3,14-Diselena-4,5,12,13-tetra­aza­tri­cyclo­[9.3.0.02,6]tetra­deca-1(11),2(6),4,12-tetra­ene

Detert, H.; Schollmeyer, D.

doi:10.1107/S2414314626000635

organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 11| Part 1| January 2026| x260063

https://doi.org/10.1107/S2414314626000635

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3,14-Diselena-4,5,12,13-tetraazatricyclo[9.3.0.0^2,6]tetradeca-1(11),2(6),4,12-tetraene

Heiner Detert ^a ^* and Dieter Schollmeyer ^a

^aUniversity Mainz, Duesbergweg 10-14, 55099 Mainz, Germany
^*Correspondence e-mail: [email protected]

Edited by M. Bolte, Goethe-Universität Frankfurt, Germany (Received 20 January 2026; accepted 22 January 2026; online 27 January 2026)

The crystal structure of the third isomer of cyclooctenobis-1,2,3-selenadiazoles, C₈H₈N₄Se₂, is reported. The molecule is located on a twofold rotation axis. The eight-membered ring adopts a twist-chair conformation with planar heterocycles. C—H⋯N hydrogen bonds connect the molecules into layers parallel to (101).

Keywords: crystal structure; heterocycle; selenium; medium-sized ring.

CCDC reference: 2524974

Structure description

The title compound, C₈H₈N₄Se₂ (Fig. 1), is the third isomer in the series of cyclooctenobis-1,2,3-selenadiazoles (Detert & Schollmeyer, 2020 ; Schollmeyer & Detert, 2025 ). These were prepared as part of a project on medium-sized cycloalkynes with functional and sterically demanding groups (Bissinger et al., 1988 ; Detert et al., 1994 ; Detert & Meier, 1997 ). Bis-1,2,3-selenadiazoles are antimicrobial agents (Al-Smadi et al., 2008 ) and important sources for medium-sized cycloalkadiynes (Gleiter et al., 1988 ; Morales & Fronczek, 1994 ). The molecule is C₂-symmetric, having the eight-membered ring in a nearly twist-chair conformation with staggered C—H bonds. Both selenadiazole rings are planar within 0.02 (6) Å at atom C5 and the torsion angle between the heterocycles is 55.5 (3)°. This is significantly larger than the torsion angle [−43.5 (11)°] between the selenadiazole rings in the isomeric molecule with an inverted orientation of the annulated heterocycles (Detert & Schollmeyer, 2020), probably due to the large atomic radii of the vicinal Se atoms in the title compound. The unit cell contains four molecules connected via four hydrogen bonds [C7—H7b⋯N2ⁱ; symmetry code: (i) −x, y + $[{1\over 2}]$ , −z + $[{1\over 2}]$ ]. The hydrogen bonds (Table 1, Fig. 2) connect the molecules to form layers parallel to ( $[\overline{1}]$ 01).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C7—H7B⋯N2ⁱ	0.99	2.61	3.466 (9)	144
Symmetry code: (i) $[-x, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Figure 1
The molecular structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
Part of the packing diagram, viewed along the c-axis direction.

Synthesis and crystallization

The title compound appeared in the synthesis of its homo-conjugated isomer (Schollmeyer & Detert, 2025) from 1,4-cyclooctanedione bissemicarbazone and selenium dioxide in 1,4-dioxane in 12% yield. Recrystallization from a solution in chloroform/ligroin gave brownish crystals (m.p. 393 K). IR (KBr): 2900, 2840, 1515, 1460, 1440, 1430, 1340, 1295, 1275, 1250, 1215, 945, 880, 850 cm⁻¹. ¹H NMR (400 MHz, CDCl₃): δ 3.20 (bs, 4H), 1.90 (bs, 4H); ¹³C NMR (100 MHz, CDCl₃): δ 158.8, 144.9 (C-1,2,7,10), 27.4, 25.1 (C-6,7,8,9); ⁷⁷Se NMR (73 MHz, CDCl₃, SeO₂/D₂O as reference): δ 295.9; ¹⁵N NMR (40,5 MHz, CDCl₃, HC₃NO₂ as reference = 0): δ 93.9, 93.1; UV (EtOH, λ, logɛ): 207 (3.85), 220 (3.86), 261 (3.57), 302 (sh, 3.33), 339 nm (sh, 3.12); MS (FD): 290 (M – N₂^+.).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms were placed at calculated positions and refined in the riding-model approximation, with C—H = 0.99 Å and U_iso(H) = 1.2U_eq(C).

