The one-dimensional chain polymer of aqua­(tyrosinato)zinc(II)

In the title compound, catena-poly[[aqua­zinc(II)]-[mu]₃-tyrosin­ato], [Zn(C₉H₇NO₃)(H₂O)]_n, each Zn atom has a distorted square-pyramidal geometry comprised of three O atoms and one N atom from three tyrosinate (tyr) ligands, and one aqua ligand. Two inversion-related Zn²⁺ ions are bridged by two O atoms from the phenolate groups of two tyr ligands to form a centrosymmetric dimeric unit, which can be described as a planar Zn₂O₂ four-membered ring. These repeating dimeric units are arranged along the c axis to give a one-dimensional chain coordination polymer, in which the tyr ligand adopts an unusual chelating/bridging coordination mode.

S1. Comment

The rational design and assembly of metal–organic coordination frameworks have received much attention in recent years, owing to their intriguing structural topologies and potential or practical applications in the areas of catalysis, magnetism, gas storage, nonlinear optics, electronics and others (Bernhard et al., 2003; Lin et al., 1998; Sun et al., 2005; Zhu et al., 2005; Wu et al., 2007). A number of fascinating metal–organic coordination polymers are known to be constructed by the combination of symmetrical or asymmetrical bridging ligands as the 'spacer', and metal ions or a metal cluster as the 'node'. Carboxylate-containing ligands acting as the 'spacer' have attracted much attention because of the diversity of the binding modes of the carboxylate group (Zhu et al., 2005; Shi et al., 2005). The tyr ligand, with a carboxylate group, and its derivatives are good spacers because they often behave similarly to isonicotinic acid, acting as a chelating/bridging ligand via the N and O atoms. Diverse topologies can be achieved with the tyr ligand (Ayyappan et al., 2001; Lu & Babb, 2001; Lu et al., 2003). However, the reported complexes of the tyr ligand are generally mononuclear (Emseis et al., 2004; Harrowfield et al., 1983; Majumder et al., 2002), with only two coordination polymers being described in the literature, namely [Cu(H-tyr)₂]_n and {[Cu₂(H-tyr)₂(4,4-bipy). 2H₂O].2 ClO₄}_n (Weng et al., 2002). Interestingly, the phenolate O atom in these two complexes is uncoordinated. In order to learn more about the coordination mode of the tyrosinato ligand, we have chosen the zinc(II) salts as the node. The zinc coordination polymers exhibit rich structural diversity because of the variable coordination behaviours of the d¹⁰ metal ion Zn^II. We have successfully obtained the 1-D zinc(II) polymer [Zn(C₉H₇NO₃)(H₂O)]_n, (I), containing the unusual coordinating phenolate O atom, via synthesis under solvothermal conditions.

The crystal structure of (I) consists of neutral [Zn(C₉H₇NO₃) (H₂O)] 1-D chains (see Fig. 1). Two Zn²⁺ ions are linked by two O atoms of the phenolate groups to give rise to a dimeric unit, which displays an inversion centre sited in the middle of the Zn₂O₂ cores. The Zn1—Zn1ⁱⁱ [symmetry code: (ii) -x, -y, -z + 2] intramolecular separation is 3.1981 (9) Å. Each zinc(II) centre in the dimeric unit is coordinated to three O atoms and one N atom from three tyr ligands, and one aqua ligand in a distorted square-pyramidal coordination geometry. These dimeric units are connected by tyr ligands to form a 1-D chain coordination polymer propagating along the crystallographic c axis. The Zn—O bonds, varying from 2.006 (3) to 2.075 (3) Å, are in good agreement with the corresponding bond lengths in [Zn₂(Rsala)₂ (H₂O)₂]·2H₂O (Vittal & Yang, 2002), [Zn(BTZ)₂]₂ (Yu et al., 2003), Zn₂(H₂SB)₂·3H₂O·Me₂CO (Matalobos et al., 2004) and [Zn₂C₂₂H₂₀N₄O₂(H₂O)₂] (ClO₄)₂ (Huang et al., 2001). The Zn1—N1ⁱ [symmetry code: (i) -x + 1, -y, -z + 1] bond length is 2.154 (4) Å, comparable with those reported for [M(en)₃]₂Sn₂S₆ [2.14 (3)–2.23 (1) Å; Jia et al., 2004] and [Zn(en)₃]₄In₁₆(Te₂)₄(Te₃)Te₂₂ [2.12 (3)–2.32 (3) Å; Chen et al., 2001]. The hydrogen bonds between the O atoms of the carboxylate groups and the H atoms of the water molecules [O1W—H···O3^iv, symmetry code: (iv) x - 1, y - 1, z + 1] link the adjacent chains to form a 2-D sheet within the (100) plane (Fig. 2); the chains further interact via the formation of N1—H···O3ⁱⁱⁱ and O1W—H···O2^v [symmetry code: (iii) x - 1, y, z; (v) -x + 2, -y, -z + 1] hydrogen bonds, resulting in a three-dimensional H-bonding network structure.

