Literature DB >> 28932482

Crystal structure of 4-amino-3-(thio-phen-3-ylmeth-yl)-1H-1,2,4-triazole-5(4H)-thione.

Trung Vu Quoc1, Linh Nguyen Ngoc1, Vy Do Truc1, Linh Duong Khanh1, Hung Ha Manh2, Chien Thang Pham3, Luc Van Meervelt4.   

Abstract

In the title compound, C7H8N4S2, the thio-phene ring shows rotational disorder over two orientations in a 0.6957 (15):0.3043 (15) ratio. The plane of the 1,2,4-triazole ring makes a dihedral angle of 75.02 (17)° with the major-disorder component of the thiophene ring. In the crystal, two types of inversion dimers, described by the graph-set motifs R22(8) and R22(10), are formed by N-H⋯S inter-actions. Chains of mol-ecules running in the [101] direction are linked by weaker N-H⋯N inter-actions. The thio-phene ring is involved in π-π and C-H⋯π inter-actions.

Entities:  

Keywords:  1,2,4-triazole-3-thione; crystal structure; disorder; polythio­phene; thio­phene

Year:  2017        PMID: 28932482      PMCID: PMC5588588          DOI: 10.1107/S2056989017012191

Source DB:  PubMed          Journal:  Acta Crystallogr E Crystallogr Commun


Chemical context

Recently, the synthesis, characterization and anti­fungal activities, together with crystal structure determinations, of thio­phene-based heterocyclic chalcones have been investigated (Ming et al., 2017 ▸). Thio­phene-containing β-diketonate complexes of copper(II) have been studied and their deposits obtained by electropolymerization have been characterized (Oyarce et al., 2017 ▸). Combinations of the thio­phene ring with other heterocyclic rings have also been investigated, such as a β-keto–enol group embedded with thio­phene and pyridine moieties giving inter­esting applications in the field of solid-phase extraction (Radi et al., 2016 ▸). As part of our ongoing studies of new polythio­phenes and their properties (Nguyen et al., 2016 ▸; Vu et al., 2016 ▸; Vu Quoc et al., 2017 ▸), we have synthesized a new thio­phene monomer containing an additional 1,2,4-triazole ring. The polymer obtained from 4-amino-3-(thio­phen-3-ylmeth­yl)-1H-1,2,4-triazole-5(4H)-thione using FeCl3 as oxidant was further characterized by IR and NMR spectroscopy, and TGA and is soluble in most common organic solvents, such as DMF and DMSO. We present here the synthesis and crystal structure of the title compound, 3.

Structural commentary

The title compound (Fig. 1 ▸) crystallizes in the monoclinic space group P21/n with one mol­ecule in the asymmetric unit. The thio­phene ring is disordered over two orientations in a rotation of approximately 180° around the C5—C3 bond [occupancy factors = 0.6957 (15) for ring A or S1A/C1A/C2A/C3/C4A and 0.3043 (15) for ring B or S1B/C1B/C2B/C3/C4B]. The 1,2,4-triazole ring is almost planar (r.m.s. deviation = 0.001 Å for ring N2/N3/N4/C6/C7), with the substituents N1, S2 and C5 deviating by −0.034 (1), 0.008 (1) and 0.093 (1) Å, respectively. Due to the sp 3 character of the linking atom C5, the planes of the five-membered rings make dihedral angles of 75.02 (17) (ring A) and 76.4 (4)° (ring B), which results in a V-shaped conformation. Atom N1 clearly has an sp 3 hybridization as shown by the bond angles.
Figure 1

A view of the asymmetric unit of the title compound, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are shown as small circles of arbitrary radii. The minor component of the disordered thio­phene rings is shown in pale yellow.

Supra­molecular features

The crystal packing of the title compound is shown in Fig. 2 ▸. The 1H-1,2,4-triazole-5(4H)-thione ring possesses an NH2 group, which, in principle, can act as a donor or acceptor for hydrogen bonding, an NH group, which can act as a donor, and an N atom and C=S group, which can only act as acceptors. Two types of inversion dimers are formed (Fig. 3 ▸ and Table 1 ▸). The first one, described as graph-set motif (8), involves hydrogen bonds between the NH and C=S groups, whereas in the second one, the NH2 group interacts with the C=S grouping, resulting in a ring structure of graph-set (10). The second H atom of the NH2 group inter­acts with the N atom of a neighbouring 1H-1,2,4-triazole-5(4H)-thione ring, resulting in chains of graph-set C(5) in the [101] direction (Fig. 3 ▸ and Table 1 ▸).
Figure 2

Crystal packing of the title compound shown in projection down the a axis.

