Download Dual Amino-Functionalised Phosphonium Ionic Liquids for CO2

FULL PAPER
DOI: 10.1002/chem.200801184
Dual Amino-Functionalised Phosphonium Ionic Liquids for CO2 Capture
Yanqiang Zhang,[a, b] Suojiang Zhang,*[a] Xingmei Lu,[a] Qing Zhou,[a] Wei Fan,[c] and
XiangPing Zhang[a]
Abstract: A series of 20 dual aminofunctionalised phosphonium ionic liquids, (3-aminopropyl)tributylphosphonium amino acid salts ([aP4443][AA], in
which [AA] = [Ala] , [Arg] , [Asn] ,
[Asp] , [Cys] , [Gln] , [Glu] , [Gly] ,
[His] , [Ile] , [Leu] , [Lys] , [Met] ,
[Phe] , [Pro] , [Ser] , [Thr] , [Trp] ,
[Tyr] and [Val] ), has been prepared.
Their physicochemical properties, such
as density, viscosity, glass transition and
thermal decomposition temperatures
and conductivity, have been deter-
mined. In particular, the [aP4443][AA]
ionic liquids (ILs) have low glass transition temperatures ranging from 69.7
to 29.6 8C and high decomposition
temperatures (all above 200 8C). The
effects of the variation of the structure
of [AA] on the above physicochemiKeywords: amino acids · carbon
dioxide capture · ionic liquids ·
phosphorus
·
physicochemical
properties
Introduction
Carbon dioxide (CO2) as the most significant greenhouse gas
has attracted worldwide attention.[1] One of the most commercially utilised technologies for CO2 recovery is the chemical absorption of CO2 by aqueous amine solutions,[2–4] which
has been shown to have many disadvantages, for example,
the uptake of water into the gas stream requires an additional
drying process, the evaporation of water increases the energy
demand and cost of the procedure and the loss of volatile
amines can cause environmental pollution. Therefore, a nonvolatile solvent that could facilitate CO2 capture without the
loss of solvent into the gas stream would be aNGU RET CHA dvantageous.
[a] Dr. Y. Zhang, Prof. Dr. S. Zhang, Dr. X. Lu, Dr. Q. Zhou,
Dr. X. Zhang
Key Laboratory of Green process and Engineering
Institute of Process Engineering, Chinese Academy of Sciences
P.O. Box 353, Beijing, 100080 (China)
Fax: (+ 86) 10-8262-7080
E-mail: [email protected]
[b] Dr. Y. Zhang
Graduate University of Chinese Academy of Sciences
Chinese Academy of Sciences
Beijing, 100049 (China)
[c] W. Fan
Kaifeng University
Kaifeng, 475004 (China)
Chem. Eur. J. 2009, 15, 3003 – 3011
cal properties are discussed. Furthermore, the CO2 absorption of [aP4443]ACHTUNGRE[Gly], [aP4443]ACHTUNGRE[Ala], [aP4443]ACHTUNGRE[Val] and
[aP4443]ACHTUNGRE[Leu], taken as examples, was
investigated. It was found that the supported absorption of CO2 by the
[aP4443][AA] ILs almost reaches equilibrium within 80 min, the chemical absorption of CO2 by the [aP4443][AA]
ILs approaches 1 mol CO2 per mol
ionic liquid (twice that reported
before) and the [aP4443][AA] ILs can be
repeatedly recycled for CO2 uptake.
Ionic liquids (ILs), which have many unique properties,[5–7]
for example, extremely low vapour pressure, a broad range
of liquid temperature, high thermal and chemical stability,
and tuneable physicochemical characteristics, have been
widely studied as a potential substitute of aqueous amine
solutions for CO2 capture. Many research groups, especially
that of Brennecke, have carried out outstanding research
into the solubility of CO2 in ILs.[8, 9] It has been found that
CO2 is very soluble in imidazolium ILs,[8] its solubility increasing with increasing pressure and decreasing with increasing temperature. As well as an increase in the alkyl
chain length of the cations leading to an increase in the CO2
absorption, the anions also play a big role in CO2 absorption
by IL;[10] The solubility of CO2 is commonly higher in ILs
with fluoroalkyl groups in the anion (tris(trifluoromethylsulfonyl)methide, [methide] , and bis(trifluoromethylsulfonyl)imide, [Tf2N] ) and lower in ILs with non-fluorinated inorganic anions (nitrate, [NO3] , and dicyanamide, [DCA] ).[11]
However, the physical absorption of CO2 by ILs as an
answer to the CO2 problem still has a very long way to go
because it is usually necessary to perform the procedure
under extreme conditions, such as a very high pressure
(90 bar or ever higher), and for a very long time for the
equilibrium to be reached (up to 24 h).[12–14]
Inspiringly, Bates et al. showed that amino-functionalised
ILs were another good choice for CO2 absorption and pro-
2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3003
posed an absorption mechanism.[15] There are mainly two
types of amino-functionalised ILs for CO2 absorption: ILs in
which the cations are functionalised with an appended
amine group, for example, 1-(3-aminopropyl)-3-butylimidACHTUNGREazolium tetrafluoroborate ([aPbim]ACHTUNGRE[BF4]),[15] which is not as
stable as phosphonium IL,[16] and ILs in which the anions
are functionalised with an appended amine group,[16–19] for
example, the tetrabutylphosphonium aminoethanoic acid
salt ([P4444]ACHTUNGRE[Gly]). These two types of functional ILs can
absorb CO2 in a ratio of 0.5 mol CO2 per mol IL at room
temperature and normal pressure. As a medium for CO2
capture, higher absorption capacity and better thermal stability of the functional ILs are always preferred.
In this work we have tried to synthesise dual amino-functionalised imidazolium, pyridinium, ammonium and phosphonium ILs for CO2 capture, in which both the cation and
the anion are functionalised with an appended amine group,
starting from 1-methylimidazole, pyridine, tributylamine,
tributylphosphine, 3-bromopropylamine hydrobromide and
glycine. The syntheses were performed in accord with the
methods of Bates and Ohno and their co-workers.[15, 17, 18] As
a result, only the 1-(3-aminopropyl)-3-methylimidazolium
aminoethanoic acid ([aPmim]ACHTUNGRE[Gly]) and (3-aminopropyl)tributylphosphonium aminoethanoic acid ([aP4443]ACHTUNGRE[Gly]) salts
could be obtained. Both [aPmim]ACHTUNGRE[Gly] and [aP4443]ACHTUNGRE[Gly] are
liquid at room temperature. Thermal gravimetric analysis
(TGA) showed that [aPmim]ACHTUNGRE[Gly] was very unstable and
gradually decomposed above 80 8C, perhaps because the
2-H proton of the imidazole ring was too active under
highly alkaline conditions, whereas [aP4443]ACHTUNGRE[Gly] had a thermal decomposition temperature (Td) of 281 8C. Thus
[aP4443] + was selected as the ideal cation and for a systematic investigation another 19 dual amino-functionalised phosphonium ILs ([aP4443][AA]) were prepared from tributylphosphine and 19 other natural amino acids by the same
procedures. Moreover, the absorption of CO2 by [aP4443]ACHTUNGRE[Gly], [aP4443]ACHTUNGRE[Ala], [aP4443]ACHTUNGRE[Val], and [aP4443]ACHTUNGRE[Leu],as examples, were measured.
Scheme 1. Structure of the dual amino-functionalised phosphonium ILs
([aP4443][AA]). [AA] = [Ala] , [Arg] , [Asn] , [Asp] , [Cys] , [Gln] ,
[Glu] , [Gly] , [His] , [Ile] , [Leu] , [Lys] , [Met] , [Phe] , [Pro] ,
[Ser] , [Thr] , [Trp] , [Tyr] and [Val] .
the glass transition (Tg) and thermal decomposition (Td)
temperatures, and conductivity (s) were determined and are
discussed below.
