Luminescent, liquid crystalline tris(N-salicylideneaniline)s: Synthesis and characterization

Article abstract of DOI:10.1021/jo9001933

A new class of discotics derived from tris(N-salicylideneaniline)s have been synthesized and their thermal and photophysical properties are investigated. These systems with outer 1,3,4-oxadiazole wings exist in an inseparable mixture of two keto-enamine tautomeric forms with C_3h and C_s rotational symmetries, and self-assemble into fluid columnar phase over a wide thermal range as evidenced by several complementary studies. They possess emissive characteristics in both solution and columnar states; the blue light (λ = 474 nm) emission has been evidenced for the former state.

Full text of DOI:10.1021/jo9001933

have been attracting special attention as they combine the unique
feature of self-assembly and intrinsic light emitting capabilities
that are promising in emissive LC displays4 and anisotropic
OLEDs.5 This is especially striking in the case of columnar (Col)
phases of disk-shaped (discotic) LCs, in which the aromatic
cores stack on top of one another and the columns thus formed
possess two-dimensional (2D) lattice. The strong π-π interac-
tion and thus the thorough overlap of the frontier orbitals of
the aromatic cores enables the facile charge migration along
the columns, a fundamental feature required for the OLED
functioning. Specifically, they can be used as components of
OLEDs such as hole transport (p-type), electron transport (n-
type), and emissive layers.1 Besides the economic feasibility,
ease of processability, self-healing of structural defects, and the
possibility to tune their properties make the Col phases very
attractive. Indubitably, Col phases are gaining acceptance as
substitutes for single crystals or conjugated polymers that are
used in electronic devices such as OLEDs,5 photovoltaic cells,
and field effect transistors.6
Luminescent, Liquid Crystalline
Tris(N-salicylideneaniline)s: Synthesis and
Characterization
Channabasaveshwar V. Yelamaggad,*
Ammathnadu S. Achalkumar, D. S. Shankar Rao, and
S. Krishna Prasad
Centre for Liquid Crystal Research,
Jalalhalli, Bangalore 560013, India
yelamaggad@gmail.com
ReceiVed January 30, 2009
In this context, tris(N-salicylideneaniline)s (TSANs),7-9
a
novel class of compounds existing as a mixture of C3h and Cs
symmetric keto-enamine tautomers, are promising as they
readily offer induction and tuning of both electronic, viz.
luminescence, as well as molecular material features like self-
organizing ability, molecular recognition, etc.7-9 For example,
based on the work of McLachalan et al., we have recently
demonstrated that by the space-filling approach TSANs can be
made to stabilize Col phase(s).8a In a later study, we noted that
these materials possess some promising inherent electronic
(fluorescence) property in solutions.8b,c Interestingly, other
studies have disclosed that the electronic properties of TSANs,
in particular the C3h isomer, can be effectively altered by
changing their peripheral substitutions; Lee et al. have deter-
A new class of discotics derived from tris(N-salicylidene-
aniline)s have been synthesized and their thermal and
photophysical properties are investigated. These systems with
outer 1,3,4-oxadiazole wings exist in an inseparable mixture
of two keto-enamine tautomeric forms with C3h and Cs
rotational symmetries, and self-assemble into fluid columnar
phase over a wide thermal range as evidenced by several
complementary studies. They possess emissive characteristics
in both solution and columnar states; the blue light (λ )
474 nm) emission has been evidenced for the former state.
(2) (a) Heeger, A. J.; Diaz-Garcia, M. A. Curr. Opin. Solid Phys. Mater.
Sci. 1998, 3, 16–22. (b) Friend, R. H.; Gymer, R. W.; Holmes, A. B.; Burroughes,
J. H.; Marks, R. N.; Taliani, C.; Bradley, D. D. C.; dos Santos, D. A.; Bredas,
J. L.; Logdlund, M.; Salaneck, W. R. Nature 1999, 397, 121–128. (c) Molenkamp,
W. C.; Watanabe, M.; Miyata, H.; Tolbert, S. H. J. Am. Chem. Soc. 2004, 126,
4476–4477.
