New eco-friendly 1-alkyl-3-(4-phenoxybutyl) imidazolium-based ionic liquids derivatives: A green ultrasound-assisted synthesis, characterization, antibacterial activity and POM analyses

Article abstract of DOI:10.3390/molecules190811741

In view of the emerging importance of the ILs as "green" materials with wide applications and our general interests in green processes, a series of a twenty five new 1-alkyl-3-(4-phenoxybutyl) imidazolium-based ionic liquids (ILs) derivatives is synthesized using a facile and green ultrasound-assisted procedure. Their structures were characterized by FT-IR, ¹H-NMR, ¹³C-NMR, ¹¹B, ¹⁹F, ³¹P, and mass spectrometry. Antimicrobial screens of some selected ILs were conducted against a panel of Gram-positive and Gram-negative bacteria. The antimicrobial activity of each compound was measured by determination of the minimal inhibitory concentration (MIC) yielding very interesting and promising results. Their antibacterial activities are reported, and, on the basis of the experimental and virtual POM screening data available, attempt is also made to elucidate the structure activity relationship.

Full text of DOI:10.3390/molecules190811741

Molecules 2014, 19, 11741-11759; doi:10.3390/molecules190811741
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
New Eco-Friendly 1-Alkyl-3-(4-phenoxybutyl) Imidazolium-
Based Ionic Liquids Derivatives: A Green Ultrasound-Assisted
Synthesis, Characterization, Antibacterial Activity and
POM Analyses
Mouslim Messali 1,*, Mohamed R. Aouad 1,2, Wael S. El-Sayed 3,4, Adeeb Al-Sheikh Ali 1,
Taibi Ben Hadda 5 and Belkheir Hammouti 6
1
Department of Chemistry, Taibah University, Al-Madina Al-Mounawara 30002, Saudi Arabia
2
Laboratoire de Chimie & Electrochimie des Complexes Métalliques (LCECM) USTO-MB,
University of Sciences and Technology Mohamed Boudiaf, BP 1505 Oran, El M'nouar, Algeria
3
Microbiology department, Faculty of Science, Ain Shams University, Cairo 11566, Egypt
4
Biology Department, Taibah University, Al-Madina Al-Mounawara 30002, Saudi Arabia
5
Laboratoire de Chimie des Matériaux, Faculté des Sciences, Université Mohammed Premier,
Oujda-60000, Morocco
6
LCAE-URAC18, Faculté des Sciences, Université Mohammed Premier, B.P. 717,
Oujda-60000, Morocco
* Author to whom correspondence should be addressed; E-Mail: mouslim@mail.be;
Tel.: +966-562-441-572.
Received: 4 June 2014; in revised form: 2 July 2014 / Accepted: 14 July 2014 /
Published: 7 August 2014
Abstract: In view of the emerging importance of the ILs as “green” materials with wide
applications and our general interests in green processes, a series of a twenty five new
1-alkyl-3-(4-phenoxybutyl) imidazolium-based ionic liquids (ILs) derivatives is
synthesized using a facile and green ultrasound-assisted procedure. Their structures
1
13
11
19
31
were characterized by FT-IR, H-NMR, C-NMR, B, F, P, and mass spectrometry.
Antimicrobial screens of some selected ILs were conducted against a panel of
Gram-positive and Gram-negative bacteria. The antimicrobial activity of each compound
was measured by determination of the minimal inhibitory concentration (MIC) yielding
very interesting and promising results. Their antibacterial activities are reported, and, on
the basis of the experimental and virtual POM screening data available, attempt is also
made to elucidate the structure activity relationship.

Molecules 2014, 19
11742
Keywords: green procedure; ultrasound irradiation; ionic liquids; antimicrobial activity;
Petra/Osiris/Molinspiration (POM) analyses
1. Introduction
Over the past two decades, Ionic liquids (ILs) have attracted considerable attention as friendly
environmental substitutes for volatile organic solvents due to the several unique properties such as
negligible vapor pressure, high thermal stability, easy recyclability, no flammability, and high ionic
conductivity [1–4]. Generally, ILs are a group of low-melting-point salts containing organic cation,
such as imidazolium, pyrrolidinium, or pyridazinium, paired with various anions, such as bromide or
tetrafluoroborate [5].
Due to these unique properties, ILs have been widely synthesized and investigated as media for
electrodeposition of metals [6–8], as a tool for lignocellulosic biomass fractionation [9], catalysis
and biocatalysis [10–16], corrosion inhibition [17–20], food chemical science [21], and the
nuclear industry [22].
Thus far, many chemists promoted to explore new procedures for the clean and efficient synthesis
of ILs since the conventional syntheses of them are not benign [23]. Several modifications have been
attempted including microwave irradiation, sonochemical reactions or solvent-free reactions. The use
of these green technologies leads to many advantages, such as large reductions in reaction times,
enhancements in conversions, sometimes in selectivity [24–27].
On the other hand, numerous studies have demonstrated the antimicrobial activity of various classes
of ionic liquids against both environmental and clinically important microorganisms [28–33].
According to the above mentioned, and our ongoing research, interest in ionic liquids
synthesis [34–36], we continued to combine the use of green technologies in the synthesis of new class
of antimicrobial agents.
Some selected ILs were investigated for their anti-microbial activity against different
pathogenic strains.
2. Results and Discussion
2.1. Chemistry
In continuation of our previous work dealing with the development of novel room temperature
functionalized ionic liquids [37], herein, we report the synthesis of a variety of new
imidazolium-based ionic liquids under both conventional and ultrasound irradiation methods
(Schemes 1 and 2).

Molecules 2014, 19
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Scheme 1. Synthesis of a variety of new imidazolium-based ionic liquids under both
conventional and ultrasound irradiation methods.
R= Et 1
R= Pr 2
R= Bu 3
(i)
R= Pent 4
R= Hex 5
R= CH2Ph 6
HN
N
N
N
R
1-6
(ii)
R= Et 7
R= Pr 8
R= Bu 9
O
R= Pent 10
R= Hex 11
R= CH2Ph 12
N
N
R
Br
7-12
(i) N-alkylation of imidazole: RBr, (KOH/K2CO3), Acetonitrile, 80 °C, 16 h. R = Et, Pr, Bu, Pent, Hex,
Benzyl. (ii) N-alkylation of N-alkylimidazole: conventional preparation (CP) and ultrasonic irradiation
conditions (US). (CP): PhO(CH2)4Br, toluene, 80 °C, 18 h; (US): toluene, 80 °C, 5 h.
Scheme 2. Anion metathesis using conventional preparation (CP) and ultrasonic irradiation
conditions (US). (CP): MY, dichloromethane, 70 °C, 3 h; (US): dichloromethane, 70 °C,
45 min. M = Na, K.
O
N
N
O
N
R
N
R
Br
Y
13-18
19-24
R= Pent
R= Hex
R= Pr
R= Bu
8-11
25-30
31-36
Y = BF , PF , CF COO, NCS, N(CN) , NO
3
4
6
3
2
Initially, various 1-alkyl-1H-imidazole 1–6 were easily prepared by treatment of imidazole with
alkyl bromide with K2CO3/KOH in Acetonitrile. The nucleophilic alkylation of N-alkylelimidazoles 1–6
under standard conditions (toluene, 80 °C, 18 h), with different alkyl halides (1.1 eq) afforded the
corresponding imidazolium halides in 78%–85% yield as oils after solvent removal by evaporation
(Table 1).

