organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890

(R)-(1-Ammonio­eth­yl)phospho­nate

aDepartment of Chemistry, University of Aveiro, CICECO, 3810-193 Aveiro, Portugal, and bDepartment of Chemistry, University of Aveiro, QOPNA, 3810-193 Aveiro, Portugal
*Correspondence e-mail: filipe.paz@ua.pt

(Received 28 July 2010; accepted 29 July 2010; online 11 August 2010)

The title compound, C2H8NO3P, crystallizes in its zwitterionic form H3N+CH(CH3)PO(O)(OH). In the crystal, the molecules are linked by N—H⋯O and O—H⋯O hydrogen bonds.

Related literature

For the anti­bacterial activity of the title compound, see: Allen et al. (1979[Allen, J. G., Havas, L., Leicht, E., Lenoxsmith, I. & Nisbet, L. J. (1979). Antimicrob. Agents Chemother. 16, 306-313.]). For the use of the title compound as a co-crystallizing inhibitor on the X-ray structure of the alanine racemase from Bacillus anthracis, a potential anti-anthrax drug target, see: Au et al. (2008[Au, K., Ren, J., Walter, T. S., Harlos, K., Nettleship, J. E., Owens, R. J., Stuart, D. I. & Esnouf, R. M. (2008). Acta Cryst. F64, 327-333.]). For examples of coordination compounds of the title compound, see: Cui et al. (2006[Cui, L.-Y., Sun, Z.-G., Liu, Z.-M., You, W.-S., Zhu, Z.-M., Meng, L., Chen, H. & Dong, D.-P. (2006). Inorg. Chem. Commun. 9, 1232-1234.]); Carraro et al. (2008[Carraro, M., Sartorel, A., Scorrano, G., Maccato, C., Dickman, M. H., Kortz, U. & Bonchio, M. (2008). Angew. Chem. Int. Ed. 47, 7275-7279.]). For a description of the graph-set notation for hydrogen-bonded aggregates, see: Grell et al. (1999[Grell, J., Bernstein, J. & Tinhofer, G. (1999). Acta Cryst. B55, 1030-1043.]). For previous work from our research group on the assembly of coordination polymers using phospho­nic-based mol­ecules, see: Cunha-Silva, Ananias et al. (2009[Cunha-Silva, L., Ananias, D., Carlos, L. D., Paz, F. A. A. & Rocha, J. (2009). Z. Kristallogr. 224, 261-272.]); Cunha-Silva, Lima et al. (2009[Cunha-Silva, L., Lima, S., Ananias, D., Silva, P., Mafra, L., Carlos, L. D., Pillinger, M., Valente, A. A., Paz, F. A. A. & Rocha, J. (2009). J. Mater. Chem. 19, 2618-2632.]); Shi, Cunha-Silva et al. (2008[Shi, F. N., Cunha-Silva, L., Ferreira, R. A. S., Mafra, L., Trindade, T., Carlos, L. D., Paz, F. A. A. & Rocha, J. (2008). J. Am. Chem. Soc. 130, 150-167.]); Shi, Trindade et al. (2008[Shi, F. N., Trindade, T., Rocha, J. & Paz, F. A. A. (2008). Cryst. Growth Des. 8, 3917-3920.]).

[Scheme 1]

Experimental

Crystal data
  • C2H8NO3P

  • Mr = 125.06

  • Orthorhombic, P 21 21 21

  • a = 4.8256 (1) Å

  • b = 10.3928 (3) Å

  • c = 10.4668 (3) Å

  • V = 524.93 (2) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.42 mm−1

  • T = 150 K

  • 0.12 × 0.08 × 0.04 mm

Data collection
  • Bruker X8 Kappa CCD APEXII diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 1997[Sheldrick, G. M. (1997). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.951, Tmax = 0.983

  • 7972 measured reflections

  • 2535 independent reflections

  • 2362 reflections with I > 2σ(I)

