102
L. Leclercq et al. / Journal of Molecular Structure 918 (2009) 101–107
H
aro), 10.51 (s, 1H; N@CHN); 13C NMR (75 MHz, CDCl3, 25 °C): d
a
b
(ppm) = 53.2 (NCH2), 121.8 (CH@CH), 128.9 (Cm),129.3 (Co), 129.3
(Cp), 132.7 (NCHN), 136.6 (CaroCH2). Anal. Calc. for C17H17BrN2;
2H2O: C, 55.90%; H, 5.79%; N, 7.67%. Found: C, 54.84%; H, 5.77%;
N, 7.87%. ESI/HRMS m/z found: 249.1376 (MꢁBr)+, calc.:
249.1391. MP: 85 °C.
H
H
4
5
4
N5
+
N
+
2
N
N
2
X-
X-
H
2.4. Synthesis of 1,3-dibenzylimidazolium hexafluorophosphate (III)
The 1,3-dibenzylimidazolium bromide salt was dissolved in
Fig. 1. (a) The three T-stacking and H-bond donors of an imidazolium ring and their
directionality, and (b) p-stacking.
water (5 mmol Lꢁ1) and a NH4PF6 aqueous solution (5 mmol Lꢁ1
)
was added. The imidazolium hexafluorophosphate salt precipitates
(95%).
1H NMR (300 MHz, CDCl3, 25 °C, TMS): d (ppm) = 5.23 (s, 4H,
NCH2), 7.24 (m, 2H, CH@CH, 3JHAH = 1.3 Hz), 7.3–7.4 (m, 10H; Haro),
2. Experimental
9.63 (s, 1H; N@CHN); 13C NMR (75 MHz, CDCl3, 25 °C):
d
2.1. Materials
(ppm) = 53.2 (NCH2), 121.4 (CH@CH), 128.6 (Cm),129.1 (Co),
129.3 ppm (Cp), 132.5 (N@CHN), 136.2 (CaroCH2). Anal. Calc. for
C17H17F6N2P: C, 51.78%; H, 4.35%; N, 7.10%. Found: C, 51.82%; H,
5.41%; N, 7.11%. ESI/HRMS m/z found: 249.1264 (MꢁPF6)+, calc.:
249.1391. MP: 93 °C.
All reactions were carried out in oven-dried glassware under
nitrogen, using standard Schlenk and vacuum line techniques.
The 1H and 13C NMR spectra were recorded using an Advance
300 Brucker, at 300.13 and 75.49 MHz, respectively. Chemical
shifts are given in ppm (d) and measured relative to residual sol-
vent. Elemental analyses were performed by the ‘‘Université de
Montréal” facility. CDCl3 and all other chemicals were purchased
from Aldrich and used without further purification. ‘‘Distilled” sol-
vents were obtained using a GlassContour system (Irvine, CA).
2.5. Crystallization and X-ray diffraction
All the crystallizations are performed in an open flask by dissol-
ving the 1,3-dibenzylimidazolium cation (33 wt.%) in 10 mL of hot
water (for I and II) or in 10 mL of hot chloroform (for III). After a
week at room temperature, single crystals suitable for X-ray dif-
fraction were obtained. All X-ray data were collected at T = 150 K
and the structures were solved by the direct method with
ShelxS-97. All non-H atoms were refined by full-matrix least-
squares with anisotropic displacement parameters while hydrogen
atoms were placed in idealized position. Hydrogen atoms from the
water molecules were initially located from a difference Fourier
map, then their location were adjusted using restrains at idealized
distances (0.84 Å) and angles (104.5°) in the direction of the hydro-
gen bonding acceptors, either chloride (compound I) or bromide
(compound II) anions.
