research communications
Synthesis and E)-1,2-bis[2-(methylsulfanyl)phenyl]diazene
of (aInstitute for Organic and Analytic Chemistry, University Bremen, Leobener Strasse 7, 28359 Bremen, Germany, bMAPEX, Center for Materials and Processes, University of Bremen, Bibliothekstr. 1, 28359 Bremen, Germany, and cInstitute for Inorganic Chemistry and Crystallography, University of Bremen, Leobener Strasse 7, 28359 Bremen, Germany
*Correspondence e-mail: staubitz@uni-bremen.de
The title compound, C14H14N2S2, was obtained by transmetallation of 2,2′-bis(trimethylstannyl)azobenzene with methyl lithium, and subsequent quenching with dimethyl disulfide. The comprises two half-molecules, the other halves being completed by inversion symmetry at the midpoint of the azo group. The two molecules show only slight differences with respect to N=N, S—N and aromatic C=C bonds or angles. Hirshfeld surface analysis reveals that except for one weak H⋯S interaction, intermolecular interactions are dominated by only.
1. Chemical context
The molecular switch azobenzene can undergo isomerization from its thermodynamically stable trans form to the metastable cis form using external stimuli such as light, temperature or pressure. Azobenzenes are common motifs in dyes because of their high thermal and photochemical stability (Yesodha et al., 2004; Lagrasta et al., 1997). We recently presented methods to substitute azobenzenes in the ortho, meta and para-positions with trimethyltin as a novel functionalization method, giving rise to a dual tin–lithium exchange (Strüben et al., 2014, 2015; Hoffmann et al., 2019). In particular, we described the effect on the diortho-substitution on azobenzenes with trimethyl-tetrels and the resulting effects on the switching properties (Hoffmann et al., 2019). In this context, we present here a novel diortho-substituted azobenzene, (C7H7NS)2, (I), bearing two methylsulfide groups.
2. Structural commentary
The Ia and Ib), the other halves being completed by application of inversion symmetry. The midpoints of the N=N bonds are located on inversion centres, resulting in a trans-configuration for the central N=N bonds (Fig. 1). As indicated by the C6A—C1A—N1A—N1Ai and C6B—C1B—N1B—N1Bii [symmetry codes: (i) −x, 1 − y, −z; (ii) 1 − x, 1 − y, 1 − z] torsion angles of 13.2 (2) and −5.3 (2)°, respectively, in both molecules the phenyl rings are twisted slightly with respect to the azo unit. A weak distortion is also found for the N1—C1—C2—S1 torsion angles of −3.06 (16)° for Ia and −2.06 (15)° for Ib. The N=N bond lengths differ marginally [1.255 (2) Å for Ia, 1.264 (2) Å for Ib], as do comparable C—C bonds. For example, the C1—C2 bond in Ia is at 1.408 (2) Å slightly shorter than Ib [1.415 (2) Å]. In comparison, this bond is longer than all other C—C distances in the ring because of repulsion of the nitrogen and the sulfur atoms attached to C1 and C2, respectively. In both molecules, the S⋯N distances [2.8625 (13) Å for Ia, 2.8761 (11) Å for Ib] are too long to be considered as attractive interactions. Fig. 2 represents an overlay plot of the two molecules, showing there are only slight conformational differences.
of the title compound consists of two half-molecules (3. Supramolecular features and Hirshfeld surface analysis
The packing of Ia and Ib in the crystal is shown in Fig. 3. Despite the presence of phenyl rings and a parallel arrangement of the molecules, only weak offset π–π interactions are observed; the shortest centroid-to-centroid distance is Cg2⋯Cg2(1 − x, 1 − y, −z) = 3.7525 (8) Å with a slippage of 1.422 Å. To further investigate the intermolecular interactions, Hirshfeld surfaces (Hirshfeld, 1977) and fingerprint plots were generated for both molecules using CrystalExplorer17.5 (McKinnon et al., 2004). Hirshfeld surface analysis depicts intermolecular interactions by different colors, representing short or long contacts and further the relative strength of the interaction. The generated Hirshfeld surfaces mapped over dnorm and the shape index are shown in Fig. 4 for Ia and in Fig. 5 for Ib. Whereas in Ia a significant intermolecular interaction is not apparent, characteristic red spots near S1B and H5B indicate weak S⋯H interactions in Ib. The respective supramolecular arrangement is shown in Fig. 6. The sulfur atom S1B interacts with a phenyl proton (H4B) of another molecule of Ib (S⋯H distance = 2.811 Å). The two-dimensional fingerprint plots for molecule Ib for quantification of the contributions of each type of non-covalent interaction to the Hirshfeld surface (McKinnon et al., 2007) are given in Fig. 7. The packing is dominated by H⋯H contacts, representing van der Waals interactions (44.5% contribution to the surface), followed by C⋯H and S⋯H interactions, which contribute with 24.0% and 18.1%, respectively. The contributions of the N⋯H (8.6%) and C⋯C (4.8%) interactions are less significant.
4. Database survey
A search of the Cambridge Structural Database (CSD version 5.4.0; update August 2019; Groom et al., 2016) revealed no azobenzene-based structures that contain methyl thioethers. However, some general ortho-substituted azobenzenes have been deposited (Yamamura et al., 2008; Kano et al., 2001; Hoffmann et al., 2019). Additionally, some diortho-substituted thioazoxybenzenes were reported previously (Szczygelska-Tao et al., 1999; Kertmen et al., 2013). For the structure of an azobenzene compound with an inversion centre at the N=N bond, see: Bohle et al. (2007).
5. Synthesis and crystallization
The synthesis of 2,2′-bis(trimethylstannyl)azobenzene was recently described (Hoffmann et al., 2019). For further details of a similar transmetallation of a stannylated azobenzene, see: Strüben et al. (2015). Dimethyl disulfide (99%) was purchased from Acros Organics and was used without further purification. Methyl lithium (1.88 M in diethyl ether, titrated against 2,2′-bipyridine) was purchased from Acros Organics. THF was purchased from VWR and was dried and degassed with a solvent purification system by Inert Technology.
2,2′-bis(Methylthio)azobenzene
In an inert reaction tube, 2,2-bis(trimethylstannyl)azobenzene (200 mg, 0.39 mmol) was dissolved under Schlenk conditions in THF (12.5 ml) and cooled to 195 K. Then MeLi (1.88 M in diethyl ether, 0.63 ml, 1.18 mmol) was added within 5 min and after 1.5 h at this temperature, dimethyl disulfide (0.35 ml, 3.94 mmol) was added in one ration. The reaction mixture was warmed to 298 K over 14 h and the solvent was removed under reduced pressure. The obtained orange solid was purified in a silica column (Merck, 0.015–0.40 mm) with a gradient of eluents from n-pentane to dichloromethane giving dark-orange crystals (31 mg, 0.11 mmol; yield 29%). Single crystals suitable for X-ray analysis were obtained by slow evaporation from a saturated n-heptane solution.
1H NMR (500 MHz, CDCl3): δ = 7.76 (dd, 3J = 8.1 Hz, 4J = 1.4 Hz, 2H, H6), 7.40 (td, 3J = 8.0, 7.3 Hz, 4J = 1.4 Hz, 2H, H4), 7.32 (dd, 3J = 8.0 Hz, 4J = 1.1 Hz, 2H, H3), 7.20 (td, 3J = 8.1, 7.3Hz, 4J = 1.1 Hz, 2H, H5), 2.53 (s, 6H, H7) ppm.
13C{1H} NMR (125 MHz, CDCl3): δ = 149.08 (C1), 141.00 (C2), 131.56 (C4), 124.81 (C3), 124.75 (C5), 118.02 (C6), 15.02 (C7) ppm.
HRMS (EI, 70 eV, MAT95, direct): m/z: calculated for C14H14N2S2+ 274.05929 found 274.05944.
MS (EI): m/z 273.9 (5%) [M]+, 258.9 (100%) [M − CH3]+, 243.9 (5%) [M − C2H6]+, 107.9 (13%) [M − C8H10N2S]+.
IR (ATR): ν = 3059 (w), 2986 (w), 2961 (w), 2918 (w), 2852 (w), 1575 (m), 1561 (w), 1457 (m), 1433 (s), 1298 (w), 1249 (w), 1217 (m), 1162 (m), 1065 (s), 1035 (m), 951 (m), 863 (w), 803 (w), 761 (s), 726 (s), 674 (s) cm−1.
M.p.: 429 K
Rf: (n-pentane: dichloromethane 3:1): 0.55.
6. Refinement
Crystal data, data collection and structure . All H atoms were positioned geometrically and refined using a riding model: C—H = 0.95–0.98 Å with Uiso(H) = 1.5Ueq (C-methyl) and 1.2Ueq(C) (C-phenyl).
details are summarized in Table 1Supporting information
https://doi.org/10.1107/S2056989019014592/wm5522sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989019014592/wm5522Isup2.hkl
Data collection: APEX3 (Bruker, 2016); cell
SAINT (Bruker, 2016); data reduction: SAINT (Bruker, 2016); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).C14H14N2S2 | F(000) = 576 |
Mr = 274.39 | Dx = 1.380 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 13.0656 (5) Å | Cell parameters from 9874 reflections |
b = 12.1787 (4) Å | θ = 2.3–28.3° |
c = 8.3471 (3) Å | µ = 0.39 mm−1 |
β = 96.154 (1)° | T = 100 K |
V = 1320.55 (8) Å3 | Block, dark orange |
Z = 4 | 0.21 × 0.18 × 0.17 mm |
Bruker D8 Venture CMOS diffractometer | 3292 independent reflections |
Radiation source: microfocus sealed X-ray tube, Incoatec Iµs | 2842 reflections with I > 2σ(I) |
Mirror optics monochromator | Rint = 0.065 |
Detector resolution: 7.9 pixels mm-1 | θmax = 28.3°, θmin = 2.3° |
ω and φ scans | h = −17→17 |
Absorption correction: multi-scan (SADABS; Krause et al., 2015) | k = −16→16 |
Tmin = 0.580, Tmax = 0.746 | l = −11→10 |
21000 measured reflections |
Refinement on F2 | Primary atom site location: dual |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.034 | H-atom parameters constrained |
wR(F2) = 0.089 | w = 1/[σ2(Fo2) + (0.0401P)2 + 0.6716P] where P = (Fo2 + 2Fc2)/3 |
S = 1.03 | (Δ/σ)max < 0.001 |
3292 reflections | Δρmax = 0.44 e Å−3 |
165 parameters | Δρmin = −0.38 e Å−3 |
0 restraints |
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. |
x | y | z | Uiso*/Ueq | ||
S1A | 0.03738 (3) | 0.22038 (3) | 0.07109 (4) | 0.01750 (10) | |
N1A | 0.00557 (9) | 0.45111 (10) | 0.02308 (14) | 0.0144 (2) | |
C1A | 0.09596 (10) | 0.43239 (11) | 0.13020 (16) | 0.0133 (3) | |
C2A | 0.12139 (10) | 0.32133 (11) | 0.15962 (16) | 0.0136 (3) | |
C3A | 0.21227 (10) | 0.29785 (12) | 0.25937 (17) | 0.0163 (3) | |
H3A | 0.232873 | 0.223733 | 0.278065 | 0.020* | |
C4A | 0.27191 (10) | 0.38209 (12) | 0.33050 (17) | 0.0175 (3) | |
H4A | 0.333363 | 0.364884 | 0.397179 | 0.021* | |
C5A | 0.24372 (10) | 0.49160 (12) | 0.30637 (17) | 0.0170 (3) | |
H5A | 0.284385 | 0.548538 | 0.358432 | 0.020* | |
C6A | 0.15556 (10) | 0.51642 (12) | 0.20540 (16) | 0.0153 (3) | |
H6A | 0.135717 | 0.590824 | 0.187411 | 0.018* | |
C7A | 0.09736 (12) | 0.09607 (12) | 0.15119 (19) | 0.0212 (3) | |
H7AA | 0.108296 | 0.100874 | 0.268985 | 0.032* | |
H7AB | 0.163749 | 0.086347 | 0.108405 | 0.032* | |
H7AC | 0.052690 | 0.033332 | 0.119805 | 0.032* | |
S1B | 0.68646 (3) | 0.36826 (3) | 0.29648 (4) | 0.01522 (10) | |
N1B | 0.53057 (8) | 0.47643 (9) | 0.45728 (13) | 0.0111 (2) | |
C1B | 0.54712 (9) | 0.53356 (10) | 0.31394 (15) | 0.0107 (2) | |
C2B | 0.62096 (9) | 0.48706 (11) | 0.22188 (15) | 0.0109 (2) | |
C3B | 0.63884 (10) | 0.53770 (11) | 0.07713 (16) | 0.0135 (3) | |
H3B | 0.688084 | 0.507481 | 0.013715 | 0.016* | |
C4B | 0.58521 (10) | 0.63170 (11) | 0.02550 (16) | 0.0149 (3) | |
H4B | 0.597271 | 0.664586 | −0.073966 | 0.018* | |
C5B | 0.51371 (10) | 0.67861 (11) | 0.11794 (16) | 0.0141 (3) | |
H5B | 0.478373 | 0.743923 | 0.082900 | 0.017* | |
C6B | 0.49478 (10) | 0.62917 (11) | 0.26090 (16) | 0.0121 (3) | |
H6B | 0.445749 | 0.660464 | 0.323699 | 0.015* | |
C7B | 0.77056 (12) | 0.33890 (13) | 0.1449 (2) | 0.0230 (3) | |
H7BA | 0.729477 | 0.327171 | 0.041043 | 0.035* | |
H7BB | 0.810613 | 0.272618 | 0.174984 | 0.035* | |
H7BC | 0.817418 | 0.400922 | 0.136102 | 0.035* |
U11 | U22 | U33 | U12 | U13 | U23 | |
S1A | 0.01446 (17) | 0.01894 (19) | 0.01851 (19) | −0.00155 (13) | −0.00094 (13) | −0.00187 (13) |
N1A | 0.0110 (5) | 0.0196 (6) | 0.0125 (5) | 0.0009 (4) | 0.0008 (4) | −0.0003 (4) |
C1A | 0.0098 (6) | 0.0203 (7) | 0.0100 (6) | −0.0002 (5) | 0.0022 (5) | 0.0005 (5) |
C2A | 0.0102 (6) | 0.0199 (7) | 0.0111 (6) | −0.0010 (5) | 0.0032 (5) | −0.0020 (5) |
C3A | 0.0129 (6) | 0.0205 (7) | 0.0155 (7) | 0.0018 (5) | 0.0011 (5) | 0.0019 (5) |
C4A | 0.0112 (6) | 0.0267 (7) | 0.0139 (6) | 0.0008 (5) | −0.0013 (5) | 0.0017 (6) |
C5A | 0.0136 (6) | 0.0250 (7) | 0.0124 (6) | −0.0033 (5) | 0.0013 (5) | −0.0021 (5) |
C6A | 0.0141 (6) | 0.0194 (7) | 0.0128 (6) | −0.0005 (5) | 0.0029 (5) | 0.0000 (5) |
C7A | 0.0238 (7) | 0.0182 (7) | 0.0215 (7) | −0.0003 (6) | 0.0026 (6) | 0.0015 (6) |
S1B | 0.01542 (17) | 0.01406 (17) | 0.01718 (18) | 0.00275 (12) | 0.00642 (13) | 0.00248 (12) |
N1B | 0.0103 (5) | 0.0140 (5) | 0.0090 (5) | −0.0019 (4) | 0.0012 (4) | −0.0012 (4) |
C1B | 0.0097 (5) | 0.0135 (6) | 0.0088 (6) | −0.0028 (5) | 0.0008 (5) | −0.0014 (5) |
C2B | 0.0096 (5) | 0.0112 (6) | 0.0115 (6) | −0.0013 (5) | 0.0001 (5) | −0.0013 (5) |
C3B | 0.0124 (6) | 0.0176 (6) | 0.0111 (6) | −0.0014 (5) | 0.0042 (5) | −0.0018 (5) |
C4B | 0.0160 (6) | 0.0180 (7) | 0.0108 (6) | −0.0030 (5) | 0.0020 (5) | 0.0019 (5) |
C5B | 0.0142 (6) | 0.0146 (6) | 0.0130 (6) | 0.0002 (5) | 0.0000 (5) | 0.0011 (5) |
C6B | 0.0109 (6) | 0.0148 (6) | 0.0106 (6) | −0.0011 (5) | 0.0011 (5) | −0.0020 (5) |
C7B | 0.0229 (7) | 0.0210 (7) | 0.0276 (8) | 0.0061 (6) | 0.0144 (6) | 0.0013 (6) |
S1A—C2A | 1.7574 (14) | S1B—C2B | 1.7605 (13) |
S1A—C7A | 1.8002 (15) | S1B—C7B | 1.7983 (15) |
N1A—N1Ai | 1.255 (2) | N1B—N1Bii | 1.264 (2) |
N1A—C1A | 1.4211 (17) | N1B—C1B | 1.4205 (16) |
C1A—C2A | 1.4080 (19) | C1B—C2B | 1.4145 (18) |
C1A—C6A | 1.3940 (19) | C1B—C6B | 1.3981 (18) |
C2A—C3A | 1.4046 (18) | C2B—C3B | 1.3983 (18) |
C3A—H3A | 0.9500 | C3B—H3B | 0.9500 |
C3A—C4A | 1.383 (2) | C3B—C4B | 1.3866 (19) |
C4A—H4A | 0.9500 | C4B—H4B | 0.9500 |
C4A—C5A | 1.393 (2) | C4B—C5B | 1.3961 (19) |
C5A—H5A | 0.9500 | C5B—H5B | 0.9500 |
C5A—C6A | 1.3857 (19) | C5B—C6B | 1.3824 (19) |
C6A—H6A | 0.9500 | C6B—H6B | 0.9500 |
C7A—H7AA | 0.9800 | C7B—H7BA | 0.9800 |
C7A—H7AB | 0.9800 | C7B—H7BB | 0.9800 |
C7A—H7AC | 0.9800 | C7B—H7BC | 0.9800 |
C2A—S1A—C7A | 101.82 (7) | C2B—S1B—C7B | 103.00 (7) |
N1Ai—N1A—C1A | 113.98 (14) | N1Bii—N1B—C1B | 114.53 (14) |
C2A—C1A—N1A | 115.37 (12) | C2B—C1B—N1B | 115.83 (11) |
C6A—C1A—N1A | 123.50 (13) | C6B—C1B—N1B | 124.14 (11) |
C6A—C1A—C2A | 121.11 (12) | C6B—C1B—C2B | 120.02 (12) |
C1A—C2A—S1A | 118.27 (10) | C1B—C2B—S1B | 118.09 (10) |
C3A—C2A—S1A | 123.84 (11) | C3B—C2B—S1B | 123.24 (10) |
