A novel mixed-valence copper complex, poly[[μ₂-4,4′-bipyridine-μ₃-pyridine-2,4,6-tricarboxyl­ato-di­copper(I,II)] monohydrate]

In the title novel mixed-valence copper complex, {[Cu₂(C₈H₂NO₆)(C₁₀H₈N₂)]·H₂O}_n, the Cu^I and Cu^II ions are linked by 4,4′-bipyridine (bpy) and pyridine-2,4,6-tricarboxyl­ate (ptc) ligands into corrugated layers, which are assembled via inter­layer C—H...O hydrogen bonds to give a three-dimensional supra­molecular architecture.

S1. Comment

In recent years, great interest has been focused on the rapidly expanding field of coordination polymers, due to their potential applications as catalysts and as materials with unique magnetic or optical properties (Eddaoudi et al., 2002; Rouzo et al., 1995; Li et al.,1998). For the syntheses of two- or three-dimensional complexes, many rigid polydentate ligands, such as 1,3,5-benzenetricarboxylic acid (H₃tma) (Yaghi et al., 1996), 1,3-adamantanedicarboxylic acid (Millange et al., 2004), 2,6-pyridinedicarboxylic acid (H₂pdc) (Murtha & Walton, 1974), have been widely used. However, 2,4,6-pyridinetricarboxylic acid (H₃ptc) has rarely been explored to construct coordination polymers (Gao et al., 2005; Ghosh et al., 2004; Ghosh & Bharadwaj, 2005). The limited investigation to date shows that the structural dimensionality of ptc complexes depends on the coordination modes of the ptc ligand (Gao et al., 2005). Here, we report the title novel mixed-valence copper complex, [Cu^IICu^I(ptc)(bpy)·H₂O]_n, (I), which was obtained by hydrothermal reaction of bpy, H₃ptc and Cu(ClO₄)₂·6H₂O at 423 K. Cu^II salts can be reduced to Cu^I or to mixed-valence compounds by 4,4'-bipyridine or 2,2'-bipyridine via hydrothermal reactions (Yang et al., 1999).

Compound (I) is composed of solvent water molecules and two-dimensional corrugated polymeric layers, [Cu^ICu^II(bpy)(ptc)]_n, where the cupric cations (Cu1) are in a square-pyramidal N₂O₃ coordination environment defined by one bpy and two ptc anions, with one carboxylate atom O5ⁱ atom at the apical position [symmetry code: (i) 1/2 − x, 1/2 + y, 3/2 − z] (Table 1), and the cuprous cations (Cu2) are linearly coordinated by one N atom of one bpy ligand and one carboxylate O atom of one ptc anion. Within the polymeric layer, the cupric and cuprous cations (Cu1 and Cu2) are alternately bridged by bpy and ptc ligands in the [001] direction and further interlinked through the apical carboxylate O5 atoms at the Cu1 atoms in the [010] direction. As illustrated in Fig. 2, the polymeric layers can be viewed topologically as rail-sharing ladders, which are oriented nearly perpendicular to one another [the dihedral angle between adjacent ladders is 86.02 (2)°].

The bond lengths involving the cupric cations (Cu1) are comparable with those reported in the literature. The Cu—O and Cu—N distances are close to those observed in the compounds [Cu(phen)(BzCN)]₂·2BF₄ [phen is 1,10-phenanthroline; BzCN is ? Please define; Cu2—N2 = 1.859 (9) Å and Cu2—N3 = 1.877 (9) Å; Lopez & Keller, 1999] and [Cu₃(C₆H₂Me₃-2,4,6)(O₂CC₆H₅)₂] [Cu2—O2 = 1.855 (5) Å; Aalten et al., 1989], but a little shorter than those in [Cu₆(Iso)₆]·2H₂O [Iso is ? Please define; Cu1—O3 = 2.1919 (14) Å, Cu1—O4a = 2.1869 (14) Å, Cu2—N21 = 2.1410 (16) Å, Cu2—N31 = 2.1389 (15) Å, Cu3—N11 = 2.1538 (15) Å and Cu3—O1 = 2.1367 (14) Å; Liu & Yuan, 2005] [bond lengths and angles for (I) are listed in Table 1].

The ptc anions display nearly perfect coplanarity, with a maximum deviation from the best plane of 0.022 (1) Å [For which atom?]. The coordination modes of the carboxylate groups are different. The 2-carboxylate atom O1 is bound to the cupric cation (Cu1) in an anti fashion, the 4-carboxylate atom O3 to the cuprous cation (Cu2) in a syn fashion, and the 6-carboxylate bidentately bridges two cupric cations in a syn–anti fashion. The bridging bpy ligands are twisted, with a dihedral angle of 39.6 (1)° between the component pyridyl rings.

The solvent water molecules form nearly linear hydrogen bonds to the coordinated (O1) and uncoordinated (O4) atoms of different ladders of one layer, with O···O distances in the range 2.786 (8)–3.284 (8) Å (Table 1). The polymeric layers are stacked along the [001] direction to meet the requirements of close packing, and weak classical interlayer C—H···O hydrogen bonding and a non-classical C17—H9···O1 hydrogen-bonding interaction (Steiner, 1996) make a significant contribution to the stabilization of the crystal structure.

S2. Experimental

Cu(ClO₄)₂·6H₂O (0.3705 g, 1.00 mmol), bpy (0.1560 g, 1.00 mmol), H₃ptc (0.1402 g, 0.67 mmol) and H₂O (10 ml) were added to a 23 ml Teflon-lined autoclave retort and heated for 160 h at 443 K, then cooled to room temperature. Blue block crystals of (I) were collected, washed with methanol and dried in the air [yield ca 2% based on the initial Cu(ClO₄)₂·6H₂O input].

S3. Refinement

H atoms attached to C atoms were positioned geometrically and refined using a riding model, with C—H = 0.93 and 0.97 Å, and with U_iso(H) = 1.2U_eq(C). Water H atoms were found in a difference Fourier synthesis and refined with the O—H bond distances fixed as initially found and with U_iso(H) = 1.2U_eq(O).

The data were collected on Siemens P4 diffractometer at room temperature, and the crystal size is 0.10 × 0.08 × 0.06 mm³. The small crystal, a non-CCD instrument and room temperature resulted in a low ratio of observed to total reflections.

Computing details

Data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1997); software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. A view of the complex molecule of the title compound, showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 45% probability level. H atoms have been omitted for clarity. [Symmetry codes: (i) 1/2 − x, 1/2 + y, 3/2 − z; (ii) x − 3/2, 3/2 − y, z − 1/2; (iii) 3/2 + x, 3/2 − y, 1/2 + z; (iv) 1/2 − x, y − 1/2, 3/2 − z.]
	Fig. 2. A topological view of the [Cu^IICu^I(ptc)(bpy)]n layer. White bonds denote the bridging carboxylates, light-grey bonds the ptc ligands and dark-grey bonds the bpy ligands.
	Fig. 3. A perspective view of the crystal structure of (I), with hydrogen bonds shown as dashed lines. H atoms not involved in hydrogen bonds have been omitted for clarity.

poly[[µ-4,4'-bipyridine-µ₃-pyridine,2,4,6-tricarboxylato-dicopper(I,II)] monohydrate]

Crystal data

[Cu2(C8H2NO6)(C10H8N2)]·H2O	F(000) = 1020
Mr = 509.39	Dx = 1.939 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 32 reflections
a = 12.823 (3) Å	θ = 11.2–25°
b = 8.2800 (17) Å	µ = 2.49 mm^−1
c = 16.776 (3) Å	T = 298 K
β = 101.53 (3)°	Block, blue
V = 1745.2 (6) Å^3	0.10 × 0.08 × 0.06 mm
Z = 4

Data collection

Siemens P4 diffractometer	1439 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.065
Graphite monochromator	θmax = 27.5°, θmin = 1.8°
ω scans	h = −1→16
Absorption correction: ψ scan (North et al., 1968)	k = −1→10
Tmin = 0.651, Tmax = 0.758	l = −21→21
5160 measured reflections	3 standard reflections every 97 reflections
4011 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.056	H-atom parameters constrained
wR(F^2) = 0.116	w = 1/[σ^2(Fo^2) + (0.0277P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.90	(Δ/σ)max = 0.005
4011 reflections	Δρmax = 0.51 e Å^−3
272 parameters	Δρmin = −0.50 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.00052 (13)

