- Exceptional dual fluorescent, excited-state intramolecular proton-transfer (ESIPT) columnar liquid crystals characterized by J-stacking and large Stokes shifts
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Excited-State Intramolecular Proton-Transfer (ESIPT) fluorophores are emerging as promising future materials for electronic and biotechnological applications. ESIPT columnar (Col) liquid crystals (LCs) have been especially projected as the apt materials for advanced technological endeavors. But, there are hardly any explorations in this direction and thus, needing immediate attention. Herein we report on the synthesis, characterization, and ESIPT activity of a homologous series of novel phasmidic bis(N-salicylideneaniline) Col LCs. Optical microscopic, calorimetric and powder X-ray diffraction (XRD) studies evidence the occurrence of hexagonal columnar (Colh) phase having p6mm symmetry where the constituent slices result from the self-assembly of a pair of mesogens in a side-by-side manner facilitated by intense longitudinal π-π interactions. X-ray data confirm the absence of both directionally correlated tilting of the slices and transverse core-core interactions within the columns. Fluorescence probing clearly evidence the ESIPT occurring not only in DCM solution of the mesogens but also in their three-condensed states viz., solid, liquid crystal, and isotropic liquid phase; in general, two archetypal emission bands at ~430 nm (weak) and ~ 630 nm (strong) with large Stokes shifts (250–275 nm) of ESIPT phenomenon have been observed. The slow shift of emission maxima of the ESIPT fluorescence as a function of decreasing temperature without photoluminescence quenching coupled with the estimated tilt angle (?) of the slices normal to the columnar axis (37 to 42o), from the XRD data, confirm the formation of so-called Scheibe or J-aggregates. The redox activity, metal ion sensing ability, and solvatochromism of the mesogens have also been investigated. The study suggests that these ESIPT Col LCs with band-gap of about 3 eV can be regarded as wide-bandgap semiconducting materials having the electronic characteristics falling between those of conventional semiconductors and insulators.
- Kanakala, Madhu Babu,Yelamaggad, Channabasaveshwar V.
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- Self-assembly of taper- and wedge-shaped maleimide derivatives: Synthesis and structure-property relationship
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Herein, we describe design and synthesis of five new amphiphilic systems, viz. 10b-c and 11a-c composed of maleimide at the focal point and alkoxy phenyl ring at the periphery. Their self-assembling behaviour was examined systematically by varying the length of hydrophobic part and aromatic core segment. Evidently, on increasing the aromatic core length, maleimide based amphiphiles relatively emerge as two distinct molecular structures, i.e. wedge- and tapered-shaped. The mesomorphic studies of the two series reveal that, tapered-shaped maleimide derivatives assemble into a smectic A phase with an interesting phasmidic arrangement, whereas the wedge-shaped molecules exclusively form a prospective supramolecular hexagonal columnar mesophase through the intermolecular hydrogen-bonding via maleimide head group. These self-assembled materials could demonstrate high-sensitivity towards various external stimuli.
- Vinayakumara,Kumar, Sandeep,Prasad, S. Krishna,Adhikari, Airody Vasudeva
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p. 765 - 772
(2019/04/25)
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- Supramolecular columnar self-assembly of wedge-shaped rhodanine based dyes: Synthesis and optoelectronic properties
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The development of small π-conjugated functional organic molecules capable of forming supramolecular columnar self-assembly, is a rapidly growing area of material research. In this context, the present work describes the design and synthesis of a new seri
- Vinayakumara,Kumar, Sandeep,Adhikari, Airody Vasudeva
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p. 215 - 222
(2018/11/20)
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- Optoelectronic exploration of novel non-symmetrical star-shaped discotic liquid crystals based on cyanopyridine
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A novel family of non-symmetrical star-shaped cyanopyridine based discotic liquid crystals (CPBz6, CPBz8 and CPBz12) was designed and synthesized, as potential luminescent materials for optoelectronic applications. The length of one of the arms in the design was systematically varied to determine the structure-property relationships. Evidently, all of the compounds exhibited a highly prospective ordered columnar mesomorphism stabilized at ambient temperature with advantageous very low isotropization temperatures. Furthermore, their photophysical characteristics were investigated in depth, both in solution and in the liquid crystal (LC) state. The discotics were found to be intense blue emitters with reasonably good quantum efficiency. Their dynamic intramolecular charge-transfer (ICT) behaviour was confirmed by steady-state absorption and fluorescence spectral analysis in varied solvent polarity. Furthermore, their electrochemical properties were studied from the combination of an experimental method and the theoretical simulations, which elucidated the low laying frontier molecular orbitals (FMOs) with a narrow energy band gap of ~2.0 eV. The resulted visually perceivable emission with favourable energy levels showcases their possible application in electronic display devices.