Density: The densities of the [aP4443][AA] ILs vary from
0.9661 to 1.0596 g cm 3 at 25 8C (Table 1), which are lower
than those of the corresponding imidazolium, pyridinium or
Table 1. Densities of the [aP4443][AA] ILs at different temperatures.[a]
25 8C
35 8C
1 [g cm 3]
45 8C
55 8C
0.9858
0.9943
1.0458
–
1.0496
1.0571
1.0161
0.9973
0.9993
0.9742
0.9661
0.9991
1.0176
1.0220
1.0047
1.0262
1.0126
1.0596
1.0429
0.9750
0.9798
0.9882
1.0399
–
1.0434
1.0509
1.0106
0.9914
0.9938
0.9681
0.9600
0.9931
1.0114
1.0160
0.9988
1.0200
1.0064
1.0540
1.0370
0.9690
0.9738
0.9821
1.0341
–
1.0373
1.0448
1.0051
0.9855
0.9883
0.9621
0.9540
0.9872
1.0053
1.0100
0.9929
1.0138
1.0003
1.0484
1.0311
0.9630
IL
CHTUNGRE[A aP4443]ACHTUNGRE[Ala]
ACHTUNGRE[aP4443]ACHTUNGRE[Arg]
ACHTUNGRE[aP4443]ACHTUNGRE[Asn]
ACHTUNGRE[aP4443]ACHTUNGRE[Asp]
ACHTUNGRE[aP4443]ACHTUNGRE[Cys]
ACHTUNGRE[aP4443]ACHTUNGRE[Gln]
ACHTUNGRE[aP4443]ACHTUNGRE[Glu]
ACHTUNGRE[aP4443]ACHTUNGRE[Gly]
ACHTUNGRE[aP4443]ACHTUNGRE[His]
ACHTUNGRE[aP4443]ACHTUNGRE[Ile]
ACHTUNGRE[aP4443]ACHTUNGRE[Leu]
ACHTUNGRE[aP4443]ACHTUNGRE[Lys]
ACHTUNGRE[aP4443]ACHTUNGRE[Met]
ACHTUNGRE[aP4443]ACHTUNGRE[Phe]
ACHTUNGRE[aP4443]ACHTUNGRE[Pro]
ACHTUNGRE[aP4443]ACHTUNGRE[Ser]
ACHTUNGRE[aP4443 ACHTUNGRE[Thr]
ACHTUNGRE[aP4443]ACHTUNGRE[Trp]
ACHTUNGRE[aP4443]ACHTUNGRE[Tyr]
ACHTUNGRE[aP4443]ACHTUNGRE[Val]
0.9680
0.9761
1.0283
–
1.0313
1.0387
0.9997
0.9797
0.9829
0.9561
0.9481
0.9812
0.9993
1.0040
0.9869
1.0077
0.9943
1.0428
1.0252
0.9570
65 8C
75 8C
0.9622
0.9701
1.0225
0.9963
1.0254
1.0326
0.9942
0.9739
0.9774
0.9503
0.9422
0.9754
0.9933
0.9982
0.9812
1.0017
0.9884
1.0373
1.0195
0.9511
0.9564
0.9642
1.0167
0.9908
1.0195
1.0265
0.9889
0.9682
0.9720
0.9444
0.9363
0.9696
0.9874
0.9923
0.9754
0.9958
0.9824
1.0318
1.0138
0.9453
[a] “–”: These values can not be measured by the method used because
the sample is a solid.
Results and Discussion
The resulting (3-aminopropyl)tributylphosphonium amino
acid ILs ([aP4443][AA]) were obtained by neutralising
(3-aminopropyl)tributylphosphonium hydroxide ([aP4443]
[OH]) with 20 natural amino acids. [aP4443][OH] was prepared from (3-aminopropyl)tributylphosphonium bromide
([aP4443]Br) using an anion-exchange resin, which is a good
method for obtaining halide-free ILs. The structures and abbreviations of the [aP4443][AA] ILs employed in this study
are shown in Scheme 1.
All the [aP4443][AA] ILs are liquids at room temperature
except [aP4443]ACHTUNGRE[Asp]. They were characterised by NMR and
IR spectroscopy and elemental analysis. The characterisation data are in good agreement with the expected structures and compositions. Also, the physicochemical properties of the [aP4443][AA] ILs, such as density (1), viscosity (h),
3004
www.chemeurj.org
ammonium ILs mainly because [aP4443] + is larger and so
weakens the ion–ion interactions and blocks ion packing.[20–22] Moreover, the data in Table 1 reveal that the structures of [AA] influence the densities of the [aP4443][AA]
ILs significantly. Elongating the alkyl side-chains of [AA]
increases the free volume of the ILs thereby decreasing
their density, for example, [aP4443]ACHTUNGRE[Gly] > [aP4443]ACHTUNGRE[Ala] >
[aP4443]ACHTUNGRE[Val] > [aP4443]ACHTUNGRE[Leu]. However, the grafting of functional groups onto the [AA] anions increases the densities
of the [aP4443][AA] ILs because the densities of the functional groups are greater than those of n-alkyl chains. For example, SH, or OH, is grafted onto [Ala] and the densities of
[aP4443]ACHTUNGRE[Cys] and [aP4443]ACHTUNGRE[Ser], at 25 8C, are 0.0638 and
0.0404 g cm 3 higher than that of [aP4443]ACHTUNGRE[Ala], respectively.
In general, the [aP4443][AA] ILs with aromatic rings in the
[AA] anions have a relatively high density, for example,
2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 3003 – 3011
Amino-Functionalised Phosphonium Ionic Liquids
FULL PAPER
[aP4443]ACHTUNGRE[Trp], [aP4443]ACHTUNGRE[Tyr] and [aP4443]ACHTUNGRE[Phe] (1.0596, 1.0429
and 1.0220 g cm 3 at 25 8C, respectively). Interestingly, it was
found that the densities of the [aP4443][AA] ILs decrease linearly with increasing temperature (correlation coefficient
R > 0.99), as shown in Figure 1. This phenomenon requires
further study.
Figure 1. Variation in the densities of the [aP4443][AA] ILs with
ACHTUNGREtemperature.
cosity of a [aP4443][AA] IL at 25 8C is still as high as
713.9 mPa s. Also, the structures of [AA] have a big effect
on the viscosities of the [aP4443][AA] ILs. An increase of the
chain length of [AA] decreases the mobility of the ILs
leading to an increase in the viscosities of the [aP4443][AA]
ILs such that [aP4443]ACHTUNGRE[Gly] < [aP4443]ACHTUNGRE[Ala] < [aP4443]ACHTUNGRE[Val] <
[aP4443]ACHTUNGRE[Leu] (713.9 < 758.0 < 888.2 < 1193.8 mPa s at 25 8C).
The presence of a large ring in the [AA] anion also decreases the mobility of the ILs, leading to [aP4443][AA] ILs
with higher viscosities, for example, the viscosities of
[aP4443]ACHTUNGRE[Trp], [aP4443]ACHTUNGRE[Tyr], and [aP4443]ACHTUNGRE[His] are all above
2000 mPa s at 25 8C. The grafting of an SH or OH functional
group onto the [AA] anion increases the viscosity of the
[aP4443][AA] due to the increased tendency to form hydrogen bonds, for example, [aP4443]ACHTUNGRE[Cys], [aP4443]ACHTUNGRE[Ser] and
[aP4443]ACHTUNGRE[Thr] each have a higher viscosity than the corresponding [aP4443][AA] without the functional group. Unlike
density, temperature has a strong effect on the viscosities of
the [aP4443][AA] ILs. Figure 2 shows that an increase in temperature can lead to a rapid decrease in the viscosities of
[aP4443][AA] at a low temperature, for example, 25 8C, and
at higher temperatures, the rate of decrease of the viscosities
of [aP4443][AA] is reduced.
Viscosity: The viscosities of the [aP4443][AA] ILs (Table 2)
are essentially determined by the flexibility of the chain, the
strength of van der Waals interactions, and their tendency to
form hydrogen bonds.[22–24] Mainly because the larger size of
[aP4443] + leads to an increase in the number of van der
Waals interactions and the two appended amine groups increase the number of hydrogen bonds, the [aP4443][AA] ILs
have higher viscosities than most other ILs. The lowest vis-
Table 2. Viscosities of the [aP4443][AA] ILs at different temperatures.[a]
25 8C
35 8C
h [mPa s]
45 8C
55 8C
65 8C
75 8C
758.0
–
–
–
–
–
–
713.9
–
1408.1
1193.8
1432.2
766.8
1985.0
1772.8
1341.7
1790.5
–
–
888.2
382.8
1429.3
–
–
–
–
–
366.4
–
658.5
565.6
691.4
396.1
923.4
803.1
627.8
810.8
–
–
434.2
210.6
688.3
–
–
–
–
–
204.1
–
338.2
293.8
364.5
224.3
452.1
400.2
323.2
406.4
–
–
231.4
80.1
204.9
853.8
854.3
1543.6
748.0
758.9
79.3
565.3
114.2
101.3
125.6
83.5
140.4
129.0
110.3
129.1
–
–
84.4
54.3
124.8
447.1
481.8
775.5
377.7
434.9
54.2
313.7
73.8
66.2
81.7
55.9
88.2
81.8
71.6
84.5
–
1291.0
56.3
IL
CHTUNGRE[A aP4443]ACHTUNGRE[Ala]
ACHTUNGRE[aP4443]ACHTUNGRE[Arg]
ACHTUNGRE[aP4443]ACHTUNGRE[Asn]
ACHTUNGRE[aP4443]ACHTUNGRE[Asp]
ACHTUNGRE[aP4443]ACHTUNGRE[Cys]
ACHTUNGRE[aP4443]ACHTUNGRE[Gln]
ACHTUNGRE[aP4443]ACHTUNGRE[Glu]
ACHTUNGRE[aP4443]ACHTUNGRE[Gly]
ACHTUNGRE[aP4443]ACHTUNGRE[His]
ACHTUNGRE[aP4443]ACHTUNGRE[Ile]
ACHTUNGRE[aP4443]ACHTUNGRE[Leu]
ACHTUNGRE[aP4443]ACHTUNGRE[Lys]
ACHTUNGRE[aP4443]ACHTUNGRE[Met]
ACHTUNGRE[aP4443]ACHTUNGRE[Phe]
ACHTUNGRE[aP4443]ACHTUNGRE[Pro]
ACHTUNGRE[aP4443]ACHTUNGRE[Ser]
ACHTUNGRE[aP4443]ACHTUNGRE[Thr]
ACHTUNGRE[aP4443]ACHTUNGRE[Trp]
ACHTUNGRE[aP4443]ACHTUNGRE[Tyr]
ACHTUNGRE[aP4443]ACHTUNGRE[Val]
125.1
360.2
1700.7
1632.5
–
1653.3
1417.5
122.7
1094.9
189.2
166.0
206.2
137.8
241.8
218.9
181.5
223.2
–
–
134.3
[a] “–”: above 2000 mPa s (the measurement range 0–2000 mPa s).
