Lithium and sodium 3-(3,4-di­hydroxy­phen­yl)propenoate hydrate

The Li cation in the crystal structure of the lithium salt LiC₉H₇O₄·H₂O shows a coordination number of four whereas the Na cation in the crystal structure of the sodium salt NaC₉H₇O₄·H₂O shows a coordination number of seven.

Abstract

Treatment of 3-(3,4-di­hydroxy­phen­yl)propenoic acid (caffeic acid or 3,4-di­hydroxy­cinnamic acid) with the alkali hydroxides MOH (M = Li, Na) in aqueous solution led to the formation of poly[aqua­[μ-3-(3,4-di­hydroxy­phen­yl)propenoato]lithium], [Li(C₉H₇O₄)(H₂O)] _n , 1, and poly[aqua­[μ-3-(3,4-di­hydroxy­phen­yl)propenoato]sodium], [Na(C₉H₇O₄)(H₂O)] _n , 2. The crystal structure of 1 consists of a lithium cation that is coordinated nearly tetra­hedrally by three carboxyl­ate oxygen atoms and a water mol­ecule. The carboxyl­ate groups adopt a μ₃-κ³ O:O′:O′ coordination mode that leads to a chain-like catenation of Li cations and carboxyl­ate units parallel to the b axis. Moreover, the lithium carboxyl­ate chains are connected by hydrogen bonds between water mol­ecules attached to lithium and catechol OH groups. The crystal structure of 2 shows a sevenfold coordination of the sodium cation by one water mol­ecule, two monodentately binding carboxyl­ate groups and four oxygen atoms from two catechol groups. The coordination polyhedra are linked by face- and edge-sharing into chains extending parallel to the b axis. The chains are inter­linked by the bridging 3-(3,4-di­hydroxy­phen­yl)propenoate units and by inter­molecular hydrogen bonds to form the tri-periodic network.

1. Chemical context

trans-3-(3,4-Di­hydroxy­phen­yl)-2-propenoic acid (caffeic acid) is ubiquitous in plants and plays a role as an inter­mediate in the biosynthesis of lignin (Boerjan et al., 2003 ▸). The first X-ray crystal-structure analysis of caffeic acid dates back to the year 1987 (García-Granda et al., 1987 ▸), and a more recent study was published in 2015 (Kumar et al., 2015 ▸). In current research, caffeic acid is used as a co-crystallizing agent, particularly for pharmaceutically relevant compounds such as 5-fluoro­uracil (Yu et al., 2020 ▸). The simultaneous presence of the carboxyl and the catechol moieties renders caffeic acid a versatile ligand in coordination chemistry, in particular after deprot­on­ation of the acidic groups (Petrou et al., 1993 ▸). However, transition-metal complexes of caffeic acid derivatives have not yet been structurally investigated. Even for simple alkali metal caffeates, reports are rare and, up to now, only potassium caffeate has been studied in detail as the potassium caffeate/caffeic acid co-crystallization product (Lombardo et al., 2011 ▸).

Here we report the crystallization and crystal-structure analysis of the lithium and sodium salts of caffeic acid, LiC₉H₇O₄·H₂O, 1, and NaC₉H₇O₄·H₂O, 2, respectively.

2. Structural commentary

The asymmetric unit of 1 comprises one Li cation, one 3-(3,4-di­hydroxy­phen­yl)propenoate anion and one water mol­ecule (Fig. 1 ▸). The Li cation is coordinated nearly tetra­hedrally by three carboxyl­ate O atoms of three caffeate anions and one water mol­ecule. The Li—O distances range from 1.908 (2) to 2.005 (3) Å and the O—Li—O angles from 105.35 (12) to 112.20 (11)° (Table 1 ▸). These values are similar to those reported for other lithium carboxyl­ate compounds such as lithium acetate monohydrate [Li—O: 1.920 (2) to 2.031 (2) Å, O—Li—O: 99.78 (10) to 124.21 (11)°; Martínez Casado et al., 2011 ▸]. The carboxyl­ate group adopts a μ ₃-κ ³O:O′,O′ coordination mode. This leads to the formation of six-membered Li₂O₃C rings that are catenated parallel to the b axis by edge-sharing (Fig. 2 ▸). Alternatively, the chain structure can be derived from condensation of corner-sharing LiO₄ tetra­hedra (Fig. 3 ▸). The translational period of the 2₁-type helix corresponds to the length of the b axis and one repeating unit comprises two LiO₄ tetra­hedra. Chains of corner-sharing LiO₄ tetra­hedra are not unusual for lithium carboxyl­ate monohydrates, and similar patterns were observed for a lithium chloride glycine adduct (Müller et al., 1994 ▸) and lithium 2,4,6-tri­fluoro­benzoate hydrate (Lamann et al., 2012 ▸), which may serve as representative examples.

Figure 1.

Mol­ecular structure of the (3,4-di­hydroxy­phen­yl)propenoate anion in compound 1 along with the coordination sphere of the lithium cation. The asymmetric unit is displayed with filled bonds. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. Symmetry codes refer to Table 1 ▸.

Table 1. Selected geometric parameters (Å, °) for 1 .

C1—C2	1.4855 (18)	C7—O4	1.3781 (16)
C1—O1	1.2669 (16)	Li—O1i	1.949 (2)
C1—O2	1.2624 (16)	Li—O1ii	1.908 (2)
C2—C3	1.3285 (19)	Li—O2	1.962 (2)
C3—C4	1.4685 (18)	Li—O5	2.005 (3)
C6—O3	1.3757 (17)
O1—C1—C2	117.48 (12)	O1i—Li—O5	105.35 (12)
O1ii—Li—O1i	112.20 (11)	O1ii—Li—O5	109.92 (12)
O1i—Li—O2	108.08 (12)	O2—Li—O5	110.08 (11)
O1ii—Li—O2	111.04 (12)	Liiii—O1—Liiv	101.15 (8)

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) .

