Diaqua­bis­{2-hy­droxy-5-[(pyridin-2-yl)methyl­idene­amino]­benzoato-κ²N,N′}zinc(II) dihydrate

The complex mol­ecule of the title compound, [Zn(C₁₃H₉N₂O₃)₂(H₂O)₂]·2H₂O, has 2 symmetry with the Zn^II cation located on a twofold rotation axis. The Zn cation is N,N′-chelated by two 5-[(pyridin-2-yl)methyl­idene­amino]-2-hy­droxy­benzoate anions and coordinated by two water mol­ecules in a distorted octa­hedral geometry. Within the anionic ligand, the pyridine ring is oriented at a dihedral angle of 49.54 (10)° with respect to the benzene ring. The carboxyl­ate group of the anionic ligand is not involved in coordination but is O—H...O hydrogen bonded to the coordinated and uncoordinated water mol­ecules. Weak inter­molecular C—H...O hydrogen bonding is also present in 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 = 0.083
• Data-to-parameter ratio = 14.8

checkCIF/PLATON results

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Alert level G
PLAT794_ALERT_5_G Note: Tentative Bond Valency for Zn1     .......       1.88

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

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

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S1. Comment

The current interest in design and synthesis of new Schiff bases and their metal complexes stem from their potential applications in antimicrobial (Bourque et al., 2005), magnetic (Feng et al., 2007; Gang et al., 2007), anticancer (Shanta et al., 2003) and catalytic (Donald et al., 2010). Hereby design and synthesis of new Schiff bases is a important field in coordination chemistry. 5-aminosalicylic acid is widely used in medicine and dye chemistry. 2-pyridinecarboxaldehyde is the intermeadiate of the bisacodyl, which is a popular medicine. We synthesized a new Schiff base 5-((pyridin-2-yl)methyleneamino)-2-hydroxybenzoic acid (C₁₃H₉N₂O₃) from 5-aminosalicylic acid and 2-pyridinecarboxaldehyde by nucleophilic addition, followed by a dehydration. The Schiff base can coordinate to the metal atoms through N or O donor atoms. Herein we report the preparation and characterization of the first 5-((pyridin-2-yl)methyleneamino)-2-hydroxybenzoic-zinc(II) complex, [Zn(C₁₃H₉N₂O₃)₂(H₂O)₂].2H₂O.

Single-crystal X-ray diffraction analysis indicates the title complex possesses a mononuclear structure and crystallizes in the orthorhombic, space group Pbcn with Z = 4. The asymmetric unit consists of two Schiff base ligand, one zinc ion, two coordinated water and two guest water molecule. A view of the zinc ion coordination is shown in Figure 1, where the metal center is coordinated in an octahedral geometry by four N atoms of the Schiff base ligand with Zn—N distances ranging from 2.1416 (17) to 2.2742 (14) Å and two O atoms from water molecules with Zn—O distances ranging from 2.0491 (15) Å. The intromolecular interaction is helpful to the stabilization of the crystal structure (Figure 2).

Related literature

The title compound is a Schiff base complex; for potential applications of Schiff base compounds, see: Bourque et al. (2005); Donald & Osit (2010); Feng et al. (2007); Gang et al. (2007); Shanta et al. (2003).

S2. Experimental

5-Aminosalicylic acid (1.53 g, 10 mmol), 2-pyridinecarboxaldehyde (1 ml, 10 mmol) and triethylamine (1 ml, 10 mmol) were added to 50 ml e thanol in a round flask, and this mixture was refluxed with agitation for 4 h at 323 K to give an yellow precipitate. After filtration and washing the precipitate with ethanol to give the pure Schiff base 5-((pyridin-2-yl)methyleneamino)-2-hydroxybenzoic acid (2.02 g, 84.00%).

Mixture of 5-((pyridin-2-yl)methyleneamino)-2-hydroxybenzoic acid (0.1 mmol, 0.024 g), Zn(OAc)₂.2H₂O (0.1 mmol, 0.022 g) and methanol (20 ml) to give an yellow solution. After evaporating the solution for one week, yellow crystals were obtained (yield, 50%).

S3. Refinement

H atoms attached to C atoms were placed in calculated positions and treated using a riding-model approximation with C–H = 0.93 Å and U_iso(H) = 1.2U_eq(C). H atoms bonded to O atoms were located in a difference Fourier map and refined isotropically.

