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In the 1:1 adduct formed between L-phenyl­alanine and 4-nitro­phenol [alternative IUPAC name: (2S)-2-ammonio-3-phenyl­propanoate-4-nitro­phenol (1/1)], C9H11NO2·C6H5NO3, the L-phenyl­alanine mol­ecule is in the zwitterionic state. The overall structure is stabilized via strong hydrogen bonding between polar zones and van der Waals inter­actions between non-polar zones, which alternate with the polar zones.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270106049018/gd3062sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270106049018/gd3062Isup2.hkl
Contains datablock I

CCDC reference: 632941

Comment top

Compounds containing amino acids and other molecules or ions have drawn a lot of attention because of the potential applications in domains such as pharmaceutical drugs, nonlinear optics and biochemistry. Much information has thus been gathered on these materials regarding properties such as aggregation patterns, conformational effects caused by the presence of other molecules or ions, nonlinear optical behaviour, ferroelastic/electric properties and phase diagrams. Furthermore, molecules containing π-electron bonds, unbalanced by the presence of polar groups and capable of accepting or giving electrons, are highly polarizable (Pecaut & Bagieu-Beucher, 1993); nitrophenols can also act as π acceptors with other aromatic molecules as well as acidic ligands forming co-compounds/salts through strong hydrogen bonding (In et al., 1997). The synthesis of the title compound has been undertaken in order to obtain a material with strong second harmonic generation properties. However, the non-linear optical properties of L-phenylalanine–4-nitrophenol (LPA–PN) were found to be rather weak in comparison to urea.

The LPA molecule is in the neutral zwitterionic state with a protonated amino group positively charged and a negatively charged carboxyl group. The conformation of this amino acid is described by the torsion angles χ1 = 67.5 (2)° and χ21 = 95.9 (2)° (IUPAC–IUB Commission on Biochemical Nomenclature, 1970); the χ1 value corresponds to a sterically less favoured G+ conformation already found in L-phenylalaninium L-phenylalanine perchlorate (Srinivasan & Rajaram, 1997) and the χ21 angle is indicative of a folded conformation.

The PN molecule shows typical bond lengths and angles (Coppens & Schmidt, 1965). The whole molecule is nearly planar, with the expected small deviations of the nitro and hydroxy O atoms. The latter are deviated towards the same side of the ring plane; one of O atoms of the nitro group lies slightly above the ring plane, whereas the other is positioned below the ring. Asymmetry between the two C—C—O angles due to the repulsion between the H atom and the C atom carrying the hydroxyl group (Hirshfeld, 1964) is also present.

The LPA molecules are bonded to each other via the strong N1—H1B···O1ii hydrogen bond [symmetry code: (ii) x + 1, y, z], forming C(5) chains (Grell et al., 1999) running along the a axis (Fig. 2). These chains are interlinked through additional hydrogen bonds giving rise to hydrophilic sheets parallel to the (001) planes; these sheets are formed by the [100] chains of the LPA molecules and the hydroxy groups of the PN molecules. In each of these sheets the hydrogen bonds N1—H1B···O1ii, O3—H3···O2ii and N1—H1C···O3 generate an R33(8) ring; the bonds N1—H1A···O1i, O3—H3···O2ii and N1—H1C···O3 [symmetry code: (i) −x, y − 1/2, −z + 1] generate an R55(16) ring; and N1—H1B···O1ii and N1—H1A···O1i give rise to an R43(14) ring.

In the hydrogen-bonding scheme, atom N1 acts as the centre of a set of trifurcated donor bonds, atom O1 is the acceptor of two (bifurcated) bonds, whereas atom O3 acts simultaneously as the acceptor of one bond and donor of another. The aromatic rings of both the LPA and the NP molecules border the hydrophilic layers, forming hydrophobic coatings on both sides of the layers. The slabs, made of a central hydrophilic layer and two bordering hydrophobic aromatic ring layers, are repeated along the [001] direction and bond to each other through van der Waals interactions, leading to alternating hydrophilic and hydrophobic zones.

