research communications
catena-poly[[bis(1-benzyl-1H-imidazole-κN3)cadmium(II)]-di-μ-azido-κ4N1:N3]
and properties ofaDepartment of Chemistry, Faculty of Science and Technology, Thammasat University, Klong Luang, Pathum Thani 12121, Thailand, bDepartment of Chemistry, Faculty of Science, Naresuan University, Phitsanulok 65000, Thailand, and cMaterials and Textile Technology, Faculty of Science and Technology, Thammasat University, Klong Luang, Pathum Thani 12121, Thailand
*Correspondence e-mail: nwan0110@tu.ac.th
The new title one-dimensional CdII coordination polymer, [Cd(C10H10N2)2(μ1,3-N3)2]n, has been synthesized and structurally characterized by single-crystal X-ray diffraction. The consists of a CdII ion, one azide and one 1-benzylimidazole (bzi) ligand. The CdII ion is located on an inversion centre and is surrounded in a distorted octahedral coordination sphere by six N atoms from four symmetry-related azide ligands and two symmetry-related bzi ligands. The CdII ions are linked by double azide bridging ligands within a μ1,3-N3 end-to-end (EE) coordination mode, leading to a one-dimensional linear structure extending parallel to [100]. The supramolecular framework is stabilized by the presence of weak C—H⋯N interactions, π–π stacking [centroid-to-centroid distance of 3.832 (2) Å] and C—H⋯π interactions between neighbouring chains.
1. Chemical context
Coordination polymers (CPs) have been receiving significant attention because of their interesting topologies (Zhang et al., 2013), properties (Kitagawa et al., 2004) and potential applications (He et al., 2018; Gao et al., 2019). Among various transition metal CPs, cadmium(II) coordination polymers containing nitrogen-donor ligands have been widely investigated because of their potential applications in (PL) (Wang et al., 2012) or (Wu et al., 2017). Generally, the CdII ion adopts the stable [Kr]4d10 and its crystal chemistry is dominated by coordination numbers of four to six (Liu et al., 2016). As for the choice of nitrogen-donor ligands, pseudohalides in the form of azide (N3−), thiocyanate (NCS−) or dicyanamide (N(CN)2−) are good candidates as anionic linkers (Mautner et al., 2019). In particular, the azide ligand is an attractive bridging ligand due to the variability of its coordination modes, such as the common μ1,1 (end-on, EO) and μ1,3 (end-to-end, EE) mode with single or double azide bridges (Ribas et al., 1999). Therefore, such ligands are used for studying magnetochemistry and for the construction of coordination frameworks. Imidazole-based derivatives with aromatic substituents, for example, 1-benzylimidazole (bzi) (Krinchampa et al., 2016) or 1,4-bis(imidazol-1-ylmethyl)benzene (bix) (Adarsh et al., 2016), are usually selected for extending the structural dimensions and increasing the properties of their CPs due to the existence of supramolecular interactions in terms of hydrogen bonds, π–π stacking and/or C—H⋯π to increase the rigidity and framework stabilities. To the best of our knowledge, the number of CdII coordination polymers with mixed nitrogen-donor ligands, e.g. azide and bzi ligands, is still limited. As part of our ongoing exploration of new members of d10 CPs and investigation of their properties (Krinchampa et al., 2016; Sangsawang et al., 2017), a family of CdII coordination polymers containing mixed nitrogen-donor ligands, i.e. bzi and pseudohalide ligands, such as azide (N3−), thiocyanate (NCS−) and dicyanamide (N(CN)2−), have been designed and prepared. In this work, a new one-dimensional CdII coordination polymer, [Cd(bzi)2(μ1,3-N3)2]n, was synthesized and characterized. Details of the synthesis, determination and properties of this compound are reported herein.