(3) (a) Tang, C. W.; Van Slyke, S. A. Appl. Phys. Lett. 1987, 51, 913–915.
(b) Shi, J.; Tang, C. W. Appl. Phys. Lett. 1997, 70, 1665–1667. (c) Hung, L. S.;
Chen, C. H. Mater. Sci. Eng., R 2002, 39, 143.
(4) Beer, A.; Scherowsky, G.; Owen, H.; Coles, H. Liq. Cryst. 1995, 19,
565, and references cited therein. .
(5) Christ, T.; Glusen, B.; Greiner, A.; Kettner, A.; Sander, R.; Stumpflen,
V.; Tsukruk, V.; Wendorff, J. H. AdV. Mater. 1997, 9, 48.
(6) (a) Adam, D.; Schuhamcher, P.; Simmerer, J.; Hayssling, L. K.;
Siemensmeyer, K. H.; Etzbach, H.; Ringsdorf; Haarer, D. Nature 1994, 371,
141–143. (b) Osburn, E. J.; Schmidt, A. L.; Chau, K.; Chen, S. Y.; Smolenyak,
P.; Armstrong, N. R.; O’Brian, D. F. AdV. Mater. 1996, 8, 926–928. (c) Schmidt-
Mende, L.; Fechtenkotter, A.; Mullen, K.; Moons, E.; Friend, R. H.; MacKenzie,
J. D. Science 2001, 293, 1119–1126. (d) Kumar, S. Chem. Soc. ReV. 2006, 35,
83–109.
(7) (a) Chong, J. H.; Sauer, M.; Patrick, B. O.; MacLachlan, M. J. Org. Lett.
2003, 5, 3823–3826. (b) Sauer, M.; Yeung, C.; Chong, J. H.; Patrick, B. O.;
MacLachlan, M. J. J. Org. Chem. 2006, 71, 775–788.
(8) (a) Yelamaggad, C. V.; Achalkumar, A. S.; Rao, D. S. S.; Prasad, S. K.
J. Am. Chem. Soc. 2004, 126, 6506–6507. (b) Yelamaggad, C. V.; Achalkumar,
A. S. Tetrahedron Lett. 2006, 47, 7071–7075. (c) Yelamaggad, C. V.;
Achalkumar, A. S.; Rao, D. S. S.; Prasad, S. K. J. Org. Chem. 2007, 72, 8308–
8318.
(9) (a) Riddle, J. A.; Bollinger, J. C.; Lee, D. Angew. Chem., Int. Ed. 2005,
44, 6689–6693. (b) Riddle, J. A.; Lathrop, S. P.; Bollinger, J. C.; Lee, D. J. Am.
Chem. Soc. 2006, 128, 10986–10987. (c) Jiang, X.; Bollinger, J. C.; Lee, D.
J. Am. Chem. Soc. 2006, 128, 11732–11733.
The design, fabrication, and optimization of efficient light
emitting diodes (LEDs) based on organic materials is one of
the thrust areas of research due to the promising applications
in flat-panel displays.1 The vital factor for the successful
development of organic light emitting devices (OLEDs) is the
molecular engineering and synthesis of stable emissive organic
compounds associated with desired properties. Thus, a wide
range of materials varying from the low molar mass materials
to processable polymers2,3 have been realized to examine their
suitability for OLEDs. Of these, the structurally diverse
functional single molecules with the ability to form LC phases
* To whom correspondence should be addressed.
(1) (a) Kelly, S. M. In Flat Panel Displays: AdVanced Organic Materials;
RSC Materials Monographs; Royal Society of Chemistry: Letchworth, UK, 2000.
