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In the title compound, C9H12NO2+·C4H3O4, the amino acid mol­ecule exists in the cationic form and the maleic acid mol­ecule in the mono-ionized state. In the semi-maleate anion, a nearly symmetric intramolecular O—H...O hydrogen bond is observed. The aggregation pattern observed in the title crystal has striking similarities with those observed in L-phenyl­alanine L-phenyl­alaninium formate and L-phenyl­alanine L-phenyl­alaninium perchlorate.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536801015240/ci6062sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536801015240/ci6062Isup2.hkl
Contains datablock I

CCDC reference: 175370

Key indicators

  • Single-crystal X-ray study
  • T = 293 K
  • Mean [sigma](C-C) = 0.003 Å
  • R factor = 0.028
  • wR factor = 0.078
  • Data-to-parameter ratio = 7.2

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

General Notes

REFLT_03 From the CIF: _diffrn_reflns_theta_max 67.92 From the CIF: _reflns_number_total 1353 Count of symmetry unique reflns 1352 Completeness (_total/calc) 100.07% TEST3: Check Friedels for noncentro structure Estimate of Friedel pairs measured 1 Fraction of Friedel pairs measured 0.001 Are heavy atom types Z>Si present no Please check that the estimate of the number of Friedel pairs is correct. If it is not, please give the correct count in the _publ_section_exptl_refinement section of the submitted CIF.

Comment top

Phenylalanine, an essential amino acid commonly found in proteins, plays a key role in the formation of a variety of physiologically important chemicals that transmit signals between nerve cells. Previous works on phenylalanine report only the unit-cell dimensions (Khawas & Murthi, 1968; Khawas, 1970, 1971, 1985) and the crystal structure of the D-form with a high agreement factor of 15% (Weissbuch et al., 1990). The crystal structure of L-phenylalanine, however, is yet to be reported. A number of complexes of L-phenylalanine with inorganic acids are already known. The present study, which reports the crystal structure of L-phenylalaninium maleate, (I), is part of a series of X-ray investigations being carried out in our laboratory on amino acid–carboxylic acid complexes. Recently, the crystal structure of glycinium maleate (Rajagopal, Krishnakumar, Mostad & Natarajan, 2001), L-alaninium maleate (Alagar et al., 2001) and β-alaninium maleate (Rajagopal, Krishnakumar & Natarajan, 2001) have been reported.

Fig. 1 shows the molecular structure of (I) with the atom-numbering scheme adopted. The amino acid molecule exists in the cationic form with a positively charged amino group and an uncharged carboxylic acid group. The phenylalaninium cation has the gauche- conformation with a χ1 value of -59.3 (2)°. This is different from the values observed in L-phenylalanine L-phenylalaninium formate with χ1 = 72.3 (4) and 70.8 (4)°, respectively, for the zwitterion and the cation (Gorbitz & Etter, 1992). The maleic acid molecule exists in the mono-ionized state (i.e. as a semi-maleate anion). In the semi-maleate anion, a nearly symmetric intramolecular hydrogen bond with a proton shared between the O3 and O5 atoms is observed as in the crystal structures of complexes of maleic acid with DL– and L-arginine (Ravishankar et al., 1998) and L-histidine and L-lysine (Pratap et al., 2000). However, in the crystal structures of maleic acid itself (James & Williams, 1974), glycinium maleate and L-alaninium maleate, this intramolecular hydrogen bond is asymmetric.

Fig. 2 shows the packing of the molecules of (I) viewed down the b axis. The phenylalaninium cations and the semimaleate anions form hydrogen-bonded double chains in which they alternate along the c axis and are held together by N—H···O hydrogen bonds. The double chain, on either side, is flanked by the hydrophobic side chains of phenylalanine leading to alternating hydrophilic and hydrophobic zones along the a axis. These double chains form an infinite two-dimensional network extending along the b axis, interconnected through O—H···O, N—H···O and C—H···O hydrogen bonds. The aggregation pattern observed in (I) has striking similarities with those observed in L-phenylalanine L-phenylalaninium formate (Gorbitz & Etter, 1992) and L-phenylalanine L-phenylalaninium perchlorate (Srinivasan & Rajaram, 1997).

