Self-assembly of imidazoliums salts based on acridine with silver oxide as coordination polymers: Synthesis, fluorescence and antibacterial activity

Journal of Organometallic Chemistry 797 (2015) 67e75

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Self-assembly of imidazoliums salts based on acridine with silver oxide as coordination polymers: Synthesis, fluorescence and antibacterial activity Zhan He a, Kun Huang b, Fang Xiong a, Shu-Fang Zhang a, Jun-Ru Xue a, Yue Liang a, Lin-Hai Jing a, Da-Bin Qin a, * a

Key Laboratory of Chemical Synthesis and Pollution Control of Sichuan Province, School of Chemistry and Chemical Engineering, China West Normal University, Nanchong 637002, PR China School of Chemistry and Chemical Engineering, Sichuan University of Arts and Science, Dazhou 635000, PR China

b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 20 April 2015 Received in revised form 17 July 2015 Accepted 20 July 2015 Available online 8 August 2015

The reaction of iodomethane, n-butane bromide, bromoethane, benzyl bromide and 9-(1-imidazolyl) acridine obtains the corresponding imidazolium salts, which can further react with NH4PF6, affording 2a e2d. Then, they were treated with silver oxide in CH3CN or DMSO to afford complexes 3ae3d ({Ag [1acridinyl-3-methylimidazoly-diene]2 (PF6)} (3a), {Ag [1-acridinyl-3-butylimidazoly-diene]2 (PF6) CH3CN} (3b), {Ag [1-acridinyl-3-ethylimidazolydiene] (PF6)}n (3c), {Ag [1-acridinyl-3-benzylimidazoly-diene] (PF6)}n (3d)). 3a and 3b formed mononuclear silver complexes which presented p
p stacking interactions between acriding rings. Amazingly, 3c and 3d formed one-dimensional coordination polymers through self-assembly of N1eAg1eC16 and N1eAg1eC14 bonds, respectively. Moreover, 3b, 3c and 3d have been found to have efficient anti-bacterial activity against the Acinetobacter baumannii and P. aeruginosa. In addition, the imidazolium salts and their corresponding silver complexes show a phenomenon of fluorescence quenching. © 2015 Elsevier B.V. All rights reserved.

Keywords: NHC Acridine derivatives Silver-NHC complexes Antibacterial activity

1. Introduction Since the first isolation of free N-heterocyclic carbene (NHC) in 1991 [1], NHCs have been developed rapidly in organometallic chemistry [2]. As the NHCs' strong s-donor, most of which can lead to stable metal-NHCs with strong metal-carbon bonds. Metal-NHCs are more efficient and more excellent stability toward air and moisture in many catalytic reactions compared with phosphinemetal complexes [3,4]. Several strategies which including the reaction metal compounds with free carbene [5], transmetalation reaction [6], the direct reaction of metal precursors with imidazolium salts [6,7] and electrolysis [8] for the synthesis of metal NHC complexes have been described. However, the direct reaction of the metal complex with the free carbene is the most general method, generally obtained by deprotonation of the imidazolium salt, or the transmetalation reaction with silver(I) NHC complexes, which is the favorite for metal NHC complexes.

* Corresponding author. E-mail address: [email protected] (D.-B. Qin). http://dx.doi.org/10.1016/j.jorganchem.2015.07.030 0022-328X/© 2015 Elsevier B.V. All rights reserved.

Up to now, metal-NHCs have revealed their intriguing structural properties and numerous applications in medicine, nanomaterial, catalysis [9]. Additionally, their potential applications in fluorescent switch [10], antibacterial activity [11], anticancer [12] and antiparasitic therapy [13] have been received increasing attention. Recently, the synthesis of metalllosupermolecular through selfassembly of metal-NHC has also attracted scientists' great interest [14]. Gimeno et al. have reported several imidazolium salts and silver-NHC complexes containing acridine group [6b]. However, metal-NHCs containing acridine group are rarely reported [15]. For the sake of exposing the structure of more metal-NHCs contain acridine. Herein, we report the preparation of the new imidazolium salts and metal-NHC complexes containing the acridine group. The cations of 2a, 2d, and 3a were analogously reported by Gimeno et al. In our works, 3a and 3b formed mononuclear silver complexes which shown p
p stacking interactions between acriding rings. To our surprise, 3c and 3d formed 1D polymeric chain through self-assembly of N1eAg1eC16 and N1eAg1eC14 bonds, respectively. In addition, the optical properties of the imidazolium salts and the silver complexes were researched. More

