Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536801014350/ya6047sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536801014350/ya6047Isup2.hkl |
CCDC reference: 175351
Key indicators
- Single-crystal X-ray study
- T = 293 K
- Mean (C-C) = 0.012 Å
- H-atom completeness 70%
- R factor = 0.069
- wR factor = 0.220
- Data-to-parameter ratio = 7.6
checkCIF results
No syntax errors found ADDSYM reports no extra symmetry
Alert Level C:
ABSMU_01 Alert C The ratio of given/expected absorption coefficient lies outside the range 0.99 <> 1.01 Calculated value of mu = 0.106 Value of mu given = 0.110 STRVAL_01 From the CIF: _refine_ls_abs_structure_Flack 0.000 From the CIF: _refine_ls_abs_structure_Flack_su 4.000 Alert C Flack test results are meaningless. General Notes
FORMU_01 There is a discrepancy between the atom counts in the _chemical_formula_sum and the formula from the _atom_site* data. Atom count from _chemical_formula_sum:C18 H23 N3 O7 Atom count from the _atom_site data: C18 H16 N3 O7 CELLZ_01 From the CIF: _cell_formula_units_Z 2 From the CIF: _chemical_formula_sum C18 H23 N3 O7 TEST: Compare cell contents of formula and atom_site data atom Z*formula cif sites diff C 36.00 36.00 0.00 H 46.00 32.00 14.00 N 6.00 6.00 0.00 O 14.00 14.00 0.00 Difference between formula and atom_site contents detected. WARNING: H atoms missing from atom site list. Is this intentional? CHEMW_03 From the CIF: _cell_formula_units_Z 2 From the CIF: _chemical_formula_weight 393.39 TEST: Calculate formula weight from _atom_site_* atom mass num sum C 12.01 18.00 216.20 N 14.01 3.00 42.02 O 16.00 7.00 111.99 H 1.01 16.00 16.13 Calculated formula weight 386.34 The ratio of given/expected molecular weight as calculated from the _atom_site* data lies outside the range 0.99 <> 1.01 REFLT_03 From the CIF: _diffrn_reflns_theta_max 25.00 From the CIF: _reflns_number_total 1895 Count of symmetry unique reflns 1899 Completeness (_total/calc) 99.79% TEST3: Check Friedels for noncentro structure Estimate of Friedel pairs measured 0 Fraction of Friedel pairs measured 0.000 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.
0 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
2 Alert Level C = Please check
The title compound was crystallized from an aqueous solution of a 2:1 stoichiometric ratio of L-phenylalanine and nitric acid by slow evaporation.
H atoms bonded to C atoms were placed in geometrically calculated positions and allowed to ride on the attached atom. Attempts to introduce H atoms attached to the amino N atom yielded a slight increase in all discrepancy values. Therefore, these H atoms were not included in the final refinement.
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, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 1999); software used to prepare material for publication: SHELXL97.
