research communications
catena-poly[[[(2-ethoxypyrazine-κN)copper(I)]-di-μ2-cyanido] [copper(I)-μ2-cyanido]]
ofaDepartment of Chemistry, Taras Shevchenko National University of Kyiv, Volodymyrska St. 64, Kyiv 01601, Ukraine
*Correspondence e-mail: sofiia.partsevska@univ.kiev.ua
In the 4H3OC2H5N2)][Cu(CN)]}n, there are two Cu atoms with different coordination environments. One CuI ion is coordinated in a triangular coordination geometry by the N atom of the 2-ethoxypyrazine molecule and by two bridging cyanide ligands, equally disordered over two sites exchanging C and N atoms, thus forming polymeric chains parallel to the c axis. The other Cu atom is connected to two bridging cyanide groups disordered over two sites with an occupancy of 0.5 for each C and N atom, and forming an almost linear polymeric chain parallel to the b axis. In the crystal, the two types of chain, which are orthogonal to each other, are connected by cuprophilic Cu⋯Cu interactions [2.7958 (13) Å], forming two-dimensional metal–organic coordination layers parallel to the bc plane. The coordination framework is further stabilized by weak long-range (electrostatic type) C—H⋯π interactions between cyano groups and 2-ethoxypyrazine rings.
of the title coordination compound, {[Cu(CN)(CKeywords: crystal structure; ethoxypyrazine; cyanides; copper(I); metal–organic framework.
1. Chemical context
The design and synthesis of coordination polymers has received much attention in the field of inorganic chemistry due to their structural features, as well as their potential applications in catalysis, adsorption, luminescence and as chemical sensors (Li et al., 2012; Czaja et al., 2009; Etaiw et al., 2016; Ley et al., 2010). Complexes with the cyano group, which is one of the important bridging and assembling ligands acting as a monodentate, bidentate or tridentate ligand, are the subject of much interest (Ley et al., 2010). Different types of metal with building blocks from linear M(CN)2 (Okabayashi et al., 2009), trigonal M(CN)3 (Su et al., 2011), tetrahedral M(CN)4 (Jószai et al., 2005) to high connected M(CN)7 (Qian et al., 2013) and M(CN)8 (Chorazy et al., 2013) units have been reported with various metal ions. Among the large number of various metal copper(I) cyanide complexes are very important in organic, organometallic and supramolecular chemistry because of both the copper centre, which possesses several coordination modes (two-, three-, four-, five- or six-coordinate) and can form diverse geometries, and the versatile cyanide ligand (Pike, 2012). In general, the crystallochemistry of CuICN systems is highly complex and provides several recurrent structural motifs: (i) linear chains similar to those of pure CuCN with possible disorder in the cyanide groups; (ii) six CN ligands connected by copper dimers with stoichiometry Cu2(1,1,2-μ3-CN)2(CN)4 and Cu⋯Cu distances typical of cuprophilic interactions; (iii) (CuCN)x rings with square, pentagonal or hexagonal geometry (Grifasi et al., 2016; Pike, 2012). Mixed-valence CuI/CuII coordination complexes with cyanide and amine ligands having different supramolecular architectures and their luminescence properties have also been reported (Grifasi et al., 2016). To improve the design of copper cyanide coordination polymers, as well as to investigate its influence on the resulting luminescence and other properties, different types of co-ligands were used, in particular, N-donor bridging or chelating ligands, such as 1,10-phenanthroline, 4,4′-bipyridine (Su et al., 2011), pyridines with methyl, ethyl, methoxy and other substituents (Dembo et al., 2010), and pyrazine (Qin et al., 2012; Chesnut et al., 2001) and its derivatives (Chesnut et al., 2001). Here we describe the of a new [CuCN]-based metal–organic coordination framework of the general formula {[Cu(CN)2(EtOpz)][CuCN]}n (where EtOpz is 2-ethoxypyrazine).
