oalkane.[21, 24] For all ILs of the type CnmimBr/Cl (n=2, 3, 4), but not for
C6mimBr and C6mimCl, a white crystalline powder was obtained.
well as in toys, signs, and so on.[20] However, all but one of
the reported compounds were solid at room temperature
and unfortunately lost their luminescent properties on
reaching temperatures at which solid–solid phase transitions
or melting occurred.
C2mimCl was synthesized by adding a fourfold excess of cold chloro-
ethane to dry N-methylimidazole in a Teflon cartridge (Parr Instruments
Co., Illinois, USA). The filled Teflon cartridge was inserted into an auto-
clave (Parr Instruments Co., Illinois, USA) and the contents were stirred
at 908C for four days. The reaction mixture was then allowed to cool to
room temperature and the excess chloroethane was evaporated. The very
hygroscopic white powder obtained was dried at 958C under reduced
pressure for several days.
C2mimCl: 1H NMR (300 MHz, D2O): d=1.46 (t, 3H), 3.87 (s, 3H), 4.21
(q, 2H), 7.45 (d, 2H), 8.72 ppm (s, 1H).
C3mimCl: 1H NMR (300 MHz, D2O): d=0.85 (t, 3H), 1.81 (q, 2H), 3.83
Recently, we were able to show that low-melting com-
pounds composed of an organic cation and an optically
active rare-earth ion, for example [C4mpyr]2[Pr
(mpyr=N-methyl-N-propylpyrrolidinium);[21] [C3mim][Eu-
(Tf2N)4], [C4mim][Eu(Tf2N)5], and [C4mpyr][Eu
(Tf2N)5];[22]
and [C4mim]3ꢀx[Dy(SCN)8ꢀxA
(H2O)x],[23] exhibit excellent lu-
ACHTUGNRTNE(NUNG Tf2N)5]
A
R
ACHTUNGTRENNUNG
A
CHTUNGTRENNUNG
minescent properties. For these systems, unexpectedly good
luminescent properties can even be maintained in the
molten/liquid state due to the favourable coordination envi-
ronment of the lanthanide ion. Furthermore, replacement of
conventional solvents by carefully designed ionic liquids can
generally lead to dramatic increases in the emission decay
of the excited state and the quantum yields of emission,
even for NIR luminescence.[24,25]
(s, 3H), 4.09 (t, 2H), 7.39 (d, 2H), 8.66 ppm (s, 1H).
1
C4mimCl: H NMR (300 MHz, D2O): d=0.82 (t, 3H), 1.18 (m, 2H), 1.72
(quint., 2H), 3.76 (s, 3H), 4.01 (t, 2H), 7.30 (d, 2H), 8.57 ppm (s, 1H).
1
C6mimCl: H NMR (300 MHz, D2O): d=0.78 (t, 3H), 1.22 (m, 6H), 1.80
(t, 2H), 3.83 (s, 3H), 4.13 (t, 2H), 7.40 (d, 2H), 8.67 ppm (s, 1H).
C2mimBr: 1H NMR (300 MHz, CDCl3): d=1.23 (t, 3H), 3.75 (s, 3H),
4.06 (q, 2H), 7.39 (s, 2H), 9.82 ppm (s, 1H).
1
C3mimBr: H NMR (300 MHz, CDCl3): d=0.44 (t, 3H), 1.45 (sext., 2H),
3.61 (s, 3H), 3.82 (t, 2H), 7.82 (d, 2H), 9.67 ppm (s, 1H).
In continuation of our research, we have sought ionic
liquid transition metal systems with interesting luminescent
properties in the (ionic) liquid state.
1
C4mimBr: H NMR (300 MHz, CDCl3): d=0.85 (t, 3H), 1.27 (sext., 2H),
1.81 (quint., 2H), 4.02 (s, 3H), 4.24 (t, 2H), 7.56 (d, 2H), 10.19 ppm (s,
1H).
C6mimBr: 1H NMR (300 MHz, CDCl3): d=0.75 (t, 3H), 1.20 (m, 6H),
1.81 (quint., 2H), 2.05 (s, 2H), 4.03 (s, 3H), 4.22 (t, 2H), 7.55 (d, 2H),
10.24 ppm (s, 1H).
General procedure for the synthesis of 1-n-alkyl-3-methylimidazolium
bis(trifluoromethanesulfonyl)amides: The 1-n-alkyl-3-methylimidazolium
bis(trifluoromethanesulfonyl)amides were synthesized by metathesis re-
actions of the 1-n-alkyl-3-methylimidazolium halides with lithium bis(tri-
fluoromethanesulfonyl)amide.[19,21,24]
Experimental Section
Materials: The following chemicals were used as received unless men-
tioned otherwise. Acetonitrile (>99.5%), dichloromethane (99.6%), tol-
uene (99.5%), manganese(II) carbonate, manganese(II) bromide (98%),
1-bromobutane (>99%), 1-chlorohexane (99%), and lithium bis(trifluor-
omethylsulfonyl)amide (>99%) were purchased from Sigma–Aldrich
(Steinheim, Germany). Ethyl acetate (99.8%) was obtained from KMF
(St. Augustin, Germany). 2-Propanol (extra dry), methanol (extra dry),
bromoethane (98%), 1-bromopropane (98%), 1-chlorobutane (>99%),
1-chloropropane (99%), and 1-bromohexane (>98%) were purchased
from Acros (Geel, Belgium). N-Methylimidazole (>99%) was purchased
from Acros (Geel, Belgium), dried over elemental sodium, and distilled
prior to use. Chloroethane (for synthesis) was purchased from Merck
(Hohenbrunn, Germany).
