DOI: 10.1021/cg900031c
New Ionic Liquids of N,N0 -Dialkylbenzimidazolium Salt Comprising Copper(II) Ions
2009, Vol. 9 3934–3940
KeFei Wang,†,‡ FangFang Jian,*,†,‡ RuiRui Zhuang,‡ and HaiLian Xiao§,‡ †
Microscale Science Institute, Weifang University, Weifang 261061, P. R. China, ‡New Materials and Function Coordination Chemistry Laboratory, Qingdao University of Science and Technology, Qingdao Shandong 266042, P. R. China, and §College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao Shandong 266042, P. R. China Received January 12, 2009; Revised Manuscript Received July 21, 2009
ABSTRACT: Three new metal-containing ionic liquids (ILs) of N,N0 -dialkylbenzimidazolium of [(CnH2nþ1)2-bim]2[CuCl4] (n=8, 10, 12) (bim=benzimidazole) were synthesized, and the structures were characterized by X-ray crystallography, IR spectroscopy, and elemental analysis. The cations of three complexes adopted U-shaped conformations and were packed in a bilayer fashion. The thermal behaviors of three complexes were studied by differential scanning calorimetry (DSC) and thermogravimetry (TG). The ionic conductivities measurements showed that the ionic conductivities of the three complexes were different in absolute ethanol, and the ionic conductivities may relate to the coordination environment found for Cu(II) of three complexes.
1. Introduction Ionic liquids (ILs) have attracted considerable attention as versatile media and materials due to their peculiar physicochemical properties.1 Ionic liquids are characterized by extremely low vapor pressures, wide liquid ranges, nonflammability, thermal stability, tunable polarity, good electrolytic properties, and easy recycling.2 ILs have attracted great interest as environmentally friendly solvents to replace volatile organic solvents in chemical reactions in the field of separations and manufacturing processes.3 ILs with different cations, such as ammonium, phosphonium, pyridinium, and imidazolium salts,1 have been described in the literature. Among these, imidazolium salts are some of the most frequently studied.1,4 This is due to the use of imidazolium salts as ligand precursors in the synthesis of metalcarbene complexes,5 which are excellent catalysts in many chemical reactions.6 Benzimidazolium as derivatives of imidazolium may possess the nicest properties of imidazolium. Furthermore, the ILs of N,N0 -benzimidazolium salts used in catalytic systems7 increasingly have aroused people’s attention. However, only a few crystal structures of 1,3-dialkylbenzimidazolium chlorides and bromides have been reported.8 By incorporating metal ions to ILs, metal-containing ILs can be formed.9 The presence of metal ions in ILs provided many additional properties such as color, geometry, and magnetiszm. Bolkan and Yoke10 observed the formation of a copper(I)based room temperature IL system of [emim]Cl-CuCl (emim = 1-ethyl-3-methylimidazole). Spectroscopic studies showed that a broad variety such as [CuCl3]2-, [Cu2Cl3]-, [CuCl4]- and polynuclear complexes CumCln(n-m)- were formed. However, these systems were found to be oxygen sensitive. Sundermeyer’s group reported copper(II) containing ILs formulated as [bmim]2[Cu3Cl8]11 (bmim = 1-butyl-3-methylimidazole). A [(Cn)2-im]Cl/[CuCl] system consisting of various chlorocuprates viz., [CuCl2]-, [Cu2Cl3]-, and [Cu3Cl4]- was also prepared for catalyst.12 Metal-containing ionic liquid crystals of N, *To whom correspondence should be addressed. E-mail: ffj2003@163169. net. pubs.acs.org/crystal
Published on Web 08/10/2009