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Table 1. Reaction conditions and yields for the quaternization of N-alkylimidazole (7–12)
using conventional preparation (CP) and ultrasound irradiation conditions (US).
Yield (%) of the Quaternization Step
Compound
R
CP1
79
80
78
79
80
79
US b
a
7
8
Et
Pr
85
87
9
Bu
89
10
11
12
Pent
Hex
CH2Ph
88
87
86
a Time (18 h), Temperature (80 °C) in toluene; b Time (5 h), Temperature (80 °C) in toluene.
Previous work reports that the hydrophobicity of an ionic liquid increases with the length of the
alkyl chain on the imidazolium ring, and this increase tends to raise viscosity [38,39]. This why six
anions were used in the metathesis step in order to obtain low melting point and less viscous ILs.
The next step in the synthesis involved an anion exchange halides by using a slight excess of the
anions sodium tetrafluoroborate, potassium hexafluorophosphate, trifluoroacetic acid sodium, sodium
dicyanamide, sodium thiocyanate, or sodium nitrate anions (Scheme 2).
The resulting pure products from these reactions were subsequently obtained by filtration of the
metal halide salts, followed by filtrate evaporation and washing of the residue with dichloromethane
followed by further filtration to remove any remaining metal salts. Finally, evaporation of the filtrate
afforded the desired ionic liquids 13–36 in good yields (Table 2).
As already reported by our team, an anion exchange metathesis is easily performed by ultrasonic
activation [34]. In a similar way, the preparation of ILs 13–36 was carried in a closed vessel and
exposed to irradiation for 45 min at 70 °C using a sonication bath. The data presented in Table 2
indicated that very good yields were obtained in very short reaction times. As observed, the anion
nature of the exchange agents did not affect product yields.
Table 2. Reaction conditions and yields for the anion metathesis reaction using
conventional preparation (CP) and ultrasound irradiation conditions (US).
Yield (%) for the Anion Metathesis
Compound
R
MY
a
CP2
95
95
92
94
92
94
94
93
93
92
93
92
(US) b
13
14
15
16
17
18
19
20
21
22
23
24
NaBF4
KPF6
96
97
NaOOCCF3
NaN(CN)2
NaNCS
NaNO3
98
Pr
97
97
95
NaBF4
98
KPF6
97
NaOOCCF3
NaN(CN)2
NaNCS
NaNO3
97
Bu
96
95
96

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Table 2. Cont.
Yield (%) for the Anion Metathesis
Compound
R
MY
a
CP2
95
93
95
94
94
94
94
93
95
92
93
94
(US) b
25
26
27
28
29
30
31
32
33
34
35
36
NaBF4
KPF6
98
96
NaOOCCF3
NaN(CN)2
NaNCS
NaNO3
97
Pent
97
95
98
NaBF4
97
KPF6
96
NaOOCCF3
NaN(CN)2
NaNCS
NaNO3
97
Hex
96
95
97
a Time (3 h), Temperature (70 °C) in acetonitrile; b Time (45 min), Temperature (70 °C) in acetonitrile.
1
13
The structures of all the newly synthesized ionic liquids were confirmed by H-NMR, C-NMR,
11B-NMR, 19F-NMR, 31P-NMR, FT-IR, and LCMS analysis. All spectroscopic data are detailed in the
experimental part.
2.2. Antimicrobial Activity
The short generation times of bacteria compared with other living organisms give a good starting
point to examine the toxicity of ILs [40]. This has indirectly led to the realization that some ILs exhibit
anti-microbialactivity.
One of the objectives of the present study is therefore to investigate the anti-microbial activities of
some synthesized ILs. For this, several types of human pathogens were selected to assess the potential
toxicities of these ILs and theireffectiveness as anti-microbial agents.
In this aim, the water soluble ILs 7–12 were tested in vitro for their antibacterial activity against
Gram-positive bacteria including; Staphylococcus aureus, Streptococcus pneumonia, Bacillus subtilis
and Bacillus cereus, as well as Gram-negative bacteria, including Escherichia coli, Klebsiella
pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. These clinical isolates were
selected based on their pathogenic properties. The antibacterial activity was measured by
determination of MIC values in a range from 0 to 256 µg/mL and compared with those of some potent
antibacterial compounds like mezlocillin, amikacin, tetracycline and nitrofurantion. MIC values are
summarized (Table 3).
From the MIC values obtained, all compounds exhibited antibacterial activity with varying potential
as well as spectrum. In general, all tested ILs (7–12) possessed congruent antibacterial activities
against the growth of E. coli, K. pneumoniae, S. aureus and S. pneumoniae as compared with the
standards mezlocillin, amikacin, tetracycline, and nitrofurantion while showed low activity
(>128 µg/mL) against P. aeruginosa and A. baumannii.

Molecules 2014, 19
Table 3. Antimicrobial activity of Ionic liquids 7–12 against eight bacterial strains.
11746
MIC (µg/mL)
Compounds
E.
K.
P.
aeruginosa
>256
>256
>256
128
A.
S.
S.
B.
B.
coli pneumoniae
baumannii aureus pneumoniae subtilis cereus
7
64
32
16
16
16
16
128
32
16
64
16
16
8
>256
>256
>256
256
128
>256
128
32
64
64
32
16
8
64
64
16
8
128
128
128
64
16
64
32
---
>256
>256
>256
64
8
9
10
11
8
>256
>256
128
8
32
12
32
128
32
16
128
64
---
32
---
128
32
---
32
8
>256
32
Mezlocillin
Amikacin
Tetracycline
32
---
---
16
4
4
Nitrofurantion 128
---
---
128
---
---
In particular, IL 11 exhibited the highest antibacterial activities in the series against most of the
tested bacteria with MIC values (<32 µg/mL). Having MIC value of 8 for IL 11 against K. pneumoniae,
S. aureus, and S. pneumonia makes it a good candidate as a potent antibacterial agent. Such relatively
high antibacterial activity of IL 11 can be attributed to the presence of the hexyl chain which is absent
in the IL 7 having lowest toxicity. This trend was also found in case of IL 9 and 10. Therefore, it can
be concluded that the biological activity of ILs 7–11 depends on the length of the alkyl chain and
increased with increasing the hydrophobicity for the tested ILs.
Beside antibacterial activity, all tested ILs (7–12) showed broader spectrum revealed by detected
antibacterial activity against Gram-positive and Gram-negative bacteria, particularly S. aureus,
S. pneumonia and E. coil, K. pneumonia, respectively.
2.3. POM Analyses of Compounds 7–12
For a molecule to be a potential drug, besides having a good biological activity, it must have good
pharmacokinetic properties in biological systems. To access the pharmacokinetic profile of the
synthesized molecules, we used well validated in silico tools: Osiris, Petra and Molinspiration. These
tools have been validated with almost 7000 drug molecules available on the market.
The analysis of theoretical toxicity risks for the similar ILs using the Osiris program showed that
similar ILs were less toxic than standard clinical drugsand can be used as therapeutic agents.
From the data evaluated in Table 4 indicates that, all structures are supposed to be non-mutagenic
when run through the mutagenicity assessment system and, as far as irritating and reproductive effects
are concerned, all the compounds are at low risk comparable with standard drugs used. The
hydrophilicity character of each compound has been expressed in term of the log p value which
correspond to the logarithm of its partition coefficient between n-octanol and water. It has been
established that the absorption or permeation is greatly affected by the hydrophilicity (value of Log p).
Accordingly, when Log p is higher than 5, the absorption or permeation decrease.
On this basis, all the majority of compounds 7–12 is having log P values under the acceptable
criteria should be active but they are not active because there is another crucial parameter which
should be taken in consideration. It concerns the geometrical conformation of pharmacophore. The

Molecules 2014, 19
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absorption, distribution characteristics and bioactivity was proved to be dependent to the geometrical
parameter and the aqueous solubility of a compound. Consequently, the bad absorption could
presumably due to the low solubility of the tested ILs. Further, the Table 4 shows drug-likeness of
compounds 7–12 which is not in the comparable zone with that of standard drugs used.
We have calculated overall drug-score (DS) for the compounds 7–12 and compared with that of
standard drugs (AMP, GENTA, and AMPHO) used as shown in Tables 4 and 5. The DS combines
drug-likeness, log p, log S, molecular weight, and toxicity risks, in one handy value that may be used
to judge the compound’s overall potential to qualify for a drug. The reported compounds 7–12 showed
low to moderate DS as compared with standard drugs used.
Table 4. Osiris calculations of toxicity risks and drug-score of compounds 7–12.
Br-
N
N+
R
O
(7-12)
Toxicity Risks [a]
Drug-Score [b]
DL
Compd.
R
MUT TUMO IRRI REP CLP
S
DS
7
Ethyl
Propyl
Butyl
Pentyl
Hexyl
Benzyl
---
2.38 −2.67 −0.66 0.60
2.84 −2.94 −0.90 0.56
3.31 −3.21 −3.16 0.43
3.77 −3.48 −5.85 0.39
4.23 −3.76 −10.23 0.36
3.31 −3.69 −0.91 0.41
−0.03 −2.53 15.14 0.66
8
9
10
11
12
Mezlocillin
Amikacin
Tetracycline
Nitrofurantion
: not toxic;
---
−8.00 −0.23
−1.02 −1.83
−0.07 −2.50
1.73
5.43
0.67
0.35
0.81
0.78
---
---
[a]
: slightly toxic;
: highly toxic. MUT: mutagenic; TUMO: tumorigenic; IRRI:
irritant; REP: reproductive effective. [b] CLP: cLogP, S: Solubility, DL: Druglikness, DS: Drug-Score.
2.4. Molinspiration Calculations
cLog P (octanol/water partition coefficient) is calculated by the methodology developed by
Molinspiration as a sum of fragment based contributions and correction factors (Table 4). The method
is very useful and can be applied to all organic and some organometallic molecules. Molecular Polar
Surface Area values (TPSA) were also measured using the above mentioned methodology. O– and N–
centred polar fragments are considered. PSA has been shown to be a useful parameter for
determination of drug absorption and especially intestinal absorption, bioavailability, and blood–brain
barrier penetration. Prediction results of compounds 7–12 molecular properties (TPSA, GPCR ligand,
and ICM) are valued (Table 5).

