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SYNTHESIS, CHARACTERIZATION, AND STRUCTURES OF TWO NEW TETRANUCLEAR COPPER COMPLEXES WITH AZIDO/DICYANAMIDE BRIDGES CONTAINING CHIRAL SCHIFF BASE LIGAND
© 2015 Z. Zhou1, X. K. Hou2, C. C. Xue2, and Z. X. Wang2, *
department of Chemistry, College of Science, South Agricultural University, Guangzhou, 510642 P.R. China 2Department of Chemistry, College of Science, Shanghai University, Shanghai, 200444 P.R. China
*E-mail: zxwang@shu.edu.cn Received August 8, 2014
Two new copper complexes [Cu4(^-L)2(^i i-N3)2(N3)2] (I) and [Cu4(^-L)2(^i 5-Dca)2(Dca)2] (II) (H2L = = (1R,3S)-N',N"-£is[5-methoxysalicylidene]-1,3-diamino-1,2,2-trimethylcyclopentane, Dca = dicyan-amide ions) were synthesized and structurally characterized by elemental analyses, IR spectroscopy and single-crystal X-ray diffraction (CIF files CCDC nos. 1013673 (I), 1013672 (II)). The two complexes crystallize in monoclinic P21/c and triclinic P1 space group, respectively. Both the complexes consist of two crys-tallographically independent copper ions connected by a double phenoxo bridges, which are further linked to the other symmetry-related half of the molecule by two end-on azido bridges or 5-dca groups.
DOI: 10.7868/S0132344X1503010X
INTRODUCTION
Chiral Schiff base ligands, obtained by condensing between a number of chiral amines and aldehydes or ketones, are a very important class of ligands to construct molecule materials with various novel structures and interesting properties [1—3]. In their family, tet-radentate Schiff-base ligands containing N, O donors have been widely utilized to form polynuclear complexes with interesting structures [4—6]. Camphoric diamine is a very useful material to construct chiral compounds [7]. Chiral Schiff base ligand condensation of camphoric diamine with a variety of aldehydes is also exploited to synthesize functional molecular materials [8]. Recently, we prepared a series of chiral Schiff base ligands based on camphoric diamine and used azide or dicyanamide ions as a small conjugated ligand bridging to connect partially blocked dinuclear copper to form a series of compounds exhibiting 0D [9], 1D and 2D structures [10]. To continue our previous work, we synthesized a new chiral Schiff base ligand (1R,3S)-N',N"-Ws,[5-methoxysahcylidene]-1,3-diamino-1,2,2-trimethylcyclopentane (H2L) obtained by reaction with 5-methoxysalicylaldehyde and camphoric diamine and harvested two new tetranucle-ar copper complexes with doubly phenoxo and end-on azido or dicyanamide bridges. Herein, we describe the details of syntheses, characterization and crystal structures of the complexes, [Cu4(^-L)2(^11-N3)2(N3)2] (I) and [Cu4(|i-L)2(|i1,5-Dca)2(Dca)2(CH3OH)2] (II), where Dca are dicyanamide ions.
OH
HO
(H2L)
EXPERIMENTAL
Materials and methods. All chemicals used during the course of this work were of reagent grade and used as received from commercial sources without further purification. Schiff base ligands H2L was prepared according to the literature methods [11, 12]. Elemental analyses for carbon, hydrogen, and nitrogen were carried out with a Vario EL III elemental analyzer. Infrared spectra were recorded with a Nicolet A370 FT-IR spectrometer using KBr pellets in the 4000—400 cm-1 region.
Caution! Azide derivatives are potentially explosive, only a small amount of material should be prepared, and it should be handled with proper care.
Synthesis of complex I. This complex was prepared by a similar procedure to that described in reference [9] except that H2L was used. Due to the low yield, only several crystals were picked up by handy to do Infrared spectra.
IR (KBr; v, cm-1): 2955, 2068, 2039, 1604, 1482, 1288, 815.
