Bis(μ-4-formyl-2-methoxy­phenolato)bis­[aqua­chloridozinc(II)] dihydrate

In the centrosymmetric dinuclear mol­ecule of the title compound, [Zn₂(C₈H₇O₃)₂Cl₂(H₂O)₂], the Zn ions are bridged by two phenolate O atoms, with a Zn...Zn distance of 3.1216 (6) Å, forming a Zn₂O₂ four-membered ring. Each Zn coordination is completed by a further bidentate 4-hydr­oxy-3-methoxy­benzaldehyde ion, one chloride ion and one water mol­ecule. The water mol­ecules are involved in hydrogen bonds, which stabilize the crystal structure.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.030
• wR factor = 0.087
• Data-to-parameter ratio = 16.9

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT412_ALERT_2_C Short Intra XH3 .. XHn     H5A    ..  H7A     ..       1.83 Ang.
PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........          4
PLAT764_ALERT_4_C Overcomplete CIF Bond List Detected (Rep/Expd) .       1.12 Ratio

Alert level G
PLAT794_ALERT_5_G Check Predicted Bond Valency for Zn1         (2)       2.11
PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints .......          6

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

   0 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
   2 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

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S1. Comment

In recent years, phenolic compounds have attracted the interest of researchers because they show promise of being powerful antioxidants that can protect the human body from free radicals (Rice-Evans et al., 1996). Their complexes are becoming increasingly important as biochemical, analytical and antimicrobial reagents (Tumer et al., 1999). We report here the zinc dinuclear vanillin complex bis[aqua-chloro-(4-hydroxy-3-methoxybenzaldehyde)-zinc(II)] dihydrate (I).

The structural features of the I dimer shown in Fig. 1. The complex is centrosymmetric with an inversion center in the middle of the Zn₂O₂ core. Similar binuclear zinc(II) phenol O-bridged complexes with a planar Zn₂O₂ core have been reported by Olmstead et al., (1991) and Kunert et al., (2000). Each Zn atom employs one oxygen donor - O1, from the vanillin ligands to form the Zn₂O₂ unit, while the second oxygen atom, O2, from this bridging vanillin ligand is terminally coordinated to the Zn atom. This complex contains a central four-membered Zn—O—Zn—O ring can be described as parallelogram. The atom O1 as a bridge atom coordinate with two Zn atoms. The Zn—O bond lengths of the terminal bonds (Zn1—O2 = 2.2907 (17) Å) are significantly larger than the bridging Zn—O—Zn moiety (Zn1—O1 = 1.9851 (17) Å, Zn1—O1A = 2.0349 (16) Å) but still less than the Zn—O bond length (2.444 Å) reported by Ding et al., (2005). The coordinated water molecules and chloride ion are located trans with respect to the Zn₂O₂ plane. The bridging vanillin ligands are coplanar. There are two water molecules in the lattice. The O1w H atoms make intermolecular hydrogen bonds to the O2w atoms [(symmetry code: -1 + x, y, z) with d(O···O) = 2.671 (3)Å and angle O–H···O = 175.(3)°] and uncoordinated O3 atoms [(symmetry code: x - 1, y, z - 1) with d(O···O) = 2.666 (3)Å and angle O–H···O = 170.(4)°]. The O2w H atoms also make intermolecular hydrogen bonds to the Cl atoms [(symmetry code: 1/2 + x, 0.5 - y, 1/2 + z) with d(O···O) = 3.259 (3)Å and angle O–H···O = 178.(4)°]. The vanillin O atoms, the water O atoms and chloride ion contribute to the formation of a hydrogen-bonded three-dimensional network.

Related literature

For related crystal structures, see: Ding et al. (2005); Kunert et al. (2000); Olmstead et al. (1991). For common applications of these complexes, see: Rice-Evans et al. (1996); Tumer et al. (1999).

S2. Experimental

ZnCl₂(1 mmol, 136 mg), 2-methoxy-4-[(4-nitrophenylimino)methyl]phenol (2 mmol, 545 mg) were dissolved in ethanol (25 ml) solution and the mixture was stirred for 2 h at room temperature. The yellow solution was kept aside, and the orange crystal was abtained after several weeks.

