КООРДИНАЦИОННАЯ ХИМИЯ, 2014, том 40, № 1, с. 27-31
УДК 541.49
HYDROTHERMAL SYNTHESIS, CRYSTAL STRUCTURE, AND PROPERTIES OF TWO NOVEL BINUCLEAR COMPLEXES BASED ON ZALTOPROFEN
AND 2,2'-BIPYRIDINE LIGANDS
© 2014 J. N. Tang, Z. J. Huang*, D. Y. Wang, T. T. Ren, L. Li, and G. H. Pan
College of Chemistry and Chemical Engineering, Guangxi University for Nationalities, Nanning, 530006 P.R. China
*E-mail: tangjinniu@126.com Received January 10, 2012
Two novel binuclear metal-organic coordination complexes [M2(Zaltoprofen)2(Bipy)2] [M = Cd (I), Zn (II); Zaltoprofen = 5-(1-carboxyethyl)-2-(phenylthio)phenylacetic acid, Bipy = 2,2'-bipyridine) have been synthesized under hydrothermal conditions and characterized by single crystal X-ray diffraction, elemental analysis, IR and electronic spectroscopy, powder X-ray diffraction, and fluorescent properties. Complexes I, II crystallize isomorphously in the monoclinic space group P2i/c. Structural analysis shows that the M(II) atom of I and II is coordinated with four oxygen atoms from the carboxyl group of the Zaltoprofen together with two nitrogen atoms from the Bipy. The 3D structures of the complexes are stabilized by п—п stacking interactions.
DOI: 10.7868/S0132344X14010071
INTRODUCTION
During the past decade, the design of new metal-organic supramolecular solids has attracted ever-increasing focus in the elds of coordination chemistry and crystal engineering, for the sake of developing desired crystalline materials with potential functionality [1—3]. Generally, extended higher-dimensional supramolecular architectures can be obtained by the assembly of lower-dimensional structures via coordina-tive force and other weak non-covalent interactions. Aromatic ring stacking is one important type of intramolecular non-covalent interactions, which play vital roles in highly efficient and specific biological reactions and are essential for molecular recognition and self-organization [4, 5].
Zaltoprofen is one of non-steroidal anti-inflammatory drugs that exhibit favorable anti-inflammatory, anal-genesic and antipyretic properties. But to our knowledge, using Zaltoprofen to construct metal-organic frameworks has not been reported. As a multifunctional ligand, Zaltoprofen has attracted our attention on the basis of the following considerations. The carboxyl is always deprotonated to compensate the charge of the metal ions, and it may allow for diversity in the coordination mode. The ligand has larger conjugated n-systems, therefore n-n stacking interactions and/or C—H-n interactions may play important roles in the formation of higher-dimensional supramolecular frameworks. Chelating bipyridine-like ligands, such as 1,10-phenanthroline and 2,2'-bipyri-dine (Bipy) may provide supramolecular recognition sites for n-n stacking interactions to form interesting
supramolecular structures [6, 7]. The chemistry of metal-organic molecular architectures of Bipy-like and carboxylate ligands has been reviewed [8].
As a continuation of our research, we report synthesis, crystal structure, elemental analyses, IR spectrum, powder X-ray diffraction (XRD) and fluorescent properties of two novel supramolecular complexes [M2(Zaltoprofen)2(Bipy)2], which is formed by n—n stacking interactions. Electronic spectra (UV-vis) and photoluminescence properties of complexes in the solid state have also been investigated below in detail.
EXPERIMENTAL
Materials and physical measurements. All chemicals were commercial materials of analytical grade and used without purification. Elemental analysis for C, H, and N was carried out on a PerkinElmer 2400 II elemental analyzer. The FT-IR spectrum was obtained on a PE Spectrum One FT-IR Spectrometer Fourier transform infrared spectroscopy in the 4000— 400 cm-1 region, using KBr pellets. XRD patterns were obtained using a pinhole camera (Anton Paar) operating with a point focused Ni-filtered Cu^a radiation in the 29 range from 5° to 50° with a scan rate of 0.08° per second. The optical properties were analyzed by the UV-vis diffuse reflectance spectroscopy (DRS) using a UV-vis spectrophotometer (Cary-500, Varian Co.), in which BaSO4 was used as the internal standard.
