КООРДИНАЦИОННАЯ ХИМИЯ, 2010, том 36, № 6, с. 475-479
SYNTHESIS AND CRYSTAL STRUCTURES OF TWO SCHIFF BASE COPPER(II) COMPLEXES DERIVED FROM 4-CHLORO-2-[(2-MORPHOLIN-4-YLETHYLIMINO)METHYL]PHENOL AND 4-CHLORO-2-(CYCLOHEXYLIMINOMETHYL)PHENOL
© 2010 Y. L. Sang* and X. S. Lin
Department of Chemistry, Chifeng University, Chifeng 024001, P.R. China *E-mail: firstname.lastname@example.org Received October 28, 2009
A centrosymmetric mononuclear copper(II) complex, [Cu(L1)2] (I), and a phenolate oxygen—bridged dinuclear copper(II) complex, [Cu2(L2)4] (II) (HL1 = 4-chloro-2-[(2-morpholin-4-ylethylimino)methyl]phenol, HL2 = 4-chloro-2-(cyclohexylimino-methyl)phenol), were synthesized and characterized by elemental analyses, IR, and single crystal X-ray diffraction. The crystal of I is monoclinic: space group P2i/n, a = 13.396(3), b = 5.339(1), c = = 19.740(4) A, P = 108.64(3)°, V = 1337.8(5) A3, Z =2. The crystal of II is monoclinic: space group P21, a = 9.157(2), b = 22.715(4), c = 12.169(2) A, в = 95.28(3)°, V= 2520.4(8) A3, Z = 2. The Cu atom in I, lying on the inversion center, is four-coordinate in a square planar geometry with two phenolate oxygen and two imine nitrogen atoms. Each Cu atom in II is five-coordinate in a square pyramidal geometry with two phenolate oxygen and two imine nitrogen atoms from two L2 ligands defining the basal plane and with one phenolate oxygen atom of another L2 ligand occupying the apical position.
Schiff bases are readily synthesized by the condensation reaction of carbonyl compounds with primary amines [1, 2]. The metal complexes of Schiff bases have been received much attention. These complexes not only play an important role in the development ofcoordination chemistry related to catalysis, enzymatic reactions, magnetism, and molecular architectures [3—5], but also exhibit interesting biological activities [6—8].
The Schiff bases 4-chloro-2-[(2-morpholin-4-yleth-ylimino)methyl]phenol (HL1) and 4-chloro-2-(cyclo-hexyliminomethyl)phenol (HL2) are two versatile ligands. The complexes with HL1 have never been reported previously. The cadmium(II), cobalt(II), zinc(II), and nick-el(II) complexes with HL2 have been reported [9—12]. However, the copper(II) complexes with HL2 have never been reported so far. In this paper, a centrosymmetric mononuclear copper(II) complex, [Cu(L1)2] (I), and a phenolate oxygen-bridged dinuclear copper(II) complex, [Cu2(L2)4] (II), have been synthesized and structurally characterized.
Materials and measurements. 5-Chloro-2-hydroxy-benzaldehyde, 4-(2-aminoethyl)morpholine, and cyclo-hexylamine were obtained from Aldrich and used as received. Elemental analyses were performed using a Per-kinElmer 240C analytical instrument. Infrared spectra were recorded on a Nicolet 5DX FT-IR spectrophotometer with KBr pellets.
Synthesis of HL1 and HL2. HL1 was prepared by re-fluxing of 5-chloro-2-hydroxybenzaldehyde (156.6 mg, 1.0 mmol) and 4-(2-aminoethyl)-morpholine (130.2 mg, 1.0 mmol) in 30 ml ofmethanol for 0.5 h. The clear yellow solution was evaporated to give a yellow powder, which was washed three times with methanol and dried in air. The yield was 95%.
anal. calcd., %: C, 58.1; H, 6.4; N, 10.4. Found, %: C, 58.5; H, 6.2; N, 10.7.
