A novel two-dimensional Cd^II coordination polymer: poly[aqua­[μ₄-2-(4-carboxylatobenzoyl)benzoato]cadmium(II)]

The title Cd^II coordination framework, [Cd(C₁₅H₈O₅)(H₂O)]_n or [Cd(bpdc)(H₂O)]_n [H₂bpdc is 2-(4-carboxybenzoyl)benzoic acid], has been prepared and characterized using IR spectroscopy, elemental analysis, thermal analysis and single-crystal X-ray diffraction. Each Cd^II centre is six-coordinated by two O atoms from one 2-(4-carboxylatobenzoyl)benzoate (bpdc²⁻) ligand in chelating mode, three O-donor atoms from three other bpdc²⁻ anions and one O atom from a coordinated water mol­ecule in an octa­hedral coordination environment. Two crystallographically equivalent Cd^II cations are bridged by one O atom of the 2-carboxyl­ate group of one bpdc²⁻ ligand and by both O atoms of the 4-carboxyl­ate group of a second bpdc²⁻ ligand to form a binuclear [(Cd)₂(O)(OCO)] secondary building unit. Adjacent secondary building units are inter­linked to form a one-dimensional [Cd(OCO)₂]_n chain. The bpdc²⁻ ligands link these rod-shaped chains to give rise to a complex two-dimensional [Cd(bpdc)]_n framework with a 4,4-connected binodal net topology of point symbol {4³.6².8}. The compound exhibits a strong fluorescence emission and typical ferroelectric behaviour in the solid state at room temperature.

S1. Introduction

During the past decade coordination polymers have attracted great inter­est, not only owing to their intriguing variety of topologies but also because of their potential applications in many fields, such as ion-exchange media, heterogeneous catalysts, optical devices, molecular magnets and gas-storage devices (Du et al., 2013; Li et al., 2010; Luo et al., 2010; Ma et al., 2009; Su et al., 2010). Generally, the assembly of coordination polymers is mainly affected by the combination of a few factors including temperature, the neutral ligands, the organic anions and the metal atoms (Cook et al., 2013; Almeida Paz et al., 2012). Among these factors, great effort has been devoted to the design of suitable organic ligands to construct new coordination polymers.

Organic ligands that contain carb­oxy­lic groups are frequently used for coordination polymers since the carboxyl­ate group has an excellent coordination capability and flexible coordination patterns, which result in a large diversity of structures. Benzo­phenone-2,4'-di­carb­oxy­lic acid (H₂bpdc), an asymmetrically V-shaped aromatic polycarb­oxy­lic acid derivative, has been used as a bridging ligand in the synthesis of novel coordination polymers (Chen et al., 2012; Hu et al., 2011, 2009; Xu et al., 2012). Taking inspiration from the points mentioned above, we explored the self-assembly of the Cd^II cation and H₂bpdc under hydro­thermal conditions, and obtained a novel two-dimensional coordination polymer, [Cd(bpdc)·H₂O]_n, (I), and we now report its synthesis, crystal structure and physical properties.

S2. Experimental

All chemicals used in the experiment were purchased from commercial sources (Sigma–Aldrich) and used without further purification. The C and H elemental analysis was performed on a Vario EL III elemental analyser (Elementar Analysensysteme GmbH). The IR spectrum was recorded from a KBr pellet in the range 4000–400 cm^-1 on a VECTOR 22 spectrometer (Bruker). The fluorescence spectrum was recorded on a Fluoro Max-P spectrophotometer (Perkin–Elmer). Thermogravimetric analysis was performed on a Perkin–Elmer Pyris 1 TGA analyser from 298 to 1123 K with a heating rate of 20 K min^-1 under nitro­gen (TA Instruments). The electric hysteresis loop was measured with a Premier II ferroelectric tester at room temperature (Radiant Technology Inc.).

S2.1. Synthesis and crystallization

A mixture of Cd(NO₃)₂·6H₂O (0.0346 g, 0.1 mmol), H₂bpdc (0.0271 g, 0.1 mmol) and KOH (0.0112 g, 0.2 mmol) in H₂O (10 ml) was sealed in a 16 ml Teflon-lined stainless steel container and heated at 493 K for 72 h. After cooling to room temperature, colourless block crystals of (I) were collected by filtration and washed in water and ethanol several times (yield 22.9%, based on H₂bpdc). Elemental analysis for C₁₅H₁₀CdO₆ (M_r = 398.63): C 45.19, H 2.53; found: C 45.28, H 2.54. IR (KBr, ν, cm^-1) : 3439 (m), 3057 (m), 1661 (s), 1578 (s), 1424 (vs), 1274 (s), 1234 (s), 841 (s), 771 (s), 722 (s).

