Solvent Relaxation Accompanied Ultrafast Excited State Proton Transfer Dynamics Revealed in a Salicylideneaniline Derivative

Abstract

In this study, we have investigated the excited state intramolecular proton transfer (ESIPT) and subsequent dielectric relaxation of a newly synthesized Schiff base molecule in cyclohexane, methanol and SDS micelle through femtosecond fluorescence up‐conversion and broadband transient absorption spectroscopy. We found that the molecule showed ultrafast proton transfer with a timescale about 0.2 ps followed by solvent relaxation of the keto tautomer in methanol and SDS medium. In non‐polar cyclohexane, the solvation part was completely absent as expected. Computational study suggested the existence of a transition state in the proton transfer surface. Quantification of the system was done with two step model assigning the first rate constant to the relaxation of the excited state enol form and the second to the barrier crossing from the enol to the keto form.

Nature of Fast Relaxation Processes and Spectroscopy of a Membrane-Active Peptide Modified with Fluorescent Amino Acid Exhibiting Excited State Intramolecular Proton Transfer and Efficient Stimulated Emission

“…The specificity of ESIPT processes in chromophore structures was comprehensively described in the scientific literature − and can be used as a part of specially designed electronic mechanisms for amplified spontaneous emission, bulk heterojunction solar cells, color-specific photoswitching, light-emitting liquid crystal displays, thermally activated delayed fluorescence, and so forth. The dynamics of ESIPT phenomena is also an area of great interest, ,, and the nature of ultrafast and relatively long proton transfer processes was comprehensively investigated using transient absorption pump-probe spectroscopy, − upconverted and time-resolved fluorescence methods, , and femtosecond time-resolved resonance-enhanced multiphoton ionization and ion yield spectroscopy techniques. , …”

“…The specificity of ESIPT processes in chromophore structures was comprehensively described in the scientific literature 20−25 and can be used as a part of specially designed electronic mechanisms for amplified spontaneous emission, 26 bulk heterojunction solar cells, 27 color-specific photoswitching, 28 light-emitting liquid crystal displays, 29 thermally activated delayed fluorescence, 30 and so forth. The dynamics of ESIPT phenomena is also an area of great interest, 23,31,32 nature of ultrafast and relatively long proton transfer processes was comprehensively investigated using transient absorption pump-probe spectroscopy, 33−36 upconverted and time-resolved fluorescence methods, 37,38 and femtosecond timeresolved resonance-enhanced multiphoton ionization and ion yield spectroscopy techniques. 39,40 In this work, we present the synthesis and comprehensive investigation of linear steady-state and time-resolved photophysical properties, along with femtosecond transient absorption pump-probe spectroscopy of a new fluorescently labeled peptide 1, which exhibited the ESIPT phenomenon in liquid media at room temperature and efficient superluminescence under femtosecond pumping into the main absorption band.…”