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Acta Cryst. (2007). E63, m2318    [ doi:10.1107/S1600536807038263 ]

Dichloridodiglycinezinc dihydrate

S. Mary Navis Priya, B. Varghese, J. Mary Linet and S. Jerome Das

Abstract top

The title compound, [ZnCl2(C2H5NO2)2]·2H2O, crystallizes with one half-molecule in the asymmetric unit and a twofold rotation axis passing through the Zn atom. The glycine molecules are zwitterionic. The eight water molecules present in the unit cell mediate the formation of a three-dimensional hydrogen-bonded network in the crystal structure.

Comment top

Some aminoacids and their complexes are of considerable chemical, optical and biological interest. As part of our ongoing research for finding new nonlinear optics (NLO) materials. We are attempting grow fairly big crystals of aminoacid metal complexes. Crystal structure of dichloro-bis(glycine-O)-zinc glycine (Hariharan et al., 1989), is an NLO material. During our attempt to synthesize this compound, we found that, a new complex, namely, dichloro-bis(glycine)-zinc dihydrate (I), is also formed along with. As the compound is new, it was decided to elucidate its crystal structure. The molecule crystallizes in monoclinic system with space group C2/c with half the molecule in the asymmetric unit. The two–fold axis passing through the Zn atom bisects the molecule. In the crystal structure, zinc atom is tetrahedrally coordinated with two molecules of chlorine and one oxygen each of the carboxyl groups of the glycine. Both glycine molecules are zwitterionic. There are two water molecules in the assymetric unit. The structure packing formes a three dimensional network of hydrogen bonds. The water molecules mediate N—H—O hydrogen bonded link between different units of (I). There are no direct hydrogen bonded link betwen glycine zinc chloride molecules.

Related literature top

For related crystal structures, see: Hariharan et al. (1989).

Experimental top

A supersaturated solution of glycine zinc chloride complex was prepared by dissolving equimolar amounts of glycine and ZnCl2 and stirring continuously using magnetic a stirrer for 12 h. The prepared solution was filtered and kept at room temperature. Crystals were formed in three days. Inspection showed that the crystals were of of two different morphologies. X-ray indexing of these identified them to be belonging to two different complexes viz; dichloro-bis(glycine-O)-zinc glycine (Hariharan et al., 1989) and the title compound (I). Crystals of (I) had diamond shaped morphology while that of the other was irregular polyhedra. The melting point of the material was measured by capillary method using Silicon oil melting point apparatus. The compound melts at 376 K. Thermogravimetric analysis was done using the instrument NETZSCH STA 409 C/CD, which showed the first sharp weight loss starting close to 400 K. This weightloss is assigned to loss of water showing that water is present in the complex after melting.

Refinement top

All the hydrogen atoms were located in difference Fourier map. Water H atoms were isotropically refined. The CH2 hydrogen atoms were geometrically fixed (0.97 Å) and given riding model refinement with Uiso equal to 1.2 UeqC. Program shell used for structure solution, refinement, analysis and graphics - WinGX (Farrugia, 1999).