S2.2. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. C-bound H atoms were placed in calculated positions and treated using a riding-model approximation, with C—H = 0.93 Å (aromatic) and with U_iso(H) = 1.2U_eq(C). Water H atoms were located in a difference Fourier map and refined with U_iso(H) = 1.2U_eq(O) and with the O—H distance restrained to 0.85 (2) Å.

S3. Results and discussion

X-ray crystallography reveals that the asymmetric unit of (I) consists of a divalent cadmium cation, one fully deprotonated bpdc ligand and one aqua ligand. As shown in Fig. 1, atom Cd1 is six-coordinated by two O atoms from one bpdc^2- ligand in a chelating mode, three O donor atoms from three individual bpdc anions and one O atom from a coordinated aqua molecule in an o­cta­hedral coordination environment (Table 2). The average of the Cd—O distances [2.31 (4) Å] is indeed comparable with those for other structures containing Cd^II (Wang et al., 2013; Wang, 2014).

In the bpdc^2- ligand in (I), the dihedral angle between the two benzene rings is 79.8 (2)° and the C5—C8—C9 angle is 118.6 (3)°. The dihedral angles between the carboxyl­ate groups at C1 and C15 and their adjacent benzene rings are 19.7 (3) and 17.5 (3)°, respectively. Each bpdc anion in (I) acts in a µ₄-mode (µ₂-η¹:η¹ and µ₂-η²:η¹), with one carboxyl­ate group bridging two Cd^II cations in a bis-monodentate mode and the other carboxyl­ate group bridging two other Cd^II cations in a briding mode. Two crystallographically equivalent Cd^II cations are bridged by one carboxyl­ate group (O4–C15–O5) and the carboxyl­ate group containing atoms O1, O2 and C1 to form a binuclear [(Cd1)₂(O1)(O4–C15–O5)] secondary building unit (SBU) with a Cd···Cd separation of 3.805 (2) Å. As shown in Fig 2, adjacent SBUs are inter­linked to form a one-dimensional [Cd(OCO)₂]_n chain extending along the c axis. The bpdc^2- ligands link these rod-shaped SBUs to give rise to a complicated two-dimensional [Cd(bpdc)]_n framework parallel to the (010) crystal plane (Fig 3).

The topology of this neutral [Cd(bpdc)]_n two-dimensional framework can be simplified by regarding both the Cd^II cations and the bpdc^2- ligands as 4-connected nodes. The resulting network thus has a 4,4-connected binodal net topology of point symbol {4³.6².8} (Fig. 4). To the best of our knowledge, this 4,4-connected binodal lattice has not yet been reported in coordination polymer chemistry.

Inter­layer inter­actions are fostered by weak O—H···O and C—H···O hydrogen bonds (see Table 3), constructing a three-dimensional supra­molecular architecture.

To test the thermal stability of (I), thermogravimetric analysis (TGA) was conducted. As shown in Fig. 5, the coordination water molecule was lost between 373 and 433 K (observed 3.98%, calculated 4.52%). The anhydrous substance was stable upon heating to 483 K. The decomposition of the organic ligand is observed between 483 and 1063 K, and the remaining weight corresponds to the formation of CdO (observed 32.03%, calculated 32.21%).

Due to the excellent fluorescence properties of d¹⁰ metal compounds, the solid-state photoluminescent properties of (I) were investigated at room temperature. The H₂bpdc ligand exhibits a broad weak fluorescent emission centred at 394 nm with an excitation maximum at 280 nm, which are probably attributed to π^*–n or π^*–π transitions, as previously reported (Xu et al., 2012). Compound (I) exhibits a relatively [strong? Text missing] emission band centred on ~410 nm upon excitation at 290 nm (Fig. 6). Because the Cd^II cation is difficult to oxidize or reduce, due to its d¹⁰ configuration, the emissive behaviour of (I) can be attributed to ligand-centred electronic transitions (Guo et al., 2011; Wen et al., 2007).