The possible coordination modes of tyr^2- and H-tyr^- are shown in the scheme below. The usual chelating mode is (b), as exemplified by [Co(en)(2-N-eth-en) (H-tyr)]·2ClO₄·2H₂O (Harrowfield et al., 1983), [Cu(hista)(H-tyr) (ClO₄)] (Yamauchi et al., 1989), [Ru(bpy)₂ (H-tyr)]ClO₄ (Majumder et al., 2002), [Cu(H-tyr)(phen)ClO₄]·2.5H₂O (Sugimori et al., 1997) and [Co(picchxn)(H-tyr)] Br₂·3.5H₂O (Emseis et al., 2004). The bridging mode (c) is less common, with only two examples found, [Cu(H-tyr)₂]_n and {[Cu₂(H-tyr)₂(4,4-bipy). 2H₂O].2 ClO₄}_n (Weng et al., 2002). The most remarkable feature of (I) is the unusual coordination mode (a) of the tyr^2- ligand. The tyr ligand adopts a chelating/bridging coordination mode, in which its amino and carboxylate bind a Zn²⁺ ion to form a chelating five-membered ring. In addition, the phenolate –OH bridges another two Zn²⁺ ions, resulting in the formation of a planar Zn₂O₂ four-membered ring which contributes to the distortion of the square-pyramidal geometry around the metal ion.

Related literature

For related literature, see: Ayyappan et al. (2001); Bernhard et al. (2003); Chen et al. (2001); Emseis et al. (2004); Harrowfield et al. (1983); Huang et al. (2001); Jia et al. (2004); Lin et al. (1998); Lu & Babb (2001); Lu et al. (2003); Majumder et al. (2002); Shi et al. (2005); Sugimori et al. (1997); Sun et al. (2005); Weng et al. (2002); Wu et al. (2007); Yamauchi et al. (1989); Yu et al. (2003); Zhu et al. (2005).

S2. Experimental

Single crystals of the title complex suitable for X-ray crystallographic analysis were obtained by solvothermal treatment of Zn(NO₃)₂·6H₂O (0.2 mmol), H₂-tyr (0.1 mmol), CH₃OH (5 ml) and NH₃ (0.2 ml). The reagents were placed in a thick Pyrex tube (ca 20 cm long). The tube was cooled with liquid N₂ and the air evacuated. The sealed tube was heated at 413 k for 10 d to yield yellow block crystals in about 25% yield.

S3. Refinement

H atoms on C and N atoms were positioned geometrically and were allowed to ride on their parent atoms, with C—H = 0.93 Å and N—H = 0.90 Å, and U_iso(H) = 1.2U_eq(C) or 1.2U_eq(N). H atoms on O atoms were located in a difference map and refined. High displacement parameters suggest some disorder in the C8 atom of the tyr^2- ligand, but this could not be resolved.

