Article pubs.acs.org/IC
Crystal Structures, Magnetic Properties, and Electrochemical Properties of Coordination Polymers Based on the Tetra(4-pyridyl)tetrathiafulvalene Ligand Hai-Ying Wang,† Yue Wu,† Chanel F. Leong,‡ Deanna M. D’Alessandro,‡ and Jing-Lin Zuo*,† †
State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, People’s Republic of China ‡ School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia S Supporting Information *
ABSTRACT: Seven new coordination polymers based on the redox-active tetra(4-pyridyl)-tetrathiafulvalene ligand (TTF(py)4) and different transition-metal ions, namely, {[Cu(hfac)2][TTF(py)4]·2(CH2Cl2)}n (1), {[Co(acac)2][TTF(py)4]0.5·(CHCl3)}n (2), {[Mn(hfac)2][TTF(py)4]0.5}n (3), {[Cu 2 (OAc) 4 ][TTF(py) 4 ] 0 . 5 ·1.5(CHCl 3 )·0.5(H 2 O)· (CH3CN)}n (4), {[Mn(SCN)2][TTF(py)4]·6(CH2Cl2)}n (5), {[Mn(SeCN)Cl][TTF(py)4]}n (6), and {Cu2[TTF(py)4]2· (ClO4)2·2.5(CH2Cl2)·1.5(CH3CN)}n (7), were synthesized and characterized. The tetrapyridyl ligand coordinates to metal ions in a bidentate or tetradentate fashion, forming complexes 1−7 with different structures. Complex 1 exhibits a onedimensional chain structure. Complexes 2, 3, and 4 possess similar (4,2)-connected binodal two-dimensional networks, while complexes 5 and 6 have similar (4,4)-connected binodal two-dimensional networks with two different rings. Complex 7 shows a 2-fold interpenetrated (4,4)-connected binodal PtS-type three-dimensional framework. Meanwhile, these complexes feature diverse nonclassical hydrogen bonding interactions. In addition, magnetic and solid-state electrochemical properties for typical complexes have been studied.
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INTRODUCTION Metal−organic frameworks (MOFs) constructed from metal ions or clusters and functionalized organic ligands have received considerable attention in recent years for their intriguing structures and their potential applications in gas storage, sensing, catalysis, luminescence, and magnetism, among others.1−6 The integration of ligands with appropriate geometries and functionalities are important in directing the structure and properties of frameworks. Tetrathiafulvalene (TTF), a sulfur-rich conjugated core, can be easily and reversibly oxidized into its corresponding cationic radical (TTF• +) and dictation (TTF2+) and has been studied extensively as a component of conductive and optoelectronic materials.7−10 Many attempts have been made to derivatize TTF with functional groups that can bind to transition-metal ions. It is well-known that pyridyl groups have a strong ability to coordinate different metal ions.11−16 In this context, the association of redox-active pyridyl ligands containing the TTF core with metallic centers is an effective approach to synthesize interesting multifunctional materials.17 Over the past decade, monopyridine,14,18 bipyridine.19,20 and tetrapyridine21 organic ligands in which the pyridyl group is directly linked to the TTF moiety, and the corresponding complexes of these ligands have © XXXX American Chemical Society
been reported. These types of coordination compounds containing TTF show zero-dimensional (0D) or one-dimensional (1D) crystal structures and electrochemical activity resulting from the TTF moiety. Recently, Therrien and Sallé et al. have successfully prepared the interesting tetrapyridyl-TTF ligand (TTF(py)4; see Scheme 1).22 Based on this ligand, four arene ruthenium(II) complexes (one molecular cube and three metallaplates) have been studied. The incorporation of magnetic moment carriers such as paramagnetic ions into MOFs allows for the development of novel multifunctional materials with additional magnetic Scheme 1. TTF(py)4 Ligand Used in the Construction of Coordination Polymers
Received: August 7, 2015
A
DOI: 10.1021/acs.inorgchem.5b01803 Inorg. Chem. XXXX, XXX, XXX−XXX
a
B
2 C24H23Cl3CoN2O4S2 632.84 triclinic P1̅ 7.6741(2) 11.7196(5) 15.9558(7) 85.945(4) 81.135(3) 86.628(3) 1412.67(10) 2 1.488 100.01(10) 9.032 3.79−67.08 646 5035/0/332 1.040 0.0456, 0.1075 0.0620, 0.1186
1
C38H22Cl4CuF12N4O4S4 1160.18 triclinic P1̅ 7.532(4) 11.604(6) 14.208(7) 81.018(9) 79.496(8) 73.902(8) 1165.8(10) 1 1.653 293(2) 0.969 1.47−25.50 579 4297/8/301 1.030 0.0688, 0.1934 0.0930, 0.2156
R1 = ∑∥F0| − |Fc∥/∑|F0|. bwR2 = [∑w(F02 − Fc2)2/∑w(F02)2]1/2.
