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Author Sahoo, Dibakar ♦ Bhattacharya, Prosenjit ♦ Chakravorti, Sankar
Source IACS Kolkata
Content type Text
Publisher American Chemical Society
File Format PDF
Language English
Subject Domain (in DDC) Natural sciences & mathematics ♦ Chemistry & allied sciences ♦ Technology ♦ Chemical engineering
Subject Keyword Negative Solvatochromism ♦ Polarity ♦ Hydrogen Bonding ♦ Quinolium Dye ♦ Photophysics ♦ Information and Communication Technology ♦ Time-resolved emission ♦ Quantum Chemical Calculations ♦ DASQMI ♦ dimethyl sulfoxide (DMSO) ♦ polarizable continuum model (PCM) ♦ 2-[4-(dimethylamino) styryl]-1-methylquinolinium iodide
Abstract Photophysics of the 2-[4-(dimethylamino)styryl]-1-methylquinolinium iodide (DASQMI) molecule hasbeen studied in different solvents by steady-state and timeresolvedemission spectroscopy and also with quantum chemicalcalculations. The probe molecule exhibits a strong solventpolarity-dependent characteristic. The low-energy fluorescenceband of DASQMI shows an anomalous 40 nm blue shift inwater from that in dimethyl sulfoxide (DMSO); though indeuterium oxide the normal trend of red shift was observed. Amarked increase in intensity of this band at 77 K and an increasein lifetime in viscous solvent point clearly to the intramolecularcharge-transfer (ICT) character of the low-energy band. Fromthe temperature-dependent emission and emission spectra inmixed solvents, the negative solvatochromism of DASQMI has been established, which means that the ICT state moves towardground state with polarity and hydrogen-bond ability and beyond a critical dielectric constant coupled with protic nature of thesolvent ground state gets further stabilized to show anomalous blue shift. In ethanol, below a critical temperature, 253 K, a blue shiftstarts due to greater solvent molecular polarization. A third long-lifetime component with dominant 75% amplitude was observedonly in aqueous solution and may be due to the cis-isomer of hydrophobic DASQMI, a stable form in the excited state predictedfrom polarizable continuum model (PCM) calculations in water with 6-31G+(d,p) as basis set.
Education Level UG and PG
Learning Resource Type Article
Journal J Phys Chem B
Volume Number 115
Page Count 7
Starting Page 10983
Ending Page 10989