L-Serinium semi-maleate, (I), and DL-serinium semi-maleate, (II), both C3H8NO3+·C4H3O4-, provide the first example of chiral and racemic anhydrous serine salts with the same organic anion. A comparison of their crystal structures with each other, with the structures of the pure components (L-serine polymorphs, DL-serine and maleic acid) and with other amino acid maleates is important for understanding the formation of the crystal structures, their response to variations in temperature and pressure, and structure-property relationships. As in other known crystal structures of amino acid maleates, there are no direct links between the semi-maleate anions in the two new structures. The serinium cations have different conformations in (I) and (II). In (I), they are linked into infinite chains via hydrogen bonds between carboxylic acid and hydroxy groups. In (II), there are no such chains formed by the serinium cations. In both (I) and (II), there are C22(12) chains consisting of alternating semi-maleate anions and serinium cations. Two types of such chains are present in (I) and (II), termed C22(12) and C22(12)'. In (I), these chains, lying in the same plane, are further linked to each other via hydrogen bonds, whereas in (II) they are not.
Supporting information
CCDC references: 950361; 950362
Crystals of L-serinium semi-maleate and DL-serinium semi-maleate
were obtained by slow evaporation at 298 K of aqueous solutions (ca
3–4 ml) containing L-serinium or DL-serinium and maleic acid in
a 1:1 ratio.
For both structures, H-atom positions were located from difference Fourier
maps. All H-atom positional and displacement parameters were allowed to refine
freely.
Data collection: X-AREA (Stoe & Cie, 2006) for (I); CrysAlis PRO (Agilent, 2012) for (II). Cell refinement: X-AREA (Stoe & Cie, 2006) for (I); CrysAlis PRO (Agilent, 2012) for (II). Data reduction: X-RED (Stoe & Cie, 2006) for (I); CrysAlis PRO (Agilent, 2012) for (II). For both compounds, program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: Mercury (Macrae et al., 2008), PLATON (Spek, 2009) and publCIF (Westrip, 2010).
(I)
L-Serinium semi-maleate
top
Crystal data top
C3H8NO3+·C4H3O4− | F(000) = 232 |
Mr = 221.17 | Dx = 1.555 Mg m−3 |
Monoclinic, P21 | Mo Kα radiation, λ = 0.71073 Å |
a = 6.9527 (11) Å | Cell parameters from 3393 reflections |
b = 6.5631 (10) Å | θ = 3.0–29.6° |
c = 10.4284 (19) Å | µ = 0.14 mm−1 |
β = 97.094 (14)° | T = 297 K |
V = 472.22 (13) Å3 | Block, colourless |
Z = 2 | 0.3 × 0.25 × 0.1 mm |
Data collection top
Stoe IPDS II diffractometer | 1905 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.021 |
Graphite monochromator | θmax = 29.1°, θmin = 3.0° |
Detector resolution: 6.67 pixels mm-1 | h = −9→9 |
rotation method scans | k = −8→8 |
3648 measured reflections | l = −14→12 |
2508 independent reflections | |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.039 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.070 | All H-atom parameters refined |
S = 0.93 | w = 1/[σ2(Fo2) + (0.0324P)2] where P = (Fo2 + 2Fc2)/3 |
2508 reflections | (Δ/σ)max < 0.001 |
180 parameters | Δρmax = 0.17 e Å−3 |
1 restraint | Δρmin = −0.16 e Å−3 |
Crystal data top
C3H8NO3+·C4H3O4− | V = 472.22 (13) Å3 |
Mr = 221.17 | Z = 2 |
Monoclinic, P21 | Mo Kα radiation |
a = 6.9527 (11) Å | µ = 0.14 mm−1 |
b = 6.5631 (10) Å | T = 297 K |
c = 10.4284 (19) Å | 0.3 × 0.25 × 0.1 mm |
β = 97.094 (14)° | |
Data collection top
Stoe IPDS II diffractometer | 1905 reflections with I > 2σ(I) |
3648 measured reflections | Rint = 0.021 |
2508 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.039 | 1 restraint |
wR(F2) = 0.070 | All H-atom parameters refined |
S = 0.93 | Δρmax = 0.17 e Å−3 |
2508 reflections | Δρmin = −0.16 e Å−3 |
