научная статья по теме A NEW 2D MN(II) COORDINATION POLYMER CONSTRUCTED FROM CARBOXYLATE AND N-DONOR COLIGAND: SYNTHESIS, STRUCTURE, AND MAGNETISM Химия

Текст научной статьи на тему «A NEW 2D MN(II) COORDINATION POLYMER CONSTRUCTED FROM CARBOXYLATE AND N-DONOR COLIGAND: SYNTHESIS, STRUCTURE, AND MAGNETISM»

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A NEW 2D Mn(II) COORDINATION POLYMER CONSTRUCTED FROM CARBOXYLATE AND N-DONOR COLIGAND: SYNTHESIS, STRUCTURE, AND MAGNETISM

© 2014 J. Wang1, 2, 3, *, L. Lu1, 2, W. P. Wu1, 2, L. K. Zou1, 2, and B. Xie1, 2

1Institute of Functionalized Materials, Sichuan University of Science & Engineering, Zigong, 643000 P.R. China 2School of Chemistry and Pharmaceutical Engineering, Sichuan University of Science & Engineering,

Zigong, 643000 P.R. China 3Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, Shanxi Key Laboratory of Physico-Inorganic Chemistry, College of Chemistry and Materials Science, Northwest University, Xi'an, 710069 P.R. China *E-mail: scwangjun2011@126.com Received October 29, 2012

A new complexes, namely, {[Mn2(L)2(Bipy)2] • H2O}n (I) (H2L = diphenic acid, Bipy = 4,4'-bipyridine) has been synthesized and structurally characterized by single-crystal diffraction analysis. In I, the two syn, anti-carboxylate groups in L bridge Mn(II) forming a one-dimensional chain, which is further connected by Bipy into 2D double layer. Magnetic study reveals the overall antiferromagnetic interaction between neighboring Mn2+ ions in compound I.

DOI: 10.7868/S0132344X14030098

INTRODUCTION

Over past decades, the field of crystal engineering has achieved significant success in developing a variety of metal-organic frameworks [1—3]. The interest arises not only from their versatile fascinating architectures but also from their promising applications [4]. Many works have been devoted to the selection or design of suitable ligands containing certain features. Among the reported studies, organic ligands with car-boxylate groups are of especial interest because they can adopt a variety of coordination modes and result in diverse multidimensional frameworks [5—11]. H2L is utilized as multifunctional ligand owing to their high coordination numbers and modulating coordination environments [12]. Two ionizable hydrogen atoms can be partially or completely deprotonated to generate L anion. Moreover, H2L has a C—C single bond between two phenyl rings to form skew coordination orientation of the carboxylate groups [13, 14]. To date, some Cu/Cd coordination polymers with diphenic acid ligand have been reported [15]. However, a few Mn(III) complexes of diphenic acid ligand have been studied.

On the other hand, 4,4'-bipyridine (Bipy) or a combination with other ligands can be used for the construction of intriguing supramolecular motifs using covalent coordination and hydrogen bonds to give one-dimensional structures and higher-dimensional coordination polymers [16]. With this background in

mind, we chose diphenic acid (H2L) as a organic ligand to react with the Mn2+ ion in the presence of rigid N-do-nor (Bipy). A new polymer {[Mn2(L)2(Bipy)2] • ^O}n (I) was obtained under mild condition. In I, the two syn, anti-carboxylate groups in L bridge Mn(II) forming a one-dimensional chain, which is further connected by Bipy into 2D double layer. Magnetic study reveals the overall antiferromagnetic interaction between neighboring Mn2+ ions in compound I.