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. A view of the zinc ion coordination, showing the labeling of the non-H atoms and 30% probability ellipsoids. H atoms have been omitted for clarity.
	Fig. 2. Packing of title complex showing the three dimensional hydrogen bonding network.

Diaquabis{2-hydroxy-5-[(pyridin-2-yl)methylideneamino]benzoato- κ²N,N'}zinc(II) dihydrate

Crystal data

[Zn(C13H9N2O3)2(H2O)2]·2H2O	F(000) = 1280
Mr = 619.90	Dx = 1.557 Mg m^−3
Orthorhombic, Pbcn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2n 2ab	Cell parameters from 5445 reflections
a = 15.812 (2) Å	θ = 2.3–26.5°
b = 10.6962 (15) Å	µ = 1.00 mm^−1
c = 15.636 (2) Å	T = 296 K
V = 2644.5 (6) Å^3	Block, yellow
Z = 4	0.43 × 0.32 × 0.27 mm

Data collection

Bruker SMART APEX CCD area-detector diffractometer	3041 independent reflections
Radiation source: fine-focus sealed tube	2291 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.038
φ and ω scans	θmax = 27.5°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Bruker, 2001)	h = −20→20
Tmin = 0.689, Tmax = 0.764	k = −13→13
21797 measured reflections	l = −20→20

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.030	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.083	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	w = 1/[σ^2(Fo^2) + (0.0389P)^2 + 0.7619P] where P = (Fo^2 + 2Fc^2)/3
3041 reflections	(Δ/σ)max < 0.001
206 parameters	Δρmax = 0.33 e Å^−3
0 restraints	Δρmin = −0.29 e Å^−3

Special details

Experimental. IR (KBr, cm-1): 3455(versus), 3088(w), 2924(w), 2361(w), 1919(w), 1668(s), 1602(m), 1578(m), 1489(versus), 1447(m), 1364(versus), 1299(m), 1245(s), 1161(m), 1084(m), 1054(s), 959(w), 893(m), 839(s), 792(versus), 655(m), 572(m), 512(m).

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 (Ų)

