Polymeric sodium 3,5-di­carboxy­benzene­sulfonate–urea–water (1/1/1)

In the title compound, poly­[sodium-μ₄-3,5-di­carboxy­benzene­sulfonato-κ⁴O:O′:O′′:O′′′-μ₂-urea-κ²O:N] monohydrate], {[Na(C₈H₅O₇S)(CH₄N₂O)]·H₂O}_n, the organic anions are arranged almost vertically within (001) monolayers, with the sulfonate and carboxylic acid groups pointing into the interlayer region. The inversion-related aromatic rings of the anions inside the layers are arrayed via offset face-to-face interactions into molecular stacks along the crystallographic a axis. The `up' and `down' arrangement of the aromatic portions makes both faces of the layers ionic and hydro­philic, whereas the interiors of the layers are primarily hydro­phobic. The interleaving of the anions is such that the carboxylic acid groups are oriented more toward the interior than are the sulfonate groups. The aromatic rings in neighbouring layers are arranged in a herring-bone fashion. The coordination sphere of the Na⁺ ions contains two sulfonate and two carboxylic acid O atoms, from a total of four different acid anions belonging to two neighbouring anionic monolayers. The urea mol­ecules are positioned between translation-related anionic stacks inside the (001) layers, serving a triple function, viz. they fill in the large meshes (empty cavities) formed within the anionic–cationic network, and they provide additional Na⁺ coordination and hydrogen-bond sites.

S1. Comment

Mixed organic–inorganic compounds with layered structures have been intensively studied, due to their potential chemical applications. In particular, metal phosphonates forming rigid covalent inorganic layers separated by weakly interacting organic domains are of longstanding interest, due to the possibility of manipulating the size and hydrophobic nature of the interlayer region and, therefore, the physical properties of the material (Zhang & Clearfield, 1991). More recently, metal organosulfonates have been studied as structural analogues of metal phosphonates (Gunderman & Squattrito, 1994, 1995). On the other hand, Ward and co-workers synthesized and studied numerous guanidinium alkene- and arenesulfonates displaying broad structural diversity, starting from layered materials (Russell et al., 1994), and moving on to nanoporous molecular sandwiches {Russell et al., 1997) and crystalline clathrates (Evans et al., 1999; Holman & Ward, 2000). In an earlier paper, we studied the competition of sulfonic and carboxylic acid groups for hydrogen-bond formation and, therefore, for crystal network organization (Videnova-Adrabińska et al., 2001). Here, we discuss the competitive coordination capabilities of these two groups versus the Na⁺ ion in the title urea-sodium sulfoisophthalate (1:1) cocrystal, (I). \sch

The coordination geometry of the Na⁺ ion in (I) is sixfold and irregular, with five Na—O distances in the range 2.3065 (9)–2.4465 (9) Å. The sixth, somewhat elongated, coordination bond [Na—N2^iv 2.7869 (12) Å; symmetry code: (iv) ?] is to one of the N atoms of another urea molecule (Table 1 and Fig. 1).

A more detailed analysis of the molecular organization in the crystal of (I) reveals a helical arrangement of the ligands around the Na⁺ ions (Fig. 2). Only the carboxylic acid groups are involved in the formation of the helical chains that run up and down along the crystallographic b direction [Na—O21 2.3223 (9) and Na—O23ⁱ 2.3065 (9) Å; symmetry code: (i) ?]. On the other hand, the sulfonate group, providing two additional O coordination sites, serves to associate neighbouring helical chains into double helices [Na—O35ⁱⁱⁱ 2.4230 (9) and Na—O15ⁱⁱ 2.4465 (9) Å; symmetry codes: (ii) ?; (iii) ?].

The three-dimensional crystal network of (I) is furnished by dense packing of these double helices via translation relations in the a and c directions, so that the overall crystal architecture can be considered as consisting of (001) organic layers with alternating sulfoisophthalate and urea galleries (Fig. 3). The aromatic rings located in the turns of the helices are alternately arranged in (210) and (210) planes in order to form stacks along the a axes, with consecutive offset face-to-face and van der Waals interactions in between. The urea molecules are embedded in the anionic–cationic network so as to occupy the empty filaments (corridors) generated between the sulfoisophthalate galleries. The narrow inorganic regions, where the Na⁺ ions reside, link the organic monolayers.

