КООРДИНАЦИОННАЯ ХИМИЯ, 2014, том 40, № 6, с. 358-366
УДК 541.49
TWO COORDINATION POLYMERS FROM 2-p-BUTYLPHENYL IMIDAZOLE DICARBOXYLATE: SYNTHESES, CRYSTAL STRUCTURES,
AND THERMAL PROPERTIES © 2014 R. M. Gao, J. Li, M. W. Guo, and G. Li*
College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou, 450001 P.R. China
*E-mail: gangli@zzu.edu.cn Received June 5, 2013
By employing a newly designed ligand, 2-(p-tert-butylphenyl)-1H-imidazole-4,5-dicarboxylic acid (H3BuPhIDC) to react with manganese(II) or nickel(II) ions, two coordiantion polymers [Mn2(p,3-HBuPhIDC)2(CH3OH)2] (I) and [Ni(^2-HBuPhIDC)(H2O)2] (II) have been solvothermally synthesized and structurally characterized by elemental analyses, IR spectroscopy, and single crystal X-ray diffraction. Polymer I shows a 3D framework bearing 1D octagonal channels constructed from left- and right-handed helical chains. Polymer II exhibits an infinite chain structure, which are joined through the п—п interactions and intramolecular hydrogen bonds to form a 3D architecture. The thermal properties of the polymers have been investigated as well. The coordination ability and modes of H3BuPhIDC have been investigated from both theoretical and experimental aspects.
DOI: 10.7868/S0132344X14050041
INTRODUCTION
In recent years, design and construction of functional coordination polymers (CPs) via metal ions and various organic ligands have become a hot research area. Imidazole-4,5-dicarboxylates (H3IDC) and its derivatives, which have six potential donor atoms: two imidazole nitrogen atoms and four carboxy-late oxygen atoms, have attracted much attention due to their strong coordination ability and variety coordination modes [1—4].
More recently, our laboratory has synthesized a series of imidazole dicarboxylate ligands bearing 2-position phenyl-groups, for example, 2-phenyl-1H-imidazole-4,5-dicarboxylic acid (H3PhIDC), 2-methylphenyl-1H-imidazole-4,5-dicarboxylic acid (H3MePhIDC) and 2-dimethylphenyl-1H-imidazole-4,5-dicarboxylic acid (H3DMPhIDC) [5—7], and successfully obtained some fascinating structures, such as 3D polymer [Mn(|3-HPhIDC)(H2O)2] composed of novel 2D stairlike layers in the yz plane, 3D interpenetrating framework {[Co15(p-MePhIDC)(H2O)3] ■ H2O}„ containing honeycomb-like cages, and 3D polymer {[Co3(|3-DMPhIDC)2(H2O)6] ■ ■ 2H2O}b bearing infinite 1D hexagonal channels and
[Co2(DMPhIDC)]6 cages. As one might expect, the relative orientations of the imidazole dicarboxylate is a key factor to determine the structures of the MOFs. Changes in the substituents on the phenyl ring to which the imidazole dicarboxylate units are attached may result in different spatial arrangements of the MOFs. At the same time, our findings indicated that the bulky aromatic group can supply additional stabilizing forces for solid-state crystallizing packing.
Encouraged by our preliminary studies, we continuously investigate butylphenyl substituted imidazole dicarboxylate ligand at 2-position and successfully prepare a new organic ligand, 2-(p-feri-butylphenyl)-1H-imidazole-4,5-dicarboxylic acid (H3BuPhIDC), and hope to explore its coordination features. To our excitement, two MOFs, namely [Mn2(|3-HBuPhIDC)2(CH3OH)2] (I) and [Ni(|2-HBuPhIDC)(H2O)2] (II), have been synthesized (Scheme). In this paper, we will present the crystal structures and thermal properties of the two coordination polymers I and II, and describe the coordination modes of HBuPhIDC2- anions (Fig. 1).
[Ni( p.2-HBuPhIDC)(H2O)2] (NcN/Ho^Et^N
Polymer II
160°C,3d
Scheme.
chMOH/haEU [Mn2(fe-HBuPhIDC)2(CH3OH)2]
Polymer I
160°C,3d
(a)
(b)
■V— ■ M OHC C NC C C C
OC NCC CCC OM
M
^3-HBuPhIDC2
C
OM
^2-HBuPhIDC2
Fig. 1. Coordination modes of HBuPhIDC2 anions in polymers I (a) and II (b).
EXPERIMENTAL
All chemicals were of reagent grade quality obtained from commercial sources and used without further purification. The organic ligand H3BuPhIDC was prepared according to literature procedure [8]. The C, H, and N microanalyses were carried out on a FLASH EA 1112 analyzer. IR spectra were recorded on a BRUKER TENSOR 27 spectrophotometer as KBr pellets in the 400—4000 cm-1 region. TG measurements were performed by heating the crystalline sample from 20 to 680°C at a rate of 10°C min-1 in the air on a Netzsch STA 409PC differential thermal analyzer.
Synthesis of
(10.1 mg, 0.05
I. A mixture of MnCl2 • 4H2O mmol), H3BuPhIDC (14.5 mg,
0.05 mmol) CH3OH-H2O (3 : 4, 7 mL), Et3N (0.014 mL, 0.1 mmol) were sealed in a 25 mL Teflon-lined stainless steel autoclave, heated at 160°C for three days, and then cooled to room temperature. Colorless lamellar crystals of I were isolated, washed with distilled water, and dried in air (39% yield based on Mn).
IR (KBr; v, cm-1): 3430 m, 2959 m, 1597 s, 1573 s, 1491 m, 1405 s, 1363 w, 1344 m, 1116 w, 841 w, 715 w.
