A one-dimensional carboxyl­ate-bridged helical copper(II) complex containing (quinolin-8-yl­oxy)­acetate

The title compound, catena-poly[­[bromo­copper(II)]-μ-(quin­olin-8-yl­oxy)­acetato-κ⁴N,O,O′:O′′], [CuBr(C₁₁H₈NO₃)]_n, is a novel carboxyl­ate-bridged one-dimensional helical copper(II) polymer. The metal ion exhibits an approximately square-pyramidal CuBrNO₃ coordination environment, with the three donor atoms of the ligand and the bromide ion occupying the basal positions, and an O atom belonging to the carboxyl­ate group of an adjacent mol­ecule in the apical site. Carboxyl­ate groups are mutually cis oriented, and each anti–anti carboxyl­ate group bridges two copper(II) ions via one apical and one basal position [Cu...Cu = 5.677 (1) Å], resulting in the formation of a helical chain along the crystallographic b axis.

S1. Comment

Self-assembly of supramolecules with helical structures by simple mixing of ligands and metal ions has been one of the targets of supermolecular chemistry (Piguet et al., 1997), because helicity is an essential element of life and is also important in advanced materials, such as optical devices and asymmetric catalysis (Albrecht, 2001; Erxleben, 2001; Jung et al., 2000; Plasseraud et al., 2001). It is well known that a carboxylate group can bridge two metal ions to give rise to a wide variety of polynuclear complexes, ranging from discrete entities to three-dimensional systems (Rettig et al., 1999; Tangoluis et al., 1996). In these complexes, a carboxylate group can assume many types of bridging conformations, the most important being triatomic syn–syn, anti–anti and syn–anti, and monatomic (Kato et al., 1988; Colacio et al., 1999; Dey et al., 2003; Yang et al., 2003; see Scheme 2).

In our efforts to investigate the bonding nature of carboxylate-bridged copper(II) complexes, we succeeded in obtaining a new single-stranded helical coordination polymer, (I), by reacting 8-quinolinyloxyacetic acid with copper(II) bromide. Although a few similar helical chains with carboxylate-containing ligand have been reported by other authors (Colacio et al., 1992; Colacio et al., 2000; Yang et al., 2003), to our knowledge, the title complex is the first helical carboxylate-bridged copper(II) polymer containing an aryloxyacetate ligand.

Complex (I) has a one-dimensional helical chain structure, which results from the fact that the copper(II) ions are bridged sequentially by anti–anti carboxylate groups (see below). A perspective view of the mononuclear fragment of (I) is given in Fig. 1, a view of the helical chain is shown in Fig. 2, and selected bond lengths and angles are listed in Table 1. Within the coordination sphere, four bonds are formed in the basal plane with one N atom [Cu—N1 = 1.978 (5) Å], two O atoms [Cu—O1 = 2.017 (4) Å and Cu—O3 = 1.936 (4) Å] from one oxyacetate ligand and one bromide anion [Cu—Br = 2.3290 (12) Å], while the other O atom, forming a bridge between two Cu atoms, is at the axial position and is coordinated at a longer distance [Cu—O2A = 2.294 (4) Å; the suffix A indicates the symmetry position (-x, y − 1/2, 1/2 − z)]. The inequivalence of the carboxylate C—O distances O3—C11 [1.290 (7) Å] and O2—C11 [1.206 (7) Å] may be correlated with their involvement in bonding with the Cu atoms. The other bond lengths and angles associated with the ligand and the Br⁻ ion are as expected.

The coordination geometry around the Cu atom may be described as a distorted square pyramid, the basal plane being defined by atoms N1, O1, O3 and Br, and the apical position being occupied by atom O2A from the carboxylate group of a neighbouring complex. Atoms N1, O1, O3 and Br show deviations of 0.0502 (1), −0.0633 (1), 0.0534 (1) and −0.0403 (1) Å, respectively, from the least-squares mean plane through these atoms, indicating a tetrahedral distortion from planarity. As expected,the Cu atom is displaced from this plane by 0.1253 (1) Å toward the apical O2A atom. Each monodeprotonated ligand is tridentate with respect to one Cu centre but is, in fact, tetradentate when the bridge to atom O2A is considered. Two five-membered chelate rings are formed with the metal atoms, producing considerable distortions in the chelate rings; the N1—Cu—O1 and O1—Cu—O3 chelate angles are 81.31 (19) and 79.32 (17)°, respectively. The five-membered chelate ring defined by atoms Cu, N1, C9, C8 and O1 is significantly non-planar [maximum atomic displacement −0.1069 (1) Å], while the five-membered chelate ring defined by atoms Cu, O1, C10, C11 and O3 has a maximum atomic displacement of −0.1909 (1) Å. The two fused ring systems are also folded along the common Cu—O1 axis by 10.3 (1)°.