Computing details top

Data collection: APEX2 (Bruker Nonius, 2004); cell refinement: APEX2 and SAINT-Plus (Bruker Nonius, 2004); data reduction: SAINT-Plus and XPREP (Bruker Nonius, 2004); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97 and WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. The molecule structure of the title compound with atom labels and 50% probability displacement ellipsoids for non-H atoms. H atoms presented as spheres with arbitrary radius. Symmetry code _2: 2 − x, y, 0.5 − z.
[Figure 2] Fig. 2. Packing of molecules in the unit cell. Hydrogen bonds are shown with dotted lines.
Dichloridodiglycinezinc dihydrate top
Crystal data top
[ZnCl2(C2H5NO2)2]·2H2OF000 = 656
Mr = 322.46Dx = 1.880 Mg m−3
Monoclinic, C2/cMelting point: 376 K
Hall symbol: -C 2ycMo Kα radiation
λ = 0.71073 Å
a = 14.4167 (11) ÅCell parameters from 7181 reflections
b = 6.9068 (4) Åθ = 2.8–25.0º
c = 12.9531 (7) ŵ = 2.64 mm−1
β = 117.940 (4)ºT = 293 (2) K
V = 1139.44 (13) Å3Prism, colourless
Z = 40.30 × 0.20 × 0.20 mm
Data collection top
Bruker Kappa APEXII CCD
diffractometer		1008 independent reflections
Radiation source: fine–focus sealed tube1004 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.031
T = 293(2) Kθmax = 25.0º
ω and φ scansθmin = 3.2º
Absorption correction: multi-scan
(Blessing, 1995)		h = −17→17
Tmin = 0.578, Tmax = 0.782k = −8→8
9969 measured reflectionsl = −15→15
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH atoms treated by a mixture of
independent and constrained refinement
R[F2 > 2σ(F2)] = 0.013  w = 1/[σ2(Fo2) + (0.015P)2 + 0.7575P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.034(Δ/σ)max < 0.001
S = 1.12Δρmax = 0.22 e Å−3
1008 reflectionsΔρmin = −0.18 e Å−3
90 parametersExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0604 (12)
Secondary atom site location: difference Fourier map
Crystal data top
[ZnCl2(C2H5NO2)2]·2H2OV = 1139.44 (13) Å3
Mr = 322.46Z = 4
Monoclinic, C2/cMo Kα
a = 14.4167 (11) ŵ = 2.64 mm−1
b = 6.9068 (4) ÅT = 293 (2) K
c = 12.9531 (7) Å0.30 × 0.20 × 0.20 mm
β = 117.940 (4)º
Data collection top
Bruker Kappa APEXII CCD
diffractometer		1008 independent reflections
Absorption correction: multi-scan
(Blessing, 1995)		1004 reflections with I > 2σ(I)
Tmin = 0.578, Tmax = 0.782Rint = 0.031
9969 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.01390 parameters
wR(F2) = 0.034H atoms treated by a mixture of
independent and constrained refinement
S = 1.12Δρmax = 0.22 e Å−3
1008 reflectionsΔρmin = −0.18 e Å−3
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 > 2σ(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
Zn11.00000.28907 (3)0.25000.01935 (11)
Cl10.86678 (2)0.09616 (5)0.13652 (3)0.03154 (12)
O11.10441 (7)0.59018 (14)0.45232 (9)0.0307 (2)
O20.94677 (7)0.47738 (14)0.32473 (8)0.0277 (2)
C11.00740 (10)0.60066 (18)0.39672 (11)0.0208 (3)
C20.95567 (10)0.77847 (18)0.41474 (12)0.0236 (3)
H2A0.98700.80650.49770.028*
H2B0.96930.88800.37690.028*
N10.84174 (10)0.7565 (2)0.36831 (12)0.0292 (3)
