The excited state intramolecular proton transfer (ESIPT) in 1-(trifluoroacetylamino)naphthaquinone (TFNQ) has been investigated using the CASSCF and CASPT2 computational approaches with the 6-31G(d) basis set. The structures and relative energies of critical points along the proton transfer reaction coordinate were optimized and the associated spectroscopic and electrostatic properties obtained...

Monitoring the chromism induced by intramolecular hydrogen and charge transfers within proteins as well as the isomerization of both protein and cofactor is essential not only to understand photoactive signaling pathways but also to design targeted opto-switchable proteins. We used a dual-ion mobility drift tube coupled to a tunable picosecond laser to explore the optical and structural propert...

A new method for the expansion of potential energy surfaces has been developed exploiting the peculiar properties of Hahn polynomials, a class of orthogonal polynomials of a discrete variable which generalize 3j vector coupling coefficients of angular momentum algebra. The method has been tested for the He nonÈHeiles potential, a typical model for coupled oscillators, and applied to the repres...

We discuss theoretically the geometric and electronic structure properties of the thiazolidinedione derivative A and its hydrogen-bonded complex in dimethylformamide (DMF) solution in the S0 and S1 states. To gain insight into the photoinduced coupled excited-state proton transfer (ESPT) and twisted intramolecular charge transfer (TICT) associated with intermolecular hydrogen bonding, the poten...

The photophysics of N,N'-bis(salicylidene)-p-phenylenediamine (BSP) is analyzed both theoretically and experimentally. The alternative intramolecular proton-transfer reactions lead to three different tautomers. We performed DFT and TDDFT calculations to analyze the topography of the reactions connecting the three tautomers. Deactivation paths through a Conical Intersection (CI) region are also ...

Here we report a ternary catalyst system for the intramolecular hydroamidation of unactivated olefins using simple N-aryl amide derivatives. Amide activation in these reactions occurs via concerted proton-coupled electron transfer (PCET) mediated by an excited state iridium complex and weak phosphate base to furnish a reactive amidyl radical that readily adds to pendant alkenes. A series of H-a...

The excited-state proton transfer and subsequent intramolecular ion pair formation of a cupreidine-derived Cinchona organocatalyst (BnCPD) were studied in THF-water mixtures using picosecond time-resolved fluorescence together with global analysis. Full spectral and kinetic characterization of all the fluorescent species allowed us to monitor the 3-step process for the ion pair dissociation. In...

Up to now, the response of antibiotics upon ionizing radiation has been very scarcely reported. Here, we present results X-ray photoabsorption experiments on isolated rifamycin, a broad-range antibiotic against Gram-positive and Gram-negative bacteria. A mass spectrometer coupled synchrotron beamline analyze cationic products protonated rifamycin dimer monomer sodium salts. Absorption single ph...

In mass spectrometry of protonated N-phenylcinnamides, the carbonyl oxygen is the thermodynamically most favorable protonation site and the added proton is initially localized on it. Upon collisional activation, the proton transfers from the carbonyl oxygen to the dissociative protonation site at the amide nitrogen atom or the α-carbon atom, leading to the formation of important reactive interm...

The computational investigation of photochemical processes often entails the calculation excited-state geometries, energies, and energy gradients. nuclear–electronic orbital (NEO) approach treats specified nuclei, typically protons, quantum mechanically on same level as electrons, thereby including associated nuclear effects non-Born–Oppenheimer behavior into chemistry calculations. multicompon...