Effective Na+-Binding Ability and Molecular Assembly of an Alkylamide-Substituted Penta(ethylene)glycol Derivative

Alkylamide-Substituted Penta(ethylene)glycol Derivative

Article

Eﬀective Na ‑Binding Ability and Molecular Assembly of an

Shinya Seto, Takashi Takeda, Norihisa Hoshino, and Tomoyuki Akutagawa*

Cite This: J. Phys. Chem. B 2021, 125, 6349 −6358

Read Online

ACCESS

Metrics & More

Article Recommendations

sı Supporting Information

ABSTRACT: A new amphiphilic penta(ethylene glycol) deriva-

tive (1) bearing two hydrogen-bonding −CONHC H chains

was prepared. Compound 1 exhibited ion-recognition abilities for

Na and K , and its properties were compared with those of the

macrocyclic [18]crown-6. Although both compound 1 and

[

18]crown-6 have six ether oxygen atoms (−OC H −), the Na -

binding ability of the former was much higher than that of the

latter. K -binding ability of cyclic [18]crown-6 was much higher

than its Na -binding ability, while the reverse was true for acyclic compound 1. Single-crystal X-ray structural analysis of Na ·1·

B(Ph) ·(hexane) at 100 K revealed the existence of a wrapped Na -coordination by six ether and one carbonyl oxygen atoms of 1,

−

which was further stabilized by intramolecular N−H···O hydrogen-bonding interactions. The complex phase transition during

−

glass (G) formation and recrystallization was conﬁrmed in the thermal cycle of Na ·1·B(Ph) , whose molten state showed two

−

kinds of liquid phases, Na -complexed (Na ·1) + B(Ph) and completely dissociated Na + 1 + B(Ph) . The Na conductivity of

the molten state was 2 orders of magnitude higher than that of the G phase.

,10

. INTRODUCTION

respectively, in CH OH.

Therefore, the pK value of the

macrocyclic system is 3 or 4 orders of magnitude higher than

that of the acyclic system. The conformational freedom of

acyclic oligo(ethylene glycol) derivatives drastically decreases

Crown ether derivatives can recognize a variety of cations

−4

based on the size of the central cavity of macrocycles.

For

instance, Na and K cations can ﬁt well into the cavities of

15]crown-5 and [18]crown-6, respectively, forming planar

the M -binding ability relative to the binding ability of

[

4−6

conformationally rigid cyclic crown ethers. This is known as

cyclic Na ([15]crown-5) and K ([18]crown-6) structures.

5,16

the macrocyclic eﬀect.

The driving force for binding cations (M ) inside the cavity of

a crown ether is the electrostatic attractive interaction of the

lone pairs of oxygen atoms of the macrocyclic ether.

Additionally, the oxygen atoms have a much higher aﬃnity

The ion-recognized crown ether and oligo(ethylene glycol)

derivatives can form interesting ion-encapsulated static and

dynamic molecular assemblies.

array of crown ethers forms an artiﬁcial ionic channel that has

17−24

For instance, a regular

−3,7,8

for hard cations than soft cations.

Based on the complex

formation constant (pK), the aﬃnity of [18]crown-6 for alkali-

been applied for the design of functional ion-transport systems

25−27

metal ions in the CH CN solution phase decreases in the order

in molecular assemblies.

crown-6), where M = Li , Na , and Cs , have been introduced

into the electrically conducting [Ni(dmit) ] salts (dmit = 2-

The ionic channels of M ([18]-

K (pK = 5.46) > Rb (pK = 4.89) ∼ Cs (pK = 4.83) > Na

pK = 4.21), depending on the compatibility between the

cavity size and ionic radii.

2−

(

,10

For instance, owing to the much

thioxo-1,3-dithiole-4,5-dithiolate); the ion dynamics inside the

channels have been investigated based on the electrical

smaller pore diameter of [15]crown-5 compared to that of

8−30

[

18]crown-6, the aﬃnity of Na ions was much higher than

conductivity and magnetic susceptibility.

A small-sized

that for K one. The pK values of [15]crown-5 for Na and K

cations are 5.38 and 3.98, respectively, while those of

Li cation inside the cavity of [18]crown-6 has motional

freedom, while the dynamics of a Na cation inside [18]crown-

is subtly restricted due to the eﬀective binding of Na to the

six ether oxygen atoms. In addition, the large-sized Cs cation

[

18]crown-6 for the same cations are 4.21 and 5.46,

,10

respectively, in CH CN.

Therefore, the strategic design of

the macrocyclic ring size is an important factor for controlling

the cation selectivity. Similar electrostatic interactions at the

Received: April 8, 2021

Revised: May 20, 2021

Published: June 4, 2021

oxygen atoms of the ether units (−OC H −) for M have been

11−13

reported in an acyclic oligo(ethylene glycol) derivative.

These acyclic ethers can also recognize alkali-metal ions, and

the pK values of dimethyl-penta(ethylene glycol); pentaglyme,

for Na and K cations are 1.52 and 2.20, respectively, while

those of [18]crown-6 for the same cations are 4.36 and 6.06,

2021 American Chemical Society

J. Phys. Chem. B 2021, 125, 6349−6358

349

The Journal of Physical Chemistry B

Article

−

Scheme 1. Molecular Structures of 1 and the Na ·1 Complex with the B(Ph)₄Counter Anion

cannot pass through the cavity of [18]crown-6 and is ﬁxed

between the [18]crown-6 molecules. Such cation dynamics

and its arrangement in the crystal lattice aﬀect the electrical

rotation of the rigid core along the long axis of the

46,47

molecule.

Thermal conversion between the trans and

gauche conformation of the alkyl chain occurs typically in

liquid phases, and such dynamics play an important role in the

appearance of the liquid crystal phase. In liquid crystalline

materials, alkyl chains such as −C H , −OC H₂_n₊₁,

conducting behavior of the regular π-stack of [Ni(dmit) ] via

the generation of periodic and random potentials for the

28,29

conduction electrons.

The cation structure of K [penta-

2n+1

(

ethylene glycol)] has been introduced into the electrically

−COOC H , and −OOCC H

are fused at the rod-like

rigid core. Among them, the alkylamide group of

−CONHC H is an interesting hydrogen-bonding structural

2n+1

conducting [Ni(dmit) ] crystals. However, the low M -

binding ability of oligo(ethylene glycol) derivatives restricts the

2n+1

crystal formation of the [Ni(dmit) ] salt, including a variety of

unit for stabilizing the liquid crystal phase, as ﬁrst

supramolecular cations. In contrast, Li -conducting materials

demonstrated by Matsunaga et al. for the discotic hexagonal

48−50

such as Li -coordination polymers of poly(ethylene glycol)

columnar (Col ) liquid crystal phase.

The eﬀective

derivatives have been extensively developed for their

intermolecular N−H···O hydrogen-bonding interaction

enhances the order of molecular assembly in the intrinsic

liquid state, leading to the appearance of the mesophase before

melting to the liquid phase. For instance, a benzene derivative

32,33

application as electrolytes in Li secondary batteries.

Structural analysis of the Li [poly(ethylene glycol)] derivative

revealed a helical Li -coordination between the Li cation and

ether oxygen atoms.

bearing three −CONHC H

chains at the 1, 3, and 5-

positions (3BC) forms the Col liquid crystal phase by the aid

2n+1

Oligo(ethylene glycol) and poly(ethylene glycol) derivatives

have been widely utilized for the formation of speciﬁc

of intermolecular N−H···O hydrogen-bonding interac-

4,35

49,50

molecular assemblies such as micelles and vesicles.

Highly

tions.

Interestingly, the application of electric ﬁeld (E)

water soluble ethylene glycol chains are useful for designing

drug delivery systems and for fabricating biocompatible

along the hydrogen-bonding column of 3BC resulted in a

ferroelectric response in the polarization−electric ﬁeld (P−E)

curve, wherein the dipole moment of each hydrogen-bonding

chain was inverted by the application of outer E along the π-

6,37

molecular systems.