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importantly, the efficient antibacterial activities against the Acinetobacter baumannii and Pseudomonas aeruginosa of AgeNHCs have been studied. 2. Result and discussion

addition, an interesting phenomenon in the packing diagrams of 2b is that aromatic pep stacking interactions are observed [18]. Two types of pep interactions for face to face and edge to face are observed in Fig. 2 (center to center and edge to center distances: 3.5753 Å and 3.6167 Å, respectively), which lead to the formation of 2-D supramolecular layer (Fig. 2).

2.1. Synthesis and characterization of the imidazolium salts 9-(1-imidazolyl) acridine is prepared from imidazole and 9Chloroacridine by NaH as base and powder of copper as catalyst [16]. A high yield is obtained compared to the literature procedure [17]. Compounds (2ae2d) were synthesized according to the traditional procedure [15b] (Scheme 1). Additionally, (2ae2d) were characterized by 1H NMR, 13C NMR spectroscopy and elemental analyses. In 1H NMR spectrum of 2ae2d, the chemical shift for the imidazolium, acridine, methylene and methyl protons could be observed (in Supporting Information). The resonances signals (2a: 9.75 ppm, 2b: 9.84 ppm, 2c: 9.90 ppm, 2d: 9.93 ppm) corresponding to the NCHN imidazolium proton were found (in Supporting Information), which were confirmed the structures of 2ae2d. The yellow crystal of 2b was grown by slow diffusion of Et2O into CH3CN solution at room temperature, which had been confirmed by X-ray diffraction. The solid-state molecular structure is depicted in Fig. 1. In molecular structure of 2b, the imidazole ring and its adjacent acridine ring form a dihedral angel of 64.93 . C14eH14 … N1 hydrogen bond links the two cations into dimeric unit. In

2.2. Synthesis and characterization of the complexes Complexes (2ae2d) were treated with silver oxide (Ag2O, 0.6 mol equivalent) in CH3CN or DMSO to afford complexes (3ae3d) (Scheme 2), respectively. Moreover, (3ae3d) were characterized by 1 H NMR, 13C NMR spectroscopy and elemental analyses. In the 1H NMR spectrum of complexes 3ae3d, the signals for NCHN imidazolium proton has been disappeared, which have confirmed the formation of the silver-NHCs. Additionally, in the 1H NMR and 13C NMR spectra an interesting phenomenon was found that the chemical shifts of the methyl for 3a and methylene for 3b moved toward high magnetic field compared to their precursors, this can be attributed to the shielding effect of acridine. As is known to us, many influencing factors can result in the difference of metal complexes structures, but ligand and solvent are generally regarded as the primary factors [19]. Complexes 3ae3d were obtained in two different kinds of structural types, which could be ascribed to the reason that nitrogen atom of acetonitrile coordinated to metal atom of metal NHCs.

Scheme 1. Synthesis of the imidazolium salts.

Fig. 1. ORTEP diagram of 2b with 50% probability ellipsoids. Most hydrogen atoms are omitted for clarity. Selected bond distances (Å) and angles (deg): N1AA-C6AA 1.3518, C1AAN2AA 1.1360, C14A-H14A 0.9500, and C16A-N3AA-C17A 119.45.

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Fig. 2. Stack diagram of 2b.

Scheme 2. Synthesis of the complexes 3ae3d.

2.3. X-ray structure description The yellow crystals of 3ae3d suitable for X-Ray diffraction were grown by slow diffusion of Et2O into CH3CN solution. The molecular structures of complexes 3ae3d have been determined by X-ray diffraction. Crystallographic data of Complexes 2a, 3a, 3b, 3c and 3d were presented in Table 1. Molecular structures of 3a and 3b are depicted in Figs. 3 and 4. Complexes 3a and 3b are mononuclear silver complexes, which

afford trans-conformation. The two imidazole rings are almost coplane linking by C16eAg1eC16A and C16A-Ag1A-C16B bonds, with bond distances Ag1eC16 of 2.086(5) Å and Ag1A-C16A of 2.075(2) Å in 3a and 3b, respectively. The dihedral angels between acridine ring and its adjacent imidazole rings are 68.69 and 63.87 in 3a and 3b, respectively. As shown in Figs. 5 and 6, aromatic pep stacking interactions (face to face) are observed in the packing diagrams of 3a and 3b [18,20] (center to center distances: 4.4787 Å in 3a, 3.7675 Å in 3b). In crystal structure of 3b, Two CH3CN lay at the

