Carboxylate-Driven Supramolecular Assemblies of Protonated meso-Aryl-Substituted Dipyrrolylpyrazoles

Article abstract of DOI:10.1002/chem.201500681

Dipyrrolylpyrazole (dpp) derivatives possessing an aryl ring at the pyrazole 4-position were synthesized. Upon protonation, modified dpp derivatives formed a variety of assembled structures through complexation with carboxylates, as observed by single-cry

Full text of DOI:10.1002/chem.201500681

DOI: 10.1002/chem.201500681
Full Paper
&
p-Conjugated Molecules |Hot Paper|
Carboxylate-Driven Supramolecular Assemblies of Protonated
meso-Aryl-Substituted Dipyrrolylpyrazoles
[a]
[a]
[a]
[b, c]
Hiromitsu Maeda,* Kengo Chigusa, Ryohei Yamakado, Tsuneaki Sakurai,
and
[b, c]
Shu Seki
Abstract: Dipyrrolylpyrazole (dpp) derivatives possessing an
aryl ring at the pyrazole 4-position were synthesized. Upon
protonation, modified dpp derivatives formed a variety of
assembled structures through complexation with carboxy-
lates, as observed by single-crystal X-ray and synchrotron
XRD analyses. In particular, the complexation of protonated
dpp species possessing long alkyl chains with dicarboxylates
resulted in highly ordered assembled structures, the packing
modes of which as lamellar structures were controlled by
the lengths of the spacer units between two carboxylate
moieties. The charge-carrier transporting properties of the
solid materials were also controlled by bound anions, includ-
ing dicarboxylates.
Introduction
The location of p-electronic units in molecular assemblies de-
termines their electronic properties because interactions be-
tween the constituting p systems control the mobility of
charge carriers. A variety of noncovalent interactions, such as
hydrogen-bonding and van der Waals interactions, often at the
peripheral substituents, are effective for the arrangement of p-
electronic units. In contrast to electronically neutral molecules,
charged p-electronic species can use electrostatic force for as-
sembly, and their arrangement is essential for the fabrication
[
1,2]
of functional electronic materials.
In particular, electron-defi-
cient cationic species behave as effective electron carriers for
organic semiconductor devices owing to the formation of
stacking structures.
Figure 1. a) The dpp derivatives (left) and their [2+2]-type complexes with
As a promising p-electronic cation, the protonated form of
À
CF
3
CO
2
in the protonated forms (right). TFA=trifluoroacetic acid. b) Synthe-
[
3,4]
3
,5-dipyrrolylpyrazole (dpp; for example, 1)
affords a [2+2]-
sis of 3a,b from the corresponding 2-arylmalonic acids.
À
type planar complex with trifluoroacetate (CF CO ; Fig-
3
2
[5]
ure 1a). Such a [2+2]-type ion-pairing complex is an attrac-
tive scaffold for supramolecular assemblies and enables the
formation of highly ordered organized structures by peripheral
modifications of the dpp unit. The introduction of aryl moieties
at the a positions of pyrrole, as seen in 2a,b (Figure 1a), re-
sults in the formation of a 2D pattern at the solution–substrate
(highly ordered pyrolytic graphite (HOPG)) interface, supra-
molecular gels, and mesophases based on [2+2]-type com-
À [4b,6]
plexes with CF CO2
.
Although a-aryl moieties were useful
3
for installing various substituents on dpp, they interfered with
À
[
a] Prof. H. Maeda, K. Chigusa, Dr. R. Yamakado
College of Pharmaceutical Sciences, Ritsumeikan University
Kusatsu 525-8577 (Japan)
stable complexation with CF CO2 due to steric effects. There-
3
fore, the formation of stable assembled structures comprising
protonated dpp compounds and carboxylates requires the
design and synthesis of dpp derivatives that possess an aryl
substituent at a more suitable position. Potentially suitable
motifs are the dpp derivatives with an aryl moiety at the pyra-
zole 4-position (meso position) because their protonated forms
can provide functional assembled structures upon combination
with a variety of carboxylate anions. Herein, we report on the
synthesis of meso-aryl dpp derivatives and their ion-pairing di-
mension-controlled assembling modes of which in the proton-
E-mail: maedahir@ph.ritsumei.ac.jp
[b] Dr. T. Sakurai, Prof. S. Seki
Department of Applied Chemistry, Graduate School of Engineering
Osaka University, Suita 565-0871 (Japan)
[
c] Dr. T. Sakurai, Prof. S. Seki
Department of Molecular Engineering
Graduate School of Engineering, Kyoto University
Kyoto 615-8510 (Japan)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201500681.
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ated forms were thoroughly examined by synchrotron XRD
analysis.
Results and Discussion
The dpp precursors, 2-aryl-substituted 1,3-dipyrrolyl-1,3-pro-
panediones 3a’,b’, were prepared by the treatment of 2-aryl-
malonic acids with thionyl chloride and subsequent reactions
[7]
with pyrrole in 27 and 29% yield (two steps), respectively.