X-ray crystallographic data for I and III were collected from a
single crystal sample, which was mounted on a loop fiber. Data
were collected using a Bruker microstar diffractometer equipped
with a Platinum 135 CCD Detector, Helios optics and Kappa goni-
ometer. The crystal-to-detector distance was 4.0 cm, and the data
collection was carried out in 512 ꢂ 512 pixel mode. The initial unit
cell parameters were determined by a least-squares fit of the angu-
lar setting of strong reflections, collected by a 10.0° scan in 33
frames over three different parts of the reciprocal space (99 frames
total). One complete sphere of data was collected.
2.2. Synthesis of 1,3-dibenzylimidazolium chloride (I)
A dry flask (250 mL), equipped with a magnetic stir bar and a
septum-inlet for nitrogen, was charged with a solution of (chloro-
methyl) benzene (1.06 g, 8.42 mmol) in toluene (50 mL). In a
Schlenk, a solution of 1-benzylimidazole (1.60 g, 10.1 mmol) in tol-
uene (10 mL) was added to the other flask in a dropwise fashion by
cannulation at 0 °C. The reaction mixture was stirred for 20 min at
room temperature, then filtered under gravity. The solid was
washed with diethylether to remove unreacted 1-benzylimidazole.
The white solid was dried overnight at 120 °C in a vacuum. The
product was stored under dry nitrogen (90%).
1H NMR (300 MHz, CDCl3, 20 °C, TMS): d = 5.41 (s, 4H, NCH2),
7.23 (m, 6H, Haro(ortho), Haro(para) and imidazolium CH@CH), 7.34
3
(d, 2H, CH@CH, JHAH = 1.3 Hz), 7.41 (dd, 4H, Haro(meta)
,
3J
HAH = 6.3 Hz and JHAH = 6.7 Hz), 10.92 ppm (s, 1H, N@CHN); 13C
NMR (75 MHz, CDCl3, 20 °C): d = 53.0 ppm (NCH2), 122.0 ppm
(CH@CH), 128.7 ppm (Cm), 129.1 ppm (Co), 129.2 ppm (Cp),
133.0 ppm (N@CHN), 137.0 ppm (CaroCH2). Anal. Calc. for
C17H17ClN2: C, 71.70%; H, 6.02%; N, 9.84%. Found: C, 69.89%; H,
6.01%; N, 9.75%. ESI/HRMS m/z found: 249.1582 (MꢁCl)+, calc.:
249.1391. MP: 63 °C.
3
X-ray crystallographic data for II were collected from a single
crystal sample, which was mounted on a loop fiber. Data were col-
lected using a Bruker Platform diffractometer, equipped with a
Bruker SMART 4K Charged-Coupled Device (CCD) Area Detector
using the program APEX II and a Nonius FR591 rotating anode
equipped with Montel 200 optics. The crystal-to-detector distance
was 5.0 cm, and the data collection was carried out in 512 ꢂ 512
pixel mode. The initial unit cell parameters were determined by
the same procedure (see above). One complete sphere of data
was collected, to better than 0.80 Å resolution.
2.3. Synthesis of 1,3-dibenzylimidazolium bromide (II)
The procedure is identical to the one which presented above.
1H NMR (300 MHz, CDCl3, 25 °C, TMS): d (ppm) = 5.52 (s, 4H,
3
NCH2), 7.23 (d, 2H, CH@CH, JHAH = 1.4 Hz), 7.31–7.39 (m, 10H;
A-
In each case, the refinement was on F2 using all reflections. The
weighted R-factor (wR) and goodness-of-fit S are based on F2, con-
ventional R-factors (R) are based on F, with F set to zero for nega-
Cl-
+
N1
A-
I
N3
C
x6
C
Br-
x13
II
tive F2. The threshold expression of F2 > 2 (F2) is used only for
r
-
PF6
III
calculating R-factors (gt) etc. and is not relevant to the choice of re-
flections for refinement. All esds (except the eds in the dihedral an-
gle between two l.s. planes) are estimated using the full covariance
matrix.
Fig. 2. The three crystals studied in this work (for I and II (x = 0), for III cation 1
(x = 1) and for III cation 2 (x = 2)).