Acta Cryst. (2009). E65, m213-m214 [ doi:10.1107/S1600536809002001 ]
![[mu]](/logos/entities/mu_rmgif.gif)
2-3-carboxypyrazine-2-carboxylato)(2-pyrazine-2,3-dicarboxylic acid)]The structural unit of the title compound, [Rb(C6H3N2O4)(C6H4N2O4)(H2O)2]n, consists of one rubidium cation, one hydrogen pyrazine-2,3-dicarboxylate anion, one pyrazine-2,3-dicarboxylic acid molecule and two water molecules. This formulation is repeated twice in the asymmetric unit as the rubidium cation lies on an inversion centre. Each anion or acid molecule is linked to two rubidium cations, while the rubidium cation has close contacts to four symmetry-equivalent organic ligands, with two different coordination modes towards this cation. In addition, each rubidium cation is coordinated by two water O atoms, raising the coordination number to eight. One of the carboxyl groups of the acid holds its H atom, which forms a hydrogen bond to a coordinated water molecule. The other carboxyl group is deprotonated in half of the ligands and protonated in the other half, taking part in a strong O-H
O hydrogen bond disordered over an inversion centre. The stabilization of the crystal structure is further assisted by O-HO and O-HN hydrogen-bonding interactions involving the water molecules and carboxylate O atoms.
Rb~2~CO~3~ (462 mg, 2 mmol) was carefully added to an aqueous solution (20 ml) of pyrazine 2,3-dicarboxylic acid (672 mg, 4 mmol), until no further bubbles formed. The reaction mixture produced a colourless and clear solution which was stirred at 323 K for 200 min., until it solidified. The solid product was then redissolved in water (5 ml) and allowed to stand for three days at ambient temperature, after which transparent fine crystals were harvested.
The H5A atom of water molecule was located in a difference map. The position of H5B atom was obtained from difference map and then its position was refined with riding constraint.The other hydyrogen atoms (H1, H2, H3, H4) were repositioned geometrically. (C—H = 0.93 Å, O—H = 0.93 Å and O—H = 0.82 Å) and U\ĩso\~(H) (in the range 1.2–1.5 times U\~eq\~ of the parent atom).
Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1997); cell refinement: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1997); data reduction: TEXSAN for Windows (Molecular Structure Corporation, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: publCIF (Westrip, 2009).
![[Figure 1]](./hg2450fig1thm.gif)