The subsequent condensation reaction of 3a’,b’ with hydrazine
in acetic acid at reflux provided 3a,b in 19 and 58% yield, re-
spectively (Figure 1b). Currently, this procedure for 3a,b, which
includes the condensation of carbonyl and amino groups, is ef-
fective compared with cross-coupling. Structural elucidation of
1
3
a,b was carried out by using H NMR spectroscopy and
[
4]
MALDI-TOF MS. As seen in 1 and 2a,b, meso-aryl-substituted
a,b also showed singly pyrrole-inverted conformations with
3
intramolecular hydrogen bonding between pyrrole NH and
pyrazole N as stable optimized states (Figures S5 and S6 in the
[
8]
Supporting Information). The singly inverted conformation of
À1
3
a is more stable at 3.01 and 4.06 kcalmol than no inverted
and doubly inverted conformations, respectively, at B3LYP/6-
1G(d,p). In solution, the inverted pyrrole ring in 3a,b is not
3
fixed with NH tautomerism at the pyrazole N sites.
Compound 3b, which possesses long alkyl chains, formed
a lamellar structure with a layer distance of 5.73 nm in the
solid state, prepared from CH Cl /MeOH, as revealed by syn-
2
2
chrotron XRD analysis at RT (Figure 2a). The layer distance cor-
responded to the length of two molecules of 3b, which sug-
gested the formation of a dimeric structure of a singly pyrrole-
inverted conformation through hydrogen-bonding and dipole–
[8]
dipole interactions (Figure S7 in the Supporting Information).
Polarized optical microscopy (POM) of 3b revealed various tex-
tures upon cooling from an isotropic liquid (Iso), although dif-
ferential scanning calorimetry (DSC) showed transitions at 57
and 478C upon first and second heating, respectively, and at
418C upon cooling, but no peaks that suggested the existence
of mesophases (Figures S11 and S12 in the Supporting Infor-
mation). After thermal annealing in Iso, compound 3b exhibit-
ed a lamellar structure in the solid state with a layer distance
of 3.40 nm, which was probably due to the formation of an in-
terdigitating structure (Figure 2b). Annealing as a process to
form the solid in the absence of solvent would provide the
condensed short layer structure.
Figure 2. i) Synchrotron XRD patterns, ii) possible packing structures, and
iii) illustration of organized structures of 3b a) as a precipitate (from CH Cl /
2 2
MeOH) at 258C and b) as a sample at 258C upon first cooling. The diffraction
at 0.41 nm is derived from assembly of alkyl chains.
Compounds 3a,b were converted into their protonated
forms in solution upon the addition of TFA, as observed in the
UV/Vis absorption and fluorescence emission spectral changes
larger than those (1.2 and 8.18) in the [2+2]-type complex of
+
À [4a]
.
2
1·H ÀCF CO
The [2+2]-type complex formed a herring-
3
(Figures S8 and S9 in the Supporting Information). Protonation
bone-like packing structure with a dihedral angle of 100.08 for
at the pyrazole N site in the dpp derivatives requires fairly
strong acids, such as TFA. Compound 3a formed a [2+2]-type
complex with TFA in the solid state through NÀH···O hydrogen
bonding with N(ÀH)···O distances of 2.71 and 2.85 Š (Fig-
ure 3a). In the solid state, the dihedral angle between the dpp
pyrazole unit and meso-phenyl ring was estimated to be 63.08,
and the steric effect of the meso-phenyl ring resulted in distor-
tion of the planarity of the pyrrole rings, with dihedral angles
of 12.2 and 19.78 to the pyrazole unit. These distortions were
two dpp planes in neighboring columns, as observed in the
[4a]
TFA complex of 1. Furthermore, compound 3b also formed
+
À
a complex with TFA, 3b·H ÀCF CO , that could be purified
3
2
by recrystallization from octane. POM revealed a broken fan-
like texture from 698C to RT, whereas DSC results showed tran-
sitions only at 698C upon cooling and at 798C upon heating,
due to the absence of mesophases (Figures S11 and S12 in the
+
À
Supporting Information). The ion pair 3b·H ÀCF CO exhibit-
3
2
ed higher transition temperatures to and from the Iso by
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3
b due to more effective stacking as the assembled two units
+
À
of 3b·H are bridged by CF CO2 . It is notable that the proto-
3
nation of dpp derivatives and ion pairing with carboxylate can
control the stability of assembled structures. Synchrotron XRD
measurements of the solid sample from octane at RT revealed
a lamellar structure with a layer distance of 5.97 nm, which
was slightly larger than that of 3b, owing to complexation
with TFA (Figure 3b). After thermal annealing in Iso, the solid
sample also exhibited a similar lamellar structure with a layer
distance of 5.91 nm (Figure 3c). The fairly sharp diffractions of
the halo at around 0.4 nm at 608C and RT suggested the for-
mation of a rigid packing structure. The small difference in the
+
À
assembled structures of 3b·H ÀCF CO upon annealing is
3
2
also in contrast to that in 3b.
Protonated dpp is an effective building subunit for the fabri-
cation of highly organized structures, which are formed by
bridging between components that possess multiple carboxyl-
ate moieties. In fact, single-crystal X-ray analysis revealed the
+
assembly of parent dpp in the protonated form 1·H with
À
0
.5 equivalents of perfluorobutane dicarboxylate ((CF ) (CO ) ;
2
4
2
2
+
3
2À
CO as a [2+2]-type complex
Figure 3. a) Solid-state structure of 3a·H ÀCF
(
left) and packing side-view diagram (right). i) Synchrotron XRD patterns, ii)
possible packing structures, and iii) illustration of organized structures of
+
À
3
2
b·H ÀCF
3 2
CO as b) a precipitate (from octane) at 258C and c) a sample at
58C upon first cooling. The organized structures in part iii) of b) and c) are
the same and are ascribable to almost no change in assembled structures
upon annealing.
about 308C in comparison with 3b with transitions at 47 and
+
2À
+
Figure 4. Solid-state structures of a) (1·H )
2
À(CF
2
)
4
(CO
)
2
and b) (3a·H )
2
À
4
18C upon heating and cooling, respectively. This observation
À
(
CF
2
)
4
(CO
2
)
2
as i) hydrogen-bonding structures with a single dicarboxylate
(left: top view and right: side view) and ii) packing structures.
