Search

The infrared spectra of the hydrogen bonded solute-solvent complexes in electronically excited states are calculated to study the early time hydrogen-bonding dynamics of chromophore in hydrogen-donating solvents upon photoexcitation by using the time-dependent density functional theory method. It demonstrated that the intermolecular hydrogen bonds between coumarin 102 (C102) and hydrogen donating solvents are strengthened in the early time photoexcitation to the electronically excited state by theoretically monitoring the stretching models of C=O and H-O groups.

The ultrafast hydrogen bond strengthening of the photoexcited fluorenone (FN) in various hydrogen donating alcohol solvents is studied. The results demonstrate that hydrogen bonding can easily quench the total fluorescence of fluorenone in polar protic solvents.

An investigation of a series of platinum-containing organometallic complexes for the study of fluorescence phenomena in organometallic chromophores controlled by the intramolecular charge transfer (ICT) is presented in this work. We report steady-state and time-resolved spectroscopic experiments as well as quantum chemistry calculations to investigate the substituent effects on the ICT and fluorescence emission. We demonstrate that the fluorescence maximum and lifetimes greatly depend on different substituents and the presence of bimetallic platinum donor. This work paves the way for an understanding of the fluorescence phenomena controlled by molecular ICT characters of these kinds of platinum-containing organometallic complexes. [ABSTRACT FROM AUTHOR]

To study the early time hydrogen-bonding dynamics of chromophore in hydrogen-donating solvents upon photoexcitation, the infrared spectra of the hydrogen-bonded solute−solvent complexes in electronically excited states have been calculated using the time-dependent density functional theory (TDDFT) method. The hydrogen-bonding dynamics in electronically excited states can be widely monitored by the spectral shifts of some characteristic vibrational modes involved in the formation of hydrogen bonds. In this study, we have demonstrated that the intermolecular hydrogen bonds between coumarin 102 (C102) and hydrogen-donating solvents are strengthened in the early time of photoexcitation to the electronically excited state by theoretically monitoring the stretching modes of CO and H−O groups. This is significantly contrasted with the ultrafast hydrogen bond cleavage taking place within a 200-fs time scale upon electronic excitation, proposed in many femtosecond time-resolved vibrational spectroscopy experiments. The transient hydrogen bond strengthening behaviors in excited states of chromophores in hydrogen-donating solvents, which we have demonstrated here for the first time, may take place widely in many other systems in solution and are very important to explain the fluorescence-quenching phenomena associated with some radiationless deactivation processes, for example, the ultrafast solute−solvent intermolecular electron transfer and the internal conversion process from the fluorescent state to the ground state. [ABSTRACT FROM AUTHOR]