(b) Kraft, A.; Grimsdale, A. C.; Holmes, A. B. Angew. Chem., Int. Ed. 1998,
37, 402–428. (c) Hoga, B. P.; Gin, D. L. Liq. Cryst 2004, 31, 185–199, and
references cited therein.
3168 J. Org. Chem. 2009, 74, 3168–3171
10.1021/jo9001933 CCC: $40.75 2009 American Chemical Society
Published on Web 03/24/2009

TABLE 1. Transition Temperatures (°C)a and enthalpies (kJ
mol-1) of the TSANs 1-4
SCHEME 1. Synthesis of Oxadiazole-Based TSANsa
phase sequenced
TSANs (C3h:Cs)b
heating
cooling
1 (1:2.9)
2 (1:2.5)
3 (1:2.6)
Cr 212.6 (7.3), Colc
Cr 157.4 (13.4), Colh
Cr1 63.4 (131.6), Cr2 157.3 (29.4), I 265.7 (4.9), Colh
Colh 269.2 (5.6), I 24.6 (51.5), Cr
Cr1 71.4 (122), Cr2 115.2 (28.6), I 111.3 (23.7), Colh
Cr3 145.9 (14.9), I 64.7 (128), Cr
c
4 (1:2.7)
a Phase transition temperatures (°C) and corresponding enthalpies (J/g)
obtained from DSC thermograms during first heating and cooling cycles.
b
Ratio obtained from H NMR. c The clearing temperature could not be
1
detected in both POM and DSC as it exceeds 300 °C. d Cr, Cr1 Cr2
crystal, Colh ) columnar hexagonal phase, I ) isotropic phase.
)
a wide verity of luminescent LCs in the future. Finally, the
reaction of anilines with 1,3,5-triformylphloroglucinol (12)
afforded TSANs 1-4. The pure yellowish solids were charac-
terized by routine spectroscopic methods coupled with elemental
analyses.
1H NMR spectra of TSANs 1-4 revealed that they exist in
two inseparable keto-enamine tautomeric forms having C3h and
Cs symmetries, as expected. In particular, the spectra showed
multiple peaks between 8.8-9 and 13.1-13.6 due to coupling
between enamine (vinylic: Hb, Hd, Hf, and Hh) and secondary
amine (NH: Ha, Hc, He, and Hg) protons (see Table 1).12 In
principle, the measure of the area under the peaks (the
integration) of Ha against Hc, Hg, and He of amine protons or
Hb vs. Hd, Hf, and Hh can be considered to adjudge the ratio of
two forms. However, owing to the close proximity of chemical
shifts of enamine protons, we have considered amine protons
for estimating the ratio of the two geometrical isomers (shown
in Table 1). The coupling between the enamine and the NH
a Reagents and condtions: (i) ethanol, hydrazine hydrate, reflux °C, 1 h
(90%); (ii) 3,4,5-trimethoxybenzoyl chloride, pyridine, 60 °C, 12 h (75%);
(iii) POCl3, 100 °C, 5 h (70%); (iv) BBr3, CH2Cl2, -78 °C to rt, 17 h
(65%); (v) n-bromoalkane, anhydrous K2CO3, DMF, 80 °C, 17 h (80-85%);
(vi) 10% Pd-C, H2 (balloon, 1 atm) THF, rt, 12 h (80-82%); (vii) ethanol,
reflux, 6 h (65-75%).
mined that stereoelectronic control of self-assembly of C3h
isomers can enhance their fluorescence efficiency in solutions.
These studies inspired us to incorporate a fluorophore in TSANs
to possibly modify their luminescence characteristics while
retaining the desired mesomorphism. The 1,3,4-oxadiazole was
the obvious option given the fact that it shows promising
electron transport and emission characteristics when used in
OLEDs either as a dopant or as a part of another molecular
system.10 Thus, the oxadiazole moiety in TSANs is expected
to tune not only the emissive property but also the electron
carrier (n-type) characteristics. We report here the synthesis and
characterization of discotic TSANs 1-4 comprised of 1,3,4-
oxadiazole cores.