Experimental top

Analytical grade reagent L-phenylalanine (Aldrich) and 4-nitrophenol (Aldrich) were dissolved separately in water and methanol, respectively. The solutions were then added in a 1:1 molar ratio and stirred at 323 K for several hours; the resulting solution was allowed to cool to room temperature and crystals were obtained after two weeks, by slow evaporation at room temperature. A suitable crystal was selected and checked by photographic methods before data collection.

Refinement top

All H atoms were placed at geometrically idealized positions and refined as riding [C—H = 0.97, 0.98 and 0.93 Å for secondary CH2, tertiary CH and aromatic CH respectively; O—H = 0.82 Å; N—H = 0.89 Å; Uiso(H) = 1.2Ueq(C) and Uiso(H) = 1.5Ueq(O,N)]. Examination of the crystal structure with PLATON (Spek, 2003) showed that there are no solvent-accessible voids in the crystal lattice.

Computing details top

Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software; data reduction: PLATON (Spek, 2003); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. An ORTEPII (Johnson, 1976) plot of the title compound. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 2] Fig. 2. The packing, viewed along the c axis, showing the hydrogen-bonding network. H atoms not involved in hydrogen bonds have been omitted for clarity.
[Figure 3] Fig. 3. A view along the b axis of the alternating hydrophilic and hydrophobic slabs. H atoms not involved in intermolecular bonds are not shown.
(2S)-2-ammonio-3-phenylpropanoate–4-nitrophenol (1/1) top
Crystal data top
C9H11NO2·C6H5NO3F(000) = 320
Mr = 304.30Dx = 1.387 Mg m3
Monoclinic, P21Cu Kα radiation, λ = 1.54184 Å
Hall symbol: P 2ybCell parameters from 25 reflections
a = 5.8327 (2) Åθ = 18.7–26.6°
b = 7.0099 (9) ŵ = 0.89 mm1
c = 17.8751 (4) ÅT = 295 K
β = 94.59 (10)°Rod, clear colourless
V = 728.51 (14) Å30.34 × 0.17 × 0.17 mm
Z = 2
Data collection top
Enraf–Nonius CAD-4
diffractometer
2770 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.024
Graphite monochromatorθmax = 72.4°, θmin = 5.0°
Profile data from ω–2θ scansh = 77
Absorption correction: ψ scan
(North et al., 1968)
k = 88
Tmin = 0.72, Tmax = 0.86l = 022
2983 measured reflections3 standard reflections every 180 min
2894 independent reflections intensity decay: 4%
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.042 w = 1/[σ2(Fo2) + (0.0909P)2 + 0.1548P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.140(Δ/σ)max < 0.001
S = 1.17Δρmax = 0.20 e Å3
2894 reflectionsΔρmin = 0.23 e Å3
202 parametersExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
1 restraintExtinction coefficient: 0.018 (2)
Primary atom site location: structure-invariant direct methodsAbsolute structure: Flack (1983), 1320 Friedel pairs
Secondary atom site location: difference Fourier mapAbsolute structure parameter: 0.2 (2)
Crystal data top
C9H11NO2·C6H5NO3V = 728.51 (14) Å3
Mr = 304.30Z = 2
Monoclinic, P21Cu Kα radiation
a = 5.8327 (2) ŵ = 0.89 mm1
b = 7.0099 (9) ÅT = 295 K