N0 -dialkylimidazolium salts of Pd(II) and Cu(II) were prepared for liquid crystals and catalyst.13 Sasaki et al. prepared14 groups of metal ion-containing ionic liquid catalysts, and only the immobilized copper catalyst [bmim]2[CuCl4], which had a sandwiched [CuCl4]2- moiety, was very active for the kharasch reaction between styrene and CCl4. Naik et al. reported15 salicylaldoxime and salen containing imidazolium ionic liquids form ionic metal complexes with copper and manganese for their biphasic catalysis and metal extractions. However, to the best of our knowledge, ILs reports on the corresponding benzimidazolium with different anions are lacking, and the studies of the metal-containing ILs are even scarcer. The significance of our research work is to report the synthesis, structure, and properties of three new metal-containing ionic liquids of N,N0 -dialkylbenzimidazolium of [(CnH2nþ1)2-bim]2[CuCl4] (n=8, 10, 12). Additionally, we pay particular attention to hydrogen bonds in the crystal structures and the coordination environment of three complexes. 2. Experimental Section 2.1. Chemicals and Measurement. All chemicals were of analytical reagent grade and used directly without further purification. Elemental analyses were measured with a Perkin-Elmer 1400C analyzer (USA). Infrared spectra were recorded on a Nicolet 170SX spectrometer (USA) using pressed KBr plates in the 4000-400 cm-1 ranges. Thermal gravity were recorded on an SDT 2980 simultaneously for the samples of ca. 10 mg under a nitrogen atmosphere (150 mL/min) at a heating rate of 10 °C/min. Phase transition temperatures were determined by differential scanning calorimetry at a scan rate of 10 °C/min using a Netzsch DSC 204 thermal analysis data station. Thermogravimetry (TG) were recorded on an SDT 2980 simultaneously for the samples of ca. 10 mg under a nitrogen atmosphere (150 mL/min) at a heating rate of 10 °C/min. The TG residues were examined using a X-ray diffraction (XRD, Rigaku, D-max-γ A XRD with Cu KR radiation, λ=0.15148 nm). Conductivity measurements were performed using DZS-707 multiparameter water quality analysis instrument (Shanghai Precision & Scientific Instrument Co., Ltd.). Conductivity cells were calibrated with a KCl solution. Water content was analyzed by Karl Fischer titration by the method presented in the Supporting Information. r 2009 American Chemical Society
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2.2. The Preparation and Physical Measurement of Three Complexes. Synthesis of [(C12H25)2-bim]2[CuCl4] (1a). Copper(II) chloride (87.6 mg, 0.5 mmol) and [(C12H25)2-bim]Cl (456 mg, 1 mmol) were dissolved in 30 and 10 mL of warm absolute alcohol, respectively. The [(C12H25)2-bim]Cl solution was slowly added to the copper(II) chloride solution with stirring. After the addition was completed, the solution was refluxed for 2 h. After cooling to room temperature, the resulting brown precipitate of 1a was obtained by filtration. Recrystallization from acetonitrile gave a yield of 78%. The C, H, and N contents were determined by elemental analysis (Anal. Calcd for C62H110Cl4CuN4(%) C 66.67, H 9.93, N 5.02; found: C 66.61, H 9.96, N 4.99). The [(C10H21)2-bim]2[CuCl4] 1b and [(C8H17)2-bim]2[CuCl4] 1c were prepared by a method similar to that of [(C12H25)2-bim]2[CuCl4]. 1b The C, H, and N contents were determined by elemental analysis (Anal. calcd. for C54H94Cl4CuN4 (%) C 64.55, H 9.43, N 5.58; found: C 64.51, H 9.45, N 5.56). 1c The C, H and N contents were determined by elemental analysis (Anal. calcd. for C46H78Cl4CuN4 (%) C 61.90, H 8.81, N 6.28; found: C 61.94, H 8.82, N 6.25). IR and Raman spectra are available as Supporting Information. In the IR spectra, the band at 3041 cm-1 may be assigned to the C-H stretching vibration of the phenyl ring of benzimidazole. The bands at 2920, 2851 cm-1 may be attributed to the C-H stretching vibration of the alkyl chains. Several bands appeared in the 1609-1465 cm-1 range, contributing from the stretching vibrations of the aromatic rings. The band at 1350 cm-1 was attributed to the C-N stretching vibration of imidazole ring. In Raman spectra, for 1a the shifts at 180, 275, 301 cm-1 showed square-planar [CuCl4]2- anions;16 for 1b the shifts at 248, 266, 271 cm-1 and for 1c the shifts at 243, 249, 267 cm-1 showed tetrahedral [CuCl4]2- anions.16a,17 Reflection data and reflections for the unit cell determination were measured at 20 °C using Mo KR radiation (λ = 0.71073 A˚) with a graphite monochromator. The structures of three title complexes were solved by direct methods and refined by least-squares on Fobs2 by using the SHELXTL18 software package. All non-hydrogen atoms were refined anisotropically, and the hydrogen atoms were placed in calculated position and allowed to ride on their parent atoms. The molecular graphics were plotted using SHELXTL. The graphics of crystal stacking and hydrogen bonds were drawn using mercury 2.2. Atomic scattering factors and anomalous dispersion corrections were taken from International Tables for X-ray Crystallography.19
3. Results and Discussion 3.1. Crystal Structures of the Title Complexes. The brown crystals of [(C12H25)2-bim][Cu0.5Cl2] 1a were obtained by slow evaporation from tetrahydrofuran at room temperature. The molecular structure of 1a with the atomic numbering scheme was shown in Figure 1. Crystal data and structure refinement are listed in Table 1. There were two independent cations of benzimidazolium in the molecular structure. Each cation was composed of two long hydrocarbon chains and a benzimidazolium head core and adopted a U-shaped conformation. The two-alkyl chains in the cation ran perpendicular to the benzimidazolium core plane in the same orientation, which was similar to that found in N,N0 -dialkylbenzimidazolium bromide.8 The angles of alkyl chains were 84.05° and 83.27° with the two arms pointing in the same direction. Each plane of benzimidazolium is connected side by side to the neighboring molecules through C-H 3 3 3 Cl hydrogen bonds, such that the aromatic rings lined up in a row with all the legs pointing in the same direction. The benzimidazolium cations were packed in a head-to-head fashion. The flat benzimidazole ring heads aligned parallel to the neighboring flat heads but faced those of an opposing layer. The metal containing anion, [CuCl4]2-, had regular square-planar geometry. The angles around the Cu(II) center were
Figure 1. (a) ORTEP drawing of the cation of 1a (30% thermal ellipsolids) with atomic numbering. (b) Stacking of the bilayered structure 1a. (c) Hydrogen bonds between the chloride anion and bim cations, the tail end of alkyl chains being omitted for clarity.
180.0°, Cl(2)#1-Cu(1)-Cl(1)#1 Cl(2)#1-Cu(1)-Cl(2) 90.10(4)°, Cl(2)-Cu(1)-Cl(1)#1 89.90(4)°, Cl(2)#1-Cu(1)Cl(1) 89.90(4)°, Cl(2)-Cu(1)-Cl(1) 90.10(4)°, Cl(1)#1-Cu(1)-Cl(1) 180.0°. The packing diagram of 1a is shown in Figure 1b. Each row further is connected with the other through hydrogen bonds to form a plane, like a tiled roof and again with all the legs pointing in the same direction. Interdigitation of two such planes with interpenetrating alkyl chains generated a bilayer of 19.8 A˚ thickness. Anions were not in the proximity of the positively charged N atoms; rather, each anion formed hydrogen bonds with five C-H groups [H(12A), H(24A), H(24B), H(25A), and H(27A)] from three neighboring bim planes (Figure 1c). If one considered each alkyl chain as a rod, the rods exhibited hexagonal close-packing and the distances between the neighboring rods were 4.1-4.6 A˚. As we know, noncovalent interactions are at the core of most chemical and biological processes, and hence knowledge of their nature, strength, occurrence, and consequences is of paramount importance.20 The weak noncovalent interactions
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Table 1. Crystal Data and Structure Refinement for 1a-1c complex
1a
1b
1c
empirical formula formula weight temperature (K) wavelength (A˚) crystal system space group a (A˚) b (A˚) c (A˚) R (°) β (°) γ (°) V (A˚3) Z calculated density (Mg 3 m-3) absorption coefficient (mm-1) F(000) theta range for data collection (°) limiting indices