Figure 2.

Section of the crystal structure of 1 showing the six-membered Li₂O₃C rings.

Figure 3.

Section of the crystal structure of 1 showing the linkage of the LiO₄ tetra­hedra.

In the crystal structure of 2, the sodium cation adopts a sevenfold coordination from one water oxygen atom, two carboxyl­ate and four catechol oxygen atoms (Fig. 4 ▸). According to a SHAPE analysis (SHAPE 2.1; Llunell et al., 2013 ▸), the NaO₇ polyhedron is roughly related to the face-capped octa­hedron (CShM 2.807) and to the face-capped trigonal prism (CShM 3.593) with some preference to the former (Llunell et al., 2013 ▸; Pinsky & Avnir, 1998 ▸; Casanova et al., 2004 ▸; Cirera et al., 2005 ▸). Numerical data for this analysis are given in Table 2 ▸. The centre of Fig. 5 ▸ displays the observed NaO₇ polyhedron and the idealized CTRP-7 (left) and COC-7 (right) polyhedra in order to illustrate the degree of distortion. The Na—O distances are in the range from 2.3185 (14) to 2.7897 (17) Å (Table 3 ▸) and are comparable to those found in monosodium tartrate hydrate [2.3331 (12) to 2.6740 (12) Å], which also displays coordination number seven for the sodium cation (Al-Dajani et al., 2010 ▸). Generally, sodium carboxyl­ates with coordination number seven for the cation are rather rare. A search of the Cambridge Structural Database (CSD, version 2022.5.43; Groom et al., 2016 ▸) gave 20 matches. In this selection, the Na—O distances range from 2.299 to 3.017 Å with a median value of 2.44 Å (lower quartile: 2.380 Å, upper quartile: 2.557 Å). Regarding the coordination mode of the carboxyl­ate unit, the sodium salt 2 differs from the lithium salt 1 in the way that only one carboxyl­ate O atom (O2) is involved in coordination. Furthermore, the coordination mode of the catechol groups is also different in the two structures. In the case of 1, the catechol groups are part of the hydrogen-bonding network and there is no direct Li—O coordination from these groups. In contrast, the crystal structure of 2 reveals a direct coordination by the catechol oxygen atoms. Here, the catechol group acts as a chelating ligand and connects two sodium cations. The coordination mode can be described as μ-κ ⁴ O,O′:O,O′. Up to now, sodium compounds with chelating catechol groups have been observed only rarely. The CSD database search resulted in four structures with this coordination motif, e.g. in sodium quercetin-5′-sulfonate acetone solvate (Maciołek et al., 2022 ▸).

Figure 4.

Mol­ecular structure of the caffeate anion in compound 2 along with the coordination sphere of the sodium cation. The asymmetric unit is displayed with filled bonds. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. Symmetry codes refer to Table 2 ▸. Additional symmetry codes: (vii) −x + 1, −y, −z + 1; (viii) x, y − 1, z + 1; (ix) x, y, z − 1.

Table 2. Continuous shape measurement (CShM) values (SHAPE 2.1) for the seven-coordinate sodium ion of 2 .

Heptagon HP-7	32.482
Hexagonal pyramid HPY-7	20.852
Penta­gonal bipyramid PBPY-7	5.863
Capped octa­hedron COC-7	2.807
Capped trigonal prism CTPR-7	3.593
Johnson penta­gonal bipyramid JPBPY-7	8.482
Johnson elongated triangular pyramid JETPY-7	20.721

Figure 5.

Representation of the NaO₇ polyhedron in 2 (centre) and the best fitting regular polyhedra TRP-7 (left) and COC-7 (right).

Table 3. Selected geometric parameters (Å, °) for 2 .

C1—C2	1.481 (2)	Na—O2i	2.4608 (15)
C1—O2	1.252 (2)	Na—O2	2.3185 (14)
C1—O1	1.282 (2)	Na—O3ii	2.7897 (17)
C2—C3	1.327 (2)	Na—O3iii	2.7668 (16)
C3—C4	1.463 (2)	Na—O4iii	2.5810 (16)
C6—O3	1.3695 (19)	Na—O4ii	2.4153 (15)
C7—O4	1.3715 (19)	Na—O5	2.4411 (16)
O2—C1—C2	120.37 (14)	O2—Na—O4ii	175.93 (5)
O2—Na—O2i	84.95 (5)	O2—Na—O4iii	90.18 (5)
O2i—Na—O3ii	83.95 (5)	O2i—Na—O4iii	145.56 (5)
O2—Na—O3ii	118.94 (5)	O2—Na—O5	92.33 (5)
O2—Na—O3iii	112.69 (5)	Na—O2—Nai	95.05 (5)

Symmetry codes: (i) ; (ii) ; (iii) .

The NaO₇ polyhedra are linked by edge- (O2 and O2ⁱ) and face- (O3ⁱⁱⁱ, O4ⁱⁱⁱ, O3^iv, O4^iv) sharing to give chains propagating parallel to the b axis (Fig. 6 ▸). Additional inter­linking of these chains by μ ₄-bridging (3,4-di­hydroxy­phen­yl)propenoate units (Fig. 7 ▸) leads to layers extending parallel to the bc plane.

Figure 6.

Linkage of the NaO₇ polyhedra by edge- and face-sharing in the crystal structure of 2.

Figure 7.

Linkage of the NaO₇ polyhedral chains by (3,4-di­hydroxy­phen­yl)propenoate units in the crystal structure of 2.

In the structures of 1 and 2, the bond lengths and angles within the 3-(3,4-di­hydroxy­phen­yl)propenoate anions are very similar (Tables 1 ▸ and 3 ▸). The anions are nearly planar apart from a slight tilt [1: 6.3 (2)°, 2: 1.4 (2)°] of the carboxyl­ate group along the C1—C2 bond.