Computing details

Data collection: CrystalClear (Molecular Structure Corporation & Rigaku, 2001); cell refinement: CrystalClear; data reduction: CrystalStructure (Rigaku/MSC, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The coordination environment of the Zn^II ion. The ellipsoids are shown at 30% probability; all H atoms are omitted for clarity. [Symmetry code: (i) -x + 1, -y, -z + 1; (ii) -x,-y,-z + 2.]
	Fig. 2. Part of the crystal structure of (I), showing the formation of a (100) sheet constructed from O—H···O hydrogen bonds. H atoms bonded to C atoms have been omitted for clarity.

catena-poly[[aquazinc(II)]-µ₃-tyrosinato]

Crystal data

[Zn(C9H7NO3)(H2O)]	V = 484.81 (17) Å^3
Mr = 260.54	Z = 2
Triclinic, P1	F(000) = 264
Hall symbol: -P 1	Dx = 1.785 Mg m^−3
a = 5.8633 (12) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.681 (2) Å	θ = 2.3–26.0°
c = 9.772 (2) Å	µ = 2.52 mm^−1
α = 65.336 (3)°	T = 273 K
β = 75.334 (3)°	Block, yellow
γ = 78.440 (3)°	0.14 × 0.10 × 0.06 mm

Data collection

Rigaku Mercury diffractometer	1841 independent reflections
Radiation source: fine-focus sealed tube	1645 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.020
Detector resolution: 7.31 pixels mm^-1	θmax = 26.0°, θmin = 2.3°
ω scans	h = −7→7
Absorption correction: multi-scan (Jacobson, 1998)	k = −11→11
Tmin = 0.719, Tmax = 0.863	l = −12→12
3474 measured reflections

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)] = 0.044	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.109	H atoms treated by a mixture of independent and constrained refinement
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0592P)^2 + 0.676P] where P = (Fo^2 + 2Fc^2)/3
1841 reflections	(Δ/σ)max = 0.070
144 parameters	Δρmax = 0.61 e Å^−3
2 restraints	Δρmin = −0.51 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 > 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
N1	0.7359 (7)	0.2206 (5)	0.2087 (5)	0.0400 (9)
H1B	0.6048	0.2862	0.1883	0.048*
H1A	0.6922	0.1362	0.2908	0.048*
