This paper is a density functional theory (DFT) calculation of intramolecular proton transfer (IPT) in 6-hydroxypicolinic acid (6HPA, 6-hydroxypyridine-2-carboxylic acid) tautomeric forms. The transition state for the enol-to-keto transition is reported in the gas phase and in four different solvents. The planar and non-planar dimer forms of 6HPA keto and enol, respectively, were also studied i...

Photophysics of 2-hydroxy-1-naphthaldehyde semicarbazone (2HNS) and the corresponding thiosemicarbazone (2HNT) are explored in n-heptane and methanol as solvents, focusing on the intramolecular proton transfer (IPT) in the ground (S0) and the first excited singlet (S1) states using absorption, steady state and time-resolved fluorometric techniques. The feasibility of the IPT process in the two ...

this paper is a density functional theory (dft) calculation of intramolecular proton transfer (ipt) in 6-hydroxypicolinic acid (6hpa, 6-hydroxypyridine-2-carboxylic acid) tautomeric forms. the transition state for the enol-to-keto transition is reported in the gas phase and in four different solvents. the planar and non-planar dimer forms of 6hpa keto and enol, respectively, were also studied i...

The Intramolecular Proton Transfer (IPT) in alkoxyamines is one of the main factors determining the process of Nitroxide Mediated Polymerization (NMP). Recently, we proposed an experimental approach to study IPT and applied it to a series of alkoxyamines. It was found that IPT dramatically depends on the structure of the alkoxyamine, but it was not clear which factors are significant for IPT (M...

Using the freon mixture CDF(3)/CDClF(2) as solvent we have been able to measure the (1)H and (15)N NMR spectra of the doubly (15)N labeled 2,2'-bipyridinium cation (BpyH(+)) at temperatures down to 115 K. The obtained NMR parameters strongly depend on the type of counteranions indicating the formation of ion pairs. In the case of the bulky poorly coordinating tetrakis[3,5-bis(trifluoromethyl)ph...

We have developed for fuel cells a novel proton exchange membrane (PEM) using inorganic phosphotungstic acid (HPW) as proton carrier and mesoporous silica as matrix (HPW-meso-silica) . The proton conductivity measured by electrochemical impedance spectroscopy is 0.11 S cm(-1) at 90 °C and 100% relative humidity (RH) with a low activation energy of ∼14 kJ mol(-1). In order to determine the energ...

We report the experimental determination of the intramolecular enol-enol tautomerization rate of an unsymmetric β-diketone, benzoylacetone, with femtosecond transient absorption in the ultraviolet. Initially, there is an equilibrium of two possible enolic structures in solution, which is disturbed upon UV excitation by exciting a disproportionate fraction of one enolic form. Comparison to symme...

Channelrhodopsins serve as photoreceptors that control the motility behavior of green flagellate algae and act as light-gated ion channels when heterologously expressed in animal cells. Here, we report direct measurements of proton transfer from the retinylidene Schiff base in several channelrhodopsin variants expressed in HEK293 cells. A fast outward-directed current precedes the passive chann...