C31H55Cl2Cu0.5N2 558.46 293(2) 0.71073 triclinic P1 8.979(2) 9.066(2) 19.995(4) 83.57(3) 84.83(3) 83.44(3) 1601.9(6) 2 1.158 0.546 607 2.06 to 25.50 -10 e h e 10 -9 e k e 10 -22 e l e 24 8913/5916 [Rint = 0.0268] 99.20 full-matrix least-squares on F2 5916/0/322 1.023 R1 = 0.0478 wR2 = 0.0955 R1 = 0.0825 wR2 = 0.1106 0.346 and -0.212
C54H94Cl4CuN4 1004.67 293(2) 0.71073 triclinic P1 8.870(2) 18.163(4) 18.328(4) 87.08(3) 82.90(3) 79.24(3) 2877(1) 2 1.160 0.601 1086 1.62 to 25.50 -10 e h e 10 -22 e k e 22 -22 e l e 22 31137/10699 [Rint = 0.0524] 99.8 full-matrix least-squares on F2 10699/0/569 1.069 R1 = 0.0812 wR2 = 0.2050 R1 = 0.0937 wR2 = 0.2151 2.163 and -0.824
C46H78Cl4CuN4 892.46 293(2) 0.71073 triclinic P1 8.858(2) 16.034(3) 18.300(4) 87.22(3) 79.02(2) 78.44(3) 2499.6(9) 2 1.186 0.684 958 1.29 to 28.34 -10 e h e 10 -19 e k e 19 -21 e l e 21 25762/8794 [Rint = 0.0464] 99.8 full-matrix least-squares on F2 8794/2/461 1.066 R1 = 0.0727 wR2 = 0.2547 R1 = 0.1029 wR2 = 0.2952 0.987 and -1.260
reflections collected/unique completeness (%) refinement method data/restraints/parameters goodness-of-fit on F2 final R indices [I > 2σ(I)] R indices (all data) largest diff. peak and hole (e 3 A˚-3)
such as C-H 3 3 3 X (X = O, N, S, halogen), π-π stacking, while weaker than the classical H-bonds, also play notable roles in conformation, crystal packing, supramolecular assembly, and physicochemical properties and thus have implications in drug design, material design, and supramolecular synthesis.20-22 There were some weak potentially C-H 3 3 3 Cl hydrogen bonds intermolecular interactions, and the donor and acceptor distances were in the range of 3.5-3.68 A˚, for C(12) 3 3 3 Cl(2) 3.6260 A˚, C(24) 3 3 3 Cl(2) 3.6270 A˚, C(24) 3 3 3 Cl(1) 3.6817 A˚, C(25) 3 3 3 Cl(1) 3.5814 A˚, C(27) 3 3 3 Cl(1) 3.6683 A˚, respectively. The H 3 3 3 Cl distances were in the range of 2.7-2.83 A˚, and were within the sum of the van der Waals radii (2.95 A˚) of H and Cl. There were three types π-π stacking interactions between imidazole rings and phenyl rings. The center-to-center distances were in the range from 3.509 to 3.729 A˚. The shortest interplanar distances above were in the range of 3.410 to 3.429 A˚. The crystals of [(C10H21)2-bim]2[CuCl4] 1b were obtained by slow evaporation from acetonitrile at room temperature. The molecular structure of 1b with the atomic numbering scheme was shown in Figure 2. There were two independent cations of benzimidazolium in the molecule. Each cation was composed of two long hydrocarbon chains and a benzimidazolium head core and adopted a U-shaped conformation. The space group of the 1b was identical to that of 1a. The bond lengths, bond angles, and the conformation of the cation were similar to those of 1a. However, the [CuCl4]2- anion adopted a distorted tetrahedral geometry, which was different from 1a. The angles around the Cu(II) center were Cl(4)Cu(1)-Cl(1) 144.59(6)°, Cl(4)-Cu(1)-Cl(2) 96.33(5)°, Cl(1)-Cu(1)-Cl(2) 94.85(6)°, Cl(4)-Cu(1)-Cl(3) 94.25(5)°, Cl(1)-Cu(1)-Cl(3) 94.48(6)°, Cl(2)-Cu(1)-Cl(3) 146.82(5)°. The packing diagram of 1b was shown in Figure 2b. There were two alternating layers with distances of 17.9 A˚ in the crystal packing. Like the structure of 1a, extended H-bonds
between the [CuCl4]2- chlorides and the ring were observed in Figure 2. There were some weak potentially C-H 3 3 3 Cl hydrogen bonds intermolecular interactions, and the donor and acceptor distances were in the range of 3.4-3.72 A˚, for C(10) 3 3 3 Cl(3) 3.6048 A˚, C(20) 3 3 3 Cl(2) 3.6061 A˚, C(21) 3 3 3 Cl(1) 3.5948 A˚, C(26) 3 3 3 Cl(2) 3.6846 A˚, C(37) 3 3 3 Cl(4) 3.6472 A˚, C(47) 3 3 3 Cl(4) 3.7296 A˚, C(48) 3 3 3 Cl(4) 3.4533 A˚, C(53) 3 3 3 Cl(4) 3.5983 A˚, respectively. The H 3 3 3 Cl distances were in the range of 2.6-2.79 A˚, and were within the sum of the van der Waals radii (2.95 A˚) of H and Cl. There were three types π-π stacking interactions between imidazole rings and phenyl rings. The center-to-center distances were