Numerous hydrogen bonds to and from the urea and water molecules additionally stabilize the three-dimensional architecture of (I) (Table 2 and Fig. 4). A relatively short hydrogen bond [O11—H1···O10 2.5495 (11) Å] is formed between the sulfoisophthalate and the urea ligands inside the monolayers. Another hydrogen bond, formed between one of the carboxylic acid groups and the sulfonate group of a reflection-related anion [O13—H3···O35ⁱ 2.7052 (11) Å] traverses the interlayer region along the [101] direction, in addition to the coordination bonds. A non-coordinated crystal water molecule also stabilizes the three-dimensional crystal architecture via four hydrogen bonds (Table 2).

In conclusion, it is pertinent to draw attention to the coordination properties of the Na⁺ ion. Although the sulfonic acid group is deprotonated, the Na⁺ cation is distributed between both the carboxylic acid groups and the sulfonate group. Therefore, the anion–cation interrelations are changed from a purely ionic interaction to being coordination bonds. Interestingly, the non-charged carboxylic acid groups coordinate to the Na⁺ ion more strongly than the formally charged sulfonate group does.

S2. Experimental

The synthesis of the (I) was carried out by a reaction of sodium 5-sulfoisophthalate (0.50 g) and urea (0.22 g) dissolved in a hot mixture of H₂O and methanol (10 ml, 1:1). The reaction solution was allowed to stand at room temperature for 12 d, until colourless crystals were obtained. Prior to the X-ray measurements, the crystal sample was polished with the aid of water in order to obtain a spherical shape.

Computing details

Data collection: KM-4 CCD Software (Kuma Diffraction, 2000); cell refinement: KM-4 CCD Software; data reduction: KM-4 CCD Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. A view of the coordination sphere around the Na^+ ion in (I). Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii [symmetry codes: (i) ?; (ii) ?; (iii) ?; (iv) ?]
	Fig. 2. A view of the single helical chain running along the b direction (left) and of the double helix (right), which is formed by two inversion-related chains (`up' and `down' strands) and translated along the c axis relative to the single chain.
	Fig. 3. A view of the crystal structure of (I) along the a axis, showing the coordination network. The urea and sulfonic acid moieties are stacked in galleries along the a axis and form undulating (001) organic layers that are separated by narrow inorganic regions. Both faces of the layers are ionic and hydrophilic, whereas the interior of the layer is divided into hydrophobic and hydrophilic filaments (Fig. 4). For the sake of clarity, water molecules and hydrogen bonds have been omitted.
	Fig. 4. The same view as in Fig. 3, but showing the three-dimensional hydrogen-bonded network in (I) (coordination bonds have been omitted). The urea molecules, via a strong hydrogen bond donated from one of the carboxylic acid groups, serve to link the hydrophobic filaments in the layers. Carboxylic acid–sulfonate, urea–water and water–sulfonate hydrogen bonds interweave the monolayers.

Poly[sodium-µ₄-3,5-dicarboxybenzenesulfonate- κ⁴O:O':O'':O'''-µ₂-urea-κ²O:N] monohydrate]

Crystal data

[Na(C8H5O7S)(CH4N2O)]·H2O	F(000) = 712
Mr = 346.26	Dx = 1.668 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 15999 reflections
a = 8.203 (3) Å	θ = 2–37°
b = 11.566 (4) Å	µ = 0.32 mm^−1
c = 14.534 (4) Å	T = 100 K
β = 91.025 (3)°	Spherical, colourless
V = 1378.7 (8) Å^3	0.3 × 0.3 × 0.3 mm
Z = 4

Data collection

Kuma KM-4 CCD area-detector diffractometer	5744 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.024
Graphite monochromator	θmax = 37.5°, θmin = 3.3°
ω scans	h = −14→12
22990 measured reflections	k = −19→19
6900 independent reflections	l = −24→24