Since (I) crystallizes in the non-centrosymmetric space group Aba2, which belongs to one of the ten polar point groups, its ferroelectric features were investigated (Hang et al., 2011; Zhang & Xiong, 2012). Fig. 7 clearly indicates that (I) does indeed display ferroelectric behaviour, with a remnant polarization (P_r) of ca 0.67 µC cm^-2 and a coercive field (E_c) of 475.35 V cm^-1. The saturation value of the spontaneous polarization (P_s) is ~1.23 µC cm^-2.

Related literature

For related literature, see: Chen et al. (2012); Cook et al. (2013); Du et al. (2013); Guo et al. (2011); Hang et al. (2011); Hu et al. (2009, 2011); Li et al. (2010); Luo et al. (2010); Ma et al. (2009); Almeida Paz et al. (2012); Su et al. (2010); Wang (2014); Wang et al. (2013); Wen et al. (2007); Xu et al. (2012); Zhang & Xiong (2012).

Computing details

Data collection: SMART (Bruker 2000); cell refinement: SAINT (Bruker 2000); data reduction: SAINT (Bruker 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. A view of the local coordination of the Cd^II cations in (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. [Symmetry codes: (i) -x + 1/2, y, z - 1/2; (ii) x + 1/2, -y + 1, z - 1/2; (iii) -x, -y + 1, z - 1.]
	Fig. 2. A view of the infinite rod-shaped SBU in (I).
	Fig. 3. A view of the two-dimensional structure of (I).
	Fig. 4. A network perspective of the 4,4-connected binodal {4^3.6^2.8} point symbol in (I). The turquoise and black spheres represent the Cd atoms and bpdc^2- ligands, respectively.
	Fig. 5. The thermogravimetric plot for (I).
	Fig. 6. The solid-state emission spectrum of (I), recorded at room temperature.
	Fig. 7. The electric hysteresis loop for (I).

Poly[aqua[µ₄-2-(4-carboxylatobenzoyl)benwq3074zoato]cadmium(II)]

Crystal data

[Cd(C15H8O5)(H2O)]	Z = 8
Mr = 398.63	F(000) = 1568
Orthorhombic, Aba2	Dx = 1.953 Mg m^−3
Hall symbol: A 2 -2ac	Mo Kα radiation, λ = 0.71073 Å
a = 12.664 (6) Å	µ = 1.64 mm^−1
b = 30.334 (15) Å	T = 296 K
c = 7.060 (4) Å	Block, colourless
V = 2712 (2) Å^3	0.21 × 0.19 × 0.17 mm

Data collection

Bruker SMART CCD area-detector diffractometer	3061 independent reflections
Radiation source: fine-focus sealed tube	2511 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.034
ϕ and ω scans	θmax = 27.6°, θmin = 2.1°
Absorption correction: multi-scan SADABS (Bruker, 2000)	h = −8→16
Tmin = 0.725, Tmax = 0.768	k = −39→25
8238 measured reflections	l = −9→9