For C32H34N4OioMn2
anal. calcd., %: Found, %:
C, 51.57; C, 51.79;
H, 4.56; H, 4.28;
N, 7.52. N, 7.34.
Synthesis of II. A mixture of Ni(NO3)2 • 6H2O (14.5 mg, 0.05 mmol), H3BuPhIDC (14.5 mg, 0.05 mmol) CH3CN—H2O (3 : 4, 7 mL), Et3N (0.014 mL, 0.1 mmol) were sealed in a 25 mL Teflon-lined stainless steel autoclave, heated at 160°C for three days, and then cooled to room temperature. Glitter green block—shape crystals of II were isolated, washed with distilled water, and dried in air (51% yield based on Ni).
IR (KBr; v, cm-1): 3592 m, 2965 m, 1707 w, 1621 m, 1560 s, 1493 m, 1435 s, 1365 w, 1281 w, 1130 w, 844 w, 760 w.
For C15H18N2O6Ni
anal. calcd., %: C, 47.36; H, 4.74; N, 7.37. Found, %: C, 47.19; H, 4.31; N, 7.58.
X-ray crystallography. Measurements of compounds I and II were made on a Bruker smart APEXII CCD diffractometer with a graphite-monochromated Mo^ radiation (X = 0.71073 A). Single crystals of I and II were selected and mounted on a glass fiber. All data were collected at room temperature using the ®-29 scan technique and corrected for Lorenz-polarization effects. A correction for secondary extinction was applied. The two structures were solved by direct methods and expanded using the Fourier technique. The non-hydrogen atoms were refined with anisotropic thermal parameters. Hydrogen atoms were included but not refined. The final cycle of full-matrix least squares refinement was based on 7047 observed reflections and 443 variable parameters for I, 3739 observed reflections and 233 variable parameters for II. All calculations were performed using the SHELX-97 crys-tallographic software package [9]. Crystal data and experimental details for compounds I and II are contained in Table 1. Selected bond lengths and angles are listed in Table 2. Supplementary material has been deposited with the Cambridge Crystallographic Data Centre (nos. 895529 and 913637 for I and II, respectively; deposit@ccdc.cam.ac.uk or http://www.ccdc. cam.ac.uk).
Quantum-chemical calculation. The optimized geometry and natural bond orbital (NBO) charge distributions of the free ligand H3BuPhIDC were given by the GAUSSIAN 03 suite of programs [10]. And all calculations were carried out at the B3LYP/6-311++G(d, p) level of theory.
Table 1. Crystal data and structure refinement information for compounds I and II
Parameter Value
I II
Temperature, K 296(2) 296(2)
Fw 744.51 381.02
Crystal system Tetragonal Orthorhombic
Crystal size, mm 0.23 x 0.20 x0.19 0.22 x 0.20 x 0.20
Space group 14 Ibca
a, A 20.6044(9) 12.0233(13)
b, A 20.6044(9) 21.236(2)
c, A 16.2760(14) 25.690(3)
V, A3 6909.8(7) 6559.3(12)
Pcalcd mg m-3 1.431 1.543
Z 8 16
p., mm-1 0.791 1.217
Reflections Nillected/unique (Rint) 19667/7047 (0.0708) 19075/3739 (0.0685)
Data/restraints/parameters 7047/0/443 3739/0/233
GOOF on F 2 0.950 1.032
R 0.0627 0.0390
wR 0.1585 0.1005
APmax and Ap^n e A.-3 0.610 and -0.492 0.476 and -0.480
RESULTS AND DISCUSSION
To obtain theoretical information for the ligand H3BuPhIDC, we have investigated the tert-butyl-phe-nyl substituent effect in H3BuPhIDC by theoretical calculation [10]. The computed results reveal that the free ligand H3BuPhIDC has two characteristics:
(1) The negative NBO charges mainly distribute on the oxygen and nitrogen atoms. The NBO charges are -0.636, -0.648, -0.666, and -0.599 for four carboxy-late oxygen atoms, -0.460 and -0.498 for two imidazole nitrogen atoms (Fig. 2, Table 3). These values indicate that the oxygen and nitrogen atoms of the ligand all have potential coordination ability. So H3BuPhIDC may show superior strong coordination ability under appropriate conditions. This finding can be confirmed by our present experimental results.
(2) As shown in Table 3, compared with the free ligand PhH3IDC [5], the introduction of 2-tert-butyl group into H3BuPhIDC, has slight effect on the NBO charge distributions of oxygen and nitrogen atoms. That is to say, the substituent effect of 2-tert-butyl group is slight. Although it should be given more consideration on bulky aromatic groups in the ligand, it can be predicted that the strong coordination ability can suppress the steric effect of the aromatic group.
A single-crystal X-ray diffraction study shows that compound I is the open 3D structure crystallizing in the tetragonal space group 14. The asymmetrical unit
of I consists of two Mn2+ cations, two discrete HBuPhIDC2- ligands, as well as two coordination methanol molecules. Two Mn atoms in the center position here are associated with a center inversion operation. Each of them is in a slightly distorted octahedral geometry [MnN2O4]: two imidazole nitrogen (N(2) and N(4b)) and two carboxylate oxygen atoms (O(4) and O(6)) from two individual HBuPhIDC2- anions, one carboxylate oxygen atom (O(3)) from another one |-bridging HBuPhIDC2- anion, and one oxygen atom (O7) from the coordinated methanol molecule (Fig. 3a). The Mn-N bond lengths are in the range of 2.024(6)-2.074(6) A, while the Mn-O distances span from 2.094(6) to 2.297(6) A. The bond angles around the central Mn2+ ion vary
Для дальнейшего прочтения статьи необходимо приобрести полный текст. Статьи высылаются в формате PDF на указанную при оплате почту. Время доставки составляет менее 10 минут. Стоимость одной статьи — 150 рублей.