Chem. Eur. J. 2009, 15, 3003 – 3011
Figure 2. Variation in the viscosities of the [aP4443][AA] ILs with
ACHTUNGREtemperature.
Glass transition and thermal decomposition temperatures:
Table 3 shows that the [aP4443][AA] ILs have glass transition
temperatures (Tg) ranging from 69.7 to 29.6 8C, lower
than those of the corresponding [Emim][AA] ILs.[17] In particular, for ILs with the anions [Asp] , [Gln] , [Glu] , and
[Arg] , the differences in Tg are 58.9, 40.4, 40.3 and 38.3 8C,
respectively. The thermal decomposition temperatures (Td)
of the [aP4443][AA] ILs are all above 200 8C and half of the
20 [aP4443][AA] ILs have Td values above 280 8C, which is
far higher than that of [aPmim]ACHTUNGRE[Gly] (Td, 80 8C) and higher
than those of the [Emim][AA] (Td values are all less than
250 8C)[16] and [NR1R2R3R4][AA] ILs.[19]
2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3005
S. Zhang et al.
Table 3. Thermal properties of [aP4443][AA] and other ILs.
IL
ACHTUNGRE[aP4443]ACHTUNGRE[Ala]
ACHTUNGRE[aP4443]ACHTUNGRE[Arg]
ACHTUNGRE[aP4443]ACHTUNGRE[Asn]
ACHTUNGRE[aP4443]ACHTUNGRE[Asp]
ACHTUNGRE[aP4443]ACHTUNGRE[Cys]
ACHTUNGRE[aP4443]ACHTUNGRE[Gln]
ACHTUNGRE[aP4443]ACHTUNGRE[Glu]
ACHTUNGRE[aP4443]ACHTUNGRE[Gly]
ACHTUNGRE[aP4443]ACHTUNGRE[His]
ACHTUNGRE[aP4443]ACHTUNGRE[Ile]
ACHTUNGRE[aP4443]ACHTUNGRE[Leu]
ACHTUNGRE[aP4443]ACHTUNGRE[Lys]
ACHTUNGRE[aP4443]ACHTUNGRE[Met]
ACHTUNGRE[aP4443]ACHTUNGRE[Phe]
ACHTUNGRE[aP4443]ACHTUNGRE[Pro]
ACHTUNGRE[aP4443]ACHTUNGRE[Ser]
ACHTUNGRE[aP4443]ACHTUNGRE[Thr]
ACHTUNGRE[aP4443]ACHTUNGRE[Trp]
ACHTUNGRE[aP4443]ACHTUNGRE[Tyr]
ACHTUNGRE[aP4443]ACHTUNGRE[Val]
Tg [8C]
67.3
56.3
42.2
53.9
36.1
34.4
52.3
69.7
51.6
58.3
61.4
60.7
64.8
51.3
55.4
52.7
55.8
29.6
40.7
62.5
Td [8C]
283
228
230
254
202
297
262
281
300
284
283
292
275
282
280
254
245
277
231
293
CHTUNGRE[A Emim][AA][a]
Tg [8C] Td [8C]
57
18
16
5
19
6
12
65
24
52
51
47
57
36
48
49
40
31
23
52
212
< 250
< 250
< 250
173[c]
< 250
< 250
< 250
< 250
< 250
< 250
< 250
< 250
< 250
< 250
< 250
< 250
< 250
< 250
< 250
Other ILs[b]
Td [8C]
ACHTUNGRE[N1111]ACHTUNGRE[L-Ala] 219
ACHTUNGRE[N2222]ACHTUNGRE[L-Ala] 185
ACHTUNGRE[N1111]ACHTUNGRE[b-Ala] 193
ACHTUNGRE[N2222]ACHTUNGRE[b-Ala] 184
ACHTUNGRE[N4444]ACHTUNGRE[b-Ala] 180
ACHTUNGRE[N1111]ACHTUNGRE[Gly] 181
ACHTUNGRE[N4444]ACHTUNGRE[Gly] 179
ACHTUNGRE[N1111]ACHTUNGRE[Val] 223
ACHTUNGRE[N4444]ACHTUNGRE[Val] 185
ACHTUNGRE[aPmim]ACHTUNGRE[Gly] 80[d]
[a] From ref. [16]. [b] From ref. [19]. [c] From ref. [17]. [d] From our
ACHTUNGREexperiments.
As well as the cation ([aP4443] + ),[20, 25–27] the structures of
[AA] also have a big effect on the Tg and Td values of the
[aP4443][AA] ILs. Table 3 shows that a better flexibility of
[AA] lowers the Tg of the [aP4443][AA] ILs. As [Gly] ,
[Ala] , [Val] and [Leu] have short and linear alkyl sidechains, [aP4443]ACHTUNGRE[Gly], [aP4443]ACHTUNGRE[Ala], [aP4443]ACHTUNGRE[Val] and [aP4443]ACHTUNGRE[Leu] have low Tg values: 69.7, 67.3, 62.5 and 61.4 8C,
respectively. The Tg values decrease in the order [aP4443]ACHTUNGRE[Gly] < [aP4443]ACHTUNGRE[Ala] < [aP4443]ACHTUNGRE[Val] < [aP4443]ACHTUNGRE[Leu], which corresponds to an increasing length of the alkyl side-chain in
[AA] . [aP4443]ACHTUNGRE[Trp], [aP4443]ACHTUNGRE[Tyr], [aP4443]ACHTUNGRE[Phe] and [aP4443]ACHTUNGRE[His], which have a ring in the side-chain of the [AA] ,
have high Tg values: 29.6, 40.7, 51.3 and 51.6 8C, respectively. [Gly] and [Val] contain one CH2 less than
[Ala] and [Leu] and correspondingly the Tg values of
[aP4443]ACHTUNGRE[Gly] and [aP4443]ACHTUNGRE[Val] are 2.4 and 1.1 8C lower than
those of [aP4443]ACHTUNGRE[Ala] and [aP4443]ACHTUNGRE[Leu], respectively.
In contrast to the Tg values, the active functional groups
on [AA] and the high negative charge density of [AA]
lower the thermal decomposition temperatures of the
[aP4443][AA] ILs. Thus, [aP4443]ACHTUNGRE[Cys], [aP4443]ACHTUNGRE[Tyr], [aP4443]ACHTUNGRE[Thr] and [aP4443]ACHTUNGRE[Ser] have low Td values (202, 231, 245 and
254 8C, respectively) because [Cys] , [Tyr] , [Thr] and
[Ser] are functionalised by SH or OH moieties. As [His] ,
[Phe] , [Pro] and [Trp] have a ring in their side-chains
and low negative charge densities, [aP4443]ACHTUNGRE[His], [aP4443]ACHTUNGRE[Phe], [aP4443]ACHTUNGRE[Pro] and [aP4443]ACHTUNGRE[Trp] have high Td values of
300, 282, 280 and 277 8C, respectively. [aP4443]ACHTUNGRE[Val], [aP4443]ACHTUNGRE[Lys], [aP4443]ACHTUNGRE[Ile], [aP4443]ACHTUNGRE[Leu], [aP4443]ACHTUNGRE[Ala] and [aP4443]ACHTUNGRE[Gly] all have Td values above 280 8C because the anions
only have alkyl side-chains, which also results in a low negative charge density.
3006
www.chemeurj.org
Conductivity: The conductivities of the [aP4443][AA] ILs at
25 8C are between 1.86 10 7 and 1.40 10 4 S cm 1
(Table 4). It is well known that conductivity is mainly depenTable 4. Conductivities of the [aP4443][AA] ILs.