Figure 3

Part of the crystal packing of the title compound, showing the rings of graph-set motif (8) and (10) formed by N—H⋯S hydrogen-bond inter­actions [see Table 1 ▸; symmetry codes: (i) −x, −y + 2, −z + 1; (ii) −x + 1, −y + 2, −z + 1; (iii) x + , −y + , z + ] and a chain of graph-set motif C(5).

Table 1

Hydrogen-bond geometry (Å, °)

Cg3 is the centroid of the N2/N3/N4/C6/C7 ring.

D—H⋯A D—HH⋯A DA D—H⋯A
N1—H1C⋯N3i 0.909 (15)2.622 (15)3.3847 (13)142.0 (12)
N1—H1D⋯S2ii 0.849 (17)2.628 (16)3.4163 (9)154.9 (13)
N4—H4⋯S2iii 0.890 (16)2.395 (15)3.2847 (9)178.2 (12)
C1B—H1BCg3iv 0.952.783.503 (11)134

Symmetry codes: (i) ; (ii) ; (iii) , ; (iv) .

The disordered thio­phene ring is only involved in a π–π stacking inter­action with the 1,2,4-triazole ring [Cg1⋯Cg3i = 3.415 (2) Å and Cg2⋯Cg3i = 3.440 (5) Å; Cg1, Cg2 and Cg3 are the centroids of ring A, ring B and the 1,2,4-triazole ring, respectively; symmetry code: (i) x + , −y + , z − ; Fig. 4 ▸]. The crystal packing shows a weak C—H⋯π inter­action (Table 1 ▸) and contains no voids.
Figure 4

Part of the crystal packing of the title compound, showing the π–π stacking inter­actions between the thio­phene (yellow) and 1,2,4-triazole (blue) rings (only the major component of the disordered thio­phene ring is shown).

The packing was further investigated by an analysis of the Hirshfeld surface and two-dimensional fingerprint plots using CrystalExplorer (McKinnon et al., 2007 ▸; Spackman & Jayatilaka, 2009 ▸). The donors and acceptors corresponding to the N—H⋯S inter­actions are visible as bright-red spots in Fig. 5 ▸(a). The pale-red spots in Fig. 5 ▸(b) are the weaker N—H⋯N and C—H⋯N inter­actions. The relative contributions of the different inter­molecular inter­actions to the Hirshfeld surface area in descending order are: H⋯H (40.4%), S⋯H (26.7%), N⋯H (13.3%), C⋯H (8.2%), CC (4.1%), C⋯N (3.7%), S⋯C (2.3%) and S⋯N (1.2%). This illustrates that the weak N—H⋯N and C—H⋯N inter­actions contribute significantly to the packing of the title compound.
Figure 5

Hirshfeld surface for title compound mapped over d norm over the range −0.436 to 1.179 a.u., highlighting (a) the N—H⋯S hydrogen bonding and (b) the N—H⋯N and C—H⋯N inter­actions.

Database survey

A search of the Cambridge Structural Database (CSD, Version 5.38, last update May 2017; Groom et al., 2016 ▸) for structures containing an 4-amino-3-methyl-1H-1,2,4-triazole-5(4H)-thione moiety gave 69 hits; in 41 of these structures, the C=S and/or NH2 groups are complexed with a metal ion. The 1,2,4-triazole ring is almost planar, with the largest deviation from the best plane through the ring atoms being 0.034 Å [for the complex mer-tri­chlorido­(dimethyl sulfoxide-κS)(4-amino-3-ethyl-1,2,4-Δ2-triazoline-5-thione-κ2 N,S)ruthenium(III) hemi­hydrate; CSD refcode KESQOO; Cingi et al., 2000 ▸].

Synthesis and crystallization

The reaction scheme used to synthesize the title compound, 3, is given in Fig. 6 ▸. Methyl 2-(thio­phen-3-yl)acetate, 1, and 2-(thio­phen-3-yl)acetohydrazide, 2, were synthesized as described in a previous study (Vu Quoc et al., 2017 ▸).
Figure 6

Reaction scheme for the title compound.