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Table 1 Summary of X-ray crystallographic data for complexes 2a, 3a, 3b, 3c and 3d.

a

Compound

2b

3a

3b

3c

3d

Formula Formula weight Crystal system Space group Length a (Å) Length b (Å) Length c (Å) a (deg) b (deg) g (deg) V (Å3) Z Dcaled (g cm
3) Absorption coefficient F (000) Qmin, Qmax T (K) No. of data collected No. of unique data No. of refined parameters Goodness of fit on F2 Final R indices [(I > 2s(I)] R indices (all data)

C20H20F6N3P 447.36 Monoclinic P2(1)/c 13.285(3) 16.926(3) 9.0655(17) 90.00 105.976(2) 90.000 1959.8(6) 4 1.516 0.208 920 3.19, 27.49 293(2) 4454 3303 332 1.002 R1 ¼ 0.0468, uR2 ¼ 0.0902 R1 ¼ 0.0665, uR2 ¼ 0.1005

C34H28AgF6N6OP 787.45 Triclinic P-1 9.736(5) 9.817(4) 9.893(5) 69.73(2) 87.82(3) 69.71(2) 828.3(7) 1 1.579 0.729 396 2.20, 25.02 113(2) 2917 2828 269 1.262 R1 ¼ 0.0526, uR2 ¼ 0.1484 R1 ¼ 0.0513, uR2 ¼ 0.1480

C40H38AgF6N6P 865.13 Triclinic P-1 8.5210(19) 11.131(3) 11.153(3) 102.023(2) 103.927(2) 101.140(3) 970.6(4) 1 1.480 0.627 441 3.10, 26.00 293(2) 3710 3528 262 1.003 R1 ¼ 0.0314, uR2 ¼ 0.0695 R1 ¼ 0.0333, uR2 ¼ 0.0709

C22H25AgF6N3OP 600.29 Monoclinic P2(1)/c 12.444(3) 11.648(2) 16.912(3) 90.00 107.93(3) 90.00 2332.4(8) 4 1.709 1.001 1208 2.16, 25.02 293(2) 4101 3825 310 1.089 R1 ¼ 0.0394, uR2 ¼ 0.1150 R1 ¼ 0.0420, uR2 ¼ 0.1169

C25.5H26AgF6N3O2P 659.33 Monoclinic P2(1)/c 13.3663 11.7704 17.5834 90.000 98.565 90.000 2735.5(10) 4 1.601 0.090 1328 2.09, 25.02 293(2) 4798 4407 442 1.152 R1 ¼ 0.0423, uR2 ¼ 0.1238 R1 ¼ 0.0460, uR2 ¼ 0.1268

R1 ¼ SFoj
jFcjj=jSjFoj. bwR2 ¼ ½SwðFo2
Fc2 Þ2 =SwðFo2 Þ2 1=2

Fig. 3. ORTEP diagram of 3a with 50% probability ellipsoids. Most hydrogen atoms are omitted for clarity. Selected bond distances (Å) and angles (deg): Ag1eC16 2.086(5), N1eC7 1.347(7), and C16eAg1eC16 180.00(1).

two sides of Ag atom through weak bond of Ag1A … N4CA (Fig. 4). In the 1H NMR spectrum of 3b, the chemical shift of acetonitrile (CH3CN) at 2.0 ppm can be found (in Supporting Information), which can illustrate the presence of acetonitrile (CH3CN). The solid-state molecular structures of 3c and 3d are presented in Figs. 7 and 8. X-ray structure analysis revealed that the asymmetric unit contains one silver atom, one acridine ring and an imidazole ring. In molecular structures of 3c and 3d, silver atoms are coordinated to nitrogen atoms of acridings and carbon atoms of imidazoles. The bond lengths Ag1eC16 and Ag1eC14 of 3c and 3d are 2.049(4) Å and 2.073(4) Å, separately. Additionally, the Ag1eN1 distances of 3c and 3d (3c: 2.132(3) Å, 3d: 2.157(3) Å) are much

