КООРДИНАЦИОННАЯ ХИМИЯ, 2014, том 40, № 1, с. 14-19
УДК 541.49
CONSTRUCTION OF TWO NEW 3D SUPRAMOLECULAR NETWORKS WITH 3-PYRIDYL-4-YL-BENZOIC ACID LIGANDS: SYNTHESIS, CHARACTERIZATION, AND LUMINESCENCE
© 2014 J. Guo1, 2, S. J. Li1, D.-L. Miao3, J. S. Liu1, *, and W. D. Song2, *
1School of Environmental Science and Engineering, Donghua University, Shanghai, 200051 P.R. China 2School of Petrolium & Chemical Engineering, Zhanjiang Ocean University, Zhoushan, 316000 P.R. China 3College of Food Science and Technology, Guangdong Ocean University, Zhanjiang, 524088 P.R. China *E-mail: liujianshe@dhu.edu.cn; songwd60@126.com Received April 17, 2012
Two new coordination polymers with 3-pyridyl-4-yl-benzoic acid (3,4-HPybz), namely, [Zn(3,4-Pybz)2 • 2H2O]n (I) and [Ag(3,4-Pybz)(3,4-HPybz)]n (II), have been synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and single crystal X-ray diffraction. Compound I crystallizes in the triclinic system and has P1 space group. Complex I is an infinite 1D chain polymer and the infinite chains array uniformly in a 3D supramolecular network which posesses abundant O—H-O hydrogen-bonding interactions among the occupied and unoccupied carboxylate O atoms and the coordinated water molecules; Compound II crystallizes in the triclinic system and has P1 space group, II is an infinite chain with the repeat sequence of Ag1(I)—Ag2(I)—Ag1(I), in which weak intermolecular interactions play a key role in forming the final 3D supramolecular architectures. The photoluminescences and lifetime of I and II in the solid state have been investigated.
DOI: 10.7868/S0132344X14010010
INTRODUCTION
The past decade has witnessed tremendous progress in the synthesis of metal-organic frameworks and the investigation of their properties. The compounds based on the ligands and metal centers display a great variety of properties, such as molecular recognition, heterogeneous catalysis, ion exchange, magnetic and photochemical areas, as well as their intriguing variety of topologies [1—4]. Generally, the diversity of the framework structures of such materials as the result of the self-assemble process greatly depends on the selection of the metal centers and organic spacers, as well as on the reaction pathways [5]. In addition, weak intermolecular forces in these coordination polymers have been well-studied and can be used to to design and synthesize complexes with interesting architectures and functions. The judicious selection of a multifunctional ligand with hydgrogen donors and acceptors and suitable spacers between linking groups to connect metal ions to generate a fascinating configuration is a common strategy.
N-Heterocyclic multicarboxylic acids have been widely used to construct coordination polymers for their potential application. Among the reported frameworks, the multifunctional organic ligands that incorporate both pyridyl and carboxylate groups, such as 3-pyridyl-3-yl-benzoate and 4-pyridyl-4-yl-ben-
zoate, have been proved to be excellent candidates for constructing novel coordination polymers with different properties [6].
However, their isomeric building block 3-pyridin-4-yl-benzoate has been largely unexplored so far [7, 8]. Four 3D complexes assembled from Mn(II), Zn(II), Cd(II), or Pb(II) with 3,4-Pybz are presented in [9], two isostructural complexes are obtained in [10] and three isostructural complexes are reported and studied the magnetic properties in [11].
We choose the unsymmetrical ligand 3-pyridin-4-yl-benzoic acid (3,4-Hpybz) in the self-assembly. Herein, we report two 3D supramolecular networks: [Zn(3,4-Pybz)2 ■ 2H2O]B (I), [Ag(3,4-Pybz)(3,4-HPybz)]B (II). Complexes I and II are 1D infinite chains and extended into the final 3D framework via hydrogen bonding and/or n-n stacking interactions.
EXPERIMENTAL
Materials and measurements. All solvents and reagents were commercially available and used without further purification. Elemental (C, H, and N) analyses were performed on PerkinElmer 240 CHN element analyzer. Infrared (IR) spectra were recorded (4000— 400 cm-1) as KBr disks on a Bruker 1600 FTIR spectrometer. Thermogravimetric analysis (TGA) experi-
ments were carried out on a PerkinElmer TG/DTA 6300 system with a heating rate of 10°C/min from room temperature to 600°C under nitrogen atmosphere. Luminescence spectra for crystal solid samples were recorded at room temperature on a Hitachi F-4500 fluorescence spectrophotometer.
Synthesis of complex I. A mixture of Zn(NO3)2 ■ ■ 6H2O (0.14 g, 0.5 mmol), 3,4-HPybz (0.1 g, 0.5 mmol) and H2O (10 mL) with pH adjusted to 4 was stirred for 30 min in air. Afterwards, it was sealed in a 20 mL Teflon reactor and kept under autogenous pressure at 150°C for 96 h. The mixture was cooled to room temperature at a rate of 5°C h-1 and colorless plate crystals were obtained in a yield of 51% based on Zn.
For C24H20N2O6Zn (I)
anal. calcd., %: C, 57.85; H, 4.02; N, 5.62. Found, %: C, 57.78; H, 4.06; N, 5.63.
IR bands (KBr; v, cm-1): 3242 s, 1589 s, 1537 v.s, 1409 s, 1373 s, 1196 w, 1136 s, 1036 w, 1007 w, 863 s, 779 v.s, 708 w, 558 w, 484 w.
