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In the title compound, [Zn(C3H7NO2)2Cl2], both the alanine mol­ecules in the asymmetric unit exist as zwitterions. Zn has a distorted tetrahedral coordination, with two Cl atoms and two O atoms, one from each of the two crystallographically independent alanine ligands in the asymmetric unit.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536802003148/ci6103sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536802003148/ci6103Isup2.hkl
Contains datablock I

CCDC reference: 182591

Key indicators

  • Single-crystal X-ray study
  • T = 293 K
  • Mean [sigma](C-C) = 0.005 Å
  • R factor = 0.040
  • wR factor = 0.114
  • Data-to-parameter ratio = 15.6

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry








Comment top

Halogeno zinc–amino acid complexes are interesting as zinc is known to compete successfully with cadmium for protein binding sites. Zinc also plays an important biological role in the formation of a structural motif called `zinc fingers` which is characteristic of certain proteins that bind to DNA. The present study reports the crystal structure of a complex of DL-alanine with zinc chloride, namely dichlorobis(DL-alanine)zinc(II). Alanine, a non-essential amino acid commonly present in proteins, is hydrophobic and non-polar. A precise determination of the crystal strucure of DL-alanine itself was recently carried out in our laboratory (Subha Nandhini et al., 2001a). The crystal structure of a complex of sarcosine with zinc chloride, namely trichloro(sarcosinio)zinc(II) monohydrate (Krishnakumar et al., 2001), in which the amino acid exhibits an unusual cationic form, was also elucidated in our laboratory. A similar ionization state was observed in the case of L-histidine with zinc chloride (Foster et al., 1993). The crystal structures of dichlorobis(sarcosinato)zinc(II) (Subha Nandhini et al., 2001b) and dichlorobis(DL-valine)zinc(II) (Subha Nandhini et al., 2001c) have also been determined recently in our laboratory.

The molecular structure and atom-numbering scheme are shown in Fig.1. Both the alanine molecules in the asymmetric unit coordinating as ligands to Zn exist as zwitterions. However, the C1—O1 and C1—O2 bond lengths in molecule A [1.265 (4) and 1.232 (4) Å, respectively] and molecule B [1.273 (4) and 1.230 (4) Å, respectively] show significant deviations from those usually exhibited by zwitterions. These deviations may be due to the fact that the O1 atoms of both molecule A and B participate in the coordination environment around Zn. The torsion angles O1A—Zn1—O1B—C1B [172.7 (2)°] and O1B—Zn1—O1A—C1A [69.1 (3)°] describe the relative orientation of molecules A and B with respect to the metal. The coordination environment around Zn is remarkably similar to those observed in the structures of ZnCl2 with sarcosine (Subha Nandhini et al., 2001b), glycine (Hariharan et al., 1989) and L-proline (Yukawa et al., 1985). Fig.2 shows the packing of the molecules of (I), viewed down the b axis. The molecules aggregate into a layered arrangement parallel to the bc plane. These layers form hydrogen-bonded double layers involving inversion and glide-related molecules. The adjacent double layers have no hydrogen-bonded interactions between them and are held together by van der Waals interactions.

Experimental top

Colourless single crystals of (I) were grown as transparent plates, by slow evaporation of the saturated water–acetone mixture containing DL-alanine and zinc chloride, in stoichiometric ratio. The density was determined by the flotation method using a liquid mixture of carbon tetrachloride and bromoform.