| Fig. 1. A perspective view diagram of the structure of (I) together with asymmetric units. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) 1 - x, 1 - y, -z, (ii) 1 + x, y - 1, z, (iii) -x + 2, -y, -z, (vii) x - 1, y + 1, z]. |
![[Figure 2]](./hg2450fig2thm.gif)
| Fig. 2. Hydrogen bongd diagram of (I). Dashed lines indicate hydrogen bonds. (H atoms of carbons were ommited for clarity). |
| [Rb(C6H3N2O4)(C6H4N2O4)(H2O)2] | Z = 1 |
| Mr = 456.72 | F(000) = 228 |
| Triclinic, P1 | Dx = 1.830 Mg m−3 |
| Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
| a = 7.452 (2) Å | Cell parameters from 25 reflections |
| b = 7.8640 (15) Å | θ = 2.6–9.2° |
| c = 8.3280 (12) Å | µ = 3.05 mm−1 |
| α = 69.111 (12)° | T = 298 K |
| β = 81.424 (19)° | Prism, colourless |
| γ = 65.322 (18)° | 0.20 × 0.15 × 0.06 mm |
| V = 414.32 (16) Å3 |
| Rigaku AFC-7S diffractometer | 1604 reflections with I > 2σ(I) |
| Radiation source: fine-focus sealed tube | Rint = 0.048 |
| graphite | θmax = 40.0°, θmin = 2.6° |
| ω–2θ scans | h = −13→13 |
| Absorption correction: numerical (Clark & Reid, 1995) | k = −12→13 |
| Tmin = 0.581, Tmax = 0.838 | l = 0→15 |
| 5329 measured reflections | 3 standard reflections every 150 reflections |
| 5057 independent reflections | intensity decay: none |
| 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)] = 0.053 | H atoms treated by a mixture of independent and constrained refinement |
| wR(F2) = 0.219 | w = 1/[σ2(Fo2) + (0.0711P)2 + 0.5448P] where P = (Fo2 + 2Fc2)/3 |
| S = 0.98 | (Δ/σ)max = 0.002 |
| 5057 reflections | Δρmax = 1.35 e Å−3 |
| 133 parameters | Δρmin = −1.91 e Å−3 |
| 1 restraint | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
| Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.093 (11) |
| [Rb(C6H3N2O4)(C6H4N2O4)(H2O)2] | γ = 65.322 (18)° |
| Mr = 456.72 | V = 414.32 (16) Å3 |
| Triclinic, P1 | Z = 1 |
| a = 7.452 (2) Å | Mo Kα radiation |
| b = 7.8640 (15) Å | µ = 3.05 mm−1 |
| c = 8.3280 (12) Å | T = 298 K |
| α = 69.111 (12)° | 0.20 × 0.15 × 0.06 mm |
| β = 81.424 (19)° |
| Rigaku AFC-7S diffractometer | 1604 reflections with I > 2σ(I) |
| Absorption correction: numerical (Clark & Reid, 1995) | Rint = 0.048 |
| Tmin = 0.581, Tmax = 0.838 | θmax = 40.0° |
| 5329 measured reflections | 3 standard reflections every 150 reflections |
| 5057 independent reflections | intensity decay: none |
| R[F2 > 2σ(F2)] = 0.053 | H atoms treated by a mixture of independent and constrained refinement |
| wR(F2) = 0.219 | Δρmax = 1.35 e Å−3 |