  • Rint = 0.027

Refinement
  • R[F2 > 2σ(F2)] = 0.025

  • wR(F2) = 0.070

  • S = 1.07

  • 2535 reflections

  • 77 parameters

  • 7 restraints

  • H atoms treated by a mixture of independent and constrained refinement

  • Δρmax = 0.50 e Å−3

  • Δρmin = −0.26 e Å−3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), 1051 Friedel pairs

  • Flack parameter: 0.00 (8)

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O2—H4⋯O3i 0.92 (1) 1.63 (1) 2.5484 (10) 175 (2)
N1—H1⋯O1ii 0.94 (1) 1.91 (1) 2.8033 (11) 157 (1)
N1—H2⋯O3iii 0.94 (1) 1.90 (1) 2.8369 (12) 178 (1)
N1—H3⋯O1iv 0.95 (1) 1.87 (1) 2.8160 (12) 171 (1)
Symmetry codes: (i) x+1, y, z; (ii) [x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z]; (iii) [-x, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]; (iv) [x-{\script{1\over 2}}, -y+{\script{1\over 2}}, -z].

Data collection: APEX2 (Bruker, 2006[Bruker (2006). APEX2. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT-Plus (Bruker, 2006[Bruker (2006). APEX2. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXTL; molecular graphics: DIAMOND (Brandenburg, 2009[Brandenburg, K. (2009). DIAMOND. Crystal Impact GbR, Bonn, Germany.]); software used to prepare material for publication: SHELXTL.

Supporting information


Comment top

The title compound, R-1-aminoethylphosphonic acid (C2H8NO3P), is the phosphonic analogue of the amino acid alanine and, therefore, it is commonly represented as L-Ala-P (Au et al., 2008). It presents antibacterial activity (Allen et al., 1979) and it has been employed as inhibitor in the crystallization of the enzyme alanine racemase from Bacillus anthracis (Au et al., 2008). Remarkably, only two coordination compounds containing L-Ala-P as ligand are known, namely a racemic coordination polymer of zinc (Cui et al., 2006) and a chiral molybdenum cluster (Carraro et al., 2008). Following our interest in the use of phosphonic acid molecules in the construction of multi-dimensional coordination polymers (Cunha-Silva, Ananias et al., 2009; Cunha-Silva, Lima et al., 2009; Shi, Cunha-Silva et al., 2008; Shi, Trindade et al., 2008), herein we wish to describe the crystal structure of the title compound.

The title compound crystallises in its zwitterionic form in which the acidic phosphonate moiety donates one proton to the amino group (Fig. 1). Individual molecular units are disposed in a zigzag fashion along the [100] direction of the unit cell, leading to the formation of a supramolecular chain held together by a combination of the inner ···O1···H1—N1+—H3··· hydrogen bonds [graph set motif C12(4), Grell et al. (1999) - green dashed bonds in Fig. 2], and the outer isolated O2—H4···O3 interactions (violet dashed bonds in Fig. 2). Supramolecular chains are in turn interconnected in the bc plane via the remnant N1+—H2···O2 hydrogen bonds as depicted in Fig. 3 (orange dashed lines). It is noteworthy that all hydrogen bonding interactions are rather strong and directional: while the internuclear D···A distances range from 2.5484 (10) to 2.8369 (12) Å, the (DHA) are all greater than 157°. As depicted in Fig. 3, the crystal packing promotes a close proximity between the substituent —CH3 groups which point toward each other.

Related literature top

For the antibacterial activity of the title compound, see: Allen et al. (1979). For the use of the title compound as a co-crystallizing inhibitor on the X-ray structure of the alanine racemase from Bacillus anthracis, a potential anti-anthrax drug target, see: Au et al. (2008). For examples of coordination compounds of the title compound, see: Cui et al. (2006); Carraro et al. (2008). For a description of the graph-set notation for hydrogen-bonded aggregates, see: Grell et al. (1999). For previous work from our research group on the assembly of coordination polymers using phosphonic-based molecules, see: Cunha-Silva, Ananias et al. (2009); Cunha-Silva, Lima et al. (2009); Shi, Cunha-Silva et al. (2008); Shi, Trindade et al. (2008).

