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The crystal structure of the title compound, {[Cu(C4H4O6)(C2H6N4O2)]·4H2O}n, contains the central CuII cation in a distorted octa­hedral coordination, symmetrically chelated by the two imine N atoms of a neutral oxamide dioxime (H2oxado) ligand [Cu-N = 1.9829 (16) Å] and unsymmetrically bis-chelated by two halves of the L-(+)-tartrate(2-) (tart) ligands, each half being linked to the CuII cation via the deprotonated carboxyl­ate group and protonated hy­droxy group [Cu-O = 1.9356 (14) and 2.4674 (13) Å, respectively]. The extended asymmetric unit is defined by twofold axes, one passing through the CuII cation and the centre of the oxamide dioxime (H2oxado) ligand and the another two (symmetry related) bisecting the central C-C bonds of the tartrate ions. The structure is chiral, consisting of enantio­meric linear-chain polymers oriented along [001], with virtual monomeric {Cu(tart0.5)2(H2oxado)} repeat units and with the chains inter­leaved face-to-face into `twin pillars'. Nanochannels exist, running parallel to the c axis and bisecting a and b, which host `double strings' of solvent water mol­ecules. Extensive hydrogen bonding (O-H...O and N-H...O) between the chains and solvent water mol­ecules, together with extended [pi]-[sigma] inter­actions, consolidate the bulk crystal structure.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270112016435/sf3165sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270112016435/sf3165Isup2.hkl
Contains datablock I

CCDC reference: 879454

Comment top

A considerable number of crystal structures have been reported which deal with a wide range of metal(II) complexes based mainly on the tartrato(2-) ligand system (Adama et al., 2007; Bélombé, Nenwa, Fokwa & Dronskowski, 2009; Ge et al., 2008; González-Silgo et al., 1999; Liu et al., 2010; McCann et al., 1997; Ruiz-Pérez et al., 1996; Scherb et al., 2002; Soylu, 1985; Zhang et al., 2003; Zhao et al., 2009). Most of these studies utilized the tartrate(2-) anion (predominantly in the form of its pure enantiomers) and water molecules as the ligands linked directly to the central metal. Only a few examples have been reported where the tartrato(2-) ligand shares coordination to the central metal with another type of neutral ligand system, e.g. with two imidazole molecules to coordinate to ZnII (Adama et al., 2007), and with a phenanthroline molecule to coordinate to MnII (Zhang et al., 2003) or CuII (McCann et al., 1997). Therefore, the title compound, (I), represents only the second example of a chiral heteroleptic CuII complex polymer elucidated hitherto, involving the neutral chelating oxamide dioxime in lieu of the phenanthroline ligand.

The intrinsic nature of the tartrate(2-) anion as a polydentate ligand system offering various coordination modes to central metal ions, hence yielding a wide range of magnetic and optically active materials (applicable in advanced technologies), has been underscored in previous studies (Liu et al., 2010; Scherb et al., 2002; Soylu, 1985). Our current research aims to design, synthesize and study crystallized multifunctional materials that may combine, within a single system, a whole set of interesting physico-chemical properties such as magnetic, optoelectronic, nanoporous, electrical or hydrogen-bonding properties, etc. (Bélombé, Nenwa, Mbiangué, Bebga et al., 2009; Bélombé, Nenwa, Mbiangué, Majoumo-Mbé et al., 2009). Along these lines, we have recently prepared the chiral and paramagnetic metal–organic NiII salt, [Ni(H2oxado)3][L(+)tart].4H2O,which shows good promise of ferromagnetic ordering at about 10 K, and the report of which is currently in progress. The attempt to synthesize the CuII homologue led to the isolation of the unexpected title complex polymer, (I), which crystallizes in a new type of chiral channel lattice framework, hosting interesting `double strings' or `double filaments' of hydrogen-bonded solvate water molecules. We report herein the synthesis and crystal structure of {[Cu(tart)(H2oxado)].4H2O}n, (I).

The crystal structure of (I) consists of the chiral building blocks depicted in Fig. 1, highlighting the asymmetric unit. The crystal topology of (I) closely resembles that of the homologous [Cu(tar)(phen)].6H2O compound, (II), published earlier (McCann et al., 1997), with phenanthroline in lieu of the present oxamide dioxime as the neutral ligand. Thus, the two homologues appear to represent the only examples of such mixed-ligand CuII–tartrato complexes elucidated to date. It is worth noting that (II) crystallizes with orthorhombic symmetry, whereas (I) crystallizes in the tetragonal system.