+
À
suggested a more stable assembly for 3b·H ÀCF CO than
3
2
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+
Figure 4a). In the solid state, protonated dpp 1·H formed
a herring-bone-like packing structure with a stacking p-plane
distance of 3.46 Š, based on 3D networks forming the three
hydrogen-bonding interactions between pyrrole/pyrazole-NH
and carboxylate oxygen atoms with N(ÀH)···O distances of
2
.60–2.86 Š. The less effective interaction with carboxylate was
observed for one of the pyrrole NH atoms. The observation of
by single-crystal X-ray analysis confirmed the expectation
1
that the protonated form of dpp 3a also formed supramolec-
ular polymers with dicarboxylates. Similar to the assembly of
+
À
+
(
1·H ) À(CF ) (CO ) , the combination of 3a·H
and
CF ) (CO ) led to a solid-state assembled structure, as re-
2
2 4
2
2
À
(
2
4
2
2
vealed by single-crystal X-ray analysis (Figure 4b). The intro-
+
duction of a phenyl moiety in 3a·H , with the dihedral angle
of 64.18 to the dpp pyrazole unit, induced a stacking p-plane
distance of 3.69 Š, which was slightly larger than that of (1·
+
À
+
H ) À(CF ) (CO ) . Distortions of pyrrole rings in (3a·H ) À
2
2 4
2
2
2
À
+
(
(
CF ) (CO ) of 9.0 and 15.88 are larger than those of (1·H ) À
2
4
2
2
2
À
CF ) (CO ) (5.3 and 5.88). The assembly was constructed by
2
4
2
2
interactions not only between pyrrole/pyrazole-NH and carbox-
ylate oxygen atoms, but also those between pyrrole CH and
pyrrole/phenyl p planes, leading to larger p-plane distances.
The solid-state structures were slightly different from regular
[2+2]-type binding mode with carboxylate units, probably due
to the preferred crystal-packing modes. However, the observa-
tions of the solid-state assembled structures consisting of di-
carboxylates were valuable for the further design and prepara-
tion of highly ordered structures through the introduction of
appropriate substituents to the dpp core unit.
The long alkyl chains in 3b can yield dimension-controlled
organized structures based on van der Waals interactions be-
tween alkyl units supporting the stacking structures of the p-
electronic moieties. Compound 3b yielded precipitates of ion-
pairing assemblies from octane after mixing with 0.5 equiva-
lents of (CF ) (CO H) (n=4 and 8) in 1,2-dimethoxyethane
2
n
2
2
(DME) and evaporation of the solvent, whereas it was difficult
to obtain purified assemblies with (CF ) (CO H) (n=6 and 10;
2
n
2
2
Figure S10 in the Supporting Information). DSC results for
+
À
(
3b·H ) À(CF ) (CO ) (n=4 and 8) revealed transitions to Iso
2
2 n
2
2
at 98 and 738C, respectively, which suggested the absence of
mesophases (Figure S11 in the Supporting Information). The
[9]
Figure 5. i) Synchrotron XRD patterns, ii) possible packing structures, and
+
À
+
À
2 4 2
iii) illustration of the organized structures of 3b·H as a) (CF ) (CO )2 and
+
transition temperature of (3b·H ) À(CF ) (CO ) is 208C higher
2
2 4
2
2
À
+
À
2
b) (CF ) (CO ) complexes (in a molar ratio of 2:1 for 3b·H and dicarboxy-
2 8 2 2
than that of 3b·H ÀCF CO (798C) probably because of the
3
lates) at 258C upon cooling from Iso.