- Vinayakumara,Swamynathan,Kumar, Sandeep,Adhikari, Airody Vasudeva
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p. 16999 - 17008
(2018/10/24)
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- Wide-Range Columnar and Lamellar Photoluminescent Liquid-Crystalline Lanthanide Complexes with Mesogenic 4-Pyridone Derivatives
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A series of liquid crystals with various lanthanide ions (EuIII, SmIII, and TbIII) was designed and prepared starting from the corresponding lanthanide nitrates and N-alkylated 4-pyridone derivatives bearing mesogenic 3,4,
- Chiriac, Laura F.,Pasuk, Iuliana,Secu, Mihail,Micutz, Marin,C?rcu, Viorel
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p. 13512 - 13522
(2018/09/06)
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- Tuning the self-assembly and photophysical properties of bi-1,3,4-thiadiazole derivatives through electron donor-acceptor interactions and their application in OLEDs
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We report several shape anisotropic molecules that contain two centrally placed 1,3,4-thiadiazole units, which vary from each other with respect to the number and length of the flexible chains at the termini. The number, position and length of the periphe
- Yadav, Abhay Kumar,Pradhan, Balaram,Ulla, Hidayath,Nath, Subrata,De, Joydip,Pal, Santanu Kumar,Satyanarayan,Achalkumar, Ammathnadu S.
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supporting information
p. 9345 - 9358
(2017/09/29)
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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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- Sulfonamide and urea-based anions chemosensors
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The detection of anions has attracted considerable interest because of their importance in various physiological processes. In this study, two sulfonamide and urea-based compounds (1a and 1b) were successfully developed and their spectroscopic and anion recognition properties were fully investigated. These results showed that: (1) compounds showed high selectivity towards cyanide and fluoride ions in CH3CN; (2) compounds only exhibited a large change in fluorescence in the presence of cyanide ions in CH3CN-H2O (95:5, v/v); and (3) compound 1b could act as a gel in dimethyl sulfoxide that transforms into a homogeneous solution upon exposure to cyanide ions. This research suggests that sulfonamide and urea can act as hydrogen-bond donors and provides an alternative approach to the design of novel anion chemosensors.
- Hu, Fang,Cao, Meijiao,Huang, Juanyun,Chen, Zhao,Wu, Di,Xu, Zhiqiang,Liu, Sheng Hua,Yin, Jun
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p. 108 - 115
(2015/04/27)
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- Columnar liquid crystalline self-assembly of hydrogen-bonded rod-coil diblock complexes created from pyrazole/benzoic acid derivatives
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We synthesized hydrogen-bonded rod-coil diblock complexes having both a rigid rod and a flexible coil by combining bithiophene-conjugated pyrazole derivatives and alkoxy-substituted benzoic acid derivatives. Their self-assembled nanostructures were investigated using polarized optical microscopy, molecular modeling, and X-ray scattering in liquid crystalline (LC) state. They form different types of supramolecularLCphases depending on the numbers and lengths of alkoxy substituents in the benzoic acids. Diblock complexes with low volume ratios of aliphatic coils to rod segments (dioctyloxy chains) self-assembled into lamellar phases; systems with higher ratios (didodecyloxy, trioctyloxy, and tridodecyloxy chains) formed columns. In these columnar structures, two pyrazoles and two benzoic acids formed an aromatic tetramer core through N-H···O and O-H···N hydrogen bonds. Two sets of aromatic tetramers surrounded by flexible aliphatic chains were then stacked to give columnar phases. These are novel examples of supramolecular LC structures comprising hydrogen-bonded pyrazole-benzoic acid derivatives with tetrameric rigid aromatic scaffolds.
- Kim, Ho-Joong,Cho, Sung,Park, Jung Su
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p. 2740 - 2745
(2015/11/17)
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- Self-assembly of hekates-tris(N -salicylideneaniline)s into columnar structures: Synthesis and characterization
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Two series of new, photoluminescent star-shaped discotic liquid crystals, recently termed as "hekates", derived from tris(N-salicylideneaniline) s (TSANs), were synthesized by the facile threefold condensation of 3,4-bis(alkoxy)phenyl 4-aminobenzoates/3,4,5-tris(alkoxy) phenyl 4-aminobenzoates with 1,3,5-triformylphloroglucinol and characterized. These two series of discotics with six and nine peripheral n-alkoxy tails were especially designed and accomplished to understand the relation between mesomorphic/photophysical properties and molecular structure. Proton NMR spectral analysis revealed their existence as an inseparable mixture of two keto-enamine tautomeric forms featuring C3h and Cs rotational symmetries. A systematic study into the thermotropic liquid crystal behavior using polarizing optical microscopy, differential scanning calorimetry, and X-ray scattering confirmed the presence of columnar (Col) phase in vast majority of the TSANs prepared. The two-dimensional (2D) lattices of these fluid columnar phases were found to be characteristic of hexagonal Col (Col h), rectangular Col (Colr), or oblique Col (Col ob) phases depending on the number/length of the peripheral flexible chains. The stabilization of the Colob phase, a less commonly found fluid columnar structure, and the first of its kind in TSAN systems, implies very intensive intermolecular (face-to-face) interactions among the TSAN cores within the column. The photophysical properties were investigated both in solution and the columnar states by UV-vis absorption and photoluminescence; markedly, the solution state emits light in the blue region. The light-emitting ability of the Col phase is particularly significant given the possibility that, in such cores, the protons and electrons interact with each other through the H-bonding environment.