3. Supra­molecular features

The supra­molecular structure of lithium caffeate hydrate is governed by O—H⋯O hydrogen bonds (Table 4 ▸). Both hydrogen atoms H5A and H5B of the water mol­ecule are involved in hydrogen bonds to adjacent catechol groups (Fig. 8 ▸). H5B is part of a bifurcated hydrogen bond that connects the catechol oxygen atoms O3 and O4 with the water oxygen atom O5 (type a₁ and a₂ in Fig. 8 ▸). H5A forms a hydrogen bond to another neighbouring catechol oxygen atom O4 (type b). Moreover, the water oxygen atom O5 acts as an acceptor for the O4—H4 hydroxyl group of a further catechol unit in the surrounding (type c). An additional type of hydrogen bond is formed between the catechol group O3—H3 as the donor and the carboxyl­ate oxygen atom O2 as an acceptor (type d). The corresponding hydrogen bonds can be considered as medium-strong to weak, with the shortest O⋯O distance found for the d type [2.734 (2) Å] hydrogen bond and the largest for the bifurcated a₁ type hydrogen bond [3.042 (2) Å].

Table 4. Hydrogen-bond geometry (Å, °) for 1 .

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H3⋯O2v	0.92 (2)	1.83 (2)	2.734 (2)	168 (2)
O4—H4⋯O5vi	0.88 (2)	1.94 (2)	2.793 (2)	160.7 (2)
O5—H5A⋯O4vii	0.85 (3)	2.13 (2)	2.977 (2)	173 (2)
O5—H5B⋯O3viii	0.80 (2)	2.33 (2)	3.042 (2)	150 (2)
O5—H5B⋯O4viii	0.80 (2)	2.33 (2)	2.953 (2)	136 (2)

Symmetry codes: (v) ; (vi) ; (vii) ; (viii) .

Figure 8.

Hydrogen-bonding patterns in 1. Symmetry codes refer to Table 4 ▸. Additional symmetry codes: (x) −x + 2, −y, −z; (xi) x + 1, y, z; (xii) x - 2, −y, −z + 1.

Regarding the LiO₄ tetra­hedra chains, the hydrogen bonds are essential for intra-chain and inter-chain supra­molecular organization. Within a chain, directly adjacent LiO₄ tetra­hedra are linked pairwise (1,2 connection) by a sequence of hydrogen bonds of the type a₁ –d starting from O5 (Figs. 9 ▸, 10 ▸). Additionally, there is a c–b hydrogen-bonding sequence starting from O5 that links two LiO₄ tetra­hedra, which are separated by one LiO₄ unit (1,3 connection). The inter­connection of the LiO₄ tetra­hedra chains is based on two a₂-c hydrogen-bonding sequences starting from O5 or its centrosymmetric equivalent in the neighbouring chain. This leads to (24) motifs (Fig. 11 ▸).

Figure 9.

Inter­connection of the LiO₄ tetra­hedra chains of 1 by hydrogen bonds (dashed lines). Symmetry codes refer to Tables 1 ▸ and 4 ▸. Additional symmetry code: (xii) x − 2, −y, −z + 1.

Figure 10.

Position of the hydrogen bonds (dashed lines) along the LiO₄ tetra­hedra chains in the crystal structure of 1.

Figure 11.

Section of the crystal structure of 1 with the complete hydrogen-bonding network.

As in the case of 1, O—H⋯O hydrogen bonds are essential for the supra­molecular organisation within the crystal structure of 2 (Table 5 ▸). The water mol­ecule (H5A—O1—H5B) participates in two hydrogen bonds (Fig. 12 ▸). The hydrogen bond O5ⁱ—H5B ⁱ⋯O1 with the carboxyl­ate oxygen atom as an acceptor (equivalent to O5^xi—H5B ^xi ⋯O1^xii, type a in Fig. 12 ▸) acts as an intra-layer linkage, and the hydrogen bond O5^xi—H5A ^xi—O1 (equivalent to O5ⁱ—H5A ⁱ⋯O1^xii, type b in Fig. 12 ▸) connects adjacent layers (Fig. 13 ▸).

Table 5. Hydrogen-bond geometry (Å, °) for 2 .

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H3⋯O1iv	0.84 (2)	1.84 (2)	2.6437 (19)	158 (2)
O4—H4⋯O5v	0.81 (2)	1.85 (2)	2.6350 (19)	166 (2)
O5—H5A⋯O1vi	0.83 (2)	2.02 (2)	2.826 (2)	163 (2)
O5—H5B⋯O1i	0.82 (2)	1.95 (2)	2.7614 (19)	178 (3)

Symmetry codes: (i) ; (iv) ; (v) ; (vi) .

Figure 12.

Hydrogen-bonding patterns in the crystal structure of 2. Symmetry codes refer to Table 5 ▸.

Figure 13.

Inter-layer hydrogen bonds in 2. Symmetry codes refer to Table 5 ▸.

Fig. 14 ▸ represents the position of the intra-chain hydrogen bonds. Furthermore, the catechol groups are involved in hydrogen-bonding inter­actions. The O3—H3 group acts as the donor with respect to the carboxyl­ate oxygen atom O1 of a neighbouring chain (O^iv in Fig. 12 ▸, type c). This leads to an (18) motif between adjacent 3-(3,4-di­hydroxy­phen­yl)-2-propenoate units (Fig. 13 ▸). Finally, the cross-linking of the chains is completed by hydrogen bonds of the type d with the O4—H4 group as the donor and the water oxygen atom O5 of a neighbouring chain as acceptor. The position of the different hydrogen-bonding types is displayed in Fig. 15 ▸. Fig. 16 ▸ shows a packing diagram with the complete hydrogen-bonding network of 2. In direct comparison with 1, the hydrogen bonds in 2 are significantly stronger, with the closest O⋯O distance being 2.6350 (19) Å (Table 5 ▸).

Figure 14.

Intra-chain hydrogen bonds in compound 2.

Figure 15.