Synthesis of complex II. A mixture of AgNO3 (0.09 g, 0.5 mmol), 3,4-Hpybz (0.14 g, 0.5 mmol) and water (15 mL) was stirred for 30 min in air with the pH of 8 adjusted by NaOH, sealed in a 20 mL Teflon reactor and kept under autogenous pressure at 170°C for 72 h. The mixture was cooled to room temperature at a rate of 5°C h-1 and colorless plate crystals were obtained in a yield of 36% based on Ag.
For C24H17N2O4Ag (II)
anal. calcd., %: C, 57.00; H, 3.36; N, 5.54. Found, %: C, 56.82; H, 3.33; N, 5.63.
IR bands (KBr; v, cm-1): 3067 w, 1695 s, 1592 s, 1433 s, 1340 w, 1135 s, 864 s, 812 w, 776 s, 742 w, 705 w, 507 w.
X-ray structure determination. Diffraction data of complexes I and II were performed on a Bruker SMART CCD 1000 diffractometer operating at 50 kV and 30 mA using Mo^a radiation (X = 0.71073 A) at 298 K. Data collection and reduction were performed using the SMART and SAINT software [12], Multiscan absorption correction was applied using the SADABS program [12]. The structures were solved by direct methods and refined by full-matrix least-squares techniques using the SHELXTL program package [13]. All non-hydrogen atoms were treated anisotropically. The hydrogen atoms belonging to C and N atoms were calculated theoretically. The hydrogen atoms of water molecules were located in a difference Fourier maps. Hydrogen atoms on water molecules were located from difference Fourier maps and refined with distance restraints of O-H 0.84(2) A and H-H 1.39(2) A. Crystal data and details of the data collection and refinement for two compounds are listed in Table 1. The data for selected bond lengths, an-
gles and hydrogen bonds are listed in Table 2. Supplementary material has been deposited with the Cambridge Crystallographic Data Centre (nos. 857472 (I), 857472 (II); deposit@ccdc.cam.ac.uk or http:// www.ccdc.cam.ac.uk).
RESULTS AND DISCUSSION
The asymmetric unit of I (Fig. 1a) consists of one Zn2+ ion, two 3,4-Pybz ligands and two coordinated water molecules. Each Zn(II) center is hexa-coordinat-ed with a distorted octahedral coordination geometry supplied by two carboxylate oxygen atoms from one 3,4-Pybz ligand, two nitrogen atoms from two different 3,4-Pybz ligands and two oxygen atoms from two coor-
dinated water molecules. The Zn(1)-O,
caboxylate
bonds
(2.175(4) and 2.194(4) A) are slightly longer than the Zn-Owater bonds (1.997(4) and 2.109(4) A). This may due to that the carboxylate group in the bidentate chelating mode weakens the Zn-O bonding interactions. All Zn-O distances (from 1.997(4) to 2.194(4) A) and Zn-N distances (from 2.100(4) to 2.305(5) A) falls in the normal range. 3,4-Pybz ligands in complex I display two kinds of coordination modes:
Zn
Zn
O< >O
Zn
HO:
N'
'Ag
Ag
-O
O; I
Ag
Scheme 1.
One moda connects one Zn(II) center via pyridyl-N atom; the other chelates one Zn(II) center via the car-boxylate group in the bidentate chelating mode and bridges another Zn(II) center via one pyridyl-N atom. Based on such coordination modes of L ligands, an infinite 1D chain was formed (Fig. 1b), such adjacent 1D chains are connected into a 2D layer via O(2w)-H(4w)--O(3) hydrogen-bonding interaction between the depronated carboxylate O atoms and the coordinated water molecules (Fig. 1c). The 2D layers are further extended into 3D supramolecular net via O-H■■■ O hydrogen-bonding interactions (O(2w)-H(3w)--O(4), O(1w)-H(2w)"-O(3), and O(1w)-H(1w)-O(2)) among the occupied and unoccupied carboxylate O atoms and the coordinated water molecules (Fig. 1d).
Table 1. Crystallographic data and refinement parameters for structures I and II
Parameter
Value
I
II
Empirical formula Formula weight Crystal size, mm Crystal system Space group
a, Â
b, Â c, Â a, deg P, deg Y, deg V, Â3
Pcalcd mg/cm3
Z
F(000)
Absorption coefficient, mm-1 Max and min transmission 9 Range for data collection, deg Limiting indices Reflections collected/unique Completeness to 9 = 25.00, % Data/restraints/parameters GOOF
Final R indices (I> 2ct(T)) R indices (all data)
C24H29N2O6Zn
497.79 0.42 x 0.39 x 0.21 Triclinic
P1 6.0528(6) 7.7930(4) 11.6702(12) 84.386(2) 75.8830(10) 84.801(2) 530.02(8) 1.560 1
256 1.204 0.7861 and 0.6317 2.63-25.00 -6 < h < 7, -9 < k < 9, -13 < l <12 2714/2207
98.2 2207/9/298 1.068
R1 = 0.0282, wR2 = 0.0650 R1 = 0.0294, wR2 = 0.0657
-9
C24H17N2O4Ag
505.27 0.30 x 0.28 x 0.11 Triclinic
PI
8.2484(9) 10.3371(11) 12.2031(14) 89.588(2) 87.0870(10) 70.9240(10) 982.03(19) 1.709 2
508 1.062 0.8921 and 0.7411 2.62-25.00 < h < 9, -12 < k < 12, -14 < l < 10 5119/3400
98.70 3400/0/283 1.023
R1 = 0.0389, wR2 = 0.0805 R1 = 0.0644, wR2 = 0.0956
Rx = Z(|F0| - |Fc|)/Z|F0|wR2 = [Zw (|F0|2 - |Fc|2)2/Zw(/0)2]^2.
Table 2. Geometric parameters of hydrogen bonds for complexes I and II*
Contact D H-A Distance, Â Angle D H-
D-H H-A D-A
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