The synthetic strategy to achieve these novel discotic TSANs
bearing 1,3,4-oxadiazole fluorophores is illustrated in Scheme
1. Methyl 4-nitrobenzoate (5) was reacted with hydrazine
hydrate in refluxing ethanol to obtain the hydrazide 6 that on
treatment with 3,4,5-trimethoxybenzoyl chloride in the presence
of pyridine furnished N-benzoylbenzohydrazide 7. Phosphoryl
trichloride-mediated cyclization of 7 yielded the trimethoxy
oxadiazole derivative 8,11 which on demethylation with BBr3
at -78 °C furnished the key precursor, namely, 2-(4-nitrophe-
nyl)-5-(3,4,5-trihydroxyphenyl)-1,3,4-oxadiazole (9), in 65%
yield. Compound 9 on O-alkylation with n-alkyl bromides under
Williamson’s ether synthesis condition yielded the nitro com-
pounds 10a-d, which on catalytic hydrogenation provided the
requisite vital anilines 11a-d. To our knowledge, compounds
9-11 were unknown hitherto, and are promising for realizing
1
protons was further confirmed by the H-1H COSY NMR
spectra.12
Furthermore, the strong coupling (3JHH ≈ 13 Hz)12 elucidates
the localization of the proton on the nitrogen atom. The phase
behavior of the synthesized TSANs 1-4 was established with
the aid of a polarizing optical microscope (POM), a differential
scanning calorimeter (DSC), and X-ray diffraction (XRD). The
sample placed between a clean untreated glass slide and a
coverslip was used for the POM study. The preliminary
mesophase assignment was based on the two inherent properties
displayed by mesogenic TSANs: the birefringence and fluidity.
The signatures observed in DSC thermograms due to phase
transitions of all the samples were consistent with those of the
optical experiments. In general, the phase transition temperatures
deduced from calorimetric measurements of the first heating
and cooling cycles at a rate of 5 deg/min are considered.
However, when the thermal signatures were not observed in
DSC thermograms, the transition temperatures were taken from
the microscopic observations. A summary of the results deduced
from these complementary techniques has been presented in
Table 1.
In the microscopic study, the solid compounds 1 and 2 were
observed to clearly melt into an identical mesomorphic state at
213 and 158 °C, respectively, showing birefringent homoge-
neous fluid (easily shearable) patterns that remained unaltered
until about 300 °C (experimental limitation). On subsequent
cooling of the samples, no textural change was observed except
(10) (a) Adachi, C.; Tsutui, T.; Saito, S. Appl. Phys. Lett. 1990, 56, 799. (b)
Antoniadis, H.; Inbasekaran, M.; Woo, E. P. Appl. Phys. Lett. 1998, 73, 3055.
(11) Radha Vakula, T.; Saraswathi, T. V.; Srinivasan, V. R. Indian J. Chem.
1968, 6, 172–173.
(12) See the Supporting Information.
J. Org. Chem. Vol. 74, No. 8, 2009 3169

FIGURE 1. Photomicrographs of textures observed under POM of the
Colh phases of 3 at 258 °C (a) and 4 at 78 °C (b).
FIGURE 2. (a) Absorption spectrum (blue trace) and emission spectrum
(orange trace) (excited at 420 nm) obtained for TSAN 3 in THF solution
(2.3 × 10-6 M); the inset shows the pictures of solutions as seen before
(left hand side (LHS)) and after the illumination (right hand side (RHS))
of 365 nm light. (b) Thin film absorption spectrum (LHS) at room
temperature and emission spectra (RHS) for the thin film as a function
of temperature.