H1C0.8099 (15)0.723 (3)0.2924 (19)0.041 (5)*
H1A0.8292 (15)0.671 (3)0.4096 (18)0.046 (5)*
H1B0.8166 (15)0.857 (3)0.3742 (16)0.042 (5)*
O30.76138 (9)0.13810 (16)0.37226 (9)0.0302 (2)
H3A0.8038 (19)0.214 (3)0.423 (2)0.055 (6)*
H3B0.7180 (17)0.118 (3)0.3885 (17)0.049 (6)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Zn10.02036 (14)0.01750 (15)0.02109 (14)0.0000.01046 (10)0.000
Cl10.02259 (18)0.0314 (2)0.0375 (2)−0.00571 (13)0.01148 (15)−0.01057 (14)
O10.0224 (5)0.0349 (5)0.0334 (5)0.0025 (4)0.0118 (4)−0.0037 (4)
O20.0265 (5)0.0256 (5)0.0321 (5)−0.0006 (4)0.0148 (4)−0.0092 (4)
C10.0249 (7)0.0215 (6)0.0202 (6)−0.0001 (5)0.0139 (5)0.0010 (5)
C20.0240 (7)0.0199 (6)0.0285 (7)−0.0018 (5)0.0137 (5)−0.0038 (5)
N10.0244 (6)0.0281 (6)0.0365 (7)0.0018 (5)0.0155 (6)−0.0072 (6)
O30.0261 (5)0.0342 (6)0.0294 (5)0.0022 (5)0.0124 (5)−0.0033 (4)
Geometric parameters (Å, °) top
Zn1—Cl12.2314 (4)C1—O11.2394 (16)
Zn1—Cl1i2.2314 (4)C1—O21.2623 (16)
Zn1—O21.9783 (9)N1—H1C0.90 (2)
Zn1—O2i1.9783 (9)N1—H1A0.87 (2)
C2—N11.4684 (18)N1—H1B0.80 (2)
C2—C11.5107 (17)O3—H3A0.84 (2)
C2—H2A0.9700O3—H3B0.76 (2)
C2—H2B0.9700
N1—C2—C1113.07 (11)C2—N1—H1B109.9 (13)
N1—C2—H2A109.0H1C—N1—H1B107.7 (17)
C1—C2—H2A109.0H1A—N1—H1B107.2 (18)
N1—C2—H2B109.0C1—O2—Zn1120.75 (8)
C1—C2—H2B109.0H3A—O3—H3B107 (2)
H2A—C2—H2B107.8O2—Zn1—O2i97.79 (6)
O1—C1—O2126.28 (12)O2—Zn1—Cl1107.64 (3)
O1—C1—C2117.56 (11)O2i—Zn1—Cl1118.79 (3)
O2—C1—C2116.16 (11)O2—Zn1—Cl1i118.81 (3)
C2—N1—H1C112.0 (12)O2i—Zn1—Cl1i107.69 (3)
C2—N1—H1A109.4 (13)Cl1—Zn1—Cl1i106.67 (2)
H1C—N1—H1A110.6 (17)
N1—C2—C1—O1−166.07 (12)C1—O2—Zn1—O2i−58.56 (9)
N1—C2—C1—O214.67 (17)C1—O2—Zn1—Cl1177.83 (9)
O1—C1—O2—Zn1−20.74 (18)C1—O2—Zn1—Cl1i56.60 (10)
C2—C1—O2—Zn1158.44 (8)
Symmetry codes: (i) −x+2, y, −z+1/2.
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O3—H3A···O1ii0.84 (2)2.04 (2)2.8812 (15)175 (2)
O3—H3B···O1iii0.76 (2)2.16 (2)2.9163 (16)172 (2)
N1—H1C···O3iv0.90 (2)1.97 (2)2.8714 (18)177.4 (17)
N1—H1A···O1ii0.87 (2)2.40 (2)3.1707 (18)147.4 (17)
N1—H1B···O3v0.80 (2)2.09 (2)2.8891 (18)170.5 (18)
Symmetry codes: (ii) −x+2, −y+1, −z+1; (iii) x−1/2, y−1/2, z; (iv) −x+3/2, y+1/2, −z+1/2; (v) x, y+1, z.
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O3—H3A···O1i0.84 (2)2.04 (2)2.8812 (15)175 (2)
O3—H3B···O1ii0.76 (2)2.16 (2)2.9163 (16)172 (2)
N1—H1C···O3iii0.90 (2)1.97 (2)2.8714 (18)177.4 (17)
N1—H1A···O1i0.87 (2)2.40 (2)3.1707 (18)147.4 (17)
N1—H1B···O3iv0.80 (2)2.09 (2)2.8891 (18)170.5 (18)
Symmetry codes: (i) −x+2, −y+1, −z+1; (ii) x−1/2, y−1/2, z; (iii) −x+3/2, y+1/2, −z+1/2; (iv) x, y+1, z.
Acknowledgements top

The authors express their thanks to the Sophisticated Analytical Instruments Facility, Indian Institute of Technology Madras, Chennai, for the X-ray data collection.

references
References top

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Hariharan, M., Rajan, S. S., Srinivasan, R. & Natarajan, S. (1989). Z. Kristallogr. 188, 217–222.

Sheldrick, G. M. (1997). SHELXL97. University of Göttingen, Germany.