180 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 | |
C1 | 0.4842 (2) | 0.3859 (3) | 0.78079 (16) | 0.0276 (4) | |
N1 | 0.7020 (2) | 0.5822 (3) | 0.93427 (16) | 0.0319 (4) | |
H1A | 0.649 (4) | 0.524 (4) | 1.003 (3) | 0.056 (7)* | |
H1B | 0.820 (3) | 0.619 (3) | 0.958 (2) | 0.033 (5)* | |
H1C | 0.627 (3) | 0.692 (3) | 0.915 (2) | 0.039 (6)* | |
O1 | 0.45363 (17) | 0.3166 (2) | 0.66314 (11) | 0.0389 (3) | |
H1 | 0.322 (4) | 0.298 (5) | 0.638 (3) | 0.090 (9)* | |
C2 | 0.6955 (2) | 0.4416 (3) | 0.82254 (17) | 0.0279 (4) | |
H2 | 0.745 (3) | 0.513 (3) | 0.752 (2) | 0.030 (5)* | |
O2 | 0.36375 (16) | 0.4045 (2) | 0.85386 (12) | 0.0410 (3) | |
C3 | 0.8156 (3) | 0.2522 (3) | 0.8626 (2) | 0.0335 (4) | |
H3A | 0.766 (3) | 0.185 (3) | 0.929 (2) | 0.027 (5)* | |
H3B | 0.818 (3) | 0.159 (4) | 0.790 (2) | 0.043 (6)* | |
O3 | 1.00479 (17) | 0.3089 (2) | 0.91449 (14) | 0.0416 (3) | |
H3 | 1.068 (3) | 0.328 (4) | 0.853 (2) | 0.060 (8)* | |
C4 | 1.0141 (2) | 0.2838 (3) | 0.49298 (18) | 0.0337 (4) | |
O4 | 1.09075 (18) | 0.2742 (2) | 0.60716 (13) | 0.0444 (3) | |
C5 | 0.7975 (2) | 0.2799 (3) | 0.47379 (18) | 0.0334 (4) | |
H5 | 0.747 (3) | 0.249 (3) | 0.547 (2) | 0.042 (6)* | |
O5 | 1.10934 (17) | 0.2963 (2) | 0.39725 (14) | 0.0464 (4) | |
C6 | 0.6730 (3) | 0.3141 (3) | 0.36890 (18) | 0.0344 (4) | |
H6 | 0.536 (3) | 0.309 (3) | 0.3789 (18) | 0.035 (5)* | |
O6 | 0.56920 (19) | 0.3966 (2) | 0.15278 (12) | 0.0456 (3) | |
C7 | 0.7101 (3) | 0.3600 (3) | 0.23456 (18) | 0.0355 (4) | |
O7 | 0.8833 (2) | 0.3607 (3) | 0.20481 (13) | 0.0527 (4) | |
H7 | 0.987 (5) | 0.321 (6) | 0.276 (3) | 0.106 (11)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
C1 | 0.0226 (7) | 0.0297 (9) | 0.0290 (8) | 0.0012 (7) | −0.0027 (6) | 0.0034 (8) |
N1 | 0.0205 (7) | 0.0361 (9) | 0.0366 (9) | −0.0007 (7) | −0.0058 (7) | −0.0023 (7) |
O1 | 0.0277 (6) | 0.0576 (9) | 0.0297 (7) | 0.0005 (6) | −0.0031 (5) | −0.0059 (6) |
C2 | 0.0217 (8) | 0.0338 (10) | 0.0277 (9) | −0.0009 (7) | 0.0014 (6) | 0.0044 (7) |
O2 | 0.0232 (6) | 0.0631 (9) | 0.0368 (7) | −0.0069 (6) | 0.0045 (5) | −0.0090 (7) |
C3 | 0.0244 (8) | 0.0384 (11) | 0.0370 (10) | 0.0050 (7) | 0.0009 (7) | 0.0012 (9) |
O3 | 0.0191 (5) | 0.0594 (9) | 0.0459 (7) | 0.0075 (6) | 0.0023 (5) | 0.0109 (7) |
C4 | 0.0292 (8) | 0.0307 (9) | 0.0393 (9) | −0.0027 (8) | −0.0031 (7) | −0.0016 (9) |
O4 | 0.0314 (6) | 0.0579 (9) | 0.0406 (7) | −0.0049 (6) | −0.0083 (5) | 0.0026 (7) |
C5 | 0.0283 (8) | 0.0413 (11) | 0.0309 (9) | −0.0034 (8) | 0.0042 (7) | 0.0024 (9) |
O5 | 0.0290 (6) | 0.0661 (9) | 0.0443 (8) | 0.0001 (7) | 0.0056 (6) | −0.0005 (8) |
C6 | 0.0276 (8) | 0.0395 (11) | 0.0356 (9) | −0.0045 (8) | 0.0014 (7) | 0.0011 (8) |
O6 | 0.0498 (8) | 0.0475 (8) | 0.0352 (7) | −0.0085 (7) | −0.0123 (6) | 0.0046 (7) |
C7 | 0.0419 (9) | 0.0315 (10) | 0.0311 (8) | −0.0092 (7) | −0.0035 (7) | −0.0015 (7) |
O7 | 0.0450 (8) | 0.0814 (12) | 0.0312 (7) | −0.0141 (8) | 0.0030 (6) | 0.0031 (8) |
Geometric parameters (Å, º) top
C1—O2 | 1.206 (2) | O3—H3 | 0.83 (2) |
C1—O1 | 1.301 (2) | C4—O4 | 1.245 (2) |
C1—C2 | 1.524 (2) | C4—O5 | 1.267 (2) |
N1—C2 | 1.483 (2) | C4—C5 | 1.495 (2) |
N1—H1A | 0.93 (3) | C5—C6 | 1.327 (3) |
N1—H1B | 0.86 (2) | C5—H5 | 0.90 (2) |
N1—H1C | 0.90 (2) | O5—H7 | 1.45 (4) |
O1—H1 | 0.93 (3) | C6—C7 | 1.486 (3) |
C2—C3 | 1.527 (2) | C6—H6 | 0.970 (18) |
C2—H2 | 0.97 (2) | O6—C7 | 1.240 (2) |
C3—O3 | 1.409 (2) | C7—O7 | 1.280 (2) |
C3—H3A | 0.93 (2) | O7—H7 | 1.00 (4) |
C3—H3B | 0.98 (2) | | |
| | | |
O2—C1—O1 | 125.85 (15) | O3—C3—H3B | 110.9 (13) |
O2—C1—C2 | 121.02 (15) | C2—C3—H3B | 111.2 (13) |
O1—C1—C2 | 113.13 (14) | H3A—C3—H3B | 109.2 (18) |
C2—N1—H1A | 111.8 (15) | C3—O3—H3 | 107.6 (17) |
C2—N1—H1B | 109.5 (14) | O4—C4—O5 | 123.59 (15) |