TABLE 2. The Results of Indexation of XRD Profiles of TSANs
phaseb
T/°C
lattice
Miller
TSAN
da/Å
intensityc parameters/Å indices hkl
2
Colh 200 40.6
s
d
s
d
d
s
d
d
s
a: 46.82
100
100
4.8
Colh 230 42.9
4.9
3
4
a: 49.57
c: 3.64
peak in the low-angle region; the absence of expected multiple
reflections for the Col phase can be ascribed to a minimum in
the form factor. This is analogous to several reports wherein
such a pattern has been assigned to a hexagonal columnar phase
(Colh).13 Although the presence of a single maximum at low
angles does not allow for an unambiguous determination of the
mesophase structure, the microscopic textures are consistent with
a uniaxial, hexagonal columnar structure. It may be mentioned
that the lattice constant a and not the d10 spacing, which is
comparable to the diameter of the molecule (determined with
Chem3D Ultra 9), supports the argument that the structure is
hexagonal columnar. In the wide-angle region, except for TSAN
2, two broad reflections were observed. The first maximum
corresponding to a spacing in the range of 4.5-4.9 Å is
associated with the liquid-like correlation of the discs within
the column. The second reflection indexed as (001) in the range
of 3.4-3.6 Å indicates the periodic stacking, although short
ranged, of the molecular cores within the column. Thus, the
X-ray data coupled with the textural patterns suggest that the
mesophase is indeed the Colh phase. In the case of TSAN 4,
the X-ray evidence is more unambiguous with the existence of
a second peak at low angles; the ratio of the spacings of the
low angle reflections is 1:(1/ꢀ3), a feature expected for the Colh
phase.
As discussed before, owing to the presence of multiple
chromophores and possible π-conjugations between the periph-
eral region and the central core, this series of discotic TSANs
are expected to exhibit promising photophysical properties. The
absorption and emission characteristics of these compounds were
probed by using their solutions in tetrahydrofuran (10-6 M).12
Figure 2a shows the combined UV-vis absorption and photo-
luminescent (PL) spectra of TSAN 3 as a representative case.
The absorption spectrum (see the blue trace in Figure 2a) shows
two bands around 353 and 438 nm attributed to the π-π* and
n-π* transitions. Interestingly, upon irradiation with light of
420 nm, a sharp emission line in the blue region with a shoulder
(at 498 nm) was obtained (474 nm; orange trace). This is
remarkable given the fact that the blue light emitting materials
3.64
47.4
4.5
3.44
48.3
001
100
Colh 50
Colh 90
a: 54.77
c: 3.44
001
100
110
a: 55.82
c: 3.39
27.8
4.6
3.39
s
d
d
001
a d is spacing. b Colh: hexagonal columnar phase. c s: strong, d:
diffuse.
that mechanical shearing was not possible near room temper-
ature. These transitions were highly reproducible, implying that
these TSANs are chemically and thermally stable. As expected,
for both compounds, DSC thermograms showed only a signature
due to transition from the crystalline phase into the mesophase
during the first heating cycle, while no peaks were detected in
the successive cooling cycle or subsequent heating/cooling scans,
which imply that the mesophase is glassy in nature at room
temperature. Notably, the mesophases of 1 and 2 could be mixed
well with the LC phases formed by TSANs 3 and 4, which we
shall discuss later, clearly indicating that all of them show an
identical mesophase. Compounds 3 and 4 having longer alkyl
chains were found to display an enantiotropic and a monotorpic
mesophase, respectively, with lower transition temperatures. On
heating, the solid TSAN 3 melted (at 158 °C) into a mesophase
with the nonspecific textural features identical to ones seen for
1 and 2 and remaining unaltered until the isotropic phase (270
°C). On subsequent cooling, it showed fan-shaped defects
interspersed with large homeotropic domains (Figure 1a),
features characteristic of the Col phases. The material crystallizes
at 24 °C. The DSC thermograms12 showed peaks at temperatures
corresponding to those noted in the microscopic study. It may
be mentioned here that the LC phase freezes if the sample is
cooled slowly (about 1 deg/min). As mentioned above, TSAN
4 displayed a monotropic phase having a mosaic textural pattern
as shown in Figure 1b. Thus, the longer (icosyl) chain of 4
effectively reduces the transition temperatures at the expense
of mesophase stability. The high melting points of other TSANs
can be attributed to the strong intermolecular association due
to the large electrical dipole moment of the oxadiazole moiety.