shorter than related reported [9d], which illustrating the AgeN bond here is much stronger. Moreover, in molecular structures 3c and 3d, the dihedral angels between the imidazole and acridine ring are 66.47 and 88.34 , respectively. The dihedral angel is 76.69 between benzene and acridine ring of 3d. Furthermore, the angels of N1eAg1eC16 for 3c and N1eAg1eC14 for 3d are 173.53 and 169.51, respectively. Amazingly, 3c and 3d afford to onedimensional zigzag type chain coordination polymers. In the two polymeric molecules 3c and 3d, the three adjacent silver atoms result in the formation of isosceles triangles with Ag … Ag waist lengths (3c: 7.0723 Å, 3d: 6.7525 Å), and the angels of Ag … Ag … Ag are 110.87 for 3c and 121.27 for 3d, respectively. Up to now, the

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Fig. 4. ORTEP diagram of 3b with 50% probability ellipsoids. Most hydrogen atoms are omitted for clarity. Selected bond distances (Å) and angles (deg): N2AA-C13B 1.433(3), N1AAC6AA 1.349(3), Ag1A-C16A 2.075(2), C16A-Ag1A-C16B 180.00.

Fig. 5. Stack diagram of 3a.

Fig. 6. Stack diagram of 3b.

1-D chain structure of silver NHCs are rarely known in related literature. 2.4. Optical properties The photoluminescence properties of 2ae2d and 3ae3d have been studied in CH3CN and H2O (VCH3CN:VH2O ¼ 1:1) at room

temperature depicted in Fig. 9. All of the imidazolium salts and silver-NHC complexes show a similar emission spectrum and excitation wavelength is 356 nm. As is shown in Fig. 9, the fluorescence intensity of all silver-NHC complexes is weaker than that of their corresponding imidazolium salts in 380e500 nm, which can be attributed to the photoinduced electron transfer (PET) process of the lone-pair electron of the nitrogen atom to the

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Fig. 7. ORTEP diagram of 3c with 50% probability ellipsoids. Most hydrogen atoms are omitted for clarity. Selected bond distances (Å) and angles (deg): Ag1eC16 2.049(4), Ag1eN1 2.132(3), and N1eAg1eC16 173.53.

Fig. 8. ORTEP diagram of 3d with 50% probability ellipsoids. Most hydrogen atoms are omitted for clarity. Selected bond distances (Å) and angles (deg): Ag1eC14 2.073(4), Ag1eN1 2.157(3), and N1eAg1eC14 169.51.

Fig. 9. Emission spectra of 2ae2d (solid line) and 3ae3d (dash line) in VCH3CN:VH2O ¼ 1:1 (1.0  10
6 M) solution upon excitation at 356 nm.

acridine ring [21]. Additionally, a pronounced blue shift can be obtained for 3ae3d compared to their precursors, which may well illustrate pep stacking interactions [22] arising from acidine rings.

2.5. Antibacterial properties Antibacterial activities of the Silver-NHC complexes were confirmed through using agar dilution process recommended by