Experimental top

Colorless single crystals of (I) were grown as transparent needles from a saturated aqueous solution containing L-alanine and maleic acid in a 1:1 stoichiometric ratio.

Refinement top

The absolute configuration of L-phenylalaninium maleate was not established by the analysis but is known from the configuration of the starting reagents. The H atoms were placed at calculated positions and were allowed to ride on their respective parent atoms with HFIX instructions using SHELXL97 (Sheldrick, 1997) defaults. The H atom shared between O3 and O5 atoms of the semimaleate anion is, however, refined isotropically.

Computing details top

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: CAD-4 Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 1999); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The molecular structure of (I) with the atom-numbering scheme and 50% probability displacement ellipsoids.
[Figure 2] Fig. 2. Packing of the molecules of (I) viewed down the b axis.
L-Phenylalaninium maleate top
Crystal data top
C9H12NO2+·C4H3O4F(000) = 296
Mr = 281.26Dx = 1.407 Mg m3
Dm = 1.41 Mg m3
Dm measured by flotation in mixture of xylene and bromoform
Monoclinic, P21Cu Kα radiation, λ = 1.54180 Å
a = 11.0560 (9) ÅCell parameters from 25 reflections
b = 5.3326 (4) Åθ = 28–42°
c = 11.4712 (7) ŵ = 0.96 mm1
β = 101.07 (1)°T = 293 K
V = 663.73 (8) Å3Needle, colorless
Z = 20.40 × 0.10 × 0.10 mm
Data collection top
Enraf-Nonius CAD-4
diffractometer
1294 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.015
Graphite monochromatorθmax = 67.9°, θmin = 3.9°
ω–2θ scansh = 130
Absorption correction: ψ scan
(North et al., 1968)
k = 06
Tmin = 0.82, Tmax = 0.91l = 1313
1424 measured reflections2 standard reflections every 100 reflections
1353 independent reflections intensity decay: <2%
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.028H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.078 w = 1/[σ2(Fo2) + (0.0418P)2 + 0.0901P]
where P = (Fo2 + 2Fc2)/3
S = 1.13(Δ/σ)max < 0.001
1353 reflectionsΔρmax = 0.12 e Å3
187 parametersΔρmin = 0.12 e Å3
1 restraintExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.052 (3)
Crystal data top
C9H12NO2+·C4H3O4V = 663.73 (8) Å3
Mr = 281.26Z = 2
Monoclinic, P21Cu Kα radiation
a = 11.0560 (9) ŵ = 0.96 mm1
b = 5.3326 (4) ÅT = 293 K
c = 11.4712 (7) Å0.40 × 0.10 × 0.10 mm
β = 101.07 (1)°
Data collection top
Enraf-Nonius CAD-4
diffractometer
1294 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)
Rint = 0.015
Tmin = 0.82, Tmax = 0.912 standard reflections every 100 reflections
1424 measured reflections intensity decay: <2%
1353 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0281 restraint