As noted above, each carboxylate group is in an anti–anti conformation with respect to the two copper centres that it bridges via two of its O atoms. The copper ions deviate from the mean basal plane towards the axial O-atom donor. Because the three donor atoms of the ligands occupy the basal plane of the coordination sphere, the carboxylate bridges must be oriented in a mutually cis fashion and occupy basal and apical positions, with intrachain Cu···Cu distances of 5.677 (1) Å. Interestingly, both the cis orientations of the anti–anti carboxylate groups and the shifts of the copper(II) ions from the carboxylate mean planes contribute to helicity in the chains. The helix is generated by the operation of a 2₁ screw axis parallel to the b axis.

S2. Experimental

##AUTHOR: Please confirm changes below.

The ligand 8-quinolinyloxyacetic acid was prepared by a general procedure reported by Koelsch (1931). The title complex was prepared by stirring together a solution of 8-quinolinyloxyacetic acid (0.0203 g, 0.1 mmol) in methanol (20 ml) and an aqueous solution (2 ml) of CuBr₂·2H₂O (0.027 g, 0.1 mmol) for 6 h. A solution of NaOH (0.004 g, 0.1 mmol) in methanol (10 ml) was then added. The resulting green solution was stirred for about 6 h at room temperature and then filtered. Slow evaporation from the filtrate yielded square prismatic green crystals suitable for X-ray analysis. Analysis found: C 38.69, H 2.11, N 4.07%; calculated for C₁₁H₈BrCuNO₃: C 38.22, H 2.33, N 4.00%.

S3. Refinement

H atoms were included in calculated positions and refined in the riding-model approximation, with C—H distances of 0.95 and 0.99 Å, and U_iso(H) values of 1.2U_eq(C).

Computing details

Data collection: CrystalClear (Molecular Structure Corporation, 2000; Rigaku Corporation, 1999 ); cell refinement: CrystalClear; data reduction: CrystalStructure (Rigaku/MSC and Rigaku Corporation, 2000–2003); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker,1998); software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. An ellipsoid plot of the mononuclear fragment of (I); atom O2A is at symmetry position (-x, y − 1/2, 1/2 − z). Displacement ellipsoids are drawn at the 30% probability level.
	Fig. 2. A view of the helical polymeric chain propagated along the crystallographic b axis.

(I)

Crystal data

[CuBr(C11H8NO3)]	F(000) = 676
Mr = 345.63	Dx = 2.109 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 3148 reflections
a = 9.733 (5) Å	θ = 3.0–27.5°
b = 6.725 (3) Å	µ = 5.67 mm^−1
c = 17.066 (9) Å	T = 193 K
β = 102.922 (8)°	Square prism, green
V = 1088.8 (9) Å^3	0.40 × 0.20 × 0.15 mm
Z = 4

Data collection

Rigaku Mercury CCD area-detector diffractometer	2490 independent reflections
Radiation source: fine-focus sealed tube	2326 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.040
Detector resolution: 7.31 pixels mm^-1	θmax = 27.5°, θmin = 3.7°
ω scans	h = −12→12
Absorption correction: multi-scan (Jacobson, 1998)	k = −8→8
Tmin = 0.210, Tmax = 0.484	l = −18→22
8275 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.063	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.154	H-atom parameters constrained
S = 1.14	w = 1/[σ^2(Fo^2) + (0.057P)^2 + 11.343P] where P = (Fo^2 + 2Fc^2)/3
2490 reflections	(Δ/σ)max < 0.001
154 parameters	Δρmax = 1.38 e Å^−3
0 restraints	Δρmin = −1.46 e Å^−3

