научная статья по теме THREE-DIMENSIONAL 3D–4F FRAMEWORKS CONSTRUCTED THROUGH SUBSTITUTED IMIDAZOLE–DICARBOXYLATE: SYNTHESIS, STRUCTURE, AND CHARACTERIZATION Химия

Текст научной статьи на тему «THREE-DIMENSIONAL 3D–4F FRAMEWORKS CONSTRUCTED THROUGH SUBSTITUTED IMIDAZOLE–DICARBOXYLATE: SYNTHESIS, STRUCTURE, AND CHARACTERIZATION»

УДК 541.49

THREE-DIMENSIONAL 3d-4f FRAMEWORKS CONSTRUCTED THROUGH SUBSTITUTED IMIDAZOLE—DICARBOXYLATE: SYNTHESIS, STRUCTURE, AND CHARACTERIZATION

© 2015 X. Feng1, *, C. L. Wang2, J. Zhao2, S. Y. Xie1, L. Y. Wing1*2, and S. W. Ng3

1College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang, 471022 P.R. China 2School of Life Science and Technology, Nanyang Normal University, Nanyang, 473601 P.R. China 3Department of Chemistry, University of Malaya, Kuala Lumpur, 50603, Malaysia * E-mail: fengx@lynu.edu.cn Received September 27, 2014

A heteronuclear metal organic framework containing erbium(III) and cobalt(II) ion based on a rigid ligand of substituted imidazoledicarboxylic acid has been synthesized and characterized by single-crystal X-ray diffraction analysis (CIF file CCDC no. 1019455). It's formula is [Er2Co2(^3-HMimda)2(^3-Mimda)2 ■ 4H2O]n ■ 2nH2O, (H3Mimda = 1-H-2-methyl-4,5-imidazole-dicarboxylic acid). The complex crystallizes in the monoclinic system. It possesses an extended grid-like porous structure constructed from corrugated shaped 2D layer. Direct current magnetic susceptibility measurements for indicated the depopulation of the Stark components at low temperature and possible very weak antiferromagnetic interactions within heteronuclear MOF.

DOI: 10.7868/S0132344X15040015

INTRODUCTION

In recent years, the rational design and construction of 3d-4f heterometallic coordination polymers have provoked the interest of chemists not only due to their potential applications in the fields of magnetism, luminescence, gas adsorption, and bimetallic catalysis, but also their fascinating architectures and arrays [1—3]. From the magnetic viewpoint, molecular magnetic materials based on transition metal ions, such as Co2+ have been extensively studied because the high spin ground state can be obtained from strong exchange interaction between 3d electrons. However, a high spin ground state and significant magneto anisotropy cannot be simultaneously achieved easily in 3d complexes due to the small spin-flip. The magnetic properties of large magnetic anisotropy of lanthanides continue to be an attractive research field because of their unique and intriguing properties and potential applications in molecular spintronics [4]. Couplings between the lanthanide and transition metallic ions f—d) are much stronger than f—f interactions, and the combination of such two kinds of spin carriers into a singular material may help to improve their magnetic properties in heterometallic materials [5]. However, no systematic investigation of zeolite-type functional materials containing lanthanide metal atoms series along with the transition metal atoms has been documented systematically [6], and Ln—Co heteronuclear metal organic frameworks (MOFs) with 3D framework structures have been seldom reported yet. This is due to the practically challenging syntheses of 3d—4f heterometallic MOFs. One of the difficulties is how to control the variable coordination environment of the lanthanide ions [7].

As continuation of our previous research [8], we have extended this idea by application of a simple H3Mimda ligand for construction of heterometallic MOFs [Er2Co2(|i3-HMimda)2(|i3-Mimda)2 ■ 4H2O]„ ■ 2«H2O (I) (H3Mimda = 1-#-2-methyl-4,5-imidazole-dicarboxylic acid) with novel architectures and interesting properties.