2. Structural commentary
Fig. 1 shows a fragment of the title compound, which is a polymeric copper complex with different coordination environments of the two crystallographically independent CuI ions. The Cu1 atom is coordinated to the N atom of a 2-ethoxypyrazine molecule [Cu1—N5 = 2.090 (4) Å]. Two other coordination positions are occupied by bridging cyanide groups, which are equally disordered over two sites, exchanging C and N atoms [Cu1—C1/N1 = 1.905 (4) Å and Cu1—C2/N2 = 1.888 (4) Å], thus forming an irregular triangular coordination geometry where the copper ion is displaced from the centre [C2/N2—Cu1—N5 = 108.9 (2)°, C1/N1—Cu1—N5 = 103.2 (2)° and C2/N2—Cu1—C1/N1 = 147.7 (2)°]. The Cu2 atom is coordinated by two cyanide ligands, which are also disordered over two sites with an occupancy of 0.5 for each C and N atom [Cu2—C3/N3 = 1.859 (5) Å and Cu2—C4/N4iii = 1.841 (4) Å; symmetry codes: (i) −x + 1, y, −z + ; (ii) −x + 1, −y, −z + 1; (iii) x, y − 1, z] to form an almost linear chain [C4/N4iii—Cu2—C3/N3 = 170.5 (2)°]. The two CuI centres are connected through a Cu⋯Cu interaction [Cu1—Cu2 = 2.7958 (13) Å] that could be interpreted as a cuprophilic contact (Hermann et al., 2001).
3. Supramolecular features
The crystal packing of the title compound (Fig. 2) consists of two types of orthogonal polymeric chains (the first involving the Cu1 atoms and parallel to the c axis and the second involving the Cu2 atoms and parallel to the b axis) interconnected by Cu⋯Cu contacts and forming two-dimensional layers parallel to (100). The Cu⋯Cu contacts are almost perpendicular to the [Cu2(CN)] chains [C3/N3—Cu2—Cu1 = 89.8 (2)° and C4/N4iii—Cu2—Cu1 = 99.7 (2)°]. At the same time, the Cu2 atom occupies an axial position with respect to the triangular [N(CN)2] coordination environment of Cu1 [C1/N1—Cu1—Cu2 = 70.6 (2)° and C2/N2—Cu1—Cu2 = 87.6 (2)°]. The resulting metal–organic coordination framework is additionally stabilized by weak long-range (electrostatic-type) C—H⋯π interactions between cyanide groups and 2-ethoxypyrazine rings (Aliev et al., 2015; Table 1). Short Cu2⋯O1iv contacts of 3.060 (3) Å are also observed [symmetry code: (iv) −x + 1, −y + 1, −z + 1].
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4. Database survey
A search of the Cambridge Structural Database (CSD, Version 5.39, last update November 2017; Groom et al., 2016) confirmed that the structure of the title complex has not been reported previously and revealed for the fragment –C≡N—Cu—C≡N– and an azine ligand attached to Cu (unsubstituted, substituted and fused azines) 128 structures, which are polymeric copper cyanide chains decorated with various co-ligands. Most of these co-ligands are derivatives of pyridine, piperidine, methylenetetramine and piperazine. In particular, the structure of catena-[pentakis(μ2-cyano)tris(1-phenylpiperazine)pentacopper] (refcode VIYPOK; Pike et al., 2014) contains five independent Cu atoms and five nonsymmetrically disordered and forms two independent one-dimensional chain sublattices, i.e. (CuCN)(PhPip) and (CuCN)3(PhPip), associated by Cu⋯Cu pairwise cuprophilic interactions, with distances of 2.5586 (10) and 2.6441 (10) Å. A search of the CSD for two C—N—Cu—C—N fragments with a defined Cu⋯Cu distance less than 2.8 Å gave 80 hits, among which is an example close to the title structure, i.e. catena-[(μ2-N-benzylpiperazine-N,N′)tetrakis(μ2-cyano)tetracopper(I)] (refcode LOGWIO; Lim et al., 2008), where the resulting network is composed of planar rows of undulating CuCN chains running roughly parallel to the a axis and crosslinked by bridging benzylpiperazine ligands in the c direction, forming two-dimensional double sheets capped by nonbridging ligands. Two Cu⋯Cu interactions are present in the mentioned coordination polymer, with distances of 2.6650 (6) and 2.9644 (6) Å.