| S = 0.98 | Δρmin = −1.91 e Å−3 |
| 5057 reflections | Absolute structure: ? |
| 133 parameters | Flack parameter: ? |
| 1 restraint | Rogers parameter: ? |
Experimental. [analytical numeric absorption correction using a multifaceted crystal model based on expressions derived (Clark & Reid, 1995)] |
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. |
| x | y | z | Uiso*/Ueq | Occ. (<1) | |
| Rb1 | 1.0000 | 0.0000 | 0.0000 | 0.0474 (3) | |
| O1 | 0.9512 (4) | 0.1940 (5) | 0.2826 (4) | 0.0451 (7) | |
| O2 | 0.8035 (5) | 0.3205 (6) | 0.4927 (4) | 0.0555 (9) | |
| H2 | 0.9157 | 0.2906 | 0.5229 | 0.083* | |
| O3 | 0.4264 (4) | 0.8765 (4) | 0.0673 (4) | 0.0472 (7) | |
| H1 | 0.4742 | 0.9762 | 0.0256 | 0.071* | 0.50 |
| O4 | 0.7256 (4) | 0.6622 (5) | 0.1716 (5) | 0.0497 (8) | |
| O5 | 0.8582 (5) | −0.1900 (5) | 0.3618 (5) | 0.0520 (8) | |
| N1 | 0.5456 (5) | 0.1950 (5) | 0.3236 (4) | 0.0367 (7) | |
| N2 | 0.2959 (4) | 0.5834 (5) | 0.1521 (4) | 0.0333 (6) | |
| C1 | 0.8065 (5) | 0.2816 (5) | 0.3520 (5) | 0.0335 (7) | |
| C2 | 0.6004 (5) | 0.3460 (5) | 0.2892 (4) | 0.0307 (7) | |
| C3 | 0.3632 (6) | 0.2399 (6) | 0.2753 (5) | 0.0390 (8) | |
| H3 | 0.3190 | 0.1392 | 0.2980 | 0.047* | |
| C4 | 0.2388 (6) | 0.4346 (6) | 0.1918 (5) | 0.0372 (8) | |
| H4 | 0.1117 | 0.4612 | 0.1629 | 0.045* | |
| C5 | 0.4790 (5) | 0.5392 (5) | 0.1997 (4) | 0.0297 (7) | |
| C6 | 0.5508 (6) | 0.7044 (5) | 0.1459 (5) | 0.0344 (8) | |
| H5A | 0.761 (12) | −0.087 (12) | 0.364 (10) | 0.10 (3)* | |
| H5B | 0.816 (8) | −0.243 (8) | 0.316 (6) | 0.057 (16)* |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Rb1 | 0.0433 (4) | 0.0367 (3) | 0.0434 (4) | −0.0028 (2) | −0.0063 (2) | −0.0051 (2) |
| O1 | 0.0316 (14) | 0.0510 (17) | 0.0607 (19) | −0.0160 (13) | −0.0025 (13) | −0.0265 (15) |
| O2 | 0.0423 (16) | 0.079 (2) | 0.0460 (17) | −0.0112 (16) | −0.0128 (13) | −0.0312 (17) |
| O3 | 0.0395 (15) | 0.0302 (13) | 0.069 (2) | −0.0180 (12) | −0.0093 (14) | −0.0036 (13) |
| O4 | 0.0393 (15) | 0.0428 (16) | 0.075 (2) | −0.0207 (13) | −0.0172 (14) | −0.0157 (15) |
| O5 | 0.0471 (18) | 0.0489 (18) | 0.066 (2) | −0.0120 (15) | −0.0233 (15) | −0.0253 (16) |
| N1 | 0.0360 (16) | 0.0293 (14) | 0.0426 (17) | −0.0139 (12) | −0.0078 (13) | −0.0053 (12) |
| N2 | 0.0290 (14) | 0.0350 (15) | 0.0375 (16) | −0.0144 (12) | −0.0070 (12) | −0.0088 (12) |
| C1 | 0.0304 (17) | 0.0321 (17) | 0.0395 (19) | −0.0143 (14) | −0.0057 (14) | −0.0089 (14) |
| C2 | 0.0299 (16) | 0.0340 (17) | 0.0304 (17) | −0.0148 (14) | −0.0030 (13) | −0.0093 (13) |
