Dichloridodiglycinezinc dihydrate

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.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.013
• wR factor = 0.034
• Data-to-parameter ratio = 11.2

checkCIF/PLATON results

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Alert level C
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ ....          ?
PLAT062_ALERT_4_C Rescale T(min) & T(max) by .....................       0.75
PLAT432_ALERT_2_C Short Inter X...Y Contact  C1     ..  C1      ..       3.11 Ang.

Alert level G
ABSTM02_ALERT_3_G  When printed, the submitted absorption T values will be
            replaced by the scaled T values. Since the ratio of scaled T's
            is identical to the ratio of reported T values, the scaling
            does not imply a change to the absorption corrections used in
            the study.
            Ratio of Tmax expected/reported      0.755
            Tmax scaled      0.590 Tmin scaled      0.436
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K
PLAT794_ALERT_5_G Check Predicted Bond Valency for Zn1         (2)       2.05

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   3 ALERT level C = Check and explain
   4 ALERT level G = General alerts; check

   3 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

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S1. Comment

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

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

S2. Experimental

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.

S3. Refinement

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 U_iso equal to 1.2 U_eqC. Program shell used for structure solution, refinement, analysis and graphics - WinGX (Farrugia, 1999).

Computing details

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

	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.
	Fig. 2. Packing of molecules in the unit cell. Hydrogen bonds are shown with dotted lines.

Dichloridodiglycinezinc dihydrate

Crystal data

[ZnCl2(C2H5NO2)2]·2H2O	F(000) = 656
Mr = 322.46	Dx = 1.880 Mg m^−3
Monoclinic, C2/c	Melting point: 376 K
Hall symbol: -C 2yc	Mo Kα radiation, λ = 0.71073 Å
a = 14.4167 (11) Å	Cell parameters from 7181 reflections
b = 6.9068 (4) Å	θ = 2.8–25.0°
c = 12.9531 (7) Å	µ = 2.64 mm^−1
β = 117.940 (4)°	T = 293 K
V = 1139.44 (13) Å^3	Prism, colourless
Z = 4	0.30 × 0.20 × 0.20 mm

Data collection

Bruker Kappa APEXII CCD diffractometer	1008 independent reflections
Radiation source: fine–focus sealed tube	1004 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.031
ω and φ scans	θmax = 25.0°, θmin = 3.2°
Absorption correction: multi-scan (Blessing, 1995)	h = −17→17
Tmin = 0.578, Tmax = 0.782	k = −8→8
9969 measured reflections	l = −15→15

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.013	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.034	w = 1/[σ^2(Fo^2) + (0.015P)^2 + 0.7575P] where P = (Fo^2 + 2Fc^2)/3
S = 1.12	(Δ/σ)max < 0.001
1008 reflections	Δρmax = 0.22 e Å^−3
90 parameters	Δρmin = −0.18 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0604 (12)