Z. He et al. / Journal of Organometallic Chemistry 797 (2015) 67e75

the Clinical and Laboratory Standards Institute [23,24]. Minimal inhibitory concentrations (MIC) for silver complexes were tested against standard bacterial strains; A. baumannii (ATCC 19606), P. aeruginosa (ATCC 27853) were obtained from commercial supplies and the fungal strains A. baumannii (AB1-AB14), P. aeruginosa (PA1PA7, PA9) were obtained from North Sichuan Medical College Affiliated Hospital. Standard bacterial strains and the fungal strains taken out from the fridge were subcultured on Muller Hinton Broth. The solution of Silver-NHC complexes was prepared in acetonitrile (CH3CN). The concentrations measured complexes were 512, 256, 128, 64, 32, 16, 8, 4, 2 and 1 mg ml
1. Ciprofloxacin was used as antibacterial standard drugs whose MIC values (3.12 mg ml
1) were offered in literature [11c]. Then the bacterial strains were inoculated to the surface of agar plates contain broth by Multipoint inoculation instrument. After that all the inoculated agar plates were incubated at 37  C, the results were obtained after 24 h. In addition, the acetonitrile (CH3CN) without silver complex was done the same operation under similar conditions. The minimum concentration for the complexes which stopped visible growth of all bacterial strains was considered to be the MIC values. We found that the acetonitrile could not restrain the growth of the bacterias. The MIC values of our silver-NHC complexes against A. baumannii and P. aeruginosa were summarized in Table 2. Antibacterial activity values were observed in silvereNHC complexes which were tested against bacteria and fungi at 32e8 mg ml
1 concentrations. As shown in Table 2, the results revealed that 3c exhibited the most effective activity with MIC values 8 and 32 mg ml
1 of AB 19606 and PA 27853, respectively [11c]. The MIC value 32 mg ml
1 of 3b against PA 27853 was similar to 3d, but 3b had the MIC value 16 mg ml
1 against AB 19606 different from 3d (32 mg ml
1). The antibacterial activities of silver-NHC complexes against AB1-AB14 and PA1-PA9 were also obtained (Table 2). 3c showed the most efficient activity against AB1-AB14 and PA1-PA9 with same MIC values of 8 mg ml
1 (AB3: 32 mg ml
1, PA2: 32 mg ml
1, PA7:16 mg ml
1). 3b presented a high activity against all bacterial strains with MIC values 16 mg ml
1. The least activity for 3d against AB1-AB14 and PA1-PA9 could be obtained with MIC values of

Table 2 Summary minimum inhibitory concentration (MIC) [mg ml
1] values of complexes 3b, 3c and 3d against different bacterial strains. Bacterial strain

3b

3c

3d

Quality control bacteria AB 19606 Quality control bacteria PA 27853 A. baumannii AB1 AB2 AB3 AB4 AB5 AB6 AB7 AB8 AB9 AB10 AB11 AB12 AB13 AB14 P. aeruginosa PA1 PA2 PA3 PA4 PA5 PA6 PA7 PA9

16 32 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16

8 32 8 8 32 8 8 8 8 8 8 8 8 8 8 8 8 32 8 8 8 8 16 8

32 32 32 32 32 32 32 32 32 32 32 16 32 32 16 32 32 32 32 32 32 16 16 16

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32 mg ml
1 (AB10 and AB13: 16 mg ml
1, PA6, PA7 and PA9: 16 mg ml