| C3 | 0.040 (2) | 0.0370 (19) | 0.046 (2) | −0.0223 (16) | −0.0045 (16) | −0.0094 (16) |
| C4 | 0.0324 (17) | 0.043 (2) | 0.041 (2) | −0.0219 (16) | −0.0042 (15) | −0.0096 (16) |
| C5 | 0.0307 (16) | 0.0325 (16) | 0.0300 (16) | −0.0147 (13) | −0.0050 (13) | −0.0100 (13) |
| C6 | 0.0397 (19) | 0.0314 (17) | 0.0400 (19) | −0.0200 (15) | −0.0049 (15) | −0.0113 (14) |
| Rb1—O3i | 2.987 (3) | O4—C6 | 1.234 (5) |
| Rb1—O3ii | 2.987 (3) | O5—H5A | 0.84 (9) |
| Rb1—N2ii | 3.007 (3) | O5—H5B | 0.82 (6) |
| Rb1—N2i | 3.007 (3) | N1—C2 | 1.336 (5) |
| Rb1—O5 | 3.096 (4) | N1—C3 | 1.340 (5) |
| Rb1—O5iii | 3.096 (4) | N2—C4 | 1.326 (5) |
| Rb1—O1iii | 3.137 (3) | N2—C5 | 1.344 (4) |
| Rb1—O1 | 3.137 (3) | N2—Rb1iv | 3.007 (3) |
| Rb1—H5B | 3.16 (5) | C1—C2 | 1.513 (5) |
| O1—C1 | 1.204 (5) | C2—C5 | 1.389 (5) |
| O2—C1 | 1.307 (5) | C3—C4 | 1.391 (6) |
| O2—H2 | 0.8210 | C3—H3 | 0.9300 |
| O3—C6 | 1.274 (5) | C4—H4 | 0.9300 |
| O3—Rb1iv | 2.987 (3) | C5—C6 | 1.506 (5) |
| O3—H1 | 0.9299 | ||
| O3i—Rb1—O3ii | 180.00 (14) | O5iii—Rb1—H5B | 165.0 (3) |
| O3i—Rb1—N2ii | 126.56 (8) | O1iii—Rb1—H5B | 104.1 (4) |
| O3ii—Rb1—N2ii | 53.44 (8) | O1—Rb1—H5B | 76.0 (10) |
| O3i—Rb1—N2i | 53.44 (8) | C1—O1—Rb1 | 131.4 (2) |
| O3ii—Rb1—N2i | 126.56 (8) | C1—O2—H2 | 111.2 |
| N2ii—Rb1—N2i | 180.0 | C6—O3—Rb1iv | 128.1 (2) |
| O3i—Rb1—O5 | 78.94 (9) | C6—O3—H1 | 116.0 |
| O3ii—Rb1—O5 | 101.06 (9) | Rb1iv—O3—H1 | 115.9 |
| N2ii—Rb1—O5 | 70.89 (9) | Rb1—O5—H5A | 95 (5) |
| N2i—Rb1—O5 | 109.11 (9) | Rb1—O5—H5B | 87 (4) |
| O3i—Rb1—O5iii | 101.06 (9) | H5A—O5—H5B | 104 (6) |
| O3ii—Rb1—O5iii | 78.94 (9) | C2—N1—C3 | 116.8 (3) |
| N2ii—Rb1—O5iii | 109.11 (9) | C4—N2—C5 | 117.1 (3) |
| N2i—Rb1—O5iii | 70.89 (9) | C4—N2—Rb1iv | 119.0 (2) |
| O5—Rb1—O5iii | 180.00 (13) | C5—N2—Rb1iv | 123.5 (2) |
| O3i—Rb1—O1iii | 81.24 (8) | O1—C1—O2 | 126.2 (3) |
| O3ii—Rb1—O1iii | 98.76 (8) | O1—C1—C2 | 121.8 (3) |
| N2ii—Rb1—O1iii | 76.07 (8) | O2—C1—C2 | 111.8 (3) |
| N2i—Rb1—O1iii | 103.93 (8) | N1—C2—C5 | 121.9 (3) |
| O5—Rb1—O1iii | 118.29 (9) | N1—C2—C1 | 113.0 (3) |
| O5iii—Rb1—O1iii | 61.71 (9) | C5—C2—C1 | 125.1 (3) |
| O3i—Rb1—O1 | 98.76 (8) | N1—C3—C4 | 121.2 (3) |
| O3ii—Rb1—O1 | 81.24 (8) | N1—C3—H3 | 119.4 |
| N2ii—Rb1—O1 | 103.93 (8) | C4—C3—H3 | 119.4 |
| N2i—Rb1—O1 | 76.07 (8) | N2—C4—C3 | 122.0 (3) |
| O5—Rb1—O1 | 61.71 (9) | N2—C4—H4 | 119.0 |
| O5iii—Rb1—O1 | 118.29 (9) | C3—C4—H4 | 119.0 |
| O1iii—Rb1—O1 | 180.00 (14) | N2—C5—C2 | 120.9 (3) |