2. Structural commentary
The II ion (site symmetry ), one azide ligand and one bzi ligand (Fig. 1). The distorted octahedral coordination environment of the CdII ion is defined by six N atoms. Two are from two symmetry-related bzi ligands in the axial positions with the shortest Cd—N distance, and four are from four symmetry-related azide ligands in equatorial positions with slightly larger distances; angular distortions are small (Table 1). Neighbouring CdII ions are linked by doubly end-to-end (EE) binding azide bridges, resulting in a one-dimensional linear chain-like structure extending along [100] (Fig. 2). The Cd⋯Cd distance in the chain is 5.5447 (3) Å, which is longer than in a previously reported one-dimensional zigzag chain-like structure of a CdII coordination polymer, [Cd(N3)2(3,5-DMP)2] (Goher et al., 2003).
of the title compound consists of a Cd3. Supramolecular features
The π–π stacking and intermolecular C—H⋯π interactions between adjacent chains (Fig. 3a). Hydrogen-bonding interactions are found between the C—H groups of the phenyl rings and the N atoms of the azide bridging ligands (Table 2 and Fig. 3b); π–π stacking between adjacent chains is associated with the symmetry-related imidazole rings of the bzi ligands [Cg1⋯Cg1(−x + 1, −y + 1, −z + 1) = 3.832 (2) Å; slippage = 1.477 Å; interplanar distance = 3.536 (3) Å; Cg1 is the centroid of the imidazole N1/C1/N2/C2/C3 ring], as shown in Fig. 3(b). Moreover, C—H⋯π interactions between the phenyl rings of the bzi ligands of different chains are observed (Fig. 3c and Table 2).
of the title compound is stabilized by various weak interactions, including C—H⋯N hydrogen bonding,4. Characterization
The FT–IR spectrum (Fig. S1 in the supporting information) of the title compound presents the characteristic bands of the N3− ligand at 2058 cm−1 and the characteristic bands of the bzi ligand including C—H aromatic stretching at 3113–3028 cm−1, C=N and C=C stretching at 1602–1506 cm−1, C—C stretching at 1396 cm−1 and C—N stretching at 1233 cm−1. The IR spectrum also reveals a band at 3365 cm−1, indicating the N⋯H hydrogen-bonding interaction in this compound.
Plots of the experimental and simulated powder X-ray diffraction (PXRD) patterns of the title compound are shown in Fig. S2 of the supporting information, revealing a good match and thus phase purity and repeatable synthesis.
The thermal stability of the title compound has been investigated by means of thermogravimetric analysis from room temperature to 1073 K under a nitrogen atmosphere. Based on the results (Fig. S3 in the supporting information), the structure of the title compound is stable up to around 470 K. Above this temperature, the structure starts to collapse by losing a mass percentage of 57.7%, which corresponds to the loss of two bzi ligands. The second step of mass loss by about 30.6% corresponds to the loss of the remaining azide ligands. Further increasing the temperature leads only to a slight increase of the mass loss until CdO was formed as the final product.
5. (PL) properties
Fig. 4 presents the solid-state PL emission spectra of the free bzi ligand and the title compound. It should be noted that the signal in the emission spectra below 330 nm belongs to the tail of the scattered excitation light. The PL spectrum of the free bzi ligand reveals a broad band with the centre at 384 nm (λex = 305 nm), which is assigned to the π→π* and n→π* transitions of the delocalized electrons within the aromatic phenyl and imidazole rings. Interestingly, the of the title compound exhibits a with a λmax of 429 nm (λex = 305 nm) and a higher emission intensity in comparison with that of free bzi. Furthermore, the emission peak of the title compound is less broad than that of the bzi ligand. The PL features of the title compound can be attributed to ligand-to-metal charge transfer (LMCT). The increased intensity is presumably caused by the increased rigidity for the bzi ligands due to the presence of numerous weak supramolecular interactions between the chains in the This increased rigidity likely enhances the emission properties of the title compound due to limiting the probability of nonradiative decay of the excited state.
