research communications
μ-chlorido-bis[(4-carboxypyridine-2-carboxylato-κ2N,O2)chloridocuprate(II)]
of a chloride-bridged copper(II) dimer: piperazine-1,4-dium bis(di-aInorganic Materials Chemistry Laboratory, Department of Pure and Applied Chemistry, University of Calabar, P.M.B. 1115-Calabar, Nigeria, and bDepartment of Chemistry, Missouri University of Science and Technology, Rolla, MO 65409, USA
*Correspondence e-mail: ayiayi72@gmail.com
Crystals of a new dimeric chloride-bridged cuprate(II) derived from pyridine-2,4-dicarboxylic acid were obtained solvothermally in the presence of piperazine and hydrochloric acid. The 4H12N2)[Cu2(C7H4NO4)2Cl4], revealed one of the carboxyl groups of the original pyridine-2,4-dicarboxylic acid ligand to be protonated, whereas the other is deprotonated and binds together with the pyridine N atom to the CuII atom. The coordination environment of the CuII atom is distorted square-pyramidal. One of the chloride ligands bridges two metal cations to form a centrosymmetric dimer with two different Cu—Cl distances of 2.2632 (8) and 2.7853 (8) Å, whereby the longer distance is associated with the apical ligand. The remaining chloride ligand is terminal at one of the basal positions, with a distance of 2.2272 (9) Å. In the crystal, the dimers are linked by intermolecular O—H⋯O hydrogen bonds, together with N—H⋯O and N—H⋯Cl interactions involving the centrosymmetric organic cation, into a three-dimensional supramolecular network. Further but weaker C—H⋯O and C—H⋯Cl interactions consolidate the packing.
determination of the title salt, (CCCDC reference: 1497751
1. Chemical context
In recent times, research on coordination polymers, popularly known as metal–organic frameworks (MOFs), have received great attention, not only for their potential applications in the area of gas storage, ion-exchange, non-linear optics, molecular sieves, catalysis, magnetism, and molecular sensing (Yaghi et al., 2003; Ockwig et al., 2005; Wang et al., 2005; Carlucci et al., 2003; Hill et al., 2005), but also for their rich structural chemistry (Li et al., 2016; Eddaoudi et al., 2015). In the design of compounds with metal–organic frameworks, versatile carboxylate ligands, derived from 1,4-benzenedicarboxylic acid, 1,3,5-benzenetricarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid or pyridine-2,4-dicarboxylic acid, have frequently been used owing to their abundant carboxylate groups possessing high affinity to metal cations (Li et al., 2004; Shi et al., 2004; Gutschke et al., 2001; Tao et al., 2000). A number of novel metal–organic frameworks have been constructed using di- or multicarboxylate ligands as linkers. Most of the reported MOF materials have been synthesized using solvothermal or hydrothermal synthetic conditions, often by using sealed autoclaves. These techniques have also been found to play an important role in preparing robust and stable inorganic compounds with open frameworks (Rao et al., 2001; Eddaoudi et al., 2001). The fact that the solubility of the reactants increases under hydrothermal methods makes the reaction more likely to occur at lower temperatures, with the formation of polymeric units through molecular building blocks (Zhao et al., 2007). Small changes in one or more of the reaction variables, such as temperature, time, pH or the solvent type, can have a profound influence on the product. In some cases, organic or alkylammonium cations are used as templates and/or structure-directing agents in the crystallization process of framework solids (Jiang et al., 1998; Cheetham et al., 1999). In the course of our investigations, we were interested in using pyridine-2,4-dicarboxylic acid as a source of N- and O-donors, in synthesizing a coordination polymer in an acidic medium under solvothermal conditions and in the presence of piperazine as an organic amine. In this context we report on the synthesis and of the title compound (C4H12N2)[Cu2(C7H4NO4)2Cl4], (I).