Molecules 2014, 19
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Table 5. Molinspiration calculations of compounds 7–12.
Physico-Chemical Properties [a]
Drug Likeness [b]
KI NRL
MW
(g/mol)
325
Compd.
TPSA O/NH VIOL VOL GPC ICM
PI
EN
7
12.47
12.47
12.47
12.47
12.47
12.47
173
0
0
0
0
0
0
0
0
2
3
1
0
271 −0.06 −0.10 −0.18 −0.06 −0.22 0.01
8
339
287
304
321
338
325
0.04 −0.06 −0.13 0.03 −0.10 0.03
0.07 −0.06 −0.10 0.08 −0.05 0.05
9
10
353
0
367
0
0.10 −0.05 −0.07 0.12
0.12 −0.05 −0.05 0.13
0.09 −0.06 −0.01 0.08
0.01
0.03
0.04
0.07
0.06
0.04
0.10
0.45
11
381
0
12
387
0
Mezlocillin
Amikacin
Tetracycline
539
3
434 −0.04 −0.43 −0.60 −0.58 0.66
510 0.32 −0.09 0.16 −0.10 0.78
585
332
17
7
444
182
377 −0.15 −0.24 −0.53 −0.09 −0.04 0.52
181 −1.36 −0.90 −1.21 −2.16 −1.45 −0.79
Nitrofurantion
238
121
1
[a]
TPSA: Total polar surface area; O/NH: O---HN interaction; VIOL: number of violation; VOL: volume.
GPC: GPCR ligand; ICM: Ion channel modulator; KI: Kinase inhibitor; NRL: Nuclear receptor ligand;
[b]
PI: Protease inhibitor; EI: Enzyme inhibitor.
The bioactivity properties were greatly affected by the electronic and steric factors. The obtained
POM results confirm that most of these ILs could be used as potential antimicrobial activity after
major modifications. Based on their great hydrosolubility properties, these compounds may be useful
as solubilising substituents with potential anti-tumoralactivity. These results prompt several pertinent
observations: (i) This type of ILs can furnish an interesting model for studying the interaction of
target-antibiotics complexes with cancer phosphates because the possible charge (P=Oδ---Nδ+)
modification of pi-charge pharmacophore group; (ii) The future flexiblelipophyl-hydrosoluble drugs
containing Il moiety will enable us to prepare molecules for multi-therapeutic materials with high
combined antibacterial/antiviral/antifungal/antitumoral activity.
3. Materials and Methods
3.1. Experimental
1
13
All new compounds were synthesized and characterized by H-NMR, C-NMR, IR, and LCMS.
1H-NMR (400 MHz) and 13C-NMR (100 MHz) spectra were measured in CDCl3 at room temperature.
Chemical shifts (δ) were reported in ppm to a scale calibrated for tetramethylsilane (TMS), which is
used as an internal standard. The LCMS spectra were measured with a Micromass, LCT mass
spectrometer. IR spectra were recorded in NaCl or KBr disc on a Schimadzu 8201 PC, FTIR
spectrophotometer (υmax in cm−1). The ultrasound-assisted reactions were performed using a high
intensity ultrasonic processor SUB Aqua 5 Plus-Grant with temperature controller (750 W),
microprocessor controlled-2004, the ultrasonic frequency of the cleaning bath used equal 25 KHz.
3.2. Synthesis
General procedures for the synthesis of imidazolium halides (7–12) using conventional method. To
the solution of N-alkylimidazole (1 eq) in toluene, was added alkyl bromide (1.1 eq) at room
temperature, followed by stirring at 80 °C for 18 h. The completion of the reaction was marked by the

Molecules 2014, 19
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separation of oil from the initially obtained clear and homogenous mixture of N-alkylimidazole and
alkyl halide in toluene. The product was isolated by extraction to remove the unreacted starting
materials and solvent. Subsequently, the imidazolium salt was washed with ethyl acetate. In each case,
the IL/salt was finally dried at a reduced pressure to get rid of all the volatile organic compounds.
General procedure for the synthesis of imidazolium halides (7–12) using under Ultrasonic
irradiation. Alkylimidazole (1 eq) and the appropriate alkyl bromide (1 eq) were placed in a closed
vessel and exposed to irradiation for 5 h at 80 °C using a sonication bath. The product was then
collected as described in the conventional procedure outlined earlier.
General procedure for the methathesis reaction of (8–11) leading to compounds (13–36) using
conventional method. The quaternary salt (1 eq) was dissolved in dichloromethane to obtain a clear
solution. To this solution of quaternary halide was added solution of sodium tetrafluoroborate,
potassium hexafluorophosphate, trifluoroacetic acid sodium, sodium dicyanamide, sodium thiocyanate,
or sodium nitrate (1.2 eq), followed by stirring at 70 °C for 3 h. The cooled reaction mixture was
filtered through Celite to remove solid metal halide. The evaporation of dichloromethane leaded
quantitatively to the desired ionic liquids.
General procedure for the ultrasound-assisted methathesis reaction of (8–11) leading to compounds
(13–36). Imidazolium-halides salts (1 eq) and NaBF4, KPF6, CF3COONa, NaN(CN)2, NaNCS or
NaNO3 (1 eq) were placed in a closed vessel and exposed to irradiation for 45 min at 70 °C using a
sonication bath. The product was then collected as described in the conventional procedure
outlined earlier.
3.3. Characterization
1
1-Ethyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium bromide (7). H-NMR (CDCl3, 400 MHz): δ = 1.40
(t, J = 7.2 Hz, 3H), 1.69 (quint, J = 7.6 Hz, 2H), 1.96 (quint, J = 7.6 Hz, 2H), 3.96 (t, J = 7.6 Hz, 2H),
4.23 (q, J = 7.2 Hz, 2H), 4.30 (t, J = 7.6 Hz, 2H), 6.87–6.91 (m, 3H, Ar-H), 7.22–7.27 (m, 2H, Ar-H),
7.93–7.99 (m, 2H), 9.55 (s, 1H); 13C-NMR (CDCl3, 100 MHz): δ = 15.0 (CH3), 25.3 (CH2), 26.3
(CH2), 44.1 (CH2), 48.4 (CH2), 66.6 (CH2), 114.3 (CH), 120.4 (CH), 122.1 (CH), 122.3 (CH), 129.4
(CH), 135.8 (CH), 158.3 (C); IR (NaCl) υmax 3132 (C-H Ar), 1599–1471 (C=C), 1165(C-N), 1082
(C-O) cm−1; LCMS (M+)-Br− 245.2 found for C15H21N2O+.
1
1-Propyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium bromide (8). H-NMR (CDCl3, 400 MHz): δ = 0.88
(t, J = 7.2 Hz, 3H), 1.76 (quint, J = 7.6 Hz, 2H), 1.88 (sextet, J = 7.6 Hz, 2H), 2.07 (quint, J = 7.6 Hz,
2H), 3.93 (t, J = 7.6 Hz, 2H), 4.21 (t, J = 7.2 Hz, 2H), 4.40 (t, J = 7.6 Hz, 2H), 6.77–6.86 (m, 3H, Ar-H),
7.15–7.19 (m, 2H, Ar-H), 7.50–7.58 (m, 2H, Ar-H), 10.22 (s, 1H, Ar-H); 13C-NMR (CDCl3, 100 MHz):
δ = 10.7 (CH3), 23.6 (CH2), 25.8 (CH2), 27.3 (CH2), 49.6 (CH2), 51.3 (CH2), 66.7 (CH2), 114.4 (CH),
120.8 (CH), 122.3 (CH), 122.4 (CH), 129.5 (CH), 136.6 (CH), 158.5 (C); IR (NaCl) υmax 3131 (C-H
Ar), 1599–1470 (C=C), 1164(C-N), 1083 (C-O) cm−1; LCMS (M+)-Br− 259.2 found for C16H23N2O+.
1-Butyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium bromide (9). 1H-NMR (CDCl3, 400 MHz): δ = 0.88 (t,
J = 7.2 Hz, 3H), 1.31 (sextet, J = 7.6 Hz, 2H), 1.78–1.82 (m, J = 7.6 Hz, 4H), 2.10 (quint, J = 7.6 Hz,
2H), 3.94 (t, J = 7.6 Hz, 2H), 4.25 (t, J = 7.2 Hz, 2H), 4.41 (t, J = 7.6 Hz, 2H), 6.79–6.86 (m, 3H,
13
Ar-H), 7.17–7.21 (m, 2H, Ar-H), 7.47–7.58 (m, 2H, Ar-H), 10.22 (s, 1H, Ar-H); C-NMR (CDCl3,

