Dynamic Resolution of Piezosensitivity in Single Crystals of π-Conjugated Molecules

Article abstract of DOI:10.1002/chem.201900054

Targeted synthesis of piezoresponsive small molecules and in-depth understanding of their mechanism is of utmost importance for the development of smart devices. This work reports the synthesis, structure and piezosensitivity of a bola-amphiphile 1,4-bis(pentyloxy)-2,5-bis(2-pyridineethynyl)-benzene (C5-PPB). Depending on the rate of compression, two different phases in C5-PPB can be generated. The ambient-pressure α-phase is stable up to 0.8 GPa, beyond which it undergoes an isostructural transformation to β-phase, accompanied by a clearly visible elongation of the crystal. This α-to-β phase transition requires the sample to be compressed slowly. When quickly compressed, phase α persists to about 1.5 GPa, beyond which its amorphization starts, accompanied by the appearance of irregular grooves on the largest faces. Mechanical pressure also affects the optical property of C5-PPB, which shows reversible mechanochromism with a green to cyan transformation in the emission, associated with a 15 nm shift in the maxima. The conductivity of C5-PPB as a direct outcome of its crystal packing has also been studied.

Full text of DOI:10.1002/chem.201900054

A Journal of
Accepted Article
Title: Dynamic Resolution of Piezosensitivity in a Single Crystal of π-
Conjugated Molecules
Authors: Sohini Bhattacharyya, Szymon Sobczak, Aleksandra
Polrolniczak, Syamantak Roy, Debarata Samanta, Andrzej
Katrusiak, and Tapas Kumar Maji
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content of this Accepted Article.
To be cited as: Chem. Eur. J. 10.1002/chem.201900054
Link to VoR: http://dx.doi.org/10.1002/chem.201900054
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Dynamic Resolution of Piezosensitivity in a Single Crystal of π-
Conjugated Molecules
Sohini Bhattacharyya,[a]# Szymon Sobczak,[b]# Aleksandra Półrolniczak,[b]# Syamantak Roy,[a]
Debabrata Samanta,[a] Andrzej Katrusiak, [b]* and Tapas Kumar Maji[a]*
Targeted synthesis of piezoresponsive small molecules and in-depth
understanding of their mechanism is of utmost importance for the
development of smart devices. Here, we report the synthesis,
structure and piezosensitivity of
a
bola-amphiphile 1,4-
(C5-PPB).
bis(pentyloxy)-2,5-bis(2-pyridineethynyl)-benzene
Depending on the rate of compression, two different phases in C5-
PPB can be generated. The ambient-pressure α-phase is stable up
to 0.8 GPa, beyond which it undergoes an isostructural
transformation to β-phase, accompanied by
a clearly visible
elongation of the crystal. This α-to-β phase transition requires that
the sample be compressed slowly. When quickly compressed,
phase α persists to about 1.5 GPa, beyond which its amorphization
starts, accompanied by the appearance of irregular grooves on the
largest faces. Mechanical pressure also affects the optical property
of C5-PPB, which shows reversible mechanochromism with a green
to cyan transformation in the emission, associated with a 15 nm shift
in the maxima. The conductivity of C5-PPB as a direct outcome of its
crystal packing has also been studied.
Scheme 1. Schematic representation of the piezo-response in C5-PPB.
remains a major challenge.[3,6] In many cases, piezochromic
molecules have appeared as isolated serendipitous occurrences
where the change in luminescence is irreversible and achieving
reversibility requires
a subtle balance between different
Development of purely organic conjugated oligomers that
are light, flexible and external-stimuli responsive is highly
desirable for multifarious applications in smart devices.[1]
Molecules that are capable of responding to external mechanical
forces[2] are vastly sought after for human-machine or robotic
interfaces, sensors, security inks, memory storage and
healthcare devices.[3] In condensed forms like crystals, liquid
crystals or micelles, the piezo-sensitivity of a particular material
depends extensively on its intermolecular interactions and
packing, governed by H-bonding, π-π, C—H···π or dipole-dipole
interactions.[4] When these interactions undergo alterations
under mechanical perturbation, the emission spectrum or
intensity may vary, which is regarded as mechanochromism or
piezochromism and finds numerous practical applications.[5]
However, the innate complexities of intermolecular forces and
structure factors render piezo-sensitivity of such systems
unpredictable and their rational design and synthesis still
supramolecular interactions.[7] The in-depth understanding of the
mechanism of piezosensitivity requires its correlation with the
structural changes occurring under pressure[8] which can be
characterized by studying the single-crystal structure under
hydrostatic compression. In this context, π-conjugated polymeric
systems, e.g., oligo-(p-phenylenevinylene) (OPV) and oligo-(p-
phenyleneethynylene) (OPE) derivatives[9] are ideal candidates.
