Challenging systems for quantum chemistry : inorganic excited states and intermolecular aggregates
Abstract
This thesis focuses on challenging systems for computational chemistry:
inorganic excited states and intermolecular aggregates. Excited states of
inorganic systems can be extremely challenging for conventional methods
of quantum chemistry, mostly due to strong correlation, degeneracy
and near-degeneracy problems, in addition to a large density of states.
A calibration study of the electronic excited states of a range of complexes
has been carried out in a number of chapters using a wide range of
methods. A range of all-electron and ECP basis sets were used. These
calculations reveal the effect of improving the treatment of electron correlation
systematically. A CASSCF/RASSCF study was performed for
the most complex systems to be able to capture and analyse the multireference
nature of the complexes. Later in the thesis the photochemistry
arising from the photodissociaton of Mn2(CO)10 and Cr(CO)6 is
described using CASPT2 to recover the dynamic correlation of the system
and compare with previous CASSCF results. The last part focuses
on intermolecular aggregates. Supramolecular structures have grown in
importance in recent years due to their potential applications as advanced
functional materials. The fine-tuning of these structures allows
to build up higher hierarchical superstructures with very diverse and
interesting properties. A bottom-up approach for this kind of systems
is used to characterize the multichromophoric self-assembly of gels and
detail their responses to light.