Solids can transition to only one phase of plastic crystal or
LC (if they have mesophases), because only one state of orien-
tation or gravity point of the constituents is allowed to melt in
the mesophase (both states are fused in an isotropic liquid state).
It is, thus, interesting to determine which parameters contribute
to forming rotator (plastic crystal) or LC phases, especially,
in rod-like chemicals. The physical properties of n-CmH(2m+1)-
Kagaku Co.) to BEt in hexane diluent at 0 °C and evaporating
the solvents. During this process, the flask was continuously
3
flushed with N gas. For preparation of [n-C H
NEt ]Br
3
2
x
(2x+1)
(x = 48, 10, 11, 12, 14, 16), NEt and n-C H(2x+1)Br were
3
x
mixed in ethanol. The products were obtained by evaporating
the solvent at 60 °C. After dissolving [n-C H NEt ]Br
x
(2x+1)
3
in water, Li[BEt3Me] was added to the aqueous solution at
0 °C. [CxNEt ][BEt Me] (x = 4) crystallized in the solution; in
2
11
1215
16
NH Cl,
5
n-C H(2m+1)COOM
n-C H
OSO M,
(2m+1) 3
3
m
m
3
3
-alkoxy-2-(4-alkoxyphenyl)pyrimidine,4
8,49
4-[4-n-alkoxy
contrast, liquid products were obtained for x = 58, 10, 12,
14, and 16. The latter materials were separated by use of
dichloromethane and purified by vacuum drying. The chemical
5
0,51
cinnamoyloxy]-4-methoxy benzyl cinnamates,
previously been evaluated as a function of the alkyl-chain
lengths. In the case of n-C H NH Cl (x ² 7), a rotator phase
etc., have
1
13
structures of all products were confirmed by H and C NMR
x
(2x+1)
3
transforming to a LC phase with increasing temperatures is
measurements in DMSO-d solvent.
DSC spectra were obtained with a Shimadzu DSC-60 calo-
rimeter using Al2O3 as a reference sample. The samples were
6
11
observed, however, no LC phase is detected in n-C H(2m+1)-
m
COOM and n-CmH(2m+1)OSO3M salts.1
216
In contrast, the latter
¹
1
two molecular compounds of 5-alkoxy-2-(4-alkoxyphenyl)
heated from ca. 230 to 480 K at a rate of 5 K min . Based on
pyrimidine and 4-[4-n-alkoxy cinnamoyloxy]-4-methoxy ben-
the DSC results, the transition temperatures (T ) in the solid
phase were determined as well as entropy changes at these
transition temperatures.
tr
zyl cinnamates form only LC phases.4
851
This difference is
considered to indicate that attractive interactions among the
constituents influence which phase (rotator or LC) is formed.
However, the formation of both LC and plastic-crystal phases
for a chemical family is rarely observed.
For ionic plastic-crystals, we have recently proposed a new
region in which chemicals assemble via weak ionic interac-
tions, and we have successfully demonstrated the formation
Polarized optical microscope (POM) photographs of the
liquid crystal and isotropic liquid phases were obtained using
an Olympus CX31P instrument with a sensitive color plate.
XRD patterns were acquired using a Bruker D8 ADVANCE
instrument equipped with a Cu anticathode. A rotating stage
and ttk450 probe were employed at room and other temper-
atures, respectively. Powder patterns were recorded over a scan
range of 540° with a step angle of 0.02°.
