theory, namely branching ratio, time scales, or luminescence quantum yields, needs
simulation of the dynamics in real time. Obviously, whereas a complete quantum
treatment is possible for small molecules involving 5 or 6 atoms [33, 34] other
strategies have to be employed for large transition metal complexes with ~50–100
atoms and a metal center.
The purpose of this chapter is to review density functional theory (DFT)-based
methods for computing with reasonable accuracy excited states properties, including spin-orbit coupling (SOC) in transition metal complexes, and to point to
pioneering strategies to simulate ultra-fast ISC processes in this class of molecules.
Whenever possible, the time-dependent DFT (TD-DFT) excited states properties
are compared either to the results obtained by more accurate ab initio methods or to
experimental data. The first section is devoted to methodological highlights oriented to the computation of SOC and its interplay with vibronic coupling, and to the
simulation of ISC. The two next sections are dedicated to SOC effects on the
absorption and emission spectroscopies exemplified by recent theoretical studies
performed on third-row Ir(III), Re(I), and Pt(II) complexes. The last section reports
on recent pioneering simulations of ultra-fast ISC processes in various complexes
from first to third row on the basis of different approaches.
2 Methodological Highlights
Transition metal complexes cumulate most of the complexities inherent to theoretical studies: size, electronic delocalization, near-degeneracy, high density of electronic states of various characters, multi-configurational electronic structures, longrange charge transfer states, relativistic effects, especially spin-orbit coupling,
dissociative states, states mixing, and vibronic couplings.
Recent reviews and articles give the reader an idea of the latest developments
and applications related to excited states in large molecules and/or transition metal
complexes [18, 19, 35–43].
In spite of well-known drawbacks, the long-range charge transfer problem being
particularly pertinent in the case of transition metal complexes [35] (and references
therein), the TD-DFT approach remains a computationally simple and efficient
method. This approach, thanks to recent developments [44], can treat practical
problems in a reasonable time scale at low cost as compared to highly correlated ab
initio methods [45–54]. This section focuses on three issues, especially relevant for
transition metal complexes excited states: (1) the spin-orbit coupling (SOC) problem; (2) the vibronic coupling problem; (3) the simulation of ISC processes.
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C. Daniel
simulation of the dynamics in real time. Obviously, whereas a complete quantum
treatment is possible for small molecules involving 5 or 6 atoms [33, 34] other
strategies have to be employed for large transition metal complexes with ~50–100
atoms and a metal center.
The purpose of this chapter is to review density functional theory (DFT)-based
methods for computing with reasonable accuracy excited states properties, including spin-orbit coupling (SOC) in transition metal complexes, and to point to
pioneering strategies to simulate ultra-fast ISC processes in this class of molecules.
Whenever possible, the time-dependent DFT (TD-DFT) excited states properties
are compared either to the results obtained by more accurate ab initio methods or to
experimental data. The first section is devoted to methodological highlights oriented to the computation of SOC and its interplay with vibronic coupling, and to the
simulation of ISC. The two next sections are dedicated to SOC effects on the
absorption and emission spectroscopies exemplified by recent theoretical studies
performed on third-row Ir(III), Re(I), and Pt(II) complexes. The last section reports
on recent pioneering simulations of ultra-fast ISC processes in various complexes
from first to third row on the basis of different approaches.
2 Methodological Highlights
Transition metal complexes cumulate most of the complexities inherent to theoretical studies: size, electronic delocalization, near-degeneracy, high density of electronic states of various characters, multi-configurational electronic structures, longrange charge transfer states, relativistic effects, especially spin-orbit coupling,
dissociative states, states mixing, and vibronic couplings.
Recent reviews and articles give the reader an idea of the latest developments
and applications related to excited states in large molecules and/or transition metal
complexes [18, 19, 35–43].
In spite of well-known drawbacks, the long-range charge transfer problem being
particularly pertinent in the case of transition metal complexes [35] (and references
therein), the TD-DFT approach remains a computationally simple and efficient
method. This approach, thanks to recent developments [44], can treat practical
problems in a reasonable time scale at low cost as compared to highly correlated ab
initio methods [45–54]. This section focuses on three issues, especially relevant for
transition metal complexes excited states: (1) the spin-orbit coupling (SOC) problem; (2) the vibronic coupling problem; (3) the simulation of ISC processes.
380
C. Daniel