Position of the hydrogen bonds (dashed lines) along the NaO₇ polyhedral chains in the crystal structure of 2. Symmetry codes refer to Table 3 ▸. Additional symmetry codes: (x) x − 1, y + 1, z; (xi) x + 1, y, z.

Figure 16.

Section of the crystal structure of 2 showing the complete hydrogen-bonding network (dashed lines).

4. Database survey

A search of the Cambridge Structural Database (CSD, Version 2022.3; Groom et al., 2016 ▸) for metal caffeates revealed only the crystal structure of the potassium caffeate/caffeic acid co-crystallization product (CSD code GIFXEA; Lombardo et al., 2012 ▸). Furthermore, there are 16 crystal structures containing caffeic acid as free acid, hydrate or co-crystals with various organic mol­ecules.

5. Synthesis and crystallization

2 mmol of the alkali hydroxide (48 mg, LiOH, 80 mg NaOH) and 2 mmol of caffeic acid (360 mg) were dissolved in 5 ml of water to give a clear solution. After slow evaporation the products were isolated as colourless solids in nearly qu­anti­tative yield. Single crystals were obtained by recrystallization from water.

Compound 1: IR: 1643 m, 1616 w, 1548 s, 1524 m, 1441 w, 1401 vs, 1360 w, 1304 w, 1249 vs, 1195 w, 1164 s, 1109 s, 971 s, 859 s, 809 s, 714 s, 602 w, 581 s cm⁻¹.

Compound 2: IR: 1641 m, 1601 m, 1519 s, 1474 w, 1409 w, 1369 s, 1290 w, 1273 m, 1250 s, 1224 w, 1195 m, 1012 w, 969 s, 829 w, 873 w, 859 m, 814 s, 739 m, 695 m, 600 m, 564 s, 516 m cm⁻¹.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 6 ▸. All carbon-bound hydrogen atoms were positioned geometrically (C—H = 0.94 Å) and refined as riding, with U _iso(H) = 1.2U _eq(C). Hydrogen atoms bound to oxygen were found in difference-Fourier maps. The O—H distances of 2 were restricted to 0.82 Å.

Table 6. Experimental details.

	1	2
Crystal data
Chemical formula	[Li(C9H7O4)(H2O)]	[Na(C9H7O4)(H2O)]
M r	204.10	220.15
Crystal system, space group	Monoclinic, P21/n	Triclinic, P
Temperature (K)	220	293
a, b, c (Å)	8.3083 (12), 4.8511 (5), 22.587 (4)	6.3289 (13), 6.8126 (14), 11.253 (2)
α, β, γ (°)	90, 98.572 (18), 90	75.05 (2), 86.39 (2), 78.09 (2)
V (Å3)	900.2 (2)	458.64 (17)
Z	4	2
Radiation type	Mo Kα	Mo Kα
μ (mm−1)	0.12	0.17
Crystal size (mm)	0.46 × 0.15 × 0.15	0.4 × 0.2 × 0.08
Data collection
Diffractometer	Stoe IPDS 2	Stoe IPDS 2
No. of measured, independent and observed [I > 2σ(I)] reflections	4973, 1735, 1314	7192, 1798, 1331
R int	0.027	0.048
(sin θ/λ)max (Å−1)	0.619	0.619
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.032, 0.079, 1.01	0.035, 0.095, 1.00
No. of reflections	1735	1798
No. of parameters	152	152
No. of restraints	0	4
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement	H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3)	0.19, −0.15	0.24, −0.22

Computer programs: X-AREA (Stoe & Cie, 2016 ▸), SHELXT (Sheldrick, 2015a ▸), SHELXL (Sheldrick, 2015b ▸), DIAMOND (Brandenburg & Putz, 2019 ▸) and OLEX2 (Dolomanov et al., 2009 ▸).

Supplementary Material

CCDC references: 2340673, 2340672

Additional supporting information: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Poly[aqua[µ-3-(3,4-dihydroxyphenyl)propenoato]lithium] (1). Crystal data

[Li(C9H7O4)(H2O)]	F(000) = 424
Mr = 204.10	Dx = 1.506 Mg m−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 8.3083 (12) Å	Cell parameters from 3964 reflections
b = 4.8511 (5) Å	θ = 2.5–26.0°
c = 22.587 (4) Å	µ = 0.12 mm−1
β = 98.572 (18)°	T = 220 K
V = 900.2 (2) Å3	Block, colourless
Z = 4	0.46 × 0.15 × 0.15 mm

Poly[aqua[µ-3-(3,4-dihydroxyphenyl)propenoato]lithium] (1). Data collection

Stoe IPDS 2 diffractometer	1314 reflections with I > 2σ(I)
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus, Incoatec Iµs	Rint = 0.027
Plane graphite monochromator	θmax = 26.1°, θmin = 2.5°
Detector resolution: 6.67 pixels mm-1	h = −10→10
rotation method scans	k = −5→5
4973 measured reflections	l = −27→27
1735 independent reflections

Poly[aqua[µ-3-(3,4-dihydroxyphenyl)propenoato]lithium] (1). Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Hydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.032	H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.079	w = 1/[σ2(Fo2) + (0.047P)2 + 0.0259P] where P = (Fo2 + 2Fc2)/3
S = 1.01	(Δ/σ)max = 0.001
1735 reflections	Δρmax = 0.19 e Å−3
152 parameters	Δρmin = −0.15 e Å−3
0 restraints