IL
s [S cm 1]
ACHTUNGRE[aP4443]ACHTUNGRE[Ala]
ACHTUNGRE[aP4443]ACHTUNGRE[Arg]
ACHTUNGRE[aP4443]ACHTUNGRE[Asn]
ACHTUNGRE[aP4443]ACHTUNGRE[Asp]
ACHTUNGRE[aP4443]ACHTUNGRE[Cys]
ACHTUNGRE[aP4443]ACHTUNGRE[Gln]
ACHTUNGRE[aP4443]ACHTUNGRE[Glu]
ACHTUNGRE[aP4443]ACHTUNGRE[Gly]
ACHTUNGRE[aP4443]ACHTUNGRE[His]
ACHTUNGRE[aP4443]ACHTUNGRE[Ile]
1.06 10
1.54 10
1.82 10
–[a]
1.05 10
1.17 10
7.23 10
1.40 10
5.95 10
3.14 10
4
5
6
6
6
6
4
6
5
IL
s [S cm 1]
ACHTUNGRE[aP4443]ACHTUNGRE[Leu]
ACHTUNGRE[aP4443]ACHTUNGRE[Lys]
ACHTUNGRE[aP4443]ACHTUNGRE[Met]
ACHTUNGRE[aP4443]ACHTUNGRE[Phe]
ACHTUNGRE[aP4443]ACHTUNGRE[Pro]
ACHTUNGRE[aP4443]ACHTUNGRE[Ser]
ACHTUNGRE[aP4443]ACHTUNGRE[Thr]
ACHTUNGRE[aP4443]ACHTUNGRE[Trp]
ACHTUNGRE[aP4443]ACHTUNGRE[Tyr]
ACHTUNGRE[aP4443]ACHTUNGRE[Val]
4.99 10
3.78 10
7.95 10
1.90 10
3.12 10
5.37 10
4.25 10
1.86 10
8.93 10
5.15 10
5
5
5
5
5
5
5
7
7
5
[a] Could not be measured in the method used because the sample is
solid.
dent on the number and mobility of charge carriers.[25, 26, 28, 29]
The [aP4443][AA] ILs have a similar number of charge carriers for a similar molecular mass, density and size. From
Figure 3 it can be seen for most of the [aP4443][AA] ILs that
a linear relationship exists between their conductivity
(25 8C) and glass transition temperature, which indicates
that the conductivities of the [aP4443][AA] ILs are mainly
governed by the mobility of the charge carriers. Furthermore, the relatively low conductivities of the [aP4443][AA]
ILs maybe due to the low mobility of the charge carriers,
which is caused by a high number of hydrogen-bonding
ACHTUNGREinteractions.
Figure 3. Relationship between the conductivities (S cm 1, 25 8C) and
glass transition temperatures of the [aP4443][AA] ILs.
CO2 absorption: Owing to their relatively low viscosities,
[aP4443]ACHTUNGRE[Gly], [aP4443]ACHTUNGRE[Ala], [aP4443]ACHTUNGRE[Val] and [aP4443]ACHTUNGRE[Leu],
taken as examples, were placed in a special glass container
with a magnetic stirrer at room temperature. CO2 dried with
P2O5 was then fed into the container through a PTEE pipeline at atmospheric pressure. Parafilm was used to prevent
2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 3003 – 3011
Amino-Functionalised Phosphonium Ionic Liquids
the humid atmosphere from entering the system. The viscosities of the [aP4443][AA] ILs increased markedly with CO2
absorption, which made agitation difficult and eventually it
stopped. After 2 h, absorption of less than 0.2 mol
CO2 per mol IL had been achieved for the four [aP4443][AA]
ILs (Figure 4) because the increasing viscosity of the [aP4443]
[AA] ILs reduced the CO2 diffusion too much.
FULL PAPER
physical and chemical absorption of CO2 by the [aP4443][AA]
ILs. How to distinguish the chemical absorption of CO2 by
the [aP4443][AA] ILs from the other two components is critical for the study of the absorption process. We present a
method that could provide an answer to the above question.
[aP4443]ACHTUNGRE[Gly] and [aP4443]ACHTUNGRE[Ala] were used as examples for this
study. Moreover another two ILs, the tetrabutylphosphonium acetic acid ([P4444][Ac]) and propionic acid ([P4444][Pr])
salts obtained in our laboratory, were also studied. Comparison of [aP4443]ACHTUNGRE[Gly] with [P4444][Ac] and [aP4443]ACHTUNGRE[Ala] with
[P4444][Pr] show that they almost have the same structures
except for the two appended amine groups (for structures
see below).
Figure 4. Direct absorption of CO2 by the [P4443][AA] ILs.
To enhance the absorption rate, supported absorption of
CO2 by [aP4443]ACHTUNGRE[Gly], [aP4443]ACHTUNGRE[Ala], [aP4443]ACHTUNGRE[Val] and [aP4443]ACHTUNGRE[Leu] on porous SiO2 was performed according to the procedure used in our previous work,[18] which can overcome the
high viscosities of the [aP4443][AA] ILs such that CO2 absorption is almost complete in 80 min (Figure 5).
However, supported CO2 absorption process is more complicated as it includes the physical absorption of CO2 by
porous SiO2, which cannot be omitted because the porous
SiO2 has a big surface area (about 500 m2 g 1), as well as the
The supported CO2 absorption of [aP4443]ACHTUNGRE[Gly], [P4444]
[Ac], [aP4443]ACHTUNGRE[Ala] and [P4444][Pr] was performed under the
same experimental conditions according to the procedure
described previously.[18] Thus, the chemical absorption of
CO2 by [aP4443]ACHTUNGRE[Gly] and [aP4443]ACHTUNGRE[Ala] is the absorption by
the [Ac] and [Pr] salts subtracted from the values for the
[Gly] and [Ala] salts, approximately (see key in Figure 6).
The results show that the ratio of chemical absorption of
CO2 by [aP4443]ACHTUNGRE[Gly] and [aP4443]ACHTUNGRE[Ala] is close to 1 mol
CO2 per mol IL (twice that reported before), which is consistent with the absorption mechanism proposed by Bates
and Zhang and their co-workers.[15, 18]
Moreover, the [aP4443][AA] ILs can desorb CO2 under reduced pressure and increasing temperature (60 8C), and be
repeatedly recycled for CO2 uptake. The recycling of
[aP4443]ACHTUNGRE[Gly] for the chemical absorption of CO2 is shown in
Figure 7. Although the rate and capacity of the absorption
decrease steadily, the loss of absorption rate and capacity is
not very great for five cycles. With more recycling, the absorption rate and capacity decrease more quickly.
Conclusion
Figure 5. Supported absorption of CO2 by the [aP4443][AA] ILs.
Chem. Eur. J. 2009, 15, 3003 – 3011
A series of 20 dual amino-functionalised phosphonium ionic
liquids ([aP4443][AA]) has been prepared. Their physico-
2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3007
S. Zhang et al.
Experimental Section
Tri-n-butylphosphine (Beijing Ouhe Technology Co. Ltd., China) and
3-bromopropylamine hydrobromide (Shanghai Mayao Chemical Technology Co., Ltd., China) were of analytical grade. Twenty natural amino
acids, namely (l-alanine (Ala), l-arginine (Arg), l-asparagine (Asn),
l-aspartic acid (Asp), l-cysteine (Cys), l-glutamine (Gln), l-glutamic
acid (Glu), glycine (Gly), l-histidine (His), l-isoleucine (Ile), l-leucine
(Leu), l-lysine (Lys), l-methionine (Met), l-phenylalanine (Phe), l-proline (Pro), l-serine (Ser), l-threonine (Thr), l-tryptophan (Trp), l-tyrosine (Tyr) and l-valine (Val), were of biotechnology grade and purchased
from Beijing Solarbio Science & Technology Co., Ltd., China. Acetonitrile, ethanol, n-hexane and anion-exchange resin 711(Cl) were of analytical grade and purchased from the Beijing Chemical Reagents
ACHTUNGRECompany, China.
1
Figure 6. Chemical absorption of CO2 by [aP4443]ACHTUNGRE[Gly] and [aP4443]ACHTUNGRE[Ala].
H and 13C NMR spectra were recorded on an Bruker ARX400 spectrometer at 400 MHz with tetramethylsilane as the standard. IR spectra
were recorded on a Thermo Nicolet 380 spectrometer. Elemental analysis
was performed on a Vario EL element analyser. Densities and viscosities
were measured on Paar DMA5000 density and Paar AMVn viscosity
meters, respectively. Conductivity was measured with a DDS-307 conductivity meter with a DJS-1C electrode. Glass transition and decomposition
temperatures were measured with a DSC 2910 and TGA 2050 meters,
ACHTUNGRErespectively.
Supported absorption of CO2 : Experiments were performed by using
ultra pure CO2 (purity of 99.995 %) purchased from the Beijing Analytical Instrument Factory. Experiments were performed as in our previous
work.[18] The porous silica gel (SiO2, Qingdao Silica Gel Factory) was pretreated at 400 8C for 2 h. [aP4443]ACHTUNGRE[Gly], [aP4443]ACHTUNGRE[Ala], [aP4443]ACHTUNGRE[Val], [aP4443]ACHTUNGRE[Leu], [P4444][Ac] and [P4444][Pr] were dissolved in ethanol and then
mixed with the above silica gel. After evaporation of the ethanol at
70 8C, silica gel samples containing ILs were further dried with P2O5 in a
vacuum at 80 8C for 24 h. Then the samples were placed in a glass container. CO2 dried with P2O5 was then fed into the container through a
PTFE pipeline at atmospheric pressure. Parafilm was used to prevent the
humid atmosphere from entering the system. The amount of CO2 absorbed was determined by an Analytical Balance to an accuracy of
0.0001 g at certain intervals of time.