Zn1	0.10104 (8)	−0.16052 (5)	0.98560 (5)	0.02613 (18)
O1	0.1409 (5)	0.0629 (3)	0.8754 (3)	0.0317 (7)
O1W	0.3249 (7)	−0.3060 (5)	1.1269 (5)	0.0491 (9)
H1W2	0.469 (6)	−0.292 (10)	1.088 (9)	0.12 (3)*
H1W1	0.296 (13)	−0.399 (3)	1.158 (8)	0.09 (2)*
O2	1.1516 (5)	0.2756 (4)	0.0164 (4)	0.0344 (7)
O3	1.2600 (6)	0.3971 (4)	0.1327 (4)	0.0464 (9)
C1	0.3115 (7)	0.1270 (5)	0.7566 (5)	0.0274 (9)
C2	0.2607 (8)	0.2616 (5)	0.6356 (5)	0.0383 (10)
H2	0.1059	0.3087	0.6380	0.046*
C3	0.4338 (10)	0.3268 (6)	0.5120 (5)	0.0457 (12)
H3	0.3926	0.4169	0.4328	0.055*
C4	0.6654 (9)	0.2635 (6)	0.5017 (5)	0.0436 (12)
C5	0.7176 (8)	0.1297 (6)	0.6229 (6)	0.0447 (12)
H5	0.8733	0.0840	0.6201	0.054*
C6	0.5454 (8)	0.0622 (5)	0.7478 (6)	0.0374 (10)
H6	0.5870	−0.0279	0.8269	0.045*
C7	0.8563 (12)	0.3332 (9)	0.3650 (7)	0.075 (2)
H7	0.9452	0.4037	0.3631	0.091*
C8	0.8947 (11)	0.2886 (10)	0.2421 (8)	0.089 (3)
C9	1.1178 (7)	0.3254 (5)	0.1217 (5)	0.0310 (9)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.030 (2)	0.056 (3)	0.043 (2)	−0.0176 (18)	0.0080 (17)	−0.030 (2)
Zn1	0.0231 (3)	0.0286 (3)	0.0269 (3)	−0.00491 (18)	0.00178 (19)	−0.0137 (2)
O1	0.0320 (16)	0.0268 (15)	0.0299 (16)	−0.0078 (12)	0.0120 (13)	−0.0130 (13)
O1W	0.038 (2)	0.050 (2)	0.055 (2)	−0.0049 (17)	−0.0040 (18)	−0.0190 (19)
O2	0.0234 (14)	0.0477 (18)	0.0370 (17)	−0.0099 (13)	0.0062 (13)	−0.0253 (15)
O3	0.0335 (18)	0.063 (2)	0.056 (2)	−0.0206 (16)	0.0110 (16)	−0.0400 (19)
C1	0.026 (2)	0.030 (2)	0.029 (2)	−0.0093 (17)	0.0047 (17)	−0.0162 (18)
C2	0.035 (2)	0.041 (3)	0.034 (2)	−0.006 (2)	−0.002 (2)	−0.011 (2)
C3	0.054 (3)	0.051 (3)	0.025 (2)	−0.023 (2)	−0.001 (2)	−0.003 (2)
C4	0.047 (3)	0.066 (3)	0.028 (2)	−0.032 (3)	0.010 (2)	−0.026 (2)
C5	0.025 (2)	0.063 (3)	0.054 (3)	−0.012 (2)	0.009 (2)	−0.036 (3)
C6	0.034 (2)	0.035 (2)	0.037 (3)	−0.0042 (19)	0.000 (2)	−0.013 (2)
C7	0.083 (4)	0.123 (6)	0.047 (3)	−0.080 (4)	0.042 (3)	−0.058 (4)
C8	0.059 (4)	0.185 (8)	0.072 (4)	−0.087 (5)	0.047 (3)	−0.100 (5)
C9	0.025 (2)	0.036 (2)	0.034 (2)	−0.0082 (18)	0.0033 (18)	−0.018 (2)