Such molecules, comprising a rigid conjugated backbone along
with tunable side chains and functionalisable end terminals, offer
the perfect combination of weak and strong forces to create a
stimuli-responsive supramolecular architecture.[10] The rigid π-
conjugated backbone gives rise to charge migration, [11] intense
luminescence,[12] and may also lead to the formation of
conformational polymorphs via rotational freedom around the
single bonds connecting the conjugated units.[13] The
interference with the crystal packing caused by such molecular
movement forms the basis of stimuli-responsive luminescent
materials. [14] Similar systems synthesized by us previously have
shown a host of exciting stimuli-responsive properties like liquid
[a]
S. Bhattacharyya, Dr. S. Roy, Dr. D. Samanta, Prof. Dr. T. K. Maji
Chemistry and Physics of Materials Unit, School of Advanced
Materials (SAMat),
crystallinity, mechanochromism and photoconductivity as
a
direct outcome of their structures.[13] We predicted that a π-
conjugated system without any strong directional H-bonding
may manifest interesting piezosensitivity owing a synergistic
effect between the various weak van der Waal‘s forces. In this
work, we report the synthesis, structure and characterization of
Jawaharlal Nehru Centre for Advanced Scientific Research
Bangalore-560064, India.
E-mail: tmaji@jncasr.ac.in
Homepage: www.jncasr.ac.in/tmaji/
[b]
S. Sobczak, A. Półrolniczak, Prof. A. Katrusiak
Faculty of Chemistry,
such
a
bola-amphiphile
1,4-bis(pentyloxy)-2,5-bis(2-
Adam Mickiewicz University
pyridineethynyl)benzene (C5-PPB), which has been designed
with polar pyridine terminals and non-polar alkyl chains, thus
creating an interplay of weak interactions in the supramolecular
assembly (Scheme1). We have performed the in-depth analysis
of the compression rate-dependent polymorphism under
hydrostatic pressure and reversible mechanochromism upon
Umultowska 89b, 61-614 Poznań, Poland.
E-mail: katran@amu.edu.pl
Homepage: hpc.amu.edu.pl
#These authors contributed equally.
Supporting information and a movie for this article is given via a link
at the end of the document. Associated crystallographic information
has CCDC numbers 1871836, 1869429-1869438, 1894690
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irregular ―wrinkles‖ on the face; (ii) a transition front travelling
along the crystal plane followed by abrupt shape change. These
observations initially seemed to be inconsistent, but were
detected for the same crystal sample even on subsequent
experiments. The compression of phase α is monotonic till 0.8
GPa (Figure 2b). When the crystal is compressed rapidly from
0.8 to about 1.2 GPa, phase α is retained, and a visible
monotonic compression of the crystal is observed. When such a
crystal is further compressed slowly, it still resides in phase α.
However, when compressed to about 1.5 GPa, the irregular
‗wrinkles‘ appear on faces of the crystal, marking its
amorphization (Figure 2). If phase α is compressed beyond
0.8 GPa very slowly, a drastic discontinuous phase transition
occurs at 0.9 GPa,[24] associated with a giant negative-linear
Figure 1. (a) Photograph of a single crystal of C5-PPB. (b) Consecutive
molecules of C5-PPB arranged in ABA fashion in the a direction forming
extended π-column. (c) 2D sheets formed by C—H···N bonding between two
adjacent π-columns of C5-PPB. (d) Two different 2D sheets demarcated by
purple and green colours interact through weak van der Waal‘s forces.
grinding in C5-PPB.
C5-PPB has been synthesized by
a multistep synthesis
involving Sonogashira-Hagihara C-C coupling reaction from 1,4-
diethynyl-2,5-bis(pentyloxy)benzene.[24] The pure bulk of C5-
PPB, obtained after meticulous purification, was crystallized by
slow evaporation of ethanol from its concentrated solution.
Single-crystal X-ray diffraction (SCXRD) of the needle-like C5-
PPB crystal (Figure 1a) revealed that it crystallizes in triclinic Pī
space group, with two independent molecules located on
inversion centers arranged in a staggered fashion. The terminal
pyridines are twisted at a dihedral angle of 12° with respect to
the central phenyl ring. This ambient phase is regarded as the α-
phase. In the crystal structure of phase α, the OPE back bone of
one molecule overlaps with the alkyl chain of another along the
crystallographic a direction. Further, in the a direction, the
central phenyl rings of adjacent molecules interact via a weak
parallel offset π-π stacking interaction with a distance of 4.1 Å.
[4d,e]
Thus the molecules arranged in an ABA fashion form 1D
[24]
chain with an extended π-column (Figure 1b).