H1A—N1—H1B | 111 (2) | O4—C4—C5 | 115.63 (17) |
C2—N1—H1C | 111.1 (14) | O5—C4—C5 | 120.78 (16) |
H1A—N1—H1C | 103 (2) | C6—C5—C4 | 130.62 (18) |
H1B—N1—H1C | 110.2 (19) | C6—C5—H5 | 117.0 (13) |
C1—O1—H1 | 110.8 (19) | C4—C5—H5 | 112.4 (13) |
N1—C2—C1 | 107.97 (14) | C4—O5—H7 | 113.0 (12) |
N1—C2—C3 | 109.22 (15) | C5—C6—C7 | 129.76 (17) |
C1—C2—C3 | 111.00 (14) | C5—C6—H6 | 117.0 (12) |
N1—C2—H2 | 108.5 (11) | C7—C6—H6 | 113.3 (12) |
C1—C2—H2 | 108.5 (11) | O6—C7—O7 | 121.31 (18) |
C3—C2—H2 | 111.6 (11) | O6—C7—C6 | 118.22 (17) |
O3—C3—C2 | 110.06 (15) | O7—C7—C6 | 120.47 (16) |
O3—C3—H3A | 104.8 (12) | C7—O7—H7 | 115.7 (18) |
C2—C3—H3A | 110.4 (12) | | |
| | | |
O2—C1—C2—N1 | −20.8 (2) | O4—C4—C5—C6 | 170.0 (2) |
O1—C1—C2—N1 | 160.15 (15) | O5—C4—C5—C6 | −10.0 (3) |
O2—C1—C2—C3 | 98.9 (2) | C4—C5—C6—C7 | 2.6 (4) |
O1—C1—C2—C3 | −80.16 (19) | C5—C6—C7—O6 | −176.5 (2) |
N1—C2—C3—O3 | −54.5 (2) | C5—C6—C7—O7 | 3.8 (3) |
C1—C2—C3—O3 | −173.39 (15) | | |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O6i | 0.93 (3) | 1.91 (3) | 2.837 (2) | 173 (2) |
N1—H1B···O3ii | 0.86 (2) | 2.10 (2) | 2.840 (2) | 143.5 (18) |
N1—H1C···O6iii | 0.90 (2) | 1.98 (2) | 2.866 (2) | 168 (2) |
O1—H1···O4iv | 0.93 (3) | 1.61 (3) | 2.5338 (18) | 175 (3) |
O3—H3···O2v | 0.83 (2) | 2.12 (2) | 2.7224 (18) | 130 (2) |
O7—H7···O5 | 1.00 (4) | 1.45 (4) | 2.428 (2) | 165 (3) |
Symmetry codes: (i) x, y, z+1; (ii) −x+2, y+1/2, −z+2; (iii) −x+1, y+1/2, −z+1; (iv) x−1, y, z; (v) x+1, y, z. |
(II)
DL-Serinium semi-maleate
top
Crystal data top
C3H8NO3+·C4H3O4− | Z = 2 |
Mr = 221.17 | F(000) = 232 |
Triclinic, P1 | Dx = 1.548 Mg m−3 |
a = 5.9406 (3) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 8.9527 (4) Å | Cell parameters from 2552 reflections |
c = 9.3796 (3) Å | θ = 2.3–28.1° |
α = 79.239 (3)° | µ = 0.14 mm−1 |
β = 75.528 (3)° | T = 297 K |
γ = 86.771 (4)° | Block, colourless |
V = 474.50 (3) Å3 | 0.25 × 0.15 × 0.05 mm |
Data collection top
Agilent Xcalibur (Ruby, Gemini Ultra) diffractometer | 1943 independent reflections |
Radiation source: fine-focus sealed tube | 1597 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.022 |
Detector resolution: 10.3457 pixels mm-1 | θmax = 26.4°, θmin = 2.3° |
rotation method scans | h = −7→7 |
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2012) | k = −11→11 |
Tmin = 0.964, Tmax = 1.000 | l = −11→11 |
5841 measured reflections | |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.044 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.115 | All H-atom parameters refined |
S = 1.05 | w = 1/[σ2(Fo2) + (0.0487P)2 + 0.2145P] where P = (Fo2 + 2Fc2)/3 |
1943 reflections | (Δ/σ)max < 0.001 |
180 parameters | Δρmax = 0.33 e Å−3 |
0 restraints | Δρmin = −0.18 e Å−3 |
Crystal data top
C3H8NO3+·C4H3O4− | γ = 86.771 (4)° |
Mr = 221.17 | V = 474.50 (3) Å3 |
Triclinic, P1 | Z = 2 |
a = 5.9406 (3) Å | Mo Kα radiation |
b = 8.9527 (4) Å | µ = 0.14 mm−1 |
c = 9.3796 (3) Å | T = 297 K |
α = 79.239 (3)° | 0.25 × 0.15 × 0.05 mm |
β = 75.528 (3)° | |
Data collection top
Agilent Xcalibur (Ruby, Gemini Ultra) diffractometer | 1943 independent reflections |
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2012) | 1597 reflections with I > 2σ(I) |
Tmin = 0.964, Tmax = 1.000 | Rint = 0.022 |
5841 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.044 | 0 restraints |
wR(F2) = 0.115 | All H-atom parameters refined |
S = 1.05 | Δρmax = 0.33 e Å−3 |
1943 reflections | Δρmin = −0.18 e Å−3 |
180 parameters | |
Special details top
Experimental. Absorption correction CrysAlisPro, Agilent Technologies,
Version 1.171.35.21 (release 20-01-2012 CrysAlis171 .NET)
(compiled Jan 23 2012,18:06:46)
Empirical absorption correction using spherical harmonics,
implemented in SCALE3 ABSPACK scaling algorithm.