1). The antibacterial activities of our new silver-NHC complexes are higher than that of literature [11c]. 3. Conclusion In summary, new imidazolium salts containing the acridine group have been synthesized. The salt 2b (1-acridinyl-3butylimidazolium hexafluorophosphate salt) presents a bidimensional supermolecular structure through acridine ring face to face and edge to face pep stacking interactions. Four silver (I) NHCs which through the reaction of the imidazolium salts with Ag2O have been prepared. Mononuclear silver complexes 3a and 3b were obtained. However, 3c and 3d afforded to one-dimensional zigzag type chain coordination polymers. In addition, 3b, 3c and 3d have an efficient anti-bacterial activity against the A. baumannii and P. aeruginosa. Amazingly, 3c is found to show the most effective anti-bacterial activity. What's more, the fluorescence quenching phenomenon and blue shift of the imidazolium salts and their corresponding silver NHC complexes can be obtained. 4. Experimental 4.1. Antimicrobial activities Minimal inhibitory concentrations for every compound were tested against standard bacterial strains: A. baumannii (ATCC 19606), P. aeruginosa (ATCC 27853). They were obtained from commercial supplies. Otherwise, the fungal strains A. baumannii (AB1-AB14), P. aeruginosa (PA1-PA7, PA9) were obtained from North Sichuan Medical College Affiliated Hospital. The bacterial strains were inoculated to the surface of agar plates contain broth by Multipoint inoculation instrument. After that all the inoculated agar plates were incubated at 37  C, the results were obtained after 24 h. 4.2. General procedures All chemicals were obtained from commercial supplies and used without further purification. Melting point was determinated with a KY-XT6B. 1H and 13C NMR spectra were recorded on a Bruker 400 spectrometer (1H 400 MHz; 13C, 100 MHz). Chemical shifts are expressed in ppm to TMS. The fluorescence spectra were carried out in solution of CH3CN:H2O ¼ 1:2 at room temperature using RF5310 PC. 4.3. Synthesis of 9-(1-imidazolyl) acridine (1) Anhydrous 1,4-dioxidiane was added to mixture of imidazole (6.8 g, 100 mmol) and oil-free sodium hydride (2.4 g, 100 mmol) under nitrogen atmosphere and stired for 6 h at room temperature, then 9-(1-imidazolyl) acridine (4.26 g, 20 mmol) and copper (0.127 g, 2 mmol) were added to the suspension mixture. The mixture was continued to stir for 48 h at 130  C then cooled to room temperature. Solvent was removed under vacuum and water was added to the residue. The solution was extracted with CHCl3 (100 ml  3), and the extracting solution was dried with anhydrous MgSO4. Pure product was obtained through silica gel column Chromatography (ethyl acetate/petroleum ether, 1:1) as yellow solid. Yield: 4.10 g (83.5%), Mp: 220e222  C. Anal. Calcd for C16H11N3: C, 78.35; H, 4.52; N, 17.13%; Found: C, 78.31, H, 4.58, N, 17.16%. 1H NMR (CDCl3, TMS): d (ppm) 7.35e7.36 (t, 1H, J ¼ 1.26 Hz), 7.47e7.48 (t, 1H, J ¼ 1.08 Hz), 7.57e7.59 (m, 4H, Acr-H), 7.82e7.86 (m, 3H, Acr-H), 8.30 (t, 1H, J ¼ 0.90 Hz), 8.32e8.33 (t, 1H,