	x	y	z	Uiso*/Ueq
Zn1	0.5000	0.40959 (2)	0.2500	0.03779 (10)
O1	0.49550 (12)	0.53276 (14)	0.14990 (11)	0.0590 (4)
O2	0.70387 (10)	−0.06373 (16)	−0.00402 (11)	0.0623 (4)
O3	0.62843 (10)	−0.24718 (13)	0.05467 (11)	0.0670 (4)
O4	0.51579 (10)	−0.22474 (13)	0.13984 (11)	0.0615 (4)
O5	0.37521 (14)	0.47962 (17)	0.02876 (13)	0.0709 (5)
N1	0.36496 (10)	0.39448 (14)	0.24957 (9)	0.0414 (4)
N2	0.47286 (10)	0.24704 (13)	0.16032 (9)	0.0364 (3)
C1	0.31145 (14)	0.4780 (2)	0.28233 (14)	0.0525 (5)
H1A	0.3329	0.5440	0.3144	0.063*
C2	0.22455 (15)	0.4697 (2)	0.27010 (15)	0.0625 (6)
H2A	0.1889	0.5311	0.2919	0.075*
C3	0.19182 (15)	0.3703 (2)	0.22564 (16)	0.0643 (6)
H3A	0.1337	0.3615	0.2190	0.077*
C4	0.24669 (13)	0.2838 (2)	0.19101 (14)	0.0537 (5)
H4A	0.2262	0.2158	0.1603	0.064*
C5	0.33299 (12)	0.30015 (17)	0.20284 (12)	0.0416 (4)
C6	0.39452 (12)	0.21815 (16)	0.16127 (12)	0.0415 (4)
H6A	0.3765	0.1445	0.1354	0.050*
C7	0.53077 (12)	0.16496 (16)	0.11906 (11)	0.0363 (4)
C8	0.59723 (12)	0.21657 (17)	0.07233 (12)	0.0458 (4)
H8A	0.6034	0.3029	0.0695	0.055*
C9	0.65391 (13)	0.14022 (19)	0.03025 (13)	0.0507 (5)
H9A	0.6977	0.1753	−0.0014	0.061*
C10	0.64583 (12)	0.01035 (18)	0.03502 (13)	0.0444 (4)
C11	0.57989 (11)	−0.04244 (16)	0.08294 (12)	0.0386 (4)
C12	0.52303 (11)	0.03585 (16)	0.12417 (11)	0.0374 (4)
H12A	0.4790	0.0013	0.1558	0.045*
C13	0.57306 (13)	−0.18215 (17)	0.09375 (13)	0.0470 (5)
H1	0.5058 (16)	0.606 (3)	0.152 (2)	0.081 (10)*
H2	0.4595 (18)	0.517 (3)	0.1115 (18)	0.083 (9)*
H3	0.3812 (19)	0.417 (3)	−0.005 (2)	0.084 (9)*
H4	0.326 (2)	0.507 (3)	0.025 (2)	0.124 (14)*
H5	0.685 (2)	−0.146 (3)	0.009 (2)	0.117 (11)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn1	0.04294 (17)	0.02329 (15)	0.04715 (18)	0.000	−0.00043 (13)	0.000
O1	0.0828 (11)	0.0317 (8)	0.0625 (9)	−0.0157 (8)	−0.0203 (9)	0.0127 (7)
O2	0.0562 (9)	0.0523 (9)	0.0785 (11)	−0.0026 (7)	0.0186 (8)	−0.0231 (8)
O3	0.0642 (9)	0.0356 (8)	0.1011 (12)	0.0057 (7)	0.0064 (9)	−0.0178 (8)
O4	0.0744 (11)	0.0280 (7)	0.0820 (11)	−0.0052 (7)	0.0102 (8)	0.0028 (7)
O5	0.0746 (12)	0.0529 (10)	0.0851 (12)	0.0051 (9)	−0.0225 (10)	−0.0171 (9)
N1	0.0442 (8)	0.0357 (8)	0.0443 (8)	0.0064 (6)	0.0028 (7)	0.0041 (7)
N2	0.0446 (8)	0.0241 (7)	0.0406 (8)	0.0009 (6)	0.0000 (6)	0.0006 (6)
C1	0.0608 (13)	0.0453 (12)	0.0514 (11)	0.0133 (10)	0.0115 (10)	0.0046 (9)
C2	0.0562 (13)	0.0630 (15)	0.0684 (15)	0.0221 (11)	0.0210 (11)	0.0172 (12)
C3	0.0452 (12)	0.0712 (16)	0.0764 (15)	0.0103 (11)	0.0067 (11)	0.0232 (13)
C4	0.0462 (11)	0.0533 (12)	0.0616 (13)	−0.0023 (9)	−0.0050 (10)	0.0108 (10)
C5	0.0427 (10)	0.0356 (9)	0.0466 (10)	0.0005 (8)	−0.0012 (8)	0.0081 (8)
C6	0.0466 (11)	0.0302 (9)	0.0477 (10)	−0.0031 (8)	−0.0059 (8)	−0.0008 (8)
C7	0.0402 (9)	0.0283 (9)	0.0404 (9)	−0.0013 (7)	−0.0009 (8)	−0.0014 (7)
C8	0.0593 (12)	0.0284 (9)	0.0497 (10)	−0.0078 (8)	0.0067 (9)	−0.0001 (8)
C9	0.0572 (12)	0.0423 (11)	0.0525 (11)	−0.0125 (9)	0.0166 (10)	−0.0025 (9)
C10	0.0457 (10)	0.0416 (10)	0.0459 (10)	−0.0015 (8)	0.0015 (9)	−0.0118 (8)
C11	0.0429 (10)	0.0285 (8)	0.0443 (10)	−0.0031 (7)	−0.0054 (8)	−0.0039 (7)
C12	0.0394 (9)	0.0290 (9)	0.0438 (10)	−0.0047 (7)	−0.0017 (7)	0.0000 (7)
C13	0.0533 (12)	0.0284 (9)	0.0593 (12)	0.0014 (8)	−0.0092 (10)	−0.0067 (9)

Geometric parameters (Å, º)

