Synthesis and structure of 5,5′-(tris­ulfane-1,3-di­yl)bis­(1,3,4-thia­diazol-2-amine)

Atashov, A.; Torambetov, B.; Ashurov, J.; Hökelek, T.; Belay, A.N.; Azizova, A.N.

doi:10.1107/S2056989026005517

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Volume 82| Part 7| July 2026|

https://doi.org/10.1107/S2056989026005517

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Synthesis and structure of 5,5′-(trisulfane-1,3-diyl)bis(1,3,4-thiadiazol-2-amine)

Aziz Atashov,^a Batirbay Torambetov,^b Jamshid Ashurov,^c Tuncer Hökelek,^d Alebel N. Belay ^e ^* and Asmet N. Azizova ^f,^g

^aKarakalpak State University, 1 Ch. Abdirov St., Nukus 230112, Uzbekistan, ^bNational University of Uzbekistan named after Mirzo Ulugbek, 4 University St., Tashkent 100174, Uzbekistan, ^cInstitute of Bioorganic Chemistry, Academy of Sciences of Uzbekistan, M. Ulugbek St. 83, Tashkent 100125, Uzbekistan, ^dHacettepe University, Department of Physics, 06800 Beytepe-Ankara, Türkiye, ^eDepartment of Chemistry, Bahir Dar University, PO Box 79, Bahir Dar, Ethiopia, ^fAzerbaijan Medical University, Scientific Research Centre (SRC), A. Kasumzade Str. 14, AZ 1022, Baku, Azerbaijan, and ^gScientific Research Center, Baku Engineering University, Hasan Aliyev Str. 120, AZ 0101, Khirdalan, Absheron, Azerbaijan
^*Correspondence e-mail: [email protected]

Edited by W. T. A. Harrison, University of Aberdeen, United Kingdom (Received 16 April 2026; accepted 25 May 2026; online 5 June 2026)

The title compound, C₄H₄N₆S₅, consists of two 1,3,4-thiadiazol-2-amine moieties bridged by a trisulfanediyl group [S—S—S = 107.98 (6)°]. The conformation is supported by an intramolecular π–π stacking interaction. In the crystal, N—H⋯N hydrogen bonds link the molecules, enclosing R²₂(8) and R⁵₅(31) ring motifs, into infinite channels/tubes propagating along the b-axis direction. Hirshfeld surface analysis revealed that the most important contributions for the crystal packing are from S⋯S (33.6%) and H⋯N/N⋯H (32.8%) interactions.

Keywords: 1,3,4-thiadiazole; crystal structure; noncovalent interactions.

CCDC reference: 2556705

1. Chemical context

1,3,4-Thiadiazole (C₂H₂N₂S) is a five-membered heterocyclic aromatic compound containing two nitrogen atoms and one sulfur atom. In order to improve the functional properties of 1,3,4- thiadiazoles, substituents can be attached at the 2- and 5-positions, enabling the creation of diverse bioactive compounds (e.g., antibacterial, anticancer) from a stable, electron-deficient, five-membered heterocyclic ring (Hu et al., 2014 ). Common synthesis methods include the cyclization of thiosemicarbazides or diacylhydrazines, as well as nucleophilic substitution and C—H activation to introduce various substituents (Hu et al., 2014; Kumar et al., 2024 ). In this work, we describe the synthesis and structure of the title compound, C₄H₄N₆S₅ (I), prepared by the oxidation of 5-amino-1,3,4-thiadiazole-2-thiol with 30% H₂O₂.

2. Structural commentary

Compound (I) consists of two 1,3,4-thiadiazol-2-amine moieties bridged by the trisulfanediyl group (Fig. 1) with the S2—S3—S4 bridging angle of 107.98 (6)°. The S2—S3 [2.0478 (16) Å] and S3—S4 [2.0705 (16) Å] and S2—C2 [1.766 (5) Å] and S4—C3 [1.755 (16) Å] bond lengths are slightly different, while the C2—S2—S3 [101.91 (15)°] and C3—S4—S3 [100.29 (15)°] bond angles are significantly different. The A (N1/N2/S1/C1/C2) and B (N4/N5/S5/C3/C4) rings are oriented at a dihedral angle of 5.15 (13)°, with a centroid–centroid separation of 3.621 (2) Å (slippage 1.336 Å), indicative of an intramolecular π–π stacking interaction. The key torsion angles associated with the trisulfide bridge are C2—S2—S3—S4 = 81.8 (3) and S2—S3—S4—C3 = −79.3 (3)°.

