КООРДИНАЦИОННАЯ ХИМИЯ, 2014, том 40, № 10, с. 593-599
УДК 541.49
ANIONS-INDUCED ASSEMBLY: STRUCTURES AND LUMINESCENT PROPERTIES © 2014 N. Zhang1, L. P. Wang2, D. L. Xu1, M. D. Yang1, Q. Y. Zhu3 *, and H. P. Zhou1, *
1College of Chemistry and Chemical Engineering, Key Laboratory of Functional Inorganic Materials Chemistry of Anhui Province, Anhui University, Hefei, 230601 P.R. China 2Department of Civil Engineering, Anhui Communication Vocational and Technical College, Hefei, 230051 P.R. China 3Department of Chemistry, Huainan Normal College, Huainan, 232001 P.R. China
*E-mail: zhpzhp@263.net Received February 21, 2014
Self-assembly of a multidentate ligand containing pyridyl groups, namely, 6-phenyl-4-(4'-[2-(2-naphtha-lene)ethenyl]phenyl)-2,2'-bipyridine (L) with corresponding zinc(II) salts, affords a series of coordination complexes, ZnLI2 (I), [ZnLCl2]2 ' 2CH2Cl2 (II), ZnLBr2 (III). Complexes I and II were characterized by single crystal X-ray diffraction (CIFfiles CCDC nos. 943273 (I), 944798 (II)). In complex I, the n-n stacking and C—H—n interactions based on the pyridyl group constructed the 1D and 2D structures. While in complex II, various weak interactions including hydrogen bonds (C—H-Cl and C—H-тс) played significant roles in the final supramolecular structures. The luminescent properties of ligand and the complexes were investigated. The results reveal that different anions have shown a great influence on both the molecular structures and luminescent properties of the complexes.
DOI: 10.7868/S0132344X14100120
INTRODUCTION
In recent years, the design and synthesis of organic-inorganic hybrid complexes based on strong coordinate bonds and multiple weak non-covalent forces have become hot spots along with the rapid development in coordination chemistry and crystal engineering owing to their fascinating structural features and interesting properties as new functional materials with tremendous potential applications in the areas of luminescence, catalysis, separation, adsorption, biological chemistry, and so on [1—3]. Many supramolecular coordination complexes with specific topologies and excellent properties have been synthesized by assembly of metal salts and organic ligands [4, 5]. So far, considerable progress has been achieved in dominating the assembly and orientation of individual building blocks into structures with specific topologies and-functions including ion/molecular recognition, selective guestinclusion, ion exchange, etc. [6, 7]. However, it is still very difficult to design and synthesize su-pramolecular architectures with predicted structures due to multiple weak intermolecular interactions to control the molecular packing [8]. Moreover, although a lot of interesting metal-organic frameworks have been constructed from mixed ligands, the effects of the counter-anions on the assembly process of anionic and neutral mixed ligands with metal ions have also seldom been investigated. Hence, it is a challenge to predict and control the exactly discrete coordination architectures or infinite polymeric networks through
the self-assembly process of metal ions and mixed ligands in crystal engineering since the structures are highly influenced by the coordination preferences of metal ions, the nature of organic ligands, and some very subtle factors, such as counter-anions [9].
The chemistry of anions as components in su-pramolecular assemblies is an area of increasing interest. Anions are of critical importance due to the vital roles they play in biological and industrial processes. Anions also have proven ability to afford structural control of supramolecules through interactions with other components [10—12]. The organic ligands can control the topology of coordination complexes. The design and synthesis of new organic ligands is a key approach for construction of metal-organic complexes with desired structures and properties. In designing coordination complexes, pyridyl derivatives have been widely used as ligands due to their ability to coordinate with several metal centers in various modes [13].
We have an on-going interest in nitrogen based on heterocyclic ligands and the fascinating structural diversity possible in their combination with zinc salts [14]. Taking the above into consideration and in order to construct new coordination complexes with specific structures and properties, a multidentate ligand containing pyridyl groups, namely, 6-phenyl-4-(4'-[2-(2-naphthalene)ethenyl]phenyl)-2,2' (L) has been designed and synthesized according to the following Scheme:
CH2P+Ph3Br-
CHO
. , <-BuOK „
+ \__grind * N
(M)
(L)
Herein, we present structures and luminescent properties of the following complexes: ZnLI2 (I), [ZnLCl2]2 ■ 2CH2Cl2 (II), ZnLBr2 (III).
EXPERIMENTAL
General methods. All commercially available chemicals are of reagent grade and used without further purification. Elemental analyses were carried out on a PerkinElmer 240 analyzer. IR spectra were recorded with a Nicolet FT-IR NEXUS 870 spectrometer (KBr disks) from 4000 to 400 cm-1. The solid state luminescence spectra were measured on a F-4500FL spectrophotometer. For time-resolved fluorescence measurements, the fluorescence signals were collimat-ed and focused onto the entrance slit of a monochro-mator with the output plane equipped with a photomul-tiplier tube (HORIBA HuoroMax-4P). The decays were analyzed by least-squares. The quality of the exponential fits was evaluated by the goodness offit (x2).
Synthesis of L. To construct new coordination complexes with specific structures and properties, a multidentate ligand (L) containing pyridyl group has been designed and synthesized.
Intermediate (M) (0.97 g, 1.5 mmol) and t -BuOK (0.84 g, 7.50 mmol) was placed into a dry mortar and milled into powder, then 2-naphthaldehyde (0.23 g, 1.47 mmol) was added and milled vigorously [15, 16]. After completion of the reaction (monitored by thin layer chromatography (TLC), the mixture was dispersed in 100 mL dichloromethane. The filtrate was washed with water for three times and organic phase was dried with anhydrous magnesium sulfate. The filtrate was concentrated and 30 mL is o-propanol was added. Gray solid was gained after the suction filter, then the crude product was recrystallized by ethylace-tate, 0.52 g creamy white solid was obtained, the yield was 75.3%.
