КООРДИНАЦИОННАЯ ХИМИЯ, 2015, том 41, № 6, с. 375-379
УДК 541.49
SYNTHESIS, STRUCTURAL CHARACTERIZATION, AND PROPERTIES OF A Cd(II) COMPLEX WITH A CARBOXYLATE-AND BENZIMIDAZOLYL-CONTAINING LIGAND © 2015 C. H. Dai and F. L. Mao*
School of Chemistry and Chemical Engineering, Yancheng Teachers University, Yancheng, 224002 P.R. China
*E-mail: yctcmaofl@163.com Received December 6, 2014
The hydrothermal reaction of cadmium salt with 3,5-bis(benzimidazol-1-ylmethyl)benzoic acid (HL) forms a new complex [Cd(L)2] • 3H2O (I). This complex has been characterized by single-crystal X-ray diffraction, IR, elemental and thermogravimetric analyses and shows 3D flu framework structure with 2-nodal (3,6)-connected (42.6)2(44.62.89) topology. Luminescent property of I was investigated. Moreover, single crystals of HL were obtained accidentally in the hydrothermal reaction of the HL with MnSO4 at 160°C, and its crystal structure has been characterized by single-crystal X-ray diffraction (CIF files CCDC nos. 1020274 (HL) and 1020275 (I)).
DOI: 10.7868/S0132344X1506002X
INTRODUCTION
The assembly of coordination polymers has received remarkable attention in recent years because of their fascinating structures and potential applications in magnetism, optical material, catalysis, and adsorption [1]. Generally, the syntheses of complexes involves the metal centers and bridging ligands to fabricate overall architectures, which can be influenced by many factors, such as the nature of metal ions and ligands, solvent, the auxiliary ligands, and the reaction temperature [2]. It is known that the functional properties of the resultant complexes may have a close relation with the intrinsic features of the metal centers and the ligands [3]. And thus, the selection of ligands becomes very important task for the exploration of new crystalline materials. Among the well utilized buildings, N-and O-donors are always regarded as excellent candidates in the construction of desirable frameworks.
Some N- and O-donor ligands, such as 3,5-di(Lff-im-idazol-1-yl)benzoate, 3,5-di(pyridine-4-yl)benzoate, and 5-(isonicotinamido)isophthalate, have been found to be efficient organic building blocks in the construction of new complexes with fascinating structures in the reported literatures [4—6]. However, ligands containing both sterically hindered N-donor groups, such as benz-imidazolyl and carboxylate groups, have also been paid increasing attention because of their distinctive features. Hitherto, 5-(benzimidazol-1-ylmethyl)isophthalic acid and 4-(benzimidazol-1-ylmethyl)benzoic acid have already been selected as organic ligands to assemble new complexes with diverse intriguing structures [7—9], which attracts us to undertake further study on this kind of ligands for the comprehension of the correla-
tion between the synthetic conditions and the structure of resultant complexes.
Recently we have been focusing our attention on the utilization of a benzimidazol-1-yl and carboxy-late-containing ligand 3,5-te(benzimidazol-1-ylme-thyl)benzoic acid (HL) as a building block for the construction of coordination polymers. The arene-cored ligand HL possesses two functional groups, namely carboxylate and sterically hindered benzimidazol-1-yl groups. Due to mutable coordination patterns of the carboxylate, such as ^1-n1:n°-monodentate, ^1-n1:^1-chelating and ^2-^1:^1-briding modes, the HL can show various coordination modes which is helpful to achive structural diversification [1°]. Moreover, the sterically hindered benzimidazolyl group may induce new structural evolution and its large conjugated system is very important for seeking for new fluorescent materials. Herein we report the synthesis and structural characterization of a new complex [Cd(L)2] • 3H2O (I). The thermal stability and fluorescence have been investigated.
EXPERIMENTAL
Materials and methods. All commercially available chemicals were of reagent grade and used as received without further purification. According to the reported literature [7—9], a slightly revised experimental procedure was used to synthesize the HL ligand. Elemental analyses of C, H, and N were taken on a Perkin Elmer 24°C elemental analyzer. Infrared spectra (IR) were recorded on a Bruker Vector22 FT—IR spectrophotometer by using KBr pellets. Thermogravimetric analysis (TGA) was performed on a simultaneous
O
C
Fig. 1. Molecular structure of HL in the single crystal of HL • H2O with the ellipsoids drawn at the 30% probability level. The hydrogen atoms are omitted for clarity.
SDT 2960 thermal analyzer under nitrogen atmosphere with a heating rate of 10°C min-1. The luminescence spectra for the powdered solid samples were measured on an Aminco Bowman Series 2 spectroflu-orometer with a xenon arc lamp as the light source. In the measurements of emission and excitation spectra the pass width was 5 nm, and all measurements were carried out under the same experimental conditions.
Synthesis of I. Reaction mixture of Cd(ClO)4 • 6H2O (41.9 mg, 0.1 mmol), HL (19.1 mg, 0.1 mmol) and KO H (5.6 mg, 0.1 mmol) in 10 mL H2O was stirred for 30 min. Then reaction mixture was placed in a 16 mL Teflon-lined stainless steel container and heated at 180°C for 48 h. And then the oven was shut off and cooled down naturally at ambient temperature. After cooling to the room temperature, block colorless crystals of I were obtained with the yield of 40% based onHL.