2. Structural commentary
The molecular structure of (I) showing the numbering scheme is presented in Fig. 1. The copper(II) atom is chelated by the O atom (O3) of the deprotonated carboxylic group and the pyridine N atom (N1) of the organic ligand, forming a five-membered chelate ring Cu1–N1–C1–C6–O3. Two bridging and one terminal chlorido ligands complete the distorted square-pyramidal coordination of the metal cation. The arrangement of the chlorido ligands is such that Cl1 is doubly bridging the two metal cations into a centrosymmetric dimer through edge-sharing. The apical Cu—Cl1(−x + 2, −y + 2, −z + 1) bond length of 2.7853 (9) Å is significantly longer than the other bridging Cu—Cl bond with a length of 2.2632 (8) Å. The square plane is formed by N1 and O3, both from the pyridine-2,4-dicarboxylate anion, Cl1 from the bridging chlorido ligand and Cl2 of the terminal chlorido ligand [2.2272 (9) Å]. This type of coordination has been previously described as a transition state between 4- and 5-coordinate (Qi et al., 2009). The distortion index (τ) assuming a square-pyramidal environment was calculated as 0.08 using the formula, τ = (β − α)/60 (α, β are the largest valence angles) proposed by Addison et al. (1984), which indicates only slight distortions from the ideal value where τ = 0. The Cu⋯Cu distance in the dimer is 3.5946 (9) Å, with an Cu—Cl—Cu bond angle of 90.19 (3)° and a Cl⋯Cl separation of 3.5831 (14) Å. The Cu—N and Cu—O bond lengths are 2.013 (2) and 1.963 (2) Å, respectively, and are in good agreement with similar compounds reported in the literature (Goddard et al., 1990; Tynan et al., 2005; Han et al., 2008; Liu et al., 2009; Qi et al., 2009). The chelate angle O3—Cu—N1 of 81.34 (9)° is, as expected, smaller than the N1—Cu—Cl1 and O3—Cu—Cl2 bond angles of 170.22 (7) and 165.23 (8)°, respectively. The inorganic anion has a charge of −2 that is compensated by the incorporation of a fully protonated piperazine molecule in the structure. The latter is located about an inversion centre.
3. Supramolecular features
The centrosymmetric dimers are linked by pairs of (carboxyl)O1—H3⋯O4(carboxylate) hydrogen bonds to form sheets parallel (100). The protonated centrosymmetric amine cations are situated between the sheets and are connected through N2—H⋯O2 interactions to one of the carbonyl oxygen atoms and various N—H⋯Cl interactions into a three-dimensional network (Table 1, Fig. 2). The carbonyl oxygen atom O2 also acts as a hydrogen-bond acceptor from pyridyl C—H groups (C2—H2⋯O2 and C4—H12⋯O2). These interactions, together with C—H⋯Cl interactions, further stabilize the three-dimensional supramolecular network structure.
4. Database survey
There are several copper(II) dimeric compounds in which the copper atoms are bridged by chlorido ligands (Marsh et al., 1983; Puschmann et al., 2001; Li et al., 2006; Lee, et al., 2008; Han et al., 2008; Øien et al., 2013; Choubey et al., 2015; Golchoubian & Nateghi 2016; Liu et al., 2009). A search of the Cambridge Structural Database (Version 5.38, November 2016; Groom et al., 2016), revealed numerous di-μ-chlorido bridged copper(II) compounds constructed with ligands having -N,O- donor atoms (Kapoor et al., 2002, 2004; Damous et al., 2013; Lumb et al., 2013; Smolentsev et al., 2014; Qureshi et al., 2016). However, the search did not reveal related complexes derived from pyridine-2,4-dicarboxylic acid and piperazine.
5. Synthesis and crystallization
The syntheses were carried out in Ace pressure tubes (15 cm3) and heated in programmable ovens. The reagents used for syntheses were obtained from Aldrich (Analar grade) and used without further purification. In a typical synthesis of (I), Cu(CH3COO)2·2H2O (0.1996 g, 1.0 mmol) was stirred together with pyridine-2,4-dicarboxylic acid (0.1671 g, 1.0 mmol) in 3.3 cm3 of n-butanol. This was followed by the addition of piperazine (0.940 g, 1.0 mmol) and the pH of the solution was adjusted to 2 by dropwise addition of 0.16 cm3 of conc. HCl. The resultant mixture was homogenized for 15 min before transferring into the reaction vessel and heated in an oven at 393 K for 48 h. The product, a crop of bluish crystalline material, was washed with distilled water and air-dried.