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Cu1	0.34039 (6)	0.77279 (11)	0.65020 (5)	0.0312 (3)
Cu2	−0.30314 (6)	0.73763 (13)	0.37936 (5)	0.0434 (3)
N1	0.1932 (3)	0.7471 (7)	0.6048 (3)	0.0218 (12)
N2	0.4955 (4)	0.7642 (7)	0.6881 (3)	0.0280 (13)
N3	1.0504 (4)	0.7645 (7)	0.8352 (3)	0.0311 (14)
O1	0.3285 (3)	0.9247 (6)	0.5545 (2)	0.0356 (13)
O2	0.2102 (3)	1.0078 (5)	0.4450 (3)	0.0331 (13)
O3	−0.1606 (3)	0.7382 (7)	0.4273 (2)	0.0415 (14)
O4	−0.1828 (3)	0.5813 (6)	0.5322 (3)	0.0431 (14)
O5	0.1610 (4)	0.4703 (6)	0.7544 (3)	0.0405 (14)
O6	0.3024 (3)	0.6023 (6)	0.7259 (3)	0.0349 (13)
C1	0.1528 (5)	0.8274 (8)	0.5364 (4)	0.0268 (18)
C2	0.0471 (5)	0.8050 (8)	0.5000 (4)	0.0259 (17)
H1	0.0179	0.8599	0.4524	0.031*
C3	−0.0146 (5)	0.7006 (9)	0.5349 (4)	0.0279 (18)
C4	0.0314 (5)	0.6200 (8)	0.6062 (4)	0.0301 (18)
H2	−0.0090	0.5502	0.6312	0.036*
C5	0.1380 (5)	0.6450 (8)	0.6396 (4)	0.0251 (16)
C6	0.2363 (5)	0.9301 (8)	0.5081 (4)	0.0260 (17)
C7	−0.1304 (5)	0.6712 (9)	0.4960 (4)	0.0305 (19)
C8	0.2041 (5)	0.5618 (8)	0.7146 (4)	0.0249 (17)
C9	0.5626 (5)	0.7573 (9)	0.6365 (4)	0.0356 (18)
H3	0.5344	0.7569	0.5809	0.043*
C10	0.6721 (5)	0.7508 (9)	0.6618 (4)	0.0339 (18)
H4	0.7163	0.7396	0.6245	0.041*
C11	0.7139 (5)	0.7614 (9)	0.7445 (4)	0.0279 (17)
C12	0.6439 (5)	0.7714 (8)	0.7980 (4)	0.0296 (17)
H5	0.6696	0.7790	0.8538	0.035*
C13	0.5363 (5)	0.7699 (8)	0.7671 (4)	0.0320 (18)
H6	0.4900	0.7729	0.8033	0.038*
C14	0.8315 (4)	0.7619 (8)	0.7750 (4)	0.0258 (17)
C15	0.8993 (5)	0.8451 (8)	0.7359 (4)	0.0302 (18)
H7	0.8732	0.9008	0.6879	0.036*
C16	1.0066 (5)	0.8444 (9)	0.7691 (4)	0.036 (2)
H8	1.0512	0.9045	0.7430	0.043*
C17	0.9835 (5)	0.6806 (9)	0.8730 (4)	0.036 (2)
H9	1.0123	0.6225	0.9196	0.043*
C18	0.8764 (5)	0.6772 (8)	0.8459 (4)	0.0346 (19)
H10	0.8332	0.6192	0.8741	0.042*
O7	0.3857 (5)	0.5501 (8)	0.5152 (4)	0.114 (3)
H11	0.3701	0.6454	0.5275	0.137*
H12	0.3192	0.5324	0.5020	0.137*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0132 (4)	0.0427 (6)	0.0343 (5)	−0.0031 (5)	−0.0035 (4)	0.0049 (5)