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. Displacement ellipsoids are shown at the 50% probability level.
[Figure 2] Fig. 2. Packing diagram of (I), viewed down the b axis.
Dichlorobis(DL-alanine)zinc(II) top
Crystal data top
C6H14Cl2N2O4ZnF(000) = 640
Mr = 314.46Dx = 1.780 Mg m3
Dm = 1.77 (2) Mg m3
Dm measured by flotation method
Monoclinic, P21/cCu Kα radiation, λ = 1.5418 Å
Hall symbol: -P 2ybcCell parameters from 25 reflections
a = 9.996 (5) Åθ = 16–24°
b = 13.622 (4) ŵ = 7.12 mm1
c = 8.616 (3) ÅT = 293 K
β = 90.30 (1)°Plates, colourless
V = 1173.2 (8) Å30.20 × 0.14 × 0.10 mm
Z = 4
Data collection top
Enraf-Nonius CAD-4
diffractometer
2097 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.044
Graphite monochromatorθmax = 67.9°, θmin = 4.4°
ω–2θ scansh = 1211
Absorption correction: ψ scans
(North et al., 1968)
k = 160
Tmin = 0.35, Tmax = 0.49l = 010
2282 measured reflections2 standard reflections every 100 reflections
2134 independent reflections intensity decay: <1%
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)] = 0.040H-atom parameters constrained
wR(F2) = 0.114 w = 1/[σ2(Fo2) + (0.0605P)2 + 2.8047P]
where P = (Fo2 + 2Fc2)/3
S = 1.15(Δ/σ)max < 0.001
2134 reflectionsΔρmax = 0.51 e Å3
137 parametersΔρmin = 0.96 e Å3
0 restraintsExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0030 (4)
Crystal data top
C6H14Cl2N2O4ZnV = 1173.2 (8) Å3
Mr = 314.46Z = 4
Monoclinic, P21/cCu Kα radiation
a = 9.996 (5) ŵ = 7.12 mm1
b = 13.622 (4) ÅT = 293 K
c = 8.616 (3) Å0.20 × 0.14 × 0.10 mm
β = 90.30 (1)°
Data collection top
Enraf-Nonius CAD-4
diffractometer
2097 reflections with I > 2σ(I)
Absorption correction: ψ scans
(North et al., 1968)
Rint = 0.044
Tmin = 0.35, Tmax = 0.492 standard reflections every 100 reflections
2282 measured reflections intensity decay: <1%
2134 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0400 restraints
wR(F2) = 0.114H-atom parameters constrained
S = 1.15Δρmax = 0.51 e Å3
2134 reflectionsΔρmin = 0.96 e Å3
137 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
Zn10.71059 (4)0.04277 (3)0.75589 (5)0.0200 (2)
Cl10.51376 (9)0.10007 (7)0.84660 (10)0.0291 (3)
Cl20.86984 (9)0.14992 (6)0.83302 (11)0.0300 (3)
O2A0.5833 (3)0.15896 (17)0.7783 (3)0.0256 (6)
O1A0.7617 (3)0.07791 (19)0.8666 (3)0.0338 (6)
N1A0.6195 (3)0.3120 (2)0.9625 (3)0.0248 (6)
H1A10.54190.28540.98980.037*
H1A20.61280.33610.86680.037*
H1A30.64030.36021.02810.037*
C1A0.6836 (3)0.1509 (2)0.8610 (4)0.0196 (7)
C2A0.7258 (4)0.2359 (2)0.9670 (4)0.0228 (7)
H2A0.73310.21101.07350.027*
C3A0.8595 (4)0.2787 (3)0.9212 (6)0.0405 (10)
H3A10.88220.33150.99030.061*
H3A20.85420.30310.81680.061*
H3A30.92700.22870.92740.061*
O2B0.6619 (3)0.16576 (18)0.4876 (3)0.0277 (6)
O1B0.7220 (3)0.01135 (18)0.5308 (3)0.0282 (6)
N1B0.7036 (3)0.1605 (2)0.1863 (3)0.0258 (7)
H1B10.72810.15390.08770.039*
H1B20.61500.16560.19140.039*
H1B30.74090.21440.22590.039*
C1B0.7058 (3)0.0861 (2)0.4441 (4)0.0188 (7)
C2B0.7484 (4)0.0733 (2)0.2764 (4)0.0226 (7)
H2B0.70480.01470.23380.027*
C3B0.8994 (5)0.0616 (4)0.2620 (5)0.0437 (11)
H3B10.92250.05380.15470.066*
H3B20.94300.11880.30300.066*
H3B30.92780.00480.31920.066*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Zn10.0300 (3)0.0110 (3)0.0190 (3)0.00029 (16)0.00362 (19)0.00056 (15)