2C9H11NO2·H+·NO3− | F(000) = 416 |
Mr = 393.39 | Dx = 1.361 Mg m−3 Dm = 1.350 Mg m−3 Dm measured by flotation in a mixture of carbon tetrachloride and xylene |
Monoclinic, P21 | Mo Kα radiation, λ = 0.71073 Å |
a = 12.536 (16) Å | Cell parameters from 25 reflections |
b = 5.378 (4) Å | θ = 14.5–23.4° |
c = 14.962 (9) Å | µ = 0.11 mm−1 |
β = 107.83 (8)° | T = 293 K |
V = 960.2 (15) Å3 | Needle, colorless |
Z = 2 | 0.45 × 0.3 × 0.15 mm |
Enraf-Nonius sealed tube diffractometer | 1356 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.000 |
Graphite monochromator | θmax = 25.0°, θmin = 2.5° |
ω–2θ scans | h = −14→14 |
Absorption correction: ψ scan (North et al., 1968) | k = 0→6 |
Tmin = 0.963, Tmax = 0.984 | l = 0→17 |
1895 measured reflections | 3 standard reflections every 60 min |
1895 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)] = 0.069 | H-atom parameters constrained |
wR(F2) = 0.220 | w = 1/[σ2(Fo2) + (0.1548P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.09 | (Δ/σ)max < 0.001 |
1895 reflections | Δρmax = 0.30 e Å−3 |
250 parameters | Δρmin = −0.34 e Å−3 |
3 restraints | Absolute structure: Flack H D (1983) |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0 (4) |
2C9H11NO2·H+·NO3− | V = 960.2 (15) Å3 |
Mr = 393.39 | Z = 2 |
Monoclinic, P21 | Mo Kα radiation |
a = 12.536 (16) Å | µ = 0.11 mm−1 |
b = 5.378 (4) Å | T = 293 K |
c = 14.962 (9) Å | 0.45 × 0.3 × 0.15 mm |
β = 107.83 (8)° |
Enraf-Nonius sealed tube diffractometer | 1356 reflections with I > 2σ(I) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.000 |
Tmin = 0.963, Tmax = 0.984 | 3 standard reflections every 60 min |
1895 measured reflections | intensity decay: none |
1895 independent reflections |
R[F2 > 2σ(F2)] = 0.069 | H-atom parameters constrained |
wR(F2) = 0.220 | Δρmax = 0.30 e Å−3 |
S = 1.09 | Δρmin = −0.34 e Å−3 |
1895 reflections | Absolute structure: Flack H D (1983) |
250 parameters | Absolute structure parameter: 0 (4) |
3 restraints |
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 | ||
N | 0.0352 (4) | 0.1764 (13) | 0.1120 (4) | 0.0506 (15) | |
O1 | 0.0705 (6) | 0.3884 (15) | 0.1375 (8) | 0.108 (3) | |
O2 | 0.0855 (7) | −0.0024 (15) | 0.1021 (8) | 0.123 (3) | |
O3 | −0.0728 (4) | 0.1534 (12) | 0.0948 (4) | 0.0692 (16) | |
O11 | 0.3355 (3) | 0.1787 (8) | 0.1035 (3) | 0.0440 (11) | |
O12 | 0.5151 (3) | 0.3053 (11) | 0.1553 (4) | 0.0585 (15) | |
C11 | 0.4061 (4) | 0.3366 (13) | 0.1292 (4) | 0.0336 (14) | |
C12 | 0.3784 (4) | 0.6101 (12) | 0.1460 (4) | 0.0357 (14) | |
H12 | 0.4126 | 0.7182 | 0.1096 | 0.043* | |
N11 | 0.2553 (4) | 0.6363 (10) | 0.1084 (4) | 0.0403 (13) | |
C13 | 0.4206 (5) | 0.6877 (13) | 0.2472 (5) | 0.0441 (16) | |
H13A | 0.5017 | 0.6964 | 0.2655 | 0.053* | |
H13B | 0.3933 | 0.8541 | 0.2524 | 0.053* | |
C14 | 0.3887 (5) | 0.5242 (14) | 0.3158 (5) | 0.0443 (16) | |