On the other hand, molecular

assemblies of hydrophobic molecules bearing long alkyl chains

are stabilized by multiple van der Waals interactions; these

molecular assemblies include micelles, vesicles, and Langmuir−

51−55

stack.

Further chemical design of the central core, from

simple benzene to functional π-molecular systems such as

8−40

Blodgett ﬁlms.

Although van der Waals interactions are

pyrene and tetrabenzoporphyrin, has been utilized for

6−59

much weaker than electrostatic, hydrogen-bonding, and

charge-transfer interactions, the multitude of such interactions

in long alkyl chain compounds eﬀectively enhances the total

energy of the intermolecular interactions. The intermolecular

van der Waals interaction between the alkyl chains is more

than that between the oligo(ethylene glycol) chains, which was

conﬁrmed by the considerably higher melting point of n-

alkanes than that of the oligo(ethylene glycol) derivatives with

fabricating multifunctional molecular materials.

For

instance, a pyrene derivative bearing four −CONHC H

chains exhibits ferroelectricity, ﬂuorescence, and current-

switching behavior. Most importantly, it can form multifunc-

tional molecular assemblies such as organogels and nano-

56−58

ﬁbers

The non π-planar 2,5-dimethylhelicene derivative

bearing two −CONHC H chains also exhibited ferroelec-

tricity, as evident from the P−E hysteresis curve. Moreover,

single-crystal X-ray structural analysis of this molecular system

revealed the presence of a two-dimensional (2D) N−H···O

41,42

the same chain length.

For instance, the melting point of

the pentadecane (n-C H ) crystal (283 K) was 40 K higher

than that of the tetraglyme of C H O (243 K). A useful

hydrogen-bonding network. The polar alkylamide chain is

crystal engineering approach to enhance the intermolecular

interaction has been demonstrated by utilizing the molecular

fastener eﬀect in electrically conducting tetrathiafulvalene

one of the useful structural units to design dynamic molecular

assemblies.

In this study, we designed a penta(ethylene glycol)

derivative (1), which exhibited ion-recognition ability and

contained hydrogen-bonding N−H···O sites and hydro-

phobic long alkyl chains of −CONHC H (Scheme 1). It

(

TTF) derivatives bearing four long alkylthio chains

−SC H₂_n₊₁), where the multiple van der Waals interactions

between the alkylthio-chains eﬀectively bind the TTF π-

molecular system in a one-dimensional (1D) column.

42,43

The

was further applied as a new hydrogen-bonding ion-

recognition molecular system. The six ether oxygen atoms of

the penta(ethylene glycol) unit in 1 could adopt a cyclic

conformation by coordinating to an alkali metal ion. The

conformational freedom of the alkyl chain can be partially

melted even in solids. For instance, several n-alkane crystals

showed an ordered crystal−plastic crystal phase transition by

thermally activated 1D rotation along the long axis of the

coexistence of a hydrophilic cation-binding M [penta(ethylene

4,45

molecule.

In addition, most of the thermotropic liquid

glycol)] unit and the hydrophobic long −C H alkyl chains

crystalline molecules have both a rigid core and ﬂexible lateral

alkyl chain(s), and the transition to the liquid crystal phase was

accompanied by the melting of the alkyl chain(s) and the free

renders the ion-recognized M ·1 complex amphiphilic. Owing

to the cation-binding ability of acyclic compound 1, together

with the N−H···O hydrogen-bonding interaction, the

350

The Journal of Physical Chemistry B

J. Phys. Chem. B 2021, 125, 6349−6358

Article

Figure 1. Na - and K -binding abilities of 1 in CDCl −CD CN (v/v = 1/9). (a) Na concentration (c )-dependent change in δ-values of the C−

−

H proton of 1 (at a ﬁxed concentration of 10 mM) upon the addition of Na ·BPh . (b) c - and c -dependent changes in Δδ values of 1 upon the

addition of Na ·BPh (left scale) and K ·BPh (right scale).

−

molecular conformation changes drastically after M recog-

nition and provides higher conformational freedom than that

and further stirred at 298 K for 30 min. After quenching the

reaction by the addition of water, the solution was washed with

saturated NH Cl, NaHCO , and brine (30 mL × 1) and dried

in cyclic [18]crown-6. The Na - and K -binding abilities of

acyclic molecule 1 in the solution phase were compared with

those of cyclic [18]crown-6. The molecular assemblies of 1

on sodium sulfate overnight. The solvent was removed in

vacuum, and the crude product (9.15 g) was puriﬁed by silica

gel column chromatography (ethyl acetate/toluene/ethanol =

10/10/1) to aﬀord colorless oil compound 1a (3.66 g 7.84

and the Na ·1 complex were examined in terms of their

thermal stability, phase transition behavior, molecular

structure, packing structure, dielectric response, and ionic

conductivity. This is expected to provide further design

strategies for functional molecular assemblies based on

hydrogen-bonding acyclic ion-recognition molecules.

mmol) with a yield of 37%. H NMR: δ 4.02 (s, 4H), δ 3.70

(m, 20H), δ 1.48 (s, 18H).

.2.2. Preparation of 3,6,9,12,15,18-Hexaoxaicosane-

,20-dioic Acid (1b). Triﬂuoroacetic acid (12.4 mL) was

slowly added to a solution of 1a (3.66 g 7.84 mmol) in CH Cl

. METHODS

.1. Physical Measurements. H NMR spectra were

(10 mL) and stirred at 298 K for 2 h. The solvent and an

excess amount of triﬂuoroacetic acid were removed in vacuum.

Compound 1b (6.36 g) was used for the next reaction without

puriﬁcation.

recorded on a Bruker AVANCE III 400 NMR spectrometer,

and chemical shifts (δ, ppm) were obtained relative to

tetramethylsilane as an internal standard. Temperature-

dependent infrared (IR) spectra were recorded in the range

2.2.3. N ,N -Ditetradecyl-3,6,9,12,15,18-hexaoxaicosane-

diamide (1). Compound 1b (6.36 g, 18.0 mmol) in SOCl₂

(31.5 mL) was stirred overnight at 338 K, and the residual

−

00−4000 cm using KBr pellets on a Thermo Fisher

SOCl was removed in vacuum. The reaction products were

Scientiﬁc Nicolet 6700 spectrophotometer with a resolution of

−

dissolved in anhydrous CH Cl (30 mL), and triethylamine

cm . Thermogravimetric (TG) analysis and diﬀerential

(

7.5 mL, 53.8 mmol) and tetradecylamine (9.59 g, 45.0 mmol)

scanning calorimetry (DSC) were conducted using a Rigaku

Thermo plus TG8120 thermal analysis station and Mettler

DSC1-T with an Al O reference, respectively, with a heating

were added to the solution and stirred at 298 K for 5 days.

After the addition of water, the organic layer was washed three

times with saturated brine and dried overnight on sodium

−

and cooling rate of 5 K min under a nitrogen atmosphere.

The temperature-dependent dielectric constants were meas-

ured using the two-probe AC impedance method from 100 Hz

to 1 MHz (Hewlett-Packard, HP4194A); a Linkam LTS-E350

temperature controller system was used for the measurement.

sulfate. After removing CH Cl , the crude product was puriﬁed

by silica gel column chromatography (eluted using toluene/

ethanol in the ratio 8:2, 7:3, to 2:3) passing through activated

carbon. The product was recrystallized from CH CN as a

white powder (compound 1, 1.47 g) with a yield of 9%.