6. Database survey
One-dimensional linear chain-like CdII coordination polymers constructed by one type of doubly end-to-end (EE) bound azide bridges and ligands based on imidazole derivatives are rare in the literature. To the best of our knowledge, there are only a few first-row transition metal coordination polymers constructed by μ1,3-N3− and differently substituted pyridine derivatives: [Cu(N3)2(L1)2]n [Cambridge Structural Database (CSD; Groom et al., 2016) refcode LOYROG; Dalai et al., 2002], [Co(N3)2(bepy)2]n (TUJCEI; Zhao et al., 2015) and [Mn(N3)2(L2)2]n (CEMTOG; Khani et al., 2018) {where L1 = 4-(dimethylamino)pyridine, bepy = 4-benzylpyridine and L2 = N′-[4-(dimethylamino)benzylidene]isonicotinohydrazide}. On the other hand, previously reported CPs containing μ1,3-N3− and 3,5-dimethylpyridine (3,5-DMP) ligands in [M(N3)2(3,5-DMP)2] [M = Cd (EHEYIZ; Goher et al., 2003) and Ni (LEWMAD; Lu et al., 2012)] exhibit one-dimensional structures with zigzag chains.
7. Synthesis and crystallization
A methanolic solution (5 ml) of bzi (1.0 mmol) was introduced slowly to a methanolic solution (5 ml) of Cd(NO3)2·4H2O (1.0 mmol). A DMSO solution (5 ml) of NaN3 (2.0 mmol) was then added slowly to the mixed solution, resulting in the immediate formation of a white precipitate. The precipitate was dropped slowly into a DMSO–DMF (1:2 v/v) mixture (9 ml) under continuous stirring at 333 K over a period of 30 min, and was kept stirring until the solution became clear. Finally, the solution was filtered and allowed to slowly evaporate in air at room temperature. Colourless crystals of the title compound were obtained within 3 d (yield 23.36%, 119.80 mg, based on the CdII salt). Elemental analysis calculated (found) (%) for C20H20CdN10: C 46.84 (46.83), H 3.9 3(3.62), N 27.31 (27.05). IR (KBr, cm−1): 3370 (m), 3109 (s), 2062 (s, broad), 1612 (w), 1510 (m), 1440 (m), 1395 (w), 1355 (m), 1280 (m), 1233 (m), 1098 (s), 1030 (m), 942 (m), 822 (m), 767 (m), 712 (s), 652 (m, 625 (m), 462 (w).
8. Refinement
The crystal data, data collection and structure . All H atoms were generated geometrically and refined using a riding model, with C—H = 0.93 Å and Uiso(H) = 1.2Ueq(C).
details are summarized in Table 3Supporting information
https://doi.org/10.1107/S205698901901421X/wm5527sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S205698901901421X/wm5527Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S205698901901421X/wm5527sup3.pdf
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: SHELXL2017 (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).[Cd(C10H10N2)2(N3)2] | F(000) = 516 |