Table 2
Experimental details

Crystal data
Chemical formula	C₈H₈N₄Se₂
M_r	318.10
Crystal system, space group	Monoclinic, I2/a
Temperature (K)	120
a, b, c (Å)	11.746 (2), 8.1617 (10), 10.0922 (15)
β (°)	97.121 (14)
V (Å³)	960.1 (3)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	7.66
Crystal size (mm)	0.48 × 0.09 × 0.04

Data collection
Diffractometer	STOE IPDS 2T
Absorption correction	Integration
T_min, T_max	0.468, 0.893
No. of measured, independent and observed [I > 2σ(I)] reflections	2481, 1144, 930
R_int	0.037
(sin θ/λ)_max (Å⁻¹)	0.663

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.056, 0.148, 1.10
No. of reflections	1144
No. of parameters	64
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	1.04, −1.75
Computer programs: X-AREA WinXpose (Stoe & Cie, 2020 ), X-AREA Recipe (Stoe & Cie, 2020), X-AREA Integrate (Stoe & Cie, 2020), SHELXT2014 (Sheldrick, 2015a ), SHELXL2019 (Sheldrick, 2015b ) and PLATON (Spek, 2020 ).

Structural data

CCDC reference: 2524974

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S2414314626000635/bt4196sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314626000635/bt4196Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314626000635/bt4196Isup3.cml

checkCIF report

Computing details top

3,14-Diselena-4,5,12,13-tetraazatricyclo[9.3.0.0^2,6]tetradeca-1(11),2(6),4,12-tetraene top

Crystal data top

C₈H₈N₄Se₂	F(000) = 608
M_r = 318.10	D_x = 2.201 Mg m⁻³
Monoclinic, I2/a	Mo Kα radiation, λ = 0.71073 Å
a = 11.746 (2) Å	Cell parameters from 5444 reflections
b = 8.1617 (10) Å	θ = 3.1–28.2°
c = 10.0922 (15) Å	µ = 7.66 mm⁻¹
β = 97.121 (14)°	T = 120 K
V = 960.1 (3) Å³	Plate, colorless
Z = 4	0.48 × 0.09 × 0.04 mm