Compound 1 or Na ·1 was fabricated in its liquid state into an

Elemental analysis: Calcd. for C H N O : C: 67.70, H:

indium tin oxide (ITO) glass (SZ-A311P6N) and was

sandwiched by the corresponding ITO glass to form the

dielectric measurement cell with an average electrode gap of 2

μm. Temperature-dependent powder X-ray diﬀraction

42 84

1.36, N: 3.76. Found: C: 67.77, H: 11.61, N: 3.78. H NMR

(

400 MHz, CDCl ): δ 6.95 (s, 2H), 3.98 (s, 4H), 3.68−3.65

m, 20H), 3.27 (q, J = 6.8 Hz, 4H), 1.52 (t, J = 6.8 Hz, 4H),

(

PXRD) was performed using a Rigaku SmartLab diﬀrac-

tometer with Cu Kα (λ = 1.54187 Å) radiation.

.2. Preparation of 1. 2.2.1. Preparation of Di-tert-butyl

,6,9,12,15,18-Hexaoxaicosane-1,20-dioate (1a). Aq. NaOH

50 wt %, 50 mL) was poured into a solution of pentaethylene

1.30−1.25 (m, 46H), 0.88 (t, J = 6.8 Hz, 6H).

2.3. Crystal Structure Determination. Single crystals of

−

Na ·1·B(Ph) ·(hexane) were obtained by slow evaporation

4 2

from a propanol−hexane (1:2 (v/v)) mixture. Crystallographic

data were collected on a Rigaku RAPID-II diﬀractometer

equipped with a rotating anode ﬁtted with multilayer confocal

optics, using Cu Kα (λ = 1.54187 Å) radiation from a graphite

monochromator. Structural reﬁnements were performed using

(

glycol (5.07 g, 21.3 mmol) in toluene (50 mL) at 273 K. After

the addition of tetrabutylammonium hydrogen sulfate (16.0 g,

6.8 mmol) and tert-butyl bromoacetate (12.4 mL, 85.1

mmol), the reaction mixture was stirred at 273 K for 10 min

the full-matrix least-squares method on F . Calculations were

351

J. Phys. Chem. B 2021, 125, 6349−6358

The Journal of Physical Chemistry B

Article

performed using the crystal structure software packages. All the

parameters, except for those of the hydrogen atoms, were

1,62

reﬁned using anisotropic temperature factors.

Crystal data

of Na -1, C H BN NaO : F.W. = 1257.69, crystal

130

dimensions, 0.30 × 0.05 × 0.01 mm , T = 100 K, triclinic

P1 (#2), a = 9.9634(5), b = 12.9623(6), c = 29.9897(15) Å, α

96.640(7), β = 92.811(7), γ = 96.951(7)°, V = 3811.1(3) Å ,

−

−1

Z = 2, D_c_a_l_c_d= 1.096 g cm , μ = 5.807 cm , 9285 collected,

350 unique, R_i_n_i_t= 0.0510, R = 0.0832, R = 0.1559, R =

.2878, and G.O.F = 0.944. The maximum and minimum

1 all w

peaks on the ﬁnal diﬀerence Fourier map corresponded to

−

−3

0.36e and −0.32e Å , respectively. CCDC-2076312.

. RESULTS AND DISCUSSION

−

.1. Ion Recognition Ability of Compound 1 in

Figure 2. Phase transition behavior of solid 1 and Na ·1·B(Ph) . (a)

−

Solution. The pore radius of the central cavity of [18]-

crown-6 (1.31 Å) is similar to the ion radius (r ) of K (1.38

Å), indicating a high K -binding ability with a pK of 5.46 in

CD CN. The pore size of [18]crown-6 is slightly larger than r

of Na (0.95 Å), and binding to Na decreases the pK value by

one order of magnitude (pK = 4.21) for the K -binding ability.

DSC curves of 1 (black) and Na ·1·B(Ph)

(red), where S1, S1′, S2,

G, and L represent solid 1, solid 1′, solid 2, glass, and isotopic liquid

−

phases, respectively. (b) POM images of Na ·1·B(Ph) under cross-

Nicole optical arrangements: the G phase at 250 K (top), the G + S1

phase at 310 K (middle), and the S1′ phase at 310 K (bottom).

The ion-recognition ability of oligo(ethylene glycol) is 3 or 4

orders of magnitude lower than that of a crown ether of a

similar size. However, conformational freedom of the acyclic

molecular structure of the oligo(ethylene glycol) derivative

depends on the ions. Figure 1a summarizes the change in

cycle up to 373 K (Figure S5). The transition enthalpy changes

(ΔH) were 24.7 and 97.4 kJ mol , respectively. However, the

L−S2 and S2−S1 phase transitions were observed at 330 (ΔH

−

−1

= −101.5 kJ mol ) and 320 K (ΔH = −31.5 kJ mol ) in the

cooling process. This supercooling phenomenon exhibited by

1 was consistent with a ﬁrst-order phase transition behavior.

A complex phase transition behavior was observed for the

chemical shift (δ, ppm) of the C−H proton of 1 (at a ﬁxed

concentration of 10 mM) in CDCl −CD CN (v/v = 1/9)

−

upon the addition of Na ·BPh at a Na concentration (c )

Na ·1·B(Ph) salt (red trace in Figure 2a). The melting point

−

of up to 30 mM. The C−H proton signals of 1 were shifted

of Na ·1·B(Ph) was found to be 327 K, with ΔH = −78.1 kJ

−1

downﬁeld from 3.87 ppm (c = 0 mM) to 3.91 ppm (c = 30

mol , which was about ∼30 K lower than that of solid 1 (357

K). The POM images of the L phase were observed in a

complete dark domain under a cross-Nicole optical arrange-

ment and were consistent with the formation of an isotropic

liquid state. The formation of a liquid crystal phase was not

mM) upon the addition of Na ions (Figure S2 ). Similar

downﬁeld shifts of the C−H proton of 1 were observed upon

−

the addition of K ·BPh , suggesting the K -binding ability in

CDCl −CD CN (v/v = 1/9) (Figure S3). Figure 1b shows the

−

ion (M = Na and K) concentration (c )-dependent shift of the

conﬁrmed in the Na ·1·B(Ph) salt, while the viscous L phase

δ value (Δδ, ppm) of 1 upon the addition of Na and K ions.

suggested the existence of eﬀective short-range electrostatic

interactions. The formation of cation−anion pairs in the L

phase corresponded to the ionic liquid state at 298 K in the

cooling process, in the temperature range from 390 to 260 K.

The Δδ values were saturated at high c for both Na and K

ions, which was consistent with the ﬁrst-order binding of 1

with M , that is, 1 + M = M ·1, in the solution phase. The pK

−

values of 1 for Na and K were found to be 4.30 and 3.89,

respectively, upon curve ﬁtting (Figure 1a). Interestingly, the

The supramolecular treatment of Na ·B(Ph) by the addition

of 1 formed the ionic liquid state, where the signiﬁcant

pK value for Na was higher than that for K . Although both

18]crown-6 and the penta(ethylene glycol) unit of 1 have six

OC H − oxygen atoms, the Na -binding ability of the acyclic

compound 1 was much higher than that of [18]crown-6. The

pK values of pentaglyme for Na and K were 1.52 and 2.20,

respectively, while those of [18]crown-6 for the same cations

were 4.36 and 6.06, respectively, in CH OH. Therefore, the

Na -binding ability of acyclic compound 1 should be much

lowering of melting occurred to decrease the electrostatic

[

−

interaction of Na . The birefringence POM image by

crystallization was not recovered upon cooling the molten

−

Na ·1·B(Ph) salt from the L phase at 390 K and a dark POM

image was obtained (Figure S6). A small phase transition peak

−1

was observed at 260 K, with ΔH = 25.9 kJ mol . No ﬂuidic

behavior was observed below 260 K and dark POM images

were obtained. Therefore, the phase transition from L to glass

,10

−

higher than that of pentaglyme bearing the same number of

(G) occurred in the Na ·1·B(Ph) molten salt via the

−

C H O− units within the molecule.