S3. Refinement

The H atoms bonded to C atoms were positioned geometrically and refined using a riding model: aromatic C–H = 0.93Å and aliphatic C–H = 0.96 Å, U_iso(H) = 1.2U_eq(C) for aromatic and U_iso(H) = 1.5U_eq(C) for aliphatic. The H atoms bonded to O atoms were located in a difference Fourier maps and refined with O–H distance restraints of 0.85 (2) and U_iso(H) = 1.5U_eq(O).

Computing details

Data collection: SMART (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2002); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures

Fig. 1. The molecular structure of I, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are presented as a spheres of arbitrary radius.

Bis(µ-4-formyl-2-methoxyphenolato)bis[aquachloridozinc(II)] dihydrate

Crystal data

[Zn2(C8H7O3)2Cl2(H2O)2]	F(000) = 584
Mr = 576.02	Dx = 1.750 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 3431 reflections
a = 7.0896 (6) Å	θ = 2.5–27.5°
b = 15.9772 (10) Å	µ = 2.49 mm^−1
c = 10.1193 (7) Å	T = 296 K
β = 107.559 (4)°	Plate, orange
V = 1092.83 (14) Å^3	0.26 × 0.17 × 0.07 mm
Z = 2

Data collection

Bruker P4 diffractometer	2500 independent reflections
Radiation source: Fine-focus sealed tube	2046 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.028
ω–scans	θmax = 27.5°, θmin = 2.5°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −9→8
Tmin = 0.517, Tmax = 0.840	k = −20→20
9933 measured reflections	l = −13→12

Refinement

Refinement on F^2	Primary atom site location: Direct
Least-squares matrix: Full	Secondary atom site location: Difmap
R[F^2 > 2σ(F^2)] = 0.030	Hydrogen site location: Geom
wR(F^2) = 0.088	H atoms treated by a mixture of independent and constrained refinement
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0464P)^2 + 0.539P] where P = (Fo^2 + 2Fc^2)/3
2500 reflections	(Δ/σ)max = 0.001
148 parameters	Δρmax = 0.57 e Å^−3
6 restraints	Δρmin = −0.48 e Å^−3

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	−0.05704 (4)	0.407241 (18)	0.51776 (3)	0.03079 (12)
Cl1	0.06529 (12)	0.29032 (5)	0.45511 (8)	0.0496 (2)
C1	0.1385 (3)	0.50285 (15)	0.7681 (2)	0.0275 (5)
C2	0.2207 (4)	0.57134 (16)	0.8483 (3)	0.0330 (5)