[Tf2N]: 1H NMR (300 MHz, CDCl3): d=1.58 (t, 3H), 4.06 (q,
ACHUTNRGEN[NUG C2mim]ACHTUTGNRENNUGN
2H), 7.73 (d, 2H), 9.00 ppm (s, 1H); 19F NMR (300 MHz, CDCl3): d=
ꢀ79.96 ppm (s, 6H).
1
G
G
2H), 3.84 (s, 3H), 4.05 (t, 2H), 7.29 (d, 2H), 8.53 ppm (s, 1H); 19F NMR
(300 MHz, CDCl3): d=ꢀ79.43 ppm (s, 6H).
1
G
N
2H), 1.80 (quint., 2H), 3.87 (s, 3H), 4.11 (t, 2H), 7.30 (d, 2H), 8.59 ppm
(s, 1H); 19F NMR (300 MHz, CDCl3): d=ꢀ79.32 ppm (s, 6H).
[Tf2N]: 1H NMR (300 MHz, CDCl3): d=0.83 (t, 3H), 1.26 (m,
ACHUTNRGEN[NUG C6mim]ACHTUTGNRENNUGN
6H), 1.81 (quint., 2H), 3.87 (s, 3H), 4.11 (t, 2H), 7.30 (d, 2H), 8.61 ppm
Syntheses
(s, 1H); 19F NMR (300 MHz, CDCl3): d=ꢀ79.27 ppm (s, 6H).
HTf2N: HTf2N was obtained by sublimation from a solution of LiTf2N in
excess sulfuric acid. The reaction mixture was stirred for 2 days at 80–
1008C. The colorless product crystallized upon cooling the vapour in
yields of about 90%. 1H NMR (300 MHz, D2O): d=4.77 ppm (s, 1H);
General procedure for the synthesis of bis(1-alkyl-3-methylimidazolium)
tetrahalogenomanganates: According to 2 RmimX + MnX2 ! [Rmim]2-
AHCTUNGRTEG[NNNU MnX4] (R=alkyl; X=Cl, Br), equimolar amounts of the appropriate
19F NMR (300 MHz, D2O): d=ꢀ79.16 ppm (s, 6F); 13C
(300 MHz, D2O): d=19.27 ppm (s, 2C).
{19F} NMR
ACHTUNGTRENNUNG
dry 1-alkyl-3-methylimidazolium halide and MnX2 were placed in a
Schlenk tube and heated to 808C. After completion of the reaction,
which could be monitored visually by the complete dissolution of MnX2,
the product was kept at 908C under reduced pressure for one day. In all
cases, the yield of the yellow-green to brownish ionic liquid was quantita-
tive. Each liquid product was washed several times with 2-propanol to
remove unreacted starting materials. Alternatively, the reaction could be
performed in anhydrous methanol or 2-propanol, with subsequent crys-
tallization of the products after removal of the solvent. The halide com-
pounds were purified by washing several times with 2-propanol and re-
peatedly recrystallizing from 1:0.5!1:1 methanol/2-propanol mixtures.
MnACHTUNGTRENNUNG(Tf2N)2: Manganese(II) carbonate was suspended in water and an
equimolar amount of HTf2N dissolved in water was added dropwise. The
reaction mixture was stirred at 60–808C for 2 h. The water was then
evaporated and the product was dried at 1408C under reduced pressure
for 1 day. The crude product was resublimed at 3008C. Elemental analy-
sis calcd (%): C 7.80, H 0.00, N 4.55, S 20.81; found: C 7.78, H 0.10, N
4.64, S 21.40.
MnCl2: Manganese(II) carbonate was suspended in water, an excess of
hydrochloric acid was added, and the mixture was stirred at 1208C until
a pink solid precipitated as a slurry. The crude product was dried at
3008C under reduced pressure for two days to give pink MnCl2. The
purity of the obtained product was confirmed by powder XRD analysis.
A
2ACHTUNGTREN[NUNG MnCl4]: Elemental analysis calcd (%): C 34.39, H 5.29, N
A
CHTUNGTRENNUNG
General procedure for the synthesis of 1-n-alkyl-3-methylimidazolium
chlorides and bromides: Generally, the chloride and bromide ILs were
synthesized by alkylation of N-methylimidazole with the appropriate hal-
N
CHTUNGTRENNUNG
3356
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 3355 – 3365