- Achalkumar, Ammathnadu S.,Hiremath, Uma S.,Rao, D. S. Shankar,Prasad, S. Krishna,Yelamaggad, Channabasaveshwar V.
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p. 527 - 544
(2013/03/13)
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- Synthesis and characterization of bis [ n -(4-benzoyloxy) Benzylidene{ n (n -di-/tri-alkoxy)benzoyl}-hydrazinato]nickel(II) complexes displaying liquid crystalline columnar phases
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A series of materials based on the aroylhydrazinatonickel (II) complex is synthesized and characterized. The molecule in the materials consist of two 4-benzoyloxy-benzene groups and two benzene rings having two or three alkoxy chains containing 6, 8, 10,
- Abser, M. Nurul,Karim, M. Manzurul,Kauser, Abu,Parvin, Rabeya,Molla, M. Elias,Yeasmin, Zenifer,Zoghaib, Wajdi Michel,Al-Rawahi, Zainab,Carboni, Carlo,Al-Saidi, Ghalib
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- Room temperature liquid porphyrins
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The syntheses of 5,10,15,20-tetrakis(3,4,5-trialkoxyphenyl)porphyrins, which exhibit fluid state behavior at room temperature, are reported. The thermal and rheological measurements indicate that they behave like liquid at 25 °C (298 K).
- Maruyama, Sumio,Sato, Kenta,Iwahashi, Hiroyuki
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supporting information; experimental part
p. 714 - 716
(2011/01/09)
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- Columnar mesophases and phase behaviors of novel polycatenar mesogens containing bi-1,3,4-oxadiazole
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A new series of liquid-crystalline bi-1,3,4-oxadiazole derivatives (2,2′-bis(3,4,5-trialkoxyphenyl)-bi-1,3,4-oxadiazole, BOXD-Tn, n=3, 4, 5, 6, 7, 8, 10, 14) were designed and synthesized. They have been confirmed to give rise to columnar mesophases. The
- Qu, Songnan,Li, Min
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p. 12429 - 12436
(2008/03/12)
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- Gallic esters of 4,5-dinitrocatechol as potential building blocks for thermotropic liquid crystals
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A series of unsubstituted and 1,4-disubstituted gallic catecholates 1, 6 and 7 as possible candidates for wedge-shaped mesogens were prepared starting from the respective benzene derivatives 2a-c and gallic esters 5a-h. The mesomorphic properties were inv
- Judele, Roxana,Laschat, Sabine,Baro, Angelika,Nimtz, Manfred
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p. 9681 - 9687
(2007/10/03)
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- Liquid crystals in the series of 2,4,6-tristyryl-1,3,5-triazines
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Alkaline condensation reactions of 2,4,6-trimethyl-1,3,5-triazine (1) and substituted benzaldehydes (2a-n) yield 2,4,6-tristyryl-1,3,5-triazines (3a-n). A sufficient number and length of the alkoxy chains at the benzene rings provide liquid crystalline ph
- Holst, Hans Christof,Pakula, Tadeusz,Meier, Herbert
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p. 6765 - 6775
(2007/10/03)
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- One-Dimensional Ion Transport in Self-Organized Columnar Ionic Liquids
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New fan-shaped ionic liquids forming columnar liquid crystalline phases have been prepared to obtain one-dimensional ion-transporting materials. The ionic liquids consist of two incompatible parts: an imidazolium-based ionic part as an ion-conducting part
- Yoshio, Masafumi,Mukai, Tomohiro,Ohno, Hiroyuki,Kato, Takashi
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p. 994 - 995
(2007/10/03)
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- Tailoring thermotropic cubic mesophases: Amphiphilic polyhydroxy derivatives
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Novel amphiphilic polyhydroxy compounds [N-(3,4-dialkoxybenzoyl)-1-amino-1-deoxy-D-glucitols (glucamides), N-(3,4-dialkoxybenzoyl)-1-deoxy-1-methylamino-D-glucitols, N-(3,4,5-trialkoxybenzoyl)-1-deoxy-1-methylamino-D-glucitols (N-methylgucamides), 1-benzo
- Borisch, Konstanze,Diele, Siegmar,Goering, Petra,Kresse, Horst,Tschierske, Carsten
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p. 529 - 543
(2007/10/03)
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