H2A	0.2306	0.6222	0.8063	0.040*
C3	0.2887 (4)	0.56405 (17)	0.9918 (3)	0.0338 (6)
H3A	0.3432	0.6103	1.0455	0.041*
C4	0.2758 (4)	0.48843 (16)	1.0555 (2)	0.0316 (5)
C5	0.1889 (4)	0.41882 (16)	0.9764 (2)	0.0309 (5)
H5A	0.1790	0.3681	1.0188	0.037*
C6	0.1187 (4)	0.42698 (15)	0.8348 (2)	0.0289 (5)
C7	0.0128 (5)	0.28292 (17)	0.7989 (3)	0.0460 (7)
H7A	0.0587	0.2848	0.8983	0.055*
H7B	0.0934	0.2448	0.7661	0.055*
H7C	−0.1221	0.2643	0.7687	0.055*
C8	0.3641 (4)	0.48144 (19)	1.2047 (3)	0.0390 (6)
H8A	0.4148	0.5299	1.2534	0.047*
O1	0.0780 (3)	0.50395 (10)	0.63014 (17)	0.0345 (4)
O1W	−0.3382 (3)	0.39772 (14)	0.5103 (2)	0.0426 (5)
H1WA	−0.434 (4)	0.406 (2)	0.441 (3)	0.064*
H1WB	−0.377 (5)	0.3628 (19)	0.555 (3)	0.064*
O2	0.0256 (3)	0.36493 (11)	0.74433 (18)	0.0406 (5)
O2W	0.5141 (4)	0.2849 (3)	0.6469 (3)	0.1013 (13)
H2WA	0.393 (3)	0.294 (4)	0.616 (5)	0.152*
H2WB	0.525 (8)	0.265 (4)	0.725 (3)	0.152*
O3	0.3765 (3)	0.41693 (14)	1.2706 (2)	0.0489 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn1	0.03931 (19)	0.02613 (18)	0.02405 (17)	−0.00240 (12)	0.00521 (12)	0.00208 (11)
Cl1	0.0609 (5)	0.0417 (4)	0.0420 (4)	0.0132 (3)	0.0091 (3)	−0.0052 (3)
C1	0.0291 (11)	0.0315 (12)	0.0207 (11)	0.0014 (10)	0.0059 (9)	0.0043 (9)
C2	0.0396 (14)	0.0289 (12)	0.0303 (13)	−0.0015 (11)	0.0101 (11)	0.0014 (10)
C3	0.0373 (14)	0.0339 (13)	0.0276 (12)	0.0030 (11)	0.0060 (11)	−0.0051 (10)
C4	0.0304 (12)	0.0401 (14)	0.0229 (11)	0.0059 (11)	0.0062 (10)	0.0001 (10)
C5	0.0330 (13)	0.0341 (13)	0.0243 (12)	0.0017 (10)	0.0067 (10)	0.0070 (10)
C6	0.0309 (12)	0.0311 (12)	0.0219 (11)	0.0000 (10)	0.0037 (9)	0.0019 (9)
C7	0.0607 (19)	0.0308 (14)	0.0410 (15)	−0.0087 (13)	0.0069 (14)	0.0087 (12)
C8	0.0405 (15)	0.0511 (16)	0.0232 (12)	0.0051 (13)	0.0062 (11)	−0.0026 (12)
O1	0.0518 (11)	0.0286 (9)	0.0195 (8)	−0.0056 (8)	0.0053 (7)	0.0034 (7)
O1W	0.0363 (11)	0.0565 (13)	0.0303 (10)	−0.0027 (9)	0.0031 (8)	0.0117 (9)
O2	0.0574 (12)	0.0298 (9)	0.0249 (9)	−0.0113 (9)	−0.0020 (8)	0.0053 (7)
O2W	0.0647 (17)	0.154 (3)	0.0694 (18)	−0.045 (2)	−0.0035 (14)	0.058 (2)
O3	0.0529 (13)	0.0624 (14)	0.0254 (10)	0.0024 (10)	0.0027 (9)	0.0092 (9)