Zn1—O1^i	2.0471 (15)	C1—H1A	0.9300
Zn1—O1	2.0471 (15)	C2—C3	1.372 (4)
Zn1—N1^i	2.1414 (17)	C2—H2A	0.9300
Zn1—N1	2.1414 (17)	C3—C4	1.379 (3)
Zn1—N2	2.2746 (14)	C3—H3A	0.9300
Zn1—N2^i	2.2746 (14)	C4—C5	1.388 (3)
O1—H1	0.81 (3)	C4—H4A	0.9300
O1—H2	0.84 (3)	C5—C6	1.462 (3)
O2—C10	1.357 (2)	C6—H6A	0.9300
O2—H5	0.95 (3)	C7—C12	1.389 (2)
O3—C13	1.274 (2)	C7—C8	1.394 (3)
O4—C13	1.244 (2)	C8—C9	1.380 (3)
O5—H3	0.86 (3)	C8—H8A	0.9300
O5—H4	0.84 (4)	C9—C10	1.397 (3)
N1—C1	1.333 (2)	C9—H9A	0.9300
N1—C5	1.344 (2)	C10—C11	1.403 (3)
N2—C6	1.277 (2)	C11—C12	1.388 (2)
N2—C7	1.423 (2)	C11—C13	1.508 (2)
C1—C2	1.390 (3)	C12—H12A	0.9300
O1^i—Zn1—O1	99.88 (10)	C2—C3—H3A	120.6
O1^i—Zn1—N1^i	90.66 (6)	C4—C3—H3A	120.6
O1—Zn1—N1^i	94.92 (7)	C3—C4—C5	118.8 (2)
O1^i—Zn1—N1	94.92 (7)	C3—C4—H4A	120.6
O1—Zn1—N1	90.66 (6)	C5—C4—H4A	120.6
N1^i—Zn1—N1	171.34 (8)	N1—C5—C4	122.45 (18)
O1^i—Zn1—N2	165.91 (6)	N1—C5—C6	116.20 (16)
O1—Zn1—N2	90.80 (6)	C4—C5—C6	121.29 (18)
N1^i—Zn1—N2	97.61 (5)	N2—C6—C5	120.37 (16)
N1—Zn1—N2	75.65 (6)	N2—C6—H6A	119.8
O1^i—Zn1—N2^i	90.80 (6)	C5—C6—H6A	119.8
O1—Zn1—N2^i	165.91 (6)	C12—C7—C8	119.37 (17)
N1^i—Zn1—N2^i	75.65 (6)	C12—C7—N2	122.05 (16)
N1—Zn1—N2^i	97.61 (5)	C8—C7—N2	118.58 (15)
N2—Zn1—N2^i	80.29 (7)	C9—C8—C7	120.36 (17)
Zn1—O1—H1	126 (2)	C9—C8—H8A	119.8
Zn1—O1—H2	115.9 (19)	C7—C8—H8A	119.8
H1—O1—H2	111 (3)	C8—C9—C10	120.25 (17)
C10—O2—H5	103 (2)	C8—C9—H9A	119.9
H3—O5—H4	109 (3)	C10—C9—H9A	119.9
C1—N1—C5	118.25 (18)	O2—C10—C9	119.64 (18)
C1—N1—Zn1	125.53 (15)	O2—C10—C11	120.52 (18)
C5—N1—Zn1	115.68 (12)	C9—C10—C11	119.79 (17)
C6—N2—C7	118.70 (15)	C12—C11—C10	119.14 (16)
C6—N2—Zn1	111.15 (12)	C12—C11—C13	119.98 (17)
C7—N2—Zn1	129.02 (12)	C10—C11—C13	120.80 (17)
N1—C1—C2	122.1 (2)	C11—C12—C7	121.09 (17)
N1—C1—H1A	118.9	C11—C12—H12A	119.5
C2—C1—H1A	118.9	C7—C12—H12A	119.5
C3—C2—C1	119.5 (2)	O4—C13—O3	125.32 (18)
C3—C2—H2A	120.3	O4—C13—C11	118.69 (17)
C1—C2—H2A	120.3	O3—C13—C11	115.98 (18)
C2—C3—C4	118.8 (2)

Symmetry code: (i) −x+1, y, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O4^ii	0.80 (3)	1.83 (3)	2.618 (2)	169 (3)
O1—H2···O5	0.84 (3)	1.90 (3)	2.744 (3)	178 (3)
O5—H3···O3^iii	0.86 (3)	1.98 (3)	2.808 (2)	161 (3)
O5—H4···O2^iv	0.83 (3)	2.05 (3)	2.881 (3)	174 (3)
O2—H5···O3	0.95 (3)	1.58 (3)	2.473 (2)	156 (3)
C6—H6A···O2^iii	0.93	2.57	3.346 (3)	142

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