Fig. 1. The coordination environment of M2+ ion of the complexes.
Synthesis of [Cd2(Zaltoprofen)2(Bipy)2] (I).
3CdSO4 ■ 8H2O (0.2565 g, 0.33 mmol), Zaltoprofen (0.1582 g, 0.5 mmol), NaOH (0.04 g, 1 mmol), Bipy (0.0783 g, 0.5 mmol) were added into 15 mL mixed solvent of DMF—EtOH—H2O (volume ratio 1 : 1 : 1) and then stirred. The resulting mixture was sealed in a 25 mL Teon-lined stainless reactor, kept under autogenous pressure at 130 °C for 72 h and then slowly cooled to room temperature at a rate of 5°C per hour. The colorless block crystals suitable for X-ray diffraction were isolated directly. The yeld was 78% based on Cd.
For C54H44N4O8 S2Cd2
anal. calcd., %: C, 55.63; H, 3.80; N, 4.81. Found: %: C, 55.67; H, 3.76; N, 4.83.
IR data (KBr; v, cm-1): 3070 w, 2963 w, 1564 v.s, 1475 m, 1439 m, 1385 s, 1318 w, 1264 w, 1169 w, 1067 m, 948 w, 880 w, 770 m, 736 m, 690 w, 648 w.
Synthesis of [Zn2(Zaltoprofen)2(Bipy)2] (II). The
reagents of Zn(NO3)2 ■ 6H2O (0.2975 g, 1 mmol), Zaltoprofen (0.1582 g, 0.5 mmol), Bipy (0.0783 g, 0.5 mmol), five drop of pyridine and 15 mL mixed solvent of DMF-H2O (volume ratio 1 : 2) were sealed in a 25 mL Teon-lined stainless reactor and the mixture was stirred for 0.5 h, then kept under autogenous pressure at 145°C for 72 h. The resulting reaction mixture was slowly cooled to room temperature at a rate of 5°C per hour. The colorless block crystals suitable for X-ray
diffraction were isolated directly. The yield was 63% based on Zn.
For C54H44N4O8 S2Zn2 anal. calcd., %: C, 60.51; Found: %: C, 60.38;
H, 4.14; N, 5.23. H, 4.05; N, 5.35.
IR data (KBr; v, cm-1): 3070 w, 1598 v.s, 1520 w, 1490 w, 1476 w, 1383 s, 1319 w, 1269 w, 1251 w, 1179 w, 1066 m, 1025 m, 880 w, 832 w, 801 m, 774 m, 736 m, 690 w.
X-ray structure determination. Single crystal of the complex was mounted on glass fibers and measured on a Bruker SMART CCD area detector at 298 K using graphite monochromated Mol^ radiation (X = 0.71073 Â). Empirical absorption corrections were applied using the SADABS program [9]. The complexes were solved by the direct method and PATT method, respectively. And refined by full-matrix least squares on F2 using the SHELXTL program [10]. All non-hydrogen atoms were refined anisotronically. A summary of the crystal-lographic data and structure refinement is shown in Table 1, selected bond lengths and angles of the complexes are listed in Table 2.
Further information about the Crystallographic analysis is deposited in the Cambridge Crystallogra-phic Data Centre (nos. 882954 (I) and 902638 (II); www.ccdc.cam.ac.uk/data_request/cif or deposit@ ccdc.cam.ac.uk).
