Browsing by Author "Vinayakumara, D.R."

Now showing 1 - 14 of 14

Columnar self-assembly of novel benzylidenehydrazones and their difluoroboron complexes: Structure-property correlations
(2019) Vinayakumara, D.R.; Swamynathan, K.; Kumar, S.; Adhikari, A.V.
Organoboron complexes are considered to be an important class of optically dynamic materials and because of their imperative properties, they have been unceasingly studied in a wide range of scientific areas. In this context, a new family of D-A-D? architectured boron difluoride complexes FB1-4 derived from arylhydrazones HZ1-4 has been synthesized and characterized. The work also deliberates detailed studies on their thermal, self-assembling and optoelectronic properties with respect to structural modifications. The systematic studies reveal that the new arylhydrazone ligands and their BF2 complexes exhibit a prospective columnar mesomorphism with different 2D lattice geometries at room temperature, owing to their critical structural features. Interestingly, an unusual morphological cross-over from a columnar hexagonal to rectangular mesophase has been confirmed in one of the investigated pseudo-discoidal boron complexes, FB4. The optoelectronic studies showcased their ICT dominating dye properties. Finally, the experimental results have been consciously correlated with quantum chemical simulations. 2019 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Columnar self-assembly of novel benzylidenehydrazones and their difluoroboron complexes: Structure-property correlations
(Royal Society of Chemistry, 2019) Vinayakumara, D.R.; Swamynathan, K.; Kumar, S.; Vasudeva Adhikari, A.V.
Organoboron complexes are considered to be an important class of optically dynamic materials and because of their imperative properties, they have been unceasingly studied in a wide range of scientific areas. In this context, a new family of D-A-D? architectured boron difluoride complexes FB1-4 derived from arylhydrazones HZ1-4 has been synthesized and characterized. The work also deliberates detailed studies on their thermal, self-assembling and optoelectronic properties with respect to structural modifications. The systematic studies reveal that the new arylhydrazone ligands and their BF2 complexes exhibit a prospective columnar mesomorphism with different 2D lattice geometries at room temperature, owing to their critical structural features. Interestingly, an unusual morphological cross-over from a columnar hexagonal to rectangular mesophase has been confirmed in one of the investigated pseudo-discoidal boron complexes, FB4. The optoelectronic studies showcased their ICT dominating dye properties. Finally, the experimental results have been consciously correlated with quantum chemical simulations. © 2019 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Hydrogen bond-driven columnar self-assembly of electroluminescent D-A-D configured cyanopyridones
(2018) Vinayakumara, D.R.; Ulla, H.; Kumar, S.; Pandith, A.; Satyanarayan, M.N.; Rao, D.S.S.; Prasad, S.K.; Adhikari, A.V.
Herein, we report the design and synthesis of a new series of flying bird-shaped liquid crystalline (LC) cyanopyridone derivatives with a D-A-D architecture, CPO-1 to CPO-4. Their mesomorphic, photophysical, electrochemical, and electroluminescence characteristics have been investigated in detail. Here, the H-bonding interactions through a central lactam core were shown to be the key driving force for their self-assembly into columnar mesophases. The key role of H-bonding has been confirmed by using newly synthesized similar shaped compounds, MCP-1 to MCP-3. New CPO mesogens were found to be intense greenish blue light emitters with narrow band-gap energies. Conclusions were drawn based on theoretical studies also. Finally, the application potential of the selected mesogen CPO-2 as an emissive material has been demonstrated for the fabrication of doped and non-doped OLED devices with different device architectures, which displayed encouraging results. In fact, this is the first report on the use of emissive H-bond-assisted columnar liquid crystals in devices. The present results provide a new guideline and a versatile approach to the design of new LC molecules for the fabrication of efficient OLEDs. 2018 The Royal Society of Chemistry.
Hydrogen bond-driven columnar self-assembly of electroluminescent D-A-D configured cyanopyridones
(Royal Society of Chemistry, 2018) Vinayakumara, D.R.; Ulla, H.; Kumar, S.; Pandith, A.; Satyanarayan, M.N.; Shankar Rao, D.S.S.; Prasad, S.K.; Vasudeva Adhikari, A.