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)] = 0.028	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.055	w = 1/[σ^2(Fo^2) + (0.0207P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.99	(Δ/σ)max = 0.002
3061 reflections	Δρmax = 0.36 e Å^−3
205 parameters	Δρmin = −0.89 e Å^−3
3 restraints	Absolute structure: Flack (1983), with 1218 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.02 (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. 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
C1	0.1456 (3)	0.46675 (13)	0.3340 (5)	0.0247 (9)
C2	0.1314 (3)	0.50502 (15)	0.4667 (6)	0.0221 (10)
C3	0.1242 (4)	0.54738 (15)	0.3946 (7)	0.0293 (12)
H3	0.1260	0.5520	0.2644	0.035*
C4	0.1143 (4)	0.58270 (17)	0.5164 (6)	0.0286 (12)
H4	0.1118	0.6112	0.4675	0.034*
C5	0.1080 (4)	0.57638 (16)	0.7112 (6)	0.0233 (10)
C6	0.1151 (4)	0.53324 (15)	0.7841 (6)	0.0255 (11)
H6	0.1117	0.5285	0.9141	0.031*
C7	0.1269 (4)	0.49802 (16)	0.6622 (6)	0.0240 (11)
H7	0.1318	0.4695	0.7103	0.029*
C8	0.0973 (3)	0.61466 (13)	0.8439 (6)	0.0288 (9)
C9	0.0826 (3)	0.65986 (13)	0.7619 (5)	0.0275 (9)
C10	0.1692 (3)	0.68747 (16)	0.7589 (7)	0.0443 (12)
H10	0.2327	0.6782	0.8118	0.053*
C11	0.1619 (4)	0.72935 (16)	0.6764 (7)	0.0543 (14)
H11	0.2207	0.7477	0.6751	0.065*
C12	0.0700 (4)	0.74334 (12)	0.5987 (13)	0.0513 (11)
H12	0.0661	0.7710	0.5424	0.062*
C13	−0.0181 (3)	0.71616 (11)	0.6034 (9)	0.0367 (9)
H13	−0.0812	0.7259	0.5509	0.044*
C14	−0.0134 (3)	0.67491 (13)	0.6849 (5)	0.0262 (9)
C15	−0.1114 (3)	0.64644 (13)	0.6943 (5)	0.0274 (9)
Cd1	0.193946 (18)	0.400042 (7)	0.09130 (6)	0.02709 (7)
O1	0.1826 (2)	0.43005 (9)	0.3988 (4)	0.0327 (6)
O2	0.1235 (2)	0.47011 (9)	0.1631 (4)	0.0344 (7)
O3	0.1084 (3)	0.61025 (9)	1.0158 (4)	0.0460 (8)
O4	−0.1117 (2)	0.61486 (9)	0.8091 (4)	0.0369 (7)
O5	−0.1862 (2)	0.65611 (8)	0.5860 (10)	0.0484 (7)
O6	0.0677 (3)	0.35110 (12)	0.1977 (4)	0.0470 (8)
H6A	0.074 (4)	0.3446 (15)	0.312 (3)	0.056*
H6B	0.0031 (18)	0.3508 (16)	0.168 (6)	0.056*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.020 (2)	0.025 (2)	0.028 (2)	−0.0015 (16)	0.0025 (16)	−0.0026 (16)
C2	0.020 (2)	0.025 (3)	0.021 (2)	0.0005 (18)	0.0006 (17)	0.0037 (18)
C3	0.040 (3)	0.024 (3)	0.023 (2)	0.006 (2)	0.0028 (19)	0.0031 (19)
C4	0.039 (3)	0.019 (2)	0.027 (2)	0.000 (2)	0.0004 (18)	0.0010 (18)
C5	0.024 (2)	0.024 (3)	0.022 (2)	0.004 (2)	0.0022 (17)	−0.0033 (18)
C6	0.027 (2)	0.027 (3)	0.022 (2)	0.003 (2)	−0.0026 (18)	0.004 (2)
C7	0.031 (2)	0.018 (2)	0.0229 (19)	0.0073 (19)	−0.0050 (16)	−0.0007 (16)
C8	0.025 (2)	0.030 (2)	0.031 (2)	0.0004 (17)	−0.0027 (17)	0.0001 (17)
C9	0.033 (2)	0.025 (2)	0.0249 (19)	−0.0001 (19)	0.0022 (17)	−0.0073 (16)
C10	0.034 (3)	0.041 (3)	0.057 (3)	−0.006 (2)	−0.005 (2)	−0.010 (2)
C11	0.057 (3)	0.038 (3)	0.068 (3)	−0.020 (3)	0.016 (3)	−0.013 (2)
C12	0.079 (3)	0.027 (2)	0.048 (2)	−0.008 (2)	0.008 (4)	0.010 (4)
C13	0.054 (2)	0.0240 (19)	0.032 (2)	0.0026 (16)	−0.001 (3)	0.001 (3)
C14	0.036 (2)	0.023 (2)	0.0192 (18)	−0.0026 (17)	0.0028 (16)	−0.0013 (15)
C15	0.031 (2)	0.022 (2)	0.029 (2)	−0.0013 (18)	0.0039 (17)	−0.0063 (17)
Cd1	0.03306 (13)	0.02638 (13)	0.02184 (10)	−0.00207 (11)	−0.0006 (2)	−0.0039 (2)
O1	0.0399 (17)	0.0254 (16)	0.0328 (14)	0.0076 (13)	−0.0088 (13)	−0.0024 (12)
O2	0.0449 (18)	0.0328 (17)	0.0254 (13)	0.0077 (13)	0.0012 (12)	−0.0039 (11)
O3	0.071 (2)	0.042 (2)	0.0247 (13)	0.0157 (16)	−0.0099 (14)	−0.0031 (12)
O4	0.0443 (18)	0.0330 (17)	0.0334 (15)	−0.0036 (14)	0.0100 (13)	0.0001 (13)
O5	0.0400 (16)	0.0341 (15)	0.0711 (19)	0.0004 (12)	−0.016 (3)	−0.002 (3)
O6	0.060 (2)	0.049 (2)	0.0322 (17)	−0.0167 (18)	−0.0028 (16)	0.0080 (15)