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. A short description of program CrystalClear: This software was developed by Rigaku/Molecular Structure Corporation and is based on Jim Pflugrath's D*TREK data processing software but the front end runs under Windows NT platform. This software is used to collect data from the R-Axis IIc Image Plate (IP) detector. It utilizesa more graphical user interface (GUI) for both input and output.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Br	−0.13278 (7)	−0.26227 (11)	0.06619 (4)	0.0325 (2)
Cu	0.02403 (7)	−0.00976 (11)	0.11973 (4)	0.0150 (2)
O1	0.1444 (4)	0.2347 (6)	0.1493 (2)	0.0165 (8)
O2	−0.1146 (4)	0.3886 (7)	0.2507 (2)	0.0187 (9)
O3	−0.1076 (4)	0.1650 (6)	0.1555 (3)	0.0186 (9)
N1	0.1962 (5)	−0.1039 (8)	0.0879 (3)	0.0167 (10)
C1	0.2157 (7)	−0.2693 (10)	0.0492 (4)	0.0230 (13)
H1	0.1379	−0.3552	0.0301	0.028*
C2	0.3491 (8)	−0.3207 (11)	0.0358 (5)	0.0297 (15)
H2	0.3591	−0.4373	0.0062	0.036*
C3	0.4628 (7)	−0.2051 (11)	0.0648 (4)	0.0282 (15)
H3	0.5531	−0.2439	0.0578	0.034*
C4	0.4470 (6)	−0.0252 (10)	0.1057 (4)	0.0211 (13)
C5	0.5578 (6)	0.1099 (12)	0.1375 (4)	0.0268 (15)
H5	0.6508	0.0824	0.1319	0.032*
C6	0.5318 (7)	0.2773 (11)	0.1757 (4)	0.0252 (14)
H6	0.6077	0.3635	0.1981	0.030*
C7	0.3923 (6)	0.3275 (10)	0.1832 (4)	0.0224 (13)
H7	0.3747	0.4467	0.2092	0.027*
C8	0.2860 (6)	0.2002 (9)	0.1521 (3)	0.0163 (11)
C9	0.3100 (6)	0.0210 (9)	0.1150 (3)	0.0160 (11)
C10	0.1023 (6)	0.3534 (9)	0.2097 (4)	0.0158 (11)
H10A	0.1139	0.4965	0.1993	0.019*
H10B	0.1602	0.3206	0.2636	0.019*
C11	−0.0554 (5)	0.3044 (9)	0.2052 (3)	0.0128 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br	0.0283 (4)	0.0320 (4)	0.0346 (4)	−0.0049 (3)	0.0017 (3)	−0.0078 (3)
Cu	0.0114 (3)	0.0159 (4)	0.0172 (4)	−0.0006 (3)	0.0024 (2)	−0.0029 (3)
O1	0.0142 (18)	0.017 (2)	0.018 (2)	−0.0011 (16)	0.0047 (15)	−0.0063 (17)
O2	0.0139 (19)	0.026 (2)	0.015 (2)	0.0035 (17)	0.0026 (15)	−0.0042 (17)
O3	0.0115 (18)	0.017 (2)	0.026 (2)	−0.0008 (16)	0.0019 (16)	−0.0038 (18)
N1	0.017 (2)	0.017 (2)	0.016 (2)	0.001 (2)	0.0037 (19)	0.001 (2)
C1	0.028 (3)	0.017 (3)	0.026 (3)	0.000 (3)	0.010 (3)	−0.006 (3)
C2	0.034 (4)	0.024 (3)	0.038 (4)	0.005 (3)	0.022 (3)	−0.002 (3)
C3	0.024 (3)	0.033 (4)	0.032 (4)	0.011 (3)	0.017 (3)	0.001 (3)
C4	0.018 (3)	0.027 (3)	0.021 (3)	0.005 (2)	0.008 (2)	0.005 (3)
C5	0.012 (3)	0.044 (4)	0.024 (3)	0.000 (3)	0.002 (2)	0.005 (3)
C6	0.015 (3)	0.037 (4)	0.023 (3)	−0.007 (3)	0.003 (2)	0.000 (3)
C7	0.017 (3)	0.028 (3)	0.023 (3)	−0.004 (2)	0.004 (2)	−0.003 (3)
C8	0.016 (3)	0.019 (3)	0.014 (3)	−0.003 (2)	0.004 (2)	0.002 (2)
C9	0.015 (3)	0.021 (3)	0.012 (2)	0.003 (2)	0.004 (2)	0.003 (2)
C10	0.015 (3)	0.015 (3)	0.019 (3)	−0.001 (2)	0.006 (2)	−0.005 (2)
C11	0.010 (2)	0.017 (3)	0.010 (2)	−0.003 (2)	−0.0005 (19)	0.001 (2)

Geometric parameters (Å, º)