Molecules 2014, 19
11750
100 MHz): δ = 13.4 (CH3), 19.4 (CH2), 25.8 (CH2), 27.3 (CH2), 32.1 (CH2), 48.7 (CH2), 49.6 (CH2),
66.8 (CH2), 114.4 (CH), 120.8 (CH), 122.2 (CH), 122.4 (CH), 129.5 (CH), 136.6 (CH), 158.5 (C); IR
(NaCl) υmax 3133 (C-H Ar), 1600–1471 (C=C), 1166(C-N), 1082 (C-O) cm−1; LCMS (M+)-Br− 273.3
found for C17H25N2O+.
1
1-Pentyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium bromide (10). H-NMR (CDCl3, 400 MHz): δ = 0.67
(t, J = 7.2 Hz, 3H), 1.04–1.15 (m, 4H), 1.62–1.72 (m, 4H), 1.97 (quint, J = 7.6 Hz, 2H), 3.79 (t, J = 7.6 Hz,
2H), 4.11 (t, J = 7.2 Hz, 2H), 4.28 (t, J = 7.6 Hz, 2H), 6.79–6.86 (m, 3H, Ar-H), 7.65–7.71 (m, 2H,
13
Ar-H), 7.02–7.06 (m, 2H, Ar-H), 10.13 (s, 1H, Ar-H); C-NMR (CDCl3, 100 MHz): δ = 13.7 (CH3),
21.8 (CH2), 25.7 (CH2), 27.2 (CH2), 28.0 (CH2), 29.7 (CH2), 49.4 (CH2), 49.8 (CH2), 66.6 (CH2),
114.2 (CH), 120.6 (CH), 122.2 (CH), 122.5 (CH), 129.3 (CH), 136.3 (CH), 158.4 (C); IR (NaCl) υmax
3132 (C-H Ar), 1600–1471 (C=C), 1164 (C-N), 1081 (C-O) cm−1; LCMS (M+)-Br− 287.3 found
for C18H27N2O+.
1
1-Hexyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium bromide (11). H-NMR (CDCl3, 400 MHz): δ = 0.94
(t, J = 7.2 Hz, 3H), 1.14 (quint, J = 7.6 Hz, 2H), 1.39–1.41 (m, 4H), 1.69 (quint, J = 7.6 Hz, 2H), 1.77
(quint, J = 7.6 Hz, 2H), 1.96 (quint, J = 7.6 Hz, 2H), 3.96 (t, J = 7.6 Hz, 2H), 4.27 (quint, J = 7.2 Hz,
2H), 4.46 (t, J = 7.6 Hz, 2H), 6.87–6.91 (m, 3H, Ar-H), 7.22–7.27 (m, 2H, Ar-H), 7.93–7.99 (m, 2H,
Ar-H), 9.55 (s, 1H, Ar-H); 13C-NMR (CDCl3, 100 MHz): δ = 13.9 (CH3), 22.6 (CH2), 24.8 (CH2), 27.2
(CH2), 27.3 (CH2), 32.6 (CH2), 33.9 (CH2), 44.1 (CH2), 48.3 (CH2), 66.6 (CH2), 114.3 (CH), 120.4
(CH), 122.1 (CH), 122.3 (CH), 129.4 (CH), 135.8 (CH), 158.3 (C); IR (NaCl) υmax 3132 (C-H Ar),
1598–1472 (C=C), 1165 (C-N), 1081 (C-O) cm−1; LCMS (M+)-Br− 301.3 found for C19H29N2O+.
1-Benzyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium bromide (12). White crystals, Mp 153–155 °C,
1H-NMR (CDCl3, 400 MHz): δ = 1.77 (quint, J = 8, 2H), 2.07 (quint, J = 8 Hz, 2H), 3.91 (t, J = 8 Hz,
2H), 4.35 (t, J = 8 Hz, 2H), 5.52 (s, 2H), 6.77–6.88 (m, 3H), 7.17–7.55 (m, 9H), 10.45 (s, 1H);
13C-NMR (CDCl3, 100 MHz): δ = 25.7 (CH2), 26.9 (CH2), 49.7 (CH2), 53.2 (CH2), 66.7 (CH2), 114.4
(CH), 120.8 (CH), 122.2 (CH), 122.6 (CH), 128.9 (CH), 129.4 (CH), 129.5 (CH), 133.0 (C), 135.5
(CH), 158.6 (C); IR (KBr) υmax 3130 (C-H Ar), 1599–1471 (C=C), 1164 (C-N), 1081 (C-O) cm−1;
LCMS (M+)-Br− 307.3.3 found for C20H23N2O+.
1
1-Propyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium tetrafluoroborate (13). H-NMR (CDCl3, 400 MHz):
δ = 0.88 (t, J = 7.2 Hz, 3H), 1.76 (quint, J = 7.6 Hz, 2H), 1.88 (sextet, J = 7.6 Hz, 2H), 2.07 (quint,
J = 7.6 Hz, 2H), 3.93 (t, J = 7.6 Hz, 2H), 4.21 (t, J = 7.2 Hz, 2H), 4.40 (t, J = 7.6 Hz, 2H),
6.77–6.86 (m, 3H, Ar-H), 7.15–7.19 (m, 2H, Ar-H), 7.50–7.58 (m, 2H, Ar-H), 10.22 (s, 1H, Ar-H);
13C-NMR (CDCl3, 100 MHz): δ = 8.7 (CH3), 21.6 (CH2), 24.0 (CH2), 25.3 (CH2), 47.9 (CH2), 49.6
(CH2), 65.0 (CH2), 112.6 (CH), 119.0 (CH), 120.7 (CH), 122.2 (CH), 127.7 (CH), 133.7 (CH), 158.5
(C); 19F-NMR (CDCl3, 376.5 MHz): δ = −150.65; 11B-NMR (CDCl3, 128 MHz): δ = −0.96; IR (NaCl)
−
υ
max 3133 (C-H Ar), 1598–1472 (C=C), 1166 (C-N), 1084 (C-O) cm−1; LCMS (M+)-BF4 259.2 found
for C16H23N2O+.
1-Propyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium hexafluorophospate (14). 1H-NMR (CDCl3, 400 MHz):
δ = 0.94 (t, J = 7.2 Hz, 3H), 1.80 (quint, J = 7.6 Hz, 2H), 1.87 (sextet, J = 7.6 Hz, 2H), 2.06 (quint,