c = 17.8751 (4) Å0.34 × 0.17 × 0.17 mm
β = 94.59 (10)°
Data collection top
Enraf–Nonius CAD-4
diffractometer
2770 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)
Rint = 0.024
Tmin = 0.72, Tmax = 0.863 standard reflections every 180 min
2983 measured reflections intensity decay: 4%
2894 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.042H-atom parameters constrained
wR(F2) = 0.140Δρmax = 0.20 e Å3
S = 1.17Δρmin = 0.23 e Å3
2894 reflectionsAbsolute structure: Flack (1983), 1320 Friedel pairs
202 parametersAbsolute structure parameter: 0.2 (2)
1 restraint
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
O10.2825 (2)0.7639 (2)0.45893 (9)0.0372 (4)
O20.1545 (2)0.5043 (2)0.40292 (8)0.0375 (4)
C10.1269 (3)0.6604 (3)0.43587 (10)0.0279 (4)
C20.1199 (3)0.7345 (3)0.45020 (10)0.0273 (4)
H20.14390.77280.50300.033*
N10.2852 (3)0.5779 (3)0.43657 (10)0.0308 (4)
H1A0.27100.48500.46980.046*
H1B0.42810.62330.44140.046*
H1C0.25490.53220.39040.046*
C30.1629 (3)0.9091 (3)0.40118 (12)0.0327 (4)
H3A0.07071.01460.41700.039*
H3B0.32330.94580.40970.039*
C40.1078 (4)0.8773 (3)0.31796 (11)0.0301 (4)
C50.1050 (4)0.9318 (3)0.28386 (13)0.0364 (5)
H50.21470.98470.31260.044*
C60.1545 (4)0.9077 (4)0.20751 (14)0.0430 (5)
H60.29750.94410.18530.052*
C70.0068 (5)0.8299 (4)0.16408 (13)0.0435 (5)
H70.02620.81510.11260.052*
C80.2178 (4)0.7743 (4)0.19757 (13)0.0421 (5)
H80.32650.72050.16860.051*
C90.2685 (4)0.7982 (3)0.27410 (12)0.0352 (5)
H90.41130.76080.29610.042*
O30.4867 (3)0.3450 (3)0.32340 (9)0.0422 (4)
H30.60510.38420.34610.063*
C100.5145 (4)0.3399 (3)0.24837 (11)0.0325 (5)
C110.7123 (4)0.4079 (4)0.21995 (13)0.0388 (5)
H110.82900.46140.25180.047*
C120.7349 (4)0.3956 (4)0.14368 (14)0.0434 (5)
H120.86820.43810.12370.052*
C130.5574 (5)0.3195 (4)0.09767 (13)0.0431 (5)
N20.5863 (6)0.3064 (5)0.01739 (14)0.0678 (8)
O40.7756 (6)0.3292 (8)0.00318 (16)0.1207 (16)
O50.4196 (6)0.2717 (7)0.02521 (13)0.1035 (12)
C140.3574 (4)0.2539 (4)0.12497 (14)0.0448 (6)
H140.23950.20400.09270.054*
C150.3358 (4)0.2639 (4)0.20120 (13)0.0387 (5)
H150.20270.22010.22100.046*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0221 (6)0.0489 (9)0.0410 (8)0.0024 (6)0.0045 (5)0.0029 (7)
O20.0318 (7)0.0420 (8)0.0376 (8)0.0051 (7)0.0035 (6)0.0039 (7)
C10.0228 (8)0.0367 (10)0.0235 (8)0.0013 (8)0.0018 (6)0.0038 (8)
C20.0203 (8)0.0356 (10)0.0258 (8)0.0000 (7)0.0005 (6)0.0017 (7)
N10.0220 (7)0.0371 (8)0.0330 (8)0.0017 (7)0.0006 (6)0.0009 (7)
C30.0280 (9)0.0339 (10)0.0359 (10)0.0035 (8)0.0006 (8)0.0018 (8)
C40.0287 (9)0.0300 (9)0.0316 (10)0.0021 (7)0.0036 (7)0.0048 (8)
C50.0280 (10)0.0412 (11)0.0402 (11)0.0024 (8)0.0043 (8)0.0063 (9)
C60.0353 (11)0.0500 (13)0.0422 (12)0.0038 (10)0.0062 (9)0.0102 (10)
C70.0535 (13)0.0446 (12)0.0319 (10)0.0102 (11)0.0001 (9)0.0040 (9)
C80.0481 (13)0.0427 (12)0.0369 (11)0.0017 (10)0.0120 (9)0.0015 (10)
C90.0296 (10)0.0389 (11)0.0376 (10)0.0033 (8)0.0056 (8)0.0046 (9)
O30.0372 (8)0.0555 (10)0.0337 (8)0.0049 (7)0.0023 (6)0.0079 (7)
C100.0312 (10)0.0338 (11)0.0322 (10)0.0009 (8)0.0003 (8)0.0023 (8)
