L-Me­thio­nine–succinic acid (2/1)

The asymmetric unit of the title compound, 2C₅H₁₁NO₂S·C₄H₆O₄, comprises two crystallographically independent me­thio­nine residues, which exist in the zwitterionic form, and a neutral succinic acid mol­ecule. Both me­thio­nine residues have a gauche-I conformation. In the crystal, the various components are linked via O—H...O, N—H...O and C—H...O hydrogen bonds forming slabs parallel to the ab plane

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.012 Å
• R factor = 0.063
• wR factor = 0.171
• Data-to-parameter ratio = 14.0

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Alert level A
PLAT073_ALERT_1_A H-atoms ref, but _hydrogen_treatment reported as     constr Check

Alert level B
PLAT340_ALERT_3_B Low Bond Precision on  C-C Bonds ...............    0.01156 Ang.

Alert level C
PLAT220_ALERT_2_C Large Non-Solvent  C     Ueq(max)/Ueq(min) Range        3.4 Ratio

Author Response: 3.2 Ratio

PLAT222_ALERT_3_C Large Non-Solvent  H     Uiso(max)/Uiso(min) ...        4.2 Ratio

Author Response: 3.6 Ratio

PLAT234_ALERT_4_C Large Hirshfeld Difference S2     --  C14     ..       0.18 Ang.

Author Response: 0.16 Ang.

PLAT480_ALERT_4_C Long H...A H-Bond Reported H12B   ..  O8      ..       2.65 Ang.

Author Response: 2.65 Ang

PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600         27 Report

Author Response: 27 Report

PLAT915_ALERT_3_C Low Friedel Pair Coverage ....(No Flack x Check)         79 %

Author Response: 72-79 %

PLAT934_ALERT_3_C Number of (Iobs-Icalc)/SigmaW > 10 Outliers ....          1 Check

Alert level G
PLAT002_ALERT_2_G Number of Distance or Angle Restraints on AtSite          4 Note
PLAT007_ALERT_5_G Number of Unrefined Donor-H Atoms ..............          5 Report
PLAT172_ALERT_4_G The CIF-Embedded .res File Contains DFIX Records          2 Report
PLAT199_ALERT_1_G Reported _cell_measurement_temperature ..... (K)        293 Check
PLAT200_ALERT_1_G Reported   _diffrn_ambient_temperature ..... (K)        293 Check
PLAT790_ALERT_4_G Centre of Gravity not Within Unit Cell: Resd.  #          3 Note
              C4 H6 O4
PLAT791_ALERT_4_G The Model has Chirality at C6      (Chiral SPGR)          S Verify
PLAT791_ALERT_4_G The Model has Chirality at C11     (Chiral SPGR)          S Verify
PLAT860_ALERT_3_G Number of Least-Squares Restraints .............          9 Note
PLAT910_ALERT_3_G Missing # of FCF Reflection(s) Below Th(Min) ...          2 Report
PLAT912_ALERT_4_G Missing # of FCF Reflections Above STh/L=  0.600          7 Note

   1 ALERT level A = Most likely a serious problem - resolve or explain
   1 ALERT level B = A potentially serious problem, consider carefully
   7 ALERT level C = Check. Ensure it is not caused by an omission or oversight
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   3 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
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S1. Experimental

Colourless transparent single crystals of the title compound were obtained by slow evaporation of an aqueous solution of L-methionine and succinic acid, in a stoichiometric ratio of 2:1, over a period of 20 days.

S2. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2.

Structure description

Methionine is a sulfur-containing amino acid which is essential for normal metabolism, growth and maintenance of body tissues (Sridhar et al., 2002). In conjunction with our ongoing work on nonlinear optical crystals, among the 20 naturally occurring amino acids we have focused our interest towards methionine, which is one of the essential amino acids for humans. In this paper, the crystal structure of the product of the reaction of L-methionine with succinic acid is reported.

The molecular structure of the title compound is represented in Fig. 1. The asymmetric unit contains two methionine residues and a neutral succinic acid molecule. Both methionine residues exhibit a gauche I conformation. The bond distances C5—O6, C5—O5, C10—O7 and C10—O8 are 1.244 (9), 1.248 (9), 1.232 (9) and 1.260 (9) Å, respectively, indicating a deprotonated carboxylate groups in the methionine residue. This unsymmetrical unit has bond angles O5—C5—O6 and O8—C10—O7 of 125.6 (7) and 124.7 (7) °, respectively. The backbone torsion angles Ψ1 for the central methionine of O5—C5—C6—N1 and O6—C5—C6—N1 are 4.8 (9) and −176.1 (6)°, respectively. For the end methionine residue, the backbone torsion angles Ψ1 of O7—C10—C11—N2 and O8—C10—C11—N2 are 5.8 (9) and −174.4 (6) °, respectively. The side-chain conformation for both methionine residues is gauche I trans gauche I. All possible rotational isomers are found to exist in the methionine residues (Pandiarajan et al., 2002). In both the methionine residues, the straight side chain conformation angles χ1 are in the gauche I form [70.9 (9) and 67.3 (9) °], while χ2 are in the trans form [179.5 (6) and 177.6 (6) °] and χ3 are in gauche I form [71.9 (9) and 72.1 (9)°].