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Zn1	1.0000	0.28907 (3)	0.2500	0.01935 (11)
Cl1	0.86678 (2)	0.09616 (5)	0.13652 (3)	0.03154 (12)
O1	1.10441 (7)	0.59018 (14)	0.45232 (9)	0.0307 (2)
O2	0.94677 (7)	0.47738 (14)	0.32473 (8)	0.0277 (2)
C1	1.00740 (10)	0.60066 (18)	0.39672 (11)	0.0208 (3)
C2	0.95567 (10)	0.77847 (18)	0.41474 (12)	0.0236 (3)
H2A	0.9870	0.8065	0.4977	0.028*
H2B	0.9693	0.8880	0.3769	0.028*
N1	0.84174 (10)	0.7565 (2)	0.36831 (12)	0.0292 (3)
H1C	0.8099 (15)	0.723 (3)	0.2924 (19)	0.041 (5)*
H1A	0.8292 (15)	0.671 (3)	0.4096 (18)	0.046 (5)*
H1B	0.8166 (15)	0.857 (3)	0.3742 (16)	0.042 (5)*
O3	0.76138 (9)	0.13810 (16)	0.37226 (9)	0.0302 (2)
H3A	0.8038 (19)	0.214 (3)	0.423 (2)	0.055 (6)*
H3B	0.7180 (17)	0.118 (3)	0.3885 (17)	0.049 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn1	0.02036 (14)	0.01750 (15)	0.02109 (14)	0.000	0.01046 (10)	0.000
Cl1	0.02259 (18)	0.0314 (2)	0.0375 (2)	−0.00571 (13)	0.01148 (15)	−0.01057 (14)
O1	0.0224 (5)	0.0349 (5)	0.0334 (5)	0.0025 (4)	0.0118 (4)	−0.0037 (4)
O2	0.0265 (5)	0.0256 (5)	0.0321 (5)	−0.0006 (4)	0.0148 (4)	−0.0092 (4)
C1	0.0249 (7)	0.0215 (6)	0.0202 (6)	−0.0001 (5)	0.0139 (5)	0.0010 (5)
C2	0.0240 (7)	0.0199 (6)	0.0285 (7)	−0.0018 (5)	0.0137 (5)	−0.0038 (5)
N1	0.0244 (6)	0.0281 (6)	0.0365 (7)	0.0018 (5)	0.0155 (6)	−0.0072 (6)
O3	0.0261 (5)	0.0342 (6)	0.0294 (5)	0.0022 (5)	0.0124 (5)	−0.0033 (4)

Geometric parameters (Å, º)

Zn1—Cl1	2.2314 (4)	C1—O1	1.2394 (16)
Zn1—Cl1^i	2.2314 (4)	C1—O2	1.2623 (16)
Zn1—O2	1.9783 (9)	N1—H1C	0.90 (2)
Zn1—O2^i	1.9783 (9)	N1—H1A	0.87 (2)
C2—N1	1.4684 (18)	N1—H1B	0.80 (2)
C2—C1	1.5107 (17)	O3—H3A	0.84 (2)
C2—H2A	0.9700	O3—H3B	0.76 (2)
C2—H2B	0.9700
N1—C2—C1	113.07 (11)	C2—N1—H1B	109.9 (13)
N1—C2—H2A	109.0	H1C—N1—H1B	107.7 (17)
C1—C2—H2A	109.0	H1A—N1—H1B	107.2 (18)
N1—C2—H2B	109.0	C1—O2—Zn1	120.75 (8)
C1—C2—H2B	109.0	H3A—O3—H3B	107 (2)
H2A—C2—H2B	107.8	O2—Zn1—O2^i	97.79 (6)
O1—C1—O2	126.28 (12)	O2—Zn1—Cl1	107.64 (3)
O1—C1—C2	117.56 (11)	O2^i—Zn1—Cl1	118.79 (3)
O2—C1—C2	116.16 (11)	O2—Zn1—Cl1^i	118.81 (3)
C2—N1—H1C	112.0 (12)	O2^i—Zn1—Cl1^i	107.69 (3)
C2—N1—H1A	109.4 (13)	Cl1—Zn1—Cl1^i	106.67 (2)
H1C—N1—H1A	110.6 (17)
N1—C2—C1—O1	−166.07 (12)	C1—O2—Zn1—O2^i	−58.56 (9)
N1—C2—C1—O2	14.67 (17)	C1—O2—Zn1—Cl1	177.83 (9)
O1—C1—O2—Zn1	−20.74 (18)	C1—O2—Zn1—Cl1^i	56.60 (10)
C2—C1—O2—Zn1	158.44 (8)

Symmetry code: (i) −x+2, y, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3A···O1^ii	0.84 (2)	2.04 (2)	2.8812 (15)	175 (2)
O3—H3B···O1^iii	0.76 (2)	2.16 (2)	2.9163 (16)	172 (2)
N1—H1C···O3^iv	0.90 (2)	1.97 (2)	2.8714 (18)	177.4 (17)
N1—H1A···O1^ii	0.87 (2)	2.40 (2)	3.1707 (18)	147.4 (17)
N1—H1B···O3^v	0.80 (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.