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)] = 0.035	All H-atom parameters refined
wR(F^2) = 0.091	w = 1/[σ^2(Fo^2) + (0.0469P)^2 + 0.1356P] where P = (Fo^2 + 2Fc^2)/3
S = 1.10	(Δ/σ)max = 0.001
6900 reflections	Δρmax = 0.57 e Å^−3
244 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: 0.0033 (9)

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
Na	0.55261 (5)	0.14119 (3)	0.33996 (2)	0.01129 (8)
C11	0.39454 (11)	0.32400 (8)	0.48549 (6)	0.01131 (14)
O11	0.46065 (10)	0.27266 (6)	0.55778 (5)	0.01693 (14)
O21	0.40319 (10)	0.28866 (6)	0.40661 (5)	0.01766 (14)
H1	0.510 (2)	0.2133 (17)	0.5398 (13)	0.040 (5)*
C31	0.07506 (11)	0.66165 (7)	0.37724 (6)	0.01051 (14)
O13	−0.01529 (9)	0.75239 (6)	0.40050 (5)	0.01620 (14)
O23	0.08903 (9)	0.62891 (6)	0.29822 (4)	0.01504 (13)
H3	−0.068 (2)	0.7691 (17)	0.3526 (14)	0.049 (5)*
S	0.18594 (3)	0.617774 (17)	0.733274 (13)	0.00813 (5)
O15	0.22703 (8)	0.51866 (6)	0.79203 (4)	0.01152 (12)
O25	0.01749 (8)	0.65548 (6)	0.74123 (4)	0.01208 (12)
O35	0.30261 (8)	0.71288 (6)	0.74595 (4)	0.01284 (12)
C1	0.30668 (10)	0.43329 (7)	0.50831 (6)	0.01002 (14)
C2	0.23757 (11)	0.49797 (7)	0.43693 (6)	0.01028 (14)
C3	0.15327 (10)	0.59977 (7)	0.45642 (6)	0.00932 (13)
C4	0.13727 (11)	0.63710 (7)	0.54707 (6)	0.00964 (13)
C5	0.20716 (10)	0.57076 (7)	0.61796 (5)	0.00874 (13)
C6	0.29193 (10)	0.46957 (7)	0.59950 (6)	0.00981 (13)
H2	0.2439 (17)	0.4719 (12)	0.3780 (10)	0.018 (3)*
H4	0.0806 (17)	0.7070 (13)	0.5596 (10)	0.017 (3)*
H6	0.3388 (17)	0.4226 (13)	0.6488 (10)	0.016 (3)*
C10	0.70458 (10)	0.03210 (7)	0.54052 (6)	0.01022 (14)
O10	0.62541 (9)	0.10516 (6)	0.49343 (5)	0.01353 (12)
N1	0.80422 (10)	−0.04331 (7)	0.49985 (6)	0.01468 (14)
H1N1	0.8118 (19)	−0.0418 (15)	0.4408 (12)	0.029 (4)*
H2N1	0.8620 (19)	−0.0933 (14)	0.5309 (11)	0.025 (4)*
N2	0.68951 (11)	0.02366 (8)	0.63262 (5)	0.01455 (14)
