Photo-stability of peptide-bond aggregates: N-methylformamide dimers

2014 ◽  
Vol 16 (35) ◽  
pp. 18877-18887 ◽  
Author(s):  
Rachel Crespo-Otero ◽  
Artur Mardykov ◽  
Elsa Sanchez-Garcia ◽  
Wolfram Sander ◽  
Mario Barbatti
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Peptide Bond ◽  
Fast Proton ◽  
Photo Stability ◽  
Hydrogen Bonded

Fast proton-transfer in the excited state protects hydrogen-bonded N-methylformamide dimers from photo-dissociation in contrast to the monomer photochemistry.

Excited-State Intramolecular Proton Transfer in Polymers

1995 ◽  
Vol 413 ◽  
Author(s):  
Richard M. Tarkka ◽  
Samson A. Jenekhe
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Main Chain ◽  
Intramolecular Proton Transfer ◽  
Polymer Structure ◽  
Laser Dyes ◽  
Excimer Formation ◽  
Photochromic Materials ◽  
Hydrogen Bonded

ABSTRACTExcited state intramolecular proton transfer (ESIPT) has been demonstrated in new intramoleculary hydrogen bonded (IHB) polymers of interest as photostabilizers, triplet quenchers, photochromic materials, laser dyes and electroluminescent materials. The new IHB polymers containing the 2-(2-hydroxyphenyl)benzoxazole moiety in the main chain were used to explore the effects of polymer structure, extended conjugation and competition with excimer formation on the ESIPT process. It was found that polymer structure, and particularly extent of conjugation, affects an IHB polymer's ability to exhibit ESIPT.

A TDDFT study on the excited-state double proton transfer reaction of 8-hydroxyquinoline along a hydrogen-bonded bridge

2017 ◽  
Vol 41 (16) ◽  
pp. 8437-8442 ◽  
Author(s):  
Yu-Hui Liu ◽  
Shi-Ming Wang ◽  
Chaoyuan Zhu ◽  
Sheng Hsien Lin
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Transfer Reaction ◽  
Proton Transfer Reaction ◽  
Double Proton Transfer ◽  
Hydrogen Bonded

The mechanism of excited-state multiple proton transfer reaction is demonstrated to be controlled by a hydrogen-bonded bridge.

scholarly journals Proton Transfer from a Photoacid to Water: First Principles Simulations and Fast Fluorescence Spectroscopy

2021 ◽  
Author(s):  
Alice R. Walker ◽  
Boning Wu ◽  
Jan Meisner ◽  
Michael D. Fayer ◽  
Todd J. Martinez
Keyword(s):  
Molecular Dynamics ◽  
Excited State ◽  
Fluorescence Spectroscopy ◽  
Proton Transfer ◽  
Ab Initio ◽  
Time Constant ◽  
Emission Wavelength ◽  
Ab Initio Molecular Dynamics ◽  
Long Distance ◽  
Hydrogen Bonded

Proton transfer reactions are ubiquitous in chemistry, especially in aqueous solutions. We investigate photo-induced proton transfer between the photoacid 8-hydroxypyrene-1,3,6- trisulfonate (HPTS) and water using fast fluorescence spectroscopy and ab initio molecular dynamics simulations. Photo-excitation causes rapid proton release from the HPTS hydroxyl. Previous experiments on HPTS/water described the progress from photoexcitation to proton diffusion using kinetic equations with two time constants. The shortest time constant has been interpreted as protonated and photoexcited HPTS evolving into an “associated” state, where the proton is “shared” between the HPTS hydroxyl and an originally hydrogen bonded water. The longer time constant has been interpreted as indicating evolution to a “solvent separated” state where the shared proton undergoes long distance diffusion. In this work, we refine the previous experimental results using very pure HPTS. We then use excited state ab initio molecular dynamics to elucidate the detailed molecular mechanism of aqueous excited state proton transfer in HPTS. We find that the initial excitation results in rapid rearrangement of water, forming a strong hydrogen bonded network (a “water wire”) around HPTS. HPTS then deprotonates in ≤3 ps, resulting in a proton that migrates back and forth along the wire before localizing on a single water molecule. We find a near linear relationship between emission wavelength and proton-HPTS distance over the simulated time scale, suggesting that emission wavelength can be used as a ruler for proton distance. Our simulations reveal that the “associated” state corresponds to a water wire with a mobile proton and that the diffusion of the proton away from this water wire (to a generalized “solvent-separated” state) corresponds to the longest experimental time constant.

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