C3A—C2A—C1A | 117.89 (12) | C3B—C2B—C1B | 118.67 (12) |
C2A—C3A—H3A | 119.8 | C2B—C3B—H3B | 119.8 |
C4A—C3A—C2A | 120.33 (13) | C4B—C3B—C2B | 120.46 (12) |
C4A—C3A—H3A | 119.8 | C4B—C3B—H3B | 119.8 |
C3A—C4A—H4A | 119.3 | C3B—C4B—H4B | 119.6 |
C3A—C4A—C5A | 121.35 (13) | C3B—C4B—C5B | 120.79 (12) |
C5A—C4A—H4A | 119.3 | C5B—C4B—H4B | 119.6 |
C4A—C5A—H5A | 120.4 | C4B—C5B—H5B | 120.3 |
C6A—C5A—C4A | 119.12 (13) | C6B—C5B—C4B | 119.42 (13) |
C6A—C5A—H5A | 120.4 | C6B—C5B—H5B | 120.3 |
C1A—C6A—H6A | 119.9 | C1B—C6B—H6B | 119.7 |
C5A—C6A—C1A | 120.10 (13) | C5B—C6B—C1B | 120.63 (12) |
C5A—C6A—H6A | 119.9 | C5B—C6B—H6B | 119.7 |
S1A—C7A—H7AA | 109.5 | S1B—C7B—H7BA | 109.5 |
S1A—C7A—H7AB | 109.5 | S1B—C7B—H7BB | 109.5 |
S1A—C7A—H7AC | 109.5 | S1B—C7B—H7BC | 109.5 |
H7AA—C7A—H7AB | 109.5 | H7BA—C7B—H7BB | 109.5 |
H7AA—C7A—H7AC | 109.5 | H7BA—C7B—H7BC | 109.5 |
H7AB—C7A—H7AC | 109.5 | H7BB—C7B—H7BC | 109.5 |
S1A—C2A—C3A—C4A | −177.02 (11) | S1B—C2B—C3B—C4B | −179.51 (10) |
N1Ai—N1A—C1A—C2A | −168.19 (14) | N1Bii—N1B—C1B—C2B | 175.48 (13) |
N1Ai—N1A—C1A—C6A | 13.2 (2) | N1Bii—N1B—C1B—C6B | −5.3 (2) |
N1A—C1A—C2A—S1A | −3.06 (16) | N1B—C1B—C2B—S1B | −2.06 (15) |
N1A—C1A—C2A—C3A | 177.45 (12) | N1B—C1B—C2B—C3B | 178.30 (11) |
N1A—C1A—C6A—C5A | −178.94 (12) | N1B—C1B—C6B—C5B | −178.56 (12) |
C1A—C2A—C3A—C4A | 2.4 (2) | C1B—C2B—C3B—C4B | 0.11 (19) |
C2A—C1A—C6A—C5A | 2.5 (2) | C2B—C1B—C6B—C5B | 0.61 (19) |
C2A—C3A—C4A—C5A | 0.3 (2) | C2B—C3B—C4B—C5B | 1.1 (2) |
C3A—C4A—C5A—C6A | −1.8 (2) | C3B—C4B—C5B—C6B | −1.4 (2) |
C4A—C5A—C6A—C1A | 0.4 (2) | C4B—C5B—C6B—C1B | 0.54 (19) |
C6A—C1A—C2A—S1A | 175.63 (10) | C6B—C1B—C2B—S1B | 178.71 (10) |
C6A—C1A—C2A—C3A | −3.86 (19) | C6B—C1B—C2B—C3B | −0.94 (18) |
C7A—S1A—C2A—C1A | −176.89 (11) | C7B—S1B—C2B—C1B | −179.91 (10) |
C7A—S1A—C2A—C3A | 2.57 (13) | C7B—S1B—C2B—C3B | −0.28 (13) |
Symmetry codes: (i) −x, −y+1, −z; (ii) −x+1, −y+1, −z+1. |
Funding information
The authors would like to thank Special Research Area 677 `Function by Switching' of the Deutsche Forschungsgemeinschaft (DFG), Project C14, for financial support. This research has been supported by the Institutional Strategy of the University of Bremen, funded by the German Excellence Initiative.
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