A binuclear cobalt(II) complex of an NO3-donor Schiff base derived from 3-carboxyl­salicylaldehyde and 2-nitro­aniline

Zhao-Wen Yu; Ling Chang; Peng Sun; Min-Hui He

doi:10.1107/S1600536808042487

. 2008 Dec 20;65(Pt 1):m119–m120. doi: 10.1107/S1600536808042487

A binuclear cobalt(II) complex of an NO₃-donor Schiff base derived from 3-carboxylsalicylaldehyde and 2-nitroaniline

Zhao-Wen Yu ^a,^*, Ling Chang ^a, Peng Sun ^a, Min-Hui He ^a

PMCID: PMC2968020 PMID: 21581483

Abstract

In the crystal structure of the centrosymmetric title complex, bis{μ-3-[(2-nitrophenyl)iminomethyl]-2-oxidobenzoato}dicobalt(II), [Co₂(C₁₄H₈N₂O₅)₂], in which the ligand is 3-[(2-nitrophenyl)iminomethyl]-2-oxidobenzoate, a Schiff base synthesized from 2-nitroaniline with 3-carboxylsalicylaldehyde, the two cobalt(II) ions in the molecular unit are bridged by two phenolate O atoms of the ligands. Each metal centre has a distorted square-planar geometry. In the crystal structure, molecules are linked by Co⋯O interactions involving the nitro O atoms, forming a two-dimensional network. There are also C—H⋯O and π–π stacking interactions [centroid–centroid distances of 3.5004 (2), 3.6671 (2) and 3.6677 (2) Å] between adjacent benzene rings of the two-dimensional networks, leading to the formation of a three-dimensional framework.

Related literature

For binuclear cobalt(II) complexes of Schiff base ligands, see: Adams et al. (2002 ▶); Tone et al. (2007 ▶). For the design of molecular solids, see: Zheng et al. (2003 ▶). For bond-valence parameters, see: Brown & Altermatt (1985 ▶). For luminescence emission, see: Li et al. (2008 ▶).

Experimental

Crystal data

[Co₂(C₁₄H₈N₂O₅)₂]
M _r = 686.31
Monoclinic,
a = 8.3398 (6) Å
b = 11.0454 (8) Å
c = 13.3681 (9) Å
β = 99.6040 (10)°
V = 1214.16 (15) Å³
Z = 2
Mo Kα radiation
μ = 1.44 mm⁻¹
T = 296 (2) K
0.21 × 0.16 × 0.11 mm

Data collection

Bruker APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.752, T _max = 0.858
6134 measured reflections
2132 independent reflections
1536 reflections with I > 2σ(I)
R _int = 0.045

Refinement

R[F ² > 2σ(F ²)] = 0.045
wR(F ²) = 0.123
S = 1.00
2132 reflections
199 parameters
H-atom parameters constrained
Δρ_max = 0.63 e Å⁻³
Δρ_min = −0.34 e Å⁻³

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: SAINT (Bruker, 2005 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL and PLATON (Spek, 2003 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808042487/su2076sup1.cif

e-65-0m119-sup1.cif^{(22.2KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808042487/su2076Isup2.hkl

e-65-0m119-Isup2.hkl^{(104.9KB, hkl)}

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

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

Co1—O3	1.936 (3)
Co1—N1	1.947 (4)
Co1—O2ⁱ	1.874 (3)
Co1—O3ⁱ	1.929 (3)

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Co1⋯O4	2.807 (4)
Co1⋯O5ⁱⁱ	2.867 (5)

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O3—Co1—N1	92.51 (14)
O2ⁱ—Co1—O3	171.54 (13)
O3—Co1—O3ⁱ	78.42 (11)
O2ⁱ—Co1—N1	95.83 (14)
O3ⁱ—Co1—N1	170.41 (14)
O2ⁱ—Co1—O3ⁱ	93.33 (12)

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Symmetry codes: (i) Inline graphic ; (ii) .

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C8—H8⋯O5ⁱⁱⁱ	0.93	2.55	3.295 (6)	138
C12—H12⋯O1^iv	0.93	2.58	3.230 (7)	128

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

Acknowledgments

The authors are grateful for financial support from the Henan Administration of Science and Technology (grant No. 0111030700).

supplementary crystallographic information

Comment

Weak intermolecular forces, such as hydrogen bonding, π—π stacking, dipole—dipole attractions, and van der Waals interactions, have been studied in depth and can be used in the design of molecular solids with specific supramolecular structures and functions (Zheng et al., 2003). Numerous binuclear cobalt(II) complexes of Schiff bases have been studied (Tone et al., 2007). To the best of our knowledge, 2-NA (2-nitroaniline) Schiff bases have not been reported up to now. As a result of our interest in the design of organic systems suitable for the assembly of supramolecular compounds, we have synthesized the Schiff base ligand H₂CSNA, from the condensation reaction of 3-carboxylsalicylaldehyde with 2-nitroaniline, and its binuclear cobalt(II) complex, [Co₂(CSNA)₂], (I) [where CSNA^2- = 3-[(2-nitrophenyl)iminomethyl]-2-oxidobenzoate dianion].