Figure 1
The molecular structure of (I) showing 50% probability ellipsoids.

Atoms N3, N6, S2 and S4 are displaced by 0.076 (4), −0.062 (4), 0.0182 (11) and −0.1483 (12) Å, respectively, from their corresponding ring planes. The C1—N3 [1.338 (6) Å] and C4—N6 [1.320 (6) Å] bond lengths are a little longer than a typical C=N double bond (e.g. 1.27–1.30 Å) in imines and oximes with more orbital overlap indicating partial double bond (e.g., 1.35–1.38 Å for pyridine and amides) character due to resonance delocalization. On the other hand, the S1—C1—N3 [120.6 (3)°] and S5—C4—N6 [123.5 (3)°], N1—C1—N3 [125.2 (4)°] and N4—C4—N6 [123.7 (4)°], S1—C1—N1 [114.2 (4)°] and S5—C4—N4 [112.8 (3)°], C1—N1—N2 [111.4 (4)°] and C4—N4—N5 [112.6 (3)°] bond angles are significantly different.

3. Supramolecular features

In the crystal, N—H⋯N hydrogen bonds (Table 1) link the molecules, enclosing R₂²(8) and R₅⁵(31) ring motifs (Fig. 2a), into infinite channels/tubes propagating along the b-axis direction (Fig. 2b). No intermolecular π–π stacking or C—H⋯π interactions are observed.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N3—H3A⋯N4ⁱ	0.86	2.12	2.969 (6)	171
N3—H3B⋯N2ⁱⁱ	0.86	2.25	3.099 (6)	170
N6—H6A⋯N5ⁱⁱ	0.86	2.16	3.021 (5)	174
N6—H6B⋯N1ⁱ	0.86	2.16	3.015 (6)	171
Symmetry codes: (i) ; (ii) .

Figure 2
Partial packing diagrams for (I) showing N—H⋯N hydrogen bonds as dashed lines with (a) the R₂²(8) and R₅⁵(31) ring motifs and (b) the infinite channels/tubes viewed along the b-axis direction.

4. Hirshfeld surface analysis

The intermolecular interactions in the crystal were further visualized by carrying out a Hirshfeld surface (HS) analysis using CrystalExplorer 17.5 (Spackman et al., 2021 ). Fig. 3 shows the Hirshfeld surface with several neighboring molecules in the crystal. 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 (in close contact) or longer (distinct contacts) than the van der Waals radii, respectively. The red spots indicate their roles as the respective donors and/or acceptor atoms in hydrogen bonding, as discussed above; they also appear as the blue and red regions corresponding to positive and negative potentials on the HS mapped over electrostatic potential as shown in Fig. S1. The blue and red regions indicate positive (hydrogen-bond donors) and negative (hydrogen-bond acceptors) electrostatic potentials. The overall two-dimensional fingerprint plots are shown in Fig. 4a and those delineated into different contact types are illustrated in Fig. 4b–i. According to the two-dimensional fingerprint plots, S⋯S and H⋯N/N⋯H contacts make the most significant contributions to the HS, at 33.6% and 32.8%, respectively.

Figure 3
View of the three-dimensional Hirshfeld surface for (I) plotted over d_norm in the range −0.51 to 1.25 a.u.

Figure 4
The two-dimensional fingerprint plots for (I), showing (a) all interactions, and delineated into different contact types (b)–(i). The d_i and d_e values are the closest internal and external distances (in Å) from given points on the Hirshfeld surface.

