In the title compound, [Cd(C
9H
6O
5)(C
10H
8N
2)(H
2O)]
n, the Cd
II atom is coordinated in a distorted octahedral fashion by two carboxylate groups (one in a monodentate and one in a bidentate fashion) from two 4-carboxylatophenoxyacetate anions, two N atoms from a 2,2'-bipyridine ligand and one aqua ligand. The structure is a helix with a long pitch of 16.441 (5) Å. A three-dimensional supramolecular network is further constructed through
-
stacking and hydrogen-bonding interactions between the helices.
Supporting information
CCDC reference: 600937
2,2'-Bipyridine (0.157 g, 1 mmol) and cadmium nitrate (0.308 g, 1 mmol) were
dissolved in a hot aqueous solution of 4-carboxyphenoxyacetic acid (0.196 g, 1 mmol) and the pH of the solution was adjusted to 6 with triethylamine. The
solution was sealed in a 15 ml Teflon-lined stainless steel bomb and held at
413 K for 96 h. The bomb was then cooled naturally to room temperature.
Colorless prismatic crystals were filtered off, washed with water and dried at
room temperature (yield 58%).
The water H atoms were located from difference Fourier maps and refined
freely. All other H atoms were positioned geometrically and refined with a
riding model, with distances 0.97 (CH2) or 0.93 (aromatic) Å, and with
Uiso(H) = 1.2 Ueq(C).
Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97.
catena-Poly[[aqua(2,2'-bipyridine-
κ2N,
N')cadmium(II)]-µ-4- carboxylatophenoxyacetato-
κ3O,
O':
O'']
top
Crystal data top
[Cd(C9H6O5)(C10H8N2)(H2O)] | F(000) = 960 |
Mr = 480.74 | Dx = 1.804 Mg m−3 |
OrthorhombicP212121 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 947 reflections |
a = 6.799 (2) Å | θ = 2.5–26.8° |
b = 15.834 (5) Å | µ = 1.28 mm−1 |
c = 16.441 (5) Å | T = 293 K |
V = 1769.9 (9) Å3 | Prism, colorless |
Z = 4 | 0.37 × 0.21 × 0.17 mm |
Data collection top
Bruker APEX area-detector diffractometer | 3866 independent reflections |
Radiation source: fine-focus sealed tube | 3417 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.028 |
φ and ω scans | θmax = 27.1°, θmin = 2.5° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −8→8 |
Tmin = 0.650, Tmax = 0.812 | k = −20→12 |
10675 measured reflections | l = −19→21 |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.026 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.050 | w = 1/[σ2(Fo2) + (0.0231P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.06 | (Δ/σ)max = 0.001 |
3866 reflections | Δρmax = 0.56 e Å−3 |
262 parameters | Δρmin = −0.27 e Å−3 |
0 restraints | Absolute structure: Flack (1983), 1617 Friedel pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.36 (2) |
Crystal data top
[Cd(C9H6O5)(C10H8N2)(H2O)] | V = 1769.9 (9) Å3 |