In (I), the CuII cation lies on a two-fold axis which also relates the two halves of the chelating oxamide dioxime ligand. The coordination geometry at the CuII cation in (I) is a distorted prolate octahedron, similar to that in (II), despite the higher symmetry in (I). In (I), the bond to O2 [1.9355 (14) Å] is significantly shorter than that to O4 [2.4674 (13) Å]. In (II), by contrast, the two Cu—O4 bond lengths of 2.308 (4) and 2.328 (3) Å are unequal and shorter than those in (I). In (I), these bonds form an O—Cu—O angle of 149.31 (4)°, and while they are longer than in (II) they do compare fairly well with corresponding values observed earlier in related metal(II) tartrates, e.g. in MnII—OOH (2.433 and 2.621 Å; Soylu, 1985) in CdII—OOH [2.470 (3) and 2.449 (3) Å; Zhao et al., 2009].

The two materials adopt the same polymerization pattern, by which the tartrate(2-) ions act as bis-bidentate ligands to bridge neighbouring CuII sites, offering at each ligand end the deprotonated OCOO and protonated OOH atoms as oxygen donors. In (I), the tartrate anion is located so that a two-fold axis bisects the central bonds. The ends lie within two planes that are rotated relative to each other about the C3—C3iii line by a dihedral angle of 78.90 (8)° (see Table 1 for symmetry codes). Thus, the polymerization pattern ultimately gives rise to linear chain coordination motifs, with the chains oriented parallel to [100] in (II) and parallel to [001] in (I). The planes of the neutral ligands (phenanthroline or H2oxado) lie virtually perpendicular to the respective polymeric chains, with an intra-chain Cu···Cu spacing of 6.624 Å (= c) in (I) and 6.600 Å in (II). Note that in Fig. 1 the virtual repeat unit of a polymeric chain consists of two symmetry-related halves of tartrato(2-) ligands, involving atoms O2/C2/O3/C3/O4 and O2vi/C2vi/O3vi/C3vi/O4vi [symmetry code (i) in Fig. 1 - please correct text or figure], and one oxamide dioxime ligand. The three ligands each chelate the central CuII cation in a pentacyclic coordination, the coordination polyhedron being defined by rotational symmetry about a C2 axis through the CuII centre and the midpoint of the C1—C1vi segment in the H2oxado ligand. It is quite obvious that the H2oxado ligand, with its hydroximinic and aminic functional groups, will promote hydrogen bonding more efficiently than the phenanthroline ligand, which lacks such functional groups. Hydrogen-bond parameters for (I) are collected in Table 1.

The individual polymeric chains of (I) pair up face-to-face in a zipper-type packing mode via mutual interleaving of their H2oxado ligands to form twin pillars, as shown in Fig. 2. N—H···O hydrogen bonding occurs between these pillars. The roughly planar H2oxado ligands are superimposed on top of each other such that the CN iminic double bonds of one ligand interact with the C—N aminic single bonds of neighbouring ligands, resulting in πσ interactions at a centroid-to-centroid spacing of ca 3.312 Å (= c/2). This spacing compares fairly well with the average value of 3.300 Å reported for the phenanthroline ligand in (II), where pure ππ interactions are operative. The shortest interchain separation of the metal centres is Cu···Cu = 6.702 Å in (I). Additionally, O—H···O bonding can be observed between the O—H groups of the tartrate anions and the solvent water molecules.

A juxtaposition of two unit cells of (I), projected down the c axis, is depicted in Fig. 3, highlighting the disposition of the individual twin pillars. Any neighbouring four such pillars are oriented relative to one another so that they delineate a hose-like nanochannel, inside which the solvate waters line up to form four `double strings', reminiscent of the hydrogen-bonded solvent water molecules recently observed by Vallejo et al. (2010) in oxalate-bridged trinuclear CrIII–CoII complexes with aromatic diimine ligands. The structure of (I), we believe, ought to be welcomed as another promising template system within the narrow class of materials (Akutsu-Sato et al., 2005; Rashid et al., 2001; Infantes & Motherwell, 2002; Mascal et al.,2006; Martin et al., 2007) that are needed to probe the feasibility of the challenging prospect of one-dimensional proton conduction in solids (one-dimensional PCS) (Belombe et al., 2008, 2007; Bélombé, Nenwa, Mbiangué, Bebga et al., 2009), a prospect that may be likened somewhat to the novel ionic high proton conduction as a function of surrounding humidity level newly documented in a metal–organic framework which hosts ammonium cations and water molecules within functionalized lattice channels (Pardo et al., 2011).