Herein, we report the design and synthesis of a new series of flying bird-shaped liquid crystalline (LC) cyanopyridone derivatives with a D-A-D architecture, CPO-1 to CPO-4. Their mesomorphic, photophysical, electrochemical, and electroluminescence characteristics have been investigated in detail. Here, the H-bonding interactions through a central lactam core were shown to be the key driving force for their self-assembly into columnar mesophases. The key role of H-bonding has been confirmed by using newly synthesized similar shaped compounds, MCP-1 to MCP-3. New CPO mesogens were found to be intense greenish blue light emitters with narrow band-gap energies. Conclusions were drawn based on theoretical studies also. Finally, the application potential of the selected mesogen CPO-2 as an emissive material has been demonstrated for the fabrication of doped and non-doped OLED devices with different device architectures, which displayed encouraging results. In fact, this is the first report on the use of emissive H-bond-assisted columnar liquid crystals in devices. The present results provide a new guideline and a versatile approach to the design of new LC molecules for the fabrication of efficient OLEDs. © 2018 The Royal Society of Chemistry.
New cyanopyridone-based unsymmetrical dyads: The effect of donor strength on their optoelectronic properties
(2019) Vinayakumara, D.R.; Kesavan, R.; Kumar, S.; Adhikari, A.V.
Herein, we describe the design, synthesis and optoelectronic characterization of a new series of highly fluorescent dyes configured with a D-A-D? architecture, viz. CP1 to CP7. In the new molecular design, various electron-donating scaffolds were integrated with an efficient electron-accepting trialkoxyphenyl-substituted cyanopyridone moiety to study the effect of donor strength on their thermal and opto-physical properties. A detailed investigation of their thermal properties reveals that they are thermally robust with high melting and decomposition temperatures. Furthermore, in-depth photophysical studies expose their remarkable fluorescence ability in both solution and aggregated state within a wide spectral range from blue to orange. Evidently, among all the fluorophores, dyads bearing amino donors were found to be highly intense emitters due to their superior donating strength. Furthermore, solvatochromic studies showcase their ICT-dominated optoelectronic properties and it was confirmed by different correlation studies. Finally, the experimental results were correlated with their quantum chemical simulation data. 2019 The Royal Society of Chemistry and Owner Societies.
New cyanopyridone-based unsymmetrical dyads: The effect of donor strength on their optoelectronic properties
(Royal Society of Chemistry, 2019) Vinayakumara, D.R.; Kesavan, R.; Kumar, S.; Vasudeva Adhikari, A.V.
Herein, we describe the design, synthesis and optoelectronic characterization of a new series of highly fluorescent dyes configured with a D-A-D? architecture, viz. CP1 to CP7. In the new molecular design, various electron-donating scaffolds were integrated with an efficient electron-accepting trialkoxyphenyl-substituted cyanopyridone moiety to study the effect of donor strength on their thermal and opto-physical properties. A detailed investigation of their thermal properties reveals that they are thermally robust with high melting and decomposition temperatures. Furthermore, in-depth photophysical studies expose their remarkable fluorescence ability in both solution and aggregated state within a wide spectral range from blue to orange. Evidently, among all the fluorophores, dyads bearing amino donors were found to be highly intense emitters due to their superior donating strength. Furthermore, solvatochromic studies showcase their ICT-dominated optoelectronic properties and it was confirmed by different correlation studies. Finally, the experimental results were correlated with their quantum chemical simulation data. © 2019 The Royal Society of Chemistry and Owner Societies.
New fluorescent columnar mesogens derived from phenanthrene-cyanopyridone hybrids for OLED applications
(2018) Vinayakumara, D.R.; Ulla, H.; Kumar, S.; Satyanarayan, M.N.; Adhikari, A.V.
We report the design, synthesis, and self-assembly of a novel series of pseudodiscoid dyads comprising electron-rich dialkoxyphenanthrene and trialkoxyphenyl rings appended to an electron-deficient cyanopyridone core. Evidently, all the members of the series exhibited bi-mesophases with prospective columnar mesomorphism; moreover, it was steady under ambient conditions. The electro-optical studies revealed that the new liquid crystalline materials were efficient green light emitters both in solution and LC states with substantial chromaticity. Further, their theoretical studies (DFT) revealed that the molecules possess good intramolecular charge transport behavior. These superior properties of the LC materials render them to become promising candidates for OLED applications. Their electroluminescence competence was studied by fabricating doped and non-doped simple-architecture OLED devices. One of the doped devices with Py-2 as the emissive layer exhibits the highest deep-green electroluminescence with a brightness of 1898 cd m-2 at 4.23 V having CIE coordinates of (0.312, 0.606). 2018 the Partner Organisations.
