- AIE-active mechanoluminescent discotic liquid crystals for applications in OLEDs and bio-imaging
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A multifunctional molecular design of fluorescent discotic liquid crystal (DLC) consisting of a tetraphenylethylene core is reported, which is found to serve as an excellent solid-state emitter in OLED devices with EQE of 4.4% and tunable mechanochromism.
- Bala, Indu,Chawla, Prateek,De, Joydip,Gupta, Santosh Prasad,Jou, Jwo-Huei,Kesavan, Kiran Kishore,M. M., Abdul Haseeb,Pal, Santanu Kumar,Yadav, Rohit Ashok Kumar
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supporting information
p. 14279 - 14282
(2020/11/24)
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- Effect of regioisomerism on the self-assembly, photophysical and gelation behavior of aroylhydrazone based polycatenars: Synthesis and characterization
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In this paper we report five series of aroylhydrazone based polycatenars differing from each other in number and position of alkoxy chains on one end of the core; keeping other end the same. A systematic variation in the structures was carried out to understand the effect of position and chain length on the mesophase behavior. In the case of single alkoxy chain at 4-position, there is a transition from Smectic C to Smectic A mesophase during cooling and Smectic A to Smectic C transition in heating cycle in all the homologues except n = 6 & n = 8. In the case of two alkoxy chains at 3-, 5-positions, the compounds are non-mesogenic in nature. On changing the position of alkoxy chains from 3-, 5-positions to 3-, 4-positions, intermolecular forces weaken and these compounds become liquid crystalline and show columnar rectangular mesophase resulting from the effect of regioisomerism. Moving on to the series with three alkoxy chains, it was observed that 2-, 3-, 4-trialkoxy substituted compounds exhibit columnar rectangular mesophase except lower chain length (n = 6 & 8) while 3-, 4-, 5-trialkoxy substituted aroylhydrazones show columnar rectangular mesophase; except n = 10 which shows columnar oblique mesophase. Thus it was established that on increasing density of alkoxy chains around one terminal, mesophase changes from smectic to columnar mesophase. Temperature dependent Raman studies confirm the presence of intermolecular hydrogen bonding. Further, effect of substitution pattern did not show much influence on the photophysical properties of the mesogenic series in solid and solution state. However, the non-mesogenic series showed a different absorption and emission transition from the mesogenic series in solid and solution state. Solid state fluorescence studies show almost similar emission maxima in all the series. However, it was also noticed that non-mesogenic series show maximum red shifted emission maxima in solid state as compared to that of solution. All the series showed good gelation properties with less than 1% CGC (wt%) suggesting the strong ability of molecules to form gel. These H-bonded liquid-crystalline gels have immense potential for applications in emissive displays.
- Kanth, Priyanka,Singh, Hemant Kumar,Kumar, Vijay,Singh, Sachin Kumar,Rao, D.S. Shankar,Prasad, S. Krishna,Singh, Bachcha
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- Photoluminescent discotic liquid crystals derived from tris(N-salicylideneaniline) and stilbene conjugates: Structure-property correlations
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Luminescent discotic liquid crystals based on tris(N-salicylideneaniline)s [TSANs] bearing trans-stilbene fluorophores have been synthesized. Their mesomorphic and photophysical properties were studied. These TSANs existing in the form of C3h and Cs geometrical isomers of the keto-enamine tautomer self-assemble to form the columnar phase and exhibit fluorescence both in solution and mesophase states. These columnar mesophases also exhibit frozen (glassy) columnar phase, which ensures preserved fluorescence intensity, defect free alignment and simultaneous restriction on the motion of ionic impurities. These features make them promising candidates for the use in organic light emitting diodes, particularly as emissive layers. This study also led to an understanding about the dependence of their mesomorphism (mesophase type, stability and thermal range) and photophysical features on the number and pattern of their peripheral substitution, in comparison to the analogous columnar liquid crystalline TSANs reported earlier.
- Achalkumar, Ammathnadu S.,Veerabhadraswamy,Hiremath, Uma S.,Rao, Doddamane S. Shankar,Prasad, Subbarao Krishna,Yelamaggad, Channabasaveshwar V.