formation of the more stable assembly by tight binding of ion-
pairing moieties through perfluoroalkyl spacer units. Synchro-
tron XRD at 258C revealed the formation of lamellar structures
+
with 3b·H or related carboxylate-binding structures with
+
À
in 3b·H as both (CF ) (CO ) (n=4 and 8) complexes in the
a repeat distance of 5.91 nm. On the other hand, the dicarbox-
2
n
2
2
À
solid state after melting to Iso (Figure 5 and Figure S13 in the
ylate (CF ) (CO ) has a longer perfluoroalkyl moiety and ena-
2
8
2
2
À
Supporting Information). The complex containing (CF ) (CO )
bles the formation of a lamellar structure upon supramolecular
2
4
2
2
+
exhibited a layer distance of 5.91 nm (Figure 5a), whereas the
polymerization with 3b·H by interdigitating into vacant areas
À
complex containing (CF ) (CO ) exhibited a layer distance of
between carboxylate complex units. Based on these results,
the perfluoroalkyl moieties are essential for constructing differ-
ent assembled structures in different forms. The complicated
2
8
2
2
3.70 nm (Figure 5b), which suggested that the difference in
the alkyl chain lengths of the dicarboxylate could influence the
+
À
[9]
organized structures formed by meso-modified dpp. Based on
thermal transition behavior of (3b·H ) À(CF ) (CO ) can be
2
2 8
2
2
[
8]
À
+
molecular modeling,
the dicarboxylate (CF ) (CO ) has
ascribable to less effective packing than that of (3b·H ) À
2
4
2
2
2
À
a short perfluoroalkyl chain, which may result in the formation
(CF ) (CO ) . Although the exact carboxylate binding mode
2
4
2
2
of a lamellar structure of [2+2]-type supramolecular polymers
cannot be elucidated by synchrotron XRD, the introduction of
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aliphatic chains induced ordered structures owing to interac-
tions between protonated 3b and dicarboxylates. Currently, it
is very challenging to reveal the assembling processes and
mechanisms because they include the formation of solid
states. On the other hand, the fairly disordered structures
formed upon combination of 3b with (CF ) (CO H) (n=6 and
ionic species. Further design and modification of dpp deriva-
tives, as well as the synthesis of other new p-electronic sys-
tems, are currently ongoing in our laboratory in an effort to
develop fascinating ion-based electronic materials.
2
n
2
2
1
0) could be attributed to the nonideal lengths between two Experimental Section
carboxylate moieties.
General procedures
The ion-pair-based assemblies of p-conjugated systems can
control not only their structural order, but also their charge-
carrier transporting properties. Flash-photolysis time-resolved
Starting materials were purchased from Wako Pure Chemical Indus-
tries Ltd., Nacalai Tesque Inc, and Sigma–Aldrich Co., and used
without further purification unless otherwise stated. UV/Vis spectra
were recorded on a Hitachi U-3500 spectrometer. Fluorescence
spectra were recorded on a Hitachi F-4500 fluorescence spectrom-
eter for ordinary solutions. NMR spectra used in the characteriza-
tion of products were recorded on a JEOL ECA-600 600 MHz spec-
trometer. All NMR spectra were referenced to residual solvent.
MALDI-TOF MS was recorded on a Shimadzu Axima-CFRplus spec-
trometer. Fourier transform ion cyclotron resonance mass spec-
trometry (FT-ICR-MS) was recorded on a Bruker solariX (Qh-FT-ICR-
MS) spectrometer and were carried out at the Joint Usage/Re-
search Center (JURC) at the Institute for Chemical Research (ICR),
Kyoto University. TLC analyses were carried out on aluminum
sheets coated with silica gel 60 (Merck 5554). Column chromatog-
raphy was performed on Sumitomo alumina KCG-1525, Wakogel C-
200, C-300, and Merck silica gel 60 and 60H.
[
10]
microwave conductivity (FP-TRMC) measurements were car-
ried out to investigate the effect of the ion-pair-based direc-
tional assembly on the photoconductivity (Figure S14 in the
Supporting Information). When photoexcited by a l=355 nm
+
À
+
laser pulse, thin films of 3b, 3b·H ÀCF CO , and (3b·H ) À
3
2
2
À
(
CF ) (CO ) (n=4 and 8) on quartz exhibited transient con-
2 n 2 2
ductivity (fÆm), in which f and Æm represent the yield of
charge-carrier generation and sum of the charge-carrier mobili-
ties, respectively. We found the conductivity maxima, (fSm)max,
À5
À5
À5
to be around 1.6”10 , 1.7”10 , 1.9”10 , and 2.2”
À5
2
À1 À1
+
À
+
1
0
cm V
s
for 3b, 3b·H ÀCF CO
,
and (3b·H ) À
3
2
2
À
(
(
CF ) (CO ) (n=4 and 8), respectively. The difference in
2 n 2 2
fSm)max between 3b alone and the ion-pairing forms was
small, probably because, upon dimerization, compound 3b
forms a mesoscopically ordered structure in its dimerized as-
sembly. However, slight but significant differences in the pho-
toconductivity were observed when coupled with dicarboxy-
lates in the protonated form. We consider that the dicarboxy-
lates are likely to promote supramolecular polymerization with
protonated dpp units and suppress their dynamic motions, re-
sulting in an advantage for the one-dimensional charge-carrier
2
-Phenyl-1,3-dipyrrol-2-yl-1,3-propanedione (3a’)
Thionyl chloride (4 mL) was added slowly to a flask containing 3a’’
(1.80 g, 10.0 mmol), and was stirred for 3 h at 508C. Excess thionyl
chloride was removed under vacuum for several hours to give 2-
phenylmalonyl chloride as a yellow oil, which was immediately
used in the next reaction without further purification. A solution of
pyrrole (2 mL, 30 mmol) in CH Cl (50 mL) was treated with 2-phe-
nylmalonyl chloride at 08C and stirred for 3 h. After the consump-
tion of the starting pyrrole was confirmed by TLC analysis, the mix-
ture was washed with a saturated aqueous solution of Na CO and
water, dried over anhydrous Na SO , and evaporated to dryness.
2 4
The residue was then purified by column chromatography on
a silica gel (eluent: 3% MeOH/CH Cl ) to give 3a’ (746 mg,
2
2
+
À
transporting event. In addition, ion pair (3b·H ) À(CF ) (CO ) ,
2
2 8
2
2
the assembled structure of which is less thermally stable, has
a slightly more effective pathway of charge carriers compared
2
3
+
À
with (3b·H ) À(CF ) (CO ) . The extremely long lifetime of the
2
2 4
2
2
free charge carriers in the conductivity transient over 200 ms
also supports the presence of a stable, isolated 1D pathway for
the charge carriers.