Poly[aqua[µ-3-(3,4-dihydroxyphenyl)propenoato]lithium] (1). Special details

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

Poly[aqua[µ-3-(3,4-dihydroxyphenyl)propenoato]lithium] (1). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.71575 (16)	0.1874 (3)	0.65653 (5)	0.0232 (3)
C2	0.74035 (18)	0.0573 (3)	0.59901 (6)	0.0297 (3)
H2	0.787147	−0.119367	0.599929	0.036*
C3	0.69907 (16)	0.1798 (3)	0.54634 (6)	0.0274 (3)
H3A	0.647720	0.352195	0.547117	0.033*
C4	0.72381 (16)	0.0791 (3)	0.48705 (6)	0.0265 (3)
C5	0.64958 (16)	0.2210 (3)	0.43618 (6)	0.0279 (3)
H5	0.579486	0.369071	0.440744	0.034*
C6	0.67740 (16)	0.1475 (3)	0.37929 (6)	0.0272 (3)
C7	0.78474 (16)	−0.0658 (3)	0.37246 (6)	0.0271 (3)
C8	0.85657 (17)	−0.2130 (3)	0.42205 (6)	0.0307 (3)
H8	0.926536	−0.360889	0.417203	0.037*
C9	0.82555 (18)	−0.1427 (3)	0.47885 (6)	0.0315 (3)
H9	0.873489	−0.245454	0.512161	0.038*
Li	0.7956 (3)	0.6632 (5)	0.71799 (10)	0.0283 (5)
O1	0.75014 (12)	0.0450 (2)	0.70375 (4)	0.0297 (3)
O2	0.66671 (12)	0.43357 (19)	0.65694 (4)	0.0294 (3)
O3	0.60783 (14)	0.2806 (2)	0.32801 (4)	0.0376 (3)
H3	0.525 (3)	0.395 (4)	0.3355 (9)	0.060 (6)*
O4	0.81610 (14)	−0.1140 (3)	0.31514 (4)	0.0362 (3)
H4	0.869 (3)	−0.271 (5)	0.3134 (9)	0.068 (7)*
O5	1.03368 (14)	0.5915 (3)	0.71894 (5)	0.0361 (3)
H5A	1.082 (3)	0.740 (6)	0.7122 (11)	0.092 (9)*
H5B	1.070 (3)	0.548 (5)	0.7522 (11)	0.070 (7)*

Poly[aqua[µ-3-(3,4-dihydroxyphenyl)propenoato]lithium] (1). Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
C1	0.0269 (7)	0.0219 (7)	0.0211 (7)	−0.0027 (6)	0.0043 (5)	0.0003 (5)
C2	0.0412 (8)	0.0232 (7)	0.0258 (7)	−0.0006 (6)	0.0089 (6)	−0.0027 (6)
C3	0.0281 (7)	0.0301 (8)	0.0245 (7)	−0.0019 (6)	0.0056 (5)	−0.0028 (6)
C4	0.0272 (7)	0.0298 (8)	0.0232 (7)	−0.0049 (6)	0.0056 (5)	−0.0021 (6)
C5	0.0265 (7)	0.0327 (8)	0.0255 (7)	0.0004 (6)	0.0068 (5)	−0.0031 (6)
C6	0.0268 (7)	0.0327 (8)	0.0217 (7)	−0.0033 (6)	0.0026 (5)	−0.0009 (5)
C7	0.0276 (7)	0.0323 (8)	0.0222 (7)	−0.0048 (6)	0.0063 (5)	−0.0052 (6)
C8	0.0329 (8)	0.0283 (8)	0.0314 (7)	0.0030 (7)	0.0061 (6)	−0.0039 (6)
C9	0.0377 (8)	0.0315 (8)	0.0249 (7)	−0.0022 (7)	0.0034 (6)	0.0005 (6)
Li	0.0389 (13)	0.0229 (11)	0.0239 (11)	0.0025 (10)	0.0075 (9)	−0.0009 (9)
O1	0.0468 (6)	0.0226 (5)	0.0208 (5)	0.0037 (4)	0.0087 (4)	0.0015 (4)
O2	0.0406 (6)	0.0227 (5)	0.0242 (5)	0.0047 (5)	0.0019 (4)	−0.0011 (4)
O3	0.0420 (6)	0.0486 (7)	0.0220 (5)	0.0132 (6)	0.0038 (4)	0.0016 (5)
O4	0.0455 (6)	0.0419 (7)	0.0229 (5)	0.0066 (6)	0.0106 (4)	−0.0046 (5)
O5	0.0378 (6)	0.0444 (7)	0.0261 (6)	0.0060 (6)	0.0049 (5)	0.0005 (5)

Poly[aqua[µ-3-(3,4-dihydroxyphenyl)propenoato]lithium] (1). Geometric parameters (Å, º)