H1N2	0.6409 (19)	0.0710 (14)	0.6591 (11)	0.024 (4)*
H2N2	0.7551 (17)	−0.0164 (12)	0.6624 (10)	0.015 (3)*
O1w	0.52632 (10)	0.38305 (7)	0.82537 (6)	0.01888 (14)
H1w	0.525 (2)	0.3183 (18)	0.7982 (13)	0.040 (5)*
H2w	0.446 (2)	0.4165 (17)	0.8107 (14)	0.044 (5)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Na	0.01482 (17)	0.01116 (16)	0.00787 (15)	0.00170 (12)	−0.00024 (12)	−0.00026 (12)
C11	0.0133 (4)	0.0106 (3)	0.0100 (3)	0.0028 (3)	0.0002 (3)	0.0001 (3)
O11	0.0253 (4)	0.0152 (3)	0.0102 (3)	0.0108 (3)	−0.0019 (2)	−0.0001 (2)
O21	0.0267 (4)	0.0168 (3)	0.0094 (3)	0.0103 (3)	−0.0003 (3)	−0.0023 (2)
C31	0.0123 (3)	0.0105 (3)	0.0086 (3)	0.0016 (3)	−0.0012 (3)	0.0007 (3)
O13	0.0239 (4)	0.0146 (3)	0.0099 (3)	0.0098 (3)	−0.0040 (2)	−0.0013 (2)
O23	0.0209 (3)	0.0170 (3)	0.0072 (2)	0.0064 (2)	−0.0019 (2)	−0.0010 (2)
S	0.01068 (9)	0.00793 (8)	0.00578 (8)	−0.00079 (6)	−0.00021 (6)	−0.00002 (6)
O15	0.0159 (3)	0.0108 (3)	0.0078 (2)	0.0009 (2)	−0.0006 (2)	0.0024 (2)
O25	0.0123 (3)	0.0130 (3)	0.0110 (3)	0.0022 (2)	0.0021 (2)	0.0002 (2)
O35	0.0169 (3)	0.0122 (3)	0.0094 (2)	−0.0054 (2)	−0.0011 (2)	−0.0012 (2)
C1	0.0118 (3)	0.0101 (3)	0.0082 (3)	0.0020 (3)	0.0002 (3)	−0.0004 (3)
C2	0.0124 (3)	0.0106 (3)	0.0078 (3)	0.0019 (3)	−0.0002 (3)	−0.0006 (3)
C3	0.0111 (3)	0.0094 (3)	0.0074 (3)	0.0012 (3)	−0.0012 (2)	0.0002 (3)
C4	0.0113 (3)	0.0093 (3)	0.0083 (3)	0.0011 (3)	−0.0009 (3)	−0.0003 (3)
C5	0.0100 (3)	0.0093 (3)	0.0068 (3)	−0.0006 (2)	−0.0006 (2)	−0.0008 (3)
C6	0.0115 (3)	0.0097 (3)	0.0081 (3)	0.0012 (3)	−0.0009 (3)	0.0002 (3)
C10	0.0109 (3)	0.0104 (3)	0.0093 (3)	0.0011 (3)	−0.0002 (3)	0.0003 (3)
O10	0.0172 (3)	0.0131 (3)	0.0102 (3)	0.0062 (2)	−0.0012 (2)	0.0011 (2)
N1	0.0174 (4)	0.0157 (3)	0.0110 (3)	0.0074 (3)	0.0018 (3)	0.0007 (3)
N2	0.0169 (4)	0.0185 (4)	0.0083 (3)	0.0067 (3)	0.0009 (3)	0.0012 (3)
O1w	0.0173 (3)	0.0161 (3)	0.0231 (4)	−0.0006 (3)	−0.0062 (3)	−0.0060 (3)