wR(F2) = 0.078H atoms treated by a mixture of independent and constrained refinement
S = 1.13Δρmax = 0.12 e Å3
1353 reflectionsΔρmin = 0.12 e Å3
187 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
xyzUiso*/Ueq
O10.21671 (16)0.2656 (4)0.40613 (13)0.0593 (5)
H10.18840.37560.35880.089*
O20.09656 (12)0.4396 (3)0.51853 (11)0.0427 (4)
O30.89837 (18)0.3761 (4)0.88035 (14)0.0600 (5)
O40.86654 (15)0.1424 (4)0.72068 (13)0.0556 (5)
O50.86833 (19)0.3497 (4)1.08272 (15)0.0626 (5)
O60.81953 (17)0.0653 (4)1.20320 (13)0.0623 (5)
N10.12481 (14)0.0781 (4)0.67720 (15)0.0465 (5)
H1A0.13590.05710.72350.070*
H1B0.04450.10810.65470.070*
H1C0.16110.20950.71720.070*
C10.16094 (16)0.2707 (4)0.49675 (16)0.0341 (4)
C20.17990 (17)0.0341 (4)0.57051 (18)0.0379 (5)
H20.13160.09860.52400.045*
C30.31263 (17)0.0598 (5)0.60380 (19)0.0424 (5)
H3A0.31230.22020.64370.051*
H3B0.34350.08840.53130.051*
C40.40088 (16)0.1127 (4)0.68253 (17)0.0384 (5)
C50.4201 (2)0.0880 (6)0.8048 (2)0.0537 (6)
H50.37850.03620.83830.064*
C60.5001 (2)0.2454 (7)0.8774 (2)0.0645 (8)
H60.51150.22740.95950.077*
C70.5628 (2)0.4274 (7)0.8300 (2)0.0619 (7)
H70.61700.53250.87940.074*
C80.5454 (2)0.4546 (6)0.7089 (2)0.0621 (7)
H80.58750.57870.67600.074*
C90.4650 (2)0.2971 (5)0.6359 (2)0.0513 (6)
H90.45400.31590.55400.062*
C100.86352 (19)0.1716 (4)0.82772 (18)0.0420 (5)
C110.8215 (2)0.0398 (5)0.89285 (19)0.0470 (5)
H110.79840.18260.84740.056*
C120.8112 (2)0.0586 (5)1.00627 (19)0.0489 (5)
H120.78510.21461.02790.059*
C130.8346 (2)0.1277 (5)1.10374 (19)0.0460 (5)
H30.884 (3)0.355 (8)0.975 (3)0.091 (10)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0771 (11)0.0642 (12)0.0418 (8)0.0283 (10)0.0245 (7)0.0151 (8)
O20.0488 (7)0.0392 (9)0.0417 (7)0.0089 (7)0.0129 (6)0.0095 (7)
O30.0919 (12)0.0431 (10)0.0479 (9)0.0199 (9)0.0205 (8)0.0143 (8)
O40.0729 (10)0.0562 (11)0.0411 (8)0.0106 (9)0.0195 (7)0.0131 (8)
O50.1022 (14)0.0415 (10)0.0455 (9)0.0062 (10)0.0175 (8)0.0174 (8)
O60.0829 (11)0.0662 (13)0.0419 (8)0.0039 (11)0.0224 (8)0.0079 (9)
N10.0374 (8)0.0532 (12)0.0491 (9)0.0006 (9)0.0087 (7)0.0233 (10)
C10.0340 (8)0.0335 (10)0.0326 (9)0.0003 (9)0.0011 (7)0.0034 (8)
C20.0381 (9)0.0306 (10)0.0416 (10)0.0019 (9)0.0008 (7)0.0051 (9)
C30.0431 (10)0.0310 (10)0.0508 (11)0.0058 (9)0.0031 (8)0.0029 (10)
C40.0296 (8)0.0379 (11)0.0463 (10)0.0051 (9)0.0040 (7)0.0050 (9)
C50.0501 (11)0.0598 (16)0.0488 (12)0.0092 (13)0.0031 (9)0.0130 (12)
C60.0602 (14)0.083 (2)0.0460 (12)0.0126 (16)0.0003 (10)0.0015 (15)
C70.0472 (11)0.0696 (19)0.0659 (15)0.0112 (14)0.0033 (10)0.0129 (15)
C80.0525 (12)0.0627 (17)0.0724 (15)0.0194 (14)0.0154 (11)0.0028 (15)
C90.0483 (11)0.0581 (16)0.0485 (11)0.0093 (13)0.0116 (9)0.0053 (12)