5. Synthesis and crystallization
Crystals of the title compound were obtained by slow diffusion within three layers in a 3 ml glass tube. The first layer was a solution of K[Cu(CN)2] (7.7 mg, 0.05 mmol) in 1 ml of H2O, the second layer was a H2O/EtOH mixture (1:1 v/v, 1 ml) and the third layer was a solution of 2-ethoxypyrazine (3.1 mg, 0.025 mmol) in 0.5 ml of EtOH. After two weeks, colourless block-shaped crystals had formed in the middle layer. The crystals were kept under the mother solution prior to measurement.
6. Refinement
Crystal data, data collection and structure . All H atoms were placed geometrically and refined as riding, with C—H = 0.93 Å and Uiso(H) = 1.2Ueq(C) for aromatic hydrogens, C—H = 0.97 Å and Uiso(H) = 1.2Ueq(C) for the CH2 group, and C—H = 0.96 Å and Uiso(H) = 1.5Ueq(C) for the CH3 group. A rotating model was used for the methyl group. All cyano ligands are disordered over two sites with occupancies of 0.5. The coordinates of C and N atoms sharing the same sites and their displacement ellipsoids were constrained to be the same.
details are summarized in Table 2Supporting information
https://doi.org/10.1107/S205698901901452X/rz5265sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S205698901901452X/rz5265Isup2.hkl
Data collection: SAINT (Bruker, 2013); cell
APEX2 (Bruker, 2013); data reduction: SAINT (Bruker, 2013); 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).[Cu(CN)(C6H8N2O)][Cu(CN)] | F(000) = 1200 |
Mr = 303.26 | Dx = 1.925 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
a = 26.840 (5) Å | Cell parameters from 1229 reflections |
b = 4.830 (1) Å | θ = 3.1–22.8° |
c = 18.620 (4) Å | µ = 4.04 mm−1 |
β = 119.91 (3)° | T = 293 K |
V = 2092.3 (9) Å3 | Block, colourless |
Z = 8 | 0.09 × 0.04 × 0.01 mm |
Bruker SMART CCD diffractometer | 1396 reflections with I > 2σ(I) |
ω scan | Rint = 0.113 |
Absorption correction: multi-scan (SADABS; Bruker, 2014) | θmax = 27.9°, θmin = 1.8° |
Tmin = 0.630, Tmax = 0.746 | h = −34→31 |
12437 measured reflections | k = −6→6 |
2498 independent reflections | l = −24→24 |
Refinement on F2 | Primary atom site location: dual |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.045 | H-atom parameters constrained |
wR(F2) = 0.091 | w = 1/[σ2(Fo2) + (0.0339P)2] where P = (Fo2 + 2Fc2)/3 |
S = 0.84 | (Δ/σ)max = 0.001 |
2498 reflections | Δρmax = 1.72 e Å−3 |
137 parameters | Δρmin = −0.73 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 | Occ. (<1) | |
Cu1 | 0.48390 (3) | 0.21483 (12) | 0.37001 (4) | 0.02665 (19) | |