C15 | 0.2900 (5) | 0.5802 (18) | 0.3395 (5) | 0.0552 (19) | |
H15 | 0.2451 | 0.7153 | 0.3129 | 0.066* | |
C16 | 0.2629 (8) | 0.427 (3) | 0.4034 (7) | 0.089 (4) | |
H16 | 0.1973 | 0.4636 | 0.4173 | 0.106* | |
C17 | 0.3202 (9) | 0.235 (2) | 0.4463 (7) | 0.086 (3) | |
H17 | 0.2972 | 0.1401 | 0.4890 | 0.103* | |
C18 | 0.4198 (9) | 0.1809 (19) | 0.4236 (6) | 0.083 (3) | |
H18 | 0.4641 | 0.0475 | 0.4529 | 0.099* | |
C19 | 0.4531 (6) | 0.3232 (16) | 0.3585 (5) | 0.0526 (18) | |
H19 | 0.5181 | 0.2829 | 0.3440 | 0.063* | |
O21 | 0.7033 (3) | 0.0586 (9) | 0.0675 (3) | 0.0398 (11) | |
O22 | 0.5975 (4) | −0.1005 (9) | 0.1493 (4) | 0.0555 (14) | |
C21 | 0.6790 (4) | −0.1115 (11) | 0.1116 (4) | 0.0341 (14) | |
C22 | 0.7352 (4) | −0.3568 (13) | 0.1249 (4) | 0.0353 (13) | |
H22 | 0.6804 | −0.4810 | 0.0911 | 0.042* | |
N21 | 0.8277 (3) | −0.3404 (12) | 0.0773 (4) | 0.0440 (13) | |
C23 | 0.7814 (5) | −0.4392 (15) | 0.2257 (5) | 0.0482 (16) | |
H23A | 0.7196 | −0.4823 | 0.2490 | 0.058* | |
H23B | 0.8262 | −0.5876 | 0.2285 | 0.058* | |
C24 | 0.8516 (5) | −0.2462 (13) | 0.2884 (5) | 0.0433 (16) | |
C25 | 0.9652 (4) | −0.2161 (14) | 0.2975 (4) | 0.0495 (18) | |
H25 | 0.9992 | −0.3195 | 0.2644 | 0.059* | |
C26 | 1.0260 (4) | −0.0366 (14) | 0.3544 (4) | 0.089 (3) | |
H26 | 1.1013 | −0.0199 | 0.3589 | 0.107* | |
C27 | 0.9804 (7) | 0.1255 (18) | 0.4071 (5) | 0.065 (2) | |
H27 | 1.0232 | 0.2470 | 0.4463 | 0.078* | |
C28 | 0.8721 (7) | 0.0930 (18) | 0.3970 (5) | 0.063 (2) | |
H28 | 0.8376 | 0.1995 | 0.4288 | 0.076* | |
C29 | 0.8102 (6) | −0.0869 (16) | 0.3430 (5) | 0.0551 (19) | |
H29 | 0.7362 | −0.1057 | 0.3422 | 0.066* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N | 0.041 (2) | 0.050 (4) | 0.059 (4) | −0.010 (3) | 0.012 (2) | 0.006 (4) |
O1 | 0.080 (4) | 0.064 (5) | 0.177 (9) | −0.014 (4) | 0.036 (5) | −0.011 (6) |
O2 | 0.093 (5) | 0.070 (5) | 0.223 (11) | 0.037 (5) | 0.072 (6) | 0.003 (6) |
O3 | 0.042 (2) | 0.066 (4) | 0.094 (4) | −0.004 (3) | 0.013 (2) | 0.004 (4) |
O11 | 0.048 (2) | 0.031 (2) | 0.042 (3) | −0.009 (2) | −0.0024 (18) | −0.002 (2) |
O12 | 0.0278 (16) | 0.050 (3) | 0.098 (4) | 0.002 (2) | 0.020 (2) | −0.019 (3) |
C11 | 0.029 (2) | 0.039 (4) | 0.029 (3) | 0.016 (3) | 0.004 (2) | −0.005 (3) |
C12 | 0.040 (3) | 0.034 (4) | 0.037 (3) | 0.001 (3) | 0.017 (2) | 0.003 (3) |
N11 | 0.040 (2) | 0.033 (3) | 0.054 (3) | 0.002 (3) | 0.025 (2) | −0.004 (3) |
C13 | 0.055 (3) | 0.028 (4) | 0.052 (4) | 0.003 (3) | 0.020 (3) | −0.011 (3) |
C14 | 0.053 (3) | 0.042 (4) | 0.043 (4) | −0.011 (3) | 0.021 (3) | −0.002 (4) |
C15 | 0.051 (3) | 0.058 (5) | 0.060 (4) | −0.002 (4) | 0.022 (3) | −0.005 (4) |
C16 | 0.090 (6) | 0.130 (11) | 0.060 (5) | −0.029 (7) | 0.043 (5) | 0.006 (7) |
C17 | 0.123 (8) | 0.087 (8) | 0.052 (5) | −0.033 (7) | 0.033 (5) | 0.003 (6) |