2
2
2
.68 mmol, 27%) as a yellow solid. R =0.37 (eluent: EtOAc/n-
f
1
hexane=1:1). H NMR (600 MHz, CDCl , 208C; the diketone is ob-
3
tained as a mixture of keto and enol tautomers in the ratio of
1
7
6
:0.17): keto form: d=9.34 (brs, 2H; NH), 7.54–7.28 (m, 5H; Ar-H),
.04–7.02 (m, 2H; pyrrole-H), 7.01–7.00 (m, 2H; pyrrole-H), 6.28–
.27 (m, 2H; pyrrole-H), 6.08 ppm (s, 1H; CH); enol form: d=18.57
Conclusion
We synthesized dpp derivatives that possessed an aryl ring at
the pyrazole 4-position. The modified dpp derivatives formed
a variety of assembled structures based on [2 ++ 2]-type com-
plexes upon combination with appropriate acids. In particular,
complexation of protonated dpp derivatives with dicarboxy-
lates resulted in highly ordered structures, the packing modes
of which, along with thermal transition behavior, were con-
trolled by the distances between two carboxylate moieties.
This modulation also resulted in control of the charge-carrier
transporting properties, as evidenced by electrodeless conduc-
tivity measurements. Planar ion-pairing complexes reported
herein would afford various highly ordered assembled struc-
tures based on the combination of ionic species. One of the
advantages in the ion-pairing assemblies is the control of pack-
ing structures and resulting properties by the constituting
(
(
s, 1H; OH), 9.34 (brs, 2H; NH), 7.50–7.28 (m, 5H; Ar-H), 6.90–6.89
m, 2H; pyrrole-H), 6.01–6.00 (m, 2H; pyrrole-H), 5.19–5.18 ppm (m,
+
2
H; pyrrole-H); MALDI-TOF-MS: m/z (%): 279.1 (100) [MÀH] .
4
-Phenyl-3,5-dipyrrol-2-ylpyrazole (3a)
[4]
Following a procedure reported in the literature, hydrazine mon-
ohydrate (300 mL, 6.17 mmol) was added to a solution of 3a’
(55.3 mg, 0.20 mmol) in AcOH (2 mL) and stirred at reflux for 21 h.
After monitoring the consumption of the starting diketone on TLC,
the solvent was removed and then the reaction mixture was puri-
fied by column chromatography on silica gel (eluent: 3% MeOH/
CH Cl ), followed by evaporation, and recrystallization from CH Cl /
n-hexane to give 3a (10.1 mg, 0.038 mmol, 19%) as a white solid.
R =0.14 (eluent: 3% MeOH/CH Cl ); H NMR (600 MHz, CDCl3,
2
2
2
2
1
f
2
2
208C; pyrazole NH cannot be observed at this temperature): d=
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8
2
.42 (brs, 2H; pyrrole-NH), 7.50–7.42 (m, 5H; Ar-H), 6.70–6.69 (m,
H; pyrrole-H), 6.14–6.13 ppm (m, 4H; pyrrole-H); UV/Vis (CH Cl ):
2-(3,4,5-Trihexadecyloxyphenyl)-1,3-dipyrrol-2-yl-1,3-pro-
panedione (3b’)
2
2
À4
À1
À1
lmax (e”10 )=277 nm (1.7m cm ); fluorescence (CH Cl ): l
2
2
em
À
Thionyl chloride (3 mL) was added slowly to a flask containing 3b’’
(l )=391 nm (277 nm); MALDI-TOF-MS: m/z (%): 273.9 (100) [M] .
ex
(571 mg, 0.63 mmol) and stirred for 1.5 h at 608C. Excess thionyl
chloride was removed under vacuum for 1 h to give 2-(3,4,5-trihex-
adecyloxyphenyl)malonyl chloride as a yellow solid, which was
used immediately in the next reaction without further purification.