(Agilent, 2012) |
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 | |
C1 | 1.0310 (3) | 0.0338 (2) | 0.6819 (2) | 0.0351 (4) | |
O1 | 1.0860 (3) | 0.15685 (17) | 0.58309 (17) | 0.0521 (4) | |
H1 | 1.263 (6) | 0.178 (4) | 0.563 (4) | 0.118 (12)* | |
N1 | 0.7148 (3) | −0.14040 (19) | 0.8233 (2) | 0.0387 (4) | |
H1A | 0.838 (5) | −0.172 (3) | 0.879 (3) | 0.079 (9)* | |
H1B | 0.692 (5) | −0.214 (3) | 0.765 (3) | 0.072 (8)* | |
H1C | 0.563 (5) | −0.132 (3) | 0.898 (3) | 0.077 (8)* | |
C2 | 0.7692 (3) | 0.0112 (2) | 0.7279 (2) | 0.0355 (4) | |
H2 | 0.709 (4) | 0.009 (2) | 0.645 (3) | 0.043 (6)* | |
O2 | 1.1644 (3) | −0.05158 (17) | 0.73511 (18) | 0.0537 (4) | |
C3 | 0.6437 (4) | 0.1347 (2) | 0.8108 (2) | 0.0390 (5) | |
H3A | 0.465 (4) | 0.123 (2) | 0.827 (2) | 0.039 (5)* | |
H3B | 0.691 (3) | 0.240 (2) | 0.745 (2) | 0.040 (5)* | |
O3 | 0.6913 (2) | 0.11808 (17) | 0.95367 (15) | 0.0413 (4) | |
H3 | 0.808 (5) | 0.173 (3) | 0.949 (3) | 0.071 (8)* | |
C4 | 0.4318 (3) | 0.6656 (2) | 0.6080 (2) | 0.0359 (4) | |
O4 | 0.4958 (3) | 0.75516 (18) | 0.48821 (17) | 0.0541 (4) | |
C5 | 0.1983 (4) | 0.5971 (2) | 0.6367 (2) | 0.0409 (5) | |
H5 | 0.120 (4) | 0.642 (3) | 0.567 (3) | 0.052 (6)* | |
O5 | 0.5529 (2) | 0.63128 (16) | 0.70345 (16) | 0.0435 (4) | |
C6 | 0.0915 (3) | 0.4890 (2) | 0.7459 (2) | 0.0400 (5) | |
H6 | −0.055 (4) | 0.462 (2) | 0.744 (2) | 0.044 (6)* | |
O6 | 0.0509 (3) | 0.29166 (18) | 0.95176 (17) | 0.0562 (5) | |
C7 | 0.1680 (3) | 0.3993 (2) | 0.8746 (2) | 0.0364 (4) | |
O7 | 0.3553 (3) | 0.43370 (16) | 0.90729 (17) | 0.0471 (4) | |
H7 | 0.445 (5) | 0.525 (4) | 0.822 (4) | 0.098 (10)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
C1 | 0.0376 (10) | 0.0363 (10) | 0.0289 (9) | −0.0040 (8) | −0.0033 (8) | −0.0047 (8) |
O1 | 0.0412 (8) | 0.0520 (9) | 0.0502 (9) | −0.0079 (7) | −0.0043 (7) | 0.0160 (7) |
N1 | 0.0412 (10) | 0.0373 (9) | 0.0371 (9) | −0.0096 (7) | −0.0078 (8) | −0.0045 (7) |
C2 | 0.0419 (11) | 0.0372 (10) | 0.0265 (9) | −0.0070 (8) | −0.0074 (8) | −0.0026 (8) |
O2 | 0.0423 (8) | 0.0515 (9) | 0.0604 (10) | −0.0016 (7) | −0.0118 (7) | 0.0063 (8) |
C3 | 0.0384 (11) | 0.0409 (11) | 0.0350 (10) | −0.0042 (9) | −0.0060 (8) | −0.0031 (9) |
O3 | 0.0404 (8) | 0.0496 (8) | 0.0338 (7) | −0.0155 (7) | −0.0041 (6) | −0.0093 (6) |
C4 | 0.0346 (10) | 0.0339 (10) | 0.0370 (10) | −0.0050 (8) | −0.0079 (8) | −0.0010 (8) |
O4 | 0.0418 (8) | 0.0655 (10) | 0.0456 (9) | −0.0154 (7) | −0.0088 (7) | 0.0159 (8) |
C5 | 0.0378 (11) | 0.0436 (11) | 0.0419 (11) | −0.0058 (9) | −0.0190 (9) | 0.0049 (9) |
O5 | 0.0400 (8) | 0.0440 (8) | 0.0469 (8) | −0.0144 (6) | −0.0175 (6) | 0.0039 (6) |
C6 | 0.0316 (10) | 0.0404 (11) | 0.0481 (12) | −0.0087 (8) | −0.0145 (9) | 0.0006 (9) |
O6 | 0.0553 (9) | 0.0544 (9) | 0.0546 (10) | −0.0274 (8) | −0.0203 (8) | 0.0181 (8) |
C7 | 0.0367 (10) | 0.0318 (10) | 0.0391 (10) | −0.0070 (8) | −0.0083 (8) | −0.0016 (8) |
O7 | 0.0488 (9) | 0.0439 (8) | 0.0503 (9) | −0.0172 (7) | −0.0244 (7) | 0.0095 (7) |
Geometric parameters (Å, º) top
C1—O2 | 1.204 (2) | O3—H3 | 0.86 (3) |
C1—O1 | 1.299 (2) | C4—O4 | 1.239 (2) |
C1—C2 | 1.521 (3) | C4—O5 | 1.268 (2) |
O1—H1 | 1.04 (4) | C4—C5 | 1.489 (3) |
N1—C2 | 1.483 (2) | C5—C6 | 1.327 (3) |
N1—H1A | 1.00 (3) | C5—H5 | 0.92 (2) |
N1—H1B | 0.97 (3) | O5—H7 | 1.37 (3) |