supercooled state below 240 K. The stable G phase at 220 K

was observed around 298 K in the second heating process, and

two endothermic peaks were observed at 283 and 301 K

corresponding to the crystallization of the G phase. The sum of

the ΔH values for the G−S1 and G−S1′ phase transitions was

.2. Phase Transition Behavior. Thermal stability and

−

phase transition behavior of 1 and Na ·1·B(Ph) were

evaluated by TG and DSC. The single crystals of Na ·1·

−

B(Ph) ·(hexane) included 2 mol of the crystallization

−

solvent, hexane, which was rapidly removed at 298 K. Weight

58.3 kJ mol , which is slightly lower than the ΔH value at the

−

−1

losses of 1 and Na ·1·B(Ph)₄were observed at 500 and 480

K, respectively, in the TG curves (Figure S4 ), suggesting the

slightly higher thermal stability of 1 than the cation−anion

melting point (−78.1 kJ mol ). After the ﬁrst step, the G−S1

phase transition, both the G and S1 phases coexisted in the

same domain as evident from the simultaneous appearance of

the dark and bright domains in the POM image (Figure 2b,

middle panel). The second step, S1−S1′ crystallization,

resulted in the complete recovery of the bright crystalline

−

Na ·1·B(Ph) salt. Figure 2a shows the DSC curves of 1 and

−

Na ·1·B(Ph) . Solid 1 underwent a phase transition in two

stepsS1−S2 at 336 K and S2−L at 357 Kin the heating

352

J. Phys. Chem. B 2021, 125, 6349−6358

The Journal of Physical Chemistry B

Article

domain in the POM image (Figure 2b, lower panel). This

2.511(6) Å; the average Na ···O distance was 2.42 Å. In

−

thermal cycle of Na ·1·B(Ph)₄was found to be reversible in

the DSC measurements. The structural reconstruction of the

cation−anion pair in the G phase is the origin of the G−S1

addition, one carbonyl oxygen atom (O) was coordinated to

Na with d

= 2.405(5) Å, resulting in a hepta-coordinated

Na−O

structure around Na . Furthermore, an additional N−H···O

intramolecular hydrogen-bonding interaction with d =

N−H

3.061(7) Å stabilized the Na -binding cyclic molecular

conformation (Figure S8). In the Na ([18]crown-6)Br single

crystal, the Na ion existed inside the cavity of [18]crown-6

−

(

S1′) phase transition of Na ·1·B(Ph) during the heating

process.

.3. Structure of the Molecular Assembly. Structures of

the molecular assemblies of 1 and Na ·1·B(Ph) were

investigated by temperature (T)-dependent XRD and single-

−

and was surrounded by six ether oxygen atoms with d_N_a₋_O₁=

crystal X-ray structural analyses, respectively. Single crystals of

2.464(3), d_N_a₋_O₂= 2.618, and d_N_a₋_O₃= 2.679 Å. The other

three Na−O distances were longer than 2.8 Å, and only weak

interactions were present between Na and the oxygen atoms.

distance (2.79 Å) in the Na ([18]crown-

6)Br crystal was 0.35 Å longer than that in Na ·1, in which

d_N_a₋_O= 2.42 Å. Therefore, Na was strongly bound in the

−

Na ·1·B(Ph) ·(hexane) were successfully obtained by slow

evaporation from a propanol−hexane mixture; the crystals

were unstable in air at 298 K due to the rapid elimination of

hexane molecules. Figure 3 summarizes the crystal structure of

The mean d

Na‑O

−

wrapped-coordination of 1 with the aid of additional

interactions at the carbonyl O site and by the intramolecular

N−H···O hydrogen-bonding interaction. These could be

modulated to an appropriate coordination distance in order to

increase the pK of 1; this was in contrast to cyclic [18]crown-6.

On the other hand, the lower K -binding ability of 1 compared

to the Na -binding ability was consistent with the absence of

−

any crystals of K ·1·B(Ph) ·(hexane) . The large K ion

suppressed the formation of intramolecular N−H···O

hydrogen-bonding interaction and destabilized the formation

of the wrapped K ·1 complex. Two long −C H chains of the

Na ·1 complex elongated along the same direction and

interacted with each other through multiple van der Waals

interactions to stabilize the Na -binding molecular structure.

Figure 3b shows the unit cell of Na ·1·B(Ph) ·(hexane)

viewed along the b axis; the B(Ph)₄anions and hexane were

omitted for clarity. A lamellar-type 2D molecular assembly

structure was observed in the alternate arrangement of the

cation −anion bilayer and hydrophobic alkyl layer along the c

axis (Figure S9 ). The hydrophobic −C H chains assembled

with each other in the ab plane, and hexane molecules were

required to form the closest packing structure. The Na ·1

cation and the bulky B(Ph)₄anion were alternatively arranged

−

Figure 3. Crystal structure of Na ·1·B(Ph) ·(hexane) . (a)

Molecular structure of Na ·1. (b) Unit cell viewed along the b axis.

The bulky B(Ph)₄anion and hexane are omitted for clarity. (c) 2D

−

cation−anion bilayer arrangement in the ab plane.

−

in the ab plane (Figure 3c), forming a bilayer-type electrostatic

cation−anion Coulomb layer that was sandwiched by the

hydrophobic alkyl layers. The layer periodicity along the c axis

was 29.9897(15) Å at 100 K.

Figure 4a shows the PXRD patterns of the S1 and S2 phases

of solid 1. The structures of the crystalline molecular

assemblies of 1 were conﬁrmed by the appearance of sharp

−

Na ·1·B(Ph) ·(hexane) at 100 K (Figure S7). Structural

information on the Na -coordination from 1 clariﬁed the high

Na -binding ability. Six ether oxygen atoms eﬀectively

interacted with Na , with the following Na ···O distances

d_N_a₋_O): d_N_a₋_O₁= 2.457(7), d_N_a₋_O₂= 2.393(6), d_N_a₋_O₃

.403(5), d _N _a ₋_O ₄ = 2.394(6), d _N _a ₋_O ₅ = 2.406(5), and d _N _a ₋_O ₆

(

−

Figure 4. Structures of the molecular assemblies of 1 and Na ·1·B(Ph) . (a) PXRD patterns of solid 1 for the S1 phase (T = 250 K) and the S2

−

phase (T = 370 K). (b) T-dependent PXRD patterns of Na ·1·B(Ph) from the initial S1 phase (T = 300 K), the L phase (T = 350 K), the G

phase (T = 300, 260, and 240 K), and the S1−S1′ phases (T = 240, 260, and 300 K).

353

The Journal of Physical Chemistry B

J. Phys. Chem. B 2021, 125, 6349−6358

Article

Figure 5. DSC curves and T- and f-dependent real components of the dielectric constants, ε , of (a) 1 in the heating process and (b) Na ·1·

−

B(Ph)₄in the cooling process from 360 K.

Bragg reﬂections in the PXRD patterns of the S1 and S2

phases. An intense Bragg reﬂection peak was observed in the

low-angle region at 2θ = 6.512° in the S1 phase, corresponding

to a d-spacing of 13.6 Å. For the S2 phase, peaks were observed

at 2θ = 3.520 and 7.040°, corresponding to a d-spacing of 25.1

Å. The almost similar PXRD patterns of the S1 and S2 phases

of solid 1 suggested a structure with nearly similar molecular

assembly, along with a slight structural modulation at the S1−

S2 phase transition. A broad diﬀraction peak at 2θ ≈ 20°

overlapped with the sharp Bragg reﬂection peaks of the S1 and

S2 phases, which was consistent with the partially melted state

of the terminal −C H chains.

corresponded to the dissociation of the cation−anion pair in

the L phase.