Mr = 480.74 | Z = 4 |
OrthorhombicP212121 | Mo Kα radiation |
a = 6.799 (2) Å | µ = 1.28 mm−1 |
b = 15.834 (5) Å | T = 293 K |
c = 16.441 (5) Å | 0.37 × 0.21 × 0.17 mm |
Data collection top
Bruker APEX area-detector diffractometer | 3866 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 3417 reflections with I > 2σ(I) |
Tmin = 0.650, Tmax = 0.812 | Rint = 0.028 |
10675 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.026 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.050 | Δρmax = 0.56 e Å−3 |
S = 1.06 | Δρmin = −0.27 e Å−3 |
3866 reflections | Absolute structure: Flack (1983), 1617 Friedel pairs |
262 parameters | Absolute structure parameter: 0.36 (2) |
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 | x | y | z | Uiso*/Ueq | |
Cd1 | 0.79697 (3) | 0.597549 (13) | 0.340650 (12) | 0.03146 (6) | |
O1 | 0.7358 (3) | 0.46184 (13) | 0.35751 (14) | 0.0454 (6) | |
O2 | 0.4563 (4) | 0.50229 (15) | 0.41487 (13) | 0.0492 (6) | |
O3 | 0.0214 (3) | 0.36815 (15) | 0.77036 (12) | 0.0426 (6) | |
O4 | −0.2507 (3) | 0.39258 (15) | 0.70274 (12) | 0.0424 (6) | |
O1W | 1.1313 (4) | 0.56505 (18) | 0.33104 (18) | 0.0469 (6) | |
H1A | 1.226 (6) | 0.597 (2) | 0.310 (2) | 0.064 (13)* | |
H1B | 1.194 (6) | 0.537 (2) | 0.358 (2) | 0.054 (13)* | |
N1 | 0.8241 (4) | 0.63920 (15) | 0.47599 (14) | 0.0360 (6) | |
N2 | 0.8478 (3) | 0.74367 (14) | 0.34756 (15) | 0.0330 (6) | |
C1 | 0.8248 (6) | 0.5843 (2) | 0.53766 (19) | 0.0506 (9) | |
H1 | 0.8146 | 0.5271 | 0.5258 | 0.061* | |
C2 | 0.8401 (5) | 0.6083 (3) | 0.61783 (19) | 0.0541 (10) | |
H2 | 0.8398 | 0.5685 | 0.6594 | 0.065* | |
C3 | 0.8556 (5) | 0.6928 (2) | 0.63458 (19) | 0.0530 (10) | |
H3 | 0.8648 | 0.7111 | 0.6882 | 0.064* | |
C4 | 0.8576 (5) | 0.7501 (2) | 0.57218 (18) | 0.0408 (8) | |
H4 | 0.8685 | 0.8076 | 0.5830 | 0.049* | |
C5 | 0.8433 (4) | 0.7215 (2) | 0.49240 (17) | 0.0327 (7) | |
C6 | 0.8474 (4) | 0.7801 (2) | 0.42158 (17) | 0.0321 (7) | |
C7 | 0.8513 (5) | 0.8670 (2) | 0.4300 (2) | 0.0485 (10) | |
H7 | 0.8475 | 0.8916 | 0.4813 | 0.058* | |
C8 | 0.8611 (6) | 0.9168 (2) | 0.3606 (2) | 0.0644 (12) | |
H8 | 0.8651 | 0.9753 | 0.3652 | 0.077* | |
C9 | 0.8647 (6) | 0.8797 (2) | 0.2862 (2) | 0.0601 (12) | |
H9 | 0.8728 | 0.9122 | 0.2392 | 0.072* | |
C10 | 0.8561 (5) | 0.7933 (2) | 0.2819 (2) | 0.0456 (9) | |
H10 | 0.8561 | 0.7680 | 0.2308 | 0.055* | |
C11 | 0.5668 (5) | 0.4486 (2) | 0.38684 (18) | 0.0322 (7) | |
C12 | 0.5068 (5) | 0.3567 (2) | 0.38631 (19) | 0.0359 (8) | |
H12A | 0.5417 | 0.3324 | 0.3341 | 0.043* | |
H12B | 0.5812 | 0.3270 | 0.4278 | 0.043* | |
O5 | 0.3036 (4) | 0.34298 (14) | 0.40022 (11) | 0.0410 (5) | |
C14 | 0.2279 (5) | 0.35086 (17) | 0.47679 (16) | 0.0297 (7) | |
