Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
4 results
Search Results
Item Photophysical and electrochemical properties of organic molecules: Solvatochromic effect and DFT studies(Elsevier B.V., 2018) Mohan, M.; Pangannaya, S.; Satyanarayan, M.N.; Trivedi, D.R.A series of five Schiff base molecules M1, M2, M3, M4 and M5 have been designed and synthesized by aldol condensation reaction. Synthesized molecules have been characterized by standard spectroscopic techniques in order to confirm their structural traits. The solvatochromic behavior of molecules M1 to M5 in solvents of varying polarity were investigated by UV–Vis, fluorescence spectroscopy and supported by TD-DFT calculations. DFT studies performed in the gas phase confirmed the energy stabilized structure of the molecules M1 to M5. Structural characteristics of molecule M2 favored higher fluorescence emission with a quantum yield of 0.35 and a solid-state emission of 512 nm. Fluorescence lifetime measurement of the molecules M1 to M5 exhibited a lifetime of order 2–5 ns. Overall, molecule M2 can find its application in organic light emitting diodes as a non-dopant emitter material. © 2018 Elsevier B.V.Item Functionalized pyrene-based AIEgens: synthesis, photophysical characterization and density functional theory studies(John Wiley and Sons Ltd, 2019) Mohan, M.; James, J.; Satyanarayan, M.N.; Trivedi, D.Three new pyrene-based derivatives P1, P2 and P3 with a substituted pyrazole were designed, synthesized and characterized using standard spectroscopic techniques. Ultraviolet–visible (UV–vis) spectroscopic studies for P1–P3 uncovered a finite bathochromic shift of the molecules in solvents of varying polarity. Photoluminescence (PL) studies revealed the significant fluorescence emission of all molecules in higher polar solvents such as MeOH and dimethylformamide (DMF). Fluorescence quantum yield studies demonstrated the importance of P3 possessing cyanofunctionality for imparting higher emission with a quantum yield of 0.36%. Ratiometric studies performed in a tetrahydrofuran (THF)/H2O mixture indicated fluorescence enhancement with increasing overall percentage of water, confirming the aggregation-induced emission effect. Cyclic voltammetry study of molecules P1–P3 revealed an irreversible oxidation peak and the band gaps were calculated to be 2.26 eV for P1 and 2.31 eV for P2 and P3 respectively. Density functional theory (DFT) studies performed on molecules P1–P3 validate the structure correlation of the molecules. Theoretically estimated highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) and bandgap correlated well with the experimental values. Furthermore, time-dependent (TD)DFT showed that the major contribution for the electronic transitions occurring in the system was governed by HOMO-1 and LUMO+1 orbitals. © 2019 John Wiley & Sons, Ltd.Item Design, Synthesis and Characterization of N-Substituted Heteroaromatics: DFT-Studies and Organic Light Emitting Device Application(Wiley-Blackwell info@wiley.com, 2020) Mohan, M.; John, R.; Satyanarayan, M.N.; Trivedi, D.R.Schiff's base condensation of 4,5-Dimethyl-1,2-phenylenediamine with various aldehydes namely fluorene-2-carboxaldehyde (MBF), N-ethyl-3-carboxaldehyde (MBE), 8-hydroxyjulolidine-9-carboxaldehyde (MBJ) and N-(4-formylphenyl) carbazole (MBB) functioning as light emitters have been synthesized. Solid-state emission reveals the exhibition of variant fluorescent color achieved by mere variation in the peripheral group attached to the core. Amongst the designed system, MBB showed a solid-state blue light emission with its emission peak centered at 453 nm. The fluorescence quantum yield of MBB displayed value of 44.82% in the solution state. Electrochemical studies on MBB estimated a HOMO energy level at ?5.7 eV and LUMO at ?3.2 eV. OLED realized with MBB as an active emitter material was successful in the generation of bluish-green emission with a maximum brightness of 280 cd/m2. Current efficiency of 2 cd/A and a power efficiency of 0.18 lm/W was observed for the fabricated device. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, WeinheimItem Design and Synthesis of New Bithiophene Based Planar AIE Red Light Emitters: A Detailed Theoretical and Experimental Analysis**(John Wiley and Sons Inc, 2022) Mohan, M.; Satyanarayan, M.N.; Trivedi, D.R.Bithiophene core with −CN substituted pyrazole and imidazole side chains yielding B1, B2, and B3 have been designed and synthesized viz Schiff's base condensation reaction. Molecules, at their solid-state exhibited red-light emission supporting AIE mechanism. The series exhibited the highest relative quantum yield of value 18.66 % by B1 with the lowest recorded for B3 exhibiting 2.4 %. DFT results reveal the synthesized molecules at their optimized ground state adopt a planar structure. Theoretical calculation further validates the molecules to adopt a slip-stacking type of molecular packing arrangement at its condensed state, conducive for AIE. A large π-π stacking distance between the lattice plane of 3.4 Å, 3.6 Å and 3.5 Å possessed by B1, B2, and B3 respectively, favors AIE. Computational calculation on electron and hole reorganization energy reveals the effective role of two −CN groups in altering the hole mobility in comparison with the other molecules in the series. © 2022 Wiley-VCH GmbH.