3.4. Dielectric Properties. T- and f-dependent dielectric

constants are sensitive to the motional freedom of the polar

structural unit in a molecular assembly. The real part (ε ) and

imaginary part (ε ) of the dielectric constants correspond to

the capacitance and conductance, respectively. For instance, a

typical ionic conductor shows a large ε response due to the

contribution of the dielectric-loss. Figure 5a shows the T- and

f-dependent ε response and the DSC curve of 1 during the

heating cycle. The ε -value was 3.2 at 300 K, and it increased

to ∼3.5 at the S1−S2 phase transition of solid 1 at 332 K

(Figure 5a, inset). This was dominated by a small structural

transformation without any drastic change in the motional

freedom of the polar structural unit such as N−H···O

hydrogen-bonding interaction. Further heating of the S2 phase

The formation of the G phase was conﬁrmed by the T-

−

dependent PXRD patterns of Na ·1·B(Ph) (Figure 4b). The

−

simulated PXRD pattern of Na ·1·B(Ph) ·(hexane) based on

the single-crystal X-ray structural analysis at 100 K indicated

sharp Bragg reﬂection peaks and high crystallinity (Figure

S10 ). However, removal of the crystallized hexane molecules at

gradually increased the ε values for low-f measurements, and

the maximum value of ε (ε = 270) was obtained at T = 355 K

98 K decreased the crystallinity, as evident from the

and f = 0.316 Hz. Thermal ﬂuctuations of the polar N−H···

O hydrogen-bonding interactions are activated before the

melting of solid 1, and dissociation of the hydrogen-bonding

interaction resulted in melting at the S2−L phase transition.

The trend in the ε values was similar to that in the ε values

appearance of a new broad hallow in the PXRD pattern of

the initial S1 phase at 300 K (black curve in Figure 4b).

Removal of hexane molecules from the space between the alkyl

chain layer in the ab plane generated an empty crystalline

space, where the motional freedom of the −C H chains was

(Figure S11 ), and the contribution from the ionic conduction

was negligible in both S1 and S2 phases. The PXRD patterns of

the S2 phase suggested the partial melting of the two −C H

thermally activated at 300 K. The broad reﬂection peak at 2θ ≈

0° was consistent with the partially melted state of the alkyl

chains in the S1 phase (T = 300 K). The sharp Bragg

reﬂections completely disappeared upon the S1−L phase

transition, and only a broad hallow was observed at 2θ = 20°.

The same liquid-like PXRD patterns were maintained during

the cooling of the L phase down to 240 K, which was

consistent with the formation of the G phase. When the G

phase was partially crystallized in the S1 phase in the second

heating cycle, the sharp Bragg reﬂection peaks were recovered

and were overlapped with the broad hallow at 2θ = 20° as well

as the sharp reﬂection peaks at 2θ = 25.5° in the low angle

region for the S1 and S1′ phases. These low-angle intense

reﬂection peaks were consistent with a layer periodicity of ∼26

Å along the c axis; this was slightly lesser than 29.9897(15) Å,

which is obtained based on the single-crystal structural analysis

at 100 K after the partial melting of the alkyl chains. The most

dominant intermolecular interaction in the molecular assembly

chains, and it neither aﬀected the dielectric response nor

changed the dipole moments.

−

The ε -response of Na ·1·B(Ph) was remarkably diﬀerent

from that of solid 1. Figure 5b shows the T- and f-dependent

−

ε -response and DSC curves of the Na ·1·B(Ph) molten salt

−

in the cooling process from 360 K. The Na ·1·B(Ph) salt

showed a complex thermal behavior, accompanied by the

formation of the G phase from the L phase during the cooling

process. Additionally, two-step crystallization peaks were

observed during the heating cycle of the metastable G phase.

The ε value for the L to G phase transition at 265 K during

the cooling cycle suddenly dropped to 15 after the transition to

the G phase. The frozen dipole moments in the G phase were

inert for the ε -response at 265 K, which was consistent with

the DSC measurement. Recrystallization from the metastable

G state to the crystalline S1 and S1′ phases in the heating cycle

−

of Na ·1·B(Ph) is the electrostatic cation−anion Coulomb

led to the appearance of f-dependent ε -peaks around 285 K

layer in the ab plane, while the hydrophobic −C H chains

(Figure S12 ), suggesting a dynamic structural rearrangement of

−

exist in a dynamic state. The melting of the Na ·1·B(Ph) salt

the polar units in the G phase of Na ·1·B(Ph) . The polar

354

The Journal of Physical Chemistry B

J. Phys. Chem. B 2021, 125, 6349−6358

Article

−

Figure 6. Ionic conduction of the Na ·1·B(Ph) molten salt in the L phase. (a) T-dependent Cole−Cole plots in the T-range 299−349 K. (b)

DSC curve of the cooling cycle and T-dependent σ_N_afor the G and L phases.

−

Scheme 2. Phase Transition Behavior and Thermal Cycle of the Na ·1·B(Ph)₄Salt

−

The S1 → S1′ → L → L′ → L → G → S1 cycle was reversibly observed in the Na ·1·B(Ph)₄salt.

structural unit in the Na ·1·B(Ph)₄⁻molecular assembly is

B(Ph) , when the Na ions existed freely in the L phase

−

either the N−H···O hydrogen-bonding unit or the Na −

without coordinating to 1. TG chart of the Na ·1·B(Ph)

molten salt showed the formation of a thermally stable L phase

up to 500 K. The ε and ε values of Na ·1·B(Ph) at 360 K

−

B(Ph) ion pair. Although the T-dependent PXRD patterns of

−

Na ·1·B(Ph) revealed the existence of the partially melted

1 2 4

state of the two long alkyl chains, such dynamics were

insensitive to the dielectric spectra. Therefore, reconstruction

of the N−H···O hydrogen-bonding interaction and cation−

anion rearrangement contributed to the recrystallization from

the G to S1 (S1′) phase in the heating cycle. This behavior was

consistent with the dielectric measurements.

reached 4000 and 6500 at f = 316 Hz, which were two orders

of magnitude higher than those of 1 in the L phase. Therefore,

the dissociation of the cation−anion pair eﬀectively con-

tributed to the increased dielectric and also to the ionic

−

conductivity of the Na ·1·B(Ph) molten salt. The DSC curve

−

during cooling from 360 K showed a small endothermic peak

Interestingly, the ε values of the Na ·1·B(Ph) molten salt

−1

at 302 K, with ΔH = 2.70 kJ mol (top panel, Figure 6b),

in the L phase revealed T- and f-dependences above 265 K.

There are two possible dissociation steps for the cation−anion

where the ε value at low f suddenly dropped by two orders of

−

magnitude for the L−G phase transition at 280 K. Therefore,

pairs in the L phase of Na ·1·B(Ph) . The ﬁrst is the

−

two kinds of liquid phases, L and L′, existed in the Na ·1

dissociation of Na ·1·B(Ph) into the Na ·1 cationic complex

and the B(Ph)₄anion, where the Na -binding structure of 1

−

complex. The latter comprised an independent Na + 1 phase

was maintained even in the L phase. The second is the

and inﬂuenced the dielectric behavior and the Na ionic

complete dissociation of each component to Na , 1, and

conductivity of the L phase.

355

J. Phys. Chem. B 2021, 125, 6349−6358

The Journal of Physical Chemistry B

https://pubs.acs.org/doi/10.1021/acs.jpcb.1c03188.

Article

The f-dependent resistance (Z′) and reactance (Z′) plots

stabilized by the intramolecular N−H···O hydrogen-

were obtained at diﬀerent T, and the Na conductivity of the

bonding interaction and hydrophobic interactions between

−

Na ·1·B(Ph) molten salt was determined from the T-

the two long −C H alkyl chains. Although the structural unit

14 29

dependent Cole−Cole (Z′−Z″) plots in the cooling cycle from

of 1, which contains six ether oxygen atoms, is the same as that

50 to 299 K (Figure 6a). All the Z′−Z″ plots show

of [18]crown-6, the Na -binding ability of the acyclic

−1

semicircular traces for typical Na conduction (σ , S cm );

compound 1 was higher than that of cyclic [18]crown-6.

the σ_N_avalue was deﬁned at a cross-sectional point at the

horizontal Z′-axis. A stray resistance of ∼200 Ω was observed

in all the Z′−Z″ plots in the present measurement system.

