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.
Supporting information
CCDC reference: 235315
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.
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.
Poly[sodium-µ
4-3,5-dicarboxybenzenesulfonate-
κ4O:
O':
O'':
O'''-µ
2-urea-
κ2O:
N] monohydrate]
top
Crystal data top
[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) Å3 | 0.3 × 0.3 × 0.3 mm |
Z = 4 | |
Data collection top
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 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)] = 0.035 | All H-atom parameters refined |
wR(F2) = 0.091 | w = 1/[σ2(Fo2) + (0.0469P)2 + 0.1356P] where P = (Fo2 + 2Fc2)/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+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0033 (9) |
Crystal data top
[Na(C8H5O7S)(CH4N2O)]·H2O | V = 1378.7 (8) Å3 |
Mr = 346.26 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 8.203 (3) Å | µ = 0.32 mm−1 |
b = 11.566 (4) Å | T = 100 K |
c = 14.534 (4) Å | 0.3 × 0.3 × 0.3 mm |
β = 91.025 (3)° | |
Data collection top
Kuma KM-4 CCD area-detector diffractometer | 5744 reflections with I > 2σ(I) |
22990 measured reflections | Rint = 0.024 |
6900 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.035 | 0 restraints |
wR(F2) = 0.091 | All H-atom parameters refined |
S = 1.10 | Δρmax = 0.57 e Å−3 |
6900 reflections | Δρmin = −0.50 e Å−3 |
244 parameters | |
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 | |
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 (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
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) top
Na—O21 | 2.3223 (9) | C2—C3 | 1.3971 (12) |
Na—O23i | 2.3065 (9) | C2—H2 | 0.911 (15) |
Na—O15ii | 2.4465 (9) | C3—C4 | 1.3948 (12) |
Na—O35iii | 2.4230 (9) | C3—C31 | 1.4906 (12) |
Na—O10 | 2.3362 (9) | C4—C5 | 1.3991 (12) |
Na—N2iv | 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—O15ii | 171.69 (3) | C2—C1—C6 | 120.30 (8) |
O21—Na—O35iii | 88.31 (4) | C2—C1—C11 | 118.73 (8) |
O21—Na—O10 | 81.98 (3) | C6—C1—C11 | 120.96 (8) |
O21—Na—N2iv | 93.44 (4) | C1—C2—C3 | 119.90 (8) |
O23i—Na—O21 | 98.46 (3) | C1—C2—H2 | 119.6 (9) |
O23i—Na—O15ii | 89.63 (3) | C3—C2—H2 | 120.5 (9) |
O23i—Na—O35iii | 80.69 (3) | C2—C3—C31 | 117.12 (8) |
O23i—Na—O10 | 159.48 (3) | C4—C3—C2 | 120.52 (8) |
O23i—Na—N2iv | 74.52 (3) | C4—C3—C31 | 122.29 (8) |
O15ii—Na—N2iv | 86.88 (4) | C3—C4—C5 | 118.78 (8) |
O35iii—Na—O15ii | 94.88 (4) | C3—C4—H4 | 119.9 (9) |
O35iii—Na—N2iv | 155.14 (3) | C5—C4—H4 | 121.3 (9) |
O10—Na—O15ii | 89.79 (3) | C4—C5—S | 118.81 (7) |
O10—Na—O35iii | 119.79 (3) | C6—C5—C4 | 121.29 (8) |
O10—Na—N2iv | 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—Nav | 138.44 (7) | H1N1—N1—H2N1 | 118.9 (15) |
O15—S—C5 | 106.59 (4) | Naiv—N2—H1N2 | 92.2 (12) |
O15—S—O35 | 111.75 (4) | Naiv—N2—H2N2 | 90.0 (10) |
O25—S—C5 | 106.04 (4) | C10—N2—Naiv | 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—Navi | 128.87 (4) | H1w—O1w—H2w | 107.8 (18) |
S—O35—Naiii | 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) top
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···O35vii | 0.84 (2) | 1.87 (2) | 2.7052 (11) | 173 (2) |
N1—H1N1···O15ii | 0.862 (17) | 2.275 (17) | 3.0881 (13) | 157.3 (14) |
N1—H2N1···O1wviii | 0.869 (16) | 2.282 (17) | 2.9974 (13) | 139.6 (14) |
N2—H1N2···O25ix | 0.783 (17) | 2.192 (17) | 2.9463 (12) | 161.8 (16) |
N2—H2N2···O1wviii | 0.826 (14) | 2.142 (14) | 2.8984 (14) | 152.1 (13) |
O1w—H1w···O25ix | 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. |
Experimental details
Crystal data |
Chemical formula | [Na(C8H5O7S)(CH4N2O)]·H2O |
Mr | 346.26 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 100 |
a, b, c (Å) | 8.203 (3), 11.566 (4), 14.534 (4) |
β (°) | 91.025 (3) |
V (Å3) | 1378.7 (8) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.32 |
Crystal size (mm) | 0.3 × 0.3 × 0.3 |
|
Data collection |
Diffractometer | Kuma KM-4 CCD area-detector diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 22990, 6900, 5744 |
Rint | 0.024 |
(sin θ/λ)max (Å−1) | 0.857 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.035, 0.091, 1.10 |
No. of reflections | 6900 |
No. of parameters | 244 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.57, −0.50 |
Selected geometric parameters (Å, º) topNa—O21 | 2.3223 (9) | Na—O35iii | 2.4230 (9) |
Na—O23i | 2.3065 (9) | Na—O10 | 2.3362 (9) |
Na—O15ii | 2.4465 (9) | Na—N2iv | 2.7869 (12) |
| | | |
O21—Na—O15ii | 171.69 (3) | O35iii—Na—O15ii | 94.88 (4) |
O21—Na—O35iii | 88.31 (4) | O35iii—Na—N2iv | 155.14 (3) |
O21—Na—O10 | 81.98 (3) | O10—Na—O15ii | 89.79 (3) |
O21—Na—N2iv | 93.44 (4) | O10—Na—O35iii | 119.79 (3) |
O23i—Na—O21 | 98.46 (3) | O10—Na—N2iv | 84.96 (3) |
O23i—Na—O15ii | 89.63 (3) | C10—O10—Na | 139.33 (6) |
O23i—Na—O35iii | 80.69 (3) | Naiv—N2—H1N2 | 92.2 (12) |
O23i—Na—O10 | 159.48 (3) | Naiv—N2—H2N2 | 90.0 (10) |
O23i—Na—N2iv | 74.52 (3) | C10—N2—Naiv | 105.62 (6) |
O15ii—Na—N2iv | 86.88 (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. |
Hydrogen-bond geometry (Å, º) top
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···O35v | 0.84 (2) | 1.87 (2) | 2.7052 (11) | 173 (2) |
N1—H1N1···O15ii | 0.862 (17) | 2.275 (17) | 3.0881 (13) | 157.3 (14) |
N1—H2N1···O1wvi | 0.869 (16) | 2.282 (17) | 2.9974 (13) | 139.6 (14) |
N2—H1N2···O25vii | 0.783 (17) | 2.192 (17) | 2.9463 (12) | 161.8 (16) |
N2—H2N2···O1wvi | 0.826 (14) | 2.142 (14) | 2.8984 (14) | 152.1 (13) |
O1w—H1w···O25vii | 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; (v) x−1/2, −y+3/2, z−1/2; (vi) −x+3/2, y−1/2, −z+3/2; (vii) −x+1/2, y−1/2, −z+3/2. |
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—N2iv 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.