1
,2,3-Trihexadecyloxy-5-iodobenzene
A solution of pyrrole (130 mL, 1.89 mmol) in CH Cl2 (12 mL) was
2
[11]
A mixture of 1,2,3-trihydroxy-5-iodobenzene (3.35 g, 13.3 mmol),
K2CO3 (12.9 g, 93.1 mmol), and 1-bromohexadecane (13.8 g,
treated with 2-(3,4,5-trihexadecyloxyphenyl)malonyl chloride at RT
and stirred for 30 min. After the consumption of the starting pyr-
role was confirmed by TLC analysis, the mixture was washed with
water and a saturated aqueous solution of NaCl, dried over anhy-
drous Na SO , and evaporated to dryness. The residue was then
4
5.2 mmol) in dry DMF (120 mL) was stirred at 808C for 3 d. After
cooling, the solvent was evaporated. The crude product was dis-
solved in CHCl , washed with water, dried over Na SO , and evapo-
3
2
4
2
4
rated to dryness. The residue was then purified by column chroma-
purified by flash column chromatography on silica gel (eluent:
tography on silica gel (Wakogel C-300; eluent CH Cl /n-hexane=
0.5% MeOH/CH Cl ) to give 3b’ (143 mg, 0.14 mmol, 22%) as
2
2
2
2
1
1
1
:4)
to
give
1,2,3-trihexadecyloxy-5-iodobenzene (11.1 g,
a yellow solid. R =0.24 (eluent: 0.5% MeOH/CH Cl ); H NMR
f
2
2
2.0 mmol, 90%) as a white solid. R =0.34 (eluent: CH Cl /n-
(600 MHz, CDCl , 208C): d=9.29 (brs, 2H; NH), 7.04–7.03 (m, 2H;
f
2
2
3
1
hexane=1:4); H NMR (600 MHz, CDCl , 208C): d=6.84 (s, 2H; Ar-
pyrrole-H), 7.00–6.98 (m, 2H; pyrrole-H), 6.66 (s, 2H; Ar-H), 6.28–
6.27 (m, 2H; pyrrole-H), 5.94 (s, 1H; CH), 3.97–3.89 (m, 6H;
OCH C H ), 1.78–1.68 (m, 6H; OCH CH C H ), 1.46–1.41 (m, 6H;
3
H), 3.91 (t, J=6.0 Hz, 4H; OCH ), 3.90 (t, J=6.6 Hz, 2H; OCH ),
2
2
1
1
.80–1.70 (m, 6H; OCH CH ), 1.46–1.43 (m, 6H; OC H CH ), 1.33–
2 2 2 4 2
2
15 31
2
2 14 29
.25 (m, 72H; OC H C H CH ), 0.89–0.87 ppm (m, 9H; OC H CH );
OC H CH C H ), 1.34–1.25 (m, 72H; OC H C H CH ), 0.89–
2 4 2 13 27 3 6 12 24 3
3
6
12 24
3
15 30
3
À
MALDI-TOF-MS: m/z (%): 924.1 (100) [MÀH] .
0.87 ppm (m, 9H; OC H CH ); MALDI-TOF-MS: m/z (%): 999.9
15 30 3
+
(
100) [M+H] .
4
-(3,4,5-Trihexadecyloxyphenyl)-3,5-dipyrrol-2-ylpyrazole
Di-tert-butyl 2-(3,4,5-trihexadecyloxyphenyl)malonate
(
3b)
[6]
Following a procedure reported in the literature, a Schlenk tube
[4]
Following a procedure reported in the literature, hydrazine mon-
ohydrate (240 mL, 4.94 mmol) was added to a solution of 3b’
containing [Pd (dba) ] (dba=dibenzylideneacetone; 91.6 mg,
2
3
0.10 mmol), P(tBu)3 (40.5 mg, 0.20 mmol), tBuOK (247 mg,
2.2 mmol), and 1,2,3-trihexadecyloxy-5-iodobenzene (1.85 g,
2.0 mmol) was flushed with nitrogen and charged with anhydrous
1,4-dioxane (5.0 mL) and di-tert-butyl malonate (493 mL, 2.2 mmol).
(56.8 mg, 0.057 mmol) in AcOH (1 mL), and stirred at reflux for
1
2 h. After monitoring the consumption of the starting diketone
by TLC, the solvent was removed and then the reaction mixture
was purified by flash column chromatography on silica gel (eluent:
2
from CH Cl /MeOH to give 3b (32.7 mg, 0.033 mmol, 58%) as
a pale yellow solid. R =0.22 (eluent: 2% MeOH/CH Cl ); H NMR
The mixture was heated at 808C for 12 h, cooled, and then parti-
% MeOH/CH Cl ), followed by evaporation, and recrystallization
2 2
tioned between CH Cl , water and a saturated aqueous solution of
2
2
2
2
NaCl. The combined extracts were dried over Na SO and evaporat-
2
4
1
f
2
2
ed. The residue was then purified by column chromatography on
(600 MHz, CDCl , 208C): d=8.47 (brs, 2H; NH), 6.70 (brs, 2H; pyr-
3
silica gel (Wakogel C-300; eluent: CH Cl /n-hexane=1:1) to give di-
2
2
role-H), 6.61 (s, 2H; Ar-H), 6.22 (brs, 2H; pyrrole-H), 6.16–6.15 (m,
2
6.6 Hz, 4H; OCH C H31), 1.83–1.74 (m, 6H; OCH CH C H29), 1.55–
2 15 2 2 14
tert-butyl
2-(3,4,5-trihexadecyloxyphenyl)malonate
(1.56 g,
H; pyrrole-H), 4.07 (t, J=6.6 Hz, 2H; OCH C H ), 3.90 (t, J=
2 15 31
1
.54 mmol, 77%) as a white solid. R =0.35 (eluent: CH Cl /n-
f
2
2
1
hexane=1:1); H NMR (600 MHz, CDCl , 208C): d=6.56 (s, 2H; Ar-
3
1
0
1
3
.41 (m, 6H; OC H CH C H ), 1.35–1.25 (m, 72H; OC H C H CH ),
.89–0.86 ppm (m, 9H; OC H CH ); UV/Vis (CH Cl ): l (e”
max
0 )=273.5 nm (2.3m cm ); fluorescence (CH Cl ): l (l )=
76 nm (274 nm); MALDI-TOF-MS: m/z (%):995.9 (100) [M+H] .