Along the
crystallographic b direction, two such 1D chains communicate
via C—H···N (C···N distance is 3.545 Å; ∠C—H···N angle is
156.5°) interaction between the N of one molecule and the
pyridinic β-H of its adjacent one to form a 2D network along the
ab plane (Figure 1c). These 2D arrays interact with each other
by weak van der Waals‘ forces along the crystallographic a
direction (Figure 1d). In addition, multiple C—H···π interactions
also exist between the terminal phenyl rings and the alkyl C-H
bonds of two adjacent molecules (C—H···π distances are
between 2.861-2.967 Å; ∠C—H•••π angles are in the range of
148.08-159.7°).[4f, 24]
We envisaged such a system to be piezo-sensitive owing
to the absence of any rigid directional interactions between the
Figure 2. (a) Phase diagram of C5-PPB compressed in three different
temperatures. Blue and pink colors mark phase stability regions and the
orange stripes trace amorphous region for over-compressed phase α. Squares
indicate points of the X-ray diffraction measurements and circles mark visual
observations of the crystal shape. (b) The sample C5-PPB single crystal (left)
first compressed rapidly (bottom) to 1.5 GPa, when the wrinkles mark the
onset of amorphization, and then after releasing pressure it was (top)
compressed again slowly to 0.9 GPa, where the transition to phase β starts
and transition fronts travel through the sample, till it all transforms to the end
(top right).(c) Projections of C5-PPB molecules and voids (accommodating
the probing sphere 0.8 Å in radius) in phases α and β along [100].
individual molecules and investigated the crystals under a high
[14]
hydrostatic pressure in a diamond anvil cell (DAC).
Single-
crystal of C5-PPB was compressed both rapidly and slowly in
the DAC and observed to undergo drastic visible changes, which
were also monitored by SCXRD. During compression, the
following two different sets of effects were visually observed: (i)
strong monotonic compression followed by the appearance of
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strain, visibly elongating the crystals in one direction and
(Figure 2c). It appears that such drastic conformational changes
correlated between neighboring molecules require time, and
upon fast compression, the conformers of phase α are ‗frozen‘
by rapidly increasing intermolecular interactions.
contracting them in another, forming phase β (Figure 2 and
[24]
movie).
This α-to-β transition does not change the crystal
symmetry nor Wyckoff sites, so this is an isostructural phase
transition. The single crystal integrity is often another
characteristic of isostructural transitions.[15a] In this case, the
isostructural transition between ambient phase α and high-
pressure phase β is accompanied by a volume drop of 7% and
strong conformational changes of two independent molecules,
while the crystal symmetry of triclinic space group Pī (Z = 2) is
retained. At the transition, the unit-cell parameter a abruptly
expands by 20%, b shrinks by -20% and c by -10%.[24]
Hence the quick compression of phase α eventually leads
to random collapse of molecular stacks and subsequently to
crystal amorphization. The macroscopic effect of the wrinkles on
the crystal faces is a direct effect of the molecular stacks
collapsing in groups in different directions, like book-shelves
falling incoherently in a library room. In literature, there are
numerous examples of the kinetic effects of the compression of
liquids and crystals, as well as of so-called flash cooling.[17]
However, C5-PPB is different because its kinetic path leads to
crystal amorphization connected with a massive collapse of the
voids in the crystal structure. Hence, it can amorphize when
phase α is over-pressurized quickly, which is manifested by the
―wrinkling‖ of the sample faces. These macroscopically visible
distortions of the crystal shape distinguishes C5-PPB from
regular crystalline phase transitions that show parallel lines
running exactly along the crystallographic planes on the faces of
the sample.[18] The significantly irregular ―wrinkling‖ is aligned
Characteristically,
isostructural
phase
transitions
are
discontinuous (of the 1st order according to Ehrenfest‘s
classification) and are associated with a volume drop in
compressed crystals along with a hysteresis.[15] These general
features are consistent with our observations of the sharp
transition between phases
α
and β. The process of
amorphization is generally diffused[16] and accordingly, the
amorphization of phase α proceeds over the range of pressure
from about 1.35 to 1.95 GPa at room temperature (Figure 2a). At
higher temperature the amorphization range is shifted toward
higher pressure, opposite to the boundary between phases α
and β. The π-π interaction between the central phenyl rings in
two adjacent molecules disappears as the distance between
them increases from 4.1 Å in α-phase at ambient pressure to 4.9
Å at 1.7 GPa. Moreover the molecular arrangements also vary
drastically.[24] At 1.51 GPa, the distance between the central
aromatic rings of neighboring molecules in phase α is reduced
by 0.275 Å in phase β, along with the elongation of the two n-
pentoxy chains, which explains the strong abrupt elongation of
the crystal along direction a (Figure S7). In phase β the Wyckoff
positions of molecules and their arrangement are retained,
however the conformation of independent molecules changes
significantly (Figures 1 and 2c). The torsion angles of pentyloxy
chains change up to ~ 160° (Figure S9), the terminal pyridines
with respect to the central benzene rings rotate only slightly, but
the rigid ethynyl bridge bends in the β phase and the curvature
increases with the increasing pressure. Thus two different
transformations of the C5-PPB crystal can be described as: (i)
the kinetic compression leading to ‗frowning‘ amorphous phase;
and (ii) the thermodynamic compression, leading to phase β
which is stable till at least 4.0 GPa. However, the β phase can
be circumvented, by compressing the crystal starting from 0.8
GPa quickly, at an estimated rate higher than 0.1 GPa∙s-1. The
crystal rippling marks the start of gradual amorphization. At
about 1.9 GPa the sample faces ‗frown‘ with approximately
parallel ‗wrinkles‘, marking the collapsed regions in the sample
(Figure 2b) and at this pressure no Bragg reflections can be
detected, indicating the full amorphization.