C15 | 0.3360 (5) | 0.3502 (2) | 0.54816 (18) | 0.0397 (8) | |
H15 | 0.4722 | 0.3450 | 0.5467 | 0.048* | |
C16 | 0.2384 (4) | 0.35730 (19) | 0.62191 (17) | 0.0363 (8) | |
H16 | 0.3108 | 0.3564 | 0.6699 | 0.044* | |
C17 | 0.0369 (5) | 0.36572 (18) | 0.62600 (16) | 0.0289 (6) | |
C18 | −0.0660 (5) | 0.3652 (2) | 0.55345 (18) | 0.0383 (8) | |
H18 | −0.2022 | 0.3705 | 0.5545 | 0.046* | |
C19 | 0.0275 (5) | 0.3573 (2) | 0.48011 (19) | 0.0403 (8) | |
H19 | −0.0456 | 0.3562 | 0.4323 | 0.048* | |
C20 | −0.0700 (5) | 0.37613 (18) | 0.70540 (18) | 0.0316 (7) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Cd1 | 0.03449 (11) | 0.03069 (10) | 0.02921 (9) | 0.00025 (10) | −0.00330 (10) | −0.00314 (10) |
O1 | 0.0328 (15) | 0.0373 (12) | 0.0662 (15) | −0.0056 (9) | 0.0021 (10) | 0.0105 (11) |
O2 | 0.0561 (17) | 0.0392 (15) | 0.0524 (15) | 0.0083 (12) | 0.0002 (12) | −0.0029 (12) |
O3 | 0.0401 (14) | 0.0576 (16) | 0.0300 (12) | −0.0067 (11) | 0.0015 (10) | 0.0014 (10) |
O4 | 0.0367 (16) | 0.0557 (14) | 0.0347 (10) | 0.0067 (11) | 0.0093 (8) | 0.0055 (11) |
O1W | 0.0284 (13) | 0.0531 (15) | 0.0593 (16) | 0.0020 (12) | −0.0008 (13) | 0.0071 (13) |
N1 | 0.0435 (18) | 0.0360 (14) | 0.0285 (12) | −0.0020 (13) | −0.0005 (13) | −0.0011 (11) |
N2 | 0.0352 (16) | 0.0325 (12) | 0.0313 (12) | −0.0019 (10) | −0.0072 (12) | 0.0006 (11) |
C1 | 0.065 (3) | 0.046 (2) | 0.0416 (18) | −0.001 (2) | −0.0017 (17) | 0.0054 (15) |
C2 | 0.060 (3) | 0.067 (3) | 0.0351 (17) | −0.007 (2) | −0.0047 (15) | 0.0104 (18) |
C3 | 0.044 (2) | 0.084 (3) | 0.0317 (17) | −0.0041 (19) | −0.0006 (13) | −0.0084 (17) |
C4 | 0.036 (2) | 0.051 (2) | 0.0362 (17) | 0.0013 (15) | −0.0021 (13) | −0.0090 (15) |
C5 | 0.0239 (18) | 0.0404 (18) | 0.0337 (15) | −0.0011 (13) | −0.0018 (11) | −0.0076 (13) |
C6 | 0.0275 (19) | 0.0307 (16) | 0.0380 (16) | −0.0006 (12) | −0.0053 (12) | −0.0049 (13) |
C7 | 0.057 (3) | 0.0357 (19) | 0.053 (2) | 0.0014 (17) | −0.0136 (18) | −0.0110 (17) |
C8 | 0.084 (3) | 0.026 (2) | 0.083 (3) | −0.0039 (17) | −0.020 (2) | 0.0024 (18) |
C9 | 0.082 (3) | 0.038 (2) | 0.061 (2) | −0.0103 (18) | −0.024 (2) | 0.0173 (18) |
C10 | 0.053 (2) | 0.042 (2) | 0.0414 (18) | −0.0047 (17) | −0.0123 (15) | 0.0041 (16) |
C11 | 0.0327 (19) | 0.0320 (18) | 0.0318 (16) | 0.0018 (14) | −0.0082 (14) | 0.0029 (14) |
C12 | 0.0333 (19) | 0.040 (2) | 0.0342 (16) | −0.0025 (15) | 0.0083 (14) | −0.0041 (15) |
O5 | 0.0350 (12) | 0.0559 (14) | 0.0320 (10) | −0.0122 (13) | 0.0067 (11) | −0.0093 (9) |
C14 | 0.0296 (19) | 0.0304 (15) | 0.0292 (13) | −0.0069 (13) | 0.0050 (13) | −0.0029 (12) |
C15 | 0.026 (2) | 0.054 (2) | 0.0391 (17) | −0.0037 (15) | 0.0003 (13) | −0.0074 (15) |