Complex (I), a 2-NA Schiff base cobalt(II) complex, consists of centrosymmetric binuclear molecular units of [Co₂(CSNA)₂], as shown in Fig. 1. Selected bond distances and angles are given in Table 1. Each molecular unit contains two CSNA^2- anions and two Co²⁺ ions. The two CSNA^2- anions act as N1,O2,O3 tridentate ligands to chelate two Co²⁺ ions with the phenolate O-atoms (O3 and O3ⁱ: (i) = -x + 2, -y, -z + 1) as bridging atoms. The distance between the two metal centres is found to be 2.9950 (11) Å. These coordination bonds, forming a basal plane, are of normal strength with average bond length of Co—O 1.914 (3) Å, and Co—N 1.947 (4) Å.

The distances of the nitro group O-atoms O4 and O5ⁱ [symmetry code: (i) -x + 2, -y, -z + 1] to atom Co1 are 2.8066 (44) Å and 2.8667 (44) Å, respectively. Calculated by the formula of s = exp[(r_o-r)/B], (r = bond length, s = bond value) (Brown & Altermatt, 1985), the two bond values are 0.049 and 0.042. Hence, only weak interactions exist between atoms O4 and Co1, and Co1 and O5ⁱ (Tabel 1). Thus every binuclear cobalt unit interacts with four adjacent ones through four nitro groups, forming a two-dimensional network (Fig. 2). The conformation of the ligand has changed obviously after coordination. It can be deduced that the free ligand might be a planar molecule because all the nonhydrogen atoms are in a conjugated system. In order to fulfil the intramolecular axial interaction of the nitro group, distortion has occurred between the two benzene rings of the ligand. In the binuclear molecular unit, the dihedral angle between the two benzene rings is 64.31 (13)°.

In the crystal structure there are C—H···O(nitro) interactions (Table 2), and relatively strong π···π stacking interactions [the distances between the centroids of the adjacent benzene rings are 3.5004 (2) Å, 3.6671 (2) Å and 3.6677 (2) Å] leading to the formation of a three-dimensional framework (Fig. 3).

The emission spectra of ethanol solutions of H₂CSNA and complex (I) were measured at rt. As seen in Fig. 4, the results show that H₂CSNA, exhibits two emissions at 394 nm and 466 nm (ν_ex = 351 nm). Measurement of the complex revealed two emissions at 394 nm and 468 nm (ν_ex = 351 nm). The similarity of the emissions bands of complex (I) and H₂CSNA indicates that the luminescence emission of complex (I) may be assigned to the intraligand emission of the H₂CSNA ligand (Li et al., 2008).

In summary, an unprecedented 2-nitroaniline Schiff base complex, [Co₂(CSNA)₂], has been synthesized and structurally characterized. This successful synthesis provides a feasible and effective synthetic method for searching and exploring other novel 2-nitroaniline Schiff base complexes.

Experimental

0.166 g (1.0 mmol) of 3-carboxylsalicylaldehyde and 0.138 g (1.0 mmol) of 2-nitroaniline were dissolved in 10 ml of methanol. The mixture was stirred at 60°C, and gradually a yellow precipitate (H₂CSNA) was formed. 1 h later, 10 ml of a methanol solution of 0.08 g (2.0 mmol) NaOH, and 10 ml of a methanol solution of 0.285 g (1.2 mmol) CoCl₂.6H₂O were added to the H₂CSNA solution, sequentially. After sirring for 1 h at 60°C the solution was allowed to cool to rt and then filtered. The filtrate was left to slowly evaporate at rt. After 10 d, blue crystals, suitable for X-ray structural analysis, were formed. FT/IR data for compound (I): 1634 cm^-1(s, C=N), 1601 cm^-1(s, benzene ring), 1579 cm^-1(s, ν_as(COO)), 1549 cm^-1 (s, ν_as(NO₂)), 1360 cm^-1 (s, ν_s(COO)), 1299 cm^-1 (s, ν_s(NO₂)).