Ligand HL2 was prepared by a similar procedure as that for HL1 with 4-(2-aminoethyl)morpholine replaced by cyclohexylamine (99.2 mg, 1.0 mmol). The yield was 97%.
For C13H16ClNO anal. calcd., %: Found, %:
C, 65.7; C, 65.3;
H, 6.8; H, 6.9;
N, 5.9. N, 6.1.
Synthesis of I. A solution of HL1 (26.8 mg, 0.1 mmol) in methanol (5 ml) was added with stirring to a solution of Cu(CH3COO)2 ■ H2O (20.0 mg, 0.1 mmol) in methanol (10 ml). The mixture was stirred at room temperature for 0.5 h and filtered. The filtrate was kept undisturbed at room temperature for a week. Blue crystals ofI suitable for X-ray diffraction were obtained on the slow evaporation of
Table 1. Crystallographic data and experimental details for structures I and II
Table 2. Selected bond lengths and bond angles for the complexes
Mr 599.0 1073.9
Habit Block Block
Crystal size, mm 0.20 x 0.18 x 0.17 0.17 x 0.15 x 0.15
Crystal system Monoclinic Monoclinic
Space group P2x/n P2 !
a, Â 13.396(3) 9.157(2)
b, Â 5.339(2) 22.715(4)
c, Â 19.740(4) 12.169(2)
P, deg 108.64(3) 95.28(3)
V, Â3 1337.8(5) 2520.4(8)
Z 2 2
p, g/cm3 1.487 1.415
p., mm-1 1.056 1.104
9 range, deg 1.63-27.00 1.68-27.00
1(000) 622 1116
-^min and Tmax 0.817 and 0.841 0.834 and 0.852
Number of measured reflections 7687 15333
Number of unique reflections 2910 9885
Number of observed reflections 1894 6822
Parameters/restraints 169/0 595/1
Rint 0.0475 0.0400
Goodness-of-fit on F2 1.030 1.008
R (I > 2ct(T)) R1 = 0.0482, wR2 = 0.1153 R1 = 0.0650, wR2 = 0.1574
R (all data) Rx = 0.0814, wR2 = 0.1309 Rx = 0.0978, wR2 = 0.1774
the solvent. The crystals were isolated by filtration and dried in air. The yield was 45% based on HL1.
anal. calcd., %: C, 52.1;
Found, %: C, 51.7;
H, 5.4; N, 9.4. H, 5.6; N, 9.7.
Bond d, Â Bond d, Â
Cu(1)-O(1) Cu(1)-O(1) Cu(1)-N(1) Cu(2)-O(4) Cu(2)-N(3) 1.880(2) I 1.885(4) 2.027(6) 1.892(5) 2.001(6) Cu(1)-N(1) I Cu(1)-O(2) Cu(1)-N(2) Cu(2)-O(3) Cu(2)-N(4) 2.015(3) 1.892(4) 2.039(6) 1.904(4) 2.005(6)
Angle ro, deg Angle ro, deg
O(1)Cu(1)N(1) O(1)Cu(1)O(2) O(2)Cu(1)N(1) O(2)Cu(1)N(2) O(4)Cu(2)O(3) O(3)Cu(2)N(3) O(3)Cu(2)N(4) 91.82(10) I 175.0(2) 89.0(2) 90.7(2) 160.2(2) 92.5(2) 90.8(2) I O(1)Cu(1)N(1) O(1)Cu(1)N(2) N(1)Cu(1)N(2) O(4)Cu(2)N(3) O(4)Cu(2)N(4) N(3)Cu(2)N(4) 91.2(2) 90.3(2) 166.1(2) 92.8(2) 93.8(2) 150.8(2)
filtration and dried in air. The yield was 72% based on HL2.
anal. calcd., (%): C, 58.2;
Found, (%): C, 57.5;
H, 5.6; N, 5.2. H, 5.7; N, 5.1.