C16 | 0.034 (2) | 0.0460 (19) | 0.0289 (14) | −0.0039 (14) | −0.0034 (13) | −0.0014 (13) |
C17 | 0.0333 (18) | 0.0228 (15) | 0.0307 (14) | −0.0023 (13) | 0.0018 (13) | 0.0022 (12) |
C18 | 0.0229 (18) | 0.053 (2) | 0.0394 (17) | 0.0033 (15) | −0.0004 (14) | 0.0041 (15) |
C19 | 0.038 (2) | 0.052 (2) | 0.0309 (15) | −0.0028 (16) | −0.0042 (14) | 0.0028 (16) |
C20 | 0.036 (2) | 0.0254 (16) | 0.0335 (16) | −0.0055 (13) | 0.0067 (14) | 0.0003 (12) |
Geometric parameters (Å, º) top
Cd1—O1 | 2.206 (2) | C5—C6 | 1.490 (4) |
Cd1—O4i | 2.295 (2) | C6—C7 | 1.383 (4) |
Cd1—N1 | 2.328 (2) | C7—C8 | 1.388 (5) |
Cd1—O1W | 2.336 (3) | C7—H7 | 0.9300 |
Cd1—N2 | 2.342 (2) | C8—C9 | 1.357 (6) |
Cd1—O3i | 2.513 (2) | C8—H8 | 0.9300 |
O1—C11 | 1.264 (4) | C9—C10 | 1.372 (5) |
O2—C11 | 1.225 (4) | C9—H9 | 0.9300 |
O3—C20 | 1.242 (4) | C10—H10 | 0.9300 |
O3—Cd1ii | 2.513 (2) | C11—C12 | 1.512 (4) |
O4—C20 | 1.256 (4) | C12—O5 | 1.417 (4) |
O4—Cd1ii | 2.295 (2) | C12—H12A | 0.9700 |
O1W—H1A | 0.89 (4) | C12—H12B | 0.9700 |
O1W—H1B | 0.76 (4) | O5—C14 | 1.366 (3) |
N1—C1 | 1.335 (4) | C14—C19 | 1.367 (4) |
N1—C5 | 1.336 (4) | C14—C15 | 1.384 (4) |
N2—C10 | 1.337 (4) | C15—C16 | 1.387 (4) |
N2—C6 | 1.347 (4) | C15—H15 | 0.9300 |
C1—C2 | 1.376 (5) | C16—C17 | 1.378 (5) |
C1—H1 | 0.9300 | C16—H16 | 0.9300 |
C2—C3 | 1.369 (5) | C17—C18 | 1.383 (4) |
C2—H2 | 0.9300 | C17—C20 | 1.503 (4) |
C3—C4 | 1.370 (5) | C18—C19 | 1.369 (4) |
C3—H3 | 0.9300 | C18—H18 | 0.9300 |
C4—C5 | 1.392 (4) | C19—H19 | 0.9300 |
C4—H4 | 0.9300 | C20—Cd1ii | 2.739 (3) |
| | | |
O1—Cd1—O4i | 99.5 (1) | C6—C7—H7 | 120.5 |
O1—Cd1—N1 | 99.8 (1) | C8—C7—H7 | 120.5 |
O4i—Cd1—N1 | 159.4 (1) | C9—C8—C7 | 119.7 (3) |
O1—Cd1—O1W | 88.7 (1) | C9—C8—H8 | 120.1 |
O4i—Cd1—O1W | 94.7 (1) | C7—C8—H8 | 120.1 |
N1—Cd1—O1W | 92.86 (10) | C8—C9—C10 | 118.5 (3) |
O1—Cd1—N2 | 169.70 (9) | C8—C9—H9 | 120.7 |
O4i—Cd1—N2 | 90.05 (8) | C10—C9—H9 | 120.7 |
N1—Cd1—N2 | 70.25 (9) | N2—C10—C9 | 123.1 (3) |
O1W—Cd1—N2 | 94.43 (9) | N2—C10—H10 | 118.5 |
O1—Cd1—O3i | 96.09 (8) | C9—C10—H10 | 118.5 |
O4i—Cd1—O3i | 54.03 (7) | O2—C11—O1 | 125.9 (3) |
N1—Cd1—O3i | 116.52 (9) | O2—C11—C12 | 120.4 (3) |
O1W—Cd1—O3i | 148.72 (9) | O1—C11—C12 | 113.8 (3) |
N2—Cd1—O3i | 86.33 (8) | O5—C12—C11 | 114.2 (3) |
C11—O1—Cd1 | 112.4 (2) | O5—C12—H12A | 108.7 |
C20—O3—Cd1ii | 86.72 (19) | C11—C12—H12A | 108.7 |
C20—O4—Cd1ii | 96.54 (18) | O5—C12—H12B | 108.7 |
Cd1—O1W—H1A | 127 (2) | C11—C12—H12B | 108.7 |
Cd1—O1W—H1B | 130 (3) | H12A—C12—H12B | 107.6 |
H1A—O1W—H1B | 99 (4) | C14—O5—C12 | 120.1 (2) |
C1—N1—C5 | 118.7 (3) | O5—C14—C19 | 114.8 (3) |
C1—N1—Cd1 | 122.8 (2) | O5—C14—C15 | 125.5 (3) |
C5—N1—Cd1 | 118.47 (19) | C19—C14—C15 | 119.7 (3) |
C10—N2—C6 | 118.6 (3) | C14—C15—C16 | 119.1 (3) |
