КООРДИНАЦИОННАЯ ХИМИЯ, 2015, том 41, № 8, с. 460-466
УДК 541.49
SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF OXOVANADIUM(V) COMPLEXES WITH MIXED TRIDENTATE BENZOHYDRAZONE AND BIDENTATE NO LIGANDS
© 2015 G. H. Sheng1, Y. W. Han1, Y. Xu1, X. M. Hu1, Z. L. You2, *, H. L. Zhu1 *
1School of Life Sciences, Shandong University of Technology, ZiBo, 255049 P.R. China 2Department of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian, 116029 P.R. China *E-mail:youzhonglu@126.com; hailiang_zhu@163.com Received January 13, 2015
New oxovanadium(V) complexes, [VO(L1)(Bha)] (I) and [VO(L2)(Qnl)] (II), were prepared by the reactions of [VO(Acac)2] (Acac = acetylacetonate), (4-nitrophenoxy)acetic acid [1-(2-hydroxy-3-methylphe-nyl)methylidene]hydrazide (H2L1) and benzohydroxamic acid (HBha), and [VO(Acac)2], N'-(2-hydroxy-5-methylbenzylidene)-3-methylbenzohydrazide (H2L2), and 8-hydroxyquinoline (HQnl) in methanol, respectively. Crystal and molecular structures of complexes I and II were determined by elemental analysis, infrared and UV-Vis spectra and single crystal X-ray diffraction (CIF files CCDC nos. 1000875 (I) and 1012028 (II)). The V atoms in the complexes are in octahedral coordination. Thermal stability of complex I was studied.
DOI: 10.7868/S0132344X15080046
INTRODUCTION
Two classes of vanadium enzymes, viz■ vanadium-nitrogenases and vanadate-dependent haloperoxidases, have so far been found in nature, and their structures and properties have stimulated the search for structural and functional model compounds [1—5]. In recent years, vanadium complexes have been reported to have interesting biological activities, such as normalizing the high blood glucose levels and acting as models of haloperoxidases [6—8]. The remarkable biological activity of acid hydrazides R—CO—NH—NH2, their corresponding aroylhydrazones, R—CO—NH—N=CH—R', and the dependence of their mode of chelation with transition metal ions present in the living system have been of significant interest [9—11]. Recently, our re-
search group has reported a few metal complexes with biological activities [12—16]. Benzohydroxamic acid (HBha) and 8-hydroxyquinoline (HQnl) are typical bidentate ligands in coordination chemistry. The introduction of such ligands may introduce new vanadium complexes with novel catalytic or biological properties. In the present paper, new oxovanadium(V) complexes, [VO(L1)(Bha)] (I) and [VO(L2)(Qnl)] (II), where L1 and L2 are the deprotonated forms of (4-nitrophe-noxy)acetic acid [1-(2-hydroxy-3-methylphenyl)me-thylidene]hydrazide (H2L1) and N'-(2-hydroxy-5-methylbenzylidene) - 3 -methylbenzohydrazide (H2L2), respectively, and Bha and Qnl are the deprotonated forms of benzohydroxamic acid and 8-hydroxyquino-line, respectively, are presented.
N OH
O
no2
O
SN ^OH
(H2L1)
EXPERIMENTAL
Materials and methods. Commercially available 3-methylsalicylaldehyde, 5-methylsalicylaldehyde, (4-nitrophenoxy)acetic acid hydrazide, and 3-meth-ylbenzohydrazide were purchased from Sigma-Ald-rich. Other solvents and reagents were made in China and used as received. C, H and N elemental analyses
(H2L2)
were performed with a PerkinElmer elemental analyser. Infrared spectra were recorded on a Nicolet AVATAR 360 spectrometer as KBr pellets in the (4000-400) cm-1 region. UV-Vis spectrum was recorded on Lambda 900 spectrometer. Thermal stability analysis was performed on a PerkinElmer Pyris Diamond TGA-DTA thermal analyses system.
Synthesis of I. 3-Methylsalicylaldehyde (1.0 mmol, 0.136 g) and (4-nitrophenoxy)acetic acid hydrazide (1.0 mmol, 0.201 g) were mixed in 20 mL methanol and refluxed for 30 min. To the solution was added dropwise a methanolic solution (20 mL) of [VO(Acac)2] (1.0 mmol, 0.265 g) and HBha (1.0 mmol, 0.137 g). The color of the reaction mixture changed from colorless to dark brown. The final mixture was further stirred at reflux for 30 min and cooled to room temperature. The filtrate was allowed to stand in air for a few days. Brown block-shaped crystals suitable for X-ray single crystal diffraction were formed at the bottom of the vessel. The isolated products were washed three times with cold methanol and dried in air. The yield was 46%.
For C23H19N4OsV
anal. calcd., %: C, 52.1; H, 3.6; N, 10.6. Found, %: C, 51.9; H, 3.7; N, 10.5.
Synthesis of II. 5-Methylsalicylaldehyde (1.0 mmol, 0.136 g) and 3-methylbenzohydrazide (1.0 mmol, 0.150 g) were mixed in 20 mL methanol and refluxed for 30 min. To the solution was added dropwise a methanolic solution (20 mL) of [VO(Acac)2] (1.0 mmol, 0.265 g) and HQnl (1.0 mmol, 0.145 g). The color of the reaction mixture changed from colorless to dark brown. The final mixture was further stirred at reflux for 30 min and cooled to room temperature. The filtrate was allowed to stand in air for a few days. Brown block-shaped crystals suitable for X-ray single crystal diffraction were formed at the bottom of the vessel. The isolated products were washed three times with cold methanol and dried in air. The yield was 40%.