N1—H1C | 1.00 (3) | C6—C7 | 1.477 (3) |
C2—C3 | 1.524 (3) | C6—H6 | 0.92 (2) |
C2—H2 | 0.94 (2) | O6—C7 | 1.225 (2) |
C3—O3 | 1.417 (2) | C7—O7 | 1.293 (2) |
C3—H3A | 1.04 (2) | O7—H7 | 1.09 (3) |
C3—H3B | 1.04 (2) | | |
| | | |
O2—C1—O1 | 126.01 (18) | O3—C3—H3B | 113.1 (11) |
O2—C1—C2 | 122.86 (17) | C2—C3—H3B | 108.7 (11) |
O1—C1—C2 | 111.12 (16) | H3A—C3—H3B | 108.0 (16) |
C1—O1—H1 | 110 (2) | C3—O3—H3 | 109.9 (19) |
C2—N1—H1A | 109.8 (16) | O4—C4—O5 | 123.68 (17) |
C2—N1—H1B | 110.9 (16) | O4—C4—C5 | 116.18 (17) |
H1A—N1—H1B | 113 (2) | O5—C4—C5 | 120.14 (17) |
C2—N1—H1C | 107.9 (16) | C6—C5—C4 | 130.47 (19) |
H1A—N1—H1C | 108 (2) | C6—C5—H5 | 118.0 (14) |
H1B—N1—H1C | 106 (2) | C4—C5—H5 | 111.5 (14) |
N1—C2—C1 | 109.71 (16) | C4—O5—H7 | 111.4 (13) |
N1—C2—C3 | 109.90 (15) | C5—C6—C7 | 130.84 (18) |
C1—C2—C3 | 111.75 (16) | C5—C6—H6 | 117.4 (14) |
N1—C2—H2 | 104.8 (13) | C7—C6—H6 | 111.8 (14) |
C1—C2—H2 | 111.5 (13) | O6—C7—O7 | 119.80 (18) |
C3—C2—H2 | 109.0 (13) | O6—C7—C6 | 119.29 (17) |
O3—C3—C2 | 110.35 (16) | O7—C7—C6 | 120.91 (16) |
O3—C3—H3A | 107.6 (11) | C7—O7—H7 | 109.9 (16) |
C2—C3—H3A | 109.0 (11) | | |
| | | |
O2—C1—C2—N1 | −9.8 (3) | O4—C4—C5—C6 | 173.2 (2) |
O1—C1—C2—N1 | 171.84 (16) | O5—C4—C5—C6 | −6.9 (4) |
O2—C1—C2—C3 | 112.4 (2) | C4—C5—C6—C7 | −0.6 (4) |
O1—C1—C2—C3 | −66.0 (2) | C5—C6—C7—O6 | −171.1 (2) |
N1—C2—C3—O3 | 52.4 (2) | C5—C6—C7—O7 | 9.5 (4) |
C1—C2—C3—O3 | −69.6 (2) | | |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O6i | 1.00 (3) | 1.98 (3) | 2.900 (2) | 152 (2) |
N1—H1B···O5ii | 0.97 (3) | 1.90 (3) | 2.826 (2) | 160 (2) |
N1—H1C···O3i | 1.00 (3) | 1.80 (3) | 2.796 (2) | 174 (2) |
O1—H1···O4iii | 1.04 (4) | 1.51 (4) | 2.537 (2) | 166 (3) |
O3—H3···O6iv | 0.86 (3) | 1.85 (3) | 2.706 (2) | 176 (3) |
O7—H7···O5 | 1.09 (3) | 1.37 (3) | 2.4517 (19) | 174 (3) |
Symmetry codes: (i) −x+1, −y, −z+2; (ii) x, y−1, z; (iii) −x+2, −y+1, −z+1; (iv) x+1, y, z. |
Experimental details
| (I) | (II) |
Crystal data |
Chemical formula | C3H8NO3+·C4H3O4− | C3H8NO3+·C4H3O4− |
Mr | 221.17 | 221.17 |
Crystal system, space group | Monoclinic, P21 | Triclinic, P1 |
Temperature (K) | 297 | 297 |
a, b, c (Å) | 6.9527 (11), 6.5631 (10), 10.4284 (19) | 5.9406 (3), 8.9527 (4), 9.3796 (3) |
α, β, γ (°) | 90, 97.094 (14), 90 | 79.239 (3), 75.528 (3), 86.771 (4) |
V (Å3) | 472.22 (13) | 474.50 (3) |
Z | 2 | 2 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.14 | 0.14 |
Crystal size (mm) | 0.3 × 0.25 × 0.1 | 0.25 × 0.15 × 0.05 |
|
Data collection |
Diffractometer | Stoe IPDS II diffractometer | Agilent Xcalibur (Ruby, Gemini Ultra) diffractometer |
Absorption correction | – | Multi-scan (CrysAlis PRO; Agilent, 2012) |
Tmin, Tmax | – | 0.964, 1.000 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3648, 2508, 1905 | 5841, 1943, 1597 |
Rint | 0.021 | 0.022 |
(sin θ/λ)max (Å−1) | 0.685 | 0.625 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.039, 0.070, 0.93 | 0.044, 0.115, 1.05 |
No. of reflections | 2508 | 1943 |
No. of parameters | 180 | 180 |
No. of restraints | 1 | 0 |
H-atom treatment | All H-atom parameters refined | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.17, −0.16 | 0.33, −0.18 |
Hydrogen-bond geometry (Å, º) for (I) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O6i | 0.93 (3) | 1.91 (3) | 2.837 (2) | 173 (2) |