C100.0459 (10)0.0411 (12)0.0400 (10)0.0007 (10)0.0108 (8)0.0112 (10)
C110.0616 (12)0.0360 (12)0.0434 (11)0.0081 (11)0.0100 (9)0.0150 (10)
C120.0650 (13)0.0383 (12)0.0441 (11)0.0061 (12)0.0121 (9)0.0068 (10)
C130.0524 (11)0.0478 (14)0.0390 (11)0.0055 (11)0.0115 (9)0.0096 (10)
Geometric parameters (Å, º) top
O1—C11.307 (2)C3—H3B0.97
O1—H10.82C4—C91.379 (3)
O2—C11.203 (3)C4—C51.384 (3)
O3—C101.270 (3)C5—C61.378 (4)
O3—H31.13 (3)C5—H50.93
O4—C101.244 (2)C6—C71.366 (4)
O5—C131.278 (3)C6—H60.93
O5—H31.28 (3)C7—C81.373 (4)
O6—C131.230 (3)C7—H70.93
N1—C21.486 (3)C8—C91.381 (4)
N1—H1A0.89C8—H80.93
N1—H1B0.89C9—H90.93
N1—H1C0.89C10—C111.476 (3)
C1—C21.511 (3)C11—C121.331 (3)
C2—C31.528 (3)C11—H110.93
C2—H20.98C12—C131.481 (3)
C3—C41.508 (3)C12—H120.93
C3—H3A0.97
C1—O1—H1109.5C6—C5—C4120.7 (2)
C10—O3—H3106 (2)C6—C5—H5119.6
C13—O5—H3107 (2)C4—C5—H5119.6
C2—N1—H1A109.5C7—C6—C5120.5 (2)
C2—N1—H1B109.5C7—C6—H6119.7
H1A—N1—H1B109.5C5—C6—H6119.7
C2—N1—H1C109.5C6—C7—C8119.7 (2)
H1A—N1—H1C109.5C6—C7—H7120.2
H1B—N1—H1C109.5C8—C7—H7120.2
O2—C1—O1124.68 (19)C7—C8—C9119.8 (2)
O2—C1—C2122.17 (17)C7—C8—H8120.1
O1—C1—C2113.08 (18)C9—C8—H8120.1
N1—C2—C1107.14 (17)C4—C9—C8121.2 (2)
N1—C2—C3111.81 (16)C4—C9—H9119.4
C1—C2—C3115.91 (17)C8—C9—H9119.4
N1—C2—H2107.2O4—C10—O3120.9 (2)
C1—C2—H2107.2O4—C10—C11118.3 (2)
C3—C2—H2107.2O3—C10—C11120.76 (18)
C4—C3—C2115.43 (19)C12—C11—C10130.3 (2)
C4—C3—H3A108.4C12—C11—H11114.9
C2—C3—H3A108.4C10—C11—H11114.9
C4—C3—H3B108.4C11—C12—C13130.7 (2)
C2—C3—H3B108.4C11—C12—H12114.6
H3A—C3—H3B107.5C13—C12—H12114.6
C9—C4—C5118.1 (2)O6—C13—O5121.5 (2)
C9—C4—C3121.64 (19)O6—C13—C12118.9 (2)
C5—C4—C3120.3 (2)O5—C13—C12119.6 (2)
O2—C1—C2—N19.4 (2)C5—C6—C7—C80.4 (5)
O1—C1—C2—N1173.33 (17)C6—C7—C8—C90.3 (4)
O2—C1—C2—C3135.0 (2)C5—C4—C9—C80.6 (4)
O1—C1—C2—C347.7 (2)C3—C4—C9—C8179.8 (2)
N1—C2—C3—C459.3 (2)C7—C8—C9—C40.4 (4)
C1—C2—C3—C463.9 (2)O4—C10—C11—C12179.0 (2)
C2—C3—C4—C988.8 (2)O3—C10—C11—C120.6 (4)
C2—C3—C4—C591.5 (3)C10—C11—C12—C132.2 (4)
C9—C4—C5—C60.7 (4)C11—C12—C13—O6179.3 (3)
C3—C4—C5—C6179.7 (2)C11—C12—C13—O51.5 (4)
C4—C5—C6—C70.6 (4)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O3—H3···O51.13 (3)1.28 (3)2.412 (2)175 (4)
O1—H1···O4i0.821.732.547 (2)170
N1—H1A···O5ii0.892.292.999 (2)137
N1—H1A···O6ii0.892.203.068 (3)164
N1—H1B···O2iii0.892.453.077 (2)128
N1—H1B···O4iv0.892.253.011 (2)144
N1—H1C···O6v0.892.102.947 (3)159
C2—H2···O2vi0.982.493.324 (3)142
C2—H2···O2iii0.982.483.073 (2)118
C11—H11···O3vi0.932.603.239 (3)127
C12—H12···O5vi0.932.533.303 (3)140
Symmetry codes: (i) x+1, y+1/2, z+1; (ii) x+1, y1/2, z+2; (iii) x, y1/2, z+1; (iv) x1, y, z; (v) x+1, y+1/2, z+2; (vi) x, y1, z.