For the synthesis of 4-amino-3-(thio­phen-3-ylmeth­yl)-1H-1,2,4-triazole-5(4H)-thione, 3, a mixture of hydrazide 2 (5 mmol), KOH (0.01 mol), ethanol (10 ml) and carbon di­sulfide (10 mmol) was stirred at room temperature until the formation of hydrogen sulfide stopped. An excess of alcohol was removed by distillation and the solid was washed with diethyl ether. A mixture of the resulting solid in water (10 ml) and hydrazine hydrate (15 ml) was then refluxed for 8 h at 353 K. The reaction mixture was cooled and neutralized with dilute hydro­chloric acid. The solid which precipitated was filtered off, washed thoroughly with water, dried and recrystallized from an ethanolwater solvent mixture (4:1 v/v) to give 0.63 g (yield 60.0%) of 3 in the form of colourless crystals (m.p. 378 K). IR (Nicolet Impact 410 FT–IR, KBr, cm−1): 3452 (νNH), 3088, 2911 (νCH), 1576 (νC=C thio­phene), 1278, 1207 (νC=S). 1H NMR [Bruker XL-500, 500 MHz, d 6-DMSO, δ (ppm), J (Hz)]: 7.33 (m, 1H, 4 J = 1.0, H2), 7.06 (m, 1H, 2 J = 1.0, 5 J = 5.0, H4), 7.49 (dd, 1H, 2 J = 3.0, 4 J = 5.0, H5), 4.04 (s, 2H, H6), 13.54 (s, 1H, H8), 5.58 (s, 2H, H10). 13C NMR [Bruker XL-500, 125 MHz, d 6-DMSO, δ (ppm)]: 123.03 (C2), 135.61 (C3), 128.98 (C4), 126.67 (C5), 25.60 (C6), 151.55 (C7), 166.47 (C9). Calculation for C7H8N4S2: M = 212 a.u.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. Both thio­phene rings are disordered over two orientations by a rotation of approximately 180° around the C5—C3 bond. The final occupancy factors are 0.6957 (15) and 0.3043 (15). For the disordered thio­phene ring, bond lengths and angles were restrained to the target mean values observed in 3-CH2-thio­phene fragments in the CSD (Groom et al., 2016 ▸) and the same anisotropic displacement parameters were used for equivalent atoms. The H atoms attached to atoms N1 and N4 were found in a difference density Fourier map and refined freely. The other H atoms were placed at calculated positions and refined in riding mode, with C—H distances of 0.95 (aromatic) and 0.99 Å (CH2), and isotropic displacement parameters equal to 1.2U eq of the parent atoms. In the final cycles of refinement, two reflections showing very poor agreement were omitted as outliers.
Table 2

Experimental details

Crystal data
Chemical formulaC7H8N4S2
M r 212.29
Crystal system, space groupMonoclinic, P21/n
Temperature (K)100
a, b, c (Å)7.6904 (4), 13.0429 (7), 9.0220 (4)
β (°)90.081 (2)
V3)904.95 (8)
Z 4
Radiation typeMo Kα
μ (mm−1)0.54
Crystal size (mm)0.32 × 0.20 × 0.08
 
Data collection
DiffractometerBruker APEXII CCD
Absorption correctionMulti-scan (SADABS; Bruker, 2014)
T min, T max 0.710, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections27159, 2784, 2536
R int 0.025
(sin θ/λ)max−1)0.718
 
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S 0.027, 0.071, 1.05
No. of reflections2784
No. of parameters143
No. of restraints20
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3)0.43, −0.35

Computer programs: APEX2 (Bruker, 2014 ▸), SAINT (Bruker, 2013 ▸), SHELXS97 (Sheldrick, 2008 ▸), SHELXL2014 (Sheldrick, 2015 ▸) and OLEX2 (Dolomanov et al., 2009 ▸).