Molecules 2014, 19
11751
J = 7.6 Hz, 2H), 3.98 (t, J = 7.6 Hz, 2H), 4.10 (t, J = 7.2 Hz, 2H), 4.25 (t, J = 7.6 Hz, 2H), 6.86–6.96
(m, 3H, Ar-H), 7.25–7.32 (m, 5H, Ar-H ), 8.58 (s, 1H, Ar-H); 13C-NMR (CDCl3, 100 MHz): δ = 10.5
(CH3), 23.2 (CH2), 25.7 (CH2), 27.0 (CH2), 49.8 (CH2), 51.6 (CH2), 66.7 (CH2), 114.4 (CH), 120.9
19
(CH), 122.2 (CH), 122.3 (CH), 129.6 (CH), 135.2 (CH), 158.6 (C); F-NMR (CDCl3, 376.5 MHz):
δ = −71.10 ; 31P NMR (CDCl3, 162 MHz): δ = −144.31 (sep, J = 712.8 Hz); IR (NaCl) υmax 3132 (C-H
−
Ar), 1599–1471 (C=C), 1165(C-N), 1082 (C-O) cm−1; LCMS (M+)-PF6 259.2 found for C16H23N2O+.
1
1-Propyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium trifluroacetate (15). H-NMR (CDCl3, 400 MHz):
δ = 0.88 (t, J = 7.2 Hz, 3H), 1.75 (quint, J = 7.6 Hz, 2H), 1.83 (sextet, J = 7.6 Hz, 2H), 2.03 (quint,
J = 7.6 Hz, 2H), 3.92 (t, J = 7.6 Hz, 2H), 4.14 (t, J = 7.2 Hz, 2H), 4.33 (t, J = 7.6 Hz, 2H),
6.79–6.88 (m, 3H, Ar-H), 7.18–7.22 (m, 3H, Ar-H ), 7.40–7.47 (m, 2H, Ar-H ), 10.10 (s, 1H, Ar-H);
13C-NMR (CDCl3, 100 MHz): δ = 10.5 (CH3), 23.4 (CH2), 25.7 (CH2), 27.2 (CH2), 49.5 (CH2), 51.3
(CH2), 66.7 (CH2), 114.3 (CH), 120.8 (CH), 122.1 (CH), 122.2 (CH), 129.4 (CH), 137.0 (CH), 158.5
19
(C); F-NMR (CDCl3, 376.5 MHz): δ = −75.42; IR (NaCl) υmax 3131 (C-H Ar), 1599–1469 (C=C),
−
1166 (C-N), 1079 (C-O) cm−1; LCMS (M+)-CF3CO2 259.2 found for C16H23N2O+.
1
1-Propyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium dicyanoamine (16). H-NMR (CDCl3, 400 MHz):
δ = 0.91 (t, J = 7.2 Hz, 3H), 1.79 (quint, J = 7.6 Hz, 2H), 1.82 (sextet, J = 7.6 Hz, 2H), 2.08 (quint,
J = 7.6 Hz, 2H), 3.95 (t, J = 7.6 Hz, 2H), 4.19 (t, J = 7.2 Hz, 2H), 4.36 (t, J = 7.6 Hz, 2H), 6.81–6.88
13
(m, 3H, Ar-H), 7.18–7.22 (m, 3H, Ar-H ), 7.45–7.51 (m, 2H, Ar-H ), 9.28 (s, 1H, Ar-H); C-NMR
(CDCl3, 100 MHz): δ = 8.8 (CH3), 21.6 (CH2), 24.0 (CH2), 25.4 (CH2), 48.1 (CH2), 49.8 (CH2), 64.9
(CH2), 112.6 (CH), 118.9 (CH), 120.6 (CH), 120.7 (CH), 127.6 (CH), 134.0 (CH), 156.6 (C); IR
(NaCl) υmax 3133 (C-H Ar), 1598–1472 (C=C), 1163 (C-N), 1080 (C-O) cm−1; LCMS (M+)-(CN)2N−
259.2 found for C16H23N2O+.
1-Propyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium thiocyanate (17). 1H-NMR (CDCl3, 400 MHz): δ = 0.89
(t, J = 7.2 Hz, 3H), 1.78 (quint, J = 7.6 Hz, 2H), 1.86 (sextet, J = 7.6 Hz, 2H), 2.03 (quint, J = 7.6 Hz,
2H), 3.93 (t, J = 7.6 Hz, 2H), 4.12 (t, J = 7.2 Hz, 2H), 4.29 (t, J = 7.6 Hz, 2H), 6.79–6.87 (m, 3H, Ar-H),
7.16–7.22 (m, 3H, Ar-H ), 7.39–7.46 (m, 2H, Ar-H ), 9.50 (s, 1H, Ar-H); 13C-NMR (CDCl3,
100 MHz): δ = 8.8 (CH3), 21.6 (CH2), 23.9 (CH2), 25.3 (CH2), 47.9 (CH2), 49.6 (CH2), 64.8 (CH2),
112.5 (CH), 119.0 (CH), 120.5 (CH), 120.6 (CH), 127.6 (CH), 134.1 (CH), 156.6 (C); IR (NaCl) υmax
3129 (C-H Ar), 1597–1469 (C=C), 1163 (C-N), 1079 (C-O) cm−1; LCMS (M+)-SCN− 259.2 found
for C16H23N2O+.
1
1-Propyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium nitrate (18). H-NMR (CDCl3, 400 MHz): δ = 0.75
(t, J = 7.2 Hz, 3H), 1.63 (quint, J = 7.6 Hz, 2H), 1.74 (sextet, J = 7.6 Hz, 2H), 1.94 (quint, J = 7.6 Hz,
2H), 3.79 (t, J = 7.6 Hz, 2H), 4.07 (t, J = 7.2 Hz, 2H), 4.23 (t, J = 7.6 Hz, 2H), 6.66–6.74 (m, 3H, Ar-H),
7.03–7.07 (m, 3H, Ar-H ), 7.42–7.50 (m, 2H, Ar-H ), 9.92 (s, 1H, Ar-H); 13C-NMR (CDCl3,
100 MHz): δ = 10.6 (CH3), 23.4 (CH2), 25.7 (CH2), 27.1 (CH2), 49.4 (CH2), 51.2 (CH2), 66.6 (CH2),
114.3 (CH), 120.7 (CH), 122.3 (CH), 122.4 (CH), 129.3 (CH), 136.4 (CH), 156.4 (C); IR (NaCl) υmax
−
3132 (C-H Ar), 1598–1470 (C=C), 1165 (C-N), 1081 (C-O) cm−1; LCMS (M+)-NO3 259.2 found
for C16H23N2O+.

Molecules 2014, 19
11752
1
1-Butyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium tetrafluoroborate (19). H-NMR (CDCl3, 400 MHz):
δ = 0.90 (t, J = 7.2 Hz, 3H), 1.33 (sextet, J = 7.6 Hz, 2H), 1.80–1.84 (m, J = 7.6 Hz, 4H), 2.12 (quint,
J = 7.6 Hz, 2H), 3.96 (t, J = 7.6 Hz, 2H), 4.27 (t, J = 7.2 Hz, 2H), 4.43 (t, J = 7.6 Hz, 2H), 6.81–6.89
(m, 3H, Ar-H), 7.19–7.24 (m, 2H, Ar-H), 7.50–7.61 (m, 2H, Ar-H), 9.58 (s, 1H, Ar-H); 13C-NMR
(CDCl3, 100 MHz): δ = 12.4 (CH3), 18.4 (CH2), 24.8 (CH2), 26.3 (CH2), 31.1 (CH2), 47.6 (CH2), 48.7
(CH2), 65.8 (CH2), 113.4 (CH), 119.8 (CH), 121.2 (CH), 121.4 (CH), 128.5 (CH), 135.6 (CH), 157.5
(C); 19F-NMR (CDCl3, 376.5 MHz): δ = −150.35; 11B-NMR (CDCl3, 128 MHz): δ = −0.98; IR (NaCl)
−
υ
max 3130 (C-H Ar), 1599–1471 (C=C), 1164 (C-N), 1082 (C-O) cm−1; LCMS (M+)-BF4 273.3 found
for C17H25N2O+.
1
1-Butyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium hexafluorophospate (20). H-NMR (CDCl3, 400 MHz):
δ = 0.87 (t, J = 7.2 Hz, 3H), 1.30 (sextet, J = 7.6 Hz, 2H), 1.77–1.81 (m, J = 7.6 Hz, 4H), 2.09 (quint,
J = 7.6 Hz, 2H), 3.92 (t, J = 7.6 Hz, 2H), 4.23 (t, J = 7.2 Hz, 2H), 4.39 (t, J = 7.6 Hz, 2H), 6.77–6.86
(m, 3H, Ar-H), 7.15–7.20 (m, 2H, Ar-H), 7.46–7.57 (m, 2H, Ar-H), 8.78 (s, 1H, Ar-H); 13C-NMR
(CDCl3, 100 MHz): δ = 12.8 (CH3), 18.8 (CH2), 25.2 (CH2), 26.8 (CH2), 31.5 (CH2), 48.0 (CH2), 49.1
(CH2), 66.2 (CH2), 113.7 (CH), 120.2 (CH), 121.6 (CH), 121.6 (CH), 128.9 (CH), 136.0 (CH), 158.2
(C); 19F-NMR (CDCl3, 376.5 MHz): δ = −72.96; 31P NMR (CDCl3, 162 MHz): δ = −144.96 (sep,
J = 712.8 Hz); IR (NaCl) υmax 3134 (C-H Ar), 1598–1469 (C=C), 1163 (C-N), 1080 (C-O) cm−1;
−
LCMS (M+)-PF6 273.3 found for C17H25N2O+.
1
1-Butyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium trifluroacetate (21). H-NMR (CDCl3, 400 MHz):
δ = 0.88 (t, J = 7.2 Hz, 3H), 1.32 (sextet, J = 7.6 Hz, 2H), 1.78–1.83 (m, J = 7.6 Hz, 4H), 2.10 (quint,
J = 7.6 Hz, 2H), 3.94 (t, J = 7.6 Hz, 2H), 4.24 (t, J = 7.2 Hz, 2H), 4.41 (t, J = 7.6 Hz, 2H), 6.78–6.88
(m, 3H, Ar-H), 7.16–7.22 (m, 2H, Ar-H), 7.47–7.59 (m, 2H, Ar-H), 8.99 (s, 1H, Ar-H); 13C-NMR
(CDCl3, 100 MHz): δ = 13.1 (CH3), 19.1 (CH2), 25.5 (CH2), 27.1 (CH2), 31.8 (CH2), 48.3 (CH2), 49.4
(CH2), 66.5 (CH2), 114.0 (CH), 120.6 (CH), 121.9 (CH), 121.9 (CH), 129.2 (CH), 136.3 (CH), 158.5
(C); 19F-NMR (CDCl3, 376.5 MHz): δ = −75.72;IR (NaCl) υmax 3132 (C-H Ar), 1599–1471 (C=C),
−
1165(C-N), 1082 (C-O) cm−1; LCMS (M+)-CF3CO2 273.3 found for C17H25N2O+.
1-Butyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium dicyanoamine (22). 1H-NMR (CDCl3, 400 MHz): δ = 0.88
(t, J = 7.2 Hz, 3H), 1.31 (sextet, J = 7.6 Hz, 2H), 1.78–1.82 (m, J = 7.6 Hz, 4H), 2.10 (quint, J = 7.6 Hz,
2H), 3.94 (t, J = 7.6 Hz, 2H), 4.25 (t, J = 7.2 Hz, 2H), 4.41 (t, J = 7.6 Hz, 2H), 6.79–6.86 (m, 3H,
13
Ar-H), 7.17–7.21 (m, 2H, Ar-H), 7.47–7.58 (m, 2H, Ar-H), 10.22 (s, 1H, Ar-H); C-NMR (CDCl3,
100 MHz): δ = 13.4 (CH3), 19.4 (CH2), 25.8 (CH2), 27.3 (CH2), 32.1 (CH2), 48.7 (CH2), 49.6 (CH2),
66.9 (CH2), 114.5 (CH), 120.8 (CH), 122.2 (CH), 122.4 (CH), 129.5 (CH), 136.6 (CH), 158.5 (C); IR
(NaCl) υmax 3130 (C-H Ar), 1600–1470 (C=C), 1164 (C-N), 1081 (C-O) cm−1; LCMS (M+)-(CN)2N −
273.3 found for C17H25N2O+.
1-Butyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium thiocyanate (23). 1H-NMR (CDCl3, 400 MHz): δ = 0.92
(t, J = 7.2 Hz, 3H), 1.35 (sextet, J = 7.6 Hz, 2H), 1.82–1.86 (m, J = 7.6 Hz, 4H), 2.13 (quint, J = 7.6 Hz,
2H), 3.97 (t, J = 7.6 Hz, 2H), 4.28 (t, J = 7.2 Hz, 2H), 4.45 (t, J = 7.6 Hz, 2H), 6.79–6.86 (m, 3H, Ar-H),
7.17–7.21 (m, 2H, Ar-H), 7.47–7.58 (m, 2H, Ar-H), 8.99 (s, 1H, Ar-H); 13C-NMR (CDCl3, 100 MHz):
δ = 13.4 (CH3), 19.4 (CH2), 25.8 (CH2), 27.3 (CH2), 32.1 (CH2), 48.7 (CH2), 49.6 (CH2), 66.8 (CH2),

