3 research outputs found
Analyzing Fluxional Molecules Using DORI
The
Density Overlap Region Indicator (DORI) is a density-based
scalar field that reveals covalent bonding patterns and noncovalent
interactions in the same value range. This work goes beyond the traditional
static quantum chemistry use of scalar fields and illustrates the
suitability of DORI for analyzing geometrical and electronic signatures
in highly fluxional molecular systems. Examples include a dithiocyclophane,
which possesses multiple local minima with differing extents of π-stacking
interactions and a temperature dependent rotation of a molecular rotor,
where the descriptor is employed to capture fingerprints of CH-π
and π–π interactions. Finally, DORI serves to examine
the fluctuating π-conjugation pathway of a photochromic torsional
switch (PTS). Attention is also placed on postprocessing the large
amount of generated data and juxtaposing DORI with a data-driven low-dimensional
representation of the structural landscape
Effects of the Environment on Charge Transport in Molecular Wires
Supramolecular engineering offers opportunities for creating
polymer-based
materials with tailored conductive properties. However, this requires
an understanding of intermolecular interaction effects on intramolecular
charge transport. We present a study of hole transport along molecular
wires consisting of fluorene–<i>p</i>-biphenyl or
Zn–porphyrin monomer units, in dilute solutions. The intramolecular
hole mobility was studied by pulse radiolysis–time-resolved
microwave conductivity. Experiments were supplemented by charge transport
simulations employing a quantum-mechanical description of the hole
and a classical description of the polymer and solvent dynamics. The
model was parametrized using <i>ab initio</i> and molecular
dynamics calculations. It was found that the solvent-induced energy
disorder along a polymer chain in common solvents (benzene, cyclohexane,
acetonitrile, water) is ∼1 eV, significantly greater than the
values of 0.05–0.2 eV commonly cited in the literature. Environment-induced
disorder of this magnitude has profound consequences for intramolecular
charge transport. The hole initial state upon injection onto a molecular
wire also influences the mobility. Experiments and simulations demonstrate
that supramolecular modification of polymers (coordination, rotaxination)
can significantly enhance or suppress charge transport. Incorporating
a molecular level description of the immediate supramolecular and
solvent environment into charge transport models improves their predictive
potential, providing a valuable tool for material design