along one direction on the sample, which resembles
a
corrugated foil. The direction of ―wrinkles‖ is determined by initial
structural collapse and the corrugation of the structure (Figure 2
and Supporting Movie). However, the ―wrinkles‖ are irregular in
direction and depth and their direction changes occur
monotonically without sharp turns (characteristic for crystals). It
can be noted that in the crystal undergoing the amorphization, a
subtle pattern of lines appear in the largest crystal face (see the
photograph at 1.35 GPa in Figure 2a). It is thus plausible, that a
subtle
isostructural
phase
transition
precedes
the
amorphization.[19] The strong macroscopic effects in C5-PPB are
spectacular for both the slow and fast modes of compression
and additionally for the spectroscopic reasons. In these respects
the strong transformations of C5-PPB can be listed among other
macroscopic phenomena observed in crystals (although their
structural background can be very different), like color
changes,[5d-i] crystal jumping,[20] bending,[21] twisting,[22] etc.[23]
Upon observing the piezosensitivity of C5-PPB single crystals,
we were interested in observing the optical response of the
compound to small anisotropic pressures for practical
application. OPE systems are well known for their luminescent
behaviour,1a and C5-PPB is no different. Molecularly dissolved
We established that at increased temperature, the critical
pressure of the α-to-β transition is slightly decreased, but that of
amorphization is somewhat increased, as mapped in the phase
diagram with superimposed effects of both kinetic and
thermodynamic compression (Figure 2a). At ambient conditions
the crystal structure contains large voids (Figure 2c). They are
too small to accommodate guest molecules, but are essential for
inherent crystal properties, as evident from the β phase, where
the molecules alter their conformation to fill up the void space
Figure 3. (a) Photographs of C5-PPB sample under UV lamp before and after
grinding. (b) Emission spectra of C5-PPB before and after grinding. (c) PXRD
patterns of C5-PPB before and after grinding.
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methanolic solution of C5-PPB shows two peaks in the
absorption spectrum with λmax at 310 nm and 375 nm.[24] It shows
a wide emission band, ranging from 400 to 550 nm, with a
maximum at 442 nm (Figure S3b) However, in the solid state,
C5-PPB molecules remain in the aggregated state, showing a
red-shifted wide absorption band showing a typical vibronic
feature from 350 nm (Figure S3c) and emission maximum at
507nm (ex 350 nm). Mechanical grinding of the single crystals
of C5-PPB with a mortar and pestle for ~30 min changes the
emission from fluorescent green to cyan (Figure 3a). This
corresponds to a ~15 nm blue shift in the emission maximum
and λmax shifts to 492 nm (Figure 3b). This blue shifted emission
can be attributed to the breaking of weak supramolecular forces
in the dense crystal state of C5-PPB. As a rare instance of
reversible mechanochromism, the grounded sample on being
left undisturbed for ~8 hrs reverts its emission to its original
green spectrum, which is reflected by its emission spectrum
overlapping with that of the single crystalline form. The weak
supramolecular interactions reorient and re-establish themselves
over time, thereby reverting the original green emission. This is
also reinforced by the distinctly different powder X-ray diffraction
(PXRD) patterns of C5-PPB before and after grinding, implying
structural reorganization Figure 3c). Indexing the peaks reveal
that the first peak at 2θ = 6° corresponding to (001) plane, shifts
to 2θ = 5.7° after grinding. The (001) plane is the molecular ab
plane that lies in between the 2D networks formed by CH···N
interaction between the π-columns. The appearance of this peak
at a lower angle implies an increase in the distance between the
π-π interaction. Thus in case of both mechanical anisotropic and
high isotropic pressure, the π-π interaction is disrupted.
For use in practical applications, apart from piezosensitivity,
inherent conductivity is also an important property. The
conductivity of C5-PPB was measured across the needle
shaped single crystal both in the longitudinal as well as the
lateral directions. The measured conductivity in the longitudinal
direction is 1.75 x 10-7 S·cm-1, whereas that in the lateral
direction is 3.31 x 10-9 S·cm-1 (Figure S10ab). This stark
difference can be explained simply by looking into the structure
where the (100) plane is perpendicular to the long axis of the
crystal, while (001) and (011) planes are perpendicular to width
and breadth. From the SCXRD analysis, along the (100) plane,
the parallel displaced π-π stacking is present and hence along
the longitudinal direction, facile through space charge transfer
yields a high value of conductivity. However, along the width or
thickness either the weak CH···N interaction or weak van der
Waals interaction is present, (Figure S10cd), which is ineffective
for conductivity.