Cu2	0.0161 (4)	0.0645 (8)	0.0441 (6)	−0.0012 (6)	−0.0071 (4)	0.0033 (6)
N1	0.009 (2)	0.030 (4)	0.023 (3)	0.003 (3)	−0.004 (2)	−0.006 (3)
N2	0.015 (3)	0.035 (4)	0.032 (3)	0.002 (3)	−0.001 (2)	0.002 (3)
N3	0.016 (3)	0.041 (4)	0.033 (3)	−0.001 (3)	−0.003 (3)	−0.007 (3)
O1	0.018 (3)	0.054 (3)	0.032 (3)	−0.009 (3)	−0.001 (2)	0.005 (3)
O2	0.031 (3)	0.041 (3)	0.026 (3)	−0.005 (3)	0.004 (2)	0.008 (2)
O3	0.024 (3)	0.069 (4)	0.028 (3)	−0.001 (3)	−0.002 (2)	−0.002 (3)
O4	0.019 (3)	0.061 (4)	0.049 (3)	−0.013 (3)	0.007 (3)	0.004 (3)
O5	0.033 (3)	0.046 (4)	0.042 (3)	−0.007 (3)	0.006 (3)	0.021 (3)
O6	0.019 (3)	0.048 (3)	0.035 (3)	0.000 (2)	−0.003 (2)	0.012 (3)
C1	0.022 (4)	0.032 (5)	0.025 (4)	−0.001 (4)	0.001 (3)	−0.003 (4)
C2	0.022 (4)	0.030 (4)	0.022 (4)	0.004 (3)	−0.003 (3)	0.007 (3)
C3	0.016 (3)	0.042 (5)	0.024 (4)	0.002 (4)	−0.002 (3)	0.001 (4)
C4	0.018 (4)	0.032 (5)	0.040 (4)	−0.009 (4)	0.008 (3)	−0.011 (4)
C5	0.017 (3)	0.025 (4)	0.033 (4)	−0.002 (3)	0.005 (3)	−0.002 (4)
C6	0.024 (4)	0.021 (4)	0.034 (4)	0.002 (3)	0.008 (4)	−0.009 (4)
C7	0.016 (4)	0.040 (5)	0.035 (4)	0.000 (4)	0.005 (3)	−0.009 (4)
C8	0.018 (4)	0.030 (4)	0.024 (4)	0.008 (3)	−0.002 (3)	−0.004 (3)
C9	0.022 (3)	0.049 (5)	0.034 (4)	0.001 (4)	0.001 (3)	0.007 (4)
C10	0.015 (3)	0.052 (5)	0.034 (4)	−0.007 (4)	0.003 (3)	0.002 (5)
C11	0.017 (4)	0.034 (5)	0.031 (4)	−0.002 (4)	0.001 (3)	0.003 (4)
C12	0.020 (3)	0.038 (5)	0.027 (3)	0.002 (4)	−0.006 (3)	0.003 (4)
C13	0.023 (3)	0.048 (5)	0.026 (4)	0.004 (4)	0.006 (3)	0.009 (4)
C14	0.013 (3)	0.031 (5)	0.033 (4)	0.004 (4)	0.002 (3)	−0.001 (4)
C15	0.018 (4)	0.044 (5)	0.026 (4)	0.004 (4)	−0.002 (3)	−0.003 (4)
C16	0.018 (4)	0.050 (5)	0.040 (5)	0.007 (4)	0.005 (3)	−0.002 (4)
C17	0.024 (4)	0.051 (5)	0.027 (4)	0.005 (4)	−0.008 (3)	0.004 (4)
C18	0.020 (4)	0.049 (5)	0.034 (4)	0.004 (4)	0.002 (3)	0.010 (4)
O7	0.048 (4)	0.080 (5)	0.190 (7)	−0.018 (4)	−0.036 (5)	0.016 (5)