C1—C2	1.4855 (18)	C7—O4	1.3781 (16)
C1—O1	1.2669 (16)	C8—H8	0.9400
C1—O2	1.2624 (16)	C8—C9	1.388 (2)
C2—H2	0.9400	C9—H9	0.9400
C2—C3	1.3285 (19)	Li—Lii	2.979 (3)
C3—H3A	0.9400	Li—Lii	2.979 (3)
C3—C4	1.4685 (18)	Li—O1ii	1.949 (2)
C4—C5	1.401 (2)	Li—O1iii	1.908 (2)
C4—C9	1.398 (2)	Li—O2	1.962 (2)
C5—H5	0.9400	Li—O5	2.005 (3)
C5—C6	1.3857 (18)	O3—H3	0.92 (2)
C6—C7	1.390 (2)	O4—H4	0.88 (3)
C6—O3	1.3757 (17)	O5—H5A	0.85 (3)
C7—C8	1.386 (2)	O5—H5B	0.79 (3)
O1—C1—C2	117.48 (12)	C8—C9—H9	119.6
O2—C1—C2	119.66 (12)	Lii—Li—Liii	109.00 (13)
O2—C1—O1	122.83 (12)	O1iii—Li—Liii	39.93 (3)
C1—C2—H2	118.6	O1iii—Li—Lii	144.46 (14)
C3—C2—C1	122.84 (13)	O1ii—Li—Lii	38.92 (9)
C3—C2—H2	118.6	O1ii—Li—Liii	72.61 (11)
C2—C3—H3A	116.0	O1iii—Li—O1ii	112.20 (11)
C2—C3—C4	127.96 (14)	O1ii—Li—O2	108.08 (12)
C4—C3—H3A	116.0	O1iii—Li—O2	111.04 (12)
C5—C4—C3	118.68 (13)	O1ii—Li—O5	105.35 (12)
C9—C4—C3	123.15 (12)	O1iii—Li—O5	109.92 (12)
C9—C4—C5	118.07 (12)	O2—Li—Lii	74.16 (8)
C4—C5—H5	119.3	O2—Li—Liii	130.66 (15)
C6—C5—C4	121.35 (14)	O2—Li—O5	110.08 (11)
C6—C5—H5	119.3	O5—Li—Lii	100.11 (11)
C5—C6—C7	119.53 (12)	O5—Li—Liii	117.27 (13)
O3—C6—C5	123.57 (13)	C1—O1—Liiv	133.25 (11)
O3—C6—C7	116.87 (11)	C1—O1—Lii	123.58 (11)
C8—C7—C6	120.01 (12)	Liiv—O1—Lii	101.15 (8)
O4—C7—C6	116.41 (12)	C1—O2—Li	113.53 (11)
O4—C7—C8	123.56 (13)	C6—O3—H3	111.2 (12)
C7—C8—H8	119.9	C7—O4—H4	110.7 (14)
C7—C8—C9	120.23 (13)	Li—O5—H5A	110.0 (18)
C9—C8—H8	119.9	Li—O5—H5B	106.7 (16)
C4—C9—H9	119.6	H5A—O5—H5B	106 (2)
C8—C9—C4	120.72 (13)
C1—C2—C3—C4	176.94 (13)	C5—C6—C7—O4	−175.22 (12)
C2—C1—O1—Liiv	−12.6 (2)	C6—C7—C8—C9	−2.0 (2)
C2—C1—O1—Lii	−173.12 (12)	C7—C8—C9—C4	−1.0 (2)
C2—C1—O2—Li	−131.35 (13)	C9—C4—C5—C6	−0.9 (2)
C2—C3—C4—C5	170.59 (14)	O1—C1—C2—C3	175.69 (13)
C2—C3—C4—C9	−13.2 (2)	O1—C1—O2—Li	46.58 (17)
C3—C4—C5—C6	175.49 (13)	O2—C1—C2—C3	−6.3 (2)
C3—C4—C9—C8	−173.87 (13)	O2—C1—O1—Liiv	169.48 (14)
C4—C5—C6—C7	−1.9 (2)	O2—C1—O1—Lii	8.9 (2)
C4—C5—C6—O3	−179.85 (13)	O3—C6—C7—C8	−178.57 (13)
C5—C4—C9—C8	2.4 (2)	O3—C6—C7—O4	2.84 (18)
C5—C6—C7—C8	3.4 (2)	O4—C7—C8—C9	176.53 (13)

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

Poly[aqua[µ-3-(3,4-dihydroxyphenyl)propenoato]lithium] (1). Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3···O2v	0.92 (2)	1.83 (2)	2.734 (2)	168 (2)
O4—H4···O5vi	0.88 (2)	1.94 (2)	2.793 (2)	160.7 (2)
O5—H5A···O4vii	0.85 (3)	2.13 (2)	2.977 (2)	173 (2)
O5—H5B···O3viii	0.80 (2)	2.33 (2)	3.042 (2)	150 (2)
O5—H5B···O4viii	0.80 (2)	2.33 (2)	2.953 (2)	136 (2)

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

Poly[aqua[µ-3-(3,4-dihydroxyphenyl)propenoato]sodium] (2). Crystal data

[Na(C9H7O4)(H2O)]	Z = 2
Mr = 220.15	F(000) = 228
Triclinic, P1	Dx = 1.594 Mg m−3
a = 6.3289 (13) Å	Mo Kα radiation, λ = 0.71073 Å
b = 6.8126 (14) Å	Cell parameters from 2529 reflections
c = 11.253 (2) Å	θ = 3.1–26.0°
α = 75.05 (2)°	µ = 0.17 mm−1
β = 86.39 (2)°	T = 293 K
γ = 78.09 (2)°	Plate, colourless
V = 458.64 (17) Å3	0.4 × 0.2 × 0.08 mm

Poly[aqua[µ-3-(3,4-dihydroxyphenyl)propenoato]sodium] (2). Data collection

Stoe IPDS 2 diffractometer	1331 reflections with I > 2σ(I)
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus, Incoatec Iµs	Rint = 0.048
Plane graphite monochromator	θmax = 26.1°, θmin = 3.2°
Detector resolution: 6.67 pixels mm-1	h = −7→7
rotation method scans	k = −8→8
7192 measured reflections	l = −13→13
1798 independent reflections

Poly[aqua[µ-3-(3,4-dihydroxyphenyl)propenoato]sodium] (2). Refinement

Refinement on F2	Primary atom site location: dual
Least-squares matrix: full	Hydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.035	H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.095	w = 1/[σ2(Fo2) + (0.0615P)2] where P = (Fo2 + 2Fc2)/3
S = 1.00	(Δ/σ)max < 0.001
1798 reflections	Δρmax = 0.24 e Å−3
152 parameters	Δρmin = −0.22 e Å−3
4 restraints