C10—N2—Cd1 | 123.2 (2) | C14—C15—H15 | 120.4 |
C6—N2—Cd1 | 117.82 (19) | C16—C15—H15 | 120.4 |
N1—C1—C2 | 123.2 (3) | C17—C16—C15 | 121.7 (3) |
N1—C1—H1 | 118.4 | C17—C16—H16 | 119.1 |
C2—C1—H1 | 118.4 | C15—C16—H16 | 119.1 |
C3—C2—C1 | 117.9 (3) | C16—C17—C18 | 117.4 (3) |
C3—C2—H2 | 121.0 | C16—C17—C20 | 122.3 (3) |
C1—C2—H2 | 121.0 | C18—C17—C20 | 120.3 (3) |
C2—C3—C4 | 119.8 (3) | C19—C18—C17 | 121.7 (3) |
C2—C3—H3 | 120.1 | C19—C18—H18 | 119.1 |
C4—C3—H3 | 120.1 | C17—C18—H18 | 119.1 |
C3—C4—C5 | 119.3 (3) | C14—C19—C18 | 120.3 (3) |
C3—C4—H4 | 120.4 | C14—C19—H19 | 119.8 |
C5—C4—H4 | 120.4 | C18—C19—H19 | 119.8 |
N1—C5—C4 | 121.0 (3) | O3—C20—O4 | 122.7 (3) |
N1—C5—C6 | 116.8 (2) | O3—C20—C17 | 119.6 (3) |
C4—C5—C6 | 122.2 (3) | O4—C20—C17 | 117.7 (3) |
N2—C6—C7 | 121.1 (3) | O3—C20—Cd1ii | 66.36 (16) |
N2—C6—C5 | 116.1 (3) | O4—C20—Cd1ii | 56.35 (15) |
C7—C6—C5 | 122.8 (3) | C17—C20—Cd1ii | 173.9 (2) |
C6—C7—C8 | 119.0 (3) | | |
Symmetry codes: (i) −x+1/2, −y+1, z−1/2; (ii) −x+1/2, −y+1, z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H1A···O3iii | 0.89 (4) | 1.92 (4) | 2.773 (3) | 161 (3) |
O1W—H1B···O2iv | 0.76 (4) | 2.09 (4) | 2.787 (4) | 154 (4) |
Symmetry codes: (iii) −x+3/2, −y+1, z−1/2; (iv) x+1, y, z. |
Experimental details
Crystal data |
Chemical formula | [Cd(C9H6O5)(C10H8N2)(H2O)] |
Mr | 480.74 |
Crystal system, space group | OrthorhombicP212121 |
Temperature (K) | 293 |
a, b, c (Å) | 6.799 (2), 15.834 (5), 16.441 (5) |
V (Å3) | 1769.9 (9) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 1.28 |
Crystal size (mm) | 0.37 × 0.21 × 0.17 |
|
Data collection |
Diffractometer | Bruker APEX area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.650, 0.812 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 10675, 3866, 3417 |
Rint | 0.028 |
(sin θ/λ)max (Å−1) | 0.641 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.026, 0.050, 1.06 |
No. of reflections | 3866 |
No. of parameters | 262 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.56, −0.27 |
Absolute structure | Flack (1983), 1617 Friedel pairs |
Absolute structure parameter | 0.36 (2) |
Selected geometric parameters (Å, º) topCd1—O1 | 2.206 (2) | Cd1—O1W | 2.336 (3) |
Cd1—O4i | 2.295 (2) | Cd1—N2 | 2.342 (2) |
Cd1—N1 | 2.328 (2) | Cd1—O3i | 2.513 (2) |
| | | |
O1—Cd1—O4i | 99.5 (1) | N1—Cd1—N2 | 70.25 (9) |
O1—Cd1—N1 | 99.8 (1) | O1W—Cd1—N2 | 94.43 (9) |
O4i—Cd1—N1 | 159.4 (1) | O1—Cd1—O3i | 96.09 (8) |
O1—Cd1—O1W | 88.7 (1) | O4i—Cd1—O3i | 54.03 (7) |
O4i—Cd1—O1W | 94.7 (1) | N1—Cd1—O3i | 116.52 (9) |
N1—Cd1—O1W | 92.86 (10) | O1W—Cd1—O3i | 148.72 (9) |
O1—Cd1—N2 | 169.70 (9) | N2—Cd1—O3i | 86.33 (8) |
O4i—Cd1—N2 | 90.05 (8) | | |