formula fw crystal system space group a, Å b, Å c, Å α, deg β, deg γ, deg V, Å3 Z ρcalcd, g cm−3 T, K μ, mm−1 θ, deg F(000) data/restraints/parameters GOF (F2) R1,a wR2b (I > 2σ(I)) R1,a wR2b (all data)
Table 1. Crystallographic Data for Complexes 1−7 3 C23H10MnF12N2O4S2 725.39 triclinic P1̅ 6.4766(4) 13.0615(9) 15.8126(12) 92.587(6) 97.091(6) 93.764(5) 1322.63(16) 2 1.821 99.95(18) 0.778 2.96−26.37 718 5391/0/400 1.045 0.0467, 0.0883 0.07050, 0.1036
4 C24H25Cl3Cu2N3O8.5S2 789.02 monoclinic P21/c 7.2429(2) 20.6964(6) 24.9676(6) 90 91.705(2) 90 3741.03(17) 4 1.401 100.00(10) 4.798 3.54−67.07 1596 6654/24/390 1.069 0.0721, 0.2107 0.0839, 0.2225
5 C34H28C12MnN6S6 1193.32 monoclinic P21/n 16.5175(11) 9.7287(8) 17.8499(19) 90 116.325(7) 90 2570.9(4) 2 1.542 100.00(10) 1.157 3.54−70.88 1198 4505/0/268 1.143 0.1629, 0.4127 0.2117, 0.4410
6 C27H16ClMnN5S4Se 708.04 orthorhombic P212121 9.74106(18) 14.7395(6) 31.8411(6) 90 90 90 4571.7(2) 4 1.029 100.00(10) 5.645 3.30−65.08 1412 7685/175/349 1.253 0.1240, 0.3181 0.1406, 0.3366
7 C57.50H41.50Cl7Cu2N9.50O8S8 1625.21 monoclinic P21/n 15.8574(5) 19.3325(11) 25.2962(10) 90 102.694(4) 90 7565.3(6) 2 1.427 100.00(10) 1.084 2.98−25.12 3288 13472/21/867 1.115 0.0812, 0.2388 0.0987, 0.2595
Inorganic Chemistry Article
DOI: 10.1021/acs.inorgchem.5b01803 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry
Figure 1. (a) Coordination environment for Cu(II) ion in 1 (30% ellipsoids). (b) View of the one-dimensional (1D) chain in 1. Synthesis of {[Mn(SCN)2][TTF(py)4]·6(CH2Cl2)}n (5). A mixture of MnCl2·2H2O (1.6 mg, 0.01 mmol) and KSCN (2 mg, 0.02 mmol) in CH3OH (1.5 mL) was stirred for 10 min and then filtrated. The solution was layered onto a solution of TTF(py)4 (2.5 mg, 0.005 mmol) in CH2Cl2 (1.5 mL). The solutions were left for ∼5 days at room temperature, and light red crystals were obtained. Yield: 68% (based on TTF(py)4). Anal. Calcd for C34H28Cl12MnN6S6: C, 34.22; H, 2.36; N, 7.04; S, 16.12. Found: C, 34.35; H, 2.41; N, 6.91; S, 16.07. Selected IR data (KBr, cm−1): 3305(m), 2047(m), 1600(s), 1540(w), 1417(m), 1217(w), 1064(w), 1011(w), 846(w), 797(w), 655(m), 628(m), 538(w). Synthesis of {[Mn(SeCN)Cl][TTF(py)4]}n (6). Light red crystals of 6 were obtained according to a procedure similar to that described for 5, with KSeCN instead of KSCN. Yield: 71%. Anal. Calcd for C27H16ClMnN5S4Se: C, 48.80; H, 2.28; N, 9.89; S, 18.11. Found: C, 49.06; H, 2.05; N, 9.68; S, 18.29. Selected IR data (KBr, cm−1): 3405(m), 2023(m), 1600(s), 1540(w), 1417(m), 1218(w), 1011(m), 846(w), 797(w), 655(m), 626(m), 538(w). Synthesis of {Cu2[TTF(py)4]2·(ClO4)2·2.5(CH2Cl2)·1.5(CH3CN)}n (7). Brown crystals of 7 were obtained according to a similar procedure described for 1 with CuClO4·4CH3CN instead of Cu(hfac)2·2H2O. Yield: 62%. Anal. Calcd for C57.50H41.50Cl7Cu2N9.50O8S8: C, 42.49; H, 2.57; N, 8.19; S, 15.78. Found: C, 42.55; H, 2.61; N, 8.25; S, 15.82. Selected IR data (KBr, cm−1): 3397(m), 1599(s), 1416(m), 1218(w), 1088(s), 825(w), 794(w), 621(m), 538(w). X-ray Crystallography. The crystal statistics of complexes 1, 3, 5, and 7 were collected with Mo Kα radiation (λ = 0.71073 Å), and those of complexes 2, 4, and 6 were obtained using Cu Kα radiation (λ = 1.54184 Å) on a CCD diffractometer. The cell parameters were retrieved and refined using computer software (SMART and SAINT, respectively).27. The SADABS28 program was applied for absorption corrections. Structures were solved by direct methods using the program package SHELXL-97.29 All the non-hydrogen atoms were located in the Fourier maps and refined with anisotropic parameters. Some contribution of the electron density in compounds of 6 and 7 from the remaining solvent molecules was removed by the SQUEEZE routine in PLATON,30 which was determined by elemental analysis. Crystal data are summarized in Table 1. Selected bond distances and angles are given in Table S1 in the Supporting Information. The crystal for 5 was seriously unstable and, thus, better crystallographic data could not be obtained.
properties, including ferromagnetism or ferrimagnetism, and spin crossover effects.23−26 Of particular interest is the investigation of the structures and physical properties of polymeric metal complexes incorporating both paramagnetic transition-metal ions and the redox-active TTF(py)4 ligand. In this paper, six new coordination polymers based on the TTF(py)4 ligand and different paramagnetic metal ions (Cu(II), Co(II) or Mn(II)), and one coordination polymer including the diamagnetic Cu(I) ion, have been successfully synthesized and structurally characterized. The experimental results indicate that the four pyridyl groups of the TTF(py)4 ligand can partially or completely coordinate with the metal ions, giving rise to a range of coordination structures. Herein, the preparation, structural analyses, and magnetic and solidstate electrochemical properties of these complexes are described.
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EXPERIMENTAL SECTION
Synthesis of {[Cu(hfac)2][TTF(py)4]·2(CH2Cl2)}n (1). A solution of Cu(hfac)2·2H2O (4.8 mg, 0.01 mmol) in CH3CN (1.5 mL) was layered onto a solution of TTF(py)4 (2.5 mg, 0.005 mmol) in CH2Cl2 (1.5 mL). The solution was left for ∼7 days at room temperature, and dark red crystals were obtained. Yield: 73% (based on TTF(py)4). Anal. Calcd for C38H22Cl4CuF12N4O4S4 (1): C, 39.34; H, 1.91; N, 4.83; S, 11.05. Found: C, 39.52; H, 1.75; N, 4.95; S, 10.91. Selected IR data (KBr, cm−1): 3405(w), 1653(m), 1609(m), 1552(m), 1498(m), 1421(w), 1258(s), 1215(s), 1137(s), 794(w), 669(w). Synthesis of {[Co(acac)2][TTF(py)4]0.5·(CHCl3)}n (2). A solution of Co(acac)2 (7.1 mg, 0.02 mmol) in CH3CN (1.5 mL) was layered onto a solution of TTF(py)4 (2.5 mg, 0.005 mmol) in CHCl3 (1.5 mL). The solution was left for ∼4 days at room temperature, and clear dark orange crystals were obtained. Yield: 57%. Anal. Calcd for C24H23Cl3CoN2O4S2: C, 45.55; H, 3.66; N, 4.43; S, 10.13. Found: C, 45.61; H, 3.75; N, 4.38, 10.03. Selected IR data (KBr, cm−1): 3406(m), 1603(s), 1511(s), 1457(m), 1401(s), 1013(w), 847(w), 796(w), 660(w), 630(w). Synthesis of {[Mn(hfac)2][TTF(py)4]0.5}n (3). Light red crystals of 3 were obtained according to a procedure similar to that described for 1 with Mn(hfac)2·2H2O instead of Cu(hfac)2·2H2O. Yield: 62%. Anal. Calcd for C23H10F12MnN2O4S2: C, 38.08; H, 1.39; N, 3.86; S, 8.84. Found: C, 38.22; H, 1.27; N, 3.83; S, 8.89. Selected IR data (KBr, cm−1): 3405(w), 1647(s), 1604(m), 1559(w), 1533(w), 1487(s), 1417(w), 1258(s), 1206(s), 1134(s), 1014(w), 803(m), 665(m), 628(w), 584(w). Synthesis of {[Cu2(OAc)4][TTF(py)4]0.5·1.5(CHCl3)·0.5(H2O)· (CH3CN)}n (4). Brown crystals of 4 were obtained according to a similar procedure described for 2 with Cu(OAc)2·2H2O instead of Co(acac)2. Yield: 68% (based on TTF(py)4). Anal. Calcd for C24H25Cl3Cu2N3O8.5S2: C, 36.53; H, 3.19; N, 5.33; S, 8.13. Found: C, 36.99; H, 3.16; N, 5.32; S, 8.19. Selected IR data (KBr, cm−1): 3396(m), 1621(s), 1423(s), 1220(w), 1015(w), 848(w), 749(w), 682(w), 624(w).
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RESULTS AND DISCUSSION Synthesis and Characterization. Based on the TTF(py)4 ligand, seven coordination polymers with paramagnetic transition-metal ions (Cu(II), Co(II), and Mn(II)), and the diamagnetic Cu(I) ion, were successfully obtained using similar reaction conditions. One reason for the differing structures obtained is that the four pyridyl groups of the TTF(py)4 ligand can partially or completely coordinate the metal ions, allowing for a variety of coordination modes and resulting structures. In addition, the diverse coordination environments of the metal C
DOI: 10.1021/acs.inorgchem.5b01803 Inorg. Chem. XXXX, XXX, XXX−XXX
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Figure 2. (a) Coordination environment of the Co(II) ion in 2 (50% probability displacement ellipsoids); (b) two-dimensional (2D) layer in 2; (c) the nonclassical hydrogen bonds between the adjacent layers; and (d) view of crystal packing in 2.
be regarded as charge-neutral. No obvious intermolecular π···π and shorter S···S interactions can be observed in the packing diagram. The TTF(py)4 ligand acts as 2-connected node to link Cu(hfac)2 units into a 1D chain (Figure 1b). Crystal Structure of 2, 3, and 4. These compounds show similar two-dimensional (2D) network structures formed by the TTF(4-py) 4 ligand with Co(acac) 2 , Mn(hfac) 2 , and Cu2(OAc)4, respectively. Among them, the TTF(py)4 ligand acts as a 4-connected node to link the M(II) units into 2D networks. For 2, the asymmetric unit consists of two Co ions, one TTF(py)4 ligand, four acac anions, and two CHCl3 molecules. As shown in Figure 2a, each Co(II) center adopts a distorted octahedral coordination geometry, which consists of four O atoms from two bidentate acac anions in the equatorial plane and two N atoms from two TTF(py)4 ligands in apical positions. The Co−O bond lengths range from 2.030 Å to 2.040 Å. The Co1−N2 and Co2−N1 bond lengths are 2.221(3) Å and 2.188(3) Å, respectively. In a similar fashion to 1, the TTF backbone shows a Z-like configuration with a dihedral angle of 9.6° folding at S1−S2. The central CC bond of the TTF core is 1.329(7) Å in length, confirming that the TTF moiety is in its neutral state. All Co(II) centers are connected to each other by the TTF(py)4 ligands to form a (4,2)-connected binodal 2D network, which consists of a rhombus grid in which the CHCl3 molecules are located (Figure 2b). The window has a dimension of 20.7 Å × 24.9 Å. These 2D nets are planar, and stack together to give a threedimensional (3D) framework through nonclassical hydrogen bonds C(2)−H(2)···O(4) (H···O distance, 2.51 Å) and C(17)−H(17A)···O(1) (H···O distance, 2.53 Å) (Figure 2c). Viewing the structure along the crystallographic a axis, rhombus-like channels are observed (Figure 2d). To investigate the effect of the identity of the metal ions on the formation of the coordination polymers, compound 3 was
ions, solvent systems, and anions can also result in distinct structures, as reported in related literature.31−33 Materials 1−7 were obtained as polymeric metal compounds in mixed-solvent systems using combinations of the TTF(py)4 ligand and different inorganic metal salts. It is important to note that the products are not dependent on the ligand-to-metal ratio in these specific reactions; however, an increase in the metal-to-ligand ratio resulted in somewhat higher yields and higher-quality crystals. To ensure that the bulk materials were truly representative of the crystal structures, powder X-ray diffraction (PXRD) experiments for 1−3 and 5−7 were carried out at room temperature (see Figure S6 in the Supporting Information). The framework of compound 4 is quickly collapsed in the air, and no ideal XRD spectrum was obtained. Thermogravimetric analysis experiments (see Figure S4 in the Supporting Information) were also conducted to determine the thermal stability of these compounds (1, 4, and 7). However, the crystals of 1, 4, and 7 are unstable and lose solvent molecules quickly in air, so the TGA data cannot be used to calculate the exact solvent molecules. Crystal Structure of 1. The asymmetric unit of complex 1 contains one Cu(II) atom, two hfac anions, a TTF(py)4 ligand, and two free CH2Cl2 molecules. As shown in Figure 1a, the central Cu(II) ion lies on the inversion center and adopts a distorted octahedral coordination environment, which is defined by four oxygen donors from two hfac anions in the equatorial plane and two pyridyl nitrogen donors from two ligands. The Cu−O bonds range from 2.078(4) Å to 2.155(4) Å. The pyridyl nitrogen atoms of the ligand occupy the axial positions with the shortest Cu1−N2 bond length of 2.013(4) Å. The TTF backbone exhibits a Z-like configuration with a dihedral angle of 9.4° folding at S1−S2. The central CC bond length of the TTF core is 1.334(10) Å. The bond lengths and angles of TTF(py)4 are similar to those reported for the neutral unit,34 indicating that the TTF(py)4 ligand can be still D
DOI: 10.1021/acs.inorgchem.5b01803 Inorg. Chem. XXXX, XXX, XXX−XXX
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Figure 3. (a) Coordination environment of the Mn(II) ion in 3 (50% probability displacement ellipsoids); (b) 2D layer in 3.
Figure 4. (a) Coordination environment for Cu(II) ion in 4 (50% ellipsoids); (b) view of crystal packing of 4 (down the crystallographic a-axis) showing CHCl3 and CH3CN molecules in the channels.
node to link four metal ions, whereas the OAc anions adopt a 2connected bridging mode connecting two metal ions. In this way, each TTF(py)4 ligand is bound to four [Cu2(OAc)4] units to yield a 2D network with dinuclear Cu cores separated by 2.600(11) Å, which is comparable to those found in the related complex, [(DMT-TTF−py)2Cu2(OAc)2]·4C6H6 (2.620 Å).35 In a fashion similar to that for compounds 2 and 3, the 2D sheet consists of a rhombus ring (Figure S2 in the Supporting Information), whose dimensions are 20.7 Å × 31.3 Å, which are larger than those of 2 and 3. The difference in the dimensions is predominantly due to the Cu2(OAc)4 moiety. Through nonclassical hydrogen bonds (C(4)−H(4)···S(2), H···S distance, 2.87 Å), these 2D nets are further connected to yield the 3D framework (Figure S2). Viewing from the a-axis, rhombus channels are found, in which CHCl3, H2O, and CH3CN molecules are located (see Figure 4b). Crystal Structures of 5 and 6. In complex 5, there is only one Mn(II) center in the asymmetric unit, and the Mn atom lies in a distorted octahedral coordination sphere, formed by four N atoms from four TTF(py)4 ligands in the equatorial plane and two N atoms from two SCN− anions in the axial positions (Figure 5a). Compared to 3, the Mn(II)−Npyridyl bond length (2.304 Å) is significantly elongated. The neutral TTF units are almost coplanar with a dihedral angle of 0.9° folding at S1−S2. The central CC bond length of the TTF units is 1.350(3) Å, which is similar to that found in 3 and 4. As indicated in Figure 5b, the TTF(py)4 ligand links the inorganic Mn(SCN)2 units into a (4,4)-connected binodal 2D network,
prepared using the same reaction conditions as those employed for 1, but using Mn(hfac)2·2H2O instead of Cu(hfac)2·2H2O. In a fashion similar to that used for the Cu(II) center in 1, the Mn(II) ions also adopt a distorted octahedral coordination sphere (Figure 3a). The TTF backbone shows a Z-like configuration with a dihedral angle of 5.2° folding at S1−S2, which is smaller than those in 1 and 2. The central CC bond length of the TTF core is 1.357(4) Å, which is comparable to those found in 1 and 2. However, for complex 3, the TTF(py)4 ligand acts as a tetradentate ligand for the Mn(II) ions and leads to the formation of a 2D network instead of the 1D chain structure of 1 (Figure 3b). The windows have a similar dimension to that in 2 (20.0 Å × 26.1 Å). These 2D nets are also planar, and they are stacked exactly together to give a 3D framework through nonclassical hydrogen bonds C(7)−H(7)··· O(2) (H···O distance, 2.38 Å). Viewing from the a-axis, rhombus-like channels are also found; however, there are no guest solvent molecules in the channels (see Figure S1 in the Supporting Information). For compound 4, as shown in Figure 4a, the two Cu centers adopt a distorted square-based pyramidal coordination environment formed by four carboxyl oxygen atoms from four different carboxylate groups in the basal planes and one N atom from the TTF(py)4 ligand in apical positions. The structure of neutral TTF also shows a Z-like conformation. The dihedral angle folding at S1−S2 is 3.6°, smaller than those of 1−3. The central CC bond length of the TTF unit is 1.348(8) Å, which is closed to that 3. The TTF(py)4 ligands act as a 4-connected E
DOI: 10.1021/acs.inorgchem.5b01803 Inorg. Chem. XXXX, XXX, XXX−XXX
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Figure 5. (a) Coordination environment for Mn(II) ion in 5 (30% probability displacement ellipsoids); (b) 2D layer in 5; and (c) view of crystal packing in 5. CH2Cl2 molecules (shown as space-filling) between the layers.
Figure 6. (a) Coordination environment for Mn(II) ion in 6 (50% probability displacement ellipsoids); (b) view of crystal packing in 6.
which are parallel to the crystallographic ab plane and consist of two different individual rings. The larger one is a 30-membered elliptical macrocycle whose approximate (crystallographic) dimensions are 16.51 Å × 9.72 Å. The smaller one is a 22membered dimeric unit with dimensions of 10.16 Å × 9.73 Å. These 2D nets are planar and stack together along the crystallographic c-axis in an −ABAB− stacking sequence (see Figure 5c). The CH2Cl2 molecules are located between the interlayer spaces. Viewing the structure along the crystallographic c-axis, rhombus channels are found and the dimensions are much smaller than that found in 2, 3, and 4, because of the different stacking sequence. Compared to 3, the difference in the structure and stacking mode indicates the remarkable influence that the different anion and solvent system imparts to the structure. The use of KSeCN for the preparation of complex 6, instead of KSCN in 5, allowed an investigation into the effect of the anion on the coordination polymer. Compared to 5, only one Cl− anion is substituted by SeCN− in 6. The central CC
bond length of the TTF core is 1.383(14) Å, which is longer than those found in 1−5. The coordination interaction between the TTF(py)4 ligand and the Mn(II) ions leads to a 2D network, which is similar to that of 5 (see Figure 6a). The TTF moiety adopts a U-like configuration with a dihedral angle of 22.8° folding at S1−S2, and a dihedral angle of 15.7° folding at S3−S4. Thus, this 2D net is undulating and stacks together along the crystallographic b-axis in an −ABAB− stacking sequence (Figure 6b). However, no significant intermolecular π···π and S···S contacts (