In conclusion, C5-PPB is an intriguing molecular system
with an interesting supramolecular architecture which shows
unusual compression-rate dependant piezo-sensitive behaviour.
The two different phenomena upon compressing the crystal are
firstly, the kinetic transformation of the crystal into amorphous
phase upon rapid compression and secondly the thermodynamic
transformation of the crystal into an isostructural phase upon
slow compression, are observed. Such in-depth study on the
structural changes occurring in a piezo-responsive organic
molecule is rare. Reversible mechanochromism coupled with
conductivity in this piezo-sensitive molecule makes it a potential
candidate for application in smart devices. Proper integration of
this molecule in devices can open a world of possibilities which
is currently being investigated in our lab.
2D networks in the
c direction. The peak at 2θ = 9°
corresponding to (011) plane is significantly diminished after
grinding. The (011) plane contains the extended π -column of the
structure (Figure 6d) and significant decrease in its intensity
indicates towards the increase in the distance between the π-
stacked molecules. The PXRD collected after 24 hrs of grinding
is almost same as the pristine compound.
Acknowledgements
In order to get a deeper insight into the structural changes
associated with the mechanochromic behaviour, time-dependent
density functional theory (TD-DFT) computations were
performed at CAM-B3LYP/6-31+G* level, on three different
model systems (models 1−3, Figure S6) which account for the
weak π-π and CH···N interactions. Model 1 illustrates a single
molecule, model 2 shows π stacked dimer, and model 3
SB is grateful to Mr. Saurav Islam for help with conductivity
studies. SB acknowledges INSPIRE fellowship, DST, Govt. Of
India for Fellowship. TKM is grateful to the Department of
Science and Technology (DST, Project No. MR-2015/001019
and Project No.TRC-DST/C.14.10/16-2724, JNCASR), Govt. of
India and JNCASR for financial support. SB and TKM are
grateful to Sheikh Saqr Laboratory, JNCASR for SCXRD facility.
SS, AP and AK are grateful to the Polish National Science
Centre (grant OPUS 10 No. UMO-2015/19/B/ST5/00262), SS to
considers CH···N interaction. Notably, Model
1
showed
absorption maximum at 342 nm (f = 1.2, HOMO → LUMO)
which shows an 8 nm blue shift from the absorption maximum of
Model 2 (λmax = 350 nm, f = 0.69, HOMO → LUMO + 1) (Figure
S5-S6). In contrast, Model 1 shows a 4 nm red shift in the
absorption maximum from Model 3 (λmax = 338 nm, f = 1.2,
HOMO → LUMO). Since experimentally, we observed slight
blue-shift in excitation spectra post grinding, it is a clear
indication towards the breaking of π-π stacking. Utilizing the
above transitions, emission wavelengths were calculated to be
389 nm and 397 nm, for model 1 and 2, respectively, implying
an 8 nm blue-shift upon complete removal of π-π stacking which
is in agreement with experimental findings. We have also
observed in the SCXRD structure obtained at 1.7 GPa that the
distance between the central phenyl rings of two adjacent
molecules increases to almost ~4.9 Å, thereby diminishing the
grant
POWR.03.02.00-00-I023/17
and
AP
to
grant
POWR.03.02.00-00-I026/16 co-financed by the EU European
Social Fund under the Operational Program Knowledge
Education Development.
Keywords: piezosensitive • reversible mechanochromism •
bola-amphiphile •
1.
(a) R. Thomas, S. Varghese, G. U. Kulkarni, J. Mater. Chem. 2009, 19 ,
4401-4406; (b) A. R. Ramesh, K. G. Thomas, Chem. Commun. 2010,
46, 3457-3459; (c) H.-Y. He, Y.-L. Zhou, Y. Hong, L.-G. Zhu, J. Mol.
Struct. 2005, 737 (2), 97-101.
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2.
(a) X. Yan, F. Wang, B. Zheng, F. Huang, Chem. Soc. Rev. 2012, 41,
6042-6065. (b) Minkov, V. S.; Goryainov, S. V; Boldyreva, E. V; Görbitz,
C. H. J. Raman Spectrosc. 2010, 41 (12), 1748–1758. (c) S. A.
Moggach, C. H. Görbitz, J. E. Warren, CrystEngComm 2010, 12 (8),
2322. (d) Pravica, M.; Yulga, B.; Tkachev, S.; Liu, Z. J. Phys. Chem. A
2009, 113 (32), 9133–9137. (e) Y. Wang, Z. Zhou, T. Wen, Y. Zhou, N.
Li, F. Han, Y. Xiao, P. Chow, J. Sun, M. Pravica, A. L. Cornelius, W.
Yang, Y. Zhao, J. Am. Chem. Soc. 2016, 138 (48), 15751–15757.
V. Lebedev, E. Laukhina, E. Moreno-Calvo, C. Rovira, V. Laukhin, I.
Ivanov, S. M. Dolotov, V. F. Traven, V. V. Chernyshev, J. Veciana, J.