Cu—Br	2.3290 (12)	C3—C4	1.422 (10)
Cu—N1	1.978 (5)	C3—H3	0.9500
Cu—O1	2.017 (4)	C4—C9	1.412 (8)
Cu—O2^i	2.294 (4)	C4—C5	1.421 (10)
Cu—O3	1.936 (4)	C5—C6	1.353 (10)
O1—C8	1.388 (7)	C5—H5	0.9500
O1—C10	1.434 (7)	C6—C7	1.432 (9)
O2—C11	1.206 (7)	C6—H6	0.9500
O3—C11	1.290 (7)	C7—C8	1.356 (9)
N1—C1	1.329 (8)	C7—H7	0.9500
N1—C9	1.384 (8)	C8—C9	1.406 (8)
C1—C2	1.411 (9)	C10—C11	1.554 (7)
C1—H1	0.9500	C10—H10A	0.9900
C2—C3	1.353 (11)	C10—H10B	0.9900
C2—H2	0.9500
O3—Cu—N1	160.5 (2)	C9—C4—C5	118.1 (6)
O3—Cu—O1	79.32 (17)	C9—C4—C3	116.8 (6)
N1—Cu—O1	81.31 (19)	C5—C4—C3	125.1 (6)
O3—Cu—O2^i	90.88 (17)	C6—C5—C4	120.5 (6)
N1—Cu—O2^i	90.17 (18)	C6—C5—H5	119.7
O1—Cu—O2^i	85.71 (16)	C4—C5—H5	119.7
O3—Cu—Br	98.31 (13)	C5—C6—C7	121.5 (6)
N1—Cu—Br	100.38 (15)	C5—C6—H6	119.3
O1—Cu—Br	170.34 (13)	C7—C6—H6	119.3
O2^i—Cu—Br	103.75 (11)	C8—C7—C6	118.1 (6)
C8—O1—C10	120.7 (4)	C8—C7—H7	120.9
C8—O1—Cu	112.9 (4)	C6—C7—H7	120.9
C10—O1—Cu	112.9 (3)	C7—C8—O1	124.9 (6)
C11—O2—Cu^ii	128.6 (4)	C7—C8—C9	121.9 (6)
C11—O3—Cu	117.2 (3)	O1—C8—C9	113.1 (5)
C1—N1—C9	118.8 (5)	N1—C9—C8	118.0 (5)
C1—N1—Cu	128.9 (4)	N1—C9—C4	122.3 (6)
C9—N1—Cu	112.2 (4)	C8—C9—C4	119.7 (6)
N1—C1—C2	121.6 (6)	O1—C10—C11	106.6 (4)
N1—C1—H1	119.2	O1—C10—H10A	110.4
C2—C1—H1	119.2	C11—C10—H10A	110.4
C3—C2—C1	120.5 (6)	O1—C10—H10B	110.4
C3—C2—H2	119.7	C11—C10—H10B	110.4
C1—C2—H2	119.7	H10A—C10—H10B	108.6
C2—C3—C4	119.9 (6)	O2—C11—O3	126.1 (5)
C2—C3—H3	120.0	O2—C11—C10	118.5 (5)
C4—C3—H3	120.0	O3—C11—C10	115.2 (5)
C9—N1—C1—C2	0.4 (9)	C1—N1—C9—C8	176.8 (6)
N1—C1—C2—C3	2.4 (11)	C1—N1—C9—C4	−2.5 (9)
C1—C2—C3—C4	−3.1 (11)	C7—C8—C9—N1	177.4 (6)
C2—C3—C4—C9	1.0 (10)	O1—C8—C9—N1	−5.7 (7)
C2—C3—C4—C5	−178.9 (7)	C7—C8—C9—C4	−3.3 (9)
C9—C4—C5—C6	0.2 (10)	O1—C8—C9—C4	173.6 (5)
C3—C4—C5—C6	−179.9 (7)	C5—C4—C9—N1	−178.3 (6)
C4—C5—C6—C7	−2.1 (10)	C3—C4—C9—N1	1.8 (9)
C5—C6—C7—C8	1.2 (10)	C5—C4—C9—C8	2.4 (9)
C6—C7—C8—O1	−175.1 (6)	C3—C4—C9—C8	−177.5 (6)
C6—C7—C8—C9	1.5 (9)	C8—O1—C10—C11	−161.7 (5)
C10—O1—C8—C7	−30.3 (9)	O1—C10—C11—O2	−179.5 (5)
C10—O1—C8—C9	152.9 (5)	O1—C10—C11—O3	4.9 (7)

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