Faculty Publications

Now showing 1 - 4 of 4

Nonlinear optical studies on new conjugated poly{2,2 l-(3,4- dialkoxythiophene-2,5-diyl) bis[5-(2-thienyl)-1,3,4-oxadiazole]}s
(2010) Hegde, P.K.; Vasudeva Adhikari, A.V.; Manjunatha, M.G.; Suchand Sandeep, C.S.; Philip, R.
Three new donor-acceptor type poly{2,2 1-(3,4-dialkoxythiophene- 2,5-diyl)bis[5-(2-thienyl)-1,3,4-oxadiazole]}s (P1, P2, and P3) were synthesized starting from thiodiglycolic acid and diethyl oxalate through multistep reactions. The polymerization was carried out using chemical polymerization technique. The optical and charge-transporting properties of the polymers were investigated by UV-visible, fluorescence emission spectroscopic and cyclic voltammetric studies. The polymers showed bluish-green fluorescence in solutions. The electrochemical band gaps were determined to be 2.03, 2.09, and 2.17 eV for P1, P2, and P3, respectively. The nonlinear optical properties of new polymers were investigated at 532 nm using single beam Z-scan and degenerate four-wave mixing (DFWM) techniques with nanosecond laser pulses. The polymers exhibited strong optical limiting behavior due to "effective" three-photon absorption. Values of the effective three-photon absorption (3PA) coefficients, thirdorder nonlinear susceptibilities (? (3)), and figures (F) of merit were calculated. © 2010 Wiley Periodicals, Inc.
New Carbazole-Based Sensitizers for p-Type DSSCs: Impact of the Position of Acceptor Units on Device Performance
(American Chemical Society, 2022) Keremane, K.S.; Pellegrin, Y.; Planchat, A.; Jacquemin, D.; Odobel, F.; Vasudeva Adhikari, A.V.
We report the design, synthesis, and characterization of two new carbazole-based organic dyes PC1-2as potential sensitizers for NiO-based p-type dye-sensitized solar cells (p-DSSCs). The D-A-π-A' configured PC1dye comprises a thienyl unit as a π-spacer and a malononitrile as an end-capping acceptor unit, whereas in PC2the cyanovinylene group serves as an acceptor unit and a thienyl group acts as a donor unit in a D-A-D configuration. These molecules achieved excellent solubility due to their long-branched alkyl chains. The current work encompasses their structural, photophysical, thermal, electrochemical, theoretical, and photoelectrochemical studies, establishing structure-property relationships. PC1-2exhibit λabsand λemiin the range of 389-404 and 448-515 nm, respectively, with a band gap in the range of 2.88-2.92 eV. Electrochemical studies confirm the feasibility of electron injection, regeneration, and recombination. The introduction of an additional electron-withdrawing group (cyanovinylene group) on the dye PC1skeleton endows it with a higher dye loading capacity, high hole injection, and a strengthened intramolecular charge transfer (ICT) effect, resulting in a redshifted ICT absorption with a higher molar extinction coefficient. Among the two new dyes, the device based on PC1achieved the highest power conversion efficiency (PCE) of 0.027% with a short-circuit current density (JSC) of 1.29 mA·cm-2, open-circuit voltage (VOC) of 67 mV, and fill factor (FF) of 31%, whereas the device with dye PC2performed less efficiently (PCE: 0.018%, JSC: 0.92 mA·cm-2, VOC: 68 mV, and FF: 30%). Conclusively, the study provides insights into the intricacies involved in the structural modification of carbazole-based p-type dyads for the development of highly efficient DSSCs. © 2022 American Chemical Society. All rights reserved.
Meso-tris(2-furyl/2-thienyl) substituted porphyrin-ferrocene ‘click’ conjugates: synthesis, experimental, and computational studies
(Royal Society of Chemistry, 2024) Shet, S.N.; Patil, M.; Shetti, V.S.
The chemical synthesis of 5-(4-azidophenyl)-10,15,20-tris(2-furyl/2-thienyl)porphyrins and their utilization in a Cu(i) catalyzed alkyne-azide ‘click’ reaction (CuAAC) with ethynylferrocene to obtain the hitherto unknown meso-tris(2-furyl/2-thienyl) substituted porphyrin-ferrocene ‘click’ conjugates are reported. These new ‘click’ conjugates were studied along with the reference ‘click’ conjugates containing all-meso-aryl substituted porphyrins by experimental and computational methods. Compared to the reference, the new conjugates displayed red-shifted absorption/emission bands, easier porphyrin ring reduction, and an efficient photoinduced electron transfer (PET) process from ferrocene to a porphyrin unit. Density functional theory (DFT) calculations performed on these conjugates revealed a good correlation with the experimental results. © 2024 The Royal Society of Chemistry.
Porphyrin-azoheteroarenes: synthesis, photophysical, and computational studies
(Royal Society of Chemistry, 2025) Shet, S.N.; Bhat, V.G.; Swathi, S.G.; Udayakumar, U.; Shetti, V.S.
Azobenzenes (Ph-N = N-Ph) are well-known photochromic compounds with widespread applications. Replacing one or both phenyl rings of azobenzenes with heteroarenes leads to a new class of compounds known as azoheteroarenes (Het-N N-Ph/Het). Azoheteroarenes have gained attention as promising alternatives to traditional azobenzenes in the field of photopharmacology due to their ability to undergo photoswitching under visible light. Interestingly, the chemistry of porphyrin-containing azoheteroarenes has been underexplored. In this study, we present the synthesis of hitherto unknown hybrid molecules: porphyrin-azopyrroles (porphyrin-N N-pyrrole) and porphyrin-azoindoles (porphyrin-N N-indole), which also feature porphyrins with five-membered meso-substituents, such as 2-furyl and 2-thienyl groups. The porphyrin-azoheteroarenes with meso-tris(2-furyl/2-thienyl) substitutions demonstrate red-shifted absorption and emission bands, more significant Stokes shifts, and smaller optical bandgaps compared to hybrids containing only meso-aryl groups. Additionally, these porphyrin-azoheteroarenes exhibit higher fluorescence emission intensities than their corresponding precursor porphyrins. © 2025 The Royal Society of Chemistry.

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