EXPERIMENTAL

Materials and physical measurements. Lanthanide oxides were purchased from Jinan Henghua Sci. & Tec. Co. Ltd. Erbium nitrate was prepared by the reaction of erbium oxides and nitric acid (11 mol/L). 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 using a VECTOR-22 spectrometer using KBr discs. Magnetic data were obtained using a Quantum Design MPMS SQUID 7S magnetometer at an applied field of 2000 Gs using multicrystalline samples in the temperature range of 1.8-300 K. The magnetic susceptibilities were corrected using Pascal's constant for all the constituent atoms and sample holders. Thermogravimet-ric (TG) and differential thermal analysis (DTA) experiments were performed using a TGA/NETZSCH STA449C instrument heated from 25-900°C (heating rate of 10°C/min in nitrogen stream). The powder X-ray diffraction (PXRD) patterns were measured have been performed at room temperature using a Bruker D8 advance powder diffractometer at 40 kV, 40 mA for CuKa radiation (X = 1.5418 A).

Synthesis of I. Cobalt nitrate hexahydrate (0.029 g, 0.1 mmol) and erbium(III) nitrate hexahydrate, (0.046 g,

Table 1. Crystallographic data and experimental details for compound I

Parameter Value

Formula weight 633.99

Temperature, K 293(2)

Crystal system Triclinic

Space group C2/c

a, Â 24.0431(12)

b, Â 9.0516(5)

c, Â 18.7594(9)

ß, deg 114.5062(6)

Volume, Â 3; Z 3714.8(3); 8

Pcalcd g/cm3 2.267

Absorption coefficient, mm-1 5.449

Index ranges -31 < h < 28, 0 < k < 11,

0 < l < 24

F(000) 2448

9 Range for data collection, deg 1.86-27.50

Independent reflections 4098

Observed reflections 10124

Data/restraints/parameters 4098/0/255

Goodness-of-fit on F2 1.264

R index (I> 2a(T))* R1 = 0.0367, wR2 = 0.1221

R index (all data)* Rx = 0.0441, wR2 = 0.1529

Largest diff. peak/hole, e Â-3 2.487/-3.096

* R = EllFj - Fcll/Z Fol], Rw = Zw [F2 - F2|2/ Zw (lFJ2) 2]1/2.

0.1 mmol) were mixed in a water solution (10 mL) of H3Mimda (0.3 mmol, 0.079 g). After stirring for 30 min in air, the aqueous mixture was placed into 25 mL Teflon-lined autoclave under autogenous pressure being heated at 155°C for 72 h, and then the autoclave was cooled over a period of 24 h at a rate 5°C/h, and pink crystals were obtained suitable for X-ray diffraction analysis. The yield was 0.0416 g (53%) based on erbium element.

For C13.5H14.5CoErN4.5O105

anal. calcd., C, 25.58; H, 2.31; N, 9.94; Co, 9.30; Er, 26.38. %:

Found, %: C, 24.59; H, 2.16; N, 9.63.

IR (KBr; v, cm-1): 3471 br, 3140 s, 2453 m, 1612 v.s, 1473 s, 1396 s, 1265 s, 1126 s, 883 s, 787 s.

X-ray crystallography. Single crystal diffraction data of title complex were collected on a Bruker SMART APEX II CCD diffractometer with graphite-mono-chromated Mo^a radiation (X = 0.71073 A) at room temperature. The structures were solved using direct methods and successive Fourier difference synthesis

(SHELXS-97), and refined using the full-matrix least-squares method on F2 with anisotropic thermal parameters for all nonhydrogen atoms (SHELXL-97) [9]. An empirical absorption correction was applied using the SADABS program. These reflections are in the ranges of -31 < h < 28, 0 < k < 11 and 0 < l< 24 with 20max = = 55.0°. 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 maximum and minimum main axis ADP ratio (Angstrom Units) is tested for the main residue, large value may indicate unresolved disorder of solvate, which is difficult identify. Solvate molecules were accounted for by using the program PLATON/SQUEEZE (Spek, 2009), as the result, there are parameters discrepancies between the given and expected value. All non-hydrogen atoms were refined with anisotropic thermal parameters. The final

R = 0.0441, wR = 0.1529 (w = 1/[a2(Fo2) + (0.0852P2) + + 26.6113P], where P = (Fo2 + 2Fc2)/3), (Ap)max = 0.536 and (Ap)mix = -0.467 e/A3. Crystallographic and experimental details are summarized in Table 1, and the selected bond lengths and bond angles are listed in Table 2.