N1—H1B···O3ii | 0.86 (2) | 2.10 (2) | 2.840 (2) | 143.5 (18) |
N1—H1C···O6iii | 0.90 (2) | 1.98 (2) | 2.866 (2) | 168 (2) |
O1—H1···O4iv | 0.93 (3) | 1.61 (3) | 2.5338 (18) | 175 (3) |
O3—H3···O2v | 0.83 (2) | 2.12 (2) | 2.7224 (18) | 130 (2) |
O7—H7···O5 | 1.00 (4) | 1.45 (4) | 2.428 (2) | 165 (3) |
Symmetry codes: (i) x, y, z+1; (ii) −x+2, y+1/2, −z+2; (iii) −x+1, y+1/2, −z+1; (iv) x−1, y, z; (v) x+1, y, z. |
Hydrogen-bond geometry (Å, º) for (II) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O6i | 1.00 (3) | 1.98 (3) | 2.900 (2) | 152 (2) |
N1—H1B···O5ii | 0.97 (3) | 1.90 (3) | 2.826 (2) | 160 (2) |
N1—H1C···O3i | 1.00 (3) | 1.80 (3) | 2.796 (2) | 174 (2) |
O1—H1···O4iii | 1.04 (4) | 1.51 (4) | 2.537 (2) | 166 (3) |
O3—H3···O6iv | 0.86 (3) | 1.85 (3) | 2.706 (2) | 176 (3) |
O7—H7···O5 | 1.09 (3) | 1.37 (3) | 2.4517 (19) | 174 (3) |
Symmetry codes: (i) −x+1, −y, −z+2; (ii) x, y−1, z; (iii) −x+2, −y+1, −z+1; (iv) x+1, y, z. |
Torsion angles (°) in the L-serinium cation of (I) and (II) topTorsion angle | L-Serinium maleate | DL-Serinium maleate |
C1—C2—C3—O3 | -173.31 (15) | -69.7 (2) |
O1—C1—C2—C3 | -80.19 (19) | -66.1 (2) |
O1—C1—C2—N1 | 160.14 (14) | 171.77 (16) |
O2—C1—C2—C3 | 98.9 (2) | 112.4 (2) |
O2—C1—C2—N1 | -20.7 (2) | -9.8 (3) |
N1—C2—C3—O3 | -54.4 (2) | 52.4 (2) |
Torsion angles (°) in the semi-maleate anion of (I) and (II) topTorsion angle | L-Serinium maleate | DL-Serinium maleate |
C4—C5—C6—C7 | 2.5 (4) | -0.6 (4) |
O4—C4—C5—C6 | 170.0 (2) | 173.2 (2) |
O5—C4—C5—C6 | -9.9 (3) | -6.9 (4) |
O6—C7—C6—C5 | -176.4 (2) | -171.0 (2) |
O7—C7—C6—C5 | 3.8 (3) | 9.5 (4) |
Structural-motif analysis top | (I) | (II) | L-Ser | L-Ser (p) | DL-Ser |
C22(12)OH C22(9) | | + | | + | + |
C22(12)NH3 | 2+ | + | | | |
C12(4) | + | | + | + | + |
R22(10)R22(9) | | + | | | + |
C(6) | + | | | + | + |
Serine is involved in the formation of the active centres of several important enzymes, such as the serine proteases. Molecular conformations, hydrogen bonding and mobility of the side chain in different environments are of primary importance for biological function. Multicomponent serine crystals can be considered as biomimetics when analysing the relationship between crystal structures, hydrogen bonding and side-chain mobility. In addition, some of them are promising as molecular materials, with piezoelectric, ferroelectric or nonlinear optical properties, or as biologically active compounds. The systems are also of fundamental interest for crystal engineering. Their structures can help in understanding the role of the presence of several potential hydrogen-bond donors and acceptors, and that of the shape and flexibility of molecules, in forming a particular molecular packing in multi-component crystals. This knowledge is valuable for its own sake, but also finds important applications in the design of desirable structures of salts or cocrystals of pharmaceutical importance (Desiraju, 1995, 2010; Nangia & Desiraju, 1998; Aakeröy & Salmon, 2005). Multicomponent crystals also provide the possibility of obtaining the same molecule in different conformations, which may be interesting for the analysis of the relationship between molecular structure and properties.