For C25H20N3O4V
anal. calcd., %: C, 62.9; H, 4.2; N, 8.8. Found, %: C, 62.7; H, 4.3; N, 8.9.
X-ray crystallography. Diffraction intensities for the complexes I, II were collected at 298(2) K using a Bruker D8 VENTURE PHOTON diffractometer with Mo^ radiation (X = 0.71073 A). The collected data were reduced using the SAINT program [17], and multi-scan absorption corrections were performed using the SADABS program [18]. The structures were solved by direct methods and refined against F2 by full-matrix least-squares methods using the SHELXTL [19]. All of the non-hydrogen atoms were refined anisotropically. H atoms were placed in idealized positions and constrained to ride on their parent atoms. Crystallograph-ic data are summarized in Table 1. Selected bond lengths and angles are given in Table 2.
Supplementary material for complexes I, II has been deposited with the Cambridge Crystallographic
Data Centre (nos. 1000875 (I) and 1012028 (II); deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).
RESULTS AND DISCUSSION
Replacement of two acetylacetonate ligands of [VO(Acac)2] by hydrazone and Bha or Qnl ligands in methanol resulted in the formation of the complexes. The complexes are soluble in DMF, DMSO, methanol, ethanol, and acetonitrile. Molar conductance of the complexes at the concentration of10-4 mol L-1 are 18 and 31 fi-1 cm2 mol-1, indicating their non-electrolyte nature [20].
The molecular structure and atom numbering scheme of complex I is shown in Fig. 1a. The V atom in the complex is in octahedral coordination with the three donor atoms of the hydrazone ligand and the hydroxy O atom of the Bha ligand defining the equatorial plane, and with one oxo O atom and the carbonyl O atom of the Bha ligand occupying the axial positions. The distance V(1)-O(8) is 1.584(3) Â, indicating it is a typical V=O double bond. The bond lengths in complex Imare similar to those observed in the mononuclear oxovanadium(V) complexes with octahedral coordination [21, 22]. The angular distortion in the octahedral environment around V comes from the five- and six-membered chelate rings taken by the hydrazone ligand. For the same reason, the trans angles significantly deviate from the ideal values of180°. Distortion of the octahedral coordination can be observed from the coordinate bond angles, ranging from 74.5(1)° to 106.2(1)° for the perpendicular angles and from 152.1(1)° to 172.1(1)° for the diagonal angles. The displacement of the V atom from the equatorial plane is 0.285(1) Â. The dihedral angle between the two benzene rings of the hydrazone ligand is 14.8(3)°. In the crystal structure of complex I, two adjacent molecules are linked through intermolecular hydrogen bonds oftype N-H-O (N(4)-H(4A)-O(2): N(4)-H(4A) 0.90(1), H(4A)-O(2) 2.03(2), N(4)-O(2) 2.896(4) Â, N(4)-H(4A)-O(2) 161(5)°; N(4)-H(4A)-O(3): N(4)-H(4A) 0.90(1), H(4A)-O(3) 2.58(4), N(4)-O(3) 3.196(4) Â, N(4)-H(4A)-O(3) 126(4)°) to form dimers (Fig. 2).
The molecular structure and atom numbering scheme of complex II are shown in Fig. 1b. The V atom in complex II is in octahedral coordination, with the three donor atoms of the hydrazone ligand and the hydroxy O atom of the Qnl ligand defining the equatorial plane and with one oxo O atom and the pyridine N atom of the Qnl ligand occupying the axial positions. The distance V(1)-O(4) is 1.576(5) Â, indicating it is a typical V=O double bond. The V-N(Py) bond in complex II is significantly longer than the other coordinate bonds, yet it is not uncommon for such complexes [23, 24]. The bond lengths in complex II are comparable to those observed in the mononuclear ox-ovanadium(V) complexes with octahedral coordination [23, 24]. The angular distortion in the octahedral
Table 1. Crystallographic data and structure refinement for complexes I and II
Parameter Value
I II
Mr 530.36 477.38
Crystal shape/color Block/brown Block/deep brown
Crystal size, mm 0.18 x 0.17 x 0.15 0.23 x 0.23 x 0.22
Crystal system Triclinic Monoclinic
Space group PI P21/c
a, A 9.7695(6) 12.560(3)
b, A 10.9349(6) 12.641(3)
c, A 12.4862(8) 14.389(3)
a, deg 105.777(2) 90
P, deg 107.229(2) 93.015(2)
Y, deg 103.199(2) 90
V, A3 1154.7(1) 2281.4(8)
Z 2 4
Pcalcd g cm-3 1.525 1.390
^(MoJa), mm-1 0.488 0.471
/(000) 544 984
Measured reflections 11207 7460
Independent reflections 4289 2524
Observed reflections (I > 2ct(I)) 3235 1532
Min and max transmission 0.9174 and 0.9305 0.8993 and 0.9034
Number of refinement parameters 329 287
Restraints 1 30
Goodness-of-fit on F2 1.057 1.019
R1, wR2 (I> 2a(I))* 0.0601, 0.1520 0.0604, 0.1555
R1, wR2 (all data)* 0.0839, 0.1674 0.1103, 0.1818
; R1 = Fo - Fc/F0, wR2 = Ew( Fo - I? )/Sw( I? )2]1/2.
environment around the V comes from the five- and six-membered chelate rings taken by the hydrazone ligand. For the same reason, the trans angles significantly deviate from the ideal values of1
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