Supplementary material for structure I has been deposited with the Cambridge Crystallographic Data Centre (no. 1019455; deposit@ccdc.cam.ac.uk or http://www.ccdc. cam.ac.uk).

RESULTS AND DISCUSSION

Stoichiometries of I have been confirmed by single X-ray crystallography, elements analysis and thermo-gravimetric analysis. Fig. 1 gives a perspective view of the basic unit in complex I together with atomic labeling system. The asymmetry unit contains one Er3+ ion, one Co2+ ion, four HMimda ligands and two coordinated waters, as well as two free water molecules. The octa-coordinated Er3+cation exhibits distorted dodecahedral prism geometry, being accomplished by an O8 donor set, among which two oxygen atoms are from water molecules, and another six are from imidazole carboxylic groups. HMimda ligands connected adjacent three metal ions in both bridging and chelating fashions (a, b). Diverse coordination modes of H3Mimda ligand in complex I are the following:

/Er O O-

Co

■Er

.Co O ^O

O

(a)

Co--N , N-

(b)

Co

As far as the Co2+ ion is concerned, it exhibits an octahedron geometry, being coordinated by three HMimda ligands. Each HMimda ligand provides

THREE-DIMENSIONAL 3d-4f FRAMEWORKS CONSTRUCTED 273

Table 2. Selected bond lengths (A) and angles (deg) for complex I

Bond d, A Bond d, A Bond d, A

Er(1)—O(7)#1 2.189(5) Er(1)-O(6)#! 2.364(6) Co(1)—O(8)#3 2.096(5)

Er(1)-O(3) 2.228(5) Er(1)—O(6) 2.497(5) Co(1)—N(4)#3 2.107(7)

Er(1)—O(1) 2.259(5) Co(1)—N(2)#2 2.046(6) Co(1)—O(4)#2 2.143(5)

Er(1)—O(2w) 2.300(6) Co(1)—N(1) 2.055(6) Co(1)—O(2) 2.159(5)

Er(1)—O(1w) 2.335(6)

Er(1)—O(6) 2.497(5)

Angle ю, deg Angle ю, deg Angle ю, deg

O(7)#1Er(1)O(3) 78.4(2) O(8)#3Co(1)N(4)#3 77.2(2) O(7)#1Er(1)O(5) 165.1(2)

O(7)#1Er(1)O(2w) 82.5(3) N(2)#2Co(1)O(4)#2 78.2(2) O(3)Er(1)O(5) 94.2(2)

O(3)Er(1)O(2w) 135.7(2) O(7)#xEr(1)O(1) 106.2(2) O(1)Er(1)O(5) 84.4(2)

O(1)Er(1)O(2w) 146.3(2) O(2w)Er(1)O(1w) 71.0(2) O(2 w)Er(1)O(5) 94.4(2)

O(7)#1Er(1)O(1w) 89.0(2) O(7)#xEr(1)O(6)#! 76.69(19) O(1w)Er(1)O(5) 76.2(2)

O(3)Er(1)O(1w) 69.1(2) O(3)Er(1)O(6)#1 135.53(18) O(6)#1Er(1)O(5) 116.83(17)

O(1)Er(1)O(1w) 139.9(2) O(1)Er(1)O(6)#! 74.72(19) N(2)#2Co(1)N(1) 93.8(3)

O(7)#1Er(1)O(6) 139.57(19) O(2w)Er(1)O(6)#! 76.0(2) N(2)#2Co(1)O(8)#3 91.7(2)

O(3)Er(1)O(6) 139.31(19) O(1w)Er(1)O(6)#! 145.41(19) N(1)Co(1)O(8)#3 164.3(2)

O(1)Er(1)O(6) 76.95(17) O(5)Er(1)O(6) 52.1(2) N(1)Co(1)O(2) 77.9(2)

O

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