The multiple Na ···O interactions eﬀectively trapped the Na

cation inside the hydrophilic penta(ethylene glycol) unit. The

two hydrophobic alkyl chains interacted via multiple van der

−

Figure 6b shows the T-dependent σ value of Na ·1·B(Ph)

Waals forces, supporting the Na -bound conformation. The

in the L phase. The less dynamic Na ions in the G phase

electrostatic cation−anion layer and hydrophobic alkyl chains

formed a 2D lamella-like molecular assembly. Thermal analysis

of solid 1 revealed the existence of an S1−S2 phase transition

decreased the σ_N_avalue to less than 10⁻S cm , while the G

−1

to L phase transition gradually increased the σ value up to 2

−

−1

−

10 S cm at 320 K. The small endothermic peak of the L

while that of the Na ·1·B(Ph) salt showed a complex phase

phase at 302 K in the DSC curve aﬀected the T-dependent σ_N_a

value. Thermal activation was observed in the T-range 260−

transition sequence, L → G → S1 → S1′ → L → L′ → L → G

−

→ S1. The ionic conductivity of Na in the Na ·1·B(Ph)

00 K, while σ was almost T-independent in the high-T

molten salt in the L phase showed two kinds of dynamics in

the T- and f-dependent dielectric responses. The σ_N_avalues in

the L phase were dominated by thermal activation in an

region of the L′ phase above 300 K. Dissociation of the Na ·1

complex was observed in the T-dependent equilibrium

between the Na ·1 complex and the completely dissociated

equilibrium between the Na ·1 complex and dissociated

independent Na + 1 in the solution phase, indicating the T-

species of Na + 1, while the complete dissociation of Na

dependent thermally activated conducting behavior. In

and 1 in the L′ phase showed a T-independent conducting

behavior. Thermally activated molecular motion of the

electrostatic cation−anion Coulomb pairs and the melting

state of the alkyl chains were randomly ﬁxed in the G phase,

which was reconstructed in the stable crystalline phase during

the heating cycle. The electrostatic cation−anion Coulomb

interaction ﬁrst reappeared, and the alkyl chains regained their

conformation to the lamella-type molecular assembly. The

conformational freedom and ion-recognition ability of the

acyclic amphiphilic 1 render it a potential compound in the

fabrication of ion-sensing and ionic channel materials. After

harnessing other physical properties such as electrical

conduction and ﬂuorescent responses, such materials can be

used to construct multifunctional molecular assemblies.

contrast, complete dissociation of Na and 1 in the L′ phase

corresponded to the T-independent behavior of σ in the L′

phase.

−

Single-crystal X-ray structural analysis of Na ·1·B(Ph) ·

(

hexane) at 100 K revealed a tight Na -binding structure of 1

held by intramolecular N−H···O hydrogen-bonding inter-

actions, which can be used to explain the phase transition

−

behavior of Na ·1·B(Ph) . First, the elimination of the

crystallized hexane molecules at 298 K resulted in the

formation of the crystalline S1 phase, in which the two alkyl

chains had motional freedom with a partially melted state and

the electrostatic cation−anion Coulomb layer was eﬀectively

maintained (Scheme 2). Heating of the S1 and S1′ phases

resulted in the transition to the molten L phase, in which the

Na cation was still tightly bounded by 1 to form the Na ·1

ASSOCIATED CONTENT

sı Supporting Information

The Supporting Information is available free of charge at

■

−

complex as the counter cation of bulky B(Ph) . Further

heating of the L phase changed the molecular assembly of the

Na ·1 complex to free Na + 1 species in the L′ phase. Cooling

of this phase reconstructed the L phase to form the Na ·1

complex and B(Ph)₄⁻anion. Further cooling of the L phase

ﬁxed the random orientation of each cation−anion pair with a

disordered conformation of the alkyl chains, forming the G

phase. The metastable G phase was transformed into the stable

crystalline S1 and S1′ phases upon heating, and the thermal

energy modulated the cation−anion Coulomb pair to recover

the 2D electrostatic lattice as well as the partially melted

IR spectra; NMR spectra of 1 and the change in Na and

K addition; TG charts;, POM images of 1 and Na ·1·

−

B(Ph) ; single-crystal X-ray structural analyses; simu-

lated PXRD patterns; T- and f-dependent imaginary part

dielectric constants; and T- and f-dependent dielectric

constants of G−S1 (S1′) transitions (PDF)

conformation of the two −C H chains. The S1 → S1′ → L

AUTHOR INFORMATION

Corresponding Author

■

→

L′ → L → G → S1 thermal cycle was reversibly observed in

+ −

heating and cooling cycles of the Na ·1·B(Ph) salt.

Tomoyuki Akutagawa − Graduate School of Engineering,

Tohoku University, Sendai 980-8579, Japan; Institute of

Multidisciplinary Research for Advanced Materials

. CONCLUSIONS

A penta(ethylene glycol) derivative (1) bearing two hydrogen-

bonding −CONHC H chains was prepared to achieve both

IMRAM), Tohoku University, Sendai 980-8577, Japan;

orcid.org/0000-0003-3040-1078 ; Phone: +81-22-217-

ion-recognition and hydrogen-bonding abilities. Compound 1

exhibited a much higher Na -binding ability than K -binding

ability in the solution phase, which was consistent with the

653; Email: akutagawa@tohoku.ac.jp; Fax: +81-22-217-

655

molecular structure of the Na ·1 complex based on the single

Authors

crystal X-ray structural analysis at 100 K. The six ether oxygen

atoms of penta(ethylene glycol) and one carbonyl O oxygen

atom at the −CONH− site were tightly coordinated to the

Shinya Seto − Graduate School of Engineering, Tohoku

University, Sendai 980-8579, Japan

Takashi Takeda − Graduate School of Engineering, Tohoku

University, Sendai 980-8579, Japan; Institute of

Na ion in a wrapped conformation, which was further

356

J. Phys. Chem. B 2021, 125, 6349−6358

The Journal of Physical Chemistry B

(15) Haymore, B. L.; Lamb, J. D.; Izatt, R. M.; Christensen, J. J.

Article

Multidisciplinary Research for Advanced Materials

Thermodynamic origin of the macrocyclic effect in crown ether

complexes of sodium(1+), potassium(1+), and barium(2+). Inorg.

Chem. 1982, 21, 1598−1602.

orcid.org/0000-0002-5254-2819

IMRAM), Tohoku University, Sendai 980-8577, Japan;

Norihisa Hoshino − Graduate School of Engineering, Tohoku

University, Sendai 980-8579, Japan; Institute of

Multidisciplinary Research for Advanced Materials

(16) Zhang, H.; Dearden, D. V. The gas-phase macrocyclic effect:

Reaction rates for crown ethers and the corresponding glymes with

alkali metal cations. J. Am. Chem. Soc. 1992 , 114 , 2754 −2755.

orcid.org/0000-0002-9841-6375

IMRAM), Tohoku University, Sendai 980-8577, Japan;

(17) Akutagawa, T. Dynamic molecular assemblies toward a new

frontier in materials chemistry. Mater. Chem. Front. 2018, 2, 1064−

1073.

Complete contact information is available at:

https://pubs.acs.org/10.1021/acs.jpcb.1c03188

18) Akutagawa, T. Chemical design and physical properties of

dynamic molecular assemblies. Bull. Chem. Soc. Jpn. 2021, 94, 1400−

420.

19) Han, Y.; Meng, Z.; Ma, Y.-X.; Chen, C.-F. Iptycene-derived

crown ether hosts for molecular recognition and self-assembly. Acc.

Notes

The authors declare no competing ﬁnancial interest.

Chem. Res. 2014, 47, 2026−2040.