Poly[aqua[µ-3-(3,4-dihydroxyphenyl)propenoato]sodium] (2). Special details

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

Poly[aqua[µ-3-(3,4-dihydroxyphenyl)propenoato]sodium] (2). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.7621 (3)	0.0311 (2)	0.28917 (15)	0.0254 (4)
C2	0.7226 (3)	0.1072 (2)	0.15528 (14)	0.0264 (4)
H2	0.8399	0.1004	0.1013	0.032*
C3	0.5262 (3)	0.1847 (2)	0.10941 (15)	0.0255 (4)
H3A	0.4138	0.1903	0.1666	0.031*
C4	0.4642 (3)	0.2624 (2)	−0.01989 (14)	0.0227 (3)
C5	0.6151 (3)	0.2576 (2)	−0.11683 (15)	0.0251 (4)
H5	0.7604	0.2042	−0.0994	0.030*
C6	0.5499 (3)	0.3310 (2)	−0.23713 (14)	0.0251 (4)
C7	0.3322 (3)	0.4163 (2)	−0.26497 (14)	0.0228 (3)
C8	0.1815 (3)	0.4196 (2)	−0.17098 (14)	0.0259 (4)
H8	0.0363	0.4734	−0.1888	0.031*
C9	0.2482 (3)	0.3420 (2)	−0.04956 (14)	0.0260 (4)
H9	0.1458	0.3434	0.0134	0.031*
Na	0.44737 (11)	0.27100 (10)	0.47948 (6)	0.0348 (2)
O1	0.95808 (19)	−0.0433 (2)	0.32325 (11)	0.0363 (3)
O2	0.60826 (19)	0.04183 (18)	0.36431 (10)	0.0328 (3)
O3	0.6857 (2)	0.3298 (2)	−0.33673 (11)	0.0387 (3)
H3	0.800 (3)	0.243 (4)	−0.314 (2)	0.070 (8)*
O4	0.2845 (2)	0.48950 (18)	−0.38767 (10)	0.0304 (3)
H4	0.164 (3)	0.558 (3)	−0.391 (2)	0.053 (7)*
O5	0.0849 (2)	0.2438 (2)	0.43233 (13)	0.0345 (3)
H5A	0.070 (4)	0.163 (3)	0.391 (2)	0.061 (8)*
H5B	0.070 (4)	0.187 (4)	0.5048 (17)	0.059 (7)*

Poly[aqua[µ-3-(3,4-dihydroxyphenyl)propenoato]sodium] (2). Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
C1	0.0297 (9)	0.0243 (8)	0.0217 (8)	−0.0013 (6)	−0.0040 (6)	−0.0074 (6)
C2	0.0302 (9)	0.0310 (8)	0.0179 (8)	−0.0074 (7)	0.0019 (6)	−0.0054 (6)
C3	0.0320 (9)	0.0251 (8)	0.0190 (8)	−0.0054 (6)	0.0016 (6)	−0.0054 (6)
C4	0.0291 (8)	0.0213 (7)	0.0177 (8)	−0.0046 (6)	−0.0009 (6)	−0.0048 (6)
C5	0.0235 (8)	0.0271 (8)	0.0220 (8)	−0.0018 (6)	−0.0030 (6)	−0.0031 (6)
C6	0.0274 (8)	0.0261 (8)	0.0197 (8)	−0.0039 (6)	0.0036 (6)	−0.0042 (6)
C7	0.0293 (9)	0.0215 (7)	0.0164 (8)	−0.0023 (6)	−0.0033 (6)	−0.0042 (6)
C8	0.0238 (8)	0.0268 (8)	0.0240 (9)	0.0009 (6)	−0.0024 (6)	−0.0050 (6)
C9	0.0278 (8)	0.0287 (8)	0.0199 (8)	−0.0025 (6)	0.0035 (6)	−0.0066 (6)
Na	0.0381 (4)	0.0366 (4)	0.0316 (4)	−0.0084 (3)	0.0087 (3)	−0.0132 (3)
O1	0.0302 (7)	0.0487 (7)	0.0270 (7)	0.0046 (5)	−0.0078 (5)	−0.0123 (5)
O2	0.0343 (7)	0.0399 (7)	0.0195 (6)	0.0017 (5)	0.0019 (5)	−0.0068 (5)
O3	0.0304 (7)	0.0546 (8)	0.0191 (6)	0.0056 (6)	0.0051 (5)	−0.0004 (5)
O4	0.0323 (7)	0.0360 (6)	0.0165 (6)	0.0050 (5)	−0.0046 (5)	−0.0033 (5)
O5	0.0356 (7)	0.0375 (7)	0.0262 (7)	−0.0005 (5)	−0.0078 (5)	−0.0039 (6)

Poly[aqua[µ-3-(3,4-dihydroxyphenyl)propenoato]sodium] (2). Geometric parameters (Å, º)