For C46H40N8O7Cd (M = 929.26)
anal. calcd., %: C, 59.45; H, 4.34; N, 12.06.
Found, %: C, 59.62; H, 4.26; N, 11.95.
IR data (v, cm-1): 1655 v(C=O), 1612 vas(COO), 1597 vas(COO), 1500 vs(COO), 1458 vs(COO).
X-ray structure determinations. The crystallographic data collections for the complex I and HL • H2O were carried out on a Bruker Smart Apexll CCD area-detector diffractometer using graphite-monochromated Mo^a radiation (X = 0.71073 A) at 200 K. The diffraction data were integrated by using the program SAINT [11], which was also used for the intensity corrections for Lorentz and polarization effects. Semi-empirical absorption corrections were applied using the program SADABS [12]. The structures of I and HL • H2O were solved by direct methods, and all non-hydrogen atoms were refined anisotropically on F2 by the full-matrix
least-squares techniques using the SHELXL-97 crystallographic software package [13]. In I and HL, all hydrogen atoms at C atoms were generated geometrically. The hydrogen atoms at O atoms in HL could be found at a reasonable position in the difference Fourier maps and fixed there. The crystal water in I is badly disordered and could not be modeled and has been removed from the structure by SQUEEZE in PLATON. The suggested number of crystal water molecules was determined according to elemental and thermogravi-metric analyses. The details of crystal parameters, data collection, and refinements are summarized in Table 1, selected bond lengths and angles are listed in Table 2.
Supplementary material has been deposited with the Cambridge Crystallographic Data Centre (CCDC nos. 1020274 (HL) and 1020275 (I); depos-it@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).
RESULTS AND DISCUSSION
Cd(ClO4)2 • 6H2O reacts with 3,5-&is(benzimida-zol-1-ylmethyl)benzoic acid (HL) under hydrothermal conditions at 180°C to yields the complex [Cd(L)2] • 3H2O (I). Moreover, single crystals of HL were obtained accidentally in the hydrothermal reaction of the HL with MnSO4 at 160°C. Complex I and single crystals of HL are stable in air.
The accidentally obtained single crystals the asymmetrical unit of HL • H2O consists of one HL and one crystal water. Because containing two flexible benzim-idazolyl groups, the HL ligand can display the cis- and trans-molecule conformations, respectively. In the accidentally obtained single crystal of HL • H2O, its molecuar conformation is a cis-conformation (Fig. 1), while in complex I, the L- ligand displays a trans-one (Fig. 2a).
Structural analysis shows that complex I exhibits a 3D flu framework structure. The HL molecule was deprotonated to the L- anionic ligand. In the asymmetrical unit of there are one centrosymmetric Cd2+ ion with occupancy of 0.5, one L- ligand, and 1.5 crystal water molecules. Unfortunately, all the crystal water is badly disordered and could not be modeled, which was thus removed from the structural mode of I by SQUEEZE in PLATON. The suggested number of crystal water was determined by elemental and ther-mogravimetric analyses.
As shown in Fig. 2a, Cd2+ ion is six-coordinated by four benzimidazolyl N atoms from four different Land two carboxylate O atoms from two different L- to furnish a distorted octahedral coordination geometry [CdN4O2]: O(1), O(1E), N(1L4), and N(1LD) define the equatorial plane; N(31$) and N(31C) occupy the axial positions. The bond distances around Cd2+ ion are from 2.300(3) to 2.402(3) A. The carboxylate group of the L- ligand exhibit the terminal monodentate mode and each benzimidazolyl group
SYNTHESIS, STRUCTURAL CHARACTERIZATION, AND PROPERTIES
Table 1. Crystallographic data and structure refinement for complex I
377
Parameter Value
I HL • H2O
Formula C^H^O^d C23 H20N4O3
M 929.26 400.43
Crystal size, mm 0.20 x 0.18 x 0.18 0.20 x 0.10 x 0.10
Crystal system Orthorhombic Triclinic
Space group Fddd p1
a, A 18.5913(12) 9.112(5)
b, A 25.9762(16) 10.826(6)
c, A 33.167(2) 11.417(6)
a, deg 90 65.464(7)
P, deg 90 80.188(7)
Y, deg 90 71.480(7)
V, A3 16017.6(17) 970.6(9)
Z 16 2
Pcаlcd, g cm-3 1.54 1.37
^(MoJa), cm-1 0.61 0.093
F(°°°) 7616 420
Limiting indices hkl -22 < h < 23, -23 < k < 32, -41 < l < 40 -10 < h < 10, -12 < k < 12, -13 < l < 9
9 Range, deg 1.99-26.60 1.96-25.01
Reflections measured 22341 4921
Reflections unique 4198 3358
Rint 0.0693 0.0438
Parameter refined 267 271
R(F)/wR(F2)* (all data) 0.0612/0.0686 0.1037/0.2255
GOOF (F2) 1.000 1.033
APmax/APmin, e A~3 0.74/-0.69 0.22/-0.30
* R = S||F0| - |FC||/S|F0|; wR2 = |Sw(|F0|2 - |Fc|2)|/S|w(F0)2|1/2, where w = 1/[a
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.