1H NMR (400 MHz; CD2CCl2; TMS; 8, ppm): 7.33-7.41 (m., 3H), 7.45-7.51 (m., 3H), 7.56 (t., 2H, J = 7), 7.76 (d., 2H, J = 7.6), 7.81-7.93 (m., 8H), 8.08 (s., 1H), 8.25 (d., 2H, J = 7.6), 8.70-8.75 (m., 3H). 13C NMR (100 MHz; CDCl3; TMS; 8, ppm: 117.66, 118.51, 122.25, 123.48, 124.14, 126.06, 126.41, 126.98,
127.13, 127.21, 127.61, 127.73, 128.08, 128.18, 128.40, 128.80, 129.25, 129.85, 133.17, 134.62, 137.28, 138.34, 139.28, 147.77, 149.80, 155.42, 157.44.
FT-IR (v, cm-1): 3448 w, 3055 m, 2026 w, 1686 w, 1600 v.s, 1584 s, 1567 s, 1543 s, 1513 s, 1498 s, 1451 m, 1473 s, 1391 v.s, 1261 m, 1124 m, 1075 m, 963.4 v.s, 856 v.s, 826 s, 792 s, 772 s, 753 s, 734 m, 695 s, 681 m, 618 m, 537 s, 516 w. LDI-TOF MS: m/z = 460.96 ([M + 1]+
C34H24N2 requires 460.19).
Synthesis of complex I. A methanol solution (15 mL) of ZnI2 (0.016 g, 0.05 mmol) was added to a dichloromethane solution (15 mL) of L (0.0230 g, 0.05 mmol). The clear mixture solution was left to evaporate slowly at room temperature for a few days, and pale yellow, block shape crystals of I suitable for single crystal X-ray diffraction were obtained. The yield was 28.4 mg (73%).
For C34H24N2I2Zn anal. calcd., %: Found, %:
C, 52.37; H, 3.10; N, 3.59. C, 52.35; H, 3.12; N, 3.60.
FT-IR (v, cm-1): 3448 w, 3052 w, 2346 w, 2026 w, 1599 v.s, 1540 s, 1485 v.s, 1459 w, 1445 w, 1429 w, 1399 s, 1365 m, 1241 m, 1123 m, 1063 m, 1024 m , 967 s, 893 w, 853 s, 821 s , 770 s, 750 s, 738 s, 670 v.s, 681 m, 651 m, 613 w, 536 m, 503 w, 478 m.
Synthesis of complex II. The reaction was carried out using ZnCl2 in the same method for I, and the pale yellow, needle-like crystals of II suitable for single crystal X-ray diffraction were obtained. The yield was 26.9 mg (79%).
For CTOH52N4Cl8Zn2
anal. calcd., %: Found, %:
C, 61.66; C, 61.75;
H, 3.84; H, 3.80;
N, 4.11. N, 4.13.
FT-IR (v, cm-1): 3444 w, 3054 m, 2352 w, 2026 w, 1599 v.s, 1584 s, 1538 s, 1513 s, 1486 m, 1470 m, 1445 m, 1416 w, 1391 v.s, 1259 m, 1124 s, 1072 s, 1024 m , 963 v.s, 856 v.s, 826 v.s, 791 s, 752 s, 697 s, 681 m , 640 m, 615 m, 537 s, 516 w, 485 w.
Table 1. Crystalloraphic data and structure refinement for I and II
Parameter Value
I II
Formula weight 779.72 681.75
Crystal system Tetragonal Triclinic
Space group P43212 PI
a, A 13.901(4) 13.6254(17)
b, A 13.901(3) 13.7778(17)
c, A 31.497(2) 18.119(2)
a, deg 90 87.596(2)
P, deg 90 88.320(2)
Y, deg 90 67.961(2)
V, A3 6086(2) 3149.7(7)
Z 8 4
P calcd g cm-3 1.702 1.438
p., mm-1 2.861 1.147
9, Range, deg 1.60-25.55 1.12-25.00
F(000) 3024 1392
Reflections collected/unique 45052/5658 22546/10982
Rint 0.0560 0.0314
GOOF on F 2 1.023 0.958
Final R indices (I> 2ct(T)) R1 = 0.0838 R1 = 0.0838
wR2 = 0.2450 wR2 = 0.2450
R indices (all data) R1 = 0.1374 R1 = 0.1374
wR2 = 0.3058 wR2 = 0.3058
^max^mim « A~3 1.248/—1.126 1.737/—0.862
Synthesis of complex III. By the same method with using of ZnBr2, we obtained the complex III.
The yield was 27.8 mg (81%).
For C34H24N2Br2Zn
anal. calcd., %: Found, %:
C, 59.55; C, 59.56;
H, 3.53; H, 3.64;
N, 4.08. N, 4.23.
FT-IR (v, cm-1): 3443 w, 3055 m, 2926 w, 2026 w, 1795 w, 1600 v.s, 1538 m, 1485 m, 1445 w, 1391 m, 1242 w, 1123 m, 1070 m, 1025 w, 963 m, 870 w, 855 w, 825 m, 790 m, 772 w, 699 m, 681 w, 640 w, 615 w, 538 m, 517 w, 477 w.
From the elemental analysis result, we can infer the unit of this compound contains only one ZnLBr2 molecule.
X-ray crystallography. X-ray diffraction data of single crystals were collected on a Siemens Smart 1000 CCD diffractometer. Determination of unit cell paramete
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