Molecules 2014, 19
11753
114.4 (CH), 120.8 (CH), 122.2 (CH), 122.4 (CH), 129.5 (CH), 136.6 (CH), 158.5 (C); IR (NaCl) υmax
3128 (C-H Ar), 1599–1471 (C=C), 1162 (C-N), 1079 (C-O) cm−1; LCMS (M+)-SCN− 273.3 found
for C17H25N2O+.
1
1-Butyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium nitrate (24). H-NMR (CDCl3, 400 MHz): δ = 0.90 (t,
J = 7.2 Hz, 3H), 1.33 (sextet, J = 7.6 Hz, 2H), 1.80–1.84 (m, J = 7.6 Hz, 4H), 2.12 (quint, J = 7.6 Hz,
2H), 3.96 (t, J = 7.6 Hz, 2H), 4.27 (t, J = 7.2 Hz, 2H), 4.43 (t, J = 7.6 Hz, 2H), 6.81–6.89 (m, 3H,
Ar-H), 7.19–7.24 (m, 2H, Ar-H), 7.50–7.61 (m, 2H, Ar-H), 8.89 (s, 1H, Ar-H); 13C-NMR (CDCl3,
100 MHz): δ = 13.0 (CH3), 19.1 (CH2), 25.4 (CH2), 27.1 (CH2), 31.7 (CH2), 48.3 (CH2), 49.3 (CH2),
66.5 (CH2), 113.9 (CH), 120.6 (CH), 121.8 (CH), 121.9 (CH), 129.1 (CH), 136.2 (CH), 158.5 (C); IR
−
(NaCl) υmax 3131 (C-H Ar), 1598–1471 (C=C), 1163 (C-N), 1083 (C-O) cm−1; LCMS (M+)-NO3
273.3 found for C17H25N2O+.
1
1-Pentyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium tetrafluoroborate (25). H-NMR (CDCl3, 400 MHz):
δ = 0.87 (t, J = 7.2 Hz, 3H), 1.30–1.32 (m, 4H), 1.80–1.83 (m, 4H), 2.08 (quint, J = 7.6 Hz, 2H), 3.97
(t, J = 7.6 Hz, 2H), 4.15 (t, J = 7.2 Hz, 2H), 4.28 (t, J = 7.6 Hz, 2H), 6.85–6.92 (m, 3H, Ar-H),
7.23–7.27 (m, 2H, Ar-H), 7.35–7.42 (m, 2H, Ar-H), 8.90 (s, 1H, Ar-H); 13C-NMR (CDCl3, 100 MHz):
δ = 11.9 (CH3), 20.1 (CH2), 23.9 (CH2), 25.3 (CH2), 26.3 (CH2), 27.8 (CH2), 47.9 (CH2), 48.2 (CH2),
64.9 (CH2), 112.6 (CH), 119.0 (CH), 120.5 (CH), 120.6 (CH), 127.7 (CH), 133.8 (CH), 156.8 (C);
19F-NMR (CDCl3, 376.5 MHz): δ = −151.03; 11B-NMR (CDCl3, 128 MHz): δ = −0.93; IR (NaCl) υmax
−
3135 (C-H Ar), 1601–1475 (C=C), 1165 (C-N), 1081 (C-O) cm−1; LCMS (M+)-BF4 287.3 found
for C18H27N2O+.
1-Pentyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium hexafluorophospate (26). 1H-NMR (CDCl3, 400 MHz):
δ = 0.78 (t, J = 7.2 Hz, 3H), 1.21–1.23 (m, 4H), 1.67–1.75 (m, 4H), 1.95 (quint, J = 7.6 Hz, 2H), 3.86
(t, J = 7.6 Hz, 2H), 4.02 (t, J = 7.2 Hz, 2H), 4.13 (t, J = 7.6 Hz, 2H), 6.76–6.85 (m, 3H, Ar-H),
7.14–7.25 (m, 4H, Ar-H), 8.42 (s, 1H, Ar-H); 13C-NMR (CDCl3, 100 MHz): δ = 12.0 (CH3), 20.2
(CH2), 24.0 (CH2), 25.2 (CH2), 26.4 (CH2), 27.8 (CH2), 48.0 (CH2), 48.3 (CH2), 65.0 (CH2), 112.7
(CH), 119.1 (CH), 120.6 (CH), 120.7 (CH), 127.8 (CH), 133.2 (CH), 156.9 (C); 19F-NMR (CDCl3,
31
376.5 MHz): δ = −70.94 ; P NMR (CDCl3, 162 MHz): δ = −144.26 (sep, J = 712.8 Hz); IR (NaCl)
−
υmax 3132 (C-H Ar), 1599–1469 (C=C), 1167 (C-N), 1084 (C-O) cm−1; LCMS (M+)-PF6 287.3 found
for C18H27N2O+.
1
1-Pentyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium trifluroacetate (27). H-NMR (CDCl3, 400 MHz):
δ = 0.82 (t, J = 7.2 Hz, 3H), 1.21–1.29 (m, 4H), 1.74–1.82 (m, 4H), 2.05 (quint, J = 7.6 Hz, 2H), 3.93
(t, J = 7.6 Hz, 2H), 4.18 (t, J = 7.2 Hz, 2H), 4.34 (t, J = 7.6 Hz, 2H), 6.80–6.89 (m, 3H, Ar-H),
7.18–7.22 (m, 2H, Ar-H), 7.38–7.48 (m, 2H, Ar-H), 10.02 (s, 1H, Ar-H); 13C-NMR (CDCl3, 100
MHz): δ = 11.9 (CH3), 20.1 (CH2), 23.9 (CH2), 25.4 (CH2), 26.3 (CH2), 28.0 (CH2), 47.7 (CH2), 48.1
(CH2), 64.9 (CH2), 112.5 (CH), 119.0 (CH), 120.2 (CH), 120.5 (CH), 127.6 (CH), 135.1 (CH), 156.7
19
(C); F-NMR (CDCl3, 376.5 MHz): δ = −75.36 ; IR (NaCl) υmax 3135 (C-H Ar), 1599–1473 (C=C),
−
1165 (C-N), 1082 (C-O) cm−1; LCMS (M+)-CF3CO2 287.3 found for C18H27N2O+.