Geometric parameters (Å, º)

Na—O21	2.3223 (9)	C2—C3	1.3971 (12)
Na—O23^i	2.3065 (9)	C2—H2	0.911 (15)
Na—O15^ii	2.4465 (9)	C3—C4	1.3948 (12)
Na—O35^iii	2.4230 (9)	C3—C31	1.4906 (12)
Na—O10	2.3362 (9)	C4—C5	1.3991 (12)
Na—N2^iv	2.7869 (12)	C4—H4	0.952 (15)
C11—O21	1.2205 (11)	C5—C6	1.3900 (12)
C11—O11	1.3153 (11)	C5—S	1.7736 (9)
O11—H1	0.841 (19)	C6—H6	0.974 (14)
C31—O23	1.2166 (11)	C10—O10	1.2602 (11)
C31—O13	1.3320 (11)	C10—N1	1.3400 (12)
O13—H3	0.84 (2)	C10—N2	1.3501 (12)
S—O25	1.4556 (8)	N1—H1N1	0.862 (17)
S—O15	1.4652 (7)	N1—H2N1	0.869 (17)
S—O35	1.4675 (8)	N2—H1N2	0.783 (17)
C1—C2	1.3914 (12)	N2—H2N2	0.826 (14)
C1—C6	1.3975 (12)	O1w—H1w	0.85 (2)
C1—C11	1.4953 (13)	O1w—H2w	0.79 (2)
O21—Na—O15^ii	171.69 (3)	C2—C1—C6	120.30 (8)
O21—Na—O35^iii	88.31 (4)	C2—C1—C11	118.73 (8)
O21—Na—O10	81.98 (3)	C6—C1—C11	120.96 (8)
O21—Na—N2^iv	93.44 (4)	C1—C2—C3	119.90 (8)
O23^i—Na—O21	98.46 (3)	C1—C2—H2	119.6 (9)
O23^i—Na—O15^ii	89.63 (3)	C3—C2—H2	120.5 (9)
O23^i—Na—O35^iii	80.69 (3)	C2—C3—C31	117.12 (8)
O23^i—Na—O10	159.48 (3)	C4—C3—C2	120.52 (8)
O23^i—Na—N2^iv	74.52 (3)	C4—C3—C31	122.29 (8)
O15^ii—Na—N2^iv	86.88 (4)	C3—C4—C5	118.78 (8)
O35^iii—Na—O15^ii	94.88 (4)	C3—C4—H4	119.9 (9)
O35^iii—Na—N2^iv	155.14 (3)	C5—C4—H4	121.3 (9)
O10—Na—O15^ii	89.79 (3)	C4—C5—S	118.81 (7)
O10—Na—O35^iii	119.79 (3)	C6—C5—C4	121.29 (8)
O10—Na—N2^iv	84.96 (3)	C6—C5—S	119.90 (6)
O11—C11—C1	113.45 (8)	C1—C6—H6	119.4 (8)
O21—C11—C1	121.86 (8)	C5—C6—C1	119.21 (8)
O21—C11—O11	124.69 (8)	C5—C6—H6	121.4 (8)
C11—O11—H1	108.3 (13)	O10—C10—N1	120.62 (8)
C11—O21—Na	132.68 (6)	O10—C10—N2	122.10 (8)
O13—C31—C3	114.59 (7)	N1—C10—N2	117.24 (8)
O23—C31—C3	122.20 (8)	C10—O10—Na	139.33 (6)
O23—C31—O13	123.17 (8)	C10—N1—H1N1	118.8 (11)
C31—O13—H3	104.6 (13)	C10—N1—H2N1	122.3 (11)
C31—O23—Na^v	138.44 (7)	H1N1—N1—H2N1	118.9 (15)
O15—S—C5	106.59 (4)	Na^iv—N2—H1N2	92.2 (12)
O15—S—O35	111.75 (4)	Na^iv—N2—H2N2	90.0 (10)
O25—S—C5	106.04 (4)	C10—N2—Na^iv	105.62 (6)
O25—S—O15	113.38 (4)	C10—N2—H1N2	119.6 (12)
O25—S—O35	112.54 (5)	C10—N2—H2N2	119.3 (10)
O35—S—C5	105.89 (4)	H1N2—N2—H2N2	117.8 (15)
S—O15—Na^vi	128.87 (4)	H1w—O1w—H2w	107.8 (18)
S—O35—Na^iii	141.44 (4)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O11—H1···O10	0.841 (19)	1.714 (19)	2.5495 (11)	171.9 (19)
O13—H3···O35^vii	0.84 (2)	1.87 (2)	2.7052 (11)	173 (2)
N1—H1N1···O15^ii	0.862 (17)	2.275 (17)	3.0881 (13)	157.3 (14)
N1—H2N1···O1w^viii	0.869 (16)	2.282 (17)	2.9974 (13)	139.6 (14)
N2—H1N2···O25^ix	0.783 (17)	2.192 (17)	2.9463 (12)	161.8 (16)
N2—H2N2···O1w^viii	0.826 (14)	2.142 (14)	2.8984 (14)	152.1 (13)
O1w—H1w···O25^ix	0.85 (2)	2.00 (2)	2.8252 (13)	165.5 (17)
O1w—H2w···O15	0.79 (2)	2.17 (2)	2.9461 (13)	171.1 (19)

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