Related literature top

For related literature, see: Adama et al. (2007); Akutsu-Sato, Akutsu, Turner & Day (2005); Ali et al. (2004); Bélombé, Nenwa, Fokwa & Dronskowski (2009); Bélombé, Nenwa, Mbiangué, Bebga, Majoumo-Mbé, Hey-Hawkins & Lönnecke (2009); Bélombé, Nenwa, Mbiangué, Majoumo-Mbé, Lönnecke & Hey-Hawkins (2009); Belombe et al. (2007, 2008); Ephraim (1889); Ge et al. (2008); González-Silgo, González-Platas, Ruiz-Pérez, López & Torres (1999); Infantes & Motherwell (2002); Liu et al. (2010); Martin et al. (2007); Mascal et al. (2006); McCann et al. (1997); Pardo et al. (2011); Rashid et al. (2001); Ruiz-Pérez, Hernández-Molina, González-Silgo, López, Yanes & Solans (1996); Scherb et al. (2002); Soylu (1985); Vallejo et al. (2010); Zhang et al. (2003); Zhao et al. (2009).

Experimental top

We have now rationalized a procedure by which compound (I) can be prepared systematically in stoichiometric proportions. Thus, pure oxamide dioxime (0.12 g, 1 mmol; Ephraim, 1889; Ali et al., 2004) and pure L(+)-tartaric acid [0.17 g, 1.13 mmol (in slight excess to maintain the medium acidic pH 3), LABOSI] were dissolved in lukewarm ( 318 K) water (100 ml) and stirred magnetically. CuCO3Cu(OH)2 (0.11 g, 0.5 mmol; Riedel de Haën, chemically pure) was added progressively. The solution mixture turned green immediately, then green fibres precipitated instantaneously. The green fibres were separated by filtration, washed twice with cold water (5 ml each) and dried in air to constant weight, yielding 0.32 g of (I) [80%, m.p. 508 K (decomposition)]. Spectroscopic analysis: IR (KBr, ν, cm-1): 3556 (O—H), 3392–3342 (N—H), 1715 (CO), 1676–1497 (oxime). Single crystals of (I) suitable for X-ray diffraction were grown by slow evaporation at room temperature of a supersaturated aqueous solution over the course of a few weeks.

Refinement top

H atoms were placed at their calculated positions and refined as riding on their respective carrier atoms.

