3 research outputs found
A combined theoretical and experimental study of the ultrafast photophysics of Rhodamine B
<p>The ultrafast dynamics of zwitterionic and cationic Rhodamine B in ethanol have been investigated using TDDFT calculations and ultrafast transient absorption spectroscopy. The calculations show that the zwitterionic form exhibits an electronically excited dark state which could potentially quench the initially photoexcited state, while in the case of cationic form the lowest excited lying dark state is outside the energy region of interest and cannot explain its quenching. Due to similarities in the relaxation dynamics of the two molecules, it is suggested that the electronically excited dark state may not play such an important role in the quenching process of this dye as previously proposed. Experimental evidence presented suggests that a quenching mechanism is active on the picosecond timescale for both forms of Rhodamine B.</p
Chlorine Para-Substitution of 1鈥慞henylethanol: Resonant Photoionization Spectroscopy and Quantum Chemical Calculations of Hydrated and Diastereomeric Complexes
The
conformational landscape of (<i>S</i>)-1-(4-chlorophenyl)颅ethanol,
its monohydrated complex, and its diastereomeric adducts with <i>R</i>- and <i>S</i>-butan-2-ol, have been investigated
by resonant two-photon ionization (R2PI) spectroscopy coupled with
time-of-flight mass spectrometry. Theoretical calculations at the
D-B3LYP/6-31++G** level of theory have been performed to assist in
the interpretation of the spectra and in the assignment of the structures.
The R2PI spectra and the predicted structures have been compared with
those obtained on the analogous non-halogenated and fluorinated systems,
i.e., (<i>R</i>)-1-phenylethanol and (<i>S</i>)-1-(4-fluorophenyl)颅ethanol, respectively. It appears that the presence
of chlorine atom in the para position of the aromatic ring does not
influence the overall geometry of bare molecule and its complexes
with respect to the non-halogenated analogous systems. Anyway, it
affects the electron density in the 蟺 system, and in turn the
strength of OH路路路蟺 and CH路路路蟺
interactions. A spectral chiral discrimination is evident from the
R2PI spectra of the diastereomeric adducts of (<i>S</i>)-1-(4-chlorophenyl)颅ethanol
with the two enantiomers of butan-2-ol
Adsorption and Dissociation of <i>R</i>鈥慚ethyl <i>p</i>鈥慣olyl Sulfoxide on Au(111)
Sulfur-based molecules producing self-assembled monolayers
on gold
surfaces have long since become relevant functional molecular materials
with many applications in biosensing, electronics, and nanotechnology.
Among the various sulfur-containing molecules, the possibility to
anchor a chiral sulfoxide to a metal surface has been scarcely investigated,
despite this class of molecules being of great importance as ligands
and catalysts. In this work, (R)-(+)-methyl p-tolyl sulfoxide was deposited on Au(111) and investigated
by means of photoelectron spectroscopy and density functional theory
calculations. The interaction with Au(111) leads to a partial dissociation
of the adsorbate due to S鈥揅H3 bond cleavage. The
observed kinetics support the hypotheses that (R)-(+)-methyl p-tolyl sulfoxide adsorbs on Au(111) in two different adsorption
arrangements endowed with different adsorption and reaction activation
energies. The kinetic parameters related to the adsorption/desorption
and reaction of the molecule on the Au(111) surface have been estimated