In the crystal, the various components are linked via O—H···O, N—H···O and C—H···O hydrogen bonds, forming slabs parallel to the ab plane (Table 1 and Fig. 2). There are no direct hydrogen-bonding interactions between the succinic acid molecules. The methionine residues are interlinked through the succinic acid molecules. The crystal packing may be visualized as hydrogen-bonded triple layers, a characteristic feature of α amino acids having hydrocarbon side chains, stacked in such a way that the hydrophobic side chains of the methionine molecules are facing close to each other with respect to succinic acid (Fig. 2).

Computing details

Data collection: APEX2 (Bruker, 2004); cell refinement: APEX2 and SAINT (Bruker, 2004); data reduction: SAINT and XPREP (Bruker, 2004); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015).

Figures

	Fig. 1. The molecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 40% probability level.
	Fig. 2. The crystal packing of the title compound, viewed along the a axis. The hydrogen bonds are shown as dashed lines (see Table 1 for details).

L-Methionine–succinic acid (2/1)

Crystal data

2C5H11NO2S·C4H6O4	Z = 1
Mr = 416.50	F(000) = 222
Triclinic, P1	Dx = 1.408 Mg m^−3
a = 5.0283 (4) Å	Mo Kα radiation, λ = 0.71073 Å
b = 5.0580 (4) Å	Cell parameters from 5997 reflections
c = 20.8394 (18) Å	θ = 3.0–28.3°
α = 86.645 (2)°	µ = 0.31 mm^−1
β = 83.338 (3)°	T = 293 K
γ = 68.908 (5)°	Block, colourless
V = 491.08 (7) Å^3	0.35 × 0.30 × 0.25 mm

Data collection

Bruker Kappa APEXII CCD diffractometer	3428 independent reflections
Radiation source: fine-focus sealed tube	3251 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.035
ω and φ scan	θmax = 26.0°, θmin = 3.0°
Absorption correction: multi-scan (SADABS; Bruker, 2004)	h = −6→6
Tmin = 0.873, Tmax = 0.956	k = −6→5
8433 measured reflections	l = −25→25

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: mixed
R[F^2 > 2σ(F^2)] = 0.063	H-atom parameters constrained
wR(F^2) = 0.171	w = 1/[σ^2(Fo^2) + (0.048P)^2 + 1.4388P] where P = (Fo^2 + 2Fc^2)/3
S = 1.11	(Δ/σ)max = 0.001
3428 reflections	Δρmax = 0.56 e Å^−3
244 parameters	Δρmin = −0.38 e Å^−3
9 restraints	Absolute structure: Flack x determined using 1325 quotients [(I^+)-(I^-)]/[(I^+)+(I^-)] (Parsons et al., 2013)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.06 (4)