Computing details top

Data collection: COLLECT (Nonius, 1999); cell refinement: DIRAX (Duisenberg, 1992); data reduction: EVALCCD (Duisenberg et al., 2003); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. The extended asymmetric unit of (I), showing the coordination environment of the CuII cation and the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Symmetry codes are as in Table 1. [Please clarify (i) in figure versus (vi) in text]
[Figure 2] Fig. 2. Interleaving of the H2oxado ligand of (I) via N—H···O hydrogen bonds (dashed lines), yielding a zipper-like pattern. Not all hydrogen bonds are shown.
[Figure 3] Fig. 3. The structure of (I) in a central projection along c. H atoms have been omitted.
catena-Poly[[[(oxamide dioxime-κ2N,N')copper(II)]-µ-L-tartrato- κ4O1,O2:O3,O4] tetrahydrate] top
Crystal data top
[Cu(C4H4O6)(C2H6N4O2)]·4H2ODx = 1.882 Mg m3
Mr = 401.77Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P43212Cell parameters from 171 reflections
Hall symbol: P 4nw 2abwθ = 3.7–22.3°
a = 14.6316 (9) ŵ = 1.62 mm1
c = 6.6239 (4) ÅT = 299 K
V = 1418.1 (2) Å3Block, green
Z = 40.37 × 0.18 × 0.14 mm
F(000) = 828
Data collection top
Bruker Nonius KappaCCD area-detector
diffractometer
1426 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.039
ω scansθmax = 27.5°, θmin = 5.0°
Absorption correction: multi-scan
SADABS (Sheldrick, 2003)
h = 1519
Tmin = 0.629, Tmax = 0.798k = 1816
10357 measured reflectionsl = 78
1624 independent reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.024 w = 1/[σ2(Fo2) + (0.0277P)2 + 0.0841P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.053(Δ/σ)max < 0.001
S = 1.02Δρmax = 0.21 e Å3
1624 reflectionsΔρmin = 0.20 e Å3
103 parametersAbsolute structure: Flack (1983), with 644 Friedel pairs
0 restraintsAbsolute structure parameter: 0.021 (13)
Primary atom site location: structure-invariant direct methods
Crystal data top
[Cu(C4H4O6)(C2H6N4O2)]·4H2OZ = 4
Mr = 401.77Mo Kα radiation
Tetragonal, P43212µ = 1.62 mm1
a = 14.6316 (9) ÅT = 299 K
c = 6.6239 (4) Å0.37 × 0.18 × 0.14 mm
V = 1418.1 (2) Å3
Data collection top
Bruker Nonius KappaCCD area-detector
diffractometer
1624 independent reflections
Absorption correction: multi-scan
SADABS (Sheldrick, 2003)
1426 reflections with I > 2σ(I)
Tmin = 0.629, Tmax = 0.798Rint = 0.039
10357 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.024H-atom parameters constrained
wR(F2) = 0.053Δρmax = 0.21 e Å3
S = 1.02Δρmin = 0.20 e Å3
1624 reflectionsAbsolute structure: Flack (1983), with 644 Friedel pairs
103 parametersAbsolute structure parameter: 0.021 (13)
0 restraints
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Cu10.14080.14080.00000.01952 (10)
C10.02603 (11)0.04600 (12)0.0037 (3)0.0173 (4)
C20.18881 (12)0.29030 (12)0.2560 (3)0.0193 (4)
C30.23919 (13)0.22103 (12)0.3889 (3)0.0185 (4)
N10.00707 (11)0.12625 (11)0.0363 (3)0.0213 (4)
N20.11351 (11)0.02580 (12)0.0238 (3)0.0261 (4)
O10.05969 (10)0.19413 (10)0.0267 (3)0.0369 (4)
O20.14398 (11)0.26419 (9)0.1051 (2)0.0269 (3)
O30.19637 (12)0.37216 (10)0.3041 (2)0.0352 (4)
O40.21444 (9)0.13028 (9)0.3343 (2)0.0205 (3)
O50.37291 (12)0.04366 (11)0.3020 (3)0.0394 (4)
O60.14712 (11)0.47039 (10)0.0276 (3)0.0387 (4)
H30.30300.23150.36530.022*
H2A0.14820.07010.02050.031*
H2B0.12630.02720.04710.031*
H10.03400.24130.09990.044*
H40.25830.09990.31240.025*
H5A0.36800.01320.26430.047*
H5B0.39780.06290.21580.047*
H6A0.13790.51930.00200.046*
H6B0.15880.44140.09190.046*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cu10.0179 (2)0.0190.02214 (17)0.00422 (13)0.0020.002
C10.0175 (9)0.0220 (9)0.0123 (9)0.0027 (7)0.0012 (8)0.0002 (9)
C20.0218 (9)0.0179 (9)0.0184 (10)0.0046 (7)0.0030 (10)0.0003 (9)
C30.0163 (10)0.0160 (10)0.0230 (11)0.0045 (7)0.0026 (8)0.0010 (8)
N10.0215 (8)0.0168 (9)0.0257 (10)0.0035 (6)0.0006 (7)0.0008 (7)
N20.0191 (9)0.0232 (9)0.0360 (12)0.0023 (6)0.0032 (8)0.0044 (8)
O10.0293 (8)0.0234 (8)0.0581 (12)0.0091 (6)0.0040 (8)0.0056 (8)
O20.0307 (8)0.0193 (7)0.0306 (8)0.0020 (6)0.0132 (7)0.0012 (6)
O30.0606 (11)0.0177 (8)0.0273 (9)0.0024 (7)0.0100 (7)0.0004 (6)
O40.0223 (7)0.0150 (7)0.0243 (7)0.0007 (5)0.0009 (6)0.0016 (6)
O50.0444 (10)0.0304 (8)0.0435 (11)0.0055 (7)0.0050 (8)0.0020 (7)
O60.0453 (10)0.0268 (8)0.0439 (10)0.0009 (7)0.0007 (9)0.0094 (7)
Geometric parameters (Å, º) top
Cu1—O2i1.9355 (14)C3—C3ii1.519 (4)
Cu1—O21.9356 (14)N1—O11.395 (2)
Cu1—N1i1.9829 (16)C3—H30.9587
Cu1—N11.9829 (16)N2—H2A0.8230
C1—N11.288 (2)N2—H2B0.8126
C1—N21.326 (2)O1—H10.9237
C1—C1i1.491 (3)O4—H40.7939
C2—O31.244 (2)O5—H5A0.8711
C2—O21.255 (3)O5—H5B0.7327
C2—C31.531 (3)O6—H6A0.7473
C3—O41.423 (2)O6—H6B0.9147
O2i—Cu1—O294.85 (9)C1—N1—O1112.22 (15)
O2i—Cu1—N1i94.61 (6)C1—N1—Cu1116.66 (12)
O2—Cu1—N1i165.16 (6)O1—N1—Cu1127.53 (12)
O2i—Cu1—N1165.16 (6)C2—O2—Cu1125.65 (12)
O2—Cu1—N194.61 (6)O4—C3—H3110.8
N1i—Cu1—N178.62 (9)C3ii—C3—H3107.5
N1—C1—N2126.09 (16)C2—C3—H3105.6
N1—C1—C1i112.58 (11)C1—N2—H2A114.6
N2—C1—C1i121.32 (12)C1—N2—H2B117.5
O3—C2—O2122.90 (19)H2A—N2—H2B127.9
O3—C2—C3116.56 (18)N1—O1—H1103.0
O2—C2—C3120.53 (16)C3—O4—H4111.4
O4—C3—C3ii111.41 (11)H5A—O5—H5B100.6
O4—C3—C2110.42 (14)H6A—O6—H6B106.3
C3ii—C3—C2110.9 (2)
Symmetry codes: (i) y, x, z; (ii) y, x, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H2A···O3iii0.822.443.164 (2)148
N2—H2B···O4iv0.812.132.878 (2)152
O1—H1···O6v0.921.822.696 (2)157
O4—H4···O50.791.872.651 (2)168
O5—H5A···O3vi0.872.272.869 (2)126
O5—H5A···O5vii0.872.533.236 (2)138
O5—H5B···O6i0.732.052.762 (2)164
O6—H6A···O2viii0.752.512.956 (2)121
O6—H6A···O3viii0.752.623.362 (2)171
Symmetry codes: (i) y, x, z; (iii) x1/2, y+1/2, z+1/4; (iv) x, y, z1/2; (v) y1/2, x+1/2, z+1/4; (vi) x+1/2, y1/2, z+3/4; (vii) y+1/2, x1/2, z1/4; (viii) y+1/2, x+1/2, z1/4.