Mater. Chem. C 2014, 2, 139-146.
Cryst. Growth Des. 2013, 13, 4648-4654 (d) M. Fisch, A. Lanza, E.
Boldyreva, P. Macchi, N. Casati, J. Phys. Chem. C 2015, 119, 18611–
18617. (e) B. A. Zakharov, N. A. Tumanov, E. V. Boldyreva,
CrystEngComm 2015, 17, 2074–2079. (f) A. Y. Fedorov, D. A. Rychkov,
E. A. Losev, B. A. Zakharov, J. Stare, E. V. Boldyreva, CrystEngComm
2017, 19, 2243–2252. (g) G. Resnati, E. Boldyreva, P. Bombicz, M.
Kawano, IUCrJ 2015, 2, 675–690. (h) S. Sobczak, A. Katrusiak, J. Phys.
Chem. C 2017, 121, 2539–2545. (i) B. A. Zakharov, E. V. Boldyreva,
CrystEngComm 2018, 10–22.
3.
4.
18.
(a) A. Katrusiak, Acta Cryst. B 1990, 46, 246–256. (b) S. V. Goryainov,
E. N. Kolesnik, E. V. Boldyreva, Phys. B Condens. Matter 2005, 357,
340–347. (c) W. Cai, A. Katrusiak, CrystEngComm 2012, 14, 4420–
4424. (d) E. Patyk, J. Skumiel, M. Podsiadło, A. Katrusiak, Angew.
Chemie - Int. Ed. 2012, 51, 2146–2150. (e) E. A. Kapustin, V. S.
Minkov, E. V. Boldyreva, Acta Crystallogr. Sect. B Struct. Sci. Cryst.
Eng. Mater. 2014, 70, 517–532. (f) B. A. Zakharov, E. V. Boldyreva, J.
Mol. Struct. 2014, 1078, 151–157. (g) S. Ghosh, M. K. Mishra, S. B.
Kadambi, U. Ramamurty, G. R. Desiraju, Angew. Chem. 2015, 127,
2712-2716. (h) A. A. Matvienko, D. V. Maslennikov, B. A. Zakharov, A.
A. Sidelnikov, S. A. Chizhik, E. V. Boldyreva, IUCrJ 2017, 4, 588–597
(a) M. Szafrański, A. Katrusiak, J. Phys. Chem. Lett. 2017, 8, 2496–
2506. (b) M. Szafrański, A. Katrusiak, J. Phys. Chem. Lett. 2016, 7,
3458–3466.
(a) C. Gu, N. Huang, Y. Chen, L. Qin, H. Xu, S. Zhang, F. Li, Y. Ma, D.
Jiang, Angew. Chem. Int. Ed. 2015, 54, 13594-13598. (b) J. Wu, Y.
Cheng, J. Lan, D. Wu, S. Qian, L. Yan, Z. He, X. Li, K. Wang, B. Zou, J.
You, J. Am. Chem. Soc. 2016, 138, 12803-12812. (d) C. R. Martinez,
B. L. Iverson
Chem. Sci. 2012, 3, 2191–2201.(e) M. Nishio,
CrystEngComm 2004, 6, 130-158. (f) M. Nishio, CrystEngComm, 2004,
6, 130-158.
5.
(a) S. Yagai, T. Seki, H. Aonuma, K. Kawaguchi, T. Karatsu, T. Okura,
A. Sakon, H. Uekusa, H. Ito, Chem. Mater. 2016, 28, 234-241; (b) P.
Xue, J. Ding, P. Wang, R. Lu, J. Mater. Chem. C 2016, 4, 6688-6706.
(c) Feng, C.; Wang, K.; Xu, Y.; Liu, L.; Zou, B.; Lu, P. Chem. Commun.
2016, 52 (19), 3836–3839. (d) Jaffe, A.; Lin, Y.; Mao, W. L.;
Karunadasa, H. I. J. Am. Chem. Soc. 2015, 137, 1673−1678. (e) Wang,
L.; Wang, K.; Zou, B. J. Phys. Chem. Lett. 2016, 7, 2556−2562. (f)
Gupta, S.; Pandey, T.; Singh, A. K. Inorg. Chem. 2016, 55, 6817−6824
(g) M. Andrzejewski, A. Katrusiak, J. Phys. Chem. Lett. 2017, 8, 929–
935. (h) M. Andrzejewski, A. Katrusiak, J. Phys. Chem. Lett. 2017, 8,
279–284. (i) M. Andrzejewski, N. Casati, A. Katrusiak, Dalt. Trans. 2017,
2, 14795–14803.
19.
20.
(a) J. Ridout, L. S. Price, J. A. K. Howard, M. R. Probert, Cryst. Growth
Des. 2014, 14, 3384-3391. (b) Bernstein, J. Polymorphism in Molecular
Crystals; Oxford University Press: Oxford, U.K., 2002. (c) Steiner, T.;
Hinrichs, W.;Saenger, W.; Gigg, R. Acta Crystallogr., Sect. B: Struct.