Six multicomponent crystals of serine with organic counterparts containing carboxylic acid groups are known, namely L-serinium (+)-18-crown-6-tetracarboxylic acid perchlorate monohydrate and D-serinium (+)-tricarboxy-18-crown-6-carboxylate hexahydrate (Nagata et al., 2006), bis(DL-serinium) oxalate dihydrate (Alagar et al., 2002a), bis(L-serinium) oxalate dihydrate (forms I and II) (Braga et al., 2013), and a cocrystal of L-serine with pyridine-2,4-dicarboxylic acid (Liang, 2008). No anhydrous serinium salts or cocrystals of L and DL counterparts with the same chemical composition have been reported thus far. A comparison of such pairs would be of great interest, since the crystals of pure L- and DL-serine differ radically in their properties, and provide an example of the violation of Wallah's rule (Kolesov & Boldyreva, 2007; Bordallo et al., 2007; Boldyreva et al., 2006; Drebushchak et al., 2007; Chesalov & Boldyreva, 2008). L-Serinium semi-maleate, (I), and DL-serinium semi-maleate, (II), provide the first example of chiral and racemic counterparts of an anhydrous serinium salt with the same chemical composition and stoichiometry.
The asymmetric units of (I) and (II) contain a serinium cation and a semi-maleate anion (Fig. 1). The crystal structure of (I) is monoclinic (space group P21) and that of (II) is triclinic (space group P1). The L-serinium cation and semi-maleate anion in (I) and (II) have different conformations (Tables 1 and 2).
The crystal structures of (I) and (II) display several types of intermolecular N—H···O and O—H···O hydrogen bonds, as well as a short O—H···O intramolecular hydrogen bond in the semi-maleate anion (Tables 3 and 4).
Neither (I) nor (II) has head-to-tail chains formed by the serinium cations. In (I), the cations are linked into infinite chains via hydrogen bonds between carboxy and hydroxy groups (not between amino and carboxy groups), which is exceptional for crystal structures of amino acid salts. In (II), there are no chains linking the cations.
In (I), C22(12) chains [see Bernstein et al. (1995) for hydrogen-bonding motifs] form in the [101] plane and are linked to each other via C(6) chains, which are built exclusively of L-serinium cations (green in the electronic version of Fig. 2a). The C(6) chains run along the a axis. The C22(12)' chains run along the b axis, normal to the C22(12) chains. L-Serinium cations from the C22(12)' chains also form C11(5) chains in another direction (marked green in the electronic version of Fig. 2b). The cations and anions in the C22(12)' chains form spring-like stacks, which can be supposed to account for the interesting response of this structure to variations in pressure and temperature (Fig. 2b).
In (II), the C22(12) chains are very similar to those in (I), but, in contrast with (I), they lie in the same plane and are not linked to each other by hydrogen bonds (Fig. 3a). The C22(12) chains in different planes are antiparallel (Fig. 3b). Layers in which all the chains are formed by semi-maleate anions and L-serinium cations alternate regularly with similar layers in which all the chains are formed by semi-maleate anions and D-serinium cations. Two antiparallel chains neighbouring layers linked by N1—H1B···O5(x, -1 + y, z) hydrogen bonds give rise to R44(18) rings. N1—H1C···O3(1 - x, -y, 2 - z) hydrogen bonds give rise to R22(10) rings consisting exclusively of serinium cations and R44(26) rings including L- and D-serinium cations and two semi-maleate anions. Rings of motif R22(10) and R44(18) have a common N atom, and together form columns parallel to the b axis.