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	−0.0929 (15)	−0.3017 (17)	1.2684 (3)	0.0267 (16)
C2	0.0926 (16)	−0.1994 (15)	1.2208 (4)	0.0278 (16)
H2A	0.1576	−0.0710	1.2419	0.033*
H2B	−0.0187	−0.0941	1.1866	0.033*
C3	0.3501 (15)	−0.4389 (17)	1.1917 (4)	0.0294 (17)
H3A	0.4878	−0.3610	1.1701	0.035*
H3B	0.4404	−0.5647	1.2262	0.035*
C4	0.2765 (16)	−0.6065 (15)	1.1445 (3)	0.0256 (15)
C5	0.2712 (15)	−0.2155 (15)	0.9996 (3)	0.0238 (15)
C6	−0.0208 (14)	−0.0051 (14)	0.9834 (4)	0.0239 (15)
H6	−0.1672	−0.0747	1.0051	0.029*
C7	−0.0529 (17)	0.0129 (17)	0.9119 (4)	0.0340 (18)
H7A	−0.0575	−0.1664	0.8990	0.041*
H7B	−0.2363	0.1576	0.9048	0.041*
C8	0.177 (2)	0.079 (2)	0.8687 (4)	0.050 (2)
H8A	0.3612	−0.0645	0.8758	0.060*
H8B	0.1809	0.2597	0.8811	0.060*
C9	−0.165 (3)	0.420 (3)	0.7771 (6)	0.082 (4)
H9A	−0.2084	0.4513	0.7330	0.122*
H9B	−0.3287	0.4079	0.8041	0.122*
H9C	−0.1182	0.5748	0.7906	0.122*
C10	0.2140 (15)	0.6224 (16)	0.4123 (4)	0.0259 (16)
C11	0.4113 (15)	0.3242 (15)	0.4278 (4)	0.0254 (15)
H11	0.3531	0.1939	0.4047	0.030*
C12	0.3860 (17)	0.2466 (18)	0.4989 (4)	0.0353 (18)
H12A	0.1932	0.2486	0.5112	0.042*
H12B	0.5166	0.0540	0.5049	0.042*
C13	0.447 (2)	0.433 (2)	0.5437 (4)	0.045 (2)
H13A	0.3217	0.6271	0.5365	0.054*
H13B	0.6424	0.4248	0.5327	0.054*
C14	0.709 (3)	0.027 (3)	0.6336 (7)	0.072 (4)
H14A	0.7119	−0.0447	0.6773	0.108*
H14B	0.6967	−0.1123	0.6057	0.108*
H14C	0.8805	0.0655	0.6206	0.108*
N1	−0.0777 (13)	0.2796 (12)	1.0094 (3)	0.0280 (14)
N2	0.7110 (12)	0.2804 (13)	0.4033 (3)	0.0263 (13)
H2C	0.7204	0.3274	0.3615	0.039*
H2D	0.7744	0.3884	0.4250	0.039*
H2E	0.8190	0.0991	0.4086	0.039*
O1	0.4981 (11)	−0.8243 (12)	1.1218 (3)	0.0378 (14)
H1	0.4469	−0.9096	1.0963	0.057*
O2	0.0410 (11)	−0.5487 (13)	1.1270 (3)	0.0389 (14)
O3	−0.0496 (12)	−0.5422 (12)	1.2855 (3)	0.0370 (13)
O4	−0.3294 (11)	−0.0864 (11)	1.2910 (3)	0.0364 (13)
H4	−0.4281	−0.1485	1.3172	0.055*
O5	0.4115 (11)	−0.1349 (11)	1.0347 (3)	0.0343 (13)
O6	0.3459 (11)	−0.4561 (11)	0.9767 (3)	0.0338 (12)
O7	0.3106 (11)	0.7815 (11)	0.3784 (3)	0.0332 (13)