3
Table 1. Crystallographic data and structural refinement details of complexes I and II
Parameter Value
I II
Empirical formula C48H56N16O8Cu4 C58H62N16O10Cu4
Formula weight 1239.25 1397.40
Crystal system Monoclinic Triclinic
Space group P21/C PI
a, A 12.1061(14) 9.956(3)
b, A 14.6540(17) 11.740(3)
c, A 16.5782(15) 14.769(4)
a, deg 90 90.078(5)
ß, deg 115.998(6) 94.292(5)
Y, deg 90 115.015(4)
V, A3 2643.4(5) 1558.9(7)
Z 2 1
Pcalcd g/cm3 1.557 1.491
p., mm-1 1.655 1.415
/(000) 1272 720
Reflections collected/unique 18158/4622 8722/5495
Rint 0.0373 0.0404
Limiting indices -14 < h < 14, -17 < k < 17, - 19 < l < 19 -11 < h < 11, -14 < k < 14, -17 < l < 17
Data/restraints/parameters 4622/70/343 5495/10/403
GOOF (all reflections) 1.029 1.004
R1, wR2 (I >2a(T)) 0.0877, 0.2283 0.0774, 0.2093
R1, wR2 (all data) 0.1044, 0.2378 0.1062, 0.2289
Largest diff. peak/hole, e A-3 1.041 and -0.695 1.460 and -0.764
Synthesis of complex II. Solid of CuCl2 • 2H2O (34.6 mg, 0.200 mmol) was added to 5 mL of a meth-anolic solution dissolved H2L (18.4 mg, 0.050 mmol) with stirring for 10 min. Then Na(Dca) (28.6 mg, 0.300 mmol) dissolved in 5 mL of CH3OH was added slowly to the above mixture, and the resulting brown solution was stirred for 5 min followed by filtration. The filtrate was left at room temperature, and dark crystals appeared after 3 days. They were collected by filtration, washed with methanol (the yeld was 42% based on Cu) and a well-shaped crystal of II was selected for X-ray single-crystal diffraction analysis.
For C58H62Ni6OieCu4
anal. calcd., %: C, 49.78; H, 4.43; N, 16.02; Found, %: C, 49.97; H, 4.42; N, 16.15.
IR (KBr; v, cm-1): 2964, 2306, 2239, 2168, 1607, 810.
X-ray crystallography. Crystallographic data of complexes I and II were collected using a Bruker SMART APEXII CCD diffractometer operating at room temperature. Intensities were collected with graphite monochromatized MoZa radiation (X = 0.71073 A), using the 9 and ® scan technique. Data reduction was made with the Bruker SAINT package [13]. Absorption correction was performed using the SADABS program. The structure was solved by direct methods and refined on F2 by full-matrix least-squares using SHELXL-2000 with anisotropic displacement parameters for all non-hydrogen atoms [14]. H atoms were introduced in calculations using the riding model. All computations were carried out using the SHELXTL-2000 program package [15]. X-ray crystal-lographic data and refinement details are summarized
Table 2. Selected bond lengths (À) and bond angles (deg) for complexes I and II*
Bond d, Â Bond d, Â
Cu(1) - N(1) Cu(1)—N(2) Cu(1)— O(1) Cu(1)— O(2) Cu(1)—N(1) Cu(1)—N(2) Cu(1)— O(1) Cu(1)— O(2) Cu(1)— O(3) 1.929(10) 1.978(7) 1.911(5) 1.931(5) I 1.966(5) 1.966(5) 1.950(4) 1.950(4) 2.354(5) I Cu(2)— O(1) Cu(2)—O(2) Cu(2)—N(3) Cu(2)—N(3)#1 I Cu(2)— O(1) Cu(2)—O(2) Cu(2)—N(3) Cu(2)—N(6) Cu(2)—N(8)#1 2.284(5) 2.006(5) 1.992(6) 1.977(7) 2.003(4) 1.986(4) 1.979(7) 2.228(6) 1.992(6)
Angle ro, deg Angle ro, deg