Crystal structure: contains datablock(s) I. DOI: 10.1107/S2056989017012191/zp2023sup1.cif Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989017012191/zp2023Isup2.hkl Click here for additional data file. Supporting information file. DOI: 10.1107/S2056989017012191/zp2023Isup3.cml CCDC reference: 1570281 Additional supporting information: crystallographic information; 3D view; checkCIF report
C7H8N4S2F(000) = 440
Mr = 212.29Dx = 1.558 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 7.6904 (4) ÅCell parameters from 9996 reflections
b = 13.0429 (7) Åθ = 3.1–30.7°
c = 9.0220 (4) ŵ = 0.54 mm1
β = 90.081 (2)°T = 100 K
V = 904.95 (8) Å3Block, colorless
Z = 40.32 × 0.20 × 0.08 mm
Bruker APEXII CCD diffractometer2536 reflections with I > 2σ(I)
φ and ω scansRint = 0.025
Absorption correction: multi-scan (SADABS; Bruker, 2014)θmax = 30.7°, θmin = 2.8°
Tmin = 0.710, Tmax = 0.746h = −11→11
27159 measured reflectionsk = −18→18
2784 independent reflectionsl = −12→12
Refinement on F220 restraints
Least-squares matrix: fullHydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.027H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.071w = 1/[σ2(Fo2) + (0.0367P)2 + 0.3687P] where P = (Fo2 + 2Fc2)/3
S = 1.05(Δ/σ)max = 0.001
2784 reflectionsΔρmax = 0.43 e Å3
143 parametersΔρmin = −0.35 e Å3
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.
xyzUiso*/UeqOcc. (<1)
S1A0.63885 (12)0.92996 (9)−0.14786 (11)0.02217 (15)0.6957 (15)
C1A0.7802 (4)0.9045 (2)0.0018 (3)0.0237 (6)0.6957 (15)
H1A0.8942520.9316120.0118380.028*0.6957 (15)
C2A0.7019 (5)0.8398 (5)0.1017 (6)0.0164 (5)0.6957 (15)
H2A0.7558680.8162790.1901840.020*0.6957 (15)
S1B0.7968 (3)0.92242 (15)−0.0160 (2)0.02217 (15)0.3043 (15)
C1B0.6169 (13)0.9240 (9)−0.1362 (11)0.0237 (6)0.3043 (15)
H1B0.6068460.962783−0.2249120.028*0.3043 (15)
C2B0.4838 (15)0.8542 (12)−0.0748 (15)0.0164 (5)0.3043 (15)
H2B0.3764670.840204−0.1229890.020*0.3043 (15)
C30.52961 (13)0.81192 (7)0.05711 (11)0.01448 (18)
C4A0.4817 (8)0.8574 (6)−0.0767 (6)0.0211 (5)0.6957 (15)
H4A0.3714710.847945−0.1223280.025*0.6957 (15)
C4B0.6897 (15)0.8412 (12)0.1007 (13)0.0211 (5)0.3043 (15)
H4B0.7399390.8179430.1909000.025*0.3043 (15)
C50.40813 (13)0.74501 (8)0.14692 (11)0.01518 (18)
H5A0.3306630.7064100.0792460.018*
H5B0.4768530.6948740.2049320.018*
C60.30116 (12)0.80879 (7)0.24957 (10)0.01347 (17)
N30.14624 (11)0.84574 (7)0.22259 (9)0.01560 (16)
N40.10978 (11)0.90487 (7)0.34611 (9)0.01478 (16)
H40.011 (2)0.9399 (12)0.3552 (18)0.030 (4)*
C70.23720 (12)0.90463 (7)0.44686 (10)0.01315 (17)
N20.36064 (10)0.84243 (6)0.38483 (9)0.01294 (15)
S20.25221 (3)0.96465 (2)0.61239 (3)0.01586 (7)
N10.52086 (11)0.81396 (7)0.44672 (10)0.01611 (17)
H1C0.5008 (19)0.7808 (12)0.5337 (17)0.023 (4)*
H1D0.576 (2)0.8692 (13)0.4631 (17)0.028 (4)*
U11U22U33U12U13U23
S1A0.0285 (3)0.0166 (2)0.0214 (2)0.0005 (2)0.0079 (2)0.00146 (16)
C1A0.0256 (11)0.0213 (13)0.0241 (12)0.0030 (9)−0.0027 (9)0.0011 (8)
C2A0.0091 (10)0.0171 (9)0.0229 (9)−0.0038 (9)0.0006 (7)−0.0041 (7)
S1B0.0285 (3)0.0166 (2)0.0214 (2)0.0005 (2)0.0079 (2)0.00146 (16)
C1B0.0256 (11)0.0213 (13)0.0241 (12)0.0030 (9)−0.0027 (9)0.0011 (8)