O8	−0.0432 (11)	0.6879 (11)	0.4360 (3)	0.0338 (12)
S1	0.1337 (7)	0.0957 (6)	0.78374 (14)	0.0737 (10)
S2	0.4020 (6)	0.3478 (6)	0.62834 (14)	0.0685 (9)
H1C	−0.08 (2)	0.28 (2)	1.0528 (13)	0.082*
H1A	−0.245 (11)	0.40 (2)	0.997 (4)	0.082*
H1B	0.065 (15)	0.34 (2)	0.992 (4)	0.082*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.019 (4)	0.031 (5)	0.030 (4)	−0.009 (3)	−0.005 (3)	−0.004 (3)
C2	0.027 (4)	0.019 (4)	0.037 (4)	−0.008 (3)	−0.003 (3)	−0.001 (3)
C3	0.020 (4)	0.040 (5)	0.034 (4)	−0.017 (4)	−0.001 (3)	−0.001 (3)
C4	0.023 (4)	0.022 (4)	0.032 (4)	−0.008 (3)	0.000 (3)	−0.001 (3)
C5	0.021 (4)	0.017 (4)	0.033 (4)	−0.006 (3)	−0.003 (3)	0.003 (3)
C6	0.015 (3)	0.016 (4)	0.041 (4)	−0.007 (3)	0.000 (3)	−0.003 (3)
C7	0.028 (4)	0.023 (4)	0.052 (5)	−0.008 (3)	−0.015 (3)	−0.004 (3)
C8	0.051 (6)	0.051 (6)	0.041 (5)	−0.009 (5)	−0.006 (4)	−0.001 (4)
C9	0.109 (12)	0.081 (10)	0.056 (8)	−0.032 (9)	−0.031 (7)	0.019 (6)
C10	0.015 (3)	0.033 (4)	0.032 (4)	−0.009 (3)	−0.004 (3)	−0.007 (3)
C11	0.015 (3)	0.018 (4)	0.045 (4)	−0.007 (3)	−0.002 (3)	−0.005 (3)
C12	0.022 (4)	0.025 (4)	0.054 (5)	−0.005 (3)	−0.001 (3)	0.005 (3)
C13	0.055 (6)	0.038 (5)	0.040 (5)	−0.014 (5)	−0.003 (4)	0.000 (4)
C14	0.065 (8)	0.049 (7)	0.090 (9)	−0.001 (6)	−0.031 (7)	0.022 (6)
N1	0.025 (3)	0.010 (3)	0.045 (4)	0.000 (3)	−0.007 (3)	−0.005 (2)
N2	0.017 (3)	0.017 (3)	0.041 (3)	−0.001 (3)	−0.002 (2)	0.001 (3)
O1	0.023 (3)	0.031 (3)	0.058 (4)	−0.006 (3)	−0.004 (2)	−0.015 (3)
O2	0.020 (3)	0.045 (4)	0.050 (3)	−0.007 (3)	−0.005 (2)	−0.015 (3)
O3	0.034 (3)	0.022 (3)	0.050 (3)	−0.009 (3)	0.008 (3)	−0.001 (2)
O4	0.026 (3)	0.022 (3)	0.055 (4)	−0.005 (3)	0.007 (2)	−0.002 (2)
O5	0.024 (3)	0.020 (3)	0.059 (3)	−0.005 (2)	−0.014 (2)	−0.005 (2)
O6	0.024 (3)	0.017 (3)	0.055 (3)	0.001 (2)	−0.008 (2)	−0.006 (2)
O7	0.022 (3)	0.016 (3)	0.058 (3)	−0.004 (2)	0.000 (2)	0.005 (2)
O8	0.016 (3)	0.028 (3)	0.053 (3)	−0.003 (2)	−0.001 (2)	0.003 (2)
S1	0.098 (2)	0.075 (2)	0.0378 (14)	−0.0181 (19)	−0.0056 (14)	−0.0013 (12)
S2	0.075 (2)	0.080 (2)	0.0399 (14)	−0.0173 (17)	−0.0014 (12)	0.0058 (13)