Synthesis of II. A solution of HL2 (23.8 mg, 0.1 mmol) in methanol (5 ml) was added with stirring to a solution of Cu(CH3COO)2 ■ H2O (20.0 mg, 0.1 mmol) in methanol (10 ml). The mixture was stirred at room temperature for 0.5 h and filtered. The filtrate was kept undisturbed at room temperature for three days. Blue crystals of II suitable for X-ray diffraction were obtained on the slow evaporation of the solvent. The crystals were isolated by
X-ray structure determination. Suitable single crystals with high quality of complexes I and II were selected and mounted on a Bruker Smart 1000 CCD area-detector dif-fractometer with graphite monochromatized MoA^ radiation (X = 0.71073 E). Diffraction data for both complexes were collected by an ® scan mode at 298(2) K. Data reduction and cell refinement were performed by the SMART and SAINT programs . An empirical absorption correction was applied by using SADABS . The structures were solved by direct methods and refined with the full-matrix least-squares technique using the SHELXL-97 package . The non-hydrogen atoms in the structures were subjected to refined anisotropic refinement. Hydrogen atoms were located in geometrically and treated with the riding model. Crystallographic data and experimental details for the complexes are summarized in Table 1. Selected bond lengths and angles for the complexes are listed in Table 2.
Atomic coordinates and other structural parameters of complexes I and II have been deposited with the Cambridge Crystallographic Data Center (nos. 743838 (I) and 743839 (II); deposit@ccdc. cam.ac.uk or http://www.ccdc.cam.ac.uk).
KOOP,3HHAUHOHHAH XHMH3 tom 36 № 6 2010
RESULTS AND DISCUSSION
The two Schiff bases were readily synthesized according to the similar procedure in high yields. The two cop-per(II) complexes were also synthesized according to a similar procedure (Scheme), however, giving different
structures I and II. The main difference is between the two Schiff bases is the terminal groups. It can be seen that the steric effect of HL1 is larger than that of HL2, which may cause the difference between the structures of the two copper(II) complexes.
The weak and broad band in the region 3300— 3400 cm-1 is due to the stretching vibration of the phenolic OH groups of the Schiff bases. These bands are absent in the spectra of both the complexes indicating the coordination of the phenolate oxygen atoms of the Schiff bases to the copper atoms. The phenolic v(C-O) in the spectra of the Schiff bases are observed as strong bands at 1200 cm-1 for HL1 and 1203 cm-1 for HL2. However, in the spectra of both the complexes, the bands appear at 1182 cm-1 for I and 1185 cm-1 for II. This confirms the deprotona-tion and coordination of the phenolate oxygen atoms to the copper atoms. The strong bands at 1632 cm-1 in the spectrum of HL1 and 1637 cm-1 in the spectrum of HL2 are due to the azomethine groups of the Schiff bases. These bands are shifted toward lower frequencies (1617 cm-1 for I and 1612 cm-1 for II), indicating the coordination of the azomethine nitrogen atoms to the copper atoms. The middle bands at 287 cm-1 for I and 285 cm-1 for II are attributed to the Cu-N vibrations.
Figures 1 and 2 give the perspective views of complexes I and II, respectively.
In centrosymmetric complex I, the Cu atom, lying on the inversion center, is four-coordinate in a square planar geometry with two phenolate oxygen and two imine nitro-
gen atoms. The amine N atoms of the morpholine rings are not coordinate to the copper atom. The structure of I is similar to those reported previously [16, 17].
Complex II is a phenolate oxygen-bridged dinucler copper(II) complex, which is similar to the dinuclear cop-per(II) complex with the ligand 2-(cyclohexyliminome-thyl)phenol . The coordination around each Cu atom in complex II is distorted square pyramidal. The equatorial plane ofeach square pyramid is defined by two phenolate oxygen and two imine nitrogen atoms from two L2 ligands. The apical position of each square pyramid i
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