in the range from 3.692 to 3.786 A˚. The shortest interplanar distances above were in the range of 3.450 to 3.475 A˚. The crystals of [(C8H17)2-bim]2[CuCl4] 1c were obtained by slow evaporation from ethanol at room temperature. The molecular structure of 1c with the atomic numbering scheme was shown in Figure 3. There were two independent cations of benzimidazolium in the molecule. Each cation was composed of two long hydrocarbon chains and a benzimidazolium head core and adopted a U-shaped conformation. The space group of 1c also was identical to that of 1a and 1b. The bond lengths, bond angles, and the conformation of the cation were similar to those of the 1a. However, the CuCl42- anion adopted a distorted tetrahedral geometry, which was different from 1a. The angles around the Cu(II) center were Cl(3)-Cu(1)-Cl(1) 141.93(8)°, Cl(3)-Cu(1)Cl(4) 94.76(6)°, Cl(1)-Cu(1)-Cl(4) 94.72(7)°, Cl(3)-Cu(1)-Cl(2) 98.18(7)°, Cl(1)-Cu(1)-Cl(2) 95.64(7)°, Cl(4)Cu(1)-Cl(2) 143.65(8)°. The packing diagram of 1c was shown in Figure 3. There were two alternating layers with distances of 15.7 A˚ in the crystal packing. Like the structure of 1a, extended H-bonds between the CuCl42- chlorides and the ring were observed in Figure 3. There were some weak potentially C-H 3 3 3 Cl hydrogen bonds intermolecular
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Figure 2. (a) ORTEP drawing of the cation of 1b (30% thermal ellipsolids) with atomic numbering. (b) Stacking of the bilayered structure 1b. (c) Hydrogen bonds between the chloride anion and bim cations, the tail end of alkyl chains being omitted for clarity.
interactions and C-H 3 3 3 N intramolecular interactions, and the donor and acceptor distances were in the range of 2.93.70 A˚, for C(8) 3 3 3 Cl(2) 3.598 A˚, C(16) 3 3 3 Cl(4) 3.657 A˚, C(17) 3 3 3 Cl(1) 3.591 A˚, C(19) 3 3 3 Cl(4) 3.726(7) A˚, C(29) 3 3 3 N(3) 2.996 A˚, C(31) 3 3 3 Cl(3) 3.672 A˚, C(37) 3 3 3 N(4) 2.924 A˚, C(39) 3 3 3 Cl(3) 3.704 A˚, C(40) 3 3 3 Cl(3) 3.474 A˚, C(42) 3 3 3 Cl(3) 3.588 A˚, respectively. The H 3 3 3 Cl distances were in the range of 2.5-2.83 A˚, and were within the sum of the van der Waals radii (2.95 A˚) of H and Cl. The hydrogen bonds of 1a-1c showed some characteristics; the donor and acceptor distances of 1a and 1b were similar, while that of 1c was shorter than 1a and 1b. The H 3 3 3 Cl distances of 1a-1c were similar, but the H 3 3 3 Cl distances of 1c were shortest. There were six types π-π stacking interactions between imidazole rings and phenyl rings. The center-to-center distances were in the range from 3.694 to 3.954 A˚. The shortest interplanar distances above were in the range of 3.381 to
3.499 A˚. In the solid state, the intermolecular interactions in this structure stabilized the crystal structure. 3.2. Thermal Behavior. For all the complexes, the thermal behavior and phase transition temperatures were investigated by differential scanning calorimetry (DSC) and thermal gravity (TG). DSC was performed in air at a heating rate of 10 °C/min. To avoid possible effects of hydration of the materials, all were dried under a vacuum before DSC analyses. The phase transition temperature and the corresponding enthalpy changed derived for complexes 1a-1c are displayed in Figure 4. Complexes 1a, 1b, and 1c exhibited two endothermic transitions in the heating cycle. For 1a the first transition was one peak with a total ΔH value of 5.14 kJ/mol at 90.5 °C, and the second transition peak had a ΔH value of 15.42 kJ/ mol at 110.4 °C. For 1b the first transition was one peak with a total ΔH value of 13.65 kJ/mol at 83.5 °C, and the second
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Figure 3. (a) ORTEP drawing of the cation of 1c (30% thermal ellipsolids) with atomic numbering. (b) Stacking of the bilayered structure 1b. (c) Hydrogen bonds between the chloride anion and bim cations, the tail end of alkyl chains being omitted for clarity.