Experimental details

Crystal data
Chemical formula[Cu(C4H4O6)(C2H6N4O2)]·4H2O
Mr401.77
Crystal system, space groupTetragonal, P43212
Temperature (K)299
a, c (Å)14.6316 (9), 6.6239 (4)
V3)1418.1 (2)
Z4
Radiation typeMo Kα
µ (mm1)1.62
Crystal size (mm)0.37 × 0.18 × 0.14
Data collection
DiffractometerBruker Nonius KappaCCD area-detector
diffractometer
Absorption correctionMulti-scan
SADABS (Sheldrick, 2003)
Tmin, Tmax0.629, 0.798
No. of measured, independent and
observed [I > 2σ(I)] reflections
10357, 1624, 1426
Rint0.039
(sin θ/λ)max1)0.649
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.024, 0.053, 1.02
No. of reflections1624
No. of parameters103
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.21, 0.20
Absolute structureFlack (1983), with 644 Friedel pairs
Absolute structure parameter0.021 (13)

Computer programs: COLLECT (Nonius, 1999), DIRAX (Duisenberg, 1992), EVALCCD (Duisenberg et al., 2003), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 2006), publCIF (Westrip, 2010).

Selected geometric parameters (Å, º) top
Cu1—O21.9356 (14)Cu1—N11.9829 (16)
O2i—Cu1—O294.85 (9)O2—Cu1—N194.61 (6)
O2—Cu1—N1i165.16 (6)N1i—Cu1—N178.62 (9)
Symmetry code: (i) y, x, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H2A···O3ii0.822.443.164 (2)148
N2—H2B···O4iii0.812.132.878 (2)152
O1—H1···O6iv0.921.822.696 (2)157
O4—H4···O50.791.872.651 (2)168
O5—H5A···O3v0.872.272.869 (2)126
O5—H5A···O5vi0.872.533.236 (2)138
O5—H5B···O6i0.732.052.762 (2)164
O6—H6A···O2vii0.752.512.956 (2)121
O6—H6A···O3vii0.752.623.362 (2)171
Symmetry codes: (i) y, x, z; (ii) x1/2, y+1/2, z+1/4; (iii) x, y, z1/2; (iv) y1/2, x+1/2, z+1/4; (v) x+1/2, y1/2, z+3/4; (vi) y+1/2, x1/2, z1/4; (vii) y+1/2, x+1/2, z1/4.
 

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