Geometric parameters (Å, º)

C1—O3	1.196 (9)	C9—H9C	0.9600
C1—O4	1.349 (9)	C10—O7	1.232 (9)
C1—C2	1.480 (10)	C10—O8	1.260 (9)
C2—C3	1.512 (10)	C10—C11	1.518 (10)
C2—H2A	0.9700	C11—N2	1.475 (9)
C2—H2B	0.9700	C11—C12	1.513 (11)
C3—C4	1.494 (10)	C11—H11	0.9800
C3—H3A	0.9700	C12—C13	1.496 (13)
C3—H3B	0.9700	C12—H12A	0.9700
C4—O2	1.208 (9)	C12—H12B	0.9700
C4—O1	1.317 (9)	C13—S2	1.798 (9)
C5—O6	1.244 (9)	C13—H13A	0.9700
C5—O5	1.248 (9)	C13—H13B	0.9700
C5—C6	1.533 (10)	C14—S2	1.801 (12)
C6—N1	1.486 (9)	C14—H14A	0.9600
C6—C7	1.511 (11)	C14—H14B	0.9600
C6—H6	0.9800	C14—H14C	0.9600
C7—C8	1.505 (13)	N1—H1C	0.90 (3)
C7—H7A	0.9700	N1—H1A	0.90 (3)
C7—H7B	0.9700	N1—H1B	0.90 (3)
C8—S1	1.802 (9)	N2—H2C	0.8900
C8—H8A	0.9700	N2—H2D	0.8900
C8—H8B	0.9700	N2—H2E	0.8900
C9—S1	1.793 (15)	O1—H1	0.8200
C9—H9A	0.9600	O4—H4	0.8200
C9—H9B	0.9600
O3—C1—O4	122.1 (7)	H9B—C9—H9C	109.5
O3—C1—C2	126.5 (7)	O7—C10—O8	124.7 (7)
O4—C1—C2	111.4 (7)	O7—C10—C11	119.5 (6)
C1—C2—C3	112.4 (6)	O8—C10—C11	115.8 (6)
C1—C2—H2A	109.1	N2—C11—C12	111.2 (6)
C3—C2—H2A	109.1	N2—C11—C10	111.1 (6)
C1—C2—H2B	109.1	C12—C11—C10	113.1 (6)
C3—C2—H2B	109.1	N2—C11—H11	107.1
H2A—C2—H2B	107.9	C12—C11—H11	107.1
C4—C3—C2	113.2 (6)	C10—C11—H11	107.1
C4—C3—H3A	108.9	C13—C12—C11	115.9 (7)
C2—C3—H3A	108.9	C13—C12—H12A	108.3
C4—C3—H3B	108.9	C11—C12—H12A	108.3
C2—C3—H3B	108.9	C13—C12—H12B	108.3
H3A—C3—H3B	107.8	C11—C12—H12B	108.3
O2—C4—O1	122.2 (7)	H12A—C12—H12B	107.4
O2—C4—C3	124.6 (7)	C12—C13—S2	115.5 (6)
O1—C4—C3	113.2 (6)	C12—C13—H13A	108.4
O6—C5—O5	125.6 (7)	S2—C13—H13A	108.4
O6—C5—C6	116.1 (6)	C12—C13—H13B	108.4
O5—C5—C6	118.3 (6)	S2—C13—H13B	108.4
N1—C6—C7	111.0 (6)	H13A—C13—H13B	107.5
N1—C6—C5	111.2 (6)	S2—C14—H14A	109.5
C7—C6—C5	112.6 (6)	S2—C14—H14B	109.5
N1—C6—H6	107.2	H14A—C14—H14B	109.5
C7—C6—H6	107.2	S2—C14—H14C	109.5
C5—C6—H6	107.2	H14A—C14—H14C	109.5
C8—C7—C6	115.7 (6)	H14B—C14—H14C	109.5
C8—C7—H7A	108.4	C6—N1—H1C	112 (7)
C6—C7—H7A	108.4	C6—N1—H1A	109 (8)
C8—C7—H7B	108.4	H1C—N1—H1A	109 (4)
C6—C7—H7B	108.4	C6—N1—H1B	107 (7)
H7A—C7—H7B	107.4	H1C—N1—H1B	110 (4)
C7—C8—S1	114.5 (7)	H1A—N1—H1B	110 (4)
C7—C8—H8A	108.6	C11—N2—H2C	109.5
S1—C8—H8A	108.6	C11—N2—H2D	109.5
C7—C8—H8B	108.6	H2C—N2—H2D	109.5
S1—C8—H8B	108.6	C11—N2—H2E	109.5
H8A—C8—H8B	107.6	H2C—N2—H2E	109.5
S1—C9—H9A	109.5	H2D—N2—H2E	109.5
S1—C9—H9B	109.5	C4—O1—H1	109.5
H9A—C9—H9B	109.5	C1—O4—H4	109.5
S1—C9—H9C	109.5	C9—S1—C8	102.1 (5)
H9A—C9—H9C	109.5	C13—S2—C14	100.4 (6)
O3—C1—C2—C3	2.7 (10)	C6—C7—C8—S1	179.5 (6)
O4—C1—C2—C3	−176.5 (6)	O7—C10—C11—N2	5.8 (9)
C1—C2—C3—C4	73.3 (8)	O8—C10—C11—N2	−174.4 (6)
C2—C3—C4—O2	5.1 (11)	O7—C10—C11—C12	131.6 (7)
C2—C3—C4—O1	−176.5 (6)	O8—C10—C11—C12	−48.6 (8)
O6—C5—C6—N1	−176.1 (6)	N2—C11—C12—C13	67.3 (9)
O5—C5—C6—N1	4.8 (9)	C10—C11—C12—C13	−58.5 (9)
O6—C5—C6—C7	−50.7 (9)	C11—C12—C13—S2	177.6 (6)
O5—C5—C6—C7	130.2 (7)	C7—C8—S1—C9	71.9 (9)
N1—C6—C7—C8	70.9 (9)	C12—C13—S2—C14	72.1 (9)
C5—C6—C7—C8	−54.5 (9)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O5^i	0.82	1.83	2.639 (7)	168
O4—H4···O7^ii	0.82	1.84	2.647 (7)	169
N1—H1C···O1^iii	0.90 (3)	2.59 (8)	3.133 (9)	120 (7)
N1—H1C···O2^iv	0.90 (3)	2.09 (7)	2.842 (8)	140 (9)
N1—H1A···O5^iii	0.90 (3)	2.47 (8)	3.168 (8)	135 (9)
N1—H1A···O6^iii	0.90 (3)	2.01 (4)	2.866 (8)	160 (10)
N1—H1B···O6^iv	0.90 (3)	2.03 (5)	2.897 (8)	161 (10)
N2—H2C···O3^v	0.89	2.07	2.849 (8)	146
N2—H2D···O8^vi	0.89	2.07	2.904 (8)	156
N2—H2E···O7^vii	0.89	2.45	3.169 (8)	139
N2—H2E···O8^vii	0.89	2.01	2.875 (8)	163
C6—H6···O5^viii	0.98	2.26	3.206 (9)	162
C11—H11···O7^i	0.98	2.28	3.210 (9)	159
C12—H12B···O8^vii	0.97	2.65	3.415 (10)	136

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