C18 | 0.117 (7) | 0.052 (5) | 0.057 (5) | −0.027 (6) | −0.008 (5) | 0.024 (5) |
C19 | 0.076 (4) | 0.046 (4) | 0.022 (3) | 0.005 (4) | −0.005 (3) | 0.000 (3) |
O21 | 0.048 (2) | 0.035 (2) | 0.041 (2) | 0.006 (2) | 0.0207 (19) | 0.000 (2) |
O22 | 0.056 (2) | 0.036 (3) | 0.087 (4) | 0.001 (2) | 0.040 (3) | 0.004 (3) |
C21 | 0.032 (2) | 0.027 (3) | 0.047 (4) | −0.011 (3) | 0.018 (2) | −0.009 (3) |
C22 | 0.036 (2) | 0.028 (3) | 0.037 (3) | 0.002 (3) | 0.005 (2) | −0.010 (3) |
N21 | 0.036 (2) | 0.051 (3) | 0.044 (3) | 0.014 (3) | 0.012 (2) | −0.003 (3) |
C23 | 0.053 (3) | 0.040 (4) | 0.051 (4) | 0.001 (3) | 0.016 (3) | 0.015 (4) |
C24 | 0.040 (3) | 0.036 (4) | 0.041 (4) | 0.003 (3) | −0.005 (3) | 0.010 (3) |
C25 | 0.046 (3) | 0.066 (5) | 0.037 (4) | −0.004 (4) | 0.013 (3) | −0.006 (4) |
C26 | 0.066 (5) | 0.083 (8) | 0.099 (8) | −0.004 (6) | −0.001 (5) | −0.018 (7) |
C27 | 0.091 (5) | 0.057 (5) | 0.041 (4) | −0.022 (5) | 0.013 (4) | −0.018 (4) |
C28 | 0.083 (5) | 0.061 (6) | 0.040 (4) | 0.012 (5) | 0.010 (4) | −0.010 (4) |
C29 | 0.071 (4) | 0.055 (5) | 0.045 (4) | 0.013 (4) | 0.025 (4) | −0.004 (4) |
N—O2 | 1.184 (9) | C19—H19 | 0.9300 |
N—O1 | 1.240 (10) | O21—C21 | 1.220 (7) |
N—O3 | 1.304 (6) | O22—C21 | 1.311 (7) |
O11—C11 | 1.202 (8) | C21—C22 | 1.480 (9) |
O12—C11 | 1.313 (6) | C22—C23 | 1.508 (9) |
C11—C12 | 1.549 (9) | C22—N21 | 1.539 (7) |
C12—N11 | 1.478 (7) | C22—H22 | 0.9800 |
C12—C13 | 1.502 (9) | C23—C24 | 1.491 (10) |
C12—H12 | 0.9800 | C23—H23A | 0.9700 |
C13—C14 | 1.496 (9) | C23—H23B | 0.9700 |
C13—H13A | 0.9700 | C24—C29 | 1.390 (10) |
C13—H13B | 0.9700 | C24—C25 | 1.398 (7) |
C14—C19 | 1.383 (11) | C25—C26 | 1.3565 |
C14—C15 | 1.420 (8) | C25—H25 | 0.9300 |
C15—C16 | 1.382 (13) | C26—C27 | 1.408 (10) |
C15—H15 | 0.9300 | C26—H26 | 0.9300 |
C16—C17 | 1.307 (16) | C27—C28 | 1.332 (11) |
C16—H16 | 0.9300 | C27—H27 | 0.9300 |
C17—C18 | 1.421 (14) | C28—C29 | 1.344 (12) |
C17—H17 | 0.9300 | C28—H28 | 0.9300 |
C18—C19 | 1.400 (12) | C29—H29 | 0.9300 |
C18—H18 | 0.9300 | ||
O2—N—O1 | 129.1 (6) | C18—C19—H19 | 120.3 |
O2—N—O3 | 117.4 (7) | O21—C21—O22 | 123.7 (6) |
O1—N—O3 | 113.5 (7) | O21—C21—C22 | 123.6 (5) |
O11—C11—O12 | 127.0 (6) | O22—C21—C22 | 112.6 (5) |
O11—C11—C12 | 122.9 (5) | C21—C22—C23 | 114.7 (5) |
O12—C11—C12 | 109.8 (6) | C21—C22—N21 | 106.4 (5) |
N11—C12—C13 | 111.2 (5) | C23—C22—N21 | 111.5 (4) |
N11—C12—C11 | 106.8 (5) | C21—C22—H22 | 108.0 |
C13—C12—C11 | 113.5 (5) | C23—C22—H22 | 108.0 |
N11—C12—H12 | 108.4 | N21—C22—H22 | 108.0 |
C13—C12—H12 | 108.4 | C24—C23—C22 | 113.4 (6) |
C11—C12—H12 | 108.4 | C24—C23—H23A | 108.9 |
C14—C13—C12 | 116.3 (6) | C22—C23—H23A | 108.9 |
C14—C13—H13A | 108.2 | C24—C23—H23B | 108.9 |
C12—C13—H13A | 108.2 | C22—C23—H23B | 108.9 |
C14—C13—H13B | 108.2 | H23A—C23—H23B | 107.7 |
C12—C13—H13B | 108.2 | C29—C24—C25 | 115.1 (7) |
H13A—C13—H13B | 107.4 | C29—C24—C23 | 123.0 (6) |
C19—C14—C15 | 118.8 (7) | C25—C24—C23 | 122.0 (6) |
C19—C14—C13 | 122.4 (6) | C26—C25—C24 | 120.2 (4) |
C15—C14—C13 | 118.9 (7) | C26—C25—H25 | 119.9 |
C16—C15—C14 | 117.6 (9) | C24—C25—H25 | 119.9 |
C16—C15—H15 | 121.2 | C25—C26—C27 | 123.1 (4) |
C14—C15—H15 | 121.2 | C25—C26—H26 | 118.4 |
C17—C16—C15 | 126.7 (9) | C27—C26—H26 | 118.4 |
C17—C16—H16 | 116.7 | C28—C27—C26 | 115.4 (7) |
C15—C16—H16 | 116.7 | C28—C27—H27 | 122.3 |
C16—C17—C18 | 115.8 (9) | C26—C27—H27 | 122.3 |
C16—C17—H17 | 122.1 | C27—C28—C29 | 122.9 (8) |
C18—C17—H17 | 122.1 | C27—C28—H28 | 118.6 |
C19—C18—C17 | 121.7 (10) | C29—C28—H28 | 118.6 |
C19—C18—H18 | 119.1 | C28—C29—C24 | 123.2 (7) |
C17—C18—H18 | 119.1 | C28—C29—H29 | 118.4 |
C14—C19—C18 | 119.5 (8) | C24—C29—H29 | 118.4 |
C14—C19—H19 | 120.3 | ||
O11—C11—C12—N11 | −9.9 (7) | O21—C21—C22—C23 | 126.3 (7) |
O12—C11—C12—N11 | 175.7 (5) | O22—C21—C22—C23 | −56.3 (7) |
O11—C11—C12—C13 | 112.9 (7) | O21—C21—C22—N21 | 2.5 (8) |
O12—C11—C12—C13 | −61.5 (6) | O22—C21—C22—N21 | 179.9 (5) |
N11—C12—C13—C14 | 68.2 (7) | C21—C22—C23—C24 | −49.9 (7) |
C11—C12—C13—C14 | −52.2 (7) | N21—C22—C23—C24 | 71.0 (7) |
C12—C13—C14—C19 | 89.0 (8) | C22—C23—C24—C29 | 97.0 (8) |
C12—C13—C14—C15 | −92.3 (8) | C22—C23—C24—C25 | −84.3 (7) |
C19—C14—C15—C16 | −0.9 (12) | C29—C24—C25—C26 | −1.9 (8) |
C13—C14—C15—C16 | −179.7 (8) | C23—C24—C25—C26 | 179.3 (4) |
C14—C15—C16—C17 | 1.2 (16) | C24—C25—C26—C27 | 0.4 (5) |
C15—C16—C17—C18 | −0.4 (17) | C25—C26—C27—C28 | −0.5 (10) |
C16—C17—C18—C19 | −0.7 (15) | C26—C27—C28—C29 | 2.2 (13) |
C15—C14—C19—C18 | −0.1 (11) | C27—C28—C29—C24 | −3.9 (14) |
C13—C14—C19—C18 | 178.6 (7) | C25—C24—C29—C28 | 3.6 (11) |
C17—C18—C19—C14 | 1.0 (13) | C23—C24—C29—C28 | −177.6 (7) |
Experimental details
Crystal data | |
Chemical formula | 2C9H11NO2·H+·NO3− |
Mr | 393.39 |
Crystal system, space group | Monoclinic, P21 |
Temperature (K) | 293 |
a, b, c (Å) | 12.536 (16), 5.378 (4), 14.962 (9) |
β (°) | 107.83 (8) |
V (Å3) | 960.2 (15) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.11 |
Crystal size (mm) | 0.45 × 0.3 × 0.15 |
Data collection | |
Diffractometer | Enraf-Nonius sealed tube diffractometer |
Absorption correction | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.963, 0.984 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 1895, 1895, 1356 |
Rint | 0.000 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.069, 0.220, 1.09 |
No. of reflections | 1895 |
No. of parameters | 250 |
No. of restraints | 3 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.30, −0.34 |
Absolute structure | Flack H D (1983) |
Absolute structure parameter | 0 (4) |
Computer programs: CAD-4 Software (Enraf-Nonius, 1989), CAD-4 Software, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), PLATON (Spek, 1999), SHELXL97.