Geometric parameters (Å, º)

Zn1—O1W	1.978 (2)	C5—C6	1.374 (3)
Zn1—O1	1.9851 (17)	C5—H5A	0.9300
Zn1—O1^i	2.0350 (16)	C6—O2	1.375 (3)
Zn1—Cl1	2.2307 (8)	C7—O2	1.435 (3)
Zn1—O2	2.2905 (17)	C7—H7A	0.9600
Zn1—Zn1^i	3.1216 (6)	C7—H7B	0.9600
C1—O1	1.331 (3)	C7—H7C	0.9600
C1—C2	1.382 (3)	C8—O3	1.217 (3)
C1—C6	1.415 (3)	C8—H8A	0.9300
C2—C3	1.390 (4)	O1—Zn1^i	2.0350 (16)
C2—H2A	0.9300	O1W—H1WA	0.827 (17)
C3—C4	1.385 (4)	O1W—H1WB	0.819 (17)
C3—H3A	0.9300	O2W—H2WA	0.833 (19)
C4—C5	1.400 (4)	O2W—H2WB	0.83 (4)
C4—C8	1.454 (3)
O1W—Zn1—O1	112.85 (9)	C5—C4—C8	120.7 (2)
O1W—Zn1—O1^i	100.15 (8)	C6—C5—C4	118.7 (2)
O1—Zn1—O1^i	78.12 (7)	C6—C5—H5A	120.7
O1W—Zn1—Cl1	113.49 (7)	C4—C5—H5A	120.7
O1—Zn1—Cl1	130.77 (6)	C5—C6—O2	125.2 (2)
O1^i—Zn1—Cl1	108.86 (5)	C5—C6—C1	121.4 (2)
O1W—Zn1—O2	88.06 (8)	O2—C6—C1	113.4 (2)
O1—Zn1—O2	73.91 (6)	O2—C7—H7A	109.5
O1^i—Zn1—O2	151.87 (7)	O2—C7—H7B	109.5
Cl1—Zn1—O2	91.91 (6)	H7A—C7—H7B	109.5
O1W—Zn1—Zn1^i	111.21 (6)	O2—C7—H7C	109.5
O1—Zn1—Zn1^i	39.64 (5)	H7A—C7—H7C	109.5
O1^i—Zn1—Zn1^i	38.48 (5)	H7B—C7—H7C	109.5
Cl1—Zn1—Zn1^i	128.75 (3)	O3—C8—C4	124.9 (3)
O2—Zn1—Zn1^i	113.49 (5)	O3—C8—H8A	117.6
O1—C1—C2	123.4 (2)	C4—C8—H8A	117.6
O1—C1—C6	117.7 (2)	C1—O1—Zn1	122.51 (15)
C2—C1—C6	118.9 (2)	C1—O1—Zn1^i	135.20 (15)
C1—C2—C3	119.9 (2)	Zn1—O1—Zn1^i	101.88 (7)
C1—C2—H2A	120.1	Zn1—O1W—H1WA	126 (2)
C3—C2—H2A	120.1	Zn1—O1W—H1WB	122 (2)
C4—C3—C2	120.6 (2)	H1WA—O1W—H1WB	105 (2)
C4—C3—H3A	119.7	C6—O2—C7	118.4 (2)
C2—C3—H3A	119.7	C6—O2—Zn1	112.32 (14)
C3—C4—C5	120.4 (2)	C7—O2—Zn1	128.87 (16)
C3—C4—C8	118.8 (2)	H2WA—O2W—H2WB	103 (3)
O1—C1—C2—C3	−177.0 (2)	Cl1—Zn1—O1—C1	−81.56 (19)
C6—C1—C2—C3	2.2 (4)	O2—Zn1—O1—C1	−3.26 (18)
C1—C2—C3—C4	0.4 (4)	Zn1^i—Zn1—O1—C1	173.7 (2)
C2—C3—C4—C5	−1.9 (4)	O1W—Zn1—O1—Zn1^i	−96.13 (9)
C2—C3—C4—C8	174.7 (2)	O1^i—Zn1—O1—Zn1^i	0.0
C3—C4—C5—C6	0.6 (4)	Cl1—Zn1—O1—Zn1^i	104.76 (8)
C8—C4—C5—C6	−175.9 (2)	O2—Zn1—O1—Zn1^i	−176.94 (10)
C4—C5—C6—O2	−178.3 (2)	C5—C6—O2—C7	−5.1 (4)
C4—C5—C6—C1	2.1 (4)	C1—C6—O2—C7	174.5 (2)
O1—C1—C6—C5	175.7 (2)	C5—C6—O2—Zn1	−178.4 (2)
C2—C1—C6—C5	−3.6 (4)	C1—C6—O2—Zn1	1.2 (3)
O1—C1—C6—O2	−3.9 (3)	O1W—Zn1—O2—C6	−113.56 (18)
C2—C1—C6—O2	176.8 (2)	O1—Zn1—O2—C6	0.91 (16)
C3—C4—C8—O3	−173.8 (3)	O1^i—Zn1—O2—C6	−5.5 (3)
C5—C4—C8—O3	2.8 (4)	Cl1—Zn1—O2—C6	133.00 (17)
C2—C1—O1—Zn1	−175.52 (19)	Zn1^i—Zn1—O2—C6	−1.22 (18)
C6—C1—O1—Zn1	5.2 (3)	O1W—Zn1—O2—C7	74.0 (2)
C2—C1—O1—Zn1^i	−4.3 (4)	O1—Zn1—O2—C7	−171.5 (3)
C6—C1—O1—Zn1^i	176.41 (17)	O1^i—Zn1—O2—C7	−177.9 (2)
O1W—Zn1—O1—C1	77.54 (19)	Cl1—Zn1—O2—C7	−39.4 (2)
O1^i—Zn1—O1—C1	173.7 (2)	Zn1^i—Zn1—O2—C7	−173.6 (2)

Symmetry code: (i) −x, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1W—H1WA···O3^ii	0.83 (2)	1.85 (2)	2.666 (3)	171 (4)
O1W—H1WB···O2W^iii	0.82 (2)	1.85 (2)	2.671 (3)	175 (3)
O2W—H2WA···Cl1	0.83 (2)	2.40 (3)	3.190 (3)	158 (6)
O2W—H2WB···Cl1^iv	0.83 (4)	2.43 (4)	3.258 (3)	178 (6)

Symmetry codes: (ii) x−1, y, z−1; (iii) x−1, y, z; (iv) x+1/2, −y+1/2, z+1/2.