Cu2 | 0.60202 (3) | 0.16869 (12) | 0.43005 (4) | 0.0350 (2) | |
O1 | 0.31627 (15) | 0.7706 (7) | 0.3834 (2) | 0.0307 (8) | |
N5 | 0.42154 (19) | 0.5236 (7) | 0.3357 (2) | 0.0242 (10) | |
N6 | 0.3369 (2) | 0.9360 (8) | 0.2842 (3) | 0.0303 (11) | |
C4 | 0.6090 (2) | 0.7890 (9) | 0.4339 (3) | 0.0284 (11) | 0.5 |
C5 | 0.3898 (2) | 0.5558 (10) | 0.3714 (3) | 0.0230 (12) | |
H5 | 0.395884 | 0.440570 | 0.415076 | 0.028* | |
C3 | 0.6081 (2) | 0.5524 (10) | 0.4335 (3) | 0.0313 (12) | 0.5 |
C8 | 0.4114 (2) | 0.7025 (10) | 0.2737 (3) | 0.0256 (11) | |
H8 | 0.432622 | 0.687906 | 0.246866 | 0.031* | |
C6 | 0.3472 (2) | 0.7606 (10) | 0.3445 (3) | 0.0269 (12) | |
C7 | 0.3710 (3) | 0.9009 (10) | 0.2504 (3) | 0.0320 (14) | |
H7 | 0.366143 | 1.021425 | 0.208471 | 0.038* | |
C9 | 0.2705 (2) | 0.9697 (11) | 0.3541 (4) | 0.0355 (14) | |
H9A | 0.242718 | 0.935695 | 0.296265 | 0.043* | |
H9B | 0.285567 | 1.155698 | 0.359242 | 0.043* | |
C10 | 0.2431 (3) | 0.9374 (13) | 0.4063 (4) | 0.0437 (16) | |
H10A | 0.210384 | 1.058036 | 0.386082 | 0.066* | |
H10B | 0.270287 | 0.984284 | 0.462610 | 0.066* | |
H10C | 0.230857 | 0.749007 | 0.403666 | 0.066* | |
N3 | 0.6081 (2) | 0.5524 (10) | 0.4335 (3) | 0.0313 (12) | 0.5 |
N4 | 0.6090 (2) | 0.7890 (9) | 0.4339 (3) | 0.0284 (11) | 0.5 |
C2 | 0.4969 (2) | 0.0527 (9) | 0.4702 (3) | 0.0274 (12) | 0.5 |
C1 | 0.4978 (2) | 0.2054 (8) | 0.2793 (3) | 0.0254 (11) | 0.5 |
N1 | 0.4978 (2) | 0.2054 (8) | 0.2793 (3) | 0.0254 (11) | 0.5 |
N2 | 0.4969 (2) | 0.0527 (9) | 0.4702 (3) | 0.0274 (12) | 0.5 |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cu1 | 0.0346 (4) | 0.0309 (4) | 0.0197 (3) | 0.0007 (3) | 0.0175 (3) | 0.0022 (3) |
Cu2 | 0.0518 (5) | 0.0196 (3) | 0.0408 (5) | 0.0005 (3) | 0.0285 (4) | −0.0002 (3) |
O1 | 0.030 (2) | 0.041 (2) | 0.0252 (19) | 0.0082 (18) | 0.0169 (17) | 0.0077 (17) |
N5 | 0.035 (3) | 0.017 (2) | 0.022 (2) | −0.0055 (19) | 0.016 (2) | −0.0010 (18) |
N6 | 0.035 (3) | 0.022 (2) | 0.031 (3) | −0.002 (2) | 0.015 (3) | 0.003 (2) |
C4 | 0.035 (3) | 0.026 (2) | 0.024 (3) | 0.000 (2) | 0.015 (2) | −0.001 (2) |
C5 | 0.033 (3) | 0.022 (3) | 0.017 (3) | 0.000 (2) | 0.015 (3) | 0.002 (2) |
C3 | 0.038 (3) | 0.032 (3) | 0.021 (3) | 0.001 (3) | 0.013 (3) | −0.003 (2) |
C8 | 0.036 (3) | 0.026 (3) | 0.020 (3) | −0.004 (3) | 0.018 (3) | 0.000 (2) |
C6 | 0.036 (3) | 0.020 (2) | 0.024 (3) | −0.006 (2) | 0.015 (3) | −0.002 (2) |
C7 | 0.043 (4) | 0.026 (3) | 0.030 (3) | −0.006 (3) | 0.020 (3) | 0.007 (2) |
C9 | 0.030 (4) | 0.043 (3) | 0.031 (3) | 0.007 (3) | 0.013 (3) | 0.004 (3) |
C10 | 0.030 (4) | 0.063 (4) | 0.045 (4) | 0.013 (3) | 0.024 (3) | 0.009 (3) |
N3 | 0.038 (3) | 0.032 (3) | 0.021 (3) | 0.001 (3) | 0.013 (3) | −0.003 (2) |
N4 | 0.035 (3) | 0.026 (2) | 0.024 (3) | 0.000 (2) | 0.015 (2) | −0.001 (2) |
C2 | 0.033 (3) | 0.029 (3) | 0.021 (3) | 0.000 (2) | 0.014 (3) | 0.000 (2) |
C1 | 0.023 (3) | 0.025 (2) | 0.030 (3) | 0.002 (2) | 0.015 (2) | 0.003 (2) |
N1 | 0.023 (3) | 0.025 (2) | 0.030 (3) | 0.002 (2) | 0.015 (2) | 0.003 (2) |
N2 | 0.033 (3) | 0.029 (3) | 0.021 (3) | 0.000 (2) | 0.014 (3) | 0.000 (2) |
Cu1—Cu2 | 2.7958 (13) | C5—H5 | 0.9300 |
Cu1—N5 | 2.090 (4) | C5—C6 | 1.402 (7) |
Cu1—C2 | 1.888 (4) | C3—N4 | 1.143 (6) |
Cu1—C1 | 1.905 (4) | C8—H8 | 0.9300 |
Cu1—N1 | 1.905 (4) | C8—C7 | 1.347 (7) |
Cu1—N2 | 1.888 (4) | C7—H7 | 0.9300 |
Cu2—C3 | 1.859 (5) | C9—H9A | 0.9700 |
Cu2—N3 | 1.859 (5) | C9—H9B | 0.9700 |
O1—C6 | 1.347 (5) | C9—C10 | 1.492 (7) |
O1—C9 | 1.436 (6) | C10—H10A | 0.9600 |
N5—C5 | 1.325 (6) | C10—H10B | 0.9600 |
N5—C8 | 1.357 (6) | C10—H10C | 0.9600 |
N6—C6 | 1.322 (6) | C2—C2i | 1.155 (8) |
N6—C7 | 1.354 (6) | C1—C1ii | 1.152 (8) |
C4—N3 | 1.143 (6) | ||
N5—Cu1—Cu2 | 139.01 (11) | C7—C8—H8 | 119.5 |
C2—Cu1—Cu2 | 87.55 (16) | O1—C6—C5 | 116.4 (4) |
C2—Cu1—N5 | 108.86 (18) | N6—C6—O1 | 120.7 (5) |
C1—Cu1—Cu2 | 70.59 (14) | N6—C6—C5 | 122.9 (5) |
C1—Cu1—N5 | 103.17 (17) | N6—C7—H7 | 117.9 |
N1—Cu1—Cu2 | 70.59 (14) | C8—C7—N6 | 124.2 (5) |
N1—Cu1—N5 | 103.17 (17) | C8—C7—H7 | 117.9 |
N2—Cu1—Cu2 | 87.55 (16) | O1—C9—H9A | 110.4 |
N2—Cu1—N5 | 108.86 (18) | O1—C9—H9B | 110.4 |
C3—Cu2—Cu1 | 89.85 (17) | O1—C9—C10 | 106.7 (4) |
N3—Cu2—Cu1 | 89.85 (17) | H9A—C9—H9B | 108.6 |
C6—O1—C9 | 117.2 (4) | C10—C9—H9A | 110.4 |
C5—N5—Cu1 | 123.2 (3) | C10—C9—H9B | 110.4 |
C5—N5—C8 | 116.4 (4) | C9—C10—H10A | 109.5 |
C8—N5—Cu1 | 120.3 (3) | C9—C10—H10B | 109.5 |
C6—N6—C7 | 114.3 (4) | C9—C10—H10C | 109.5 |
N5—C5—H5 | 119.4 | H10A—C10—H10B | 109.5 |
N5—C5—C6 | 121.2 (4) | H10A—C10—H10C | 109.5 |
C6—C5—H5 | 119.4 | H10B—C10—H10C | 109.5 |
N4—C3—Cu2 | 176.6 (5) | C4—N3—Cu2 | 176.6 (5) |
N5—C8—H8 | 119.5 | C2i—C2—Cu1 | 177.4 (7) |
C7—C8—N5 | 121.0 (5) | C1ii—C1—Cu1 | 175.0 (6) |
Symmetry codes: (i) −x+1, −y, −z+1; (ii) −x+1, y, −z+1/2. |
Cg is the centroid of the C1/N1–C1i/N1i cyano group (symmetry code: (i) 1-x, y, 1/2-z) |
D—H···A | D—H | H···A | D···A | D—H···A |
C8—H8···Cg | 0.93 | 2.93 | 3.558 (6) | 126 |
Funding information
Funding for this research was provided by: Ministry of Education and Science of Ukraine (grant Nos. 19BF037-01M, 19BF037-04 and 19BF037-01).
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