Sci. 1993, B49, 708–718. (d) Crottaz, O.; Kubel, F.; Schmid, H. J. Mater.
Chem. 1997,7, 143–146. (e) Etter, M. C.; Siedle, A. R. J. Am. Chem.
Soc. 1983,105, 641–643. (f) Ding, J.; Herbst, R.; Praefcke, K.; Kohne,
B.; Saenger, W. A. Acta Crystallogr., Sect. B: Struct. Sci. 1991, B47,
739–742. (g) Zamir, S.; Bernshtein, J.; Greenwood, D. J. Mol. Cryst. Liq.
Cryst. 1994, 242, 193–200. (h) Fernandes, M. A.; Levendis, D. C.;
Schoening, F. R. L. Acta Crystallogr., Sect. B: Struct. Sci. 2004, B60,
300–314.(i) Lieberman, H. F.; Davey, R. J.; Newsham, D. M. T. Chem.
Mater. 2000,12, 490–494. (j) Skoko, Z.; Zamir, S.; Naumov, P.;
Bernshtein, J. J. Am. Chem. Soc. 2010,132, 14191–14202. (k) Kaftory,
M.; Botoshansky, M.; Kapon, M.; Shteiman, V. Acta Crystallogr., Sect.
B: Struct. Sci. 2001, B57, 791–799. (l) Gigg, J.; Gigg, R.; Payne, S.;
Conant, R. J. Chem. Soc. Perkin Trans. I 1987, 2411–2414.
6.
7.
Y. Jiang, Mater. Sci.Engg: C 2014, 45, 682-689.
(a) R. Misra, T. Jadhav, B. Dhokale, S. M. Mobin, Chem.Commun.2014,
50, 9076-9078; (b) Y. Dong, J. Zhang, X. Tan, L. Wang, J. Chen, B. Li,
L. Ye, B. Xu, B. Zou, W. Tian, J. Mater. Chem. C 2013, 1, 7554-7559;
(c) P. S. Hariharan, N. S. Venkataramanan, D. Moon, S. P. Anthony, J.
Phys. Chem. C 2015, 119, 9460-9469.
8.
S. Ghosh, M. K. Mishra, S. Ganguly, G. R. Desiraju, J. Am. Chem. Soc.
2015, 137, 9912-9921.
9.
Bunz, U. H. F., Chem. Rev. 2000, 100 (4), 1605-1644.
10.
(a) S. Roy, V. M. Suresh, T. K. Maji, Chem. Sci.2016, 7, 2251-2256;
(b) H. Li, D. R. Powell, R. K. Hayashi, R. West, Macromolecules 1998,
31, 52-58.
21.
(a) C. M. Reddy, R. C. Gundakaram, S. Basavoju, M. T. Kirchner, K. A.
Padmanabhan, G. R. Desiraju, Chem. Commun., 2005, 3945; (b) Ž.
Skoko, S. Zamir, P. Naumov, J. Bernstein, J. Am. Chem. Soc. 2010,
132, 14191-14202; (c) P. Naumov, S. C. Sahoo, B.A. Zakharov,E. V.
Boldyreva, Angew. Chem. Int. Ed. 2013, 52, 9990-9995; (d) M. Lusi, J.
Bernstein, Chem. Commun. 2013, 49, 9293-9295. (e) O. S. Bushuyev,
T. C. Corkery, C. J. Barrett and T. Friščić , Chem.Sci., 2014, 5, 3158; (f)
O. S. Bushuyev, A. Tomberg, T. Friščić, C. J. Barrett, J. Am. Chem.
Soc., 2013, 135, 12556. (g) S. Ghosh, M. K. Mishra,S. B. Kadambi, U.
Ramamurty, G. R. Desiraju, Angew. Chem., Int. Ed., 2015, 54, 2674;
(h) M. K. Panda, S. Ghosh, N. Yasuda, T. Moriwaki, G. D. Mukherjee, C.
M. Reddi and P. Naumov, Nat. Chem., 2015, 7, 65. (i) O. S. Bushuyev,
A. Tomberg, J. R. Vinden, N. Moitessier, C. J. Barrett, T. Friščić, Chem.
Commun. 2016, 52, 2103–2106.
11.
12.
V. K. Praveen, C. Ranjith, E. Bandini, A. Ajayaghosh, N. Armaroli,
Chem. Soc. Rev. 2014, 43, 4222-4242.
T. M. Fasina, J. C. Collings, J. M. Burke, A. S. Batsanov, R. M. Ward,
D. Albesa-Jove, L. Porres, A. Beeby, J. A. K. Howard, A. J. Scott, W.
Clegg, S. W. Watt, C. Viney, T. B. Marder, J. Mater. Chem. 2005, 15,
690-697.
13.
(a) S. Roy, A. Hazra, A. Bandyopadhyay, D. Raut, P. L. Madhuri, D. S.