2
4
2
13 27
3
6
12 24
3
H), 4.29 (s, 1H; CH), 3.96–3.91 (m, 6H; OCH C H ), 1.80–1.70 (m,
2
15 31
1
À1
5
30
3
2
2
6
H; OCH CH C H ), 1.46 (s, 18H; tBu), 1.46–1.41 (m, 6H;
2 2 14 29
À4
À1
2
2
em
ex
OC H CH C H ), 1.35–1.25 (m, 78H; OCH CH and OC H C H CH ),
2
4
2
13 27
2
3
3
6
12 24
3
+
0
1
.89–0.87 ppm (m, 9H; OC H CH ); MALDI-TOF-MS: m/z (%):
15 30 3
013.9 (100) [M+H] .
+
Single-crystal X-ray analysis
Crystallographic data for ion-pair complexes of dipyrrolylpyrazoles
+
À
are summarized in Table 1. Single crystals of 3a·H ÀCF CO were
3
2
2-(3,4,5-Trihexadecyloxyphenyl)malonic acid (3b’’)
obtained by vapor diffusion of n-hexane into a solution of 3a and
TFA (3.6 mL) was added to a solution of di-tert-butyl 2-(3,4,5-trihex-
TFA in CH Cl in a 1:1 molar ratio. The crystal was a colorless prism
2
2
+
adecyloxyphenyl)malonate (1.56 g, 1.54 mmol) in CH Cl2 (10 mL)
of approximate dimensions 0.40”0.10”0.10 mm. Complex (1·H
2
À
and stirred at RT for 2 h. The reaction mixture was partitioned be-
tween CH Cl and a saturated aqueous solution of NaHCO . The
) À(CF ) (CO ) was obtained by vapor diffusion of n-hexane into
2
2 4
2
2
a solution of 1 and (CF ) (CO H) in a 2:1 molar ratio in DME. The
2
2
3
2 4
2
2
aqueous phase was acidified with an aqueous solution of HCl, and
then the product was extracted with diethyl ether. The combined
data crystal was a colorless prism of approximate dimensions
+
À
0.20”0.20”0.10 mm. Single crystals of (3a·H ) À(CF ) (CO ) were
2
2 4
2
2
extracts were dried over Na SO4 and evaporated to give 3b’’
obtained by vapor diffusion of n-hexane into a solution of 3a and
2
1
(
1.39 g, 1.54 mmol, quant) as a white solid. H NMR (600 MHz,
(CF ) (CO H) in a 2:1 molar ratio in CHCl /DME. The crystal was
2
4
2
2
3
CDCl , 208C): d=6.57 (s, 2H; Ar-H), 4.57 (s, 1H; CH), 3.98–3.92 (m,
a colorless prism of approximate dimensions 0.40”0.10”0.05 mm.
Data were collected at 93 K on a Rigaku RAXIS-RAPID II diffractom-
eter with graphite monochromated CuKa radiation (l=1.54187 Š),
and structures were solved by direct methods. The non-hydrogen
atoms were refined anisotropically. The calculations were per-
3
6
6
0
H; OCH C H ), 1.80–1.70 (m, 6H; OCH CH C H ), 1.47–1.42 (m,
2 15 31 2 2 14 29
H; OC H CH C H ), 1.33–1.21 (m, 72H; OC H C H CH ), 0.89–
2
4
2
13 27
3
6
12 24
3
.87 ppm (m, 9H; OC H CH ); ESI-TOF-MS (FT-ICR): m/z (%): 899.8
15
30
3
À
(
100) [MÀH] .
Chem. Eur. J. 2015, 21, 9520 – 9527
www.chemeurj.org
9525
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
and Figure S13 in the Supporting
+
2À
+
2À
+
Table 1. Crystallographic details for ion pairs 3a·H ÀCF
3
CO
,
(1·H )
2
À(CF
2
)
4
(CO
)
2
,
and (3a·H )
2
À
+
Information), and (3b·H ) as
À
2
(CF
2
)
4
(CO
2
)
2
.
À
a (CF ) (CO ) complex (Figure 5b
2
8
2
2
+
2À
+
2À
+
2À
and Figure S13 in the Supporting
Information) with a quartz capilla-
ry and an imaging plate as a de-
tector, for which the diffraction
pattern was obtained with a 0.018
step in 2q. The exposure time to
the X-ray beam was 10 to 60 s.
3
a·H ÀCF
3
CO
(1·H )
2
À(CF
2
)
4
(CO
)
2
(3a·H )
2
À(CF
)·C
2
)
4
(CO
)
2
formula
C
17
H
15
N
4
·C
2
F
3
O
2
2(C11H
11
N
4
)·C
6
F
8
O
4
2(C17
H
15
N
4
6 8 4
F O
M
r
388.35
0.40”0.10”0.10
monoclinic
686.54
838.78
0.40”0.10”0.05
monoclinic
crystal size [mm]
crystal system
space group
a [Š]
b [Š]
c [Š]
0.20”0.20”0.10
monoclinic
C2/c (no. 15)
32.4979(6)
6.05510(10)
15.9142(3)
90
P2
1
/a (no. 14)
1
P2 /a (no. 14)
16.5316(6)
5.9855(2)
17.8433(7)
90
16.3472(5)
6.1376(2)
19.0404(5)
90
a [8]
b [8]
91.687(2)
90
1764.83(11)
1.462
114.3858(9)
90
2852.18(9)
1.599
104.0875(16)
90
1852.92(10)
1.503
Flash-photolysis time-resolved
microwave conductivity (FP-
TRMC)
g [8]
3
V [Š ]
À3
1calcd [gcm
]
Z
T [K]
4
4
4
The charge-carrier mobility was
measured by FP-TRMC technique.