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J ¼ 0.90 Hz), 13C NMR (CDCl3, TMS): d (ppm) 149.23, 138.98, 138.33, 130.65, 130.10, 129.76, 127.59, 122.89, 122.46, 122.33. 4.4. Synthesis of 1-acridinyl-3-methylimidazolium hexafluorophosphate salt (2a) A solution of 1 (2.45 g, 10 mmol) and iodomethane (0.76 ml, 15 mmol) in tetrahydrofuran (THF) (150 ml) stirred for 12 h at 40  C and a yellow precipitate was formed. The yellow solid was obtained through filtration and washed with THF, then dissolved in methanol and the solution was added to the saturable solution of NH4PF6. Yellow pale precipitate was obtained though filtration again. The yellow crystal of 2a was obtained by recrystallization from CH3CN/Et2O. Mp: 214e216  C. Anal. Calcd for C17H14F6N3P: C, 50.38; H, 3.48; N, 10.37%; Found: C, 50.31; H, 3.55; N, 10.31%. 1H NMR (DMSO-d6, TMS): d (ppm) 4.08 (s, 3H, CH3), 7.72 (s, 1H, CHCH), 7.74 (s, 1H, CHCH), 7.77e7.82 (m, 2H, Acri-H), 8.00e8.05 (m, 2H, Acri-H), 8.22e8.23 (t, 1H, J ¼ 1.75 Hz, Acri-H), 8.29 (t, 1H, J ¼ 1.78 Hz, Acri-H), 8.35e8.36 (t, 1H, Acri-H), 8.38 (t, 1H, Acri-H), 9.74e9.75 (m, 1H NCHN). 13C NMR (DMSO-d6, TMS): d (ppm) 148.93, 139.65, 135.93, 135.90, 131.89, 129.79, 129.25, 125.40, 125.29, 122.57, 122.02, 36.99. 4.5. Synthesis of 1-acridinyl-3-butylimidazolium hexafluorophosphate salt (2b) A solution of 1 (2.45 g, 10 mmol) and n-butyl bromide (1.6 ml, 15 mmol) in THF (150 ml) stirred for 24 h under refluxing and a yellow precipitate was formed. The yellow solid was obtained through filtration and washed with THF, then dissolved in methanol and the solution was added to the saturable solution of NH4PF6. Yellow pale precipitate was obtained though filtration again. The yellow crystal of 2b was obtained by recrystallization from CH3CN/Et2O. Yield: 3.29 g (73.5%) Mp: 242e244  C. Anal. Calcd for C20H20F6N3P: C, 53.70; H, 4.51; N, 9.39%; Found: C, 53.62; H, 4.58; N, 9.32%. 1H NMR (DMSO-d6, TMS) d (ppm) 0.96e1.00 (t, 3H, J ¼ 7.36 Hz CH3), 1.38e1.45 (m, 2H, J ¼ 7.42 Hz CH2), 1.96e2.04 (m, 2H, J ¼ 7.44 Hz CH2), 4.39e4.42 (t, 2H, J ¼ 7.33 Hz CH2), 7.66e7.68 (d, 2H, J ¼ 8.80 Hz), 7.78e7.82 (t, 2H, J ¼ 7.54 Hz), 8.00e8.04 (t, 2H, J ¼ 7.34 Hz), 8.31e8.38 (m, 4H, J ¼ 7.53 Hz), 9.84 (s, 1H), 13C NMR (DMSO-d6, TMS): d (ppm) 177.25 (NCHN), 148.89, 141.07, 138.93, 135.80, 133.91, 131.93, 129.78, 129.42, 126.33, 125.76, 124.18, 122.33, 121.94, 121.44, 120.72, 117.59 (CH3CN), 49.98 (NCH2CH2), 31.23 (CH2CH2 CH2), 19.35 (CH2 CH2CH3), 13.74 (CH2CH3). 4.6. Synthesis of 1-acridinyl-3-ethylimidazolium hexafluorophosphate salt (2c) 2c was obtained from the similar method of that of 2b. Yield: 3.29 g (78.6%) Mp: 198e200  C. Anal. Calcd for C18H16F6N3P: C, 51.56; H, 3.85; N, 10.02%; Found: C, 51.49; H, 3.78; N, 10.08%. 1H NMR (DMSO-d6, TMS) d (ppm) 1.61e1.65 (t, 3H, J ¼ 7.32 Hz), 4.43e4.48 (q, 2H, J ¼ 7.30 Hz), 7.72e7.74 (d, 2H, J ¼ 8.40 Hz), 7.78e7.82 (m, 2H), 8.01e8.05 (m, 2H), 8.34e8.39 (m, 4H), 8.3 (d, 2H, J ¼ 8.774 Hz), 9.90 (s, 1H, NCHN). 13C NMR (DMSO-d6, TMS): d (ppm) 177.25 (NCHN), 148.93, 138.76, 135.94, 131.89, 129.79, 125.63, 123.94, 122.62, 122.00, 45.64, 14.84 (CH2CH3). 4.7. Synthesis of 1-acridinyl-3-benzylimidazoliumhexafluoroposphate salt (2d) 2d was obtained from the similar method of that of 2b. Yield: 3.59 g (74.6%) Mp: 274e276  C. Anal. Calcd for C23H18F6N3P: C, 57.39; H, 3.77; N, 8.73%; Found: C, 57.45; H, 3.72; N, 8.79%. 1H NMR