Geometric parameters (Å, º)

C1—O2	1.243 (4)	C11—C12	1.354 (7)
C1—O1	1.291 (4)	C11—H11	0.9300
C1—C2	1.503 (6)	C12—C13	1.388 (5)
C2—C3	1.385 (6)	C12—H12	0.9300
C2—C7	1.398 (6)	C13—C14	1.378 (5)
C3—C4	1.379 (6)	C13—H13	0.9300
C3—H3	0.9300	C14—C15	1.514 (5)
C4—C5	1.391 (5)	C15—O5	1.253 (6)
C4—H4	0.9300	C15—O4	1.255 (5)
C5—C6	1.409 (6)	Cd1—O1^i	2.263 (3)
C5—C8	1.498 (6)	Cd1—O5^ii	2.281 (3)
C6—C7	1.380 (6)	Cd1—O4^iii	2.293 (3)
C6—H6	0.9300	Cd1—O6	2.307 (3)
C7—H7	0.9300	Cd1—O1	2.358 (3)
C8—O3	1.229 (5)	Cd1—O2	2.360 (3)
C8—C9	1.500 (5)	O1—Cd1^iv	2.263 (3)
C9—C10	1.380 (6)	O4—Cd1^v	2.293 (3)
C9—C14	1.409 (5)	O5—Cd1^vi	2.281 (3)
C10—C11	1.401 (7)	O6—H6A	0.836 (19)
C10—H10	0.9300	O6—H6B	0.845 (19)
O2—C1—O1	119.7 (3)	C13—C12—H12	120.2
O2—C1—C2	121.0 (4)	C14—C13—C12	121.0 (5)
O1—C1—C2	119.3 (3)	C14—C13—H13	119.5
C3—C2—C7	120.1 (5)	C12—C13—H13	119.5
C3—C2—C1	119.7 (4)	C13—C14—C9	119.5 (4)
C7—C2—C1	120.2 (4)	C13—C14—C15	120.1 (4)
C4—C3—C2	119.8 (5)	C9—C14—C15	120.4 (3)
C4—C3—H3	120.1	O5—C15—O4	124.8 (4)
C2—C3—H3	120.1	O5—C15—C14	117.4 (4)
C3—C4—C5	121.0 (5)	O4—C15—C14	117.8 (4)
C3—C4—H4	119.5	O1^i—Cd1—O5^ii	80.26 (14)
C5—C4—H4	119.5	O1^i—Cd1—O4^iii	82.62 (10)
C4—C5—C6	119.1 (5)	O5^ii—Cd1—O4^iii	98.09 (17)
C4—C5—C8	121.1 (5)	O1^i—Cd1—O6	158.91 (11)
C6—C5—C8	119.8 (4)	O5^ii—Cd1—O6	89.18 (13)
C7—C6—C5	119.9 (4)	O4^iii—Cd1—O6	80.86 (11)
C7—C6—H6	120.1	O1^i—Cd1—O1	116.10 (10)
C5—C6—H6	120.1	O5^ii—Cd1—O1	110.11 (18)
C6—C7—C2	120.2 (5)	O4^iii—Cd1—O1	147.99 (10)
C6—C7—H7	119.9	O6—Cd1—O1	84.63 (11)
C2—C7—H7	119.9	O1^i—Cd1—O2	91.61 (10)
O3—C8—C9	119.7 (4)	O5^ii—Cd1—O2	158.02 (13)
O3—C8—C5	121.5 (4)	O4^iii—Cd1—O2	101.09 (10)
C9—C8—C5	118.6 (3)	O6—Cd1—O2	104.34 (12)
C10—C9—C14	118.9 (4)	O1—Cd1—O2	55.37 (9)
C10—C9—C8	117.5 (4)	C1—O1—Cd1^iv	144.1 (2)
C14—C9—C8	123.5 (3)	C1—O1—Cd1	91.7 (2)
C9—C10—C11	120.3 (4)	Cd1^iv—O1—Cd1	110.81 (11)
C9—C10—H10	119.9	C1—O2—Cd1	92.8 (2)
C11—C10—H10	119.9	C15—O4—Cd1^v	135.5 (3)
C12—C11—C10	120.6 (4)	C15—O5—Cd1^vi	108.6 (3)