93(2)
1.023
14369
3043
253
1.54187
0.0682
0.1057
1.000
93(2)
1.278
13033
2600
245
1.54187
0.0535
0.0954
1.067
93(2)
1.101
17619
3366
271
1.54187
0.0810
0.1867
1.075
À1
m(CuKa) [mm
no. of reflns
no. of unique reflns
variables
]
+
À
,
2
Complexes 3b, 3b·H ÀCF CO
3
+
À
2
(3b·H ) À(CF ) (CO ) ,
and
were
2
2 4
2
+
À
(3b·H ) À(CF ) (CO )2
2
2 8
2
lCuKa [Š]
mounted on a quartz plate, once
heated up to the isotropic state,
and then cooled to RT, to afford
thin-film samples. Charge carriers
were photochemically generated
by using a third-harmonic genera-
R
1
(I>2s(I))
wR (I>2s(I))
GOF
2
tion (l=355 nm) of
a Spectra
formed by using the Crystal Structure crystallographic software
Physics model INDI-HG Nd:YAG laser with a pulse duration of 5–
[12]
16
package of the Molecular Structure Corporation. CCDC-942381,
42382, and 942383 contain the supplementary crystallographic
8 ns. The photon density of a l=355 nm pulse was 0.9”10 pho-
2
9
tons per cm . The microwave frequency and power were set at
data for this paper. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
about 9.1 GHz and 3 mW, respectively. The TRMC signal, picked up
by a diode (rise time <1 ns), was monitored by means of a Tektron-
ics model TDS3032B digital oscilloscope. The observed conductivi-
ties were normalized, given by a photocarrier generation yield (f)
multiplied by sum of the charge carrier mobilities (Sm), according
to the equation fSm=(1/eAI F )(DP /P ), in which e, A, I , Flight,
DFT and AM1 calculations
0
light
r
r
0
Ab initio and semiempirical calculations of p-conjugated molecules
P, and DP were the unit charge of a single electron, the sensitivity
r
r
À1
[8]
were carried out by using the Gaussian 03 program and an HP
Compaq dc5100 SFF computer. The structures were optimized, and
the total electronic energies were calculated at the B3LYP level by
using a 6-31G(d,p) basis set for 3a, 3c (the derivative possessing
methoxy substituents in place of hexadecyloxy moieties in 3b),
factor (S cm), the incident photon density of the excitation laser
À2
À1
(
photon cm ), a correction (or filling) factor (cm ), and the reflect-
ed microwave power and its change, respectively. All experiments
were carried out at RT in an ambient atmosphere.
+
+
+
À
3
3
a·H , 3c·H , and 3a·H ÀCF CO and at AM1 level for 3b and
3
2
+
b·H .
Acknowledgements
Differential scanning calorimetry (DSC)
The phase transition points were observed by using a differential
scanning calorimeter (PerkinElmer Diamond DSC).
This work was supported by a Grants-in-Aid for Young Scien-
tists (A) (no. 23685032) and Scientific Research (B) (no.
2
2
6288042) and on Innovation Areas (“Photosynergetics” Area
606, no. 26107007) from the MEXT and Ritsumeikan R-GIRO
Polarizing optical microscopy (POM)
project (2008–2013). We thank Prof. Atsuhiro Osuka and Hiro-
taka Mori, Kyoto University, for single-crystal X-ray analysis; Dr.
Katsuhiro Isozaki and Prof. Hikaru Takaya, Kyoto University, for
FT-ICR-MS measurements; Dr. Noboru Ohta, JASRI/SPring-8, for
synchrotron XRD analysis; Prof. Kazuchika Ohta, Shinshu Uni-
versity, for the valuable discussion on the transition behavior;
Prof. Tomonori Hanasaki, Ritsumeikan University, for DSC and
POM measurements; and Prof. Hitoshi Tamiaki, Ritsumeikan
University, for various measurements. T.S. thanks JSPS for a Re-
search Fellowship for Young Scientists.
POM measurements were carried out with a Nikon OPTIPHOT-POL
polarizing optical microscope equipped with a Mettler FP82 HT
hot stage.
Synchrotron XRD analysis
High-resolution XRD analyses were carried out by using a synchro-
tron radiation X-ray beam with a wavelength of 1.00 Š on BL40B2
at SPring-8 (Hyogo, Japan). A large Debye–Scherrer camera with
+
a camera length of 546.28 mm for XRD of 3b (Figure 2), 3b·H À
À
+
À
2 2
CF CO (Figure 3), (3b·H ) as a (CF ) (CO ) complex (Figure 5a
3
2
2
2 4
Chem. Eur. J. 2015, 21, 9520 – 9527
www.chemeurj.org
9526
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[
[
6] Complementary hydrogen-bonding interactions are effective for the
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Beare, J. F. Hartwig, J. Org. Chem. 2002, 67, 541–555.
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2À
[
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2
À(CF
2
)
8
(CO
)
2
exhibited two transitions
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1359–1399.
Published online on May 26, 2015
Chem. Eur. J. 2015, 21, 9520 – 9527
www.chemeurj.org
9527
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim