Diaqua­{2,6-bis­[N-(2-pyridinylmeth­yl)­carbamo­yl]­phenolato-κ2 O 1,O 2}zinc(II)

Chomchai Suksai; Sarayut Watchasit; Thawatchai Tuntulani; Chaveng Pakawatchai

doi:10.1107/S1600536808016693

. 2008 Jun 7;64(Pt 7):m884–m885. doi: 10.1107/S1600536808016693

Diaqua{2,6-bis[N-(2-pyridinylmethyl)carbamoyl]phenolato-κ² O ¹,O ²}zinc(II)

Chomchai Suksai ^a,^*, Sarayut Watchasit ^a, Thawatchai Tuntulani ^b, Chaveng Pakawatchai ^c

PMCID: PMC2961791 PMID: 21202754

Abstract

In the title compound, [Zn(C₂₀H₁₇N₄O₃)₂(H₂O)₂], the Zn^II atom, lying on a twofold rotation axis, is six-coordinated in a distorted octahedral geometry by two phenolate O atoms and two carbonyl O atoms from two 2,6-bis[(pyridin-2-ylmethyl)carbamoyl]phenolate ligands and by two water molecules. A three-dimensional network is built up from an extensive array of hydrogen bonds and π–π interactions between the pyridyl rings, with a centroid–centroid distance of 3.666 (3) Å.

Related literature

For related literature, see: Chaudhuri et al. (2007 ▶); Goldsmith et al. (2002 ▶); Gumbley & Stewart (1984 ▶); Ingle et al. (2007 ▶); Kimura (1994 ▶); Lipscomb & Sträter (1996 ▶); Szajna-Fuller et al. (2007 ▶).

Experimental

Crystal data

[Zn(C₂₀H₁₇N₄O₃)₂(H₂O)₂]
M _r = 824.18
Monoclinic,
a = 16.357 (4) Å
b = 14.723 (4) Å
c = 15.135 (4) Å
β = 91.938 (7)°
V = 3642.9 (16) Å³
Z = 4
Mo Kα radiation
μ = 0.74 mm⁻¹
T = 293 (2) K
0.35 × 0.3 × 0.2 mm

Data collection

Bruker SMART APEX CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.757, T _max = 0.854
21455 measured reflections
4398 independent reflections
3575 reflections with I > 2σ(I)
R _int = 0.061

Refinement

R[F ² > 2σ(F ²)] = 0.060
wR(F ²) = 0.130
S = 1.11
4398 reflections
260 parameters
H-atom parameters constrained
Δρ_max = 0.52 e Å⁻³
Δρ_min = −0.42 e Å⁻³

Data collection: SMART (Bruker, 2007 ▶); cell refinement: SAINT (Bruker, 2007 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 1997 ▶) and Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808016693/hy2136sup1.cif

e-64-0m884-sup1.cif^{(22.5KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808016693/hy2136Isup2.hkl

e-64-0m884-Isup2.hkl^{(211.2KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected geometric parameters (Å, °).

O1—Zn1	1.9772 (18)
O2—Zn1	2.1572 (19)
O4—Zn1	2.149 (2)

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O1—Zn1—O1ⁱ	175.44 (11)
O1—Zn1—O4ⁱ	85.97 (8)
O1—Zn1—O4	97.42 (8)
O4ⁱ—Zn1—O4	84.55 (12)
O1—Zn1—O2	84.29 (7)
O4—Zn1—O2	91.26 (8)
O1—Zn1—O2ⁱ	92.61 (8)
O4—Zn1—O2ⁱ	168.82 (8)
O2—Zn1—O2ⁱ	94.67 (12)

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Symmetry code: (i) Inline graphic .

Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N3—H3A⋯O1	0.86	1.93	2.623 (3)	136
N1—H1⋯N4ⁱⁱ	0.86	2.20	3.007 (4)	155
O4—H24⋯O3ⁱⁱⁱ	0.85	1.87	2.712 (3)	174
O4—H23⋯N2^iv	0.87	2.03	2.879 (3)	163

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Symmetry codes: (ii) Inline graphic ; (iii) ; (iv) .

Acknowledgments

Financial support from the Thailand Research Fund (MRG5080149 and RTA5080006) and the Centre of Innovation in Chemistry: Postgraduate Education and Research Program in Chemistry (PERCH-CIC) are gratefully acknowledged.

supplementary crystallographic information

Comment

Zinc complexes of common amide-containing ligands have been widely explored and have received much attention in biomimetic research (Ingle et al., 2007). For example, the zinc complex with 6-(pivaloylamido-2-pyridylmethyl)amine ligand has been synthesized to serve as models for amide hydrolysis activity (Szajna-Fuller et al., 2007). Recently, zinc and copper complexes with a family of pyridylmethylamide ligands have been synthesized and showed that these ligands coordinate to metal ions with different coordination modes (Chaudhuri et al., 2007). It should be mentioned that zinc complexes containing aqua ligands have been used as model studies for zinc-hydrolase enzyme because of the functional unit at the active site of zinc-hydrolase enzyme is a zinc-bound water molecule, which is deprotonated at near neutral pH to generate a strongly nucleophilic Zn—OH group (Lipscomb & Sträter, 1996). Moreover, the aqua ligand bound to zinc ion is further stabilized via the formation of a hydrogen bond with a carboxylate or phenolic group from amino acid residues (Kimura, 1994). This hydrogen bond has been postulated to play a role in the activation of the coordinated aqua ligand in the catalytic pathway.

