). Acta Cryst. E81, 595–599. CSD CrossRef IUCr Journals Google Scholar
Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171–179. Web of Science CrossRef IUCr Journals Google Scholar
Hrovat, S., Drev, M., Groselj, U., Perdih, F., Svete, J., Stefane, B. & Pozgan, F. (2020). Catalysts 10, 421. CrossRef Google Scholar
Kitano, Y., Ashida, T., Ohta, A., Watanabe, T. & Akita, Y. (1983). Acta Cryst. C39, 136–139. CrossRef CAS IUCr Journals Google Scholar
Luo, K.-J., Geng, H., Zhang, C.-Y., Ni, H.-L. & Li, Q. (2017). Chin. J. Inorg. Chem. 33, 405–414. CAS Google Scholar
Mason, A. T. (1887). Ber. Dtsch Chem. Ges. 20, 267–277. CrossRef Google Scholar
McKinnon, J. J., Jayatilaka, D. & Spackman, M. A. (2007). Chem. Commun. pp. 3814–3816. Web of Science CrossRef Google Scholar
Ohta, A., Masano, S., Iwakura, S., Tamura, A., Watahiki, H., Tsutsui, M., Akita, Y., Watanabe, T. & Kurihara, T. J. (1982). J. Heterocycl. Chem. 19, 465–473. CrossRef CAS Google Scholar
Rigaku OD (2024). CrysAlis PRO. Rigaku Corporation, Tokyo, Japan. Google Scholar
Sammes, P. G. (1975). Fortschr. Chem. Org. Naturst. 32, 51–118. PubMed CAS Google Scholar
Schultheiss, N., Powell, D. R. & Bosch, E. (2003). Inorg. Chem. 42, 8886–8890. CrossRef PubMed CAS Google Scholar
Sheldrick, G. M. (2015a). Acta Cryst. A71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2015b). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Shi, D., Zhang, X., Wu, S., Wei, L., Li, K. & Wong, K. M. (2025). Inorg. Chem. 64, 20229–20242. CrossRef CAS PubMed Google Scholar
Spackman, M. A., McKinnon, J. J. & Jayatilaka, D. (2008). CrystEngComm 10, 377–388. CAS Google Scholar
Spackman, P. R., Turner, M. J., McKinnon, J. J., Wolff, S. K., Grimwood, D. J., Jayatilaka, D. & Spackman, M. A. (2021). J. Appl. Cryst. 54, 1006–1011. Web of Science CrossRef CAS IUCr Journals Google Scholar
Steel, P. J. & Caygill, G. B. (1990). J. Organomet. Chem. 395, 359–373. CrossRef CAS Google Scholar
Tian, A., Liu, J., Li, T., Tian, Y., Liu, G. & Ying, J. (2018). CrystEngComm 20, 2940–2951. CrossRef CAS Google Scholar
Tian, A., Tian, Y., Ning, Y., Hou, X., Ni, H., Ji, X., Liu, G. & Ying, J. (2016). Dalton Trans. 45, 13925–13936. Web of Science CSD CrossRef CAS PubMed Google Scholar
Turner, M. J., Thomas, S. P., Shi, M. W., Jayatilaka, D. & Spackman, M. A. (2015). Chem. Commun. 51, 3735–3738. Web of Science CrossRef CAS Google Scholar
Zhu, Y., Luo, K., Li, X., Wang, H., Yang, C., Ni, H. & Li, Q. (2018). J. Lumin. 204, 296–302. CrossRef CAS Google Scholar