C110.0345 (11)0.0419 (12)0.0393 (11)0.0042 (9)0.0006 (9)0.0059 (9)
C120.0420 (12)0.0491 (13)0.0400 (12)0.0050 (10)0.0091 (9)0.0002 (10)
C130.0549 (13)0.0433 (12)0.0313 (11)0.0000 (11)0.0035 (9)0.0001 (9)
N20.090 (2)0.0775 (19)0.0361 (12)0.0073 (16)0.0036 (12)0.0016 (12)
O40.110 (2)0.204 (5)0.0529 (14)0.035 (3)0.0366 (15)0.014 (2)
O50.113 (2)0.156 (3)0.0384 (11)0.020 (2)0.0137 (13)0.0094 (16)
C140.0449 (12)0.0469 (13)0.0407 (12)0.0061 (11)0.0091 (9)0.0048 (11)
C150.0324 (10)0.0413 (11)0.0418 (11)0.0045 (9)0.0004 (8)0.0007 (10)
Geometric parameters (Å, º) top
O1—C11.257 (3)C7—H70.9300
O2—C11.247 (3)C8—C91.387 (3)
C1—C21.533 (2)C8—H80.9300
C2—N11.494 (3)C9—H90.9300
C2—C31.538 (3)O3—C101.364 (3)
C2—H20.9800O3—H30.8200
N1—H1A0.8900C10—C111.382 (3)
N1—H1B0.8900C10—C151.393 (3)
N1—H1C0.8900C11—C121.383 (3)
C3—C41.513 (3)C11—H110.9300
C3—H3A0.9700C12—C131.377 (4)
C3—H3B0.9700C12—H120.9300
C4—C91.385 (3)C13—C141.379 (4)
C4—C51.392 (3)C13—N21.461 (3)
C5—C61.383 (3)N2—O41.202 (4)
C5—H50.9300N2—O51.211 (4)
C6—C71.379 (4)C14—C151.380 (3)
C6—H60.9300C14—H140.9300
C7—C81.381 (4)C15—H150.9300
O2—C1—O1126.32 (19)C6—C7—H7120.3
O2—C1—C2117.41 (18)C8—C7—H7120.3
O1—C1—C2116.27 (18)C7—C8—C9120.4 (2)
N1—C2—C1109.47 (16)C7—C8—H8119.8
N1—C2—C3110.79 (16)C9—C8—H8119.8
C1—C2—C3111.64 (16)C4—C9—C8120.4 (2)
N1—C2—H2108.3C4—C9—H9119.8
C1—C2—H2108.3C8—C9—H9119.8
C3—C2—H2108.3C10—O3—H3109.5
C2—N1—H1A109.5O3—C10—C11121.4 (2)
C2—N1—H1B109.5O3—C10—C15117.6 (2)
H1A—N1—H1B109.5C11—C10—C15121.0 (2)
C2—N1—H1C109.5C10—C11—C12119.3 (2)
H1A—N1—H1C109.5C10—C11—H11120.4
H1B—N1—H1C109.5C12—C11—H11120.4
C4—C3—C2114.30 (17)C13—C12—C11119.1 (2)
C4—C3—H3A108.7C13—C12—H12120.4
C2—C3—H3A108.7C11—C12—H12120.4
C4—C3—H3B108.7C12—C13—C14122.3 (2)
C2—C3—H3B108.7C12—C13—N2118.1 (2)
H3A—C3—H3B107.6C14—C13—N2119.6 (2)
C9—C4—C5118.8 (2)O4—N2—O5123.1 (3)
C9—C4—C3121.02 (19)O4—N2—C13118.2 (3)
C5—C4—C3120.1 (2)O5—N2—C13118.7 (3)
C6—C5—C4120.5 (2)C13—C14—C15118.6 (2)
C6—C5—H5119.8C13—C14—H14120.7
C4—C5—H5119.8C15—C14—H14120.7
C7—C6—C5120.4 (2)C14—C15—C10119.6 (2)
C7—C6—H6119.8C14—C15—H15120.2
C5—C6—H6119.8C10—C15—H15120.2
C6—C7—C8119.5 (2)
O2—C1—C2—N113.2 (2)C7—C8—C9—C40.3 (3)
O1—C1—C2—N1166.64 (17)O3—C10—C11—C12178.5 (2)
O2—C1—C2—C3109.9 (2)C15—C10—C11—C121.7 (4)
O1—C1—C2—C370.3 (2)C10—C11—C12—C131.4 (4)
N1—C2—C3—C467.5 (2)C11—C12—C13—C140.4 (4)
C1—C2—C3—C454.8 (2)C11—C12—C13—N2179.4 (3)
C2—C3—C4—C985.6 (2)C12—C13—N2—O413.3 (5)
C2—C3—C4—C595.9 (2)C14—C13—N2—O4165.8 (4)
C9—C4—C5—C60.2 (3)C12—C13—N2—O5167.3 (4)
C3—C4—C5—C6178.3 (2)C14—C13—N2—O513.6 (5)
C4—C5—C6—C70.2 (4)C12—C13—C14—C150.5 (4)
C5—C6—C7—C80.7 (4)N2—C13—C14—C15178.6 (3)
C6—C7—C8—C90.7 (4)C13—C14—C15—C100.2 (4)
C5—C4—C9—C80.2 (3)O3—C10—C15—C14179.3 (2)
C3—C4—C9—C8178.4 (2)C11—C10—C15—C140.8 (4)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···O1i0.892.002.887 (2)172
N1—H1B···O1ii0.891.962.838 (2)170
N1—H1C···O30.892.292.919 (3)128
O3—H3···O2ii0.821.872.678 (3)171
Symmetry codes: (i) x, y1/2, z+1; (ii) x+1, y, z.

Experimental details

Crystal data
Chemical formulaC9H11NO2·C6H5NO3
Mr304.30
Crystal system, space groupMonoclinic, P21
Temperature (K)295
a, b, c (Å)5.8327 (2), 7.0099 (9), 17.8751 (4)
β (°) 94.59 (10)
V3)728.51 (14)
Z2
Radiation typeCu Kα
µ (mm1)0.89
Crystal size (mm)0.34 × 0.17 × 0.17
Data collection
DiffractometerEnraf–Nonius CAD-4
diffractometer
Absorption correctionψ scan
(North et al., 1968)
Tmin, Tmax0.72, 0.86
No. of measured, independent and
observed [I > 2σ(I)] reflections
2983, 2894, 2770
Rint0.024
(sin θ/λ)max1)0.618
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.042, 0.140, 1.17
No. of reflections2894
No. of parameters202
No. of restraints1
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.20, 0.23
Absolute structureFlack (1983), 1320 Friedel pairs
Absolute structure parameter0.2 (2)

Computer programs: CAD-4 Software (Enraf–Nonius, 1989), CAD-4 Software, PLATON (Spek, 2003), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEPII (Johnson, 1976), SHELXL97.

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···O1i0.892.002.887 (2)172
N1—H1B···O1ii0.891.962.838 (2)170
N1—H1C···O30.892.292.919 (3)128
O3—H3···O2ii0.821.872.678 (3)171
Symmetry codes: (i) x, y1/2, z+1; (ii) x+1, y, z.
 

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