(DMSO-d6, TMS): d (ppm) 5.68 (s, 2H), 7.47e7.55 (m, 3H), 7.60e7.68 (m, 4H), 7.80e7.84 (m, 2H), 8.02e8.06 (m, 2H), 8.31e8.32 (d, 1H, J ¼ 1.80 Hz), 8.37e8.40 (m, 2H), 9.93e9.94 (t, 1H, J ¼ 1.60 Hz NCHN). 13 C NMR (DMSO-d6, TMS): d (ppm) 148.87, 135.75, 134.34, 131.90, 129.79, 129.59, 129.44, 129.09, 126.04, 124.23, 122.25, 121.87, 53.53 (ArCH2). 4.8. Synthesis of {Ag [1-acridinyl-3-methylimidazolydiene]2 (PF6)} (3a) A suspension of 2a (0.105 g, 0.4 mmol) and Ag2O (0.104 g, 0.45 mmol) in acetonitrile (8 ml) was stirred at 55  C for 12 h. The black Ag2O gradually vanished then filtered removing the excess of Ag2O. The filtrate was condensed to be evaporated under vacuum about 4 ml, and diethyl ether was added in it. 3a was obtained as yellow solid. Yield: 0.136 g (56.6%) Mp: 156e158  C. Anal. Calcd for C34H26AgF6N6OP: C, 52.94; H, 3.40; N, 10.89%; Found: C, 52.87; H, 3.46; N, 10.82%. 1H NMR (DMSO-d6, TMS): d (ppm) 3.46 (s, 6H, NCH3), 7.21e7.24 (d, 4H, J ¼ 8.63 Hz), 7.43e7.46 (t, 4H, J ¼ 7.61 Hz), 7.73e7.74 (d, 2H, J ¼ 1.28 Hz), 7.80e7.85 (m, 6H), 8.22 (s, 2H), 8.24 (S, 2H), 13C NMR (DMSO-d6, TMS): d (ppm) 148.88, 148.73, 140.95, 136.02, 131.97, 131.56, 129.78, 129.69, 129.26, 128.36, 125.44, 124.20, 122.84, 122.67, 122.07, 36.99 (CH3N). 4.9. Synthesis of {Ag [1-acridinyl-3-butylimidazolydiene]2 (PF6) (CH3CN)} (3b) Dimethyl sulfoxide (DMSO) (6 ml) was added to the mixture of 2b (0.134 g, 0.3 mmol) and Ag2O (0.039 g, 0.17 mmol) under N2 atmosphere, then the mixture was stired at 85  C for 24 h. Silver mirror will appeared sometimes. The filtrate was obtained by filtration; distilled water was added to it. Yellow pale precipitate was collected via filtration. Yield: 0.15 g (58.0%) Mp: 250e252  C. Anal. Calcd for C40H38AgF6N6P: C, 56.15; H, 4.48; N, 9.82%; Found: C, 56.21; H, 4.43; N, 9.89%. 1H NMR (DMSO-d6, TMS): d (ppm) 0.50e0.54 (t, 3H, J ¼ 6.61 Hz), 0.56e0.62 (m, 5H), 1.18e1.23 (m, 2H), 3.42e3.47 (t, 2H), 7.23 (s, 1H), 7.25 (s, 1H), 7.53e7.94 (m, 6H), 8.27e8.29 (m, 2H). 13C NMR (DMSO-d6, TMS): d (ppm) 148.93, 140.11, 131.45, 129.78, 128.57, 122.36, 122.33, 50.87 (NCH2CH2), 32.45 (CH2CH2CH3), 19.02 (CH2CH3), 13.58 (CH2CH3). 4.10. Synthesis of {Ag [1-acridinyl-3-ethylimidazolydiene] (PF6)}n (3c) 3c was prepared in a manner analogous to that of 3a as yellow solid. Yield: 0.136 g (56.6%) Mp: 268e270  C 268e270  C. Anal. Calcd for C18H15AgF6N3P: C, 41.09; H, 2.87; N, 7.99%; Found: C, 41.15; H, 2.83; N, 8.05%. 1H NMR (DMSO-d6, TMS): d (ppm) 1.23e1.24 (s, 3H), 3.91 (s, 2H), 7.31e7.39 (m, 3H), 7.45e7.53 (q, 3H, J ¼ 8.40 Hz Acr-H), 7.78e7.80 (m, 2H), 8.10e8.14 (t, 2H, J ¼ 8.00 Hz). 13C NMR (DMSO-d6, TMS): d (ppm) 148.73, 140.30, 131.35, 131.00, 129.60, 129.28, 128.95, 127.82, 125.22, 124.46, 123.45, 122.45, 122.16, 121.89, 121.88, 121.52, 46.6 (NCH2CH3), 15.94 (CH2CH3). 4.11. Synthesis of {Ag [1-acridinyl-3-benzylimidazolydiene] (PF6)}n (3d) 3d was prepared in a manner analogous to that of 3a as yellow solid. Yield: 0.105 g (53.1%) Mp: 276e278  C. Anal. Calcd for C23H17AgF6N3P: C, 46.96; H, 2.91; N, 7.14%; Found: C, 46.89; H, 2.97; N, 7.21%. 1H NMR (DMSO-d6, TMS): d (ppm) 5.40 (s, 2H), 7.29e7.38 (m, 7H), 7.55e7.59 (t, 2H, AreH, J ¼ 8.00 Hz), 7.82e7.90 (m, 4H, AcrH), 8.17e8.20 (d, 2H, Acr-H). 13C NMR (DMSO-d6, TMS): d (ppm) 148.30, 141.53, 136.96, 132.17, 129.57, 129.27, 128.67, 128.56, 127.80, 125.97, 123.53, 122.83, 118.47 (CH3CN), 65.27 (Et2O), 54.75 (ArCH2N), 15.43 (Et2O).

Z. He et al. / Journal of Organometallic Chemistry 797 (2015) 67e75

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