Substituent effects on ultrafast excited-state proton transfer of protonated aniline derivatives in aqueous solution

UV-Visible Absorption Spectra of Solvated Molecules by Quantum Chemical Machine Learning

“…Machine Learning Absorption Spectra Figure 4 compares the lowest-energy UV-visible absorption band computed by the multiscale quantum-chemical approach described in the methods section to experimental measurements for each molecule in aqueous solution. 6,[70][71][72][73][74][75] The QC model is in excellent agreement with the experiments for 8 out of 10 molecules, with differences in the center of the peak within less than 0.1 eV and nearly overlapping low-energy tails. Experimental bands tend to be broader on the high energy side, possibly because they encompass the tails of higher excited states.…”

“…The absorption spectrum of 1,4-anisidine was measured at pH= 6.0, while in our FPMD simulations molecules solvated in aqueous solution at neutral pH, and this difference may cause a shift in the UV-visible absorption. 70,77 The QC spectra were obtained by averaging only a few hundred frames for each molecule.…”

Role of a Conserved Prolyl Residue (Pro173) of MotA in the Mechanochemical Reaction Cycle of the Proton-Driven Flagellar Motor of Salmonella

“…Although the kinetic parameters for the rates of proton transfer may seem extremely high, the highest one, which is 6.0 × 10 15 M − 1 s − 1 for k 3 (the rate of cytoplasmic proton association), can be converted to 6.0 × 10 9 s − 1 even at an intracellular pH of 6.0, and this value is much slower than those previously estimated by Lill and Helms 35 for the rate of proton transfer between amino acids of green fluorescent protein and between a hydronium ion and an amino acid, which are 10 13 -10 14 s − 1 , and those measured by Shiobara et al 36 for proton dissociation from aniline in aqueous solution, which are around 10 10 s − 1 . a From Minamino et al 22 b The number of protons per revolution of the motor is determined based on the balance between input energy (number of protons × proton charge × PMF) and output work (2π × torque × rotation rate) at − 110 mV where the average of the six zero-speed torque values was used.…”

Solvent Assisted Photoacidity

“…This situation dramatically changes upon moving to less polar solvents where neutral photoacids become much weaker acids. 12.3) [19,25,101,115,116]. Some relevant data on the pK * a 's is collected in Tables 12.1 and 12.2 where the Förster cycle photoacidity of 1-naphthol and 2-naphthol is listed in several solvents where the ground-state acidity of the photoacid is known.…”

“…An example is the proton dissociation reaction of protonated aminopyrenes RN * H 3 + (Fig. 12.3) [19,25,101,115,116]. The K * a values of this family of cationic photoacids are very large with some pK * a values approaching the acidity of strong mineral acids (Fig.…”