(20) Fu, D.-W.; Zhang, W.; Cai, H.-L.; Zhang, Y.; Ge, J.-Z.; Xiong,

R.-G.; Huang, S. D. Supramolecular bola-like ferroelectric: 4-

methoxyanilinium tetrafluoroborate-18-crown-6. J. Am. Chem. Soc.

ACKNOWLEDGMENTS

■

This work was supported by a Grant-in-Aid for Scientiﬁc

Research on KAKENHI (JP19H00886, JP20H05865,

JP20K05442, and JP20H04655), JST CREST (grant number

JPMJCR18I4), and the “Dynamic Alliance for Open

Innovation Bridging Human, Environment and Materials”

project supported by MEXT.

21) Tang, Y.-Z.; Yu, Y.-M.; Xiong, J.-B.; Tan, Y.-H.; Wen, H.-R.

011, 133, 12780−12786.

Unusual High-Temperature Reversible Phase-Transition Behavior,

Structures, and Dielectric-Ferroelectric Properties of Two New

Crown Ether Clathrates. J. Am. Chem. Soc. 2015, 137 , 13345 −13351.

(22) Ye, H.-Y.; Zhang, Y.; Fu, D.-W.; Xiong, R.-G. A displacive-type

REFERENCES

■

metal crown ether ferroelectric compound: Ca(NO ) (15-crown-5).

3 2

2) Liu, Z.; Nalluri, S. K. M.; Stoddart, J. F. Surveying macrocyclic

1) Pedersen, C. J. Cyclic polyethers and their complexes with metal

salts. J. Am. Chem. Soc. 1967, 89, 7017−7036.

chemistry: From flexible crown ethers to rigid cyclophanes. Chem. Soc.

Rev. 2017, 46, 2459−2478.

3) Crown Ethers and Analogs; Patai, S., Rappoport, Z., Eds.; John

Wiley & Sons, 1989.

4) Gokel, G. W.; Leevy, W. M.; Weber, M. E. Crown ethers:

Sensors for ions and molecular scaffolds for materials and biological

Angew. Chem., Int. Ed. 2014, 53, 6724−6729.

(23) Akutagawa, T.; Koshinaka, H.; Sato, D.; Takeda, S.; Noro, S.-i.;

Takahashi, H.; Kumai, R.; Tokura, Y.; Nakamura, T. Ferroelectricity

and polarity control in solid-state flip-flop supramolecular rotators.

Nat. Mater. 2009, 8, 342−347.

(24) Hayata, A.; Itoh, H.; Inoue, M. Solid-phase total synthesis and

dual mechanism of action of the channel-forming 48-mer peptide

polytheonamide B. J. Am. Chem. Soc. 2018, 140, 10602−10611.

5) Buchanan, G. W.; Gerzain, M.; Bensimon, C. 1,4,7,10,13-

(25) Muraoka, T.; Noguchi, D.; Kasai, R. S.; Sato, K.; Sasaki, R.;

models. Chem. Rev. 2004, 104, 2723−2750.

Pentaoxacyclopentadecane (15-crown-5) sodium iodide complex,

Tabata, K. V.; Ekimoto, T.; Ikeguchi, M.; Kamagata, K.; Hoshino, N.;

Noji, H.; Akutagawa, T.; Ichimura, K.; Kinbara, K. A synthetic ion

channel with anisotropic ligand response. Nat. Commun. 2020, 11,

C H O •NaI. Acta Crystallogr., Sect. C: Cryst. Struct. Commun.

26) Eisenberg, B. Ionic channels in biological membranes: Natural

924.

nanotubes. Acc. Chem. Res. 1998, 31, 117−123.

27) Schneider, S.; Licsandru, E.-D.; Kocsis, I.; Gilles, A.; Dumitru,

6) Dunitz, J. D.; Dobler, M.; Seiler, P.; Phizackerley, R. P. Crystal

994, 50, 1016−1019.

structure analyses of 1,4,7,10,13,16-hexaoxacyclooctadecane and its

complexes with alkali thiocyanates. Acta Crystallogr., Sect. B: Struct.

Crystallogr. Cryst. Chem. 1974, 30, 2733−2738.

(

F.; Moulin, E.; Tan, J.; Lehn, J.-M.; Giuseppone, N.; Barboiu, M.

Columnar self-assemblies of triarylamines as scaffolds for artificial

biomimetic channels for ion and for water transport. J. Am. Chem. Soc.

7) Thompson, M. A.; Glendening, E. D.; Feller, D. The nature of

K /crown ether interactions: A hybrid quantum mechanical-

molecular mechanical study. J. Phys. Chem. 1994 , 98 , 10465 −10476.

8) Bruning, H.; Feil, D. Electrostatic interactions in host-guest

complexes 2. J. Comput. Chem. 1991, 12, 1−8.

9) Izatt, R. M.; Bradshaw, J. S.; Nielsen, S. A.; Lamb, J. D.;

Christensen, J. J.; Sen, D. Thermodynamic and kinetic data for cation-

macrocycle interaction. Chem. Rev. 1985, 85, 271−339.

10) Izatt, R. M.; Pawlak, K.; Bradshaw, J. S.; Bruening, R. L.

Thermodynamic and kinetic data for macrocycle interaction with

(

017, 139, 3721−3727.

28) Nakamura, T.; Akutagawa, T.; Honda, K.; Underhill, A. E.;

T.; Sugiura, K.-i.; Sakata, Y.; Underhill, A. E. Ionic channel structures

Coomber, A. T.; Friend, R. H. A molecular metal with ion-conducting

channels. Nature 1998, 394, 159−162.

(

(29) Akutagawa, T.; Hasegawa, T.; Nakamura, T.; Takeda, S.; Inabe,

in (M ) (18-crown-6)[Ni(dmit) ] molecular conductors, Chem.

2 2

Chem.Eur. J. 2001, 7, 4902−4912.

30) Akutagawa, T.; Hasegawa, T.; Nakamura, T.; Inabe, T.

cations, anions, and neutral molecules. Chem. Rev. 1995, 95, 2529−

Supramolecular cation assemblies of hydrogen-bonded (NH /

NH NH )(crown ether) in [Ni(dmit) ] based molecular conductors

586.

‑

11) Chan, K. W. S.; Cook, K. D. Mass spectrometric study of

and magnets. J. Am. Chem. Soc. 2002, 124, 8903−8911.

interactions between poly(ethylene glycols) and alkali metals in

solution. Macromolecules 1983, 16, 1736−1740.

12) Poudel, L.; Podgornik, R.; Ching, W.-Y. The hydration effect

and selectivity of alkali metal ions on poly(ethylene glycol) models in

cyclic and linear topology. J. Phys. Chem. A 2017, 121, 4721−4731.

13) Breton, M. F.; Discala, F.; Bacri, L.; Foster, D.; Pelta, J.;

(31) Akutagawa, T.; Hasegawa, T.; Nakamura, T.; Sugiura, K.-i.;

Sakata, Y.; Inabe, T.; Underhill, A. E. Supramolecular cation of an

acyclic polyether: Potassium(pentaethylene glycol) in a molecular

conducting nickel dithiolate salt. Chem. Commun. 1998, 2599 −2600.

(32) Mindemark, J.; Lacey, M. J.; Bowden, T.; Brandell, D. Beyond

Oukhaled, A. Exploration of neutral versus polyelectrolyte behavior of

poly(ethylene glycol)s in alkali ion solutions using single-nanopore

recording. J. Phys. Chem. Lett. 2013 , 4 , 2202 −2208.

PEO − Alternative host materials for Li -conducting solid polymer

electrolytes. Prog. Polym. Sci. 2018, 81, 114−143.

(33) Polymer Electrolyte; Gray, F. M., Connor, J. A., Eds.; RSC:

Cambridge, 1997.

14) Frensdorff, H. K. Stability constants of cyclic polyether

complexes with univalent cations. J. Am. Chem. Soc. 1971, 93, 600−

606.