In an ongoing effort to study the interaction of zinc ion with aqua ligand, we report here the synthesis and characterization of the title compound, a new zinc complex with 2,6-bis[(pyridin-2-ylmethyl)carbamoyl]phenolate and aqua ligands. The electrospray mass spectrometry (ESI-MS) of the title compound confirmed the presence of the molecular species in solution. The compound has fragmentation patterns with peaks at m/z = 823.17 and 787.19; the former corresponds to the [M+2H₂O+H⁺] ion and the latter is consistent with the loss of two coordinated water molecules [M–2H₂O+H⁺]. The evidence for the presence of water in the complex is also given by IR absorption at 3568 cm^-1. The elemental analysis agrees well with the proposed structure.

In the title compound, the Zn^II atom is situated on a twofold rotation axis in a distorted octahedral coordination geometry, which is defined by two phenolate O atoms, two carbonyl O atoms and two cis water molecules (Fig. 1). The O1—Zn1—O1ⁱ and O4—Zn1—O2ⁱ [symmetry code: (i) -x, y, 1/2 - z] angles deviate from linearity (Table 1). These results are in accordance with the distorted octahedral geometry. It is noteworthy that each ligand behaves in a bidentate coordination fashion involving one phenolate O atom and one carbonyl O atom, while the two amide N atoms and pyridyl N atoms are free of coordination with the Zn atom. The two phenyl rings of coordinated molecules are tilted to one another with a dihedral angle of 72.3 (3)°. Remarkably, the intramolecular N3—H3A···O1 hydrogen bond forms a pseudo-six-membered ring (Fig. 1).

The water molecule is involved in an extensive intermolecular hydrogen-bonding network, as shown in Fig. 2. Atom O4 of aqua ligand acts as a hydrogen-bond donor to the uncoordinated carbonyl O3 atom and uncoordinated pyridyl N2 atom of adjacent complex molecules, respectively (Table 2). Additionally, the molecules are held together by intermolecular hydrogen bond between the uncoordinated amide N1 atom and uncoordinated pyridyl N4 atom. Not only the intermolecular hydrogen bonds, but also there are intermolecular π–π interactions in the crystal structure, which occur between the pyridyl rings containing atoms N2 and N4 of adjacent molecules, with a centroid–centroid distance of 3.666 (3) Å.

Experimental

Intermediate products (I), (II) (Gumbley & Stewart, 1984) and (III) (Goldsmith et al., 2002) have been synthesized in accordance with the published procedures. The methods to synthesize compounds (IV) and (V) are shown in Fig. 3.

A methanol solution (5 ml) of Zn(ClO₄)₂.6H₂O (2.22 g, 5.96 mmol) was added dropwise to a stirred solution of compound (V) (1.00 g, 2.98 mmol) in methanol (10 ml) at room temperature and the solution was stirred for 3 h. Water (10 ml) was added to the solution to precipitate a white solid. The precipitate was filtered off and washed with water to obtain the white powder of the title compound (yield 28%, 0.66 g). m.p. 170–173 °C. Recrystallization of this powder in methanol yielded colourless block crystals of the title compound, suitable for X-ray diffraction study. Analysis, calculated for C₄₀H₃₈N₈O₈Zn: C 58.29, H 4.65, N 13.60%; found: C 58.20, H 4.67, N 13.61%. ¹H-NMR (400 MHz, DMSO-d₆): δ 10.95 (bs, 2H, –NH), 8.50 (d, J = 4.0 Hz, 2H, ArH), 7.95 (s, 2H, ArH), 7.74 (t, J = 7.6 Hz, 2H, ArH), 7.33 (t, J = 8.0 Hz, 2H, ArH), 7.26 (t, J = 5.6 Hz, 2H, ArH), 6.60 (bs,1H, ArH), 4.60 (s, 2H, –CH₂–), 4.59 (s, 2H,–CH₂–). ¹³C-NMR (100 MHz, DMSO-d₆): δ 168.97, 159.20, 149.25, 137.39, 133.99, 122.61, 121.66, 111.55, 44.73. ESI-MS: m/z 787.19 [M–2H₂O+H⁺], 823.17 [M+2H₂O+H⁺].