5. Synthesis and crystallization

Hydrogen peroxide (30%, 10.4 ml) was added dropwise to a solution of 2-amino-5-mercapto-1,3,4-thiadiazole (0.20 mol) in the mixed solvents of ethanol (40 ml) and water (20 ml) at room temperature (Fig. 5). The mixture was stirred for 3 h, giving a precipitate. The precipitate was filtered off, dried and recrystallized from a N,N-dimethylformamide (DMF) solution to yield the title compound as a yellow solid. Yellow block-like single crystals of (I) suitable for single-crystal X-ray diffraction were grown by slow evaporation from DMF at room temperature. Yield: 58% (based on 2-amino-5-mercapto-1,3,4-thiadiazole). Analysis (%) calculated for C₄H₄N₆S₅, calculated (observed): C 16.21 (16.18), H 1.36 (1.34), N 28.35 (28.33). IR (ATR, 298 K, cm⁻¹): 3123, 3260 and 3402 ν(N—H), 1595 and 1614 ν(C=N). ¹H NMR (400 MHz, DMSO-d₆, ppm): δ 7.66 and 7.83 (4H, 2 NH₂). ¹³C{¹H} NMR (100 MHz, DMSO-d₆, ppm): δ 157.2 and 148.6.

Figure 5
Synthesis scheme for (I).

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. The hydrogen-atom positions were calculated geometrically at distances of N—H = 0.86 Å and refined using a riding model. The constraint U_iso(H) = 1.2U_eq(N) was applied in all cases.

Table 2
Experimental details

Crystal data
Chemical formula	C₄H₄N₆S₅
M_r	296.43
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	293
a, b, c (Å)	11.0300 (4), 5.9139 (2), 16.2881 (7)
β (°)	92.406 (4)
V (Å³)	1061.54 (7)
Z	4
Radiation type	Cu Kα
μ (mm⁻¹)	9.89
Crystal size (mm)	0.16 × 0.12 × 0.08

Data collection
Diffractometer	XtaLAB Synergy, Single source at home/near, HyPix3000
Absorption correction	Multi-scan (CrysAlis PRO; Rigaku OD, 2020 )
T_min, T_max	0.380, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	8905, 2054, 1675
R_int	0.078
(sin θ/λ)_max (Å⁻¹)	0.615

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.069, 0.202, 1.00
No. of reflections	2054
No. of parameters	136
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.77, −0.66
Computer programs: CrysAlis PRO (Rigaku OD, 2020), SHELXT (Sheldrick, 2015a ), SHELXL2016/6 (Sheldrick, 2015b ) and OLEX2 (Dolomanov et al., 2009 ).

Supporting information

CCDC reference: 2556705

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S2056989026005517/hb8214sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989026005517/hb8214Isup2.hkl

Figure S1.3D Hirshfeld surface of the title compound. DOI: https://doi.org/10.1107/S2056989026005517/hb8214sup3.pdf

Supporting information file. DOI: https://doi.org/10.1107/S2056989026005517/hb8214Isup4.cml

checkCIF report

Computing details top

5,5'-(Trisulfane-1,3-diyl)bis(1,3,4-thiadiazol-2-amine) top

Crystal data top

C₄H₄N₆S₅	F(000) = 600
M_r = 296.43	D_x = 1.855 Mg m⁻³
Monoclinic, P2₁/c	Cu Kα radiation, λ = 1.54184 Å
a = 11.0300 (4) Å	Cell parameters from 3057 reflections
b = 5.9139 (2) Å	θ = 4.0–71.0°
c = 16.2881 (7) Å	µ = 9.89 mm⁻¹
β = 92.406 (4)°	T = 293 K
V = 1061.54 (7) Å³	Block, colourless
Z = 4	0.16 × 0.12 × 0.08 mm

Data collection top

XtaLAB Synergy, Single source at home/near, HyPix3000 diffractometer	2054 independent reflections
Radiation source: micro-focus sealed X-ray tube, PhotonJet (Cu) X-ray Source	1675 reflections with I > 2σ(I)
Mirror monochromator	R_int = 0.078
Detector resolution: 10.0000 pixels mm^-1	θ_max = 71.5°, θ_min = 4.0°
ω scans	h = −13→13
Absorption correction: multi-scan (CrysAlisPro; Rigaku OD, 2020)	k = −7→7
T_min = 0.380, T_max = 1.000	l = −19→19
8905 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)] = 0.069	H-atom parameters constrained
wR(F²) = 0.202	w = 1/[σ²(F_o²) + (0.1567P)²] where P = (F_o² + 2F_c²)/3
S = 1.00	(Δ/σ)_max < 0.001
2054 reflections	Δρ_max = 0.77 e Å⁻³
136 parameters	Δρ_min = −0.66 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
S3	0.47315 (9)	0.7178 (2)	0.31102 (7)	0.0452 (4)
S5	0.21531 (10)	0.30438 (19)	0.26530 (7)	0.0457 (4)
S1	0.33652 (10)	0.49558 (19)	0.47085 (7)	0.0451 (4)
S4	0.33425 (11)	0.75476 (18)	0.22253 (7)	0.0464 (4)
S2	0.44180 (10)	0.93820 (19)	0.40475 (7)	0.0488 (4)
N2	0.2520 (3)	0.8882 (7)	0.5007 (2)	0.0466 (9)
N4	0.0612 (3)	0.5350 (6)	0.3441 (2)	0.0438 (8)
N5	0.1361 (3)	0.6891 (6)	0.3097 (2)	0.0444 (8)
N1	0.1785 (4)	0.7401 (7)	0.5423 (3)	0.0473 (9)
N6	0.0369 (4)	0.1443 (6)	0.3578 (3)	0.0489 (9)
H6B	−0.023827	0.161979	0.388611	0.059*
H6A	0.061155	0.010410	0.345985	0.059*
N3	0.1525 (4)	0.3479 (7)	0.5594 (3)	0.0549 (11)
H3A	0.090114	0.365799	0.588721	0.066*
H3B	0.178061	0.214081	0.548935	0.066*
C4	0.0930 (4)	0.3226 (7)	0.3287 (3)	0.0409 (9)
C1	0.2097 (4)	0.5284 (8)	0.5301 (3)	0.0431 (10)
C2	0.3355 (4)	0.7875 (8)	0.4616 (3)	0.0417 (9)
C3	0.2197 (4)	0.5970 (8)	0.2674 (3)	0.0417 (9)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
S3	0.0374 (6)	0.0526 (7)	0.0465 (7)	0.0010 (4)	0.0108 (5)	−0.0029 (5)
S5	0.0428 (6)	0.0443 (6)	0.0507 (7)	0.0035 (4)	0.0097 (5)	−0.0090 (5)
S1	0.0425 (6)	0.0455 (6)	0.0481 (7)	0.0052 (4)	0.0121 (5)	−0.0021 (4)
S4	0.0486 (7)	0.0500 (7)	0.0408 (7)	−0.0005 (4)	0.0061 (5)	0.0013 (5)
S2	0.0502 (7)	0.0490 (7)	0.0479 (7)	−0.0088 (5)	0.0100 (5)	−0.0070 (5)
N2	0.0414 (19)	0.051 (2)	0.048 (2)	0.0010 (16)	0.0068 (16)	−0.0047 (18)
N4	0.0376 (17)	0.0445 (19)	0.050 (2)	0.0026 (15)	0.0063 (15)	−0.0057 (16)
N5	0.0423 (18)	0.049 (2)	0.042 (2)	0.0024 (16)	0.0005 (15)	−0.0024 (16)
N1	0.047 (2)	0.049 (2)	0.047 (2)	−0.0013 (16)	0.0141 (17)	−0.0069 (16)
N6	0.0481 (19)	0.042 (2)	0.057 (2)	0.0034 (16)	0.0115 (17)	−0.0026 (17)
N3	0.062 (2)	0.047 (2)	0.058 (3)	0.0075 (19)	0.023 (2)	−0.0003 (18)
C4	0.0351 (19)	0.047 (2)	0.041 (2)	0.0045 (16)	−0.0028 (17)	−0.0067 (18)
C1	0.043 (2)	0.050 (2)	0.037 (2)	0.0039 (18)	0.0058 (17)	−0.0066 (18)
C2	0.040 (2)	0.046 (2)	0.039 (2)	0.0009 (17)	0.0032 (17)	−0.0053 (18)
C3	0.039 (2)	0.044 (2)	0.043 (2)	0.0025 (17)	0.0041 (17)	−0.0028 (18)

Geometric parameters (Å, º) top

S3—S4	2.0705 (16)	N4—N5	1.366 (5)
S3—S2	2.0478 (16)	N4—C4	1.331 (5)
S5—C4	1.737 (4)	N5—C3	1.294 (6)
S5—C3	1.732 (5)	N1—C1	1.315 (6)
S1—C1	1.744 (4)	N6—H6B	0.8600
S1—C2	1.733 (5)	N6—H6A	0.8600
S4—C3	1.755 (4)	N6—C4	1.320 (6)
S2—C2	1.766 (5)	N3—H3A	0.8600
N2—N1	1.389 (5)	N3—H3B	0.8600
N2—C2	1.287 (6)	N3—C1	1.338 (6)

S2—S3—S4	107.98 (6)	C1—N3—H3B	120.0
C3—S5—C4	87.0 (2)	N4—C4—S5	112.8 (3)
C2—S1—C1	86.2 (2)	N6—C4—S5	123.5 (3)
C3—S4—S3	100.29 (15)	N6—C4—N4	123.7 (4)
C2—S2—S3	101.91 (15)	N1—C1—S1	114.2 (4)
C2—N2—N1	113.2 (4)	N1—C1—N3	125.2 (4)
C4—N4—N5	112.6 (3)	N3—C1—S1	120.6 (3)
C3—N5—N4	113.2 (4)	S1—C2—S2	123.1 (3)
C1—N1—N2	111.4 (4)	N2—C2—S1	114.8 (4)
H6B—N6—H6A	120.0	N2—C2—S2	122.0 (4)
C4—N6—H6B	120.0	S5—C3—S4	122.9 (2)
C4—N6—H6A	120.0	N5—C3—S5	114.3 (3)
H3A—N3—H3B	120.0	N5—C3—S4	122.7 (4)
C1—N3—H3A	120.0

S3—S4—C3—S5	−78.2 (3)	N1—N2—C2—S2	−179.3 (3)
S3—S4—C3—N5	97.0 (4)	C4—S5—C3—S4	174.1 (3)
S3—S2—C2—S1	33.6 (3)	C4—S5—C3—N5	−1.4 (3)
S3—S2—C2—N2	−147.6 (4)	C4—N4—N5—C3	1.9 (6)
N2—N1—C1—S1	3.1 (5)	C1—S1—C2—S2	−179.4 (3)
N2—N1—C1—N3	−177.1 (4)	C1—S1—C2—N2	1.8 (4)
N4—N5—C3—S5	0.0 (5)	C2—S1—C1—N1	−2.7 (4)
N4—N5—C3—S4	−175.5 (3)	C2—S1—C1—N3	177.4 (4)
N5—N4—C4—S5	−3.0 (5)	C2—N2—N1—C1	−1.7 (6)
N5—N4—C4—N6	177.6 (4)	C3—S5—C4—N4	2.5 (3)
N1—N2—C2—S1	−0.4 (5)	C3—S5—C4—N6	−178.1 (4)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N3—H3A···N4ⁱ	0.86	2.12	2.969 (6)	171
N3—H3B···N2ⁱⁱ	0.86	2.25	3.099 (6)	170
N6—H6A···N5ⁱⁱ	0.86	2.16	3.021 (5)	174
N6—H6B···N1ⁱ	0.86	2.16	3.015 (6)	171

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

Acknowledgements

The author's contributions are as follows. Conceptualization, ANB and TH; synthesis, AA and BT; X-ray analysis, BT, JA and TH; Hirshfeld surface analysis, TH; writing (review and editing of the manuscript) ANA, ANB and TH; supervision, TH and ANB.

Funding information

This work has been supported by the Azerbaijan Medical University and Baku Engineering University. TH is also grateful to Hacettepe University Scientific Research Project Unit (grant No. 013 D04 602 004).

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