6. Refinement
Crystal data, data collection and structure . C-bound H atoms were treated as riding atoms, with C—H distances of 0.93 Å (aromatic) and 0.97 Å (aliphatic), and with Uiso(H) = 1.2Ueq(C). N- and O-bound H atoms were located in difference maps and were refined with N—H distances of 0.89 Å and O—H distances of 0.82 Å, and with Uiso(H) = 1.2Ueq(N) and Uiso(H) = 1.5Ueq(O), respectively.
details are summarized in Table 2
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Supporting information
CCDC reference: 1497751
https://doi.org/10.1107/S2056989017001013/wm5354sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017001013/wm5354Isup2.hkl
Data collection: SMART (Bruker, 2008); cell
SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: SHELXTL (Sheldrick, 2008) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).(C4H12N2)[Cu2(C7H4NO4)2Cl4] | F(000) = 692 |
Mr = 689.26 | Dx = 1.934 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 11.639 (3) Å | Cell parameters from 1016 reflections |
b = 9.224 (2) Å | θ = 2.9–26.8° |
c = 11.423 (3) Å | µ = 2.30 mm−1 |
β = 105.211 (3)° | T = 298 K |
V = 1183.4 (5) Å3 | Rod, blue |
Z = 2 | 0.05 × 0.02 × 0.02 mm |
Bruker SMART APEX CCD area detector diffractometer | 2392 reflections with I > 2σ(I) |
ω scans | Rint = 0.050 |
Absorption correction: multi-scan (SADABS; Bruker, 2008) | θmax = 28.3°, θmin = 2.9° |
Tmin = 0.946, Tmax = 0.955 | h = −15→15 |
14235 measured reflections | k = −12→12 |
2923 independent reflections | l = −15→15 |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.039 | H-atom parameters constrained |
wR(F2) = 0.127 | w = 1/[σ2(Fo2) + (0.1P)2] where P = (Fo2 + 2Fc2)/3 |
S = 0.86 | (Δ/σ)max = 0.001 |
2923 reflections | Δρmax = 0.55 e Å−3 |
164 parameters | Δρmin = −0.31 e Å−3 |
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 | ||
Cu1 | 0.84456 (3) | 1.01123 (4) | 0.42216 (3) | 0.02632 (15) | |
Cl1 | 0.99944 (6) | 1.14015 (7) | 0.39127 (7) | 0.02963 (19) | |
Cl2 | 0.82884 (8) | 0.86943 (9) | 0.26090 (7) | 0.0431 (2) | |
O3 | 0.82154 (19) | 1.1592 (2) | 0.5374 (2) | 0.0326 (5) | |
O4 | 0.7301 (2) | 1.2063 (2) | 0.6797 (2) | 0.0411 (6) | |
N1 | 0.7122 (2) | 0.9149 (2) | 0.4767 (2) | 0.0244 (5) | |
O1 | 0.4230 (2) | 0.8203 (3) | 0.7170 (2) | 0.0412 (6) | |
H3 | 0.379334 | 0.776566 | 0.750692 | 0.062* | |
C6 | 0.7489 (2) | 1.1293 (3) | 0.5993 (3) | 0.0259 (6) | |
N2 | 0.9556 (2) | 0.0777 (3) | 0.0881 (2) | 0.0358 (6) | |
H2A | 0.959588 | 0.169430 | 0.065288 | 0.043* | |
H2B | 0.926778 | 0.077335 | 0.152968 | 0.043* | |
C1 | 0.6847 (3) | 0.9859 (3) | 0.5683 (3) | 0.0246 (6) | |
O2 | 0.4234 (2) | 0.6091 (3) | 0.6208 (2) | 0.0468 (6) | |
C2 | 0.6029 (2) | 0.9326 (3) | 0.6261 (3) | 0.0261 (6) | |
H2 | 0.584506 | 0.983758 | 0.688974 | 0.031* | |
C8 | 1.0765 (3) | 0.0148 (3) | 0.1210 (3) | 0.0323 (7) | |
H27A | 1.073784 | −0.081047 | 0.155093 | 0.039* | |