Symmetry code: (i) −x+1/2, −y+1, z−1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H1A···O3ii | 0.89 (4) | 1.92 (4) | 2.773 (3) | 161 (3) |
O1W—H1B···O2iii | 0.76 (4) | 2.09 (4) | 2.787 (4) | 154 (4) |
Symmetry codes: (ii) −x+3/2, −y+1, z−1/2; (iii) x+1, y, z. |
It has been noted that employment of flexible or V-shaped exo-bidentate organic bridges can improve the helicity of polymeric chains (Ye et al., 2005). Therefore, we assumed that the 4-carboxylatophenoxyacetate (cpoa2-) anion, as a multidentate ligand with two different carboxylate groups, one at a flexible site, may be useful in the formation of single-stranded helical chains in the presence of aromatic chelate ligands, such as 2,2'-bipyridine (2,2'-bipy) and 1,10-phenanthroline (phen). These aromatic chelate ligands are important in maintaining the one-dimensionality and may provide potential supramolecular recognition sites for π–π stacking interaction (Chen et al., 2002; Zhang et al., 2004) to form multi-stranded helices. Using 4-carboxyphenoxyacetic acid (H2cpoa) and 2,2'-bipy, we have hydrothermally prepared the title compound, (I), namely [Cd(cpoa)(2,2'-bipy)(H2O)]n, which is a new neutral infinite CdII dicarboxylate helical coordination polymer. The structure is reported in this paper.
The asymmetric unit of (I) contains one CdII atom, one cpoa2- ligand, one 2,2'-bipy ligand and one water molecule (Fig. 1). The Cd atom is coordinated by three O atoms from one monodentate and one 1,3-bidentate cpoa ligands, the aqua ligand and two N atoms from the 2,2'-bipy ligand to furnish a distorted octahedral geometry. The Cd1—O3i and Cd1—O4i bond distances are longer than the Cd1—O1 bond (see Table 1 for distances and symmetry codes). Each pair of adjacent CdII atoms are bridged by cpoa2- ligands to form a chiral helical chain running along the 21 axis in the c direction with a pitch of 16.441 (5) Å; this is longer than the pitch of 11.25 (1) Å in [Cu(ipa)(2,2'-bipy)]n.2nH2O (H2ipa is isophthalic acid; Chen et al., 2002) because the cpoa2- dianion is larger than the ipa2- dianion. These chains are decorated with 2,2'-bipy ligands, positioned alternately on two sides and pointing in outwards, as depicted in Fig. 2. The benzene rings of the cpoa2- ions at each side of the helix are arranged in a parallel fashion, with a vertical inter-ring distance of 5.04 (1) Å; adjacent chiral helices are connected into a two-dimensional network through hydrogen bonds involving aqua ligands (Table 2 and Fig. 3). The two-dimensional network is extended into a three-dimensional supramolecular network by π–π stacking through intercalation of the 2,2'-bipy rings (the face-to-face distance is 3.42 (1) Å; Fig. 4)