Geometric parameters (Å, º)

Cu1—N1	1.900 (4)	C3—C4	1.395 (8)
Cu1—N2	1.965 (5)	C3—C7	1.517 (8)
Cu1—O1	2.020 (4)	C4—C5	1.385 (8)
Cu1—O6	2.022 (5)	C4—H2	0.9300
Cu1—O5^i	2.290 (5)	C5—C8	1.533 (8)
Cu2—O3	1.844 (4)	C9—C10	1.383 (7)
Cu2—N3^ii	1.876 (5)	C9—H3	0.9300
N1—C5	1.312 (7)	C10—C11	1.386 (7)
N1—C1	1.338 (7)	C10—H4	0.9300
N2—C13	1.326 (7)	C11—C12	1.393 (8)
N2—C9	1.338 (7)	C11—C14	1.493 (7)
N3—C16	1.316 (8)	C12—C13	1.373 (7)
N3—C17	1.356 (8)	C12—H5	0.9300
N3—Cu2^iii	1.876 (5)	C13—H6	0.9300
O1—C6	1.281 (7)	C14—C15	1.375 (8)
O2—C6	1.227 (7)	C14—C18	1.401 (8)
O3—C7	1.269 (8)	C15—C16	1.377 (8)
O4—C7	1.239 (8)	C15—H7	0.9300
O5—C8	1.214 (7)	C16—H8	0.9300
O5—Cu1^iv	2.290 (5)	C17—C18	1.358 (8)
O6—C8	1.281 (7)	C17—H9	0.9300
C1—C2	1.383 (8)	C18—H10	0.9300
C1—C6	1.515 (9)	O7—H11	0.8501
C2—C3	1.378 (8)	O7—H12	0.8501
C2—H1	0.9300
N1—Cu1—N2	170.3 (2)	O2—C6—C1	118.5 (6)
N1—Cu1—O1	80.8 (2)	O1—C6—C1	114.5 (6)
N2—Cu1—O1	100.9 (2)	O4—C7—O3	127.7 (6)
N1—Cu1—O6	80.1 (2)	O4—C7—C3	117.8 (6)
N2—Cu1—O6	97.3 (2)	O3—C7—C3	114.5 (7)
O1—Cu1—O6	160.71 (17)	O5—C8—O6	128.7 (6)
N1—Cu1—O5^i	102.33 (19)	O5—C8—C5	119.6 (6)
N2—Cu1—O5^i	87.1 (2)	O6—C8—C5	111.7 (6)
O1—Cu1—O5^i	95.78 (18)	N2—C9—C10	123.2 (6)
O6—Cu1—O5^i	91.34 (18)	N2—C9—H3	118.4
O3—Cu2—N3^ii	177.5 (2)	C10—C9—H3	118.4
C5—N1—C1	123.4 (5)	C9—C10—C11	118.1 (6)
C5—N1—Cu1	118.4 (4)	C9—C10—H4	121.0
C1—N1—Cu1	118.1 (5)	C11—C10—H4	121.0
C13—N2—C9	118.2 (5)	C10—C11—C12	118.6 (5)
C13—N2—Cu1	119.6 (4)	C10—C11—C14	120.4 (5)
C9—N2—Cu1	122.2 (4)	C12—C11—C14	121.1 (5)
C16—N3—C17	116.6 (5)	C13—C12—C11	119.0 (6)
C16—N3—Cu2^iii	124.2 (5)	C13—C12—H5	120.5
C17—N3—Cu2^iii	119.2 (4)	C11—C12—H5	120.5
C6—O1—Cu1	114.7 (4)	N2—C13—C12	122.9 (6)
C7—O3—Cu2	119.4 (5)	N2—C13—H6	118.6
C8—O5—Cu1^iv	153.9 (4)	C12—C13—H6	118.6
C8—O6—Cu1	116.3 (4)	C15—C14—C18	117.7 (6)
N1—C1—C2	119.3 (6)	C15—C14—C11	122.0 (6)
N1—C1—C6	111.8 (6)	C18—C14—C11	120.3 (6)
C2—C1—C6	128.9 (6)	C14—C15—C16	118.7 (6)
C3—C2—C1	119.5 (6)	C14—C15—H7	120.6
C3—C2—H1	120.3	C16—C15—H7	120.6
C1—C2—H1	120.3	N3—C16—C15	124.5 (7)
C2—C3—C4	119.0 (6)	N3—C16—H8	117.8
C2—C3—C7	121.0 (6)	C15—C16—H8	117.8
C4—C3—C7	120.1 (7)	N3—C17—C18	123.1 (6)
C5—C4—C3	119.3 (7)	N3—C17—H9	118.4
C5—C4—H2	120.4	C18—C17—H9	118.4
C3—C4—H2	120.4	C17—C18—C14	119.3 (7)
N1—C5—C4	119.6 (6)	C17—C18—H10	120.3
N1—C5—C8	113.2 (5)	C14—C18—H10	120.3
C4—C5—C8	127.1 (7)	H11—O7—H12	87.1
O2—C6—O1	127.0 (7)

Symmetry codes: (i) −x+1/2, y+1/2, −z+3/2; (ii) x−3/2, −y+3/2, z−1/2; (iii) x+3/2, −y+3/2, z+1/2; (iv) −x+1/2, y−1/2, −z+3/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O7—H11···O1	0.85	2.44	3.284 (8)	176
O7—H12···O4^v	0.85	1.97	2.786 (8)	162
C10—H4···O4^vi	0.93	2.57	3.432 (8)	155
C15—H7···O2^vii	0.93	2.39	3.310 (8)	168
C16—H8···O6^viii	0.93	2.47	3.238 (8)	140
C17—H9···O1^ix	0.93	2.58	3.257 (8)	130
C18—H10···O2^x	0.93	2.40	3.327 (8)	174

Symmetry codes: (v) −x, −y+1, −z+1; (vi) x+1, y, z; (vii) −x+1, −y+2, −z+1; (viii) −x+3/2, y+1/2, −z+3/2; (ix) −x+3/2, y−1/2, −z+3/2; (x) x+1/2, −y+3/2, z+1/2.