H27B | 1.128410 | 0.074758 | 0.182456 | 0.039* | |
C7 | 0.4583 (3) | 0.7319 (3) | 0.6429 (3) | 0.0310 (6) | |
C4 | 0.5776 (3) | 0.7273 (3) | 0.4928 (3) | 0.0308 (6) | |
H12 | 0.542510 | 0.638592 | 0.465717 | 0.037* | |
C5 | 0.6597 (3) | 0.7892 (3) | 0.4394 (3) | 0.0294 (6) | |
H13 | 0.678695 | 0.741211 | 0.375346 | 0.035* | |
C3 | 0.5487 (3) | 0.7998 (3) | 0.5872 (3) | 0.0268 (6) | |
C9 | 0.8733 (3) | −0.0041 (3) | −0.0119 (3) | 0.0367 (7) | |
H26A | 0.796776 | 0.044487 | −0.034859 | 0.044* | |
H26B | 0.861083 | −0.100761 | 0.016075 | 0.044* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cu1 | 0.0282 (2) | 0.0222 (2) | 0.0335 (2) | −0.00475 (12) | 0.01701 (17) | −0.00548 (13) |
Cl1 | 0.0306 (4) | 0.0252 (3) | 0.0368 (4) | −0.0053 (3) | 0.0155 (3) | 0.0021 (3) |
Cl2 | 0.0595 (5) | 0.0385 (4) | 0.0410 (5) | −0.0166 (4) | 0.0305 (4) | −0.0152 (3) |
O3 | 0.0350 (11) | 0.0255 (10) | 0.0437 (12) | −0.0075 (9) | 0.0215 (10) | −0.0092 (9) |
O4 | 0.0424 (13) | 0.0372 (12) | 0.0520 (14) | −0.0066 (10) | 0.0272 (11) | −0.0194 (10) |
N1 | 0.0249 (11) | 0.0239 (12) | 0.0270 (11) | −0.0007 (9) | 0.0112 (9) | −0.0022 (9) |
O1 | 0.0441 (14) | 0.0401 (13) | 0.0497 (14) | −0.0112 (11) | 0.0306 (12) | −0.0032 (11) |
C6 | 0.0219 (13) | 0.0217 (13) | 0.0348 (15) | −0.0001 (10) | 0.0086 (11) | −0.0051 (11) |
N2 | 0.0454 (15) | 0.0311 (14) | 0.0334 (13) | 0.0120 (12) | 0.0150 (12) | 0.0001 (11) |
C1 | 0.0209 (12) | 0.0247 (14) | 0.0281 (14) | 0.0024 (10) | 0.0064 (11) | −0.0005 (10) |
O2 | 0.0573 (16) | 0.0355 (12) | 0.0581 (16) | −0.0167 (11) | 0.0337 (13) | −0.0040 (11) |
C2 | 0.0238 (13) | 0.0291 (14) | 0.0264 (13) | −0.0003 (11) | 0.0085 (11) | −0.0007 (11) |
C8 | 0.0422 (18) | 0.0228 (14) | 0.0280 (15) | 0.0016 (12) | 0.0027 (14) | −0.0002 (11) |
C7 | 0.0290 (14) | 0.0344 (16) | 0.0291 (14) | −0.0046 (12) | 0.0068 (12) | 0.0058 (12) |
C4 | 0.0309 (15) | 0.0276 (14) | 0.0350 (15) | −0.0075 (12) | 0.0106 (13) | −0.0022 (12) |
C5 | 0.0320 (15) | 0.0288 (15) | 0.0300 (14) | −0.0037 (12) | 0.0130 (12) | −0.0053 (11) |
C3 | 0.0240 (13) | 0.0276 (14) | 0.0291 (14) | 0.0002 (11) | 0.0076 (11) | 0.0037 (11) |
C9 | 0.0313 (17) | 0.0374 (18) | 0.0416 (19) | 0.0024 (12) | 0.0099 (15) | 0.0037 (13) |
Cu1—O3 | 1.963 (2) | N2—H2B | 0.8900 |
Cu1—N1 | 2.013 (2) | C1—C2 | 1.384 (4) |
Cu1—Cl2 | 2.2272 (9) | O2—C7 | 1.207 (4) |
Cu1—Cl1 | 2.2632 (8) | C2—C3 | 1.396 (4) |
Cu1—Cl1i | 2.7853 (9) | C2—H2 | 0.9300 |
O3—C6 | 1.267 (3) | C8—C9ii | 1.512 (5) |
O4—C6 | 1.225 (3) | C8—H27A | 0.9700 |
N1—C5 | 1.327 (4) | C8—H27B | 0.9700 |
N1—C1 | 1.343 (4) | C7—C3 | 1.502 (4) |
O1—C7 | 1.316 (4) | C4—C3 | 1.383 (4) |
O1—H3 | 0.8200 | C4—C5 | 1.385 (4) |
C6—C1 | 1.515 (4) | C4—H12 | 0.9300 |
N2—C8 | 1.476 (4) | C5—H13 | 0.9300 |
N2—C9 | 1.490 (4) | C9—H26A | 0.9700 |
N2—H2A | 0.8900 | C9—H26B | 0.9700 |
O3—Cu1—N1 | 81.34 (9) | C3—C2—H2 | 121.0 |
O3—Cu1—Cl2 | 165.23 (8) | N2—C8—C9ii | 111.4 (3) |
N1—Cu1—Cl2 | 95.35 (7) | N2—C8—H27A | 109.4 |
O3—Cu1—Cl1 | 89.63 (6) | C9ii—C8—H27A | 109.4 |
N1—Cu1—Cl1 | 170.22 (7) | N2—C8—H27B | 109.4 |
Cl2—Cu1—Cl1 | 94.33 (3) | C9ii—C8—H27B | 109.4 |
C6—O3—Cu1 | 116.83 (18) | H27A—C8—H27B | 108.0 |
C5—N1—C1 | 119.5 (2) | O2—C7—O1 | 124.8 (3) |
C5—N1—Cu1 | 127.7 (2) | O2—C7—C3 | 122.5 (3) |
C1—N1—Cu1 | 112.59 (18) | O1—C7—C3 | 112.7 (3) |
C7—O1—H3 | 109.5 | C3—C4—C5 | 118.7 (3) |
O4—C6—O3 | 124.7 (3) | C3—C4—H12 | 120.6 |
O4—C6—C1 | 120.5 (3) | C5—C4—H12 | 120.6 |
O3—C6—C1 | 114.8 (2) | N1—C5—C4 | 122.1 (3) |
C8—N2—C9 | 112.0 (2) | N1—C5—H13 | 118.9 |
C8—N2—H2A | 109.2 | C4—C5—H13 | 118.9 |
C9—N2—H2A | 109.2 | C4—C3—C2 | 119.4 (3) |
C8—N2—H2B | 109.2 | C4—C3—C7 | 118.0 (3) |
C9—N2—H2B | 109.2 | C2—C3—C7 | 122.6 (3) |
H2A—N2—H2B | 107.9 | N2—C9—C8ii | 110.8 (3) |
N1—C1—C2 | 122.2 (3) | N2—C9—H26A | 109.5 |
N1—C1—C6 | 113.9 (3) | C8ii—C9—H26A | 109.5 |
C2—C1—C6 | 123.9 (3) | N2—C9—H26B | 109.5 |
C1—C2—C3 | 118.0 (3) | C8ii—C9—H26B | 109.5 |
C1—C2—H2 | 121.0 | H26A—C9—H26B | 108.1 |
Symmetry codes: (i) −x+2, −y+2, −z+1; (ii) −x+2, −y, −z. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H3···O4iii | 0.82 | 1.79 | 2.603 (3) | 171 |
N2—H2A···Cl1iv | 0.89 | 2.78 | 3.562 (3) | 147 |
N2—H2A···O3iv | 0.89 | 2.22 | 2.861 (3) | 129 |
N2—H2B···Cl1v | 0.89 | 2.69 | 3.414 (3) | 139 |
N2—H2B···Cl2v | 0.89 | 2.69 | 3.360 (3) | 133 |
C2—H2···O2vi | 0.93 | 2.49 | 3.402 (4) | 169 |
C4—H12···O2vii | 0.93 | 2.56 | 3.362 (4) | 145 |
C5—H13···Cl2 | 0.93 | 2.71 | 3.269 (3) | 119 |
C8—H27A···Cl1viii | 0.97 | 2.72 | 3.561 (3) | 146 |
C8—H27B···Cl2ix | 0.97 | 2.81 | 3.599 (3) | 139 |
C9—H26A···O2x | 0.97 | 2.56 | 3.509 (4) | 165 |
C9—H26B···Cl1viii | 0.97 | 2.93 | 3.713 (3) | 139 |
C9—H26B···Cl2v | 0.97 | 2.93 | 3.491 (4) | 118 |
Symmetry codes: (iii) −x+1, y−1/2, −z+3/2; (iv) x, −y+3/2, z−1/2; (v) x, y−1, z; (vi) −x+1, y+1/2, −z+3/2; (vii) −x+1, −y+1, −z+1; (viii) −x+2, y−3/2, −z+1/2; (ix) −x+2, y−1/2, −z+1/2; (x) −x+1, y−1/2, −z+1/2. |
Acknowledgements
This work was supported by The World Academy of Sciences for the Advancement of Science in developing countries (TWAS) under Grant 1 2–1 69 RG/CHE/AF/AC-G–UNESCO FR: 3240271 320 for which grateful acknowledgment is made. AAA is also grateful to the Royal Society of Chemistry for a personal research grant. The authors are thankful for the support of Professor Amitava Choudhury of the Department of Chemistry, Missouri University of Science and Technology, Rolla, USA, for the single-crystal X-ray crystallographic data.
Funding information
Funding for this research was provided by: Academy of Sciences for the Developing Worldhttps://doi.org/10.13039/501100001689 (award No. 1 2-1 69 RG/CHE/AF/AC–G -UNESCO FR: 3240271 320).
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