Cl10.0321 (5)0.0294 (5)0.0259 (4)0.0067 (3)0.0070 (3)0.0013 (3)
Cl20.0323 (5)0.0193 (4)0.0384 (5)0.0049 (3)0.0009 (4)0.0013 (3)
O2A0.0390 (15)0.0208 (12)0.0171 (11)0.0033 (11)0.0009 (10)0.0004 (9)
O1A0.0322 (14)0.0180 (13)0.0511 (17)0.0045 (11)0.0027 (12)0.0166 (12)
N1A0.0340 (16)0.0184 (14)0.0219 (14)0.0061 (12)0.0003 (12)0.0087 (11)
C1A0.0258 (17)0.0144 (15)0.0188 (15)0.0036 (13)0.0077 (13)0.0020 (12)
C2A0.0319 (19)0.0151 (16)0.0213 (16)0.0027 (14)0.0005 (13)0.0057 (13)
C3A0.030 (2)0.027 (2)0.064 (3)0.0053 (16)0.0006 (19)0.0130 (19)
O2B0.0398 (15)0.0196 (12)0.0240 (12)0.0075 (11)0.0076 (10)0.0002 (10)
O1B0.0502 (16)0.0144 (12)0.0202 (12)0.0005 (11)0.0062 (11)0.0007 (9)
N1B0.0336 (17)0.0252 (15)0.0187 (14)0.0002 (13)0.0022 (12)0.0048 (11)
C1B0.0217 (16)0.0164 (15)0.0183 (15)0.0016 (13)0.0036 (12)0.0013 (12)
C2B0.0362 (19)0.0131 (15)0.0188 (16)0.0012 (14)0.0055 (14)0.0017 (12)
C3B0.043 (2)0.048 (3)0.040 (2)0.021 (2)0.0195 (19)0.013 (2)
Geometric parameters (Å, º) top
Zn1—O1A1.967 (3)C3A—H3A20.96
Zn1—O1B1.990 (3)C3A—H3A30.96
Zn1—Cl22.2572 (11)O1B—C1B1.273 (4)
Zn1—Cl12.2599 (13)O2B—C1B1.230 (4)
O2A—C1A1.232 (4)N1B—C2B1.487 (4)
O1A—C1A1.265 (4)N1B—H1B10.89
N1A—C2A1.485 (4)N1B—H1B20.89
N1A—H1A10.89N1B—H1B30.89
N1A—H1A20.89C1B—C2B1.518 (4)
N1A—H1A30.89C2B—C3B1.523 (6)
C1A—C2A1.531 (4)C2B—H2B0.98
C2A—C3A1.513 (6)C3B—H3B10.96
C2A—H2A0.98C3B—H3B20.96
C3A—H3A10.96C3B—H3B30.96
O1A—Zn1—O1B106.06 (12)C2A—C3A—H3A3109.5
O1A—Zn1—Cl2102.53 (9)H3A1—C3A—H3A3109.5
O1B—Zn1—Cl2112.45 (8)H3A2—C3A—H3A3109.5
O1A—Zn1—Cl1110.20 (9)C1B—O1B—Zn1113.1 (2)
O1B—Zn1—Cl1117.77 (9)C2B—N1B—H1B1109.5
Cl2—Zn1—Cl1106.78 (5)C2B—N1B—H1B2109.5
C1A—O1A—Zn1118.7 (2)H1B1—N1B—H1B2109.5
C2A—N1A—H1A1109.5C2B—N1B—H1B3109.5
C2A—N1A—H1A2109.5H1B1—N1B—H1B3109.5
H1A1—N1A—H1A2109.5H1B2—N1B—H1B3109.5
C2A—N1A—H1A3109.5O2B—C1B—O1B124.8 (3)
H1A1—N1A—H1A3109.5O2B—C1B—C2B119.6 (3)
H1A2—N1A—H1A3109.5O1B—C1B—C2B115.5 (3)
O2A—C1A—O1A126.3 (3)N1B—C2B—C1B108.6 (3)
O2A—C1A—C2A119.9 (3)N1B—C2B—C3B109.7 (3)
O1A—C1A—C2A113.8 (3)C1B—C2B—C3B111.9 (3)
N1A—C2A—C3A110.9 (3)N1B—C2B—H2B108.9
N1A—C2A—C1A108.5 (3)C1B—C2B—H2B108.9
C3A—C2A—C1A112.1 (3)C3B—C2B—H2B108.9
N1A—C2A—H2A108.4C2B—C3B—H3B1109.5
C3A—C2A—H2A108.4C2B—C3B—H3B2109.5
C1A—C2A—H2A108.4H3B1—C3B—H3B2109.5
C2A—C3A—H3A1109.5C2B—C3B—H3B3109.5
C2A—C3A—H3A2109.5H3B1—C3B—H3B3109.5
H3A1—C3A—H3A2109.5H3B2—C3B—H3B3109.5
O1B—Zn1—O1A—C1A69.1 (3)O1A—Zn1—O1B—C1B172.7 (2)
Cl2—Zn1—O1A—C1A172.8 (3)Cl2—Zn1—O1B—C1B61.4 (3)
Cl1—Zn1—O1A—C1A59.4 (3)Cl1—Zn1—O1B—C1B63.4 (3)
Zn1—O1A—C1A—O2A8.6 (5)Zn1—O1B—C1B—O2B13.6 (5)
Zn1—O1A—C1A—C2A173.1 (2)Zn1—O1B—C1B—C2B164.7 (2)
O2A—C1A—C2A—N1A7.4 (4)O2B—C1B—C2B—N1B10.3 (5)
O1A—C1A—C2A—N1A174.2 (3)O1B—C1B—C2B—N1B171.2 (3)
O2A—C1A—C2A—C3A115.4 (4)O2B—C1B—C2B—C3B110.9 (4)
O1A—C1A—C2A—C3A63.0 (4)O1B—C1B—C2B—C3B67.5 (4)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1A—H1A1···O2Bi0.892.152.864 (4)137
N1A—H1A2···Cl1i0.892.393.204 (3)152
N1A—H1A3···O1Bii0.892.222.960 (4)141
N1B—H1B1···Cl2iii0.892.623.478 (3)163
N1B—H1B2···O2Aiv0.892.002.886 (4)172
N1B—H1B3···Cl2v0.892.433.317 (3)173
C2B—H2B···Cl1iv0.982.773.680 (4)154
Symmetry codes: (i) x+1, y+1/2, z+3/2; (ii) x, y+1/2, z+1/2; (iii) x, y, z1; (iv) x+1, y, z+1; (v) x, y1/2, z1/2.