Cu(1)O(1)Cu(2) Cu(2)N(3)Cu(2)#! O(1)Cu(1)N(1) O(1)Cu(1)N(2) O(2)Cu(1)N(2) N(6)Cu(2)N(3) N(6)Cu(2)O(2) N(3)Cu(2)O(2) N(3)#1Cu(2)O(1) O(2)Cu(2)O(1) Cu(1)O(1)Cu(2) O(1)Cu(1)O(2) O(2)Cu(1)N(1) O(2)Cu(1)N(2) O(1)Cu(1)O(3) N(1)Cu(1)O(3) N(3)Cu(2)O(2) O(2)Cu(2)N(8)#! O(2)Cu(2)O(1) N(3)Cu(2)N(6) N(8)#1Cu(2)N(6) 98.5(2) 103.4(3) 93.1(3) 164.6(3) 93.2(3) 94.7(3) 93.4(3) 169.9(2) 103.7(3) 70.2(2) I 102.35(19) 76.20(17) 166.5(2) 91.99(18) 90.7(2) 97.2(3) 150.1(3) 93.9(2) 74.21(16) 100.7(3) 89.7(2) I Cu(1)O(2)Cu(2) O(1)Cu(1)O(2) N(1)Cu(1)O(2) N(1)Cu(1)N(2) N(6)Cu(2)N(3)#1 N(3^)Cu(2)N(3) N(3^)Cu(2)O(2) N(6)Cu(2)O(1) N(3)Cu(2)O(1) I Cu(1)O(2)Cu(2) O(1)Cu(1)N(1) O(1)Cu(1)N(2) N(1)Cu(1)N(2) O(2)Cu(1)O(3) N(2)Cu(1)O(3) N(3)Cu(2)N(8)#1 N(3)Cu(2)O(1) N(8)#1Cu(2)O(1) O(2)Cu(2)N(6) O(1)Cu(2)N(6) 108.1(3) 80.3(2) 165.7(3) 96.2(3) 160.5(3) 76.6(3) 93.8(2) 95.8(3) 115.0(3) 102.95(18) 93.0(2) 164.4(2) 97.1(2) 90.99(19) 99.8(2) 93.4(3) 91.7(2) 163.5(2) 108.3(2) 104.7(2)
* Symmetry transformations used to generate equivalent atoms: #1 — x, — y + 1, — z + 1 (I); #1 — x + 1, —y + 2, — z (II).
(a)
Fig. 1. Molecular structures of I (a) and II (b). All hydrogen atoms are been omitted for clarity.
in Table 1. The selected bond lengths and angles for the two complexes are given in Table 2.
Crystallographic data for the structures has been deposited with the Cambridge Crystallographic Data Centre (CCDC nos. 1013673 (I), 1013672 (II); www.ccdc.cam.ac.uk/data_request/cif).
RESULTS AND DISCUSSION
The infrared spectra exhibit characteristic vibration bands of the chiral Schiff base ligand in both complexes. The bands presenting at 2955 and 1604 cm-1 in I, 2964 and 1607 cm-1 in II are designated to the stretching vibrations of the methyl groups and the v(C=N) stretching frequencies, respectively. In addition, absorption of 815 and 810 cm-1 is assigned to the 6(CH) bending vibrations ofphenyl rings for I and II. Meanwhile, the spectra of I show strong sharp double characteristic absorptions of the v(N=N) at 2068 and 2039 cm-1, together with the presence of a band at about 1288 cm-1 indicating the presence of both EO bridging and terminal azido ligands [16, 17], which are in agreement with
the crystal structure. While the appearance of three sharp and strong stretching frequencies in the 23102160 cm-1 region confirms the presence of dicyana-mide anions in complex II. The peaks at 2306, 2239 and 2168 cm-1 are characteristic for expected absorption of asymmetric and symmetric vibrations of the v(C=N) groups [18, 19].
The single crystal X-ray structural analysis shows that both of the two complexes are centrosymmetrical tetranuclear structures. As showing in Fig. 1, both the complexes consist of two crystallographically independent copper ions connected by a double phenoxo bridges, which are further linked to the other symmetry-related half of the molecule by two EO azido bridges or ^15-Dca ions. This array of the copper ions leads to very similar to the tetranuclear units [9, 20-22]. In complex I, the terminal copper Cu(1) ions present a slightly distorted square plane geometry which is coordinated to two phenoxo oxygen atoms, two imine nitrogen atoms from one ligand. While the terminal Cu(1) ions in II show
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