The structural assignment of the Col phase formed by TSANs
2, 3, and 4 was achieved by X-ray diffraction study.12 The results
of indexing of one-dimensional (1D) intensity vs. 2θ profile
deduced from the powder 2D pattern of the Col phases at
different temperatures are summarized in Table 2. Except for
TSAN 4, all the diffactograms showed only a sharp Bragg (10)
(13) (a) Alvarez, L.; Barbera, J.; Puig, L.; Romero, P.; Serrano, J. L.; Sierrra,
T. J. Mater. Chem. 2006, 16, 3768–3773. (b) Hayer, A.; de Halleux, V.; Kohler,
A.; El-Garoughy, A.; Meijer, E. W.; Barbera, J.; Tant, J.; Levin, J.; Lehmann,
M.; Gierschner, J.; Cornil, J.; Geerts, Y. H. J. Phys. Chem. B 2006, 110, 7653.
(c) Barbera, J.; Gimenez, R.; Serrano, J. L. Chem. Mater. 2000, 12, 481, and
references cited therein. (d) Carfagna, C.; Roviello, A.; Sirigu, A. Mol. Cryst.
Liq. Cryst. 1985, 122, 151. (e) Gramsbergen, E. F.; Hoving, H. J.; de Jeu, W. H.;
Praefcke, K.; Kohne, B. Liq. Cryst. 1986, 1, 397. (f) Metersdorf, H.; Ringsdorf,
H. Liq. Cryst. 1989, 5, 1757. (g) Zeng, H.; Carroll, P. J.; Swager, T. M. Liq.
Cryst. 1993, 14, 1421. (h) Artal, M. C.; Toyne, K. J.; Goodby, J. W.; Barbera,
J.; Photinos, D. J. J. Mater. Chem. 2001, 11, 2801–2807.
3170 J. Org. Chem. Vol. 74, No. 8, 2009

TABLE 3. Photophysical Properties of TSAN 3
forms exhibit emissive characteristics. Notably, solutions show
blue fluorescence, while glassy Col film shows preserved
emission behavior and 2D order. Thereby, we have disclosed a
simple way of modifying molecular self-assembling and light-
generating ability of TSANs. Importantly, some novel oxadia-
zole-based intermediates have been synthesized, which could
be useful in the synthesis of light emitting liquid crystals.
state
absorption/nm
emissionb/nm
Stoke’s shift
solution (THF)a
glassy film (at rt)
353, 438
350, 418
474, 498 sh
545 sh, 610
36
192
a 10-6 M solution. b Excitation wavelength 420 nm; sh ) shoulder.
are not only scarce but also their energy levels are high, and
provide an effective approach in fine-tuning wavelength of
emission on combining with another dopant emitter.10,14 Fur-
thermore, the absorption-emission behavior of the fluid Col
phase as well as its frozen state in the form of thin film was
studied for TSAN 3 as a representative case. The substance held
between the two coverslips was heated to isotropic phase, then
cooled slowly until room temperature. Figure 2b illustrates the
absorption of the frozen Col phase as well as the PL spectra of
the Col structure at different temperatures starting from room
temperature. The UV-vis spectrum of the film at room tem-
perature shows two absorption bands at 350 and 418 nm similar
to solution spectrum. On excitation (420 nm), the film showed
a broad emission band at 610 nm (Stokes shift ca. 192 nm)
with a shoulder at 545 nm (see Table 3). This large red shift
can be attributed to the strong intermolecular interactions within
the structure as well as the thickness of the sample. Therefore,
for very thin (spin coated or vacuum deposited) samples there
is the possibility that emission might shift toward the blue
region. It can be seen that the fluorescence intensity decreases
with the increase in the temperature indicating the breaking-up
of the large stacks and thermally activated radiationless pro-
cesses.15 Thus, the emissive frozen Col phase of TSANs
characterized by the preserved 2D order and the short intraco-
lumnar distance that facilitates motion of charges with impound-
ing motion of the ionic impurities16 are promising in optoelec-
tronic applications.