Experimental details

Crystal data
Chemical formulaC6H14Cl2N2O4Zn
Mr314.46
Crystal system, space groupMonoclinic, P21/c
Temperature (K)293
a, b, c (Å)9.996 (5), 13.622 (4), 8.616 (3)
β (°) 90.30 (1)
V3)1173.2 (8)
Z4
Radiation typeCu Kα
µ (mm1)7.12
Crystal size (mm)0.20 × 0.14 × 0.10
Data collection
DiffractometerEnraf-Nonius CAD-4
diffractometer
Absorption correctionψ scans
(North et al., 1968)
Tmin, Tmax0.35, 0.49
No. of measured, independent and
observed [I > 2σ(I)] reflections
2282, 2134, 2097
Rint0.044
(sin θ/λ)max1)0.601
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.040, 0.114, 1.15
No. of reflections2134
No. of parameters137
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.51, 0.96

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
Zn1—O1A1.967 (3)C1A—C2A1.531 (4)
Zn1—O1B1.990 (3)C2A—C3A1.513 (6)
Zn1—Cl22.2572 (11)O1B—C1B1.273 (4)
Zn1—Cl12.2599 (13)O2B—C1B1.230 (4)
O2A—C1A1.232 (4)C1B—C2B1.518 (4)
O1A—C1A1.265 (4)C2B—C3B1.523 (6)
O1A—Zn1—O1B106.06 (12)O1A—Zn1—Cl1110.20 (9)
O1A—Zn1—Cl2102.53 (9)O1B—Zn1—Cl1117.77 (9)
O1B—Zn1—Cl2112.45 (8)Cl2—Zn1—Cl1106.78 (5)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1A—H1A1···O2Bi0.892.152.864 (4)136.5
N1A—H1A2···Cl1i0.892.393.204 (3)152.2
N1A—H1A3···O1Bii0.892.222.960 (4)140.9
N1B—H1B1···Cl2iii0.892.623.478 (3)162.7
N1B—H1B2···O2Aiv0.892.002.886 (4)171.6
N1B—H1B3···Cl2v0.892.433.317 (3)172.7
C2B—H2B···Cl1iv0.982.773.680 (4)154.4
Symmetry codes: (i) x+1, y+1/2, z+3/2; (ii) x, y+1/2, z+1/2; (iii) x, y, z1; (iv) x+1, y, z+1; (v) x, y1/2, z1/2.
 

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