O11—C11 | 1.202 (8) | O21—C21 | 1.220 (7) |
O12—C11 | 1.313 (6) | O22—C21 | 1.311 (7) |
O11—C11—C12—N11 | −9.9 (7) | O21—C21—C22—N21 | 2.5 (8) |
N11—C12—C13—C14 | 68.2 (7) | N21—C22—C23—C24 | 71.0 (7) |
C12—C13—C14—C19 | 89.0 (8) | C22—C23—C24—C29 | 97.0 (8) |
C12—C13—C14—C15 | −92.3 (8) | C22—C23—C24—C25 | −84.3 (7) |
Subscribe to Acta Crystallographica Section E: Crystallographic Communications
The full text of this article is available to subscribers to the journal.
- Information on subscribing
- Sample issue
- If you have already subscribed, you may need to register
The crystal structures of L-phenylalanine hydrochloride (Gurskaya & Vainstein, 1963; Al-Karaghouli & Koetzle, 1975), L-phenylalanine L-phenylalaninium formate (Gorbitz & Etter, 1992), bis(L-phenylalanine) sulfate monohydrate (Nagashima et al., 1992) and L-phenylalanine L-phenylalaninium perchlorate (Srinivasan & Rajaram, 1997) have been reported. Even though the title compound, (I), has been studied (Srikrishnan et al., 1984), no structural data are available as the above publication does not contain the atomic coordinates and has a misprint in one of the cell dimensions. Therefore, in the present work, an independent X-ray diffraction study of the title compound was undertaken.
Both phenylalanine residues (1 and 2) have similar geometries (Fig. 1). In both residues, the bond distances C—O [1.313 (6) and 1.311 (7) Å] and C═O [1.202 (8) and 1.220 (7) Å] are nearly equal and the single-bonded O atoms of 1 and 2 (O12···O22) are at a distance of 2.426 (8) Å. This may refer to a short hydrogen bond between the singly bonded carboxyl O atoms (O12···O22), as found in L-phenylalanine L-phenylalaninium perchlorate (Srinivasan & Rajaram, 1997). However, this H atom could not be located objectively. Hence, taking into account the equality of the C—O distances (see above), it can be surmised that the two residues may be connected by either a symmetric hydrogen bond or an asymmetric hydrogen bond with the H atom disordered over two positions.
The conformation angles ψ1 for residues 1 and 2 are -9.9 (7) and 2.5 (8)°, respectively (see Table 1). This tendency towards non-planarity is also found in various amino acids (Lakshminarayanan et al., 1967). The branched side conformation angle χ1 shows a gauche I conformation for both residues [68.2 (7) and 71.0 (7)°], which agrees well with formate and perchlorate complexes. The χ21 [89.0 (8) and 97.0 (8)°] and χ22 [92.3 (8) and -84.3 (7)°] torsion angles indicate that the residues have folded conformation.
The aggregation of hydrophilic zone is along z = 0 plane. The hydrophobic zone at z = 1/2 consists of the phenyl groups of both molecules and is sandwiched between two hydrophilic layers at z = 0 and z = 1 planes (Fig. 2).