The molecular packing in the structures of L-serine and of (I) differ in several respects. As is common for crystalline amino acids, in L-serine the molecules form head-to-tail C(2) chains, with N—H···O hydrogen bonds between the amino and carboxy groups within one chain. These chains are further linked via additional O—H···O hydrogen bonds between the hydroxy groups of neighbouring chains, as is typical for the crystal structures of alcohols. Such chains are no longer present in (I). The hydroxy group of the side chain in the structure of (I) is involved in the formation of C(5) and C(6) chains. In the former, the –OH group acts as a hydrogen-bond acceptor, with the H3+ group acting as a donor. In the latter, the –OH group donates an H atom and a –COOH group accepts. Similar chains are present in the crystal structure of pure DL-serine (Table 5). Interestingly, a similar C(6) is observed in the high-pressure polymorphs of L-serineII (Boldyreva et al., 2006; Drebushchak et al., 2006). Since the crystal structure of DL-serine is stable under increasing pressure, at least up to 8.6 GPa (Boldyreva et al., 2006), one can suppose the structure of (I) to be also stable with increasing pressure. The C21(4) chains, in which the two NH3+ groups and a –COO- group are involved, are present in (I), L-serine, L-serineII and DL-serine. The difference is that in L-serine, L-serineII and DL-serine the –COOH group belongs to serine, whereas in (I) it belongs to the semi-maleate anion.
A comparison of the crystal structures of (II) and DL-serine (Shoemaker et al., 1953) reveals serine dimers, giving R22(10) rings for (II) and R22(9) rings for pure DL-serine. Chains similar to the C22(12) chains in (II) can also be observed in the structure of DL-serine and in the high-pressure polymorphs of L-serineII, with the difference that the serine carboxylate groups act as H-atom acceptors in the last two cases.
Thus, in the structure of L-serinium semi-maleate, (I), one can find structural motifs of pure L-serine, pure DL-serine, high-pressure polymorphs of L-serineII and DL-serinium semi-maleate, (II).
Maleic acid is a common salt and cocrystal co-former. In particular, eight L salts with amino acids [L-alaninium maleate (Alagar, Krishnakumar, Nandhini et al., 2001), L-phenylalaninium maleate (Alagar, Krishnakumar & Natarajan, 2001), L-argininium maleate dihydrate (Sun et al., 2007), L-histidine maleic acid and L-lysine maleic acid (Pratap et al., 2000), L-histidinium maleate sesquihydrate (Gonsago et al., 2012), L-histidinium maleate hydrate and bis[L-histidinium(2+)] dimaleate (Fleck et al., 2013)], four DL salts [DL-threoninium hydrogen maleate (Rajagopal et al., 2004), DL-methioninium maleate (Alagar et al., 2002b), DL-valinium hydrogen maleate (Alagar, Krishnakumar, Mostad et al., 2001) and DL-phenylalaninium hydrogen maleate (Alagar et al., 2003)], and one salt with nonchiral glycine (Rajagopal et al., 2001) have been described to date. Nine of these 15 structures [including (I) and (II)] have C22(12) chains formed by the –COOH group of the amino acid, the –COO- [OK?] groups of the maleate anions and the NH3+ group of the amino acids. The structures of L-argininium maleate dihydrate, L-histidine maleic acid, L-histidinium maleate hydrate, L-histidinium maleate sesquihydrate and L-lysine maleic acid do not have these C22(12) chains, because the carboxy groups of the amino acids in these structures are deprotonated (COO-). The structure of DL-threoninium hydrogen maleate has C22(12) chains, although it is the –OH and not the NH3+ groups which act as donors.
In most of these structures, the amino acid molecules form head-to-tail chains linked via hydrogen bonds between the amino and carboxy groups, similar to what is observed in pure crystalline amino acids. L-Alaninium maleate, L-phenylalaninium maleate, L-argininium maleate dihydrate, L-histidine maleic acid, DL-methioninium maleate, DL-phenylalaninium hydrogen maleate and glycinium maleate have head-to-tail motifs. The L-lysine maleic acid structure has motifs similar to head-to-tail chains, but in this case the NH3+ groups of the lysine radicals play the role of the `heads'. As already mentioned, the structures of (I) and (II) have no head-to-tail motif. In three out of the five [including (II)] known structures of DL-amino acid maleates, there are dimers formed by D- and L-counterparts linked by N—H···O hydrogen bonds, which are surrounded by eight or six semi-maleate anions (Fig. 4). In the two remaining structures, the amino acid dimers are `broken' by semi-maleate anions.
The immediate environment of the ring formed by the L- and D-serinium cations in (II) is very similar to that in DL-threoninium hydrogen maleate (Rajagopal et al., 2004). Unfortunately, the structure of L-threonine maleate remains unknown (or unreported). It would be very interesting to compare it with that of (I) to see if they are also similar.
The structure of (II) is the first example in the series of structures of maleic acid with racemic amino acids that has a three-dimensional hydrogen-bond network. Other structures of the same series exhibit a two-dimensional sheet-like hydrogen-bonding scheme and packing array. In contrast, for the structures of maleic acid with L-amino acids, three-dimensional hydrogen-bond networks are typical. L-Phenylalaninium maleate is the only exception, its large hydrophobic side chain accounting for the two-dimensional hydrogen-bonded layered structure that is observed. The structure of glycinium maleate also has a two-dimensional hydrogen-bonding network, possibly because pure glycine tends to form layers.