Mr = 512.86 | Dx = 1.588 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
a = 5.5447 (3) Å | Cell parameters from 9996 reflections |
b = 8.4301 (4) Å | θ = 3.0–32.3° |
c = 22.9517 (11) Å | µ = 1.05 mm−1 |
β = 90.351 (2)° | T = 296 K |
V = 1072.80 (9) Å3 | Block, colourless |
Z = 2 | 0.32 × 0.3 × 0.22 mm |
Bruker D8 QUEST CMOS PHOTON II diffractometer | 3817 independent reflections |
Radiation source: sealed x-ray tube, Mo | 2858 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.072 |
Detector resolution: 7.39 pixels mm-1 | θmax = 32.3°, θmin = 3.0° |
ω and φ scans | h = −8→8 |
Absorption correction: multi-scan (SADABS; Krause et al., 2015) | k = −12→12 |
Tmin = 0.712, Tmax = 0.746 | l = −34→34 |
42354 measured reflections |
Refinement on F2 | Hydrogen site location: inferred from neighbouring sites |
Least-squares matrix: full | H-atom parameters constrained |
R[F2 > 2σ(F2)] = 0.043 | w = 1/[σ2(Fo2) + (0.0237P)2 + 0.7897P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.080 | (Δ/σ)max < 0.001 |
S = 1.12 | Δρmax = 0.49 e Å−3 |
3817 reflections | Δρmin = −0.43 e Å−3 |
143 parameters | Extinction correction: SHELXL2017 (Sheldrick, 2015b), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.0043 (7) |
Primary atom site location: dual |
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 | ||
Cd1 | 0.500000 | 1.000000 | 0.500000 | 0.03071 (9) | |
N1 | 0.5662 (4) | 0.7657 (2) | 0.45279 (9) | 0.0364 (4) | |
N2 | 0.4732 (4) | 0.5441 (2) | 0.40781 (9) | 0.0361 (5) | |
N3 | 0.1837 (4) | 1.0467 (3) | 0.43386 (10) | 0.0495 (6) | |
N4 | −0.0153 (4) | 1.0885 (2) | 0.43738 (8) | 0.0293 (4) | |
N5 | −0.2152 (4) | 1.1320 (3) | 0.43834 (10) | 0.0442 (5) | |
C1 | 0.4075 (5) | 0.6938 (3) | 0.41923 (11) | 0.0391 (5) | |
H1 | 0.267175 | 0.740956 | 0.405159 | 0.047* | |
C2 | 0.7433 (5) | 0.6557 (3) | 0.46316 (11) | 0.0417 (6) | |
H2 | 0.880614 | 0.672494 | 0.485806 | 0.050* | |
C3 | 0.6881 (5) | 0.5197 (3) | 0.43559 (12) | 0.0451 (6) | |
H3 | 0.778880 | 0.426908 | 0.435479 | 0.054* | |
C4 | 0.3379 (5) | 0.4268 (4) | 0.37310 (12) | 0.0481 (7) | |
H4A | 0.168657 | 0.455917 | 0.372746 | 0.058* | |
H4B | 0.351963 | 0.323822 | 0.391634 | 0.058* | |
C5 | 0.4247 (5) | 0.4141 (3) | 0.31116 (10) | 0.0366 (5) | |
C6 | 0.3045 (6) | 0.4900 (4) | 0.26668 (14) | 0.0563 (7) | |
H6 | 0.168444 | 0.550339 | 0.274880 | 0.068* | |
C7 | 0.3837 (8) | 0.4777 (4) | 0.20985 (14) | 0.0694 (10) | |
H7 | 0.300687 | 0.529653 | 0.180124 | 0.083* | |
C8 | 0.5824 (7) | 0.3901 (4) | 0.19727 (13) | 0.0618 (9) | |
