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HETEROMETALLIC COMPLEXES OF MACROCYCLIC OXAMIDE WITH POLYCARBOXYLATES: SYNTHESES, CRYSTAL STRUCTURES,
AND MAGNETIC PROPERTIES © 2014 S. Y. Liu1 2, Y. Q. Sun1, 2 *, X. X. Liu1 2, and J. Wang1, 2
1Tianjin Key Laboratory of Structure and Performance for Functional Molecule, College of Chemistry, Tianjin Normal University, Tianjin, 300387P.R. China 2Key Laboratory of Inorganic-Organic Hybrid Functional Material Chemistry (Tianjin Normal University),
Ministry of Education *E-mail: hxxysyq@mail.tjnu.edu.cn Received Octoder 16, 2013
Three complexes with the formula [Co(Ip)(CuL)(H2O)2] ■ H2O (I), [Co(Ip)(NiL)(H2O)2] ■ H2O (II), [Co(CuL)2(Hbtc)(H2O)](III), (H2Ip = m-isophthalic acid; H2L = 2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-dien; H3Btc = 1,3,5-benzenetricarboxylic acid) were synthesized and structurally characterized by elemental analysis, IR and UV spectroscopy. Single-crystal X-ray analyses reveal that the complexes I and II contain neutral heterometallic binuclear CoM (for I and II, M = Cu, Ni, respectively) moieties, and complex III contains discrete neutral trinuclear CoCu2 moieties. The structures of I—III consist of two-dimensional supramolecular architecture formed by strong O—H---O intermolecular hydrogen bonds. Furthermore, the magnetic properties of complex I were investigated and discussed in detail.
DOI: 10.7868/S0132344X14050065
INSTRODUCTION
Substantial interest has been devoted to the development of synthesis, design and characterization of supramolecular complexes over the past decade [1—3]. Many self-assembly supramolecular networks exhibit novel structural topologies and interesting electrical, magnetic, optical, catalytic, or biological properties [4—6]. Especially, the synthesis of heterometallic (3d— 3d and 3d—4/) supramolecular complexes is one of current focus, because the combination of two dissimilar metal centers can lead to fascinating structures and new topological features with the promise for interesting magnetic, magneto-optical and optoelectronic properties [7—13]. Up to date, there are two main synthetic approaches to obtain the heterometallic su-pramolecular complexes. One is one-pot synthetic approach, adopting this synthetic approach, the ligand design strategy is very important in the construction of unusual heterometallic coordination frameworks [14— 16]. However, the design and synthesis of heterometallic complexes are still a challenge to chemists, especially in the cases of 3d—3d heterometallic systems, because one-pot synthetic approach can lead to a statistical mixture of homo- and heterometallic architectures [17]. The other synthetic approach is given by the concept of 'complex ligand', i.e., utilizing a metal complex as ligand to coordinate an appropriate additional metal ion [18]. In recent years, this field has been extended by using the macrocyclic analogues of
the oxamides [19, 20]. Noncyclic oxamides may adopt a cis or trans conformation on coordination, and this flexibility restricts the control over the type of the complex formed [11]. The macrocyclic oxamides allow the synthesis of heterometallic systems in a more controlled fashion, and it has been found that theoxa-mide group serves as a pathway through which electron spin interaction takes place [21].
On the other hand, aromatic multicarboxylic acid not only possesses versatile coordination modes and easily links metal ion cores to form polymeric structures, but also has the ability to construct a novel metal-organic supramolecular network through hydrogen bonds as well as n—n stacking [22, 23]. However, systematic studies on these kinds of ligands in the coordination chemistry are still an active field of research. In our continuing efforts to investigate the synthesis and properties of heterometallic polynuclear complexes, in this paper, we report that the macrocyclic oxamido complex was used as ligand with co-ligand H2Ip, H3Btc to synthesize two binuclear ConMn (M = Cu, Ni) and one trinuclear CoIICuII2 supramolecular complexes [Co(Ip)(CuL)(H2O)2] • H2O (I), [Co(Ip)(NiL)(H2O)2] • H2O (II), [Co(CuL)2(Hbtc)(H2O)] (III) (H2Ip = m-isophthalic acid; H2L = 2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tet-raazacyclo-pentadeca-7,13-dien; H3Btc = 1,3,5-ben-zenetricarboxylic acid). Furthermore, the magnetic
properties of complex cussed in detail.
I were investigated and dis-
gradually cooled to room temperature for 36 h, and brown block crystals of III were obtained.
EXPERIMENTAL
All the starting reagents were of A.R. grade and were used as purchased. The complex ligand ML was prepared as described elsewhere [24]. Analyses of C, H, and N were determined on a PerkinElmer 240 Elemental analyzer. IR spectrum was recorded as KBr discs on a Shimadzu IR-408 infrared spectrophotometer in the 4000—600 cm-1 range. Electronic spectra for solid samples were recorded on a Shimadzu UV-2101 PC scanning spectrophotometer. Variable-temperature magnetic susceptibilities of single crystals were measured on an MPMS-7 SQUID magnetometer. Dia-magnetic corrections were made with Pascal's constants for all the constituent atoms [25].
Synthesis of complex I. A mixture of Co(Ac)2 • 6H2O (0.05 mmol, 12.5 mg), H2Ip (0.05 mmol, 8.3 mg), CuL (0.025 mmol, 10.2 mg), H2O (10 mL), and CH3OH (2 mL) was stired for 20 min at room temperature, and the pH value of the solution was adjusted to about 7-8 with triethylamine. Then, the mixture was transferred to a 18 mL Teflon-lined reactor, which was heated to 140°C for 60 h. Last the reaction system was gradually cooled to room temperature for 36 h, and brown block crystals of I were obtained.
For C27H26N4O9CoCu
anal. calcd, %: C, 48.14; H, 3.86; N, 8.32. Found, %: C, 48.16; H, 3.83; N, 8.35.
IR bands (v, cm-1): 1641 vs(COO), 1610 v(C=O),
1564 v(C=N).
Synthesis of complex II. The synthetic procedure was similar to that described for the preparation of I except using NiL (0.03 mmol, 11.8 mg) instead of CuL. The red block crystals of II were obtained.
For C27H26N4O9CoNi
anal. calcd, %: C, 48.49; H, 3.89; N, 8.38. Found, %: C, 48.36; H, 3.86; N, 8.35.
IR bands (v, cm-1): 1640 vs(COO), 1612 v(C=O),
1565 v(C=N).
Synthesis of complex III. A mixture ofCo(Ac)2 • 6H2O (0.05 mmol, 12.5 mg), H3Btc (0.05 mmol, 10.5 mg), CuL (0.025 mmol, 10.2 mg), H2O (10 mL), and CH3OH (4 mL) was stired for 20 min at room temperature, and the pH value of the solution was adjusted to about 6-7 with triethylamine. Then, the mixture was transferred to a 18 mL Teflon-lined reactor, which was heated to 140°C for 60 h. Last the reaction system was
For C47H38N8O11CoCu2
anal. calcd, %: Found, %:
C, 52.36; C, 52.37;
H, 3.52; N, 10.38. H, 3.56; N, 10.40.
IR bands (v, cm-1): 1672 vas(COOH), 1625 vs(COO), 1609 v(C=O), 1556 v(C=N).
X-ray crystallography. The data were collected on a Bruker Smart-1000-CCD area detector, all using gra-phite-monchromated Mo^a radiation (X = 0.71073 A). The structures were solved by direct method and subsequent Fourier difference techniques and refined using full-matrix least-squares procedure on F2 with anisotropic thermal parameters for all non-hydrogen atoms (SHELXS-97 and SHELXL-97). Hydrogen atoms were added geometrically and refined with riding model position parameters and fixed isotropic thermal parameters. Crystal data collection and refinement parameters are given in Table 1, and selected bond lengths and angles for I-III are listed in Table 2. Crystallographic data (excluding structure factors) for structures I-III have been deposited with the Cambridge Crystallographic Data Centre (nos. 895937895939; deposit@ccdc.cam.ac.uk or http://www.ccdc. cam.ac.uk).
RESULTS AND DISCUSSION
By using m-isophthalic acid, 1,3,5-benzenetricar-boxylic acid and macrocyclic oxamido mixed ligands as the metal linker, three new complexes have been synthesized under hydrothermal conditions. During the course of the reacations, a series of experiments were performed by varying the pH value of the reaction system in the range of 4-9. The results show that compound I and II were obtained at relatively lower pH (6-7), whereas compound III was obtained at relatively higher pH (7-8). In order to explore the effect of the other reaction parameters in the preparing complexes I—III, a large number of experiments were also carried out via varying the reaction temperature (100-180°C) and time (3 to 10 days). And the results show that the single-crystal products suitable for X-ray analysis can be readily cbtained at 140°C for 2.5 days.
The IR spectra of the three complexes clearly show the existence of the m-isophthalic acid, 1,3,5-benze-netricarboxylic acid and macrocyclic oxamido moieties in the molecules, respectively. The IR spectra of I-III exhibit broad absorption bands in the range 3260-3450 cm-1, demonstrating the existence of water, and the spectra exhibit strong absorption bands in the region 1612-1609 and 1565-1556 cm-1 due to the v(C=O) and the v(C=N) vibrations of oxamide group, respectively. The IR spectrum of the III shows one band around 1672 cm-1 which is characteristic of
Table 1. Crystal data and structure refinement for complexes I—III
Parameter Value
I II III
Fw 672.99 668.16 1076.86
Crystal size, mm 0.38 x 0.32 x 0.30 0.32 x 0.28 x 0.22 0.22 x 0.16 x 0.15
Crystal system Monoclinic Monoclinic Monoclinic
Space group P2x/c P21/c P2x/n
a, A 12.9063(6) 12.8429(6) 11.2985(9)
b, A 11.6766(6) 11.6726(6) 23.0322(18)
c, A 17.8857(9) 17.8902(9) 17.0688(13)
P, deg 92.4040(10) 92.1740(10) 100.8210
V, A3 2693.0(2) 2680.0(2) 4362.8(6)
Z 4 4 4
Pcaled g/cm3 1.660 1.656 1.639
mm-1 1.469 1.385 1.416
F(000) 1376 1372 2196
Rint 0.0152 0.0171 0.0499
Goodness-F 2 1.040 1.032 1.034
Ri* (I> 2a(I)) 0.0244 0.0241 0.0358
wR2* (all data) 0.0701 0.0650 0.0841
* R1 = ZilFoi- iiçii/Ejioi; wR2 = {Z[w(Fo - Fc2)2]/S[w(F0)2]}1/2.
the protonation of the carboxyl groups. While the IR spectra of those compounds sh
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