Browsing by Author "Fernandes, P.P."

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Functionalized 1,3-dipyrrolyl-1,3-diketone difluoroboron complexes
(Royal Society of Chemistry, 2025) Shenoy, A.M.; Fernandes, P.P.; Lakshmi, V.
BF2 complexes of 1,3-dipyrrolyl-1,3-diketones are highly emissive compounds and well known to be ?-electronic anion-responsive systems because of their role in the formation of ion-pair assemblies. Despite their impressive electronic properties, their broader potential remains unexplored. Here, we synthesized a series of novel mono-functionalized ?-electronic BF2 complexes of 1,3-dipyrrolyl-1,3-diketones. Controlled functionalization was achieved by selectively introducing formyl, iodo, nitro and amine groups at the ?-position of the unsubstituted pyrrole of 1,3-dipyrrolyl-1,3-diketone BF2 complexes. Single crystal X-ray diffraction studies of compounds 2 and 4 provided definitive evidence of their molecular structures and confirmed selective functionalization. Detailed photophysical and electrochemical studies revealed the alteration of electronic properties through the choice of functional groups as evidenced by distinct absorption and emission profiles. Furthermore, DFT calculations complemented the experimental findings by providing insights into the bandgap energies and molecular stability of the compounds. These functionalized BF2 complexes represent valuable building blocks for developing new derivatives with applications spanning organic electronics, bioimaging, and chemosensors. © 2025 The Royal Society of Chemistry.
ortho-Halogen functionalized N-squaraines: structure–property relationship and dual-mode colorimetric and fluorometric sulfide ion detection
(Royal Society of Chemistry, 2025) Fernandes, P.P.; Shenoy, A.M.; Grover, V.; Veeranagaiah, N.S.; Lakshmi, V.
Symmetric ortho-halogen derivatives of anilinium N-squaraines were synthesized and characterized using 1H-NMR, mass, FT-IR, and single-crystal X-ray diffraction techniques. The effect of halogen substituents (–F, –Cl, –Br, –I) on the optoelectronic and electrochemical properties of N-squaraines has been thoroughly investigated. Additionally, the theoretical calculations demonstrated that the ortho functionalization slightly lowers the HOMO–LUMO energy band gap, which aligns with the optical band gap. Moreover, the solid-state photophysical characterization revealed that the photo-excited state remains a singlet, even in the presence of heavy atoms like bromine and iodine. The solid-state fluorescence emission was also significantly higher than in the solution state, with the quantum yields soaring up to 24%. Further, the two acidic binding sites in the synthesized compounds 2–5 were evaluated for anion sensing. The o-halo-derivatives act as selective dual-mode colorimetric and “Turn-On” fluorometric chemosensors for sulfide anions, with the solution changing from colorless to yellow and a four-fold enhanced emission intensity. Furthermore, adding acid makes the solution turn colorless again, as investigated in detail using the o-chloro-derivative. The chemosensor displayed good reversibility for up to seven cycles and demonstrated applications in molecular logic gates. This journal is © The Royal Society of Chemistry, 2025