New fluorescent columnar mesogens derived from phenanthrene-cyanopyridone hybrids for OLED applications
(Royal Society of Chemistry, 2018) Vinayakumara, D.R.; Ulla, H.; Kumar, S.; Satyanarayan, M.N.; Vasudeva Adhikari, A.V.
We report the design, synthesis, and self-assembly of a novel series of pseudodiscoid dyads comprising electron-rich dialkoxyphenanthrene and trialkoxyphenyl rings appended to an electron-deficient cyanopyridone core. Evidently, all the members of the series exhibited bi-mesophases with prospective columnar mesomorphism; moreover, it was steady under ambient conditions. The electro-optical studies revealed that the new liquid crystalline materials were efficient green light emitters both in solution and LC states with substantial chromaticity. Further, their theoretical studies (DFT) revealed that the molecules possess good intramolecular charge transport behavior. These superior properties of the LC materials render them to become promising candidates for OLED applications. Their electroluminescence competence was studied by fabricating doped and non-doped simple-architecture OLED devices. One of the doped devices with Py-2 as the emissive layer exhibits the highest deep-green electroluminescence with a brightness of 1898 cd m-2 at 4.23 V having CIE coordinates of (0.312, 0.606). © 2018 the Partner Organisations.
Optoelectronic exploration of novel non-symmetrical star-shaped discotic liquid crystals based on cyanopyridine
(2018) Vinayakumara, D.R.; Swamynathan, K.; Kumar, S.; Adhikari, A.V.
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. 2018 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Optoelectronic exploration of novel non-symmetrical star-shaped discotic liquid crystals based on cyanopyridine
(Royal Society of Chemistry, 2018) Vinayakumara, D.R.; Swamynathan, K.; Kumar, S.; Vasudeva Adhikari, A.
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. © 2018 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Self-assembly of taper- and wedge-shaped maleimide derivatives: Synthesis and structure-property relationship
(2019) Vinayakumara, D.R.; Kumar, S.; Prasad, S.K.; Adhikari, A.V.
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. 2019
Self-assembly of taper- and wedge-shaped maleimide derivatives: Synthesis and structure-property relationship
(Elsevier B.V., 2019) Vinayakumara, D.R.; Kumar, S.; Prasad, S.K.; Vasudeva Adhikari, A.V.
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. © 2019
Supramolecular columnar self-assembly of wedge-shaped rhodanine based dyes: Synthesis and optoelectronic properties
(2019) Vinayakumara, D.R.; Kumar, S.; Adhikari, A.V.
The development of small ?-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 series of wedge-shaped rhodanine derivatives with D-A configuration, viz. RA1 RA5. Their LC properties were studied by employing DSC, POM and XRD techniques. The mesophase behavior was investigated as a function of chain length, density and position of alkoxy terminals to understand structure-property relationship. Interestingly, the longer chain analog, i.e. RA3 demonstrated H-bonded disc-like macrocyclic structures, causing an imperative columnar hexagonal phase at ambient temperature. Further, their photophysical and electrochemical properties were evaluated. They showed a good dye property attributing to effective intramolecular interactions, as confirmed by experimental and theoretical studies. Conclusively, RA3 has been considered to be a potential candidate for its application in organic electronics. 2018
Supramolecular columnar self-assembly of wedge-shaped rhodanine based dyes: Synthesis and optoelectronic properties
(Elsevier B.V., 2019) Vinayakumara, D.R.; Kumar, S.; Vasudeva Adhikari, A.V.
The development of small ?-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 series of wedge-shaped rhodanine derivatives with D-A configuration, viz. RA1–RA5. Their LC properties were studied by employing DSC, POM and XRD techniques. The mesophase behavior was investigated as a function of chain length, density and position of alkoxy terminals to understand structure-property relationship. Interestingly, the longer chain analog, i.e. RA3 demonstrated H-bonded disc-like macrocyclic structures, causing an imperative columnar hexagonal phase at ambient temperature. Further, their photophysical and electrochemical properties were evaluated. They showed a good dye property attributing to effective intramolecular interactions, as confirmed by experimental and theoretical studies. Conclusively, RA3 has been considered to be a potential candidate for its application in organic electronics. © 2018