Experimental top

The title compound was purchased from Sigma-Aldrich (>97.0%, Fluka) and was used as received without purification. Suitable single crystals were grown from an aqueous solution over a period of two weeks.

1H-NMR (300.13 MHz, D2O) δ: 1.27 (dd, 3H, J(1H-1H) = 7.3 Hz and J(1H-31P)= 14.8 Hz, CH3) and 3.19 (dq, 1H, J(1H-1H)= 7.3 Hz and J(1H-31P) = 12.7 Hz, CH).

13C-NMR (75.47 MHz, D2O) δ: 16.4 (d, J(13C-31P) = 2.6 Hz,CH3) and 47.6 (d, J(13C-31P) = 145.1 Hz,CH).

31P-NMR (121.49 MHz, D2O) δ: 14.8 (dq, J(31P-1H) = 13.8 and 14.6 Hz).

Refinement top

Hydrogen atoms bound to carbon were located at their idealized positions and were included in the final model in the riding-motion approximation with C—H = 1.00 Å (tertiary C—H) or 0.98 Å (–CH3). The isotropic thermal displacement parameters for these atoms were fixed at 1.2 (for methine-H) or 1.5 (methyl-H) times Ueq of the respective parent atom.

Hydrogen atoms associated with the protonated —NH3+ group or the pendant —OH moiety were located from difference Fourier maps and were included in the final model with the distances restrained to 0.95 (1) Å and Uiso=1.5×Ueq of the respective parent atom. The H···H distances of the —NH3+ terminal group were further restrained to 1.55 (1) Å in order to ensure a chemically reasonable geometry for this moiety.

Structure description top

The title compound, R-1-aminoethylphosphonic acid (C2H8NO3P), is the phosphonic analogue of the amino acid alanine and, therefore, it is commonly represented as L-Ala-P (Au et al., 2008). It presents antibacterial activity (Allen et al., 1979) and it has been employed as inhibitor in the crystallization of the enzyme alanine racemase from Bacillus anthracis (Au et al., 2008). Remarkably, only two coordination compounds containing L-Ala-P as ligand are known, namely a racemic coordination polymer of zinc (Cui et al., 2006) and a chiral molybdenum cluster (Carraro et al., 2008). Following our interest in the use of phosphonic acid molecules in the construction of multi-dimensional coordination polymers (Cunha-Silva, Ananias et al., 2009; Cunha-Silva, Lima et al., 2009; Shi, Cunha-Silva et al., 2008; Shi, Trindade et al., 2008), herein we wish to describe the crystal structure of the title compound.

The title compound crystallises in its zwitterionic form in which the acidic phosphonate moiety donates one proton to the amino group (Fig. 1). Individual molecular units are disposed in a zigzag fashion along the [100] direction of the unit cell, leading to the formation of a supramolecular chain held together by a combination of the inner ···O1···H1—N1+—H3··· hydrogen bonds [graph set motif C12(4), Grell et al. (1999) - green dashed bonds in Fig. 2], and the outer isolated O2—H4···O3 interactions (violet dashed bonds in Fig. 2). Supramolecular chains are in turn interconnected in the bc plane via the remnant N1+—H2···O2 hydrogen bonds as depicted in Fig. 3 (orange dashed lines). It is noteworthy that all hydrogen bonding interactions are rather strong and directional: while the internuclear D···A distances range from 2.5484 (10) to 2.8369 (12) Å, the (DHA) are all greater than 157°. As depicted in Fig. 3, the crystal packing promotes a close proximity between the substituent —CH3 groups which point toward each other.

For the antibacterial activity of the title compound, see: Allen et al. (1979). For the use of the title compound as a co-crystallizing inhibitor on the X-ray structure of the alanine racemase from Bacillus anthracis, a potential anti-anthrax drug target, see: Au et al. (2008). For examples of coordination compounds of the title compound, see: Cui et al. (2006); Carraro et al. (2008). For a description of the graph-set notation for hydrogen-bonded aggregates, see: Grell et al. (1999). For previous work from our research group on the assembly of coordination polymers using phosphonic-based molecules, see: Cunha-Silva, Ananias et al. (2009); Cunha-Silva, Lima et al. (2009); Shi, Cunha-Silva et al. (2008); Shi, Trindade et al. (2008).