Experimental details

Crystal data
Chemical formulaC9H12NO2+·C4H3O4
Mr281.26
Crystal system, space groupMonoclinic, P21
Temperature (K)293
a, b, c (Å)11.0560 (9), 5.3326 (4), 11.4712 (7)
β (°) 101.07 (1)
V3)663.73 (8)
Z2
Radiation typeCu Kα
µ (mm1)0.96
Crystal size (mm)0.40 × 0.10 × 0.10
Data collection
DiffractometerEnraf-Nonius CAD-4
diffractometer
Absorption correctionψ scan
(North et al., 1968)
Tmin, Tmax0.82, 0.91
No. of measured, independent and
observed [I > 2σ(I)] reflections
1424, 1353, 1294
Rint0.015
(sin θ/λ)max1)0.601
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.028, 0.078, 1.13
No. of reflections1353
No. of parameters187
No. of restraints1
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.12, 0.12

Computer programs: CAD-4 Software (Enraf-Nonius, 1989), CAD-4 Software, SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), PLATON (Spek, 1999), SHELXL97.

Selected geometric parameters (Å, º) top
O1—C11.307 (2)C3—C41.508 (3)
O2—C11.203 (3)C4—C91.379 (3)
O3—C101.270 (3)C4—C51.384 (3)
O4—C101.244 (2)C5—C61.378 (4)
O5—C131.278 (3)C6—C71.366 (4)
O5—H31.28 (3)C7—C81.373 (4)
O6—C131.230 (3)C8—C91.381 (4)
N1—C21.486 (3)C10—C111.476 (3)
C1—C21.511 (3)C11—C121.331 (3)
C2—C31.528 (3)C12—C131.481 (3)
O2—C1—O1124.68 (19)C6—C7—C8119.7 (2)
O2—C1—C2122.17 (17)C7—C8—C9119.8 (2)
O1—C1—C2113.08 (18)C4—C9—C8121.2 (2)
N1—C2—C1107.14 (17)O4—C10—O3120.9 (2)
N1—C2—C3111.81 (16)O4—C10—C11118.3 (2)
C1—C2—C3115.91 (17)O3—C10—C11120.76 (18)
C4—C3—C2115.43 (19)C12—C11—C10130.3 (2)
C9—C4—C5118.1 (2)C11—C12—C13130.7 (2)
C9—C4—C3121.64 (19)O6—C13—O5121.5 (2)
C5—C4—C3120.3 (2)O6—C13—C12118.9 (2)
C6—C5—C4120.7 (2)O5—C13—C12119.6 (2)
C7—C6—C5120.5 (2)
O2—C1—C2—N19.4 (2)O1—C1—C2—C347.7 (2)
O1—C1—C2—N1173.33 (17)N1—C2—C3—C459.3 (2)
O2—C1—C2—C3135.0 (2)C1—C2—C3—C463.9 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O3—H3···O51.13 (3)1.28 (3)2.412 (2)175 (4)
O1—H1···O4i0.821.732.547 (2)170
N1—H1A···O5ii0.892.292.999 (2)137
N1—H1A···O6ii0.892.203.068 (3)164
N1—H1B···O2iii0.892.453.077 (2)128
N1—H1B···O4iv0.892.253.011 (2)144
N1—H1C···O6v0.892.102.947 (3)159
C2—H2···O2vi0.982.493.324 (3)142
C2—H2···O2iii0.982.483.073 (2)118
C11—H11···O3vi0.932.603.239 (3)127
C12—H12···O5vi0.932.533.303 (3)140
Symmetry codes: (i) x+1, y+1/2, z+1; (ii) x+1, y1/2, z+2; (iii) x, y1/2, z+1; (iv) x1, y, z; (v) x+1, y+1/2, z+2; (vi) x, y1, z.
 

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