Experimental Section
All the TSANs were synthesized following the experimental
procedure described below for the TSAN 1 as a representative case.
The preparation of all the intermediates and other TSANs and
instrumentation are given in the Supporting Information.
A mixture of triformylphloroglucinol (0.005 mmol, 1 equiv) and
aniline 11a (0.19 mmol, 3.4 equiv) in absolute ethanol (50 mL)
was heated to reflux under inert atmosphere for 6 h with vigorous
stirring. The dull yellow solid that separated upon cooling the
reaction mixture was collected by filtration, repeatedly washed with
ethanol, and air-dried. The crude product was purified by repeated
recrystallizations in a mixture of absolute ethanol-THF (9:1) to
obtain 1. Rf 0.54 (40% EtOAc-hexanes); an orange solid; yield
75%; UV-vis λmax ) 425.94 nm, ε ) 12.9239 × 104 L mol-1cm-1
;
IR (KBr pellet) νmax 2922, 2852, 2359, 1627, 1599, 1492, 1457,
1290, 1255, 1180, 1117, 1009, 838, 773, and 739 cm-1; H NMR
1
(CDCl3, 400 MHz) δ 13.57 (d, J ) 13.0 Hz, dCNH), 13.51 (d, J
) 13.1 Hz, dCNH), 13.2 (d, J ) 12.9 Hz, dCNH), 8.82-8.95
(m, 3H, dCHN), 8.14-8.16 (m, 6H, Ar), 7.49 (t, 6H, J ) 8.9 Hz,
Ar), 7.32 (s, 6H, Ar), 4.02-4.1 (m, 18H, 9 × OCH2), 0.87-1.86
(m, 189H, 81 × CH2, 9 × CH3). Anal. Calcd for C150H231N9O15:
C, 75.05; H, 9.7; N, 5.25. Found: C, 75.23; H, 9.28; N, 4.91.
Acknowledgment. Prof. Suresh Das and Dr. Shibu Abraham,
RRL, Trivendrum, and Prof. Uday Maitra and Mr. Nonappa,
IISc, Bangalore, are gratefully acknowledged for providing their
instruments to carry out the luminescence experiments and
useful discussions.
In conclusion, the synthesis, thermal behavior, and qualitative
photophysical property of TSANs appended with 1,3,4-oxadi-
zoles are reported. Their solutions and fluid columnar phases
facilitated by the self-assembly of two different geometrical
Supporting Information Available: General information,
experimental details, instrumentation, structural characterization
data of all compounds, 1H NMR spectra of compounds 1-4, 8,
9, 10c, and 11c, 1H-1H COSY NMR spectra of TSAN 3, one-
dimensional intensity vs. 2θ profiles of TSANs 2-4, DSC traces
of TSAN 3, and absorption and emission spectra of TSANs
1-3. This material is available free of charge via the Internet
at http://pubs.acs.org.
(14) (a) Tao, S.; Peng, Z.; Wang, P.; Lee, C.-S.; Lee, S.-T. AdV. Funct. Mater.
2005, 15, 1716–721. (b) Hu, N.-X.; Esteghamatian, M.; Xie, S.; Popovic, Z.;
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Spiess, H.-W.; Hudsonk, S. D.; Duank, H. Nature 2002, 419, 384–387.
JO9001933
J. Org. Chem. Vol. 74, No. 8, 2009 3171