Computing details top

Data collection: APEX2 (Bruker, 2006); cell refinement: SAINT-Plus (Bruker, 2006); data reduction: SAINT-Plus (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2009); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. Molecular structure of the title compound. Displacement ellipsoids are drawn at the 80% probability level and the atomic labeling is provided for all non-hydrogen atoms.
[Figure 2] Fig. 2. Supramolecular one-dimensional zigzag chain running parallel to the [100] direction of the unit cell. The inner N—H···O interactions composing the graph set motif C12(4) are represented as dashed green lines, while the outer O—H···O bonds as violet dashed green lines. For hydrogen bonding geometrical details see Table 1. Symmetry operations used to generate equivalent atoms have been omitted for simplicity.
[Figure 3] Fig. 3. Crystal packing of the title compound viewed in perspective along the [100] direction of the unit cell. Hydrogen bonds are represented as dashed green (intra-chain N—H···O type), violet (O—H···O) or orange (inter-chain N—H···O interactions) lines.
(R)-(1-Ammonioethyl)phosphonate top
Crystal data top
C2H8NO3PF(000) = 264
Mr = 125.06Dx = 1.583 Mg m3
Orthorhombic, P212121Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2abCell parameters from 3869 reflections
a = 4.8256 (1) Åθ = 2.8–35.9°
b = 10.3928 (3) ŵ = 0.42 mm1
c = 10.4668 (3) ÅT = 150 K
V = 524.93 (2) Å3Prism, colourless
Z = 40.12 × 0.08 × 0.04 mm
Data collection top
Bruker X8 Kappa CCD APEXII
diffractometer
2535 independent reflections
Radiation source: fine-focus sealed tube2362 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.027
ω and phi scansθmax = 36.3°, θmin = 3.9°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1997)
h = 78
Tmin = 0.951, Tmax = 0.983k = 1617
7972 measured reflectionsl = 1716
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)] = 0.025H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.070 w = 1/[σ2(Fo2) + (0.0415P)2]
where P = (Fo2 + 2Fc2)/3
S = 1.07(Δ/σ)max < 0.001
2535 reflectionsΔρmax = 0.50 e Å3
77 parametersΔρmin = 0.26 e Å3
7 restraintsAbsolute structure: Flack (1983), 1051 Friedel pairs
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: 0.00 (8)
Crystal data top
C2H8NO3PV = 524.93 (2) Å3
Mr = 125.06Z = 4
Orthorhombic, P212121Mo Kα radiation
a = 4.8256 (1) ŵ = 0.42 mm1
b = 10.3928 (3) ÅT = 150 K
c = 10.4668 (3) Å0.12 × 0.08 × 0.04 mm
Data collection top
Bruker X8 Kappa CCD APEXII
diffractometer
2535 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1997)
2362 reflections with I > 2σ(I)