| O3i—Rb1—H5B | 70.4 (9) | N2—C5—C6 | 117.8 (3) |
| O3ii—Rb1—H5B | 109.6 (9) | C2—C5—C6 | 121.2 (3) |
| N2ii—Rb1—H5B | 69.3 (10) | O4—C6—O3 | 125.3 (3) |
| N2i—Rb1—H5B | 110.7 (10) | O4—C6—C5 | 118.4 (3) |
| O5—Rb1—H5B | 15.1 (10) | O3—C6—C5 | 116.1 (3) |
| O3i—Rb1—O1—C1 | 4.0 (4) | Rb1iv—N2—C4—C3 | −174.7 (3) |
| O3ii—Rb1—O1—C1 | −176.0 (4) | N1—C3—C4—N2 | 1.8 (7) |
| N2ii—Rb1—O1—C1 | −127.2 (4) | C4—N2—C5—C2 | −1.2 (5) |
| N2i—Rb1—O1—C1 | 52.8 (4) | Rb1iv—N2—C5—C2 | 171.6 (3) |
| O5—Rb1—O1—C1 | −68.3 (4) | C4—N2—C5—C6 | 176.2 (3) |
| O5iii—Rb1—O1—C1 | 111.7 (4) | Rb1iv—N2—C5—C6 | −11.0 (4) |
| Rb1—O1—C1—O2 | 164.6 (3) | N1—C2—C5—N2 | 3.7 (6) |
| Rb1—O1—C1—C2 | −10.4 (6) | C1—C2—C5—N2 | −178.5 (3) |
| C3—N1—C2—C5 | −3.4 (6) | N1—C2—C5—C6 | −173.6 (3) |
| C3—N1—C2—C1 | 178.7 (3) | C1—C2—C5—C6 | 4.2 (6) |
| O1—C1—C2—N1 | 72.3 (5) | Rb1iv—O3—C6—O4 | −179.2 (3) |
| O2—C1—C2—N1 | −103.3 (4) | Rb1iv—O3—C6—C5 | 5.3 (5) |
| O1—C1—C2—C5 | −105.6 (5) | N2—C5—C6—O4 | −171.9 (4) |
| O2—C1—C2—C5 | 78.8 (5) | C2—C5—C6—O4 | 5.5 (6) |
| C2—N1—C3—C4 | 0.7 (6) | N2—C5—C6—O3 | 3.9 (5) |
| C5—N2—C4—C3 | −1.5 (6) | C2—C5—C6—O3 | −178.7 (4) |
| Symmetry codes: (i) −x+1, −y+1, −z; (ii) x+1, y−1, z; (iii) −x+2, −y, −z; (iv) x−1, y+1, z. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| O3—H1···O3v | 0.93 | 1.55 (1) | 2.468 (3) | 170 (1) |
| O5—H5A···N1 | 0.84 (9) | 2.07 (9) | 2.888 (3) | 168 (7) |
| O5—H5B···O4vi | 0.82 (6) | 1.94 (6) | 2.753 (3) | 170 (1) |
| O2—H2···O5vii | 0.82 | 1.79 | 2.596 (6) | 166 (1) |
| Symmetry codes: (v) −x+1, −y+2, −z; (vi) x, y−1, z; (vii) −x+2, −y, −z+1. |
| Rb1—O3i | 2.987 (3) | Rb1—O5 | 3.096 (4) |
| Rb1—N2ii | 3.007 (3) | Rb1—O1 | 3.137 (3) |
| O3i—Rb1—N2ii | 126.56 (8) | O5—Rb1—O1iii | 118.29 (9) |
| O3i—Rb1—O5 | 78.94 (9) | O3i—Rb1—O1 | 98.76 (8) |
| N2ii—Rb1—O5 | 70.89 (9) | N2i—Rb1—O1 | 76.07 (8) |
| O3i—Rb1—O1iii | 81.24 (8) | O5—Rb1—O1 | 61.71 (9) |
| N2ii—Rb1—O1iii | 76.07 (8) |
| Symmetry codes: (i) −x+1, −y+1, −z; (ii) x+1, y−1, z; (iii) −x+2, −y, −z. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| O3—H1···O3iv | 0.93 | 1.55 (1) | 2.468 (3) | 170 (1) |
| O5—H5A···N1 | 0.84 (9) | 2.07 (9) | 2.888 (3) | 168 (7) |
| O5—H5B···O4v | 0.82 (6) | 1.94 (6) | 2.753 (3) | 170 (1) |
| O2—H2···O5vi | 0.82 | 1.79 | 2.596 (6) | 166 (1) |
| Symmetry codes: (iv) −x+1, −y+2, −z; (v) x, y−1, z; (vi) −x+2, −y, −z+1. |
The authors gratefully acknowledge Kırıkkale University Scientific Research Centre for financial support of this work.