C2B0.0091 (10)0.0171 (9)0.0229 (9)−0.0038 (9)0.0006 (7)−0.0041 (7)
C30.0150 (4)0.0134 (4)0.0151 (4)0.0023 (3)0.0032 (3)−0.0021 (3)
C4A0.0270 (10)0.0233 (12)0.0131 (8)0.0096 (8)0.0020 (7)0.0019 (7)
C4B0.0270 (10)0.0233 (12)0.0131 (8)0.0096 (8)0.0020 (7)0.0019 (7)
C50.0145 (4)0.0144 (4)0.0167 (4)−0.0002 (3)0.0023 (3)−0.0024 (3)
C60.0131 (4)0.0131 (4)0.0142 (4)−0.0012 (3)0.0011 (3)0.0001 (3)
N30.0140 (4)0.0182 (4)0.0146 (4)0.0010 (3)0.0005 (3)−0.0022 (3)
N40.0124 (4)0.0169 (4)0.0151 (4)0.0027 (3)0.0001 (3)−0.0015 (3)
C70.0122 (4)0.0127 (4)0.0145 (4)0.0002 (3)0.0019 (3)0.0020 (3)
N20.0105 (3)0.0146 (4)0.0138 (3)0.0015 (3)0.0000 (3)0.0007 (3)
S20.01442 (12)0.01893 (13)0.01423 (12)0.00179 (8)−0.00036 (8)−0.00250 (8)
N10.0113 (4)0.0190 (4)0.0181 (4)0.0018 (3)−0.0029 (3)0.0020 (3)
S1Aa—C1A1.763 (4)C3—C4B1.347 (10)
C1Aa—H1A0.9500C3—C51.5143 (14)
C1Aa—C2A1.375 (5)C5—H5A0.9900
C2Aa—H2A0.9500C5—H5B0.9900
S1Bb—C1B1.757 (11)C5—C61.4929 (13)
C1Bb—H1B0.9500C6—N31.3077 (13)
C1Bb—C2B1.478 (12)C6—N21.3745 (12)
C2Bb—H2B0.9500N3—N41.3842 (11)
C2Aa—C31.431 (3)N4—H40.889 (17)
C2Bb—C31.357 (11)N4—C71.3356 (12)
S1Aa—C4A1.665 (5)C7—N21.3689 (12)
C4Aa—H4A0.9500C7—S21.6900 (10)
S1Bb—C4B1.707 (11)N2—N11.4021 (11)
C4Bb—H4B0.9500N1—H1C0.909 (15)
C3—C4A1.394 (5)N1—H1D0.849 (17)
C2Aa—C1Aa—S1A110.3 (3)C3—C2Bb—H2B123.2
C4Aa—S1Aa—C1A92.56 (19)C3—C5—H5B109.5
C2Aa—C1Aa—H1A124.8H5A—C5—H5B108.1
S1Aa—C1Aa—H1A124.8C3—C4Aa—H4A123.7
C1Aa—C2Aa—H2A123.9C3—C4Bb—H4B122.0
C2Bb—C1Bb—S1B107.9 (7)C6—C5—C3110.59 (8)
C4Bb—S1Bb—C1B90.4 (5)C6—C5—H5A109.5
S1Bb—C1Bb—H1B126.1C6—C5—H5B109.5
C2Bb—C1Bb—H1B126.1N3—C6—C5126.34 (9)
C1Bb—C2Bb—H2B123.2N3—C6—N2110.46 (8)
C1Aa—C2Aa—C3112.2 (3)N2—C6—C5123.07 (9)
S1Aa—C4Aa—H4A123.7C6—N3—N4103.94 (8)
S1Bb—C4Bb—H4B122.0N3—N4—H4122.3 (11)
C4Aa—C3—C2A112.3 (3)C7—N4—N3113.41 (8)
C4Bb—C3—C2B112.1 (6)C7—N4—H4124.3 (11)
C4Aa—C3—C5123.1 (2)N4—C7—N2103.39 (8)
C2Aa—C3—C5124.6 (2)N4—C7—S2130.50 (8)
C2Bb—C3—C5122.9 (4)N2—C7—S2126.10 (7)
C4Bb—C3—C5124.8 (4)C6—N2—N1124.07 (8)
C3—C5—H5A109.5C7—N2—C6108.79 (8)
C3—C4Aa—S1A112.6 (3)C7—N2—N1127.13 (8)
C3—C2Aa—H2A123.9N2—N1—H1C108.7 (9)
C3—C4Bb—S1B115.9 (7)N2—N1—H1D106.5 (11)
C3—C2Bb—C1B113.6 (7)H1C—N1—H1D109.7 (14)
C4Aa—S1Aa—C1Aa—C2Aa0.5 (5)C2Aa—C3—C5—C689.6 (3)
S1Aa—C1Aa—C2Aa—C3−0.2 (6)C3—C5—C6—N393.21 (12)
C4Bb—S1Bb—C1Bb—C2Bb−2.2 (12)C3—C5—C6—N2−82.26 (11)
S1Bb—C1Bb—C2Bb—C32.7 (17)N2—C6—N3—N40.31 (11)
C1Bb—C2Bb—C3—C4Bb−1.8 (18)C5—C6—N3—N4−175.64 (9)
C1Bb—C2Bb—C3—C5174.8 (8)C6—N3—N4—C7−0.17 (11)
C1Aa—C2Aa—C3—C4Aa−0.3 (6)N3—N4—C7—N2−0.04 (11)
C1Aa—C2Aa—C3—C5−177.5 (3)N3—N4—C7—S2179.78 (8)
C2Aa—C3—C4Aa—S1Aa0.7 (7)N4—C7—N2—C60.23 (10)
C5—C3—C4Aa—S1Aa178.0 (2)S2—C7—N2—C6−179.61 (7)
C1Aa—S1Aa—C4Aa—C3−0.7 (5)N4—C7—N2—N1−178.40 (9)
C2Bb—C3—C4Bb—S1Bb0.0 (16)S2—C7—N2—N11.77 (14)
C5—C3—C4Bb—S1Bb−176.6 (5)N3—C6—N2—C7−0.36 (11)
C1Bb—S1Bb—C4Bb—C31.4 (12)C5—C6—N2—C7175.75 (9)
C4Bb—C3—C5—C687.4 (9)N3—C6—N2—N1178.32 (9)
C2Bb—C3—C5—C6−88.8 (10)C5—C6—N2—N1−5.57 (14)
C4Aa—C3—C5—C6−87.3 (4)
D—H···AD—HH···AD···AD—H···A
N1—H1C···N3i0.909 (15)2.622 (15)3.3847 (13)142.0 (12)
N1—H1D···S2ii0.849 (17)2.628 (16)3.4163 (9)154.9 (13)
N4—H4···S2iii0.890 (16)2.395 (15)3.2847 (9)178.2 (12)
C1B—H1B···Cg3iv0.952.783.503 (11)134
  4 in total

1.  Towards quantitative analysis of intermolecular interactions with Hirshfeld surfaces.

Authors:  Joshua J McKinnon; Dylan Jayatilaka; Mark A Spackman
Journal:  Chem Commun (Camb)       Date:  2007-10-07       Impact factor: 6.222

2.  A short history of SHELX.

Authors:  George M Sheldrick
Journal:  Acta Crystallogr A       Date:  2007-12-21       Impact factor: 2.290

3.  Crystal structure refinement with SHELXL.

Authors:  George M Sheldrick
Journal:  Acta Crystallogr C Struct Chem       Date:  2015-01-01       Impact factor: 1.172

4.  The Cambridge Structural Database.

Authors:  Colin R Groom; Ian J Bruno; Matthew P Lightfoot; Suzanna C Ward
Journal:  Acta Crystallogr B Struct Sci Cryst Eng Mater       Date:  2016-04-01
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1.  Synthesis and characterization of some novel polythiophene derivatives containing pyrazoline.

Authors:  Vu Quoc Trung; Tran Thi Thuy Duong; Nguyen Thi Dua; Nguyen Ngoc Linh; Lai Dang Cuong; Dao Phuong Thao; Vo Khac Huy; Nguyen Hoang Ha Phuong; Nguyen Hien; Duong Khanh Linh; Vu Quoc Manh; Nguyen Thuy Chinh; Thai Hoang; Luc Van Meervelt
Journal:  Des Monomers Polym       Date:  2022-06-09       Impact factor: 3.718

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