Tmin = 0.951, Tmax = 0.983Rint = 0.027
7972 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.025H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.070Δρmax = 0.50 e Å3
S = 1.07Δρmin = 0.26 e Å3
2535 reflectionsAbsolute structure: Flack (1983), 1051 Friedel pairs
77 parametersAbsolute structure parameter: 0.00 (8)
7 restraints
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
P10.12299 (5)0.08570 (2)0.11153 (2)0.01023 (6)
O10.15178 (17)0.13133 (7)0.02404 (7)0.01436 (13)
O20.33072 (15)0.02579 (7)0.14607 (8)0.01551 (14)
H40.512 (2)0.0009 (18)0.1437 (15)0.023*
O30.16015 (15)0.03922 (8)0.15035 (8)0.01671 (15)
N10.15332 (19)0.34471 (8)0.15951 (8)0.01264 (14)
H10.290 (2)0.3648 (15)0.0983 (11)0.019*
H20.152 (3)0.4080 (12)0.2239 (10)0.019*
H30.0211 (19)0.3439 (15)0.1171 (13)0.019*
C10.2286 (2)0.21731 (10)0.21766 (9)0.01326 (17)
H1A0.43520.21430.22480.016*
C20.1111 (4)0.20387 (11)0.35212 (10)0.0253 (2)
H2A0.19240.26980.40750.038*
H2B0.15570.11840.38580.038*
H2C0.09060.21480.34950.038*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
P10.00725 (9)0.01088 (9)0.01254 (9)0.00054 (8)0.00037 (8)0.00118 (8)
O10.0141 (3)0.0168 (3)0.0121 (3)0.0005 (3)0.0003 (3)0.0012 (2)
O20.0087 (3)0.0130 (3)0.0248 (4)0.0004 (2)0.0024 (2)0.0025 (3)
O30.0076 (3)0.0195 (3)0.0229 (3)0.0017 (2)0.0002 (3)0.0051 (3)
N10.0126 (3)0.0122 (3)0.0132 (3)0.0000 (3)0.0000 (3)0.0004 (3)
C10.0134 (4)0.0137 (4)0.0126 (4)0.0001 (3)0.0025 (3)0.0011 (3)
C20.0425 (7)0.0216 (5)0.0118 (4)0.0001 (5)0.0004 (5)0.0019 (4)
Geometric parameters (Å, º) top
P1—O11.5025 (8)N1—H20.942 (7)
P1—O31.5051 (8)N1—H30.951 (7)
P1—O21.5742 (8)C1—C21.5238 (16)
P1—C11.8344 (10)C1—H1A1.0000
O2—H40.918 (9)C2—H2A0.9800
N1—C11.5018 (13)C2—H2B0.9800
N1—H10.943 (8)C2—H2C0.9800
O1—P1—O3116.12 (4)N1—C1—C2111.41 (9)
O1—P1—O2112.98 (4)N1—C1—P1110.17 (6)
O3—P1—O2106.25 (4)C2—C1—P1112.80 (8)
O1—P1—C1108.11 (5)N1—C1—H1A107.4
O3—P1—C1109.15 (5)C2—C1—H1A107.4
O2—P1—C1103.46 (4)P1—C1—H1A107.4
P1—O2—H4112.2 (12)C1—C2—H2A109.5
C1—N1—H1107.5 (10)C1—C2—H2B109.5
C1—N1—H2109.1 (9)H2A—C2—H2B109.5
H1—N1—H2109.6 (9)C1—C2—H2C109.5
C1—N1—H3113.3 (10)H2A—C2—H2C109.5
H1—N1—H3107.7 (9)H2B—C2—H2C109.5
H2—N1—H3109.5 (10)
O1—P1—C1—N133.30 (8)O1—P1—C1—C2158.48 (8)
O3—P1—C1—N193.86 (7)O3—P1—C1—C231.32 (10)
O2—P1—C1—N1153.33 (7)O2—P1—C1—C281.49 (9)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H4···O3i0.92 (1)1.63 (1)2.5484 (10)175 (2)
N1—H1···O1ii0.94 (1)1.91 (1)2.8033 (11)157 (1)
N1—H2···O3iii0.94 (1)1.90 (1)2.8369 (12)178 (1)
N1—H3···O1iv0.95 (1)1.87 (1)2.8160 (12)171 (1)
Symmetry codes: (i) x+1, y, z; (ii) x+1/2, y+1/2, z; (iii) x, y+1/2, z+1/2; (iv) x1/2, y+1/2, z.

