КООРДИНАЦИОННАЯ ХИМИЯ, 2011, том 37, № 5, с. 375-379
УДК 541.49
A PROPANEDIAMINE-BRIDGED DINUCLEAR IRON(III) COMPLEX: SYNTHESIS, X-RAY ANALYSES, SPECTRAL STUDIES, AND MAGNETIC PROPERTIES
© 2011 X. Feng1, *, S. H. Li1, Q. Q. Sun1, P. P. Lei1, and C. Z. Xie2
1College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471022, P.R. China 2 School of Pharmaceutical Sciences, Tianjin Medical University, Tianjin 300070, P.R. China
*E-mail: fengx@lynu.edu.cn Received July 12, 2010
A new propylenediamine-bridged diunclear complex formulated as [Fe2(Salpn)3] (I) (pn = 1,2-propylenedi-amine, H2Salpn = N,N'-fc(salicylaldehyde)propylenediamine Schiff base) has been prepared from the template synthesis by the reaction of 1,2-propylenediamine with salicylaldehyde in the presence of the iron(III) salt. The metal centers adopt a slightly distorted octahedral geometry, and the Salpn ligands act in both bridging and chelating modes to form a dinuclear complex with the six-membered chelate rings. The magnetic susceptibility investigation for I indicates the presence of very weak antiferromagnetic coupling between the Fe3+ cations through the propylenediamine bridge.
INTRODUCTION
During the past two decades, transition metals complexes with tetradentate Schif base ligands have attracted more attention [1, 2] and have been widely utilized to form supramolecular complexes with interesting structures, as well as their intriguing properties and potential applications in magnetostructural correlations in molecular systems and materials [3]. The late transition metals are essential catalysts involved in many electron transport systems. For instance, iron is the principal electron carrier in biological redox reactions [4]. Meanwhile, the use of the salicylaldehyde Schiff base ligand in catalytic reactions has been received increasing interest due to the ligand frameworks, such as the Salpn Schiff base ligand, which can easily be sterically and electronically modified in many newly discovered processes [5, 6]. However, the iron complex with the Salpn ligands acting in both bridging and chelating modes to form the chelate rings is rarely observed. In fact, dinuclear magnetic materials are becoming a very fruitful area of investigation in intensely studied areas of inorganic chemistry, ranging from medicine to materials science owing to their potential to afford a large variety of interesting structural types with unusual magnetic properties [7, 8], and it can provide the bridge mode, thus estimating in advance the coupling between the central ions in analogous systems. In order to further study of the coordination behavior and the role ofthe late transition metal cation in the self-assembly processes at presence of the Salpn ligand and to gain further insight into the magnetic interaction and structural properties of these systems, in the present work, a new dinuclear complex [Fe2(Salpn)3] (I) has been synthesized from the actual components in the rational stoichiometric scale and has been characterized systematically.
EXPERIMENTAL
Materials and physical measurements. All chemicals were commercially purchased and used without further purification. Elemental analyses (C, H, and N) were performed on a PerkinElmer 2400 element analyzer. IR spectra were recorded in the range 400—4000 cm-1 on a VECTOR-22 spectrometer using KBr discs. Magnetic data were obtained with a Quantum Design MPMS SQUID 5S susceptometer at an applied field of10000 G using crystalline samples of I in a temperature range of 2-300 K. The magnetic susceptibilities of the complex were corrected by Pascal's constant and diamagnetism of the holder.
Synthesis of complex I. Fe2(SO4)3 • 6H2O (0.281 g, 0.5 mmol) and NaN(CN)2 (0.090 g, 1 mmol) were re-fluxed in anhydrous methanol (10 ml) for 15 min. Then they were added to 20 ml of a methanol solution offreshly distilled salicylaldehyde (0.366 g, 3.0 mmol) and 1,2-propylenediamine (0.112 g, 1.5 mmol) simultaneously. The mixture was refluxed for 3.5 h and, after cooling to the room temperature, was filtered. The resulting clear solution was diffused with diethyl ether vapor at room temperature for two weeks. Brown crystals were formed, collected by filtration, and dried in air. The yield was 198 mg (41%).
For C51H48N6O6Fe2
anal. calcd., %: C, 55.66; H, 4.15; N, 12.62. Found, %: C, 55.87; H, 4. 26; N, 12.71.
IR (KBr disc; v, cm-1): 3413 s, 3157 s, 2935 m, 2287 s, 2153 s, 1663 s, 1604 s, 1498 s, 1338 s, 1203 m, 1063 s, 902 m, 801 s, and 602 s.
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Table 1. Crystal data and refinement details for complex I
Parameter Value
Formula weight 952.65
Temperature 296(2)
Crystal system Monoclinic
Space group P2i/c
Unit cell dimensions:
a, A 10.995(3)
b, A l9.8ll(6)
c, A 23.072(7)
a, deg 90
P, deg 103.367(4)
Y, deg 90
V, A3 4889(2)
Z 4
-3 Pcalcd g cm 1.294
F(000) 1984
Absorption coefficient, mm-1 0.647
9 Range for data collection, deg 2.25 to 25.50
Limiting indice rangs -13 < h < 13
-24 < k < 24
-26 < l < 27
Max and min transmissions 0.9092 and 0.8197
Data/restraints/parameters 9081/0/586
GOOF 1.032
R-factor (I > 2ct(I)) Rl = 0.0482, wR2 = 0.0930
R-factor (all data) Rl = 0.0884, wR2 = 0.1036
r = №| - |fc ii/zfo |], rw = ew [ |f 0 - f 2|2/sw (|fw|2)2]1/2.
