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structures of identical charged species.6g,h Detailed investigations
on the formation of such assemblies are currently under way.
This work was supported by PRESTO/JST (2007–2011),
Grant-in-Aid for Young Scientists (A) (No. 23685032) from the
MEXT and Ritsumeikan R-GIRO project (2008–2013). We thank
Prof. Atsuhiro Osuka, Dr Naoki Aratani, Dr Taro Koide,
Mr Tomohiro Higashino and Mr Hirotaka Mori, Kyoto Univer-
sity, for single-crystal X-ray analysis, Prof. Kazuchika Ohta and
Mr Masahiro Shimizu, Shinshu University, for preliminary
examinations on mesophases, Dr Takashi Nakanishi, NIMS,
for SEM measurements, Prof. Tomonori Hanasaki, Ritsumeikan
University, for POM and DSC measurements, Dr Noboru Ohta,
JASRI/SPring-8, for synchrotron radiation XRD measurements
(BL40B2 at SPring-8), Prof. Hikaru Takaya, Kyoto University, for
XRD measurements carried out in the Joint Usage/Research
Center (JURC) at ICR and Prof. Hitoshi Tamiaki, Ritsumeikan
University, for various measurements.
Fig. 3 (a) POM images of (i) 2dÁClÀ–TATA+ at 64 1C upon first cooling and
(ii) 3dÁClÀ–TATA+ at 70 1C upon second heating and (b) corresponding synchro-
tron XRD pattern of 2dÁClÀ–TATA+.
Notes and references
‡ 2a and 3a exhibited anion-binding behaviour as evident from the Ka
values of 250 000 and 170 000 MÀ1 for ClÀ, 25 000 and 15 000 MÀ1 for BrÀ,
transitions at, for example, 51 1C upon heating. Furthermore, the
POM image of 2dÁClÀ–TATA+ exhibited a broken-fan-like texture at
64 1C upon first cooling (Fig. 3a(i)), whereas 3dÁClÀ–TATA+ showed
a crystal-like texture at 70 1C upon second heating (Fig. 3a(ii)).
XRD analysis of 2dÁClÀ–TATA+ at 64 1C upon first cooling
suggested the formation of a Colr phase of a = 7.34 nm, b =
2.84 nm and c = 0.80 nm (Z = 4.3 for r = 1) consisting of the dimeric
disk unit on the basis of d = 3.67 (200), 2.65 (110), 1.92 (310), 1.83
(400), 1.71 (410), 1.33 (220) and 0.80 (001) nm. In addition, the XRD
pattern at 53 1C upon second heating exhibited a Colr phase of a =
7.76 nm, b = 3.99 nm and c = 0.80 nm (Z = 6.1 for r = 1), suggesting
the increasing number of constituent ion pairs in an ellipsoidal
disk in the expanded unit lattice. In this case, the introduction of a
catechol–boron moiety instead of BF2 changed the phase from Colh
in 1dÁClÀ–TATA+6c to Colr in 2dÁClÀ–TATA+, because of the stacking
of charged planes with parallel displacement. On the other hand,
the XRD pattern of 3dÁClÀ–TATA+ exhibited various phases such as
a Colh phase of a = 5.02 nm and c = 0.85 nm (Z = 4.2 for r = 0.9) at
40 1C upon second heating, on the basis of d = 4.35 (100), 2.62
(110), 2.16 (200), 1.45 (300) and 0.85 (001) nm. In addition, XRD
analysis at 72 1C upon second heating revealed a crystal-like
diffraction pattern, which was found to be well correlated with
an exothermic transition in the DSC profile. The bulky diphenyl-
boron moiety leads to weak stacking between the charged compo-
nents, resulting in low transition temperatures and complicated
structures in the mesophases.
In summary, boron-modified pyrrole-based p-conjugated
anion receptors formed supramolecular assemblies such as meso-
phases based on charge-by-charge assembled structures. The
substituents on a boron affected the assembled structures both
in the absence and presence of anions as a planar cation salt. In
particular, catechol–boron complexes formed mesophases based
on charge-by-charge assemblies, similar to the BF2 complexes,
whereas diphenylboron complexes formed crystal-like meso-
phases upon heating. Further modified boron substituents can
change the mode of assembly and afford various ionic materials
based on charge-segregated assemblies, which comprise stacking
520 000 and 110 000 MÀ1 for CH3CO2 and 77 000 and 50 000 MÀ1 for
À
H2PO4À, respectively, in CH2Cl2; these values were estimated by the changes
in UV/vis absorption spectra upon the addition of anions as TBA salts.
§ Crystal data are summarised in the ESI.
¨
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c
2508 Chem. Commun., 2013, 49, 2506--2508
This journal is The Royal Society of Chemistry 2013