Figure 7. Recycling of [aP4443]ACHTUNGRE[Gly] in the chemical absorption of CO2.
chemical properties, including density, viscosity, glass transition and thermal decomposition temperatures, and conductivity were determined. It was found that the [aP4443][AA]
ILs have excellent thermal properties, such as low glass transition temperatures that range from 69.7 to 29.6 8C and
thermal decomposition temperatures all above 200 8C. Supported by porous SiO2, the CO2 absorption by [aP4443]ACHTUNGRE[Gly],
[aP4443]ACHTUNGRE[Ala], [aP4443]ACHTUNGRE[Val] and [aP4443]ACHTUNGRE[Leu] almost reaches
equilibrium within 80 min. The chemical absorption of CO2
by [aP4443]ACHTUNGRE[Gly] and [aP4443]ACHTUNGRE[Ala] was found to approach
1 mol CO2 per mol IL, which is a factor of two greater than
that reported before. The [aP4443][AA] ILs can be repeatedly
recycled for CO2 uptake. For [aP4443]ACHTUNGRE[Gly], the loss of absorption rate and capacity is not very significant for five absorption cycles.
3008
www.chemeurj.org
Synthesis of (3-aminopropyl)tributylphosphonium bromide hydrobromide
([aP4443][Br]·HBr): A mixture of tri-n-butylphosphine (313.6 g, 1.55 mol)
and 3-bromopropylamine hydrobromide (328.4 g, 1.5 mol) in acetonitrile
(500 mL) was heated with stirring at 80 8C for 48 h. On completion, acetonitrile was evaporated under reduced pressure at 80 8C and the residue
was dried under vacuum at 80 8C for 24 h. The product was washed with
hexane under reflux for 1 h. After the mixture had cooled, the upper
hexane phase was separated. The washing step was repeated until distillation of the separated hexane showed that no more tributylphosphine remained. The product was dried at 80 8C for 24 h to yield a white solid
[aP4443][Br]·HBr (600.2 g, 1.43 mol).
Synthesis of (3-aminopropyl)tributylphosphonium hydroxide ([aP4443]
[OH]): The anion resin was transformed from Cl-type into OH-type by
passing NaOH solution (2 mol L 1, 10 mL min 1) through columns of
resin (L = 100 cm, r = 2.5 cm) until Cl could not be detected with
AgNO3/HNO3 solution (0.5 mol L 1). As the anion-exchange resin (OH )
is not stable at temperatures higher than 40 8C, NaOH solution must be
used after it is cooled. Excessive NaOH solution was washed with deionised water. [aP4443][Br]·HBr was diluted with a little water and then transformed into [aP4443][OH] solution by passing it through the resin columns.
The [aP4443][OH] solution was concentrated by rotation evaporation
under reduced pressure at 50 8C (pure (3-aminopropyl)tributylphosphonium hydroxide is not stable).
Synthesis of (3-aminopropyl)tributylphosphonium amino acid ILs [aP4443]
[AA]: The [aP4443][OH] solution obtained was divided into 20 portions,
which were neutralised with equimolar quantities of 20 natural amino
acids, respectively. The solutions obtained were evaporated under reduced pressure at 80 8C and then dried with P2O5 under vacuum at 80 8C
for 48 h.
2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 3003 – 3011
Amino-Functionalised Phosphonium Ionic Liquids
(3-Aminopropyl)tributylphosphonium bromide hydrobromide ([aP4443]
[Br]·HBr): 1H NMR (400 MHz, D2O, 25 8C, relative to TMS): d = 0.96 (t,
J = 14.4 Hz, 9 H; CH3), 1.47–1.63 (m, 12 H; CH2), 2.02 (m, 2 H; CH2),
2.25–2.39 (m, 8 H; PCH2), 3.17 ppm (t, J = 14.9 Hz, 2 H; CH2NH2HBr);
1
H NMR (400 MHz, DMSO, 25 8C, relative to TMS): d = 0.93 (t, J =
14.3 Hz, 9 H; CH3), 1.39–1.51 (m, 12 H; CH2), 1.79 (m, 2 H; CH2), 2.25 (t,
J = 22.5 Hz, 6 H; PCH2), 2.51 (t, J = 22.2 Hz, 2 H; PCH2), 2.93 (m, 2 H;
CH2NH2HBr), 7.98 ppm (s, 3 H; NH2HBr); 13C NMR (400 MHz, DMSO,
25 8C, TMS): d = 13.4, 15.6, 17.7, 19.3, 22.8, 23.5, 39.3 ppm; elemental
analysis calcd (%) for C15H36Br2NP (421.2): C 42.8, H 8.6, N 3.3; found:
C 42.6, H 8.7, N 3.3.
(3-Aminopropyl)tributylphosphonium l-a-aminopropionic acid salt
([aP4443]ACHTUNGRE[Ala]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.93 (t, J =
14.2 Hz, 9 H; CH3), 1.20 (d, J = 7.0 Hz, 3 H; CH3), 1.43–1.55 (m, 12 H;
CH2), 1.67 (m, 2 H; CH2), 2.14–2.21 (m, 8 H; PCH2), 2.69 (t, J = 13.5 Hz,
2 H; CH2NH2), 3.25 ppm (q, J = 20.7 Hz, 1 H; HCACHTUNGRE(NH2)COO ); 1H NMR
(400 MHz, DMSO, 25 8C, TMS): d = 0.92 (t, J = 14.2 Hz, 9 H; CH3), 1.00
(d, J = 6.8 Hz, 3 H; CH3), 1.40–1.51 (m, 18 H; CH2 and NH2), 2.21–2.29
(m, 8 H; PCH2), 2.60 (t, J = 13.6 Hz, 2 H; CH2), 2.80 ppm (q, J = 20.5 Hz,
1 H; HCACHTUNGRE(NH2)COO ); 13C NMR(400 MHz, D2O, 25 8C, TMS): d = 12.6,
15.6, 17.4, 20.3, 22.5, 23.1, 23.6, 41.1, 57.1, 183.5 ppm; IR (KBr): ñ = 3354,
3280, 3180, 2958, 2931, 2872, 1576, 1463, 1408, 1358, 1313, 1232, 1098,
1005, 968, 907, 833, 776, 721, 532 cm 1; elemental analysis calcd (%) for
C18H41N2O2P (348.5): C 62.0, H 11.9, N 8.0; found: C 61.8, H 12.0, N 7.9.
(3-Aminopropyl)tributylphosphonium l-a-amino-5- guanidinovaleric acid
salt ([aP4443]ACHTUNGRE[Arg]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.89 (t,
J = 13.9 Hz, 9 H; CH3), 1.40–1.54 (m, 16 H; CH2), 1.78–1.82 (m, 3 H),
2.12–2.16 (m, 8 H; PCH2), 2.58 (m, 1 H), 2.68 (t, J = 13.7, 2 H; CH2NH2),
3.20 ppm (t, J = 12.6 Hz, 1 H; HCACHTUNGRE(NH2)COO ); 13C NMR (400 MHz,
D2O, 25 8C, TMS): d = 12.3, 15.5, 17.3, 22.4, 23.0, 23.5, 25.4, 31.8, 40.3,
41.0, 55.6, 156.8, 183.2 ppm; IR (KBr): ñ = 3351, 3282, 3188, 2958, 2932,
2872, 2140, 1668, 1584, 1465, 1382, 1313, 1229, 1159, 1096, 1049, 1003,
903, 818, 752, 724, 625, 481 cm 1; elemental analysis calcd (%) for
C21H48N5O2P (433.6): C 58.2, H 11.2, N 16.2; found: C 58.0, H 11.4, N
16.0.
(3-Aminopropyl)tributylphosphonium l-a-aminosuccinamic acid salt
([aP4443]ACHTUNGRE[Asn]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.90 (t, J =
14.3 Hz, 9 H; CH3), 1.41–1.56 (m, 12 H; CH2), 1.67 (m, 2 H; CH2), 2.12–
2.20 (m, 8 H; PCH2), 2.38 (m, 1 H), 2.64–2.70 (m, 3 H), 3.55 ppm (m, 1 H;
HCACHTUNGRE(NH2)COO ); 13C NMR (400 MHz, D2O, 25 8C, TMS): d = 12.3, 15.4,
17.3, 22.4, 23.0, 23.5, 40.2, 40.9, 53.0, 176.4, 181.0 ppm; IR (KBr): ñ =
3350, 3284, 3185, 2958, 2931, 2872, 1669, 1591, 1465, 1379, 1317, 1232,
1205, 1099, 1051, 1000, 968, 909, 856, 821, 721, 605, 458 cm 1; elemental
analysis calcd (%) for C19H42N3O3P (391.5): C 58.3, H 10.8, N 10.7;
found: C 58.0, H 10.9, N 10.6.
(3-Aminopropyl)tributylphosphonium l-a-aminosuccinic acid salt
([aP4443]ACHTUNGRE[Asp]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.89 (t, J =
14.4 Hz, 9 H; CH3), 1.40–1.53 (m, 12 H; CH2), 1.67 (m, 2 H; CH2), 2.11–
2.30 (m, 9 H), 2.59–2.70 (m, 3 H), 3.53 ppm (t, J = 13.3 Hz, 1 H; HCACHTUNGRE(NH2)COO ); 13C NMR (400 MHz, D2O, 25 8C, TMS): d = 12.3, 15.4,
17.3, 22.4, 23.0, 23.3, 40.8, 42.3, 53.5, 179.4, 180.8 ppm; IR (KBr): ñ =
3353, 3277, 3208, 2958, 2932, 2872, 1576, 1465, 1378, 1316, 1233, 1160,
1099, 1052, 1002, 967, 905, 819, 721, 669, 656 cm 1; elemental analysis
calcd (%) for C19H41N2O4P (392.5): C 58.1, H 10.5, N 7.1; found: C 57.9,
H 10.7, N 7.1.
(3-Aminopropyl)tributylphosphonium l-a-amino-3-mercaptopropropionic acid salt ([aP4443]ACHTUNGRE[Cys]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d =
0.89 (t, J = 14.4 Hz, 9 H; CH3), 1.40–1.55 (t, 12 H; CH2), 1.68 (m, 2 H;
CH2), 2.12–2.19 (m, 8 H; PCH2), 2.73 (t, J = 13.8 Hz, 2 H; CH2NH2), 2.87
(m, 1 H), 3.09 (m, 1 H), 3.55 ppm (t, J = 12.6 Hz, 1 H; HCACHTUNGRE(NH2)COO );
13
C NMR (400 MHz, D2O, 25 8C, TMS): d = 12.3, 15.5, 17.3, 22.4, 22.7,
23.1, 28.6, 40.8, 54.6, 180.0 ppm; IRACHTUNGRE(KBr): ñ = 3355, 3280, 3191, 2959,
2931, 2872, 1606, 1465, 1405, 1377, 1345, 1227, 1204, 1099, 1046, 1005,
968, 906, 820, 722, 626, 584, 507 cm 1; elemental analysis calcd (%) for
C18H41N2O2PS (380.6): C 56.8, H 10.9, N 7.4; found: C 56.5, H 11.1, N
7.2.
(3-Aminopropyl)tributylphosphonium l-a-aminoglutaramic acid salt
([aP4443]ACHTUNGRE[Gln]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.90 (t, J =
Chem. Eur. J. 2009, 15, 3003 – 3011
FULL PAPER
14.4 Hz, 9 H; CH3), 1.41–1.56 (m, 12 H; CH2), 1.68 (m, 2 H; CH2), 2.01
(m, 1 H), 2.12–2.20 (m, 8 H; PCH2), 2.38 (m, 2 H; CH2), 2.47 (m, 1 H),
2.71 (t, J = 13.7 Hz, 2 H; CH2NH2), 4.14 ppm (m, 1 H; HCACHTUNGRE(NH2)COO );
13
C NMR (400 MHz, D2O, 25 8C, TMS): d = 12.3, 15.5, 17.3, 22.4, 22.9,
23.0, 25.1, 29.4, 40.8, 58.1, 180.0, 181.3 ppm; IR (KBr): ñ = 3357, 3281,
3190, 2959, 2932, 2873, 1684, 1597, 1465, 1394, 1287, 1238, 1148, 1099,
1003, 968, 909, 802, 716, 669, 493 cm 1; elemental analysis calcd (%) for
C20H44N3O3P (405.6): C 59.2, H 10.9, N 10.4; found: C 59.1, H 11.1, N
10.3.
(3-Aminopropyl)tributylphosphonium l-1-aminopropane-1,3-dicarboxylic
acid salt ([aP4443]ACHTUNGRE[Glu]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.90
(t, J = 14.4 Hz, 9 H; CH3), 1.41–1.56 (m, 12 H; CH2), 1.67 (m, 2 H; CH2),
1.77 (m, 1 H), 1.88 (m, 1 H), 2.12–2.20 (m, 8 H; PCH2), 2.70 (t, J = 13.7,
2 H; CH2NH2), 3.25 ppm (t, J = 12.5 Hz, 1 H; HCACHTUNGRE(NH2)COO ); 13C NMR
(400 MHz, D2O, 25 8C, TMS): d = 12.2, 15.5, 17.3, 22.4, 23.0, 23.4, 31.0,
33.8, 40.9, 55.4, 181.7, 182.3 ppm; IR (KBr): ñ = 3350, 3278, 3193, 2958,
2931, 2872, 1686, 1574, 1466, 1378, 1284, 1234, 1099, 1051, 1004, 968, 909,
863, 821, 722, 643 cm 1; elemental analysis calcd (%) for C20H43N2O4P
(406.5): C 59.1, H 10.7, N 6.9; found: C 59.1, H 10.9, N 6.8.
(3-Aminopropyl)tributylphosphonium aminoethanoic acid salt ([aP4443]CHTUNGRE[A Gly]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.90 (t, J = 14.3 Hz,
9 H; CH3), 1.41–1.56 (m, 12 H; CH2), 1.68 (m, 2 H; CH2), 2.12–2.20 (m,
8 H; PCH2), 2.70 (t, J = 13.6 Hz, 2 H; CH2NH2), 3.14 ppm (s, 2 H; H2CACHTUNGRE(NH2)COO ); 1H NMR (400 MHz, DMSO, 25 8C, TMS): d = 0.92 (t, J =
14.3 Hz, 9 H; CH3), 1.38–1.60 (m, 14 H; CH2), 2.23–2.31 (m, 12 H; PCH2
and NH2), 2.60 (t, J = 13.5 Hz, 2 H; CH2NH2), 2.71 ppm (s, 2 H, H2CACHTUNGRE(NH2)COO ); 13C NMR (400 MHz, DMSO, 25 8C, TMS): d = 13.2, 15.2,
17.4, 22.7, 23.3 24.7, 42.0, 46.1, 174.4 ppm; IR (KBr): ñ = 3353, 3280, 3196,
2958, 2931, 2872, 1591, 1465, 1381, 1325, 1234, 1164, 1099, 1001, 917, 866,
825, 724, 590, 499 cm 1; elemental analysis calcd (%) for C17H39N2O2P
(334.5): C 61.1, H 11.8, N 8.4; found: C 61.0, H 12.0, N 8.3.
l-a-amino-4-imidazolepropionic
(3-Aminopropyl)tributylphosphonium
acid salt ([aP4443]ACHTUNGRE[His]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.88
(t, J = 14.4 Hz, 9 H; CH3), 1.38–1.53 (m, 12 H; CH2), 1.70 (m, 2 H; CH2),
2.10–2.17 (m, 8 H; PCH2), 2.77 (t, J = 14.0 Hz, 2 H; CH2NH2), 2.83 (m,
1 H), 2.95 (m, 1 H), 3.54 (t, J = 12.8 Hz, 1 H; HCACHTUNGRE(NH2)COO ), 6.90 (s,
1 H), 7.62 ppm (s, 1 H); 13C NMR (400 MHz, D2O, 25 8C, TMS): d = 12.3,
15.5, 17.4, 22.4, 23.1, 23.5, 31.6, 41.0, 55.8, 135.5, 181.6 ppm; IR (KBr):
ñ = 3357, 3271, 3189, 2958, 2931, 2872, 1593, 1465, 1383, 1315, 1232, 1099,
1004, 969, 916, 818, 723, 665, 628, 488 cm 1; elemental analysis calcd (%)
for C21H43N4O2P (414.6): C 60.8, H 10.5, N 13.5; found: C 60.4, H 10.7, N
13.4.
(3-Aminopropyl)tributylphosphonium l-a-amino-3-methylvaleric acid
salt ([aP4443]ACHTUNGRE[Ile]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.83–0.92
(m, 15 H; CH3), 1.11 (m, 1 H), 1.41–1.54 (m, 13 H), 1.63–1.70 (m, 3 H),
2.12–2.19 (m, 8 H; PCH2), 2.68 (t, J = 14.2 Hz, 2 H; CH2NH2), 3.07 ppm
(d, J = 5.2 Hz, 1 H; HCACHTUNGRE(NH2)COO ); 13C NMR (400 MHz, D2O, 25 8C,
TMS): d = 10.8, 12.3, 15.2, 15.5, 17.3, 22.4, 23.0, 23.4, 23.8, 38.2, 40.9, 60.7,
182.4 ppm; IR (KBr): ñ = 3354, 3285, 3192, 2958, 2931, 2872, 1582, 1464,
1384, 1326, 1232, 1157, 1099, 1004, 968, 908, 866, 813, 752, 721, 482 cm 1;
elemental analysis calcd (%) for C21H47N2O2P (390.6): C 64.6, H 12.1, N
7.2; found: C 64.6, H 12.0, N 7.1.
(3-Aminopropyl)tributylphosphonium l-a-amino-4-methylvaleric acid
salt ([aP4443]ACHTUNGRE[Leu]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.87–0.92
(m, 15 H; CH3), 1.41–1.54 (m, 14 H), 1.64–1.70 (m, 3 H), 2.12–2.18 (m,
8 H; PCH2), 2.68 (t, J = 13.8 Hz, 2 H; CH2NH2), 3.23 ppm (t, J = 12.5 Hz,
1 H; HCACHTUNGRE(NH2)COO ); 13C NMR (400 MHz, D2O, 25 8C, TMS): d = 12.3,
15.5, 17.3, 21.1, 22.2, 22.4, 23.0, 23.5, 24.1, 40.9, 43.8, 54.3, 183.8 ppm; IR
(KBr): ñ = 3352, 3280, 3196, 2956, 2931, 2871, 1580, 1466, 1381, 1343,
1314, 1232, 1168, 1099, 1003, 968, 901, 825, 752, 722, 548 cm 1; elemental
analysis calcd (%) for C21H47N2O2P (390.6): C 64.6, H 12.1, N 7.2; found:
C 64.7, H 12.3, N 7.1.
(3-Aminopropyl)tributylphosphonium l-a-diaminocaproic acid salt
([aP4443]ACHTUNGRE[Lys]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.91 (t, J =
14.4 Hz, 9 H; CH3), 13.2 (m, 2 H; CH2), 1.42–1.73 (m, 18 H; CH2), 2.13–
2.20 (m, 8 H; PCH2), 2.60 (t, J = 13.8 Hz, 2 H; CH2NH2), 2.69 (t, J =
13.9 Hz, 2 H; CH2NH2), 3.21 ppm (t, J = 12.7 Hz, 1 H; HCACHTUNGRE(NH2)COO );
13
C NMR (400 MHz, D2O, 25 8C, TMS): d = 12.3, 15.2, 17.3, 22.1, 22.4,
2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3009
S. Zhang et al.
23.0, 23.5, 31.1, 34.1, 40.0, 40.9, 55.7, 183.3 ppm; IR (KBr): ñ = 3351, 3276,
3193, 2957, 2930, 2871, 1577, 1464, 1403, 1352, 1322, 1232, 1207, 1099,
1002, 968, 905, 828, 722, 548 cm 1; elemental analysis calcd (%) for
C21H48N3O2P (405.6): C 62.2, H 11.9, N 10.4; found: C 62.0, H 11.9, N
10.3.
(3-Aminopropyl)tributylphosphonium l-a-amino-g-(methylthio)butyric
acid salt ([aP4443]ACHTUNGRE[Met]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.92
(t, J = 14.4 Hz, 9 H; CH3), 1.42–1.55 (m, 12 H; CH2), 1.69 (m, 2 H; CH2),
1.80 (m, 1 H), 1.92 (m, 1 H), 2.10 (s, 3 H; SCH3), 2.14–2.21 (m, 8 H;
PCH2), 2.54 (t, J = 13.8 Hz, 2 H; CH2S), 2.71 (t, J = 13.7 Hz, 2 H;
CH2NH2), 3.31 ppm (t, J = 12.8 Hz, 1 H; HCACHTUNGRE(NH2)COO ); 13C NMR
(400 MHz, D2O, 25 8C, TMS): d = 12.3, 13.8, 15.5, 17.3, 22.4, 23.0, 23.4,
29.4, 33.8, 40.9, 55.0, 182.3 ppm; IR (KBr): ñ = 3352, 3280, 3198, 2958,
2930, 2872, 1588, 1465, 1443, 1383, 1321, 1231, 1099, 1004, 967, 909, 857,
820, 723, 543 cm 1; elemental analysis calcd (%) for C20H45N2O2PS
(408.6): C 58.8, H 11.1, N 6.9; found: C 58.5, H 11.2, N 6.8.
(3-Aminopropyl)tributylphosphonium l-a-aminohydrocinnamic acid salt
([aP4443]ACHTUNGRE[Phe]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.91, (t, J =
14.3 Hz, 9 H; CH3), 1.40–1.53 (m, 12 H; CH2), 1.65 (m, 2 H; CH2), 2.08–
2.15 (m, 8 H; PCH2), 2.68 (t, J = 13.8 Hz, 2 H; CH2NH2), 2.85 (m, 1 H),
2.98 (m, 1 H), 3.48 (t, J = 12.9 Hz, 1 H; HCACHTUNGRE(NH2)COO ), 7.25–7.30 (m,
3 H), 7.33–7.38 ppm (m, 2 H); 13C NMR (400 MHz, D2O, 25 8C, TMS): d =
12.3, 15.4, 17.3, 22.4, 23.0, 23.3, 40.3, 40.9, 57.1, 126.4, 128.3, 129.2, 137.8,
181.6 ppm; IR (KBr): ñ = 3362, 3281, 3190, 3082, 3060, 3024, 2958, 2930,
2872, 1592, 1549, 1495, 1453, 1382, 1345, 1231, 1098, 1004, 968, 893, 834,
745, 701, 572, 486 cm 1; elemental analysis calcd (%) for C24H45N2O2P
(424.6): C 67.9, H 10.7, N 6.6; found: C 67.6, H 10.8, N 6.6.
(3-Aminopropyl)tributylphosphonium (S)-2-pyrrolidinecarboxylic acid
salt ([aP4443]ACHTUNGRE[Pro]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.91 (t,
J = 14.3 Hz, 9 H; CH3), 1.41–1.54 (m, 12 H; CH2), 1.64–1.74 (m, 5 H),
2.08–2.20 (m, 9 H), 2.69–2.76 (m, 3 H), 3.02 (m, 1 H), 3.46 ppm (t, J =
13.8 Hz, 1 H; HC(NH)COO ); 13C NMR (400 MHz, D2O, 25 8C, TMS):
d = 12.3, 15.4, 17.3, 22.4, 23.0, 23.5, 24.8, 30.4, 40.9, 45.7, 61.2, 181.5 ppm;
IR (KBr): ñ = 3358, 3290, 3189, 2958, 2933, 2872, 1576, 1464, 1401, 1310,
1232, 1099, 1004, 968, 909, 821, 786, 721, 453 cm 1; elemental analysis
calcd (%) for C20H43N2O2P (374.5): C 64.1, H 11.6, N 7.5; found: C 63.9,
H 11.8, N 7.3.
(3-Aminopropyl)tributylphosphonium
l-a-amino-3-hydroxypropionic
acid salt ([aP4443]ACHTUNGRE[Ser]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.90
(t, J = 14.4 Hz, 9 H; CH3), 1.41–1.54 (m, 12 H; CH2), 1.66 (m, 2 H; CH2),
2.12–2.20 (m, 8 H; PCH2), 2.69 (t, J = 13.8 Hz, 2 H; CH2NH2), 3.30 (t, J =
10.2 Hz, 1 H; HCACHTUNGRE(NH2)COO ), 3.64–3.73 ppm (m, 2 H; CH2OH);
13
C NMR (400 MHz, D2O, 25 8C, TMS): d = 12.3, 15.4, 17.3, 22.4, 23.0,
23.4, 40.9, 57.2, 64.3, 180.0 ppm; IR (KBr): ñ = 3354, 3280, 3201, 2958,
2932, 2872, 1595, 1465, 1385, 1330, 1230, 1204, 1099, 1043, 968, 908, 843,
767, 722, 562 cm 1; elemental analysis calcd (%) for C18H41N2O2P (364.5):
C 59.3, H 11.3, N 7.7; found: C 59.3, H 11.5, N 7.6.
(3-Aminopropyl)tributylphosphonium l-a-amino-3-hydroxybutyric acid
salt ([aP4443]ACHTUNGRE[Thr]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.90 (t,
J = 14.5 Hz, 9 H; CH3), 1.17 (d, J = 6.4 Hz, 3 H; CH3), 1.41–1.54 (m, 12 H;
CH2), 1.67 (m, J = 38.9 Hz, 2 H; CH2), 2.12–2.20 (m, 8 H; PCH2), 2.68 (t,
J = 13.7 Hz, 2 H; CH2NH2), 3.05 (d, J = 5.1 Hz, 1 H; HCACHTUNGRE(NH2)COO ),
3.90 ppm (m, 1 H; HCACHTUNGRE(CH3)OH); 13C NMR (400 MHz, D2O, 25 8C,
TMS): d = 12.3, 15.5, 17.3, 18.9, 22.4, 23.0, 23.5, 40.9, 61.6, 69.3,
180.4 ppm; IR (KBr): ñ = 3356, 3283, 3196, 2960, 2931, 2873, 1596, 1466,
1384, 1334, 1241, 1099, 1076, 1005, 966, 909, 874, 819, 723, 571 cm 1; elemental analysis calcd (%) for C19H43N2O3P (378.5): C 60.3, H 11.5, N 7.4;
found: C 60.5, H 11.6, N 7.3.
(3-Aminopropyl)tributylphosphonium (S)-a-amino-1H-indole-3-propanoic acid salt ([aP4443]ACHTUNGRE[Trp]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d =
0.92 (t, J = 12.7 Hz, 9 H; CH3), 1.40–1.54 (m, 14 H; CH2), 1.91–2.00 (m,
8 H; PCH2), 3.03 (m, 1 H), 3.20 (m, 1 H), 3.58 (t, J = 12.4 Hz, 1 H; HCACHTUNGRE(NH2)COO ), 7.13–7.23 (m, 3 H), 7.49 (d, J = 8.1 Hz, 1 H), 7.73 ppm (d,
J = 7.7 Hz, 1 H); 13C NMR (400 MHz, D2O, 25 8C, TMS): d = 12.3, 15.3,
17.1, 22.3, 23.0, 23.3, 29.9, 40.8, 56.2, 110.2, 111.5, 118.5, 118.8, 121.5,
124.0, 127.0, 135.9, 181.7 ppm; IR (KBr): ñ = 3353, 3278, 3156, 3099, 3054,
2960, 2929, 2872, 2749, 1592, 1457, 1393, 1342, 1232, 1099, 1052, 1008,
3010
www.chemeurj.org
907, 807, 743, 576, 464 cm 1; elemental analysis calcd (%) for
C26H46N3O2P (463.6): C 67.4, H 10.0, N 9.1; found: C 67.1, H 10.2, N 8.9.
(3-Aminopropyl)tributylphosphonium
l-a-amino-p-hydroxyhydrocinACHTUNGREnamic acid salt ([aP4443]ACHTUNGRE[Tyr]): 1H NMR (400 MHz, D2O, 25 8C, TMS):
d = 0.90 (t, J = 14.3 Hz, 9 H; CH3), 1.40–1.52 (t, 12 H; CH2), 1.66 (m, 2 H;
CH2), 2.09–2.16 (m, 8 H; PCH2), 2.68–2.73 (m, 3 H), 2.89 (m, 1 H), 3.45 (t,
J = 12.6 Hz, 1 H; HCACHTUNGRE(NH2)COO ), 6.66 (d, J = 8.4 Hz, 2 H), 7.03 ppm (d,
J = 8.3 Hz, 2 H); 13C NMR (400 MHz, D2O, 25 8C, TMS): d = 12.3, 15.5,
17.3, 22.4, 23.0, 23.3, 39.1, 40.9, 57.1, 117.0, 125.6, 130.4, 160.1, 181.2 ppm;
IR (KBr): ñ = 3357, 3287, 3190, 2959, 2932, 2872, 1594, 1514, 1465, 1390,
1319, 1255, 1166, 1099, 1052, 1003, 967, 906, 826, 723, 528 cm 1; elemental
analysis calcd (%) for C24H45N2O3P (440.6): C 65.4, H 10.3, N 6.4; found:
C 65.3, H 10.5, N 6.2.
(3-Aminopropyl)tributylphosphonium l-a-aminoisovaleric acid salt
([aP4443]ACHTUNGRE[Val]): 1H NMR (400 MHz, D2O, 25 8C, TMS): d = 0.86 (d, J =
6.8 Hz, 3 H; CH3), 0.92–0.96 (m, 12 H; CH3), 1.44–1.58 (m, 12 H; CH2),
1.68 (m, 2 H; CH2), 1.93 (m, 1 H), 2.15–2.22 (m, 8 H; PCH2), 2.72 (t, J =
13.6 Hz, 2 H; CH2NH2), 3.02 ppm (d, J = 5.1 Hz, 1 H; HCACHTUNGRE(NH2)COO );
1
H NMR (400 MHz, DMSO, 25 8C, TMS): d = 0.66 (d, J = 6.7 Hz, 3 H;
CH3), 0.80 (d, J = 6.9 Hz, 3 H; CH3), 0.92 (t, J = 14.2 Hz, 9 H; CH3), 1.40–
1.49 (m, 18 H), 1.87 (m, 1 H), 2.20–2.28 (m, 8 H; PCH2), 2.58–2.61 ppm
(m, 3 H); 13C NMR (400 MHz, D2O, 25 8C, TMS): d = 12.5, 15.6, 16.6,
17.4, 19.1, 22.5, 23.1, 23.5, 31.4, 41.0, 61.5, 182.2 ppm; IR (KBr): ñ = 3359,
3287, 3193, 2957, 2931, 2871, 1575, 1465, 1406, 1363, 1329, 1231, 1190,
1099, 970, 916, 880, 824, 755, 719, 482 cm 1; elemental analysis calcd (%)
for C20H45N2O2P (376.6): C 63.8, H 12.1, N 7.4; found: C 63.6, H 12.3, N
7.4.
Acknowledgements
Support of this work by the National Science Fund of China for Distinguished Young Scholars (20625618), the National Natural Science Foundation of China (No. 20873152), the Hi-tech Research and Development
Program of China (2006AA06Z371), and the National 863 Program of
China (2006AA06Z317) is gratefully acknowledged.
[1] M. George, R. G. Weiss, J. Am. Chem. Soc. 2001, 123, 10393 – 10394.
[2] S. H. Park, K. B. Lee, J. C. Hyun, S. H. Kim, Ind. Eng. Chem. Res.
2002, 41, 1658 – 1665.
[3] D. Bonenfant, M. Mimeault, R. Hausler, Ind. Eng. Chem. Res. 2003,
42, 3179 – 3184.
[4] K. A. Hoff, O. Juliussen, O. Falk-Pedersen, H. F. Svendsen, Ind.
Eng. Chem. Res. 2004, 43, 4908 – 4921.
[5] K. R. Seddon, J. Chem. Technol. Biotechnol. 1997, 68, 351 – 356.
[6] J. G. Huddleston, H. D. Willauer, R. P. Swatloski, A. E. Visser, R. D.
Rogers, Chem. Commun. 1998, 1765 – 1766.
[7] R. D. Rogers, K. R. Seddon, Science 2003, 302, 792 – 793.
[8] C. Cadena, J. L. Anthony, J. K. Shah, T. I. Morrow, J. F. Brennecke,
E. J. Maginn, J. Am. Chem. Soc. 2004, 126, 5300 – 5308.
[9] M. J. Muldoon, S. Aki, J. L. Anderson, J. K. Dixon, J. F. Brennecke,
J. Phys. Chem. B 2007, 111, 9001 – 9009.
[10] J. L. Anthony, J. L. Anderson, E. J. Maginn, J. F. Brennecke, J. Phys.
Chem. B 2005, 109, 6366 – 6374.
[11] S. Aki, B. R. Mellein, E. M. Saurer, J. F. Brennecke, J. Phys. Chem.
B 2004, 108, 20355 – 20365.
[12] S. J. Zhang, Y. H. Chen, R. X. F. Ren, Y. Q. Zhang, J. M. Zhang,
X. P. Zhan, J. Chem. Eng. Data 2005, 50, 230 – 233.
[13] Y. H. Chen, S. J. Zhang, X. L. Yuan, Y. Q. Zhang, X. P. Zhang, W. B.
Dai, R. Mori, Thermochim. Acta 2006, 441, 42 – 44.
[14] S. J. Zhang, X. L. Yuan, Y. H. Chen, X. P. Zhang, J. Chem. Eng.
Data 2005, 50, 1582 – 1585.
[15] E. D. Bates, R. D. Mayton, I. Ntai, J. H. Davis, J. Am. Chem. Soc.
2002, 124, 926 – 927.
[16] J. Kagimoto, K. Fukumoto, H. Ohno, Chem. Commun. 2006, 2254 –
2256.
2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 3003 – 3011
Amino-Functionalised Phosphonium Ionic Liquids
[17] K. Fukumoto, M. Yoshizawa, H. Ohno, J. Am. Chem. Soc. 2005,
127, 2398 – 2399.
[18] J. M. Zhang, S. J. Zhang, K. Dong, Y. Q. Zhang, Y. Q. Shen, X. M.
Lv, Chem. Eur. J. 2006, 12, 4021 – 4026.
[19] Y. Y. Jiang, G. N. Wang, Z. Zhou, Y. T. Wu, J. Geng, Z. B. Zhang,
Chem. Commun. 2008, 505 – 507.
[20] J. G. Huddleston, A. E. Visser, W. M. Reichert, H. D. Willauer,
G. A. Broker, R. D. Rogers, Green Chem. 2001, 3, 156 – 164.
[21] T. Nishida, Y. Tashiro, M. Yamamoto, J. Fluorine Chem. 2003, 120,
135 – 141.
[22] P. Bonhote, A. P. Dias, N. Papageorgiou, K. Kalyanasundaram, M.
Gratzel, Inorg. Chem. 1996, 35, 1168 – 1178.
[23] Z. Y. Gu, J. F. Brennecke, J. Chem. Eng. Data 2002, 47, 339 – 345.
[24] L. C. Branco, J. N. Rosa, J. J. M. Ramos, C. A. M. Afonso, Chem.
Eur. J. 2002, 8, 3671 – 3677.
Chem. Eur. J. 2009, 15, 3003 – 3011
FULL PAPER
[25] H. L. Ngo, K. LeCompte, L. Hargens, A. B. McEwen, Thermochim.
Acta 2000, 357-358, 97 – 102.
[26] P. A. Z. Suarez, S. Einloft, J. E. L. Dullius, R. F. de Souza, J. Dupont,
J. Chim. Phys. Phys.-Chim. Biol. 1998, 95, 1626 – 1639.
[27] J. D. Holbrey, K. R. Seddon, J. Chem. Soc. Dalton Trans. 1999,
2133 – 2139.
[28] J. Fuller, R. T. Carlin, R. A. Osteryoung, J. Electrochem. Soc. 1997,
144, 3881 – 3886.
[29] C. Nanjundiah, S. F. McDevitt, V. R. Koch, J. Electrochem. Soc.
1997, 144, 3392 – 3397.
2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Received: June 17, 2008
Revised: October 10, 2008
Published online: February 2, 2009
www.chemeurj.org
3011