X-ray structure determination. Single-crystal diffraction data of I were collected on a Bruker SMART APEX CCD diffractometer with graphite-monochromated Mo^a radiation (k = 0.71073 A). A total of35440 reflections were collected, of which 9081 were independent (Rint = 0.0747), and 5483 with I > 2g(T) were observed and used for structure refinements. The structures were solved using direct methods and successive Fourier difference synthesis (SHELXS-97) [9] and refined using the full-matrix least-squares method on F2 with anisotropic thermal parameters for all non-hydrogen atoms (SHELXL-97) [10]. All absorption corrections were performed using the SADABS program. The hydrogen atoms of organic ligands were placed in calculated positions and refined using a riding on attached atoms with isotropic thermal parameters 1.2 times those of their carrier atoms. Corrections for Lp factors were applied and all non-hydrogen atoms were refined with anisotropic thermal parameters. The final R = 0.0884, wR = 0.1036, w = l/[a2(Fo2) +
+ (0.0313P)2 + 0.000P], where P = (Fo2 + 2Fc2 )/3), ^ = = 1.032, (A/a)max = 0.001. Crystallographic and experimental details are summarized in Table l. Selected bond lengths and bond angles are listed in Table 2.
Supplementary material has been deposited with the Cambridge Crystallographic Data Centre (no. 777145; deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).
RESULTS AND DISCUSSION
The FT-IR spectrum of compound I exhibits a strong and broad absorption centered at 3418 cm-1, which can be ascribed to the presence of N-H stretching vibration. The bands of medium intensity at 3064, 2940, and 2840 cm-1 for I are assigned to the C-H stretching vibrations of the aromatic rings, and propane group, respectively. Characteristic bands of carbonyl groups at 1663 cm-1 is also found, and it shows a characteristic strong band of v(C=N) at 1604 cm-1 type located mainly on the C=N group, which was shifted toward a lower frequency than that of the free Schiff base ligand [ll]. The bands in the 1600-1520 cm-1 region were assigned to v(C=C) of the phenyl ring, and the broad and intense spectra at 1613.5 and 1417.3 cm-1 are attributed to the O-C-O stretching vibration [12]. The electronic spectrum of complex I in DMF (Fig. l) displays a very weak d-d band at 350 nm together with the intense band at 210 nm followed by a shoulder at 226 nm and another strong peak at the 274 nm are observed. These absorptions are likely to be due to intraligand n ^ n* transitions and the ligand to metal charge-transfer transition, respectively [13], as found for other six-coordinated metal complexes involving ¿¿s-salicylaldehyde Schiff base [14].
The perspective view of I with the atom labeling scheme is illustrated in Fig. 2. The symmetric unit of the crystal structure consists of two independent Fe3+ cations, and three deprotonated Salpn ligands. The dicyan-amide anion is absent in the final molecule, which is also confirmed by the IR spectrum and elemental analysis. The Salpn Schiff base acts as a tetradentate ligand showing a chelate and bridge coordination modes, which is also observed in the analogous binary complex [15, 16]. Firstly, the two Salpn ligands doubly chelate the Fe3+ ion using the phenol-hydroxyl oxygen atoms and the terminal nitrogen atoms of the l,2-propylenediamine moiety. The coordination polyhedron around the Fe3+ ion can be visualized as a slightly distorted octahedron with a FeO3N3 coordination mode. The bond lengths of Fe(III)-O varied from 1.924(2) to 1.967(2) A and the Fe-N bond lengths range from 1.977(3) to 1.990(2) A, which are close to those reported in the transition metal complexes containing Salpn ligands [17]. The equatorial sites of the octahedron are occupied by the N3O donor atoms in which two oxygen atoms are from the Salpn ligand and the distorted octahedronal coordination sphere about Fe(III) is apically completed by two nitrogen atoms N(4) and N(5) from the adjacent Salpn moi-
A PROPANEDIAMINE-BRIDGED DINUCLEAR IRON(III) COMPLEX 377
Table 2. Selected bond distances and bond angles for complex I
Bond d, Â Bond d, Â Bond d, Â
Fe(1)—O(1) 1.936(2) Fe(1)—N(1) 2.171(3) Fe(2)—O(6) 1.953(2)
Fe(1)—O(2) 1.938(2) Fe(1)—N(3) 2.182(2) Fe(2)—N(5) 2.158(3)
Fe(1)—O(3) 1.967(2) Fe(2)—O(5) 1.924(2) Fe(2)—N(6) 2.174(3)
Fe(1)—N(2) 2.156(3) Fe(2)—O(4) 1.953(2) Fe(2)-N(4) 2.200(2)
Angle ю, deg Angle ю, deg Angle ю, deg
O(1)Fe(1)O(2) 90.07(9) O(1)Fe(1)N(3) 96.97(9) O(6)Fe(2)N(5) 100.22(9)
O(1)Fe(1)O(3) 96.85(9) O(2)Fe(1)N(3) 87.76(9) O(5)Fe(2)N(6) 164.49(9)
O(2)Fe(1)O(3) 170.28(8) O(3)Fe(1)N(3) 84.64(9) O(4)Fe(2)N(6) 89.39(10)
O(1)Fe(1)N(2) 163.53(9) N(2)Fe(1)N(3) 98.34(9) O(6)Fe(2)N(6)
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