Geometric parameters (Å, º)

N1—C8	1.409 (6)	O3—C9	1.236 (5)
N1—Zn1^i	2.154 (4)	C1—C2	1.386 (6)
N1—H1B	0.9000	C1—C6	1.387 (6)
N1—H1A	0.9000	C2—C3	1.374 (7)
Zn1—O1	2.006 (3)	C2—H2	0.9300
Zn1—O2^i	2.032 (3)	C3—C4	1.370 (8)
Zn1—O1W	2.041 (4)	C3—H3	0.9300
Zn1—O1^ii	2.075 (3)	C4—C5	1.385 (8)
Zn1—N1^i	2.154 (4)	C4—C7	1.512 (7)
O1—C1	1.339 (5)	C5—C6	1.383 (7)
O1—Zn1^ii	2.075 (3)	C5—H5	0.9300
O1W—H1W2	0.85 (5)	C6—H6	0.9300
O1W—H1W1	0.86 (5)	C7—C8	1.392 (7)
O2—C9	1.267 (5)	C7—H7	0.9300
O2—Zn1^i	2.032 (3)	C8—C9	1.510 (6)
C8—N1—Zn1^i	110.5 (3)	C2—C1—C6	116.9 (4)
C8—N1—H1B	109.5	C3—C2—C1	121.5 (5)
Zn1^i—N1—H1B	109.5	C3—C2—H2	119.2
C8—N1—H1A	109.5	C1—C2—H2	119.2
Zn1^i—N1—H1A	109.5	C4—C3—C2	122.1 (5)
H1B—N1—H1A	108.1	C4—C3—H3	119.0
O1—Zn1—O2^i	128.61 (13)	C2—C3—H3	119.0
O1—Zn1—O1W	121.18 (15)	C3—C4—C5	116.7 (4)
O2^i—Zn1—O1W	110.19 (15)	C3—C4—C7	122.4 (6)
O1—Zn1—O1^ii	76.84 (12)	C5—C4—C7	120.9 (5)
O2^i—Zn1—O1^ii	91.12 (12)	C6—C5—C4	122.0 (5)
O1W—Zn1—O1^ii	103.19 (14)	C6—C5—H5	119.0
O1—Zn1—N1^i	95.71 (14)	C4—C5—H5	119.0
O2^i—Zn1—N1^i	79.16 (13)	C5—C6—C1	120.8 (5)
O1W—Zn1—N1^i	96.35 (16)	C5—C6—H6	119.6
O1^ii—Zn1—N1^i	160.22 (15)	C1—C6—H6	119.6
C1—O1—Zn1	127.1 (2)	C8—C7—C4	117.9 (5)
C1—O1—Zn1^ii	128.8 (2)	C8—C7—H7	121.1
Zn1—O1—Zn1^ii	103.16 (12)	C4—C7—H7	121.1
Zn1—O1W—H1W2	113 (6)	C7—C8—N1	126.7 (5)
Zn1—O1W—H1W1	111 (5)	C7—C8—C9	119.2 (4)
H1W2—O1W—H1W1	114 (7)	N1—C8—C9	114.0 (4)
C9—O2—Zn1^i	118.6 (3)	O3—C9—O2	123.6 (4)
O1—C1—C2	121.1 (4)	O3—C9—C8	119.4 (4)
O1—C1—C6	122.0 (4)	O2—C9—C8	117.0 (4)
O2^i—Zn1—O1—C1	−109.6 (3)	C3—C4—C5—C6	0.5 (7)
O1W—Zn1—O1—C1	72.1 (4)	C7—C4—C5—C6	−178.8 (4)
O1^ii—Zn1—O1—C1	169.7 (4)	C4—C5—C6—C1	−0.2 (7)
N1^i—Zn1—O1—C1	−28.9 (3)	O1—C1—C6—C5	179.2 (4)
O2^i—Zn1—O1—Zn1^ii	80.73 (17)	C2—C1—C6—C5	−0.3 (7)
O1W—Zn1—O1—Zn1^ii	−97.61 (17)	C3—C4—C7—C8	−89.0 (9)
O1^ii—Zn1—O1—Zn1^ii	0.0	C5—C4—C7—C8	90.3 (8)
N1^i—Zn1—O1—Zn1^ii	161.41 (15)	C4—C7—C8—N1	19.8 (14)
Zn1—O1—C1—C2	139.5 (4)	C4—C7—C8—C9	−165.6 (7)
Zn1^ii—O1—C1—C2	−53.4 (5)	Zn1^i—N1—C8—C7	−175.7 (8)
Zn1—O1—C1—C6	−39.9 (5)	Zn1^i—N1—C8—C9	9.4 (8)
Zn1^ii—O1—C1—C6	127.2 (4)	Zn1^i—O2—C9—O3	−179.8 (4)
O1—C1—C2—C3	−178.9 (4)	Zn1^i—O2—C9—C8	2.6 (6)
C6—C1—C2—C3	0.5 (7)	C7—C8—C9—O3	−1.4 (11)
C1—C2—C3—C4	−0.3 (8)	N1—C8—C9—O3	173.8 (6)
C2—C3—C4—C5	−0.2 (7)	C7—C8—C9—O2	176.3 (7)
C2—C3—C4—C7	179.0 (5)	N1—C8—C9—O2	−8.4 (9)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1B···O3^iii	0.90	2.18	3.056 (6)	165
O1W—H1W1···O3^iv	0.86 (5)	2.15 (5)	2.950 (6)	156 (6)
O1W—H1W2···O2^v	0.85 (5)	2.21 (5)	3.051 (6)	175 (9)

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