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Pyrazine-2,3-dicarboxylic acid (Takusagawa & Shimada, 1973) and its dianion (Richard et al., 1973; Nepveu et al., 1993) have been reported to be well suited for the construction of multidimensional frameworks (nD, n = 1–3), owing to the presence of two adjacent carboxylate groups (O donor atoms) as substituents on the N-heterocyclic pyrazine ring (N donor atoms). In recent years, a variety of metal-organic compound of pyrazine-2,3-dicarboxylic acid have been characterized crystallographically owing to growing interest in supramolecular chemistry. Examples are including the calcium (Ptasiewicz-Bak & Leciejewicz, 1997a; Starosta & Leciejewicz, 2005), magnesium (Ptasiewicz-Bak & Leciejewicz, 1997b), sodium (Tombul et al., 2006), caesium (Tombul et al., 2007) and potassium (Tombul et al., 2008a) and lithium (Tombul et al., 2008b) complexes. Continuation our research on Group I dicarboxylates, we present here the synthesis and crystal structure of the hydrated polymeric rubidium complex, (I), formed with pyrazine-2,3-dicarboxylic acid.
The structural unit of the title compound, (I), contains one rubidium cation, one hydrogen pyrazine-2,3-dicarboxylate anion, one pyrazine-2,3-dicarboxylic acid molecule and two water molecules; this is twice in the asymmetric unit, since the rubidium ion lies on an inversion centre. This compound is isostructural with the corresponding potassium and caesium complexes, which are fully described previously (Tombul et al., 2008a; Tombul et al., 2007). Pyrazine-2,3-dicarboxylic acid is, on average, only half deprotonated at one of the carboxylate groups (O3ii and O3iii) complete the charge balance of the cation. Taking a larger domain of the crystal structure, the anion or acid molecule is linked to two rubidium cations, while the Rb+ cation is surrounded by four organic ligands, two of which are coordinated by employing both N and O atoms and the other two are coordinated solely by O atoms. In addition, each rubidium cation is coordinated by two water molecules, raising a coordination number of eight. The inner coordination sphere accommodates comprises six oxygen atoms (O1, O1i, O3ii, O3iii, O5 and O5i), together with two nitrogen atoms (N2ii and N2iii). The planes of the carboxylic/carboxylate groups (O1/C1/C2/O2) and (O3/C6/C5/O4) form dihedral angles with the ring (C2/C3/C4/C5/N1/N2) plane of 75.87 (16) and 6.65 (21), respectively. The Rb—O distances are in the range from 2.987 (3) Å to 3.137 (3) Å, which are well within the range reported in the literature for other rubidium complexes (Yang et al. 2008; Cametti et al., 2005; Wiesbrock & Schmidbaur, 2003; Shannon, 1976; Devi & Vidyasagar, 2000). Rb—N bond lengths also lie within the normal ranges found for similar bonds in the literature (Yang et al. 2008).
In the crystal structure, an asymmetric strong hydrogen bond occurs, linking carboxylate O atoms O—H···O [O···O = 2.468 (3) 2.596 (2) Å respectively]. Atom H1 is involved in this bond and maintains the charge balance within the structure. The water molecules are involved in normal, slightly bent, hydrogen bonds with hydrogen pyrazine-2,3-dicarboxylate (Table 2); the acceptors are carboxylate O atoms and N atoms of the aromatic ring. The polymeric complex is linked in a three-dimensional manner by further numerous intermolecular O—H···O and O—H···N hydrogen bonds (Fig. 2 and Table 2)