transition peak had a ΔH value of 49.15 kJ/mol at 105.4 °C. For 1c the first transition was one peak with a total ΔH value of 26.57 kJ/mol at 96.4 °C, and the second transition peak had a ΔH value of 51.63 kJ/mol at 136.5 °C. 1a and 1b exhibited only one exothermic transitions in the cooling cycle process, and the subsequent cooling and heating processes can give reproducible results. Complexes 1c exhibited two exothermic transitions in the cooling cycle process, and the subsequent cooling and heating processes can give
reproducible results. For 1a exothermic transitions were at 55.4 °C with the ΔH value of -19.23 kJ/mol, and for 1b exothermic transitions were at 80.7 °C with the ΔH value of -57.26 kJ/mol, respectively. 1c exothermic transitions were at 117.2 and 71.5 °C with the ΔH value of -35.11 kJ/mol and -40.63 kJ/mol, respectively. All 1a-1c were checked on hot stage microscopy, but there were no mesophases observed. We think the enthalpy changes may be one crystal phase changing to another. Thermal stability of 1a-1c was also
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liquids were higher than their ligands, and 1b and 1c accorded with this law. The reason that the conductivity of 1a was lower than its ligand L1 may be the different coordination environment. The coordination environment of 1b and 1c were tetrahedron while that of 1a was squareplanar, although there was no evidence indicating the tetrahedral metal-containing ionic liquids were higher than that of square-planar. The high conductivities showed that those ionic liquids may be useful in electroanalysis chemistry. 4. Conclusions
Figure 4. DSC result curves (10 °C/min) of 1a-1c.
The synthesis, structural characterization, and conductivities of three new ionic liquids [(CnH2nþ1)2-bim]2[CuCl4] (n=8, 10, 12) had been established. The crystal structures of the three complexes had revealed that the cation adopted U-shaped conformation and were packed in a bilayer fashion. The coordination environment of 1a was square-planar, while that of 1b and 1c were tetrahedron. The DSC analysis and TG/ DTG of three complexes 1a-1c showed the general stability order to be 1a < 1b < 1c, which meant that the stability of three complexes decreased with the alkyl chain increasing. The conductivities of 1b and 1c were higher than their ligands, while the conductivity of 1a was lower than the corresponding ligand. On the basis of their properties, the new ionic liquid materials may have applications in chromatography, organic synthesis, self-assembly media, and electrochemistry. Acknowledgment. This work was supported by the Natural Science Foundation of Shandong Province (No.Y2007BS04046 and Y2006B08), P. R. China. Supporting Information Available: Crystal data of compounds 1a, 1b, and 1c. This material is available free of charge via the Internet at http://pubs.acs.org.
Figure 5. Curves of conductivities of 1 10-3 M 1a-1c and their ligands (L1, L2, L3) in absolute alcohol solution with temperature increasing.
confirmed by thermogravimetry (TG) and the first decomposition points of 1a-1c were 194, 205, and 248 °C, respectively. The results showed the general stability order to be 1a < 1b < 1c, which meant that the stability of those complexes decreased with the alkyl chain increasing. That may be attributed to the distance of molecular layer increasing with the alkyl chain increasing, and as a result the intermolecular force decreased. 3.3. Conductivity. Because the melting points of 1a-1c were relatively high, it was difficult to study their conductivities by pure compounds according to the Vogel-TammanFulcher (VTF)-type equation.23 As a result, it had to be studied in absolute alcohol solution. The conductivities of 1 10-3 M 1a-1c and their ligands (L1, L2, L3) were measured using a conventional conductivity cell as described below (Figure 5). In order to elucidate the conductivities, those complexes were measured in absolute alcohol from 25 to 90 °C. The conductivities of all those complexes increased with the increased temperature. The conductivities of three ligands (L1, L2, L3) were similar. The conductivities of 1b and 1c were similar and higher than their ligands L2 and L3. But the conductivity of 1a was lower than its ligand L1. It showed that the conductivities were affected by alkyl chain and the anions and the influence by alkyl chain was relative small. Generally the conductivities of metal-containing ionic
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