C1—C2	1.481 (2)	Na—Naii	3.4689 (15)
C1—O2	1.252 (2)	Na—O2i	2.4608 (15)
C1—O1	1.282 (2)	Na—O2	2.3185 (14)
C2—H2	0.9300	Na—O3iii	2.7897 (17)
C2—C3	1.327 (2)	Na—O3iv	2.7668 (16)
C3—H3A	0.9300	Na—O4iv	2.5810 (16)
C3—C4	1.463 (2)	Na—O4iii	2.4153 (15)
C4—C5	1.406 (2)	Na—O5	2.4411 (16)
C4—C9	1.390 (2)	Na—H5B	2.55 (2)
C5—H5	0.9300	O2—Nai	2.4608 (15)
C5—C6	1.374 (2)	O3—Nav	2.7897 (17)
C6—C7	1.401 (2)	O3—Naiv	2.7669 (16)
C6—O3	1.3695 (19)	O3—H3	0.841 (17)
C7—C8	1.380 (2)	O4—Naiv	2.5810 (16)
C7—O4	1.3715 (19)	O4—Nav	2.4153 (15)
C8—H8	0.9300	O4—H4	0.803 (16)
C8—C9	1.390 (2)	O5—H5A	0.827 (17)
C9—H9	0.9300	O5—H5B	0.816 (17)
Na—Nai	3.5262 (15)
O1—C1—C2	117.18 (14)	O3iii—Na—Naii	51.08 (4)
O2—C1—C2	120.37 (14)	O3iv—Na—Nai	151.40 (5)
O2—C1—O1	122.45 (15)	O3iii—Na—Nai	104.16 (5)
C1—C2—H2	118.8	O3iv—Na—Naii	51.67 (4)
C3—C2—C1	122.43 (15)	O3iv—Na—O3iii	102.74 (4)
C3—C2—H2	118.8	O3iv—Na—H5B	94.7 (5)
C2—C3—H3A	116.0	O3iii—Na—H5B	126.0 (4)
C2—C3—C4	128.09 (15)	O4iii—Na—Nai	132.15 (5)
C4—C3—H3A	116.0	O4iii—Na—Naii	48.03 (4)
C5—C4—C3	122.50 (15)	O4iv—Na—Naii	44.09 (3)
C9—C4—C3	119.45 (14)	O4iv—Na—Nai	125.28 (5)
C9—C4—C5	118.04 (14)	O4iii—Na—O2i	91.26 (5)
C4—C5—H5	119.7	O4iv—Na—O3iv	57.67 (4)
C6—C5—C4	120.66 (15)	O4iii—Na—O3iv	71.38 (4)
C6—C5—H5	119.7	O4iv—Na—O3iii	68.74 (4)
C5—C6—C7	120.37 (15)	O4iii—Na—O3iii	59.01 (4)
O3—C6—C5	124.36 (15)	O4iii—Na—O4iv	92.12 (5)
O3—C6—C7	115.27 (14)	O4iii—Na—O5	88.31 (5)
C8—C7—C6	119.71 (14)	O4iv—Na—H5B	152.3 (5)
O4—C7—C6	115.86 (14)	O4iii—Na—H5B	80.0 (5)
O4—C7—C8	124.43 (14)	O5—Na—Nai	83.14 (5)
C7—C8—H8	120.2	O5—Na—Naii	121.25 (5)
C7—C8—C9	119.57 (14)	O5—Na—O2i	77.91 (5)
C9—C8—H8	120.2	O5—Na—O3iv	81.58 (5)
C4—C9—H9	119.2	O5—Na—O3iii	142.21 (5)
C8—C9—C4	121.62 (15)	O5—Na—O4iv	136.45 (5)
C8—C9—H9	119.2	O5—Na—H5B	18.6 (4)
Naii—Na—Nai	153.76 (5)	C1—O2—Na	136.46 (11)
Naii—Na—H5B	122.5 (6)	C1—O2—Nai	119.95 (10)
Nai—Na—H5B	77.2 (5)	Na—O2—Nai	95.05 (5)
O2—Na—Nai	44.04 (4)	C6—O3—Nav	106.29 (10)
O2i—Na—Nai	40.91 (3)	C6—O3—Naiv	101.08 (9)
O2—Na—Naii	134.17 (5)	C6—O3—H3	108.4 (19)
O2i—Na—Naii	128.97 (5)	Naiv—O3—Nav	77.26 (4)
O2—Na—O2i	84.95 (5)	Naiv—O3—H3	140.1 (19)
O2i—Na—O3iii	83.95 (5)	Nav—O3—H3	117.7 (19)
O2—Na—O3iii	118.94 (5)	C7—O4—Nav	116.66 (9)
O2—Na—O3iv	112.69 (5)	C7—O4—Naiv	105.73 (10)
O2i—Na—O3iv	153.47 (5)	C7—O4—H4	105.9 (17)
O2—Na—O4iii	175.93 (5)	Nav—O4—Naiv	87.88 (5)
O2—Na—O4iv	90.18 (5)	Nav—O4—H4	127.7 (17)
O2i—Na—O4iv	145.56 (5)	Naiv—O4—H4	109.1 (17)
O2—Na—O5	92.33 (5)	Na—O5—H5A	119.7 (18)
O2—Na—H5B	99.4 (5)	Na—O5—H5B	88.4 (18)
O2i—Na—H5B	61.8 (5)	H5A—O5—H5B	108 (2)
C1—C2—C3—C4	−179.15 (14)	C6—C7—O4—Naiv	−50.68 (14)
C2—C1—O2—Na	−94.99 (19)	C6—C7—O4—Nav	44.96 (17)
C2—C1—O2—Nai	126.10 (13)	C7—C6—O3—Naiv	46.19 (15)
C2—C3—C4—C5	2.1 (3)	C7—C6—O3—Nav	−33.62 (16)
C2—C3—C4—C9	−178.71 (16)	C7—C8—C9—C4	0.6 (2)
C3—C4—C5—C6	179.58 (14)	C8—C7—O4—Nav	−134.11 (14)
C3—C4—C9—C8	179.34 (14)	C8—C7—O4—Naiv	130.25 (14)
C4—C5—C6—C7	1.5 (2)	C9—C4—C5—C6	0.4 (2)
C4—C5—C6—O3	−179.20 (15)	O1—C1—C2—C3	179.07 (15)
C5—C4—C9—C8	−1.5 (2)	O1—C1—O2—Nai	−54.4 (2)
C5—C6—C7—C8	−2.3 (2)	O1—C1—O2—Na	84.5 (2)
C5—C6—C7—O4	178.54 (14)	O2—C1—C2—C3	−1.4 (2)
C5—C6—O3—Naiv	−133.17 (15)	O3—C6—C7—C8	178.27 (15)
C5—C6—O3—Nav	147.02 (14)	O3—C6—C7—O4	−0.8 (2)
C6—C7—C8—C9	1.3 (2)	O4—C7—C8—C9	−179.66 (14)

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

Poly[aqua[µ-3-(3,4-dihydroxyphenyl)propenoato]sodium] (2). Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3···O1vi	0.84 (2)	1.84 (2)	2.6437 (19)	158 (2)
O4—H4···O5vii	0.81 (2)	1.85 (2)	2.6350 (19)	166 (2)
O5—H5A···O1viii	0.83 (2)	2.02 (2)	2.826 (2)	163 (2)
O5—H5B···O1i	0.82 (2)	1.95 (2)	2.7614 (19)	178 (3)

Symmetry codes: (i) −x+1, −y, −z+1; (vi) −x+2, −y, −z; (vii) −x, −y+1, −z; (viii) x−1, y, z.