EXPERIMENTAL

Materials and physical measurements. All the reagents and solvents for synthesis and analysis were commercially available and used directly. Elemental analyses for carbon, hydrogen and nitrogen were performed on a Vario EL III elemental analyzer. The infrared spectra (4000—600 cm-1) were recorded by using KBr pellet on an AVATAR-370 (Nicolet) IR spectrometer. The crystal determination was performed on a Bruker SMART APEX II CCD diffractometer equipped with graphite-monochromatized MoKa radiation (X = 0.71073 A). TGA were carried out with a Metter-Toledo TA 50 in dry dinitrogen (60 mL min-1) at a heating rate of 5°C min-1. X-ray power diffraction (XRPD) data were recorded on a Rigaku RU200 diffractometer at 60 KV, 300 mA for CuKa radiation (X = = 1.5406 A), with a scan speed of 2°C/min and a step size of 0.02° in 29. Magnetic susceptibility data of

Table 1. Crystal data and structure refinement information Table 2. Selected bond distances (À) and angles (deg) of for compound I structure I

Parameter Value Bond d, Â Bond d, Â

Formula weight 920.67 Mn(1)-N(4) 2.316(7) Mn(1)-N(2) 2.320(7

Crystal system Orthorhombic Mn(1)-O(7) 2.179(7) Mn(1)-O(1) 2.141(8

Space group Pna21 Mn(1)-O(4) 2.154(7) Mn(1)-O(6) 2.184(8

a, A 17.791(7) Mn(2)-O(3) 2.151(7) Mn(2)-O(2) 2.165(7

b, A 23.255(9) Mn(2)-O(8) 2.189(8) Mn(2)-O(5) 2.193(7

c, A 9.833(4) Mn(2)-N(1) 2.311(6) Mn(2)-N(3) 2.313(7

V, A 3 4068(3) Angle ro, deg Angle ro, deg

Z 4 O(1)Mn(1)O(4) 88.4(2) O(4)Mn(1)O(6) 170.5(2

Pcalcd g/cm3 1.503 O(1)Mn(1)O(7) 179.1(3) O(4)Mn(1)O(7) 92.5(3

mm-1 0.687 O(1)Mn(1)O(6) 86.1(3) O(7)Mn(1)O(6) 93.1(2

F(000) 1888 O(1)Mn(1)N(4) 85.4(3) O(4)Mn(1)N(4) 90.8(3

9 Range, deg 2.28-26.30 O(7)Mn(1)N(4) 94.8(3) O(6)Mn(1)N(4) 81.1(3

Limiting indices h, k, l 0 < h < 18, 0 < k< 26, 0 < l< 8 O(1)Mn(1)N(2) 97.3(3) O(4)Mn(1)N(2) 86.2(3

Reflection collected 16952 O(7)Mn(1)N(2) 82.5(3) O(6)Mn(1)N(2) 102.1(3

Independent reflections (R^) 4904 (0.0848) N(4)Mn(1)N(2) 175.9(5) O(3)Mn(2)O(2) 97.7(2

Reflections with I > 2o(I) 3608 O(3)Mn(2)O(8) 91.5(3) O(2)Mn(2)O(8) 168.9(3

Number of parameters 575 O(3)Mn(2)O(5) 175.7(3) O(2)Mn(2)O(5) 84.6(3

Goodness-of-fit 1.041 O(8)Mn(2)O(5) 86.6(2) O(3)Mn(2)N(1) 81.7(3

R1, wR2 (I> 2ct(I))* 0.0701, 0.1617 O(2)Mn(2)N(1) 101.3(3) O(8)Mn(2)N(1) 86.0(3

R1, wR2 (all data)** 0.1065, 0.1915 O(5)Mn(2)N(1) 94.3(3) O(3)Mn(2)N(3) 98.3(3

APmin/APmax, e A~3 0.098 O(2)Mn(2)N(3) 83.9(3) O(8)Mn(2)N(3) 88.7(3

* R = S(F0 - Fc)/S(Fc), ** WR2 = {S[w(Fo - Fc2)2]/S(Fo2)2}1/2. O(5)Mn(2)N(3) 85.5(3) N(1)Mn(2)N(3) 174.7(4

powdered samples restrained in parafilm were measured on Oxford Maglab 2000 magnetic measurement system in the temperature range 300—1.8 K and at field of 1 KOe.