Molecules 2014, 19
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1
1-Pentyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium dicyanoamine (28). H-NMR (CDCl3, 400 MHz):
δ = 0.82 (t, J = 7.2 Hz, 3H), 1.21–1.30 (m, 4H), 1.75–1.84 (m, 4H), 2.06 (quint, J = 7.6 Hz, 2H), 3.94
(t, J = 7.6 Hz, 2H), 4.15 (t, J = 7.2 Hz, 2H), 4.30 (t, J = 7.6 Hz, 2H), 6.79–6.87 (m, 3H, Ar-H),
7.17–7.21 (m, 2H, Ar-H), 7.38–7.47 (m, 2H, Ar-H), 9.56 (s, 1H, Ar-H); 13C-NMR (CDCl3, 100 MHz):
δ = 11.9 (CH3), 20.0 (CH2), 23.9 (CH2), 25.4 (CH2), 26.3 (CH2), 27.8 (CH2), 47.9 (CH2), 48.2 (CH2),
64.8 (CH2), 112.5 (CH), 119.0 (CH), 120.5 (CH), 120.6 (CH), 127.6 (CH), 134.1 (CH), 156.6 (C); IR
(NaCl) υmax 3129 (C-H Ar), 1598–1471 (C=C), 1163 (C-N), 1079 (C-O) cm−1; LCMS (M+)-(CN)2N−
287.3 found for C18H27N2O+.
1-Pentyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium thiocyanate (29). 1H-NMR (CDCl3, 400 MHz): δ = 0.85
(t, J = 7.2 Hz, 3H), 1.24–1.33 (m, 4H), 1.78–1.87 (m, 4H), 2.09 (quint, J = 7.6 Hz, 2H), 3.97 (t, J = 7.6 Hz,
2H), 4.18 (t, J = 7.2 Hz, 2H), 4.33 (t, J = 7.6 Hz, 2H), 6.82–6.90 (m, 3H, Ar-H), 7.20–7.24 (m, 2H, Ar-H),
7.41–7.50 (m, 2H, Ar-H), 9.59 (s, 1H, Ar-H); 13C-NMR (CDCl3, 100 MHz): δ = 11.8 (CH3), 19.9
(CH2), 23.8 (CH2), 25.3 (CH2), 26.2 (CH2), 27.7 (CH2), 47.8 (CH2), 48.1 (CH2), 64.7 (CH2), 112.4
(CH), 118.9 (CH), 120.4 (CH), 120.5 (CH), 127.5 (CH), 134.0 (CH), 156.5 (C); IR (NaCl) υmax 3132
(C-H Ar), 1599–1471 (C=C), 1165 (C-N), 1085 (C-O) cm−1; LCMS (M+)-SCN− 287.3 found
for C18H27N2O+.
1-Pentyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium nitrate (30). 1H-NMR (CDCl3, 400 MHz): δ = 0.76 (t,
J = 7.2 Hz, 3H), 1.20–1.37 (m, 4H), 1.70–1.79 (m, 4H), 2.03 (quint, J = 7.6 Hz, 2H), 3.88 (t, J = 7.6 Hz,
2H), 4.17 (t, J = 7.2 Hz, 2H), 4.34 (t, J = 7.6 Hz, 2H), 6.74–6.83 (m, 3H, Ar-H), 7.12–7.16 (m, 2H, Ar-H),
13
7.44–7.57 (m, 2H, Ar-H), 10.07 (s, 1H, Ar-H); C-NMR (CDCl3, 100 MHz): δ = 13.7 (CH3), 21.9
(CH2), 25.8 (CH2), 27.2 (CH2), 28.1 (CH2), 29.8 (CH2), 49.5 (CH2), 49.9 (CH2), 66.7 (CH2), 114.3
(CH), 120.7 (CH), 122.2 (CH), 122.5 (CH), 129.4 (CH), 136.6 (CH), 158.5 (C); IR (NaCl) υmax 3130
−
(C-H Ar), 1599–1471 (C=C), 1163 (C-N), 1082 (C-O) cm−1; LCMS (M+)-NO3 287.3 found
for C18H27N2O+.
1
1-Hexyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium tetrafluoroborate (31). H-NMR (CDCl3, 400 MHz):
δ = 0.98 (t, J = 7.2 Hz, 3H), 1.18 (quint, J = 7.6 Hz, 2H), 1.43–1.45 (m, 4H), 1.73 (quint, J = 7.6 Hz,
2H), 1.81 (quint, J = 7.6 Hz, 2H), 2.00 (quint, J = 7.6 Hz, 2H), 4.00 (t, J = 7.6 Hz, 2H), 4.31 (quint,
J = 7.2 Hz, 2H), 4.50 (t, J = 7.6 Hz, 2H), 6.91–6.95 (m, 3H, Ar-H), 7.26–7.31 (m, 2H, Ar-H),
7.97–8.01 (m, 2H, Ar-H), 9.32 (s, 1H, Ar-H); 13C-NMR (CDCl3, 100 MHz): δ = 14.1 (CH3), 22.8
(CH2), 25.0 (CH2), 27.4 (CH2), 27.5 (CH2), 32.8 (CH2), 34.1 (CH2), 44.3 (CH2), 48.5 (CH2), 66.8
(CH2), 114.5 (CH), 120.4 (CH), 122.3 (CH), 122.5 (CH), 130.0 (CH), 136.2 (CH), 158.7 (C);
19F-NMR (CDCl3, 376.5 MHz): δ = −148.25; 11B-NMR (CDCl3, 128 MHz): δ = −1.26; IR (NaCl) υmax
−
3129 (C-H Ar), 1602–1474 (C=C), 1165 (C-N), 1082 (C-O) cm−1; LCMS (M+)-BF4 301.3 found
for C19H29N2O+.
1
1-Hexyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium hexafluorophospate (32). H-NMR (CDCl3, 400 MHz):
δ = 0.85 (t, J = 7.2 Hz, 3H), 1.12 (quint, J = 7.6 Hz, 2H), 1.25–1.34 (m, 4H), 1.79–1.88 (m, 4H), 2.10
(quint, J = 7.6 Hz, 2H), 3.97 (t, J = 7.6 Hz, 2H), 4.18 (t, J = 7.2 Hz, 2H), 4.33 (t, J = 7.6 Hz, 2H),
6.83–6.91 (m, 3H, Ar-H), 7.21–7.25 (m, 2H, Ar-H), 7.42–7.51 (m, 2H, Ar-H), 9.24 (s, 1H, Ar-H);
13C-NMR (CDCl3, 100 MHz): δ = 11.9 (CH3), 20.0 (CH2), 23.9 (CH2), 25.4 (CH2), 26.4 (CH2), 27.8

Molecules 2014, 19
11755
(CH2), 32.2 (CH2), 45.9 (CH2), 48.2 (CH2), 64.8 (CH2), 112.5 (CH), 119.0 (CH), 120.5 (CH), 120.6
(CH), 127.6 (CH), 134.2 (CH), 156.7 (C); 19F-NMR (CDCl3, 376.5 MHz): δ = −71.10; 31P NMR
(CDCl3, 162 MHz): δ = −144.16 (sep, J = 712.8 Hz); IR (NaCl) υmax 3133 (C-H Ar), 1599–1471
−
(C=C), 1165 (C-N), 1083 (C-O) cm−1; LCMS (M+)- PF6 301.3 found for C19H29N2O+.
1
1-Hexyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium trifluroacetate (33). H-NMR (CDCl3, 400 MHz):
δ = 0.79 (t, J = 7.2 Hz, 3H), 1.07 (quint, J = 7.6 Hz, 2H), 1.20–1.29 (m, 4H), 1.75–1.84 (m, 4H), 2.05
(quint, J = 7.6 Hz, 2H), 3.92 (t, J = 7.6 Hz, 2H), 4.13 (t, J = 7.2 Hz, 2H), 4.28 (t, J = 7.6 Hz, 2H),
6.79–6.87 (m, 3H, Ar-H), 7.17–7.23 (m, 2H, Ar-H), 7.38–7.47 (m, 2H, Ar-H), 10.15 (s, 1H, Ar-H);
13C-NMR (CDCl3, 100 MHz): δ = 13.0 (CH3), 21.1 (CH2), 24.0 (CH2), 26.5 (CH2), 27.6 (CH2), 28.9
(CH2), 33.4 (CH2), 47.0 (CH2), 49.3 (CH2), 65.9 (CH2), 113.6 (CH), 120.1 (CH), 121.6 (CH), 121.7
(CH), 128.7 (CH), 135.3 (CH), 157.8 (C); 19F-NMR (CDCl3, 376.5 MHz): δ = −75.41 ;IR (NaCl) υmax
−
3133 (C-H Ar), 1599–1472 (C=C), 1162 (C-N), 1080 (C-O) cm−1; LCMS (M+)-CF3CO2 301.3 found
for C19H29N2O+.
1
1-Hexyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium dicyanoamine (34). H-NMR (CDCl3, 400 MHz):
δ = 0.76 (t, J = 7.2 Hz, 3H), 1.04 (quint, J = 7.6 Hz, 2H), 1.20–1.37 (m, 4H), 1.70–1.79 (m, 4H), 2.03
(quint, J = 7.6 Hz, 2H), 3.88 (t, J = 7.6 Hz, 2H), 4.17 (t, J = 7.2 Hz, 2H), 4.34 (t, J = 7.6 Hz, 2H),
6.74–6.83 (m, 3H, Ar-H), 7.12–7.16 (m, 2H, Ar-H), 7.44–7.57 (m, 2H, Ar-H), 10.07 (s, 1H, Ar-H);
13C-NMR (CDCl3, 100 MHz): δ = 13.7 (CH3), 21.9 (CH2), 25.8 (CH2), 27.2 (CH2), 28.1 (CH2), 29.8
(CH2), 35.4 (CH2), 49.5 (CH2), 49.9 (CH2), 66.7 (CH2), 114.3 (CH), 120.7 (CH), 122.2 (CH), 122.5
(CH), 129.4 (CH), 136.6 (CH), 158.5 (C);IR (NaCl) υmax 3133 (C-H Ar), 1599–1471 (C=C), 1165
(C-N), 1082 (C-O) cm−1; LCMS (M+)-(CN)2N− 301.3 found for C19H29N2O+.
1-Hexyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium thiocyanate (35). 1H-NMR (CDCl3, 400 MHz):
δ = 0.82 (t, J = 7.2 Hz, 3H), 1.10 (quint, J = 7.6 Hz, 2H), 1.21–1.29 (m, 4H), 1.74–1.82 (m, 4H), 2.05
(quint, J = 7.6 Hz, 2H), 3.93 (t, J = 7.6 Hz, 2H), 4.18 (t, J = 7.2 Hz, 2H), 4.34 (t, J = 7.6 Hz, 2H),
6.80–6.89 (m, 3H, Ar-H), 7.18–7.22 (m, 2H, Ar-H), 7.38–7.48 (m, 2H, Ar-H), 10.02 (s, 1H, Ar-H);
13C-NMR (CDCl3, 100 MHz): δ = 11.9 (CH3), 20.1 (CH2), 23.9 (CH2), 25.4 (CH2), 26.3 (CH2), 28.0
(CH2), 34.0 (CH2), 47.7 (CH2), 48.1 (CH2), 64.9 (CH2), 112.5 (CH), 119.0 (CH), 120.2 (CH), 120.5
(CH), 127.6 (CH), 135.1 (CH), 156.7 (C); IR (NaCl) υmax 3128 (C-H Ar), 1602–1471 (C=C), 1164
(C-N), 1081 (C-O) cm−1; LCMS (M+)-SCN − 301.3 found for C19H29N2O+.
1-Hexyl-3-(4-phenoxybutyl)-1H-imidazol-3-ium nitrate (36). 1H-NMR (CDCl3, 400 MHz): δ = 0.85 (t,
J = 7.2 Hz, 3H), 1.14 (quint, J = 7.6 Hz, 2H), 1.24–1.33 (m, 4H), 1.78–1.87 (m, 4H), 2.09 (quint,
J = 7.6 Hz, 2H), 3.97 (t, J = 7.6 Hz, 2H), 4.18 (t, J = 7.2 Hz, 2H), 4.33 (t, J = 7.6 Hz, 2H), 6.82–6.90
(m, 3H, Ar-H), 7.20–7.24 (m, 2H, Ar-H), 7.41–7.50 (m, 2H, Ar-H), 9.59 (s, 1H, Ar-H); 13C-NMR
(CDCl3, 100 MHz): δ = 11.8 (CH3), 19.9 (CH2), 23.8 (CH2), 25.3 (CH2), 26.2 (CH2), 27.7 (CH2), 34.2
(CH2), 47.8 (CH2), 48.1 (CH2), 64.7 (CH2), 112.4 (CH), 118.9 (CH), 120.4 (CH), 120.5 (CH), 127.5
(CH), 134.0 (CH), 156.5 (C);IR (NaCl) υmax 3131 (C-H Ar), 1598–1470 (C=C), 1164 (C-N), 1081
−
(C-O) cm−1; LCMS (M+)-NO3 301.3 found for C19H29N2O+.

Molecules 2014, 19
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3.4. Determination of Minimum Inhibitory Concentrations
Minimum inhibitory concentrations (MICs) were determined using the broth microdilution method
based on recommended protocolemployed by the Clinical and Laboratory Standards Institute [41].
Tested compounds were dissolved in sterile, distilled water and diluted to a final concentration of
512 µg/mL in Mueller-Hinton broth (Becton Dickinson, Franklin Lakes, NJ, USA) [42]. Two-fold
serially diluted test compounds were dispensed into each of the 96 wells of a standard microdilution
plates. The direct colony suspension method was used for inoculum preparation. Bacterial suspension
was prepared by direct transfer of colonies from 24 h agar plates to Mueller Hinton broth.
Bacterial suspensions were adjusted using bacterial counting chamber to contain approximately
1 × 108 CFU/mL. A 50 µL volume of each bacterial suspension was mixed with 50 µL serially diluted
tested compound in 96 microdilution plate according to the microdilution method [43]. Uninoculated
wells were prepared as control samples.Plates were incubated at 35 °C for 24 h. The minimum
(inhibitory) bactericidal concentration was defined as the lowestconcentration of test compound
producing no visible growth. Confirmation for MIC, was achieved by transfer of aliquots from wells
containing no growth on to nutrient agar plates and tested for colony formation upon subculturing.
Given values of obtained MIC values are means of three independent experiments.
4. Conclusions
In summary, new eco-friendly 1-alkyl-3-(4-phenoxybutyl) imidazolium-based ionic liquids (ILs)
derivatives were prepared by using ultrasound irradiation. Many advantages for the ultrasound assisted
synthesis compared with the standard methods have been recorded. The ILs studied displayed a very
promising antimicrobial activity. Their activities are greatly affected by the alkyl chain length. The
study of the physicochemical properties, water content, biodegradability and solubility of the newly
synthesized ionic liquids will be will be discussed in details in the forthcoming paper.
Acknowledgments
We gratefully acknowledge the financial support from Taibah University through the deanship of
the scientific research (Grant 6084). T. Ben Hadda would like to thank the ACTELION; the
Biopharmaceutical Company of Swiss, for the molecular properties calculations.
Author Contributions
This work is part of a pharmacological field study carried out in Taibah University, Madinah, KSA.
The Ionic liquids were prepared and characterised by Mouslim Messali, Mohamed R. Aouad,
Adeeb Al-Sheikh Ali. The manuscript is written by Mouslim Messali. Taibi Ben Hadda and Belkheir
Hammouti help in illustrations and drafting of manuscript. Mohamed R. Aouad, Wael S. El-Sayed,
Adeeb Al-Sheikh Ali collected data in the field and help in compounds identification. The biological
activity is carried out by Wael S. El-Sayed. Taibi Ben Hadda provided technical expertise in compiling
POM data in to the manuscript. All the authors read and approved the final manuscript.

Molecules 2014, 19
11757
Conflicts of Interest
The authors declare no conflict of interest.
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