КООРДИНАЦИОННАЯ ХИМИЯ, 2015, том 41, № 7, с. 424-429
New ц-OAC BRIDGED DINUCLEAR COPPER(II) COMPLEX WITH TRIDENTATE SCHIFF BASE LIGAND: SYNTHESIS, CHARACTERIZATION, CRYSTAL STRUCTURE, AND CuO NANO-PARTICLES FORMATION
© 2015 G. Grivani1, *, V. Eigner2, M. Dusek2, B. Sadeghi1, and A. D. Khalaji3
1School of Chemistry, Damghan University, Damghan, 36715-364 Iran 2Institute of Physics ASCR, v. v. i., Na Slovance 2, 18221 Prague, Czech Republic 3Department of Chemistry, Faculty of Science, Golestan University, Gorgan, Iran *E-mail: firstname.lastname@example.org Received October 23, 2014
A new (p.-acetato)-bridged dinuclear copper(II) complex [Cu2(L)2(p.-OAc)2] (I) has been synthesized by the reaction of a tridentate N2O Schiff base ligand (HL) with Cu(OAC)2 in methanol at refluxed conditions and characterized by elemental analyses (CHN) and FT-IR spectroscopy. The crystal structure of I was investigated by single-crystal X-ray diffraction (CIF file CCDC no. 1013907). X-ray results showed that two OAC groups bridge the copper(II) ions in a Cu2O2 core of a binuclear complex. Each copper(II) ion adopts a distorted square-pyramidal geometry with one imine nitrogen, one amine nitrogen and one phenolato oxygen from the tridentate Schiff base ligand, completed by two acetate oxygen atoms. Finally, the complex was thermally decomposed in order to obtain CuO nano-particles. The particles were characterized by powder X-ray diffraction, which confirmed the formation of the CuO nano-particles with the average size of 24 nm.
Schiff bases as chelating ligands play central role in the main group and transition metal coordination chemistry [1, 2] because of their simple preparation in one-pot condensation of aldehydes (or ketones) and primary amines in an alcohol solvent. They are capable to bind with transition, non-transition, lanthanide and actinide metal ions to give complexes with suit-ableproperties for theoretical studies and/or practical applications [3—5]. The metal complexes with Schiff base ligands have been extensively investigated for more than one century and investigated in many dif-
ferent aspects, including biological studies [6—12], magneto chemistry , non-linear optics , photo physical studies , catalysis , materials chemistry , chemical analysis , absorption and transport of oxygen . As an additional contribution to the synthesis, characterization, and crystal structure of transition metal Schiff base complexes and in the course of our ongoing studies of these kinds of materials [20—25], we describe here the synthesis, characterization and crystal structure of a new (^-acetato)-bridged dinuclear cop-per(II) complex [Cu2(L)2(^-OAc)2] (I).
=N ,N(Me)2 VcH3 Си-O^
Materials and physical measurements. All reagents and solvents for synthesis and analysis were commercially available and purchased from Merck and used as received without further purifications. FT-IR spectrum was recorded in the range 400—4000 cm-1 on a PerkinElmer FT-IR spectrophotometer using KBr pellets. Elemental analyses were performed on a Heraeus CHN-O-Rapid analyzer and results agreed with calculated values. 1H NMR spectrum was recorded on a BRUKER DRX-500 AVANCE spectrometer at 300 MHz for the Schiff base ligand. UV-Vis spectra were recorded by PerkinElmer Spectrometer Lambda 25.
Synthesis of HL. In a 100 mL round-bottmflask containing 70 mL methanol, 5-bromo-2-hydroxy-benzaldehyde (10 mmol) and N,N-dimethyl ethylen-diamin (10 mmol, 2.04 g) were added and the mixture was refluxed for 4 h with stirring. After evaporating the solvent, the yellow precipitate was collected and dried in air. The yield was 80%. M.p. = 51°C.
Table 1. Crystallographic data and structural refinement details of complex I
For CnH15N2OBr anal. calcd., %: Found, %:
C, 48.73; C, 48.72;
H, 5.50; H, 5.53;
N, 10.29. N, 10.33.
IR (KBr; v, cm-1): 1637 v(C=N). 1H NMR (CDCl3; S, ppm): 13.5 (s., 1H, O-H), 8.27 (s., 1H: H—C=N), 7.36 (m., 2H: phenyl-H), 3.71 (t., 2H: N-CH2), 2.63 (t., 2H: CH2-N) and 2.29 (s., 6H: N(CH3)2).
Synthesis of I. In a 100 mL round-bottom flask containing 60 mL methanol HL (1.8 mmol) and Cu(OAc)2 • 2H2O (0.9 mmol) were added and the content was refluxed for 2 h with stirring. After evaporating the solvent, the resulting green powder was dried in air and recrystallized in CHCl3 by slow evaporation method. The greenish crystals that formed were filtered off, washed with «-hexane and dried in an oven. M.p. = 206°C.
anal. calcd., %: C, 39.79; H, 4.32; N, 7.11. Found, %: C, 39.75; H, 4.33; N, 7.13.
IR (KBr v, cm-1): 1629 v(C=N).