H8 | 0.637397 | 0.383724 | 0.159140 | 0.074* | |
C9 | 0.7007 (6) | 0.3116 (4) | 0.24067 (14) | 0.0605 (8) | |
H9 | 0.835053 | 0.250246 | 0.231895 | 0.073* | |
C10 | 0.6230 (6) | 0.3221 (4) | 0.29772 (12) | 0.0503 (7) | |
H10 | 0.704249 | 0.267304 | 0.327012 | 0.060* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cd1 | 0.02939 (12) | 0.03079 (13) | 0.03194 (13) | 0.00640 (11) | −0.00134 (8) | −0.00695 (11) |
N1 | 0.0393 (11) | 0.0338 (11) | 0.0359 (10) | 0.0070 (9) | −0.0021 (8) | −0.0085 (9) |
N2 | 0.0453 (12) | 0.0304 (10) | 0.0328 (10) | −0.0014 (8) | 0.0040 (9) | −0.0062 (8) |
N3 | 0.0389 (12) | 0.0709 (16) | 0.0385 (11) | 0.0148 (11) | −0.0086 (9) | −0.0046 (11) |
N4 | 0.0399 (11) | 0.0245 (9) | 0.0236 (9) | 0.0024 (8) | −0.0025 (8) | 0.0007 (7) |
N5 | 0.0389 (12) | 0.0437 (13) | 0.0501 (13) | 0.0104 (10) | 0.0068 (10) | 0.0092 (10) |
C1 | 0.0395 (13) | 0.0402 (14) | 0.0376 (13) | 0.0078 (11) | −0.0021 (10) | −0.0057 (11) |
C2 | 0.0405 (14) | 0.0421 (14) | 0.0425 (14) | 0.0103 (11) | −0.0040 (11) | −0.0093 (11) |
C3 | 0.0550 (15) | 0.0334 (15) | 0.0469 (14) | 0.0140 (12) | −0.0008 (12) | −0.0056 (11) |
C4 | 0.0564 (17) | 0.0459 (16) | 0.0420 (14) | −0.0187 (13) | 0.0112 (13) | −0.0122 (12) |
C5 | 0.0431 (13) | 0.0329 (13) | 0.0337 (12) | −0.0083 (10) | 0.0004 (10) | −0.0065 (10) |
C6 | 0.0616 (18) | 0.0559 (18) | 0.0513 (16) | 0.0155 (16) | −0.0086 (13) | −0.0052 (15) |
C7 | 0.101 (3) | 0.064 (2) | 0.0436 (16) | 0.009 (2) | −0.0145 (17) | 0.0064 (15) |
C8 | 0.085 (2) | 0.066 (2) | 0.0339 (14) | −0.0078 (19) | 0.0064 (15) | −0.0049 (14) |
C9 | 0.0557 (19) | 0.072 (2) | 0.0537 (18) | 0.0121 (16) | 0.0060 (14) | −0.0170 (16) |
C10 | 0.0584 (18) | 0.0533 (17) | 0.0393 (14) | 0.0120 (14) | −0.0068 (12) | −0.0048 (13) |
Cd1—N1 | 2.2834 (19) | C3—H3 | 0.9300 |
Cd1—N1i | 2.2834 (19) | C4—H4A | 0.9700 |
Cd1—N3 | 2.346 (2) | C4—H4B | 0.9700 |
Cd1—N3i | 2.346 (2) | C4—C5 | 1.507 (3) |
Cd1—N5ii | 2.400 (2) | C5—C6 | 1.374 (4) |
Cd1—N5iii | 2.400 (2) | C5—C10 | 1.382 (4) |
N1—C1 | 1.314 (3) | C6—H6 | 0.9300 |
N1—C2 | 1.371 (3) | C6—C7 | 1.383 (5) |
N2—C1 | 1.340 (3) | C7—H7 | 0.9300 |
N2—C3 | 1.364 (4) | C7—C8 | 1.359 (5) |
N2—C4 | 1.472 (3) | C8—H8 | 0.9300 |
N3—N4 | 1.161 (3) | C8—C9 | 1.361 (5) |
N4—N5 | 1.168 (3) | C9—H9 | 0.9300 |
C1—H1 | 0.9300 | C9—C10 | 1.384 (4) |
C2—H2 | 0.9300 | C10—H10 | 0.9300 |
C2—C3 | 1.344 (4) | ||
N1—Cd1—N1i | 180.0 | C3—C2—H2 | 125.2 |
N1i—Cd1—N3i | 87.70 (8) | N2—C3—H3 | 126.7 |
N1i—Cd1—N3 | 92.30 (8) | C2—C3—N2 | 106.7 (2) |
N1—Cd1—N3i | 92.30 (8) | C2—C3—H3 | 126.7 |
N1—Cd1—N3 | 87.70 (8) | N2—C4—H4A | 108.9 |
N1i—Cd1—N5ii | 90.73 (8) | N2—C4—H4B | 108.9 |
N1i—Cd1—N5iii | 89.27 (8) | N2—C4—C5 | 113.2 (2) |
N1—Cd1—N5iii | 90.74 (8) | H4A—C4—H4B | 107.8 |
N1—Cd1—N5ii | 89.26 (8) | C5—C4—H4A | 108.9 |
N3i—Cd1—N3 | 180.0 | C5—C4—H4B | 108.9 |
N3—Cd1—N5iii | 91.87 (9) | C6—C5—C4 | 120.8 (3) |
N3i—Cd1—N5iii | 88.13 (9) | C6—C5—C10 | 118.6 (3) |
N3—Cd1—N5ii | 88.13 (9) | C10—C5—C4 | 120.6 (3) |
N3i—Cd1—N5ii | 91.87 (9) | C5—C6—H6 | 119.6 |
N5ii—Cd1—N5iii | 180.0 | C5—C6—C7 | 120.7 (3) |
C1—N1—Cd1 | 124.62 (16) | C7—C6—H6 | 119.6 |
C1—N1—C2 | 105.4 (2) | C6—C7—H7 | 119.9 |
C2—N1—Cd1 | 128.34 (17) | C8—C7—C6 | 120.2 (3) |
C1—N2—C3 | 106.8 (2) | C8—C7—H7 | 119.9 |
C1—N2—C4 | 126.9 (2) | C7—C8—H8 | 120.1 |
C3—N2—C4 | 126.3 (2) | C7—C8—C9 | 119.8 (3) |
N4—N3—Cd1 | 135.45 (18) | C9—C8—H8 | 120.1 |
N3—N4—N5 | 177.0 (2) | C8—C9—H9 | 119.7 |
N4—N5—Cd1iv | 119.56 (17) | C8—C9—C10 | 120.7 (3) |
N1—C1—N2 | 111.6 (2) | C10—C9—H9 | 119.7 |
N1—C1—H1 | 124.2 | C5—C10—C9 | 120.0 (3) |
N2—C1—H1 | 124.2 | C5—C10—H10 | 120.0 |
N1—C2—H2 | 125.2 | C9—C10—H10 | 120.0 |
C3—C2—N1 | 109.6 (2) | ||
Cd1—N1—C1—N2 | −166.25 (16) | C4—N2—C1—N1 | 178.4 (2) |
Cd1—N1—C2—C3 | 165.85 (18) | C4—N2—C3—C2 | −178.3 (2) |
N1—C2—C3—N2 | −0.3 (3) | C4—C5—C6—C7 | −179.7 (3) |
N2—C4—C5—C6 | −99.6 (3) | C4—C5—C10—C9 | −180.0 (3) |
N2—C4—C5—C10 | 82.3 (3) | C5—C6—C7—C8 | 0.0 (5) |
C1—N1—C2—C3 | 0.1 (3) | C6—C5—C10—C9 | 1.8 (4) |
C1—N2—C3—C2 | 0.4 (3) | C6—C7—C8—C9 | 1.3 (6) |
C1—N2—C4—C5 | 98.1 (3) | C7—C8—C9—C10 | −1.0 (5) |
C2—N1—C1—N2 | 0.2 (3) | C8—C9—C10—C5 | −0.5 (5) |
C3—N2—C1—N1 | −0.4 (3) | C10—C5—C6—C7 | −1.5 (5) |
C3—N2—C4—C5 | −83.3 (4) |
Symmetry codes: (i) −x+1, −y+2, −z+1; (ii) −x, −y+2, −z+1; (iii) x+1, y, z; (iv) x−1, y, z. |
D—H···A | D—H | H···A | D···A | D—H···A |
C3—H3···N5v | 0.93 | 2.49 (1) | 3.313 (4) | 148 (1) |
C7—H7···N3vi | 0.93 | 2.62 (1) | 3.368 (4) | 138 (1) |
C6—H6···Cg2vii | 0.93 | 3.17 (1) | 3.890 (3) | 135 (1) |
C9—H9···Cg2viii | 0.93 | 3.10 (1) | 3.833 (3) | 138 (1) |
Symmetry codes: (v) x+1, y−1, z; (vi) −x+1/2, y−1/2, −z+1/2; (vii) −x+1/2, y+1/2, −z+1/2; (viii) −x+3/2, y−1/2, −z+1/2. |
Acknowledgements
The authors thank the Department of Chemistry, Faculty of Science and Technology, Thammasat University, for financial support and the Central Scientific Instrument Center (CSIC), Faculty of Science and Technology, Thammasat University, for funds to purchase the X-ray diffractometer. The authors also thank the Science Lab Center, Faculty of Science, Naresuan University, for the use of the spectrofluorometer.
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