(IUCr) Redetermination of L-tryptophan hydrobromide

Volume 65
Part 6
Pages o1291-o1292
June 2009

Received 7 May 2009
Accepted 8 May 2009
Online 14 May 2009

Key indicators
Single-crystal X-ray study
T = 100 K
Mean (C-C) = 0.003 Å
R = 0.027
wR = 0.063
Data-to-parameter ratio = 18.6
Details

Redetermination of L-tryptophan hydrobromide

Kirsty Stewart ^a ^*

^aSchool of Chemical and Physical Sciences, University of KwaZulu-Natal, Scottsville 3209, South Africa
Correspondence e-mail: stewart@ukzn.ac.za

The redetermined crystal structure of the title compound, C₁₁H₁₃N₂O₂⁺·Br^-, is reported. Data collection at 100 K about three crystallographic axes resulted in a crystal structure with significantly higher precision in comparison to the two-dimensional data collected at 176 K [Takigawa et al. [(1966) Bull. Chem. Soc. Jpn, 39, 2369-2378]. The carboxyl group and indole ring system are planar, with maximum deviations of 0.002 (2) and 0.007 (2) Å, respectively, and make an angle of 70.17 (1)° with each other. The molecules are arranged in double layers of carboxyl and amino groups parallel to the ab plane, stabilized by an extensive network of N-HBr and O-HBr hydrogen bonds. The polar layer is held together by a network of three N-HBr hydrogen bonds and one O-HBr hydrogen bond. In the non-polar layer, the indole rings are linked mainly by electrostatic N-HC interactions between the polarized bond N-H (H is [delta] ⁺) of the pyrrole unit and two of the ring C atoms ( [delta] ^-) of the benzene rings of adjacent molecules. The distances of these electrostatic interactions are 2.57 and 2.68 Å, respectively. C-HO and C-H [pi] interactions are also present.

Related literature

For a previous determination of the crystal structure of the title compound, see: Takigawa et al. (1966). Study of crystal structures of amino acids and their complexes has provided information about aggregation and the effect of other molecules on their interactions and molecular properties, see: Vijayan (1988); Prasad & Vijayan (1993). For the structure of histidine hydrochloride monohydrate, see: Takigawa et al. (1966). Donohue & Caron (1964). The structures of many amino acids with non-polar side chains feature a double-layered arrangement, see: Harding & Long (1968); Torii & Iitaka (1970, 1971, 1973).

Experimental

Crystal data

C₁₁H₁₃N₂O₂⁺·Br^-
M_r = 285.13
Monoclinic, P 2₁
a = 7.6272 (3) Å
b = 5.3840 (2) Å
c = 14.4358 (5) Å
= 100.688 (3)°
V = 582.52 (4) Å³
Z = 2
Mo K radiation
= 3.52 mm^-1
T = 100 K
0.40 × 0.15 × 0.15 mm

Data collection

Oxford Xcalibur2 CCD diffractometer
Absorption correction: multi-scan (SCALE3 ABSPACK in CrysAlis RED; Oxford Diffraction, 2008 $[Oxford Diffraction (2008). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.]$ ) T_min = 0.334, T_max = 0.621
5749 measured reflections
2731 independent reflections
2507 reflections with I > 2(I)
R_int = 0.024

Refinement

R[F² > 2(F²)] = 0.027
wR(F²) = 0.063
S = 1.01
2731 reflections
147 parameters
1 restraint
H-atom parameters constrained
_max = 0.33 e Å^-3
_min = -1.14 e Å^-3
Absolute structure: Flack (1983), 523 Freidel pairs
Flack parameter: 0.009 (9)

Table 1
Hydrogen-bond geometry (Å, °)

D-HA	D-H	HA	DA	D-HA
C7-H4Cg1ⁱ	0.95	2.66	3.494 (3)	146
N1-H5Cg2ⁱ	0.88	2.72	3.406 (2)	136
N2-H11Br1ⁱⁱ	0.91	2.56	3.3208 (17)	142
N2-H12Br1ⁱⁱⁱ	0.91	2.42	3.322 (3)	173
N2-H13Br1^iv	0.91	2.52	3.320 (3)	147
C4-H1Br1ⁱⁱⁱ	0.95	2.85	3.750 (2)	159
C10-H9O1^v	1.00	2.49	3.404 (3)	153
C10-H9O1ⁱⁱ	1.00	2.56	3.199 (3)	121
O2-H10Br1	0.84	2.34	3.173 (2)	169
Symmetry codes: (i) $[-x, y-{\script{1\over 2}}, -z+1]$ ; (ii) $[-x+1, y-{\script{1\over 2}}, -z+2]$ ; (iii) x-1, y-1, z; (iv) x-1, y, z; (v) x, y-1, z. Cg1 is the centroid of the N1/C1-C3/C8 ring and Cg2 is the centroid of the C3-C8 ring.

Data collection: CrysAlis CCD (Oxford Diffraction, 2008 $[Oxford Diffraction (2008). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.]$ ); cell refinement: CrysAlis RED (Oxford Diffraction, 2008 $[Oxford Diffraction (2008). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.]$ ); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: AT2781 ).

Acknowledgements

The author gratefully acknowledges financial support from the University of Kwazulu-Natal. Thanks are also due to Ms C. Janse Van Rensburg for the mass spectrum analysis.

References

Donohue, J. & Caron, A. (1964). Acta Cryst. 17, 1178-1180.
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837-838.
Flack, H. D. (1983). Acta Cryst. A39, 876-881.
Harding, M. M. & Long, H. A. (1968). Acta Cryst. B24, 1096-1102.
Oxford Diffraction (2008). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.
Prasad, G. S. & Vijayan, M. (1993). Acta Cryst. B49, 348-356.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.
Takigawa, T., Ashida, T., Sasada, Y. & Kakudo, M. (1966). Bull. Chem. Soc. Jpn, 39, 2369-2378.
Torii, K. & Iitaka, Y. (1970). Acta Cryst. B26, 1317-1326.
Torii, K. & Iitaka, Y. (1971). Acta Cryst. B27, 2237-2246.
Torii, K. & Iitaka, Y. (1973). Acta Cryst. B29, 2799-2807.
Vijayan, M. (1988). Prog. Biophys. Mol. Biol. 52, 71-99.

organic compounds