S. Rao, U. Ramamurty, S. K. Pati, S. Krishna Prasad, T. K. Maji, J.
Phys. Chem. Lett. 2016, 7, 4086-4092. (b) S. Roy, M. Das, A.
Bandyopadhyay, S. K. Pati, P. P. Ray, T. K. Maji, J. Phys. Chem. C,
2017, 21, 23803-23810. (c) S. Roy, D. Samanta, S. Bhattacharyya, P.
Kumar, A. Hazra, T. K. Maji, J. Phys. Chem. C, 2018,122, 21598-21606.
L. Merrill, W. A. Bassett, Rev. Sci. Instrum. 1974, 45, 290–294.
(a) V. E. Schneider, E. E. Tornau, Phys. Status Solidi 1982, 111, 565–
574. (b) G. Jaeger, Arch. Hist. Exact Sci. 1998, 53, 51–81.(c) P.
Borrmann, O. Mülken, J. Harting, Phys. Rev. Lett. 2000, 84, 3511–3514.
(a) J. Koike, Phys. Rev. B 1993, 47, 7700–7704. (b) O. Mishima,
Nature 1996, 384, 546–549. (c) R. J. Hemley, A. P. Jephcoat, H. K.
Mao, L. C. Ming, M. H. Manghnani, Nature 1988, 334, 52–54. (d) E. Ma,
Scr. Mater. 2003, 49, 941–946.
14.
15.
22.
(a) S. Kobatake, S. Takami, H. Muto, T. Ishikawa, M. Irie, Nature
2007,446, 778 – 781. (b) K. Uchida, S. Sukata, Y. Matsuzawa, M.
Akazawa, J. J. D. de Jong, N. Katsonis, Y. Kojima, S. Nakamura, J.
Areephong, A. Meetsma, B. L. Feringa, Chem. Commun. 2008, 326 –
328. (c) M. Morimoto, M. Irie, J. Am. Chem. Soc. 2010, 132, 14172 –
14178. (d) F. Terao, M. Morimoto, M. Irie, Angew. Chem. 2012, 124,
925 –928; Angew. Chem. Int. Ed. 2012, 51, 901 – 904. (e) S. Kobatake,
H. Hasegawa, K. Miyamura, Cryst. Growth Des. 2011,11, 1223 – 1229.
(f) O. S. Bushuyev, A. Tomberg, J. R. Vinden, N. Moitessier, C. J.
Barrett, T. Friščić, Chem. Commun. 2016, 52, 2103–2106. (g) A. K.
Saini, K. Natarajan, S. M. Mobin, Chem.Commun.2017, 53, 9870-9873;
(h) S. Hayashi, A. Asano, N. Kamiya, Y. Yokomori, T. Maeda, T.
16.
17
(a) E. Boldyreva, Cryst. Growth Des. 2007, 7, 1662–1668. (b) N. A.
Tumanov, E. V. Boldyreva, B. A. Kolesov, A. V. Kurnosov, R. Quesada
Cabrera, Acta Crystallogr. Sect. B Struct. Sci. 2010, 66, 458–471. (c) K.
Adrjanowicz, A. Grzybowski, K. Grzybowska, J. Pionteck, M. Paluch,
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Koizumi, Sci. Rep. 2017, 7, 9453; (i) S. Hayashi, T. Koizumi, N. Kamiya,
Cryst. Growth Des. 2017, 17, 6158-6162.
23.
(a) X. Cui, A. L. Rohl, A. Shtukenberg, B. Kahr, J. Am. Chem. Soc.
2013, 135, 3395-3398; (b) D. Kitagawa, H. Tsujioka, F. Tong, X. Dong,
C. J. Bardeen, S. Kobatake, J. Am. Chem. Soc. 2018, 140, 4208-4212.
(c) Naumov, P.; Chizhik, S.; Panda, M. K.; Nath, N. K.; Boldyreva, E.
Chem. Rev. 2015, 115 (22), 12440–12490. (d) Wang, H.; Chen, P.; Wu,
Z.; Zhao, J.; Sun, J.; Lu, R. Angew. Chemie Int. Ed. 2017, 56 (32),
9463–9467.
24.
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Entry for the Table of Contents
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S. Bhattacharyya,
S. Sobczak,
A. Półrolniczak,S. Roy,
D. Samanta,A.
Katrusiak*, T. K. Maji*
Page No. – Page No.
A Piezosensitive Bola-amphiphile: Although piezosensitive compounds are of utmost importance for specific applications, the
understanding of their mechanism still eludes us. We have strategically synthesized a bola-amphiphile C5-PPB with weak
interactions that can respond to pressure. Moreover, it shows unique compression-dependant phase change and the different
phases have been discerned, providing insights into the piezo-response mechanism. Under mechanical pressure, C5-PPB also
reversible mechanochromism, with its emission changing from green to cyan and back, with a 15nm shift in the emission maximum.
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