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p. 291 - 305
(2016/05/24)
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- s-Triazine-Based Functional Discotic Liquid Crystals: Synthesis, Mesomorphism and Photoluminescence
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A new series of C3-symmetric, π-conjugated molecules was designed, synthesized and characterized. The materials were derived from electron-accepting s-triazine, appended covalently to electron-donating styrylbenzene arms, and were readily prepared in excellent yield with high purity by means of three-fold condensation of triphosphonate with n-alkoxybenzaldehydes under Horner–Wadsworth–Emmons reaction conditions. Examination of the phase transitional properties by several complementary techniques evidenced self-assembly into a hexagonal columnar phase, occurring over wide and reasonable thermal ranges. The photophysical properties were studied both in solution and in the fluid/frozen columnar states by UV/Vis absorption and photoluminescence spectroscopy. The emission spectra obtained as a function of the temperature rule out the breaking-up of larger columns and a non-radiative, thermally activated process. A study carried out on thin films of the glassy columnar state, which accounts for conserved fluorescence, defect-free orientation, and freezing ionic species, with the help of atomic force microscopy (AFM) images, suggested a homogeneous granular morphology comprising fibrillar structures. Dissimilarities in the surface morphology and birefringence of thin films of the solid and frozen columnar states were clearly shown by Raman spectroscopy. An electrochemical investigation revealed a LUMO energy of ?4.0 eV. Thus, the discotic motifs presented herein meet certain criteria of organic materials, which are essential for developing electronic devices.
- Veerabhadraswamy, B. N.,Dambal, Hashambi K.,Rao, D. S. Shankar,Yelamaggad, C. V.
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p. 2225 - 2237
(2016/08/27)
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- Tuning the thermotropic properties of liquid crystalline p-substituted aroylhydrazones
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The synthesis and mesomorphic properties of forty substituted aroylhydrazones with peripheral mono-, di- and tri- alkoxy chains derived from a p-amino aroylhydrazone core are described. The compounds with two side chains exhibited a smectic A phase, while the compounds with six soft alkoxy side chains at symmetrical positions formed a rectangular columnar mesophase. The structures of these mesophases were confirmed by differential scanning calorimetry (DSC) analysis, polarized optical microscopy (POM) and powder X-ray diffraction (XRD) studies. Raman studies with the help of density functional theory on some of the mesogenic members have been performed to understand the changes in the intermolecular interactions during phase transitions. A structure-property relationship has been deduced, and mesogenic properties are found to be dependent on the chain length, density and position of the alkoxy chains around the molecular core.
- Singh, Hemant Kumar,Singh, Sachin Kumar,Nandi, Rajib,Singh, Madan Kumar,Kumar, Vijay,Singh, Ranjan K.,Rao, D. S. Shankar,Prasad, S. Krishna,Singh, Bachcha
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p. 44274 - 44281
(2015/06/02)
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- Electron transport and electrochemistry of mesomorphic fullerenes with long-range ordered lamellae
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Fullerenes, C60, modified with long alkyl chains form long-range ordered lamellar mesophases permitting a high C60 content. The mesomorphic fullerenes feature reversible electrochemistry and a comparably high electron carrier mobilit
- Nakanishi, Takashi,Shen, Yanfei,Wang, Jiaobing,Yagai, Shiki,Funahashi, Masahiro,Kato, Takashi,Fernandes, Paulo,Moehwald, Helmuth,Kurth, Dirk G.
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supporting information; body text
p. 9236 - 9237
(2009/02/03)
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- Perfectly straight nanowires of fullerenes bearing long alkyl chains on graphite
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Fullerene derivatives bearing long alkyl chains epitaxially adsorb on the basal plane of graphite forming well-ordered one-dimensional lamellae. Within the lamellae, the C60 moieties are organized in a zigzag-type fashion. The ordering is mainl
- Nakanishi, Takashi,Miyashita, Naoko,Michinobu, Tsuyoshi,Wakayama, Yutaka,Tsuruoka, Tohru,Ariga, Katsuhiko,Kurth, Dirk G.
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p. 6328 - 6329
(2007/10/03)
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- Hierarchical supramolecular fullerene architectures with controlled dimensionality
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Self-assembly of a fullerene derivative with long alkyl chains in different solvents results in the formation of hierarchically-ordered supramolecular assemblies with well-defined 1, 2 and 3D architectures such as vesicles, fibers, discs and cones, whose
- Nakanishi, Takashi,Schmitt, Wolfgang,Michinobu, Tsuyoshi,Kurth, Dirk G.,Ariga, Katsuhiko
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p. 5982 - 5984
(2008/01/27)
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- Porphyrin derivatives their use in photodynamic therapy and medical devices containing them
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There is provided a compound of formula (I), wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, X, Y1, Y2, Y3, Z, M, A-B and C-D have meanings given in the description, which are useful in the treatment of medical conditions for which a photodynamic compound is indicated. Compositions, apparatus and methods of treatment of a medical condition for which a photodynamic compound is indicated are also disclosed.
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- 4,4'-Distyrylazobenzene as Mesogen
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From 3,4-dihydroxybenzaldehyde (1) the tetraalkoxy-substituted 4,4'-distyrylazobenzenes (E,E,E)-5a-c are synthesized.A similar reaction sequence leads from ethyl 3,4,5-trihydroxybenzoate (6) to the hexaalkoxy-substituted 4,4'-distyrylazobenzenes (E,E,E)-1
- Kosteyn, Frank,Zerban, Georg,Meier, Herbert
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p. 893 - 898
(2007/10/02)
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