(34) Won, Y.-Y.; Brannan, A. K.; Davis, H. T.; Bates, F. S. Cryogenic

transmission electron microscopy (cryo-TEM) of micelles and

357

J. Phys. Chem. B 2021, 125, 6349−6358

The Journal of Physical Chemistry B

vesicles formed in water by poly(ethylene oxide)-based block

Article

response of benzenecarboxamides bearing multiple −CONHC H

copolymers. J. Phys. Chem. B 2002, 106, 3354−3364.

chains. J. Phys. Chem. C 2014, 118, 21204−21214.

(35) Sou, K.; Endo, T.; Takeoka, S.; Tsuchida, E. Poly(ethylene

(56) Anetai, H.; Wada, Y.; Takeda, T.; Hoshino, N.; Yamamoto, S.;

Mitsuishi, M.; Takenobu, T.; Akutagawa, T. Fluorescent ferroelectrics

of hydrogen-bonded pyrene derivatives. J. Phys. Chem. Lett. 2015, 6,

1813−1818.

(57) Anetai, H.; Takeda, T.; Hoshino, N.; Araki, Y.; Wada, T.;

Yamamoto, S.; Mitsuishi, M.; Tsuchida, H.; Ogoshi, T.; Akutagawa,

T. Circular polarized luminescence of hydrogen-bonded molecular

assemblies of chiral pyrene derivatives. J. Phys. Chem. C 2018, 122,

glycol)-modification of the phospholipid vesicles by using the

spontaneous incorporation of poly(ethylene glycol)-lipid into the

vesicles. Bioconjugate Chem. 2000, 11, 372−379.

(36) Knop, K.; Hoogenboom, R.; Fischer, D.; Schubert, U. S.

Poly(ethylene glycol) in drug delivery: Pros and cons as well as

potential alternatives. Angew. Chem., Int. Ed. 2010, 49, 6288 −6308.

(37) Alcantar, N. A.; Aydil, E. S.; Israelachvili, J. N. Polyethylene

38) Shimizu, T.; Masuda, M.; Minamikawa, H. Supramolecular

323−6331.

glycol-coated biocompatible surfaces. J. Biomed. Mater. Res. 2000, 51,

43−351.

nanotube architectures based on amphiphilic molecules. Chem. Rev.

005, 105, 1401−1444.

39) Petty, M. C. Langmuir-Blodgett Films: An Introduction;

Cambridge University Press, 1996.

40) Ramanathan, M.; Shrestha, L. K.; Mori, T.; Ji, Q.; Hill, J. P.;

58) Anetai, H.; Sambe, K.; Takeda, T.; Hoshino, N.; Akutagawa, T.

Nanoscale effects in one-dimensional columnar supramolecular

ferroelectrics. Chem.Eur. J. 2019, 25, 11233−11239.

(59) Wu, J.; Takeda, T.; Hoshino, N.; Suzuki, Y.; Kawamata, J.;

(

Akutagawa, T. Ferroelectricity of a tetraphenyl porphyrin derivative

bearing −CONHC H chains at 500 K. J. Phys. Chem. C 2019, 123,

(

2439−22446.

(

60) Anetai, H.; Takeda, T.; Hoshino, N.; Kobayashi, H.; Saito, N.;

Ariga, K. Amphiphile nanoarchitectonics: From basic physical

chemistry to advanced applications. Phys. Chem. Chem. Phys. 2013,

Shigeno, M.; Yamaguchi, M.; Akutagawa, T. Ferroelectric alkylamide-

substituted helicene derivative with two-dimensional hydrogen-

bonding lamellar phase. J. Am. Chem. Soc. 2019, 141, 2391−2397.

(

5, 10580−10611.

41) Rumble, K. CRC Handbook of Chemistry and Physics, 100th ed.;

CRC Press, 2019.

42) Imaeda, K.; Enoki, T.; Shi, Z.; Wu, P.; Okada, N.; Yamochi, H.;

Saito, G.; Inokuchi, H. Electrical Conductivities of Tetrakis-

alkylthio)tetrathiafulvalene (TTCn-TTF) and Tetrakis(alkyltelluro)-

tetrathiafulvalene (TTeCn-TTF). Bull. Chem. Soc. Jpn. 1987, 60,

163−3167.

43) Ukai, S.; Igarashi, S.; Nakajima, M.; Marumoto, K.; Ito, H.;

(61) Crystal Structure: Single Crystal Structure Analysis Software, Ver.

.6; Rigaku Corporation and Molecular Structure Corporation, 2004.

62) Sheldrick, G. M. SHELX Programs for Crystal Structure Analysis;

Universitat Gottingen: Gottingen, Germany, 2018.

(

Kuroda, S.; Nishimura, K.; Enomoto, Y.; Saito, G. Molecular-fastener

effects on transport property of TTCn-TTF field-effect transistors.

Colloids Surf., A 2006, 284−285 , 589 −593.

(44) Ungar, G.; Masic, N. Order in the rotator phase of n-alkanes. J.

Phys. Chem. 1985, 89, 1036−1042.

(45) Cholakova, D.; Denkov, N. Rotator phases in alkane systems:

In bulk, surface layers and micro/nano-confinements. Adv. Colloid

Interface Sci. 2019, 269, 7−42.

(46) Collings, P. J.; Hird, M.. In Introduction to Liquid Crystals,

Chemistry and Physics; Gray, G. W., Goodby, J. W., Fukuda, A., Eds.;

Taylor & Francis: London, 1997.

(

47) Chandrasekhar, S. Liquid Crystal; Cambridge University Press:

Newyork, 1992.

48) Kobayashi, Y.; Matsunaga, Y. New Discogenic Com-

pounds:N,N ′-Dialkanoyl-2,3,5,6-tetrakis(alkanoyloxy)-1,4-benzenedi-

amines. Bull. Chem. Soc. Jpn. 1987, 60, 3515−3518.

(49) Matsunaga, Y.; Miyajima, N.; Nakayasu, Y.; Sakai, S.; Yonenaga,

M. Design of Novel Mesomorphic Compounds:N,N ′,N ″-Trialkyl-

50) Matsunaga, Y.; Nakayasu, Y.; Sakai, S.; Yonenaga, M. Liquid

,3,5-benzenetricarboxamides. Bull. Chem. Soc. Jpn. 1988, 61, 207−

10.

Crystal Phases Exhibited by N,N ′,N ″-Trialkyl-1,3,5-Benzenetricabox-

amides. Mol. Cryst. Liq. Cryst. 2011, 141, 327−333.

(51) Fitié, C. F. C.; Roelofs, W. S. C.; Kemerink, M.; Sijbesma, R. P.

Remnant polarization in thin films from a columnar liquid crystal. J.

Am. Chem. Soc. 2010, 132, 6892−6893.

(52) Fitié, C. F. C.; Roelofs, W. S. C.; Magusin, P. C. M. M.;

trialkylbenzene-1,3,5-tricarboxamides. J. Phys. Chem. B 2012, 116,

928−3937.

53) Urbanaviciute, I.; Meng, X.; Cornelissen, T. D.; Gorbunov, A.

bbenhorst, M.; Kemerink, M.; Sijbesma, R. P. Polar switching in

(

V.; Bhattacharjee, S.; Sijbesma, R. P.; Kemerink, M. Tuning the

ferroelectric properties of trialkylbenzene-1,3,5-tricarboxamide

(54) Wu, J.; Takeda, T.; Hoshino, N.; Akutagawa, T. Ferroelectric

BTA). Adv. Electron. Mater. 2017, 3, 1600530.

low-voltage ON/OFF switching of chiral benzene-1,3,5-tricarbox-

amide derivative. J. Mater. Chem. C 2020, 8, 10283−10289.

(55) Shishido, Y.; Anetai, H.; Takeda, T.; Hoshino, N.; Noro, S.-i.;

Nakamura, T.; Akutagawa, T. Molecular assembly and ferroelectric

358