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Dramatic Pressure-Dependent Quenching Effects in Supercritical CO2 Assessed by ...
Barroso, Mónica; Chattopadhyay, Nitin; Klymchenko, Andrey S.; Demchenko, Alexander P.; Arnaut, Luís G.; Formosinho, Sebastião J.Steady-state fluorescence of 4‘-dimethylamino-3-hydroxyflavone (DMA3HF) was observed in supercritical carbon dioxide (scCO2). Excited-state intramolecular proton transfer (ESIPT) occurs resulting in two well-separated emission bands corresponding to the normal and tautomer forms. As the scCO2 density exceeds 0.7 g/mL, the relative intensity of the two bands tends to a constant value, comparable to that observed...
Fluorescence from the second excited singlet state of 3-hydroxyflavone in super...
Chattopadhyay, Nitin; Barroso, Mónica; Serpa, Carlos; Arnaut, Luís G.; Formosinho, Sebastião J.Fluorescence from the second excited singlet state (S2) of 3-hydroxyflavone (3HF) has been observed for the first time in supercritical carbon dioxide (sc-CO2) environment. Steady-state experiments reveal that the intramolecular proton transfer is less effective from the S2 state of 3HF compared to that from the S1 state. ; http://www.sciencedirect.com/science/article/B6TFN-4BVP7G9-5/1/fe6fe6a663b47e1a622241...
Photophysics of 3-hydroxyflavone in supercritical CO2: a probe to study the mic...
Chattopadhyay, Nitin; Barroso, Mónica; Serpa, Carlos; Isilda Silva, M.; Arnaut, Luís G.; Formosinho, Sebastião J.The excitation of 3-hydroxyflavone (3HF) to its second excited singlet state (S2) gives rise to dual fluorescence in supercritical carbon dioxide. The ultraviolet fluorescence originated from the S2 state of 3HF is well separated from the green emission emanating from the tautomeric form, produced via the excited state intramolecular proton transfer. The relative intensity of the S2 to the tautomer fluorescence...
Vibrational spectrum and molecular structure of triphenylamine monomer: A combi...
Reva, Igor; Lapinski, Leszek; Chattopadhyay, Nitin; Fausto, RuiTheoretical optimization of triphenylamine geometry, carried out at DFT(B3LYP) level using 6-31G** and aug-cc-pVDZ basis sets, predicted a propeller-like structure of the compound with D3 overall symmetry. In this structure, the central NCCC atoms are coplanar and the phenyl rings are symmetrically twisted from this plane by 41.5° (6-31G**) or 41.6° (aug-cc-pVDZ). The experimental FTIR spectrum of triphenylamin...
Rotamerisation and intramolecular proton transfer of 2-(2'-hydroxyphenyl)oxazol...
Purkayastha, Pradipta; Chattopadhyay, NitinSemi-empirical (AM1-SCI) calculations have been performed on 2-(2'-hydroxyphenyl)oxazole (HPO), 2-(2'-hydroxyphenyl)imidazole (HPI) and 2-(2'-hydroxyphenyl)thiazole (HPT) to rationalise the photophysical behaviour of the compounds exhibiting intramolecular rotation as well as excited state intramolecular proton transfer (ESIPT). The calculations reveal that there is a gradual variation in the properties from HP...
Photoisomerization of p-(Dimethylamino)-β-chlorostyrene: A Low Temperature Matr...
Chattopadhyay, Nitin; Reva, Igor; Lapinski, Leszek; Lapinski, Leszek; Fausto, Rui; Arnaut, Luís G.; Formosinho, Sebastião J.The low-temperature matrix isolation technique in combination with FTIR spectroscopy, has been used to study the trans−cis photoisomerization of p-(dimethylamino)-β-chlorostyrene (DMACS). The highly dominant form of the compound immediately after deposition in argon matrix has been identified, by comparison of its experimental infrared spectrum with that calculated at the DFT(B3LYP)/6-31G** level, as the trans ...
Benzil fluorescence and phosphorescence emissions: a pertinent probe for the ki...
Chattopadhyay, Nitin; Serpa, Carlos; Isilda Silva, M.; Arnaut, Luis G.; Formosinho, Sebastião J.http://www.sciencedirect.com/science/article/B6TFN-442NX70-4/1/6cf7b64b08fb1d9b37e33a23b914653f
Intramolecular Charge Transfer of p-(Dimethylamino)benzethyne: A Case of Nonfl...
Chattopadhyay, Nitin; Serpa, Carlos; Pereira, Mariette M.; Melo, J. Seixas de; Arnaut, Luis G.; Formosinho, Sebastião J.The effect of solvent polarity and external heavy atom on the steady state and time-resolved fluorescence properties of the locally excited (LE) state of p-(dimethylamino)benzethyne (DMABE) has been studied. It has been observed that in less polar environments, intersystem crossing (ISC) is the main nonradiative channel of deactivation for the excited species. However, at higher solvent polarity (ET(30) ≥ 44) t...
Effect of cyclodextrin encapsulation on the photocyclization of diphenylamine: ...
Sur, Debjani; Purkayastha, Pradipta; Bera, Subhash Chandra; Chattopadhyay, NitinThe kinetics of the photocyclization of diphenylamine (DPA) to carbazole (CAZL) has been studied fluorometrically in air-equilibrated aqueous solution as well as in constrained microheterogeneous media provided by [alpha]-, [beta]-, and [gamma]- cyclodextrins (CDs). It is observed that the fluorophore is embedded within the CD cavities without any alteration of the overall reaction quantum yield in the differen...
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