Experimental details

Crystal data
Chemical formulaC2H8NO3P
Mr125.06
Crystal system, space groupOrthorhombic, P212121
Temperature (K)150
a, b, c (Å)4.8256 (1), 10.3928 (3), 10.4668 (3)
V3)524.93 (2)
Z4
Radiation typeMo Kα
µ (mm1)0.42
Crystal size (mm)0.12 × 0.08 × 0.04
Data collection
DiffractometerBruker X8 Kappa CCD APEXII
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1997)
Tmin, Tmax0.951, 0.983
No. of measured, independent and
observed [I > 2σ(I)] reflections
7972, 2535, 2362
Rint0.027
(sin θ/λ)max1)0.833
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.025, 0.070, 1.07
No. of reflections2535
No. of parameters77
No. of restraints7
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.50, 0.26
Absolute structureFlack (1983), 1051 Friedel pairs
Absolute structure parameter0.00 (8)

Computer programs: APEX2 (Bruker, 2006), SAINT-Plus (Bruker, 2006), SAINT-Plus (Bruker, 2005), SHELXTL (Sheldrick, 2008), DIAMOND (Brandenburg, 2009).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H4···O3i0.918 (9)1.633 (9)2.5484 (10)174.7 (17)
N1—H1···O1ii0.943 (8)1.911 (8)2.8033 (11)157.0 (14)
N1—H2···O3iii0.942 (7)1.895 (8)2.8369 (12)177.6 (14)
N1—H3···O1iv0.951 (7)1.873 (8)2.8160 (12)170.7 (14)
Symmetry codes: (i) x+1, y, z; (ii) x+1/2, y+1/2, z; (iii) x, y+1/2, z+1/2; (iv) x1/2, y+1/2, z.
 

Acknowledgements

We are grateful to the Fundação para a Ciência e a Tecnologia (FCT, Portugal) for their general financial support (R&D project PTDC/QUI-QUI/098098/2008), for the post-doctoral and PhD research grants Nos. SFRH/BPD/63736/2009 (to JAF) and SFRH/BD/66371/2009 (to SMFV), and for specific funding toward the purchase of the diffractometer.

References

First citationAllen, J. G., Havas, L., Leicht, E., Lenoxsmith, I. & Nisbet, L. J. (1979). Antimicrob. Agents Chemother. 16, 306–313.  CrossRef PubMed CAS Web of Science Google Scholar
First citationAu, K., Ren, J., Walter, T. S., Harlos, K., Nettleship, J. E., Owens, R. J., Stuart, D. I. & Esnouf, R. M. (2008). Acta Cryst. F64, 327–333.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationBrandenburg, K. (2009). DIAMOND. Crystal Impact GbR, Bonn, Germany.  Google Scholar
First citationBruker (2005). SAINT-Plus. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationBruker (2006). APEX2. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationCarraro, M., Sartorel, A., Scorrano, G., Maccato, C., Dickman, M. H., Kortz, U. & Bonchio, M. (2008). Angew. Chem. Int. Ed. 47, 7275–7279.  Web of Science CSD CrossRef CAS Google Scholar
First citationCui, L.-Y., Sun, Z.-G., Liu, Z.-M., You, W.-S., Zhu, Z.-M., Meng, L., Chen, H. & Dong, D.-P. (2006). Inorg. Chem. Commun. 9, 1232–1234.  Web of Science CSD CrossRef CAS Google Scholar
First citationCunha-Silva, L., Ananias, D., Carlos, L. D., Paz, F. A. A. & Rocha, J. (2009). Z. Kristallogr. 224, 261–272.  Web of Science CSD CrossRef CAS Google Scholar
First citationCunha-Silva, L., Lima, S., Ananias, D., Silva, P., Mafra, L., Carlos, L. D., Pillinger, M., Valente, A. A., Paz, F. A. A. & Rocha, J. (2009). J. Mater. Chem. 19, 2618–2632.  Web of Science CSD CrossRef CAS Google Scholar
First citationFlack, H. D. (1983). Acta Cryst. A39, 876–881.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationGrell, J., Bernstein, J. & Tinhofer, G. (1999). Acta Cryst. B55, 1030–1043.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSheldrick, G. M. (1997). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationShi, F. N., Cunha-Silva, L., Ferreira, R. A. S., Mafra, L., Trindade, T., Carlos, L. D., Paz, F. A. A. & Rocha, J. (2008). J. Am. Chem. Soc. 130, 150–167.  Web of Science CSD CrossRef PubMed CAS Google Scholar
First citationShi, F. N., Trindade, T., Rocha, J. & Paz, F. A. A. (2008). Cryst. Growth Des. 8, 3917–3920.  Web of Science CSD CrossRef CAS Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Follow Acta Cryst. E
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds