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The ability of phenol to transfer a proton to surrounding ammonia molecules in a phenol-(ammonia) n cluster depends on the relative orientation of ammonia molecules, and a critical field of about 285 MV cm -1 is essential along the O-H bond for the proton-transfer process. Ab initio MD simulations reveal that the proton-transfer process from phenol to ammonia cluster is spontaneous when the cluster has at least eight ammonia molecules, and the proton-transfer event is almost instantaneous (about 20-120 fs). These simulations also reveal that the rate-determining step for the proton-transfer process is the reorganization of the solvent around the OH group. During the solvent reorganization process, the fluctuations in the solvent occur until a particular set of configurations projects the field in excess of the critical electric field along the O-H bond which drives the proton-transfer process. Further, the proton-transfer process follows a curvilinear path which includes the O-H bond elongation and out-of-plane movement of the proton and can be referred to as a "bend-to-break" process.

In the past decades, tremendous efforts have been invested into organic molecules involved in the excited-state intramolecular proton transfer (ESIPT) reaction due to their enormously Stokes-shifted fluorescence and distinctive photophysical properties. The alterations of the environmental medium can effectively adjust the luminous performance of ESIPT molecules, which inspires us to unravel the solvent effect on the ESIPT mechanism. Here, we report the solvent-dependent excited-state properties of two new seven-membered ring pyrrole-indole ESIPT molecules, g -PPDBI , by steady-state spectra, picosecond transient fluorescence spectra, femtosecond transient absorption spectra, and theoretical calculations. The bathochromic-shifted normal fluorescence and the negligibly shifted tautomer fluorescence suggest the occurrence of an excited-state intramolecular proton-coupled charge transfer reaction. Thus, the solvent effect plays a vital role in stabilizing the intramolecular charge transferred state, resulting in a higher ESIPT reaction barrier in more polar solvents. Additionally, the observation of the slight dynamic difference between e -PPDBI , by steady-state spectra, picosecond transient fluorescence spectra, femtosecond transient absorption spectra, and theoretical calculations. The bathochromic-shifted normal fluorescence and the negligibly shifted tautomer fluorescence suggest the occurrence of an excited-state intramolecular proton-coupled charge transfer reaction. Thus, the solvent effect plays a vital role in stabilizing the intramolecular charge transferred state, resulting in a higher ESIPT reaction barrier in more polar solvents. Additionally, the observation of the slight dynamic difference between PPDBIs with different π-conjugation positions provides a new strategy to adjust the performance of ESIPT molecules.

The excited-state intramolecular proton transfer (ESIPT) of 4'- N , N -dialkylamino-3-hydroxyflavone (C n HF) having different alkyl chain lengths (ethyl, butyl, and octyl chains) was investigated in ionic liquids (ILs) by steady-state fluorescence and transient absorption spectroscopy. Upon photoexcitation, C n HF underwent ESIPT from the normal form to the tautomer form, and dual emissions from both states were detected. For C 4 HF and C 8 HF, the tautomerization yields determined from the fluorescence intensity ratios increased with the increasing number of alkyl chain carbon atoms in the cation and on reducing the excitation wavelength as reported for C 2 HF [K. Suda et al., J. Phys. Chem. B. 117 , 12567 ( 2013 )]. The transient absorption spectra of C n HF were measured at excitation wavelengths of 360, 400, and 450 nm. The ESIPT rate determined from the induced emission of the tautomer was correlated with the tautomerization yield for C 2 HF and C 4 HF. In addition, the recovery of the ground-state bleach was found to be strongly dependent on the excitation wavelength. This result indicates that the solvated state of the molecule before photoexcitation is dependent on the excitation wavelengths. The time constant for the ground-state relaxation was slower than that for the excited state.

Several possible reaction pathways for nucleotidyl transfer reaction in DNA polymerase [beta] were determined by using different quantum mechanical methods.

The contrasting effects of flexible polymethylene and rigid aryl spacer groups on the photophysical and electrochemical properties of the novel viologen-linked acridine dyads bounded to [beta]-cyclodextrin are examined. Results suggest an enhanced rates of electron transfer in systems with rigid aryl spacers due to the unusual planarization of the dyad upon encapsulation in the [beta]-cyclodextrin cavity.

The quantum mechanical/ molecular mechanical (QM/MM) calculations are used to study the mechanism of the proton transfer and the molecular rearrangements after the photoisomerization of the chromophore in the photocycle of the photoactive yellow protein. The analysis shows that the water molecular migration plays an important role in the reaction, as it propagates the proton transfer by the hydrogen bond rearrangement.

Studies done on the stability and catalytic activity of the PVP-Pt nanoparticle during its catalytic function for the electron-transfer reaction between hexacyanoferrate(III) ions and thiosulfate ions is presented. Studies reveal that the hexacyanoferrate(III) ions alone dissolve the Pt from the nanoparticle surface to form a cyano complex, as expected from thermodynamic considerations whereas thiosulfate seems to bind to the nanoparticle surface.

The ultrasonic absorption coefficients in the frequency range from 0.8 to 220 MHz were measured in aqueous solution of propylamine in the presence of poly(vinylpyrrolidone) (PVP) with several polymerization degrees at 25 degreeC. A single Debye-type relaxational absorption was observed when propylamine coexists in solution, and the cause of it was attributed to a perturbation of chemical equlibrium associated with a proton-transfer reaction.

Electrolyte properties of a novel lithium salt of a weakly coordinating anion, lithium tetra aluminate, are studied. It is used to design polymer electrolytes with high ionic conductivity.

A new electrochemical system for characterizing electron transfer (ET) processes is discussed. The low possibility of the ET mechanism is deduced from theoretical estimation of the standard rate constant and transfer coefficient for the hypothetical heterogeneous ET.

Research is presented describing the different linear compressibility for three electron transfer systems. The factors regulating electronic transfer reactions in proteins are considered.

The naturally occurring quinones hypericin and hypocrellin are known to induce antiviral and antitumor activity. For this reason, their proton-transfer reactions have been examined previously using various spectroscopic methods, leading to the conclusion that intramolecular excited-state proton transfer is a dominant nonradiative process in both of these polycyclic quinones. Their proton-transfer reactions are further elaborated using 1:1 mixtures of ethanol and methanol to demonstrate the temperature dependence of these excited-state reactions.