RESULTS AND DISCUSSION
Single-crystal X-ray diffraction on I, II reveals that they are extremely similar in structure with the formu-
Table 1. Crystallographic data and refinement details for structures I and II
Parameter Value
I II
Formula weight 1165.89 1071.79
Crystal system, space group Monoclinic, P21/c Monoclinic, P21/c
Unit cell dimensions:
a, A 13.602(3) 13.2873(14)
b, A 11.658(3) 11.9309(19)
c, A 15.667(3) 15.267(2)
P, deg 92.552(1) 93.0760(10)
Volume, A3 2481.9(10) 2416.8(6)
Z 2 2
Pcalcd, mg m—3 1.560 1.473
Absorption coefficient, mm-1 1.000 1.140
/(000) 1176 1104
Crystal size 0.32 x 0.31 x 0.29 0.16 x 0.15 x 0.13
9 Range for data collection, deg 1.50-25.00 2.17-25.00
Reflections collected 12653 12869
Unique reflections (Rint) 4323 (0.0733) 4248 (0.0575)
Completeness to 9 = 25.00, % 98.9 99.8
Absorption correction Semiempirical Semiempirical
Max and min transmission 0.748 and 0.733 0.862 and 0.833
Data/restraints/parameters 4323/0/317 4248/19/236
Goodness-of-fit on F2 1.011 0.956
R indices (I > 2ct(T)) R1 = 0.0432, wR2 = 0.0911 R1 = 0.0485, wR2 = 0.1132
R indices (all data) R1 = 0.0988, wR2 = 0.1203 Rx = 0.1010, wR2 = 0.1363
Largest diff. peak and hole, e A-3 0.958 and -0.458 0.673 and -0.444
la [M2(Zaltoprofen)2(Bipy)2] (M = Cd (I), Zn (II)). The crystal lattice of the complexes belong to the monoclinic system with a space group P21/c. The coordination environments of M2+ ion in the two binu-clear complexes are shown in Fig. 1. The coordination environment around the M(II) center is best portrayed
as a distorted [MN2O4] octahedral geometry, ligated by four oxygen atoms from one Zaltoprofen ligand, two nitrogen atoms from one chelate Bipy. The 1D chains are linked by n—n stacking interaction (Fig. 2). Two adjacent Bipy molecules are connected by n—n stacking between pyridine rings with a distance of 3.737 A
Fig. 2. A perspective view of the n—n stacking interaction. All the hydrogen atoms are omitted for clarity.
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Table 2. The selected bond lengths (A) and angles (deg) for structure I and II*
Bond d, A Bond d, A
Cd(1)-O(2) Cd(1)-O(3)#1 Cd(1)-N(1) Zn(1)-O(2) Zn(1)-N(2) Zn(1)-O(1) 2.288(4) 2.350(3) 2.335(4) I 2.008(6) 2.067(6) 2.372(0) Cd(1)-O(1) Cd(1)-O(4)#! Cd(1)-N(2) I Zn(1)-O(3)#! Zn(1)-N(1) Zn(1)-O(4)#! 2.417(4) 2.327(4) 2.313(4) 2.040(6) 2.090(7) 2.417(9)
Angle ro, deg Angle ro, deg
O(2)Cd(1)N(2) O(2)Cd(1)O(4)#1 N(2)Cd(1)O(4)#1 O(2)Cd(1)N(1) N(2)Cd(1)N(1) O(4)#*Cd(1)N(1) O(2)Cd(1)O(3)#1 N(2)Cd(1)O(3)#1 O(2)Zn(1)O(3)#1 O(3)#*Zn(1)N(2) O(3)#1Zn(1)N(1) O(2)Zn(1)O(1) N(2)Zn(1)O(1) O(2)Zn(1)O(4)#1 N(2)Zn(1)O(4)#1 O(1)Zn(1)O(4)#! 111.85(15) 142.23(15) 98.97(14) 113.92(15) 71.31(16) 95.92(15) 98.71(15) 94.89(14) I 139.6(5) 105.2(9) 114.3(7) 58.6(0) 93.6(6) 104.3(5) 149.7(1) 110.1(4) O(3)#*Cd(1)O(1) N(1)Cd(1)O(1) O(4)#*Cd(1)O(1) N(2)Cd(1)O(1) O(2)Cd(1)O(1) N(1)Cd(1)O(3)#! O(4)#1Cd(1)O(3)#1 I O(2)Zn(1)N(2) O(2)Zn(1)N(1) N(2)Zn(1)N(1) O(3)#1Zn(1)O(1) N(1)Zn(1)O(1) O(3)#1Zn(1)O(4)#1 N(1)Zn(1)O(4)#! 116.82(14) 85.56(16) 107.46(14) 146.48(14) 55.60(15) 147.27(15) 56.01(13) 104.0(0) 98.2(7) 78.2(9) 92.3(1) 153.2(6) 56.9(0) 87.2(9)
* Symme
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