X-ray crystallography. Single crystal X-ray diffraction analyses of the compound was carried out on a Bruker SMART APEX II CCD diffractometer equipped with a graphite monochromated MoZ„ radiation (X = 0.71073 Â) by using scan technique at room temperature. The intensities were corrected for Lorentz and polarization effects as well as for empirical absorption based on multi-scan techniques; all structures were solved by direct methods and refined by full-matrix least-squares fitting on F2 by SHELX-97 [17]. Absorption corrections were applied by using multi-scan program SADABS. 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. The water hydrogen atoms were located from difference maps and refined with isotropic thermal parameters 1.5 times those of their carrier atoms. Table 1 shows crystallographic data of I. Selected bond distances and bond angles, parameters are listed in Table 2. Supplementary material for structure I has been deposited with the Cambridge Crystallographic Data Centre (no. 902918; depos-it@ccdc.cam.ac.uk or http:// www.ccdc.cam.ac.uk).

Synthesis of complex I. A mixture ofH2O (8 mL) and CH3OH (8 mL) solution containing H2L (0.1 mmol) and Bipy (0.1 mmol) was added Mn(OAc) • 2H2O (0.12 mmol) in water at 80°C. The pH of the resulting solution was adjusted to 7 using dilute NaOH (0.1 mol/L) and kept at room temperature to prepare compound I. From that solution, pale yellow crystals

KOOP^HH^HOHHAtf XHMHfl TOM 40 № 3 2014

suitable for X-ray measurements were obtained. The yield was 50%.

For C48H34N4O9Mn2 (M = 920.67) anal. calcd., %: C, 62.62; N, 6.09; H, 3.72. Found, %: C, 62.55; N, 6.21; H, 3.50.

IR (KBr; v, cm-1): 3421 v.s, 2992 m, 1618 v.s, 1502 m, 1488 v.s, 1255 v.s, 1185 s, 1012 m, 955 m, 887 m,752 m.

RESULTS AND DISCUSSION

The results of crystallographic analysis revealed that the asymmetric unit of complex I contains two crystallographically unique Mn(II) atom, two L and two Bipy ligands and one coordinative water molecule. As shown in Fig. 1, Mn(1) and Mn(2) have the same coordination geometries, which are completed by four oxygen atoms from four different L ligands (п1-П1-Ц2) and two N atoms from two Bipy molecules. The Mn-O and Mn-N distances are in the normal ranges (Table 2). The L has S- and ^-configuration enantiomorph (Fig. 2). In complex I, the L ligands just act as the ge-mel, connecting the dinuclear SBUs into a chain structure along the y axis (Fig. 2). The S- and ^-ligands are at each side of the chain. The phenyl rings of L are not coplanar, with the dihedral angle of 76.5°. The combination of these twisting allows L to link Mn(II) centers into a one-dimensional chain containing repeated eight-membered (-Mn-O—C—O—) rings (Fig. 2a) [13, 14]. The Mn-Mn separation in the rings is 5.069 A. There are no other short contacts and noteworthy weak interactions between the adjacent chains. Complex I is a two-dimensional layer structure consisting of one-dimensional L-Mn chains bridged by Bipy. There are two independent L ligands in asymmetric unit, both of them behave in a ¿¿s-bidentate fashion through two syn, anft'-carboxylate groups bridging three Mn(II) (Fig. 3).

As to FT-IR spectra, the compouns show a broad band centered around 3421 cm-1 attributable to the O-H stretching frequency of the water cluster. The O-H stretching vibration for Ic appears as a broad band centered around 3200 cm-1. Specifically, asymmetric stretching vibration v(COO-) and the symmetric stretching vibration v(COO-) are observed 1618 and 1488 cm-1, respectively. For that, the difference between the asymmetric and symmetric stretches, Avas(COO)-vs(COO), are on the order of 150 cm-1 indicating that carboxyl groups are coordinated to the metal in a bidentate modes [18], consistent with the observed X-ray crystal structure of I.

To study the stability of the polymer, thermogravi-metric analyses (TGA) of complex I was performed (Fig. 4). The TGA diagram of I shows tw

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