2 research outputs found
Fate of Photoexcited Molecular Antennae - Intermolecular Energy Transfer versus Photodegradation Assessed by Quantum Dynamics
The
present computational study aims to unravel the competitive
photoinduced intermolecular energy transfer and electron transfer
phenomena in a light-harvesting antenna with potential applications
in dye-sensitized solar cells and photocatalysis. A series of three
thiazole dyes with hierarchically overlapping emission and absorption
spectra, embedded in a methacrylate-based polymer backbone, is employed
to absorb light over the entire visible region. Intermolecular energy
transfer in such antenna proceeds via energy transfer from dye-to-dye
and eventually to a photosensitizer. Initially, the ground and excited
state properties of the three push–pull-chromophores (e.g.,
with respect to their absorption and emission spectra as well as their
equilibrium structures) are thoroughly evaluated using state-of-the-art
multiconfigurational methods and computationally less demanding DFT
and TDDFT simulations. Subsequently, the potential energy landscape
for the three dyads, formed by the π-stacked dyes as occurring
in the polymer environment, is investigated along linear-interpolated
internal coordinates to elucidate the photoinduced dynamics associated
with intermolecular energy and electron transfer processes. While
energy transfer among the dyes is highly desired in such antenna,
electron transfer, or rather a light-induced redox chemistry, leading
to the degradation of the chromophores, is disadvantageous. We performed
quantum dynamical wavepacket calculations to investigate the excited
state dynamics following initial light-excitation. Our calculations
reveal for the two dyads with adjusted optical properties exclusively
efficient intermolecular energy transfer within 200 fs, while in the
case of the third dyad intermolecular electron transfer dynamics can
be observed. Thus, this computational study reveals that statistical
copolymerization of the individual dyes is disadvantageous with respect
to the energy transfer efficiency as well as regarding the photostability
of such antenna
Hydrogel-Embedded Model Photocatalytic System Investigated by Raman and IR Spectroscopy Assisted by Density Functional Theory Calculations and Two-Dimensional Correlation Analysis
The presented study reports the synthesis
and the vibrational spectroscopic
characterization of different matrix-embedded model photocatalysts.
The goal of the study is to investigate the interaction of a polymer
matrix with photosensitizing dyes and metal complexes for potential
future photocatalytic applications. The synthesis focuses on a new
rhodamine B derivate and a PtÂ(II) terpyridine complex, which both
contain a polymerizable methacrylate moiety and an acid labile acylhydrazone
group. The methacrylate moieties are afterward utilized to synthesize
functional model hydrogels mainly consisting of polyÂ(ethylene glycol)
methacrylate units. The pH-dependent and temperature-dependent behavior
of the hydrogels is investigated by means of Raman and IR spectroscopy
assisted by density functional theory calculations and two-dimensional
correlation spectroscopy. The spectroscopic results reveal that the
PtÂ(II) terpyridine complex can be released from the polymer matrix
by cleaving the Cî—»N bond in an acid environment. The same behavior
could not be observed in the case of the rhodamine B dye although
it features a comparable Cî—»N bond. The temperature-dependent
study shows that the water evaporation has a significant influence
neither on the molecular structure of the hydrogel nor on the model
photocatalytic moieties