X-ray structure determination. Suitable single crystal of I (0.11 x 0.07 x 0.02 mm) was chosen for X-ray diffraction study. Crystallographic measurements were done at room temperature with four circle CCD dif-fractometer Gemini of Oxford diffraction, Ltd., using Mo^a radiation (X = 1.5418 A), sealed X-ray tube col-limated by mirrors and CCD detector Atlas. The crystal structure was solved by direct methods with program SIR2002  and refined with program package Jana2006  by full-matrix least-squares technique
Formula weight 785.47
Crystal system Triclinic
Space group p1
a, A 7.9195(3)
b, A 8.8831(3)
c, A 10.9520(4)
a, deg 96.854(3)
P, deg 99.641(3)
Y, deg 104.633(3)
V, A3 724.32(5)
p., mm-1 5.45
Measured reflections/independent 10845/2540
Reflections with I > 3a(I) 2540
R (F2 > 2ct(F2)) 0.025
wR (F2) 0.60
APmaxAPmirn « A-3 0.56/—0.64
on F2. The molecular structure plots were prepared by ORTEP III . Hydrogen atoms were mostly discernible in difference Fourier maps and could be refined to reasonable geometry. According to common practice, they were nevertheless kept in ideal positions during the refinement. The isotropic atomic displacement parameters of hydrogen atoms were evaluated as 1.2 ^eq of the parent atom. Crystallographic data, details of the data collection and structure solution and renements are listed in Table 1, while the selected bond distances and angles are present in Table 2. Supplementary material has been deposited with the Cambridge Crystallographic Data Centre (CCDC no. 1013907) and it is available through an e-mail request at email@example.com or through a web form at http://www.ccdc.cam.ac.uk.
RESULTS AND DISCUSSION
The tridentate N2O Schiff base ligand (HL) was prepared by the condensation of 5-bromo-2-hydroxy-benzaldehyde and N,N-dimethyl ethlylenediamine in
Table 2. Selected bond distances (A) and angles (deg) of I*
Bond d, A Bond d, A
Cu(1)-O(1) 1. 9401(19) C(11)-N(12) 1.485(3)
Cu(1)-N(9) 1.9693(19) N(12)-C(13) 1.479(3)
Cu(1)-N(12) 2.099(2) N(12)-C(14) 1.477(4)
Cu(1)-O(1a) 1.9591(15) O(1a)-C(2a) 1.291(3)
Br(1)-C(5) 1.904(2) C(2a)-O(3a) 1.233(3)
C(8)-N(9) 1.284(3) C(2a)-C(4a) 1.502(3)
N(9)-C(10) 1.470(4) O(1)-C(2) 1.301(3)
Angle ro, deg Angle ro, deg
O(1)Cu(1)N(9) 90.91(8) C(8)N(9)C(10) 118.4(2)
O(1)Cu(1)N(12) 171.40(8) N(9)C(10)C(11) 108.0(2)
O(1)Cu(1)O(1a) 91.00(7) C(10)C(11)N(12) 110.4(2)
N(9)Cu(1)N(12) 82.89(8) Cu(1)N(12)C(11) 103.98(15)
N(9)Cu(1)O(1a) 175.02(8) Cu(1)N(12)C(13) 114.99(17)
N(12)Cu(1)O(1a) 94.70(7) Cu(1)N(12)C(14) 109.75(15)
Cu(1)O(1)C(2) 125.48(18) C(11)N(12)C(13) 108.60(19)
O(1)C(2)C(3) 119.9(2) C(11)N(12)C(14) 110.7(2)
O(1)C(2)C(7) 123.7(2) C(13)N(12)C(14) 108.73(19)
Cu(1)N(9)C(8) 126.21(19) Cu(1)O(1a)C(2a) 113.92(16)
Cu(1)N(9)C(10) 115.41(13) O(1a)C(2a)O(3a) 122.7(2)
O(3a)C(2a)C(4a) 121.8(2) O(1a)C(2a)C(4a) 115.6(2)
methanol in refluxed conditions and isolated by evaporation of the solvent. The corresponding dinuclear copper(II) complex I was synthesized by the reaction of Cu(OAc)2 • H2O with HL in methanol in refluxed conditions in two separated reactions. The ligand and complex are quite air stable as a solid as well as in a solution.
The HL ligand and its dinuclear copper(II) complex I were characterized by the FT-IR and UV-Vis spectroscopy and elemental (CHN) analysis. In addition, HL was characterized by 1H NMR spectroscopy. The CHN analysis of HL and complex I clearly confirmed the predicted chemical composition of both compounds.
The 1H NMR spectrum of HL is given in Fig. 1. The eight signals with the integrations ratio of 6 : 2 : 2 : : 1 : 1 : 2 : 1 were seen in this spectrum due to the aliphatic and aromatic protons. A singlet resonance appeared at 2.29 was attributed to the protons of two CH3 groups and two distinct triplet peaks at 2.62 and 3.71 ppm were corresponded to the aliphatic protons (-CH2-CH2—). The signals of aromatic protons were seen at 6.7—7.5 ppm. The resonance of iminic proton
(—CH=N—) was seen at 8.27 ppm. The chemical shift of phenolic proton (OH) was strongly shifted to down field and exhibited at 13.50 ppm. This high chemical shift can be related to the intramolecular hydrogen bonding between nitrogen of imine and hydrogen of phenol.
In the FT-IR spectrum of HL, a sharp band was appeared at 1637 cm-1, due to v(C=N) of azomethine group. This band was shifted to the lower wave number and appeared at 1629 cm-1 in FT-IR spectrum ofI, indicating the binding of azomethine nitrogen to copper ion.
The UV-Vis spectra of the HL and I are given in Fig. 2. There are two bands in the region of230-500 nm at 256 and 334 nm for the HL ligand due to the intra-ligand (n ^ n* and n ^ n*) transitions. These bands in the UV-Vis spectrum of I broadened and shifted to the higher wave lengths (red shift) and appeared at 257 and 398 nm, respectively, because of the anionic form of HL coordination (as phenolate) and resonance of charge in the longer route. In addition, a new band at 626 nm with very low intensity was appeared which was attributed to the d—d transitions of Cu2+ ion.
7.4 7.3 7.2 7.1 7.0 6.9 6.8 8, ppm
3.6 3.2 2.8 2.4
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