of twenty-four new ionic plastic-crystals of [NEt Me(4¹x)]-
x
[
3
[
BEt Me
] and [NEt Pr
][BEt Me
] (x = 04, y = 1
(4¹z)
z
(4¹z)
y
(4¹y)
z
, z = 3, 4),52,53 [NEt Pr][BBu ] and [NEt Pr ][BBu ],
54,55
Solid-state H NMR spectra were recorded at a Larmor fre-
1
3
4
2
2
4
56
NEt Me
Pr][BEt Me] (x = 1, 2), and 1-alkyl-4-aza-1-
quency of 600.13 MHz using a Bruker Avance 600 spectrom-
x
(3¹x)
3
57
azoniabicyclo[2,2,2]octane salts in the new region. These
compounds exhibit interesting characteristics, including low
temperatures of transition to the plastic phases (similar to the
eter (14.10 T). The samples were packed in a ZrO rotor with an
2
outer diameter of 4.0 mm. Spectra were obtained by Fourier
transformation (FT) of the free-induction-decay (FID) signals
1
nature of molecular plastic-crystals) and high melting points
that were obtained after a π/2 pulse. The H chemical shifts
+
(
[
similar to ionic plastic-crystals). Since the [NEt R] and
(CS) were calibrated relative to an external H O (δ = 2.499
3
2
¹
BEt Me] ions (R = alkyl groups) can be assembled via weak
ppm) reference. A recycle time of 5 s was employed for
capturing the FID data. The sample temperature was controlled
and recorded by a Bruker VT-2000 instrument. Solid-state
3
ionic interactions and show several ionic plastic crystalline
5
2
phases, it can be expected that several salts in this chemical
family should show LC phases in a range of long alkyl-chains.
In this study, we treat [n-CxH(2x+1)NEt3][BEt3Me] (abbreviated
to [CxNEt ][BEt Me]) with x = 416 with even values of x
1
3
C NMR spectra were recorded at a Larmor frequency of
150.92 MHz by use of the same spectrometer and temperature
1
controller. The same sample tube used for the H measurements
3
3
1
3
and x = 5, 7, to explore the mechanisms determining which
mesophase (plastic crystal, rotator crystal, or LC) is formed by
the salts and to investigate the formation of new ionic liquid-
crystals in the new region.
was employed for accumulating C NMR signals. Cross-
polarization (CP) and magic-angle-spinning (MAS) methods
were applied to detect signals with glycine as an external refer-
ence (δ = 43.16 ppm). Recycle times of 5 and 20 s were respec-
1
3
In the case of [CxNEt ][BEt Me], it has been reported that
tively employed for C NMR measurements with and without
CP. In order to estimate the purity of the synthesized speci-
3
3
the salts with x = 1, 2, and 3 exhibit plastic-crystal phases at
around room temperature: the transformation temperature for
1
13
mens, H and C NMR measurements of the prepared sample
conversion to the plastic phase is 232.2 K for [C3NEt ]-
dissolved in DMSO-d were carried out in the same apparatus
3
6
[
BEt Me], 227.2 K for [C2NEt ][BEt Me], and below 200 K
(analysis of samples in the solution and solid states is possible
with this spectrometer by exchanging the probe). The chemical
shift (CS) values of the H and C nuclei were calibrated by
3
3
3
for [C1NEt ][BEt Me]. The melting point of [C3NEt ]-
3
3
3
1
13
[
[
(
BEt Me] is 391.2 K; in contrast, [C1NEt ][BEt Me] and
3
3
3
52
C2NEt ][BEt Me] decompose at around 400 K. These salts
employing tetramethylsilane (TMS) dissolved in DMSO-d as
3
3
6
x = 13) are classified into new ionic-plastic-crystal regions
an internal reference (δ = 0.00 ppm).
with weak interaction acting on cation and anion.
Density functional theory (DFT) simulation was performed
to assign the NMR peaks and to estimate the line-widths ob-
2
. Experimental
1
13
served in the H and C NMR spectra. As demonstrated in a
5
257
For the preparation of Li[BEt Me] and [NEt Me(3¹x)R]Br,
previous report,
the B3LYP/6-311+G** function in the
3
x
reported procedures52 were applied. Li[BEt Me] crystals were
Gaussian 03 computer program can be adequately used to
explain the C NMR CS values and line-widths observed for
58
3
1
3
obtained by adding MeLi dissolved in diethylether (Kanto
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