C12—C11—H11	119.7	Cd1—O6—H6A	114 (3)
C10—C11—H11	119.7	Cd1—O6—H6B	127 (3)
C11—C12—C13	119.7 (5)	H6A—O6—H6B	109 (4)
C11—C12—H12	120.2
O2—C1—C2—C3	−19.3 (6)	C10—C9—C14—C15	−177.0 (4)
O1—C1—C2—C3	159.9 (4)	C8—C9—C14—C15	4.6 (5)
O2—C1—C2—C7	161.5 (5)	C13—C14—C15—O5	18.1 (6)
O1—C1—C2—C7	−19.3 (7)	C9—C14—C15—O5	−163.0 (4)
C7—C2—C3—C4	1.1 (8)	C13—C14—C15—O4	−162.2 (4)
C1—C2—C3—C4	−178.1 (4)	C9—C14—C15—O4	16.7 (5)
C2—C3—C4—C5	−2.1 (9)	O2—C1—O1—Cd1^iv	136.6 (3)
C3—C4—C5—C6	1.9 (10)	C2—C1—O1—Cd1^iv	−42.6 (6)
C3—C4—C5—C8	−180.0 (4)	O2—C1—O1—Cd1	6.4 (4)
C4—C5—C6—C7	−0.7 (8)	C2—C1—O1—Cd1	−172.8 (3)
C8—C5—C6—C7	−178.8 (4)	O1^i—Cd1—O1—C1	68.99 (19)
C5—C6—C7—C2	−0.3 (8)	O5^ii—Cd1—O1—C1	157.8 (2)
C3—C2—C7—C6	0.1 (9)	O4^iii—Cd1—O1—C1	−51.9 (3)
C1—C2—C7—C6	179.3 (4)	O6—Cd1—O1—C1	−115.1 (2)
C4—C5—C8—O3	−168.3 (5)	O2—Cd1—O1—C1	−3.5 (2)
C6—C5—C8—O3	9.8 (7)	O1^i—Cd1—O1—Cd1^iv	−82.36 (19)
C4—C5—C8—C9	5.9 (7)	O5^ii—Cd1—O1—Cd1^iv	6.42 (15)
C6—C5—C8—C9	−175.9 (4)	O4^iii—Cd1—O1—Cd1^iv	156.72 (14)
O3—C8—C9—C10	72.0 (5)	O6—Cd1—O1—Cd1^iv	93.56 (14)
C5—C8—C9—C10	−102.4 (5)	O2—Cd1—O1—Cd1^iv	−154.89 (17)
O3—C8—C9—C14	−109.6 (5)	O1—C1—O2—Cd1	−6.4 (4)
C5—C8—C9—C14	76.1 (5)	C2—C1—O2—Cd1	172.8 (3)
C14—C9—C10—C11	−1.4 (6)	O1^i—Cd1—O2—C1	−117.3 (2)
C8—C9—C10—C11	177.1 (4)	O5^ii—Cd1—O2—C1	−49.8 (5)
C9—C10—C11—C12	0.0 (8)	O4^iii—Cd1—O2—C1	159.9 (2)
C10—C11—C12—C13	1.0 (10)	O6—Cd1—O2—C1	76.6 (3)
C11—C12—C13—C14	−0.5 (11)	O1—Cd1—O2—C1	3.7 (2)
C12—C13—C14—C9	−0.9 (8)	O5—C15—O4—Cd1^v	−72.4 (6)
C12—C13—C14—C15	177.9 (6)	C14—C15—O4—Cd1^v	107.9 (4)
C10—C9—C14—C13	1.9 (6)	O4—C15—O5—Cd1^vi	−10.9 (6)
C8—C9—C14—C13	−176.6 (4)	C14—C15—O5—Cd1^vi	168.8 (3)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O6—H6A···O5^vii	0.84 (2)	2.40 (3)	3.133 (8)	147 (4)
O6—H6B···O3^iii	0.85 (2)	2.13 (3)	2.828 (5)	139 (4)
C3—H3···O3^viii	0.93	2.50	3.290 (6)	143
C6—H6···O2^ix	0.93	2.50	3.292 (5)	143

Symmetry codes: (iii) −x, −y+1, z−1; (vii) −x, −y+1, z; (viii) x, y, z−1; (ix) x, y, z+1.