Data collection top

STOE IPDS 2T diffractometer	930 reflections with I > 2σ(I)
Detector resolution: 6.67 pixels mm^-1	R_int = 0.037
rotation method, ω scans	θ_max = 28.1°, θ_min = 3.1°
Absorption correction: integration	h = −15→13
T_min = 0.468, T_max = 0.893	k = −10→10
2481 measured reflections	l = −13→13
1144 independent 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)] = 0.056	H-atom parameters constrained
wR(F²) = 0.148	w = 1/[σ²(F_o²) + (0.0748P)² + 11.7676P] where P = (F_o² + 2F_c²)/3
S = 1.10	(Δ/σ)_max < 0.001
1144 reflections	Δρ_max = 1.04 e Å⁻³
64 parameters	Δρ_min = −1.75 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
Se1	0.14172 (6)	0.61729 (7)	0.33965 (6)	0.0274 (3)
N2	0.0080 (5)	0.4890 (7)	0.3007 (5)	0.0291 (12)
N3	0.0157 (5)	0.3578 (7)	0.3698 (5)	0.0289 (12)
C4	0.1149 (6)	0.3307 (8)	0.4573 (6)	0.0259 (13)
C5	0.1943 (5)	0.4546 (8)	0.4581 (6)	0.0269 (13)
C6	0.1228 (6)	0.1830 (8)	0.5420 (6)	0.0254 (12)
H6A	0.044169	0.148577	0.555241	0.031*
H6B	0.163678	0.211823	0.630606	0.031*
C7	0.1843 (6)	0.0368 (8)	0.4861 (6)	0.0284 (13)
H7A	0.155565	−0.065021	0.523630	0.034*
H7B	0.162450	0.033262	0.388198	0.034*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Se1	0.0327 (4)	0.0269 (4)	0.0241 (4)	0.0027 (3)	0.0096 (3)	0.0013 (2)
N2	0.031 (3)	0.033 (3)	0.024 (2)	0.001 (2)	0.007 (2)	−0.001 (2)
N3	0.030 (3)	0.031 (3)	0.028 (3)	0.003 (2)	0.011 (2)	0.000 (2)
C4	0.027 (3)	0.027 (3)	0.026 (3)	−0.003 (3)	0.012 (2)	−0.003 (2)
C5	0.027 (3)	0.029 (3)	0.027 (3)	−0.001 (3)	0.011 (2)	−0.006 (2)
C6	0.029 (3)	0.024 (3)	0.025 (3)	−0.006 (3)	0.010 (2)	−0.002 (2)
C7	0.034 (3)	0.027 (3)	0.026 (3)	0.001 (3)	0.008 (3)	0.002 (3)

Geometric parameters (Å, º) top

Se1—C5	1.841 (7)	C6—C7	1.538 (9)
Se1—N2	1.888 (6)	C6—H6A	0.9900
N2—N3	1.275 (8)	C6—H6B	0.9900
N3—C4	1.390 (9)	C7—C7ⁱ	1.534 (13)
C4—C5	1.375 (9)	C7—H7A	0.9900
C4—C6	1.474 (9)	C7—H7B	0.9900
C5—C5ⁱ	1.467 (13)

C5—Se1—N2	86.5 (3)	C7—C6—H6A	108.5
N3—N2—Se1	110.6 (5)	C4—C6—H6B	108.5
N2—N3—C4	118.6 (6)	C7—C6—H6B	108.5
C5—C4—N3	113.7 (6)	H6A—C6—H6B	107.5
C5—C4—C6	127.2 (6)	C7ⁱ—C7—C6	116.2 (5)
N3—C4—C6	119.1 (6)	C7ⁱ—C7—H7A	108.2
C4—C5—C5ⁱ	124.0 (5)	C6—C7—H7A	108.2
C4—C5—Se1	110.7 (5)	C7ⁱ—C7—H7B	108.2
C5ⁱ—C5—Se1	125.3 (3)	C6—C7—H7B	108.2
C4—C6—C7	114.9 (5)	H7A—C7—H7B	107.4
C4—C6—H6A	108.5

C5—Se1—N2—N3	−0.1 (4)	C6—C4—C5—Se1	−177.1 (5)
Se1—N2—N3—C4	−0.1 (7)	N2—Se1—C5—C4	0.2 (4)
N2—N3—C4—C5	0.3 (8)	N2—Se1—C5—C5ⁱ	179.9 (6)
N2—N3—C4—C6	177.4 (5)	C5—C4—C6—C7	−87.5 (8)
N3—C4—C5—C5ⁱ	180.0 (6)	N3—C4—C6—C7	95.9 (7)
C6—C4—C5—C5ⁱ	3.2 (11)	C4—C6—C7—C7ⁱ	83.7 (8)
N3—C4—C5—Se1	−0.4 (7)

Symmetry code: (i) −x+1/2, y, −z+1.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C7—H7B···N2ⁱⁱ	0.99	2.61	3.466 (9)	144

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

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