Abbreviations
CASPT2 Complete active space second-order perturbation theory
CASSCF Complete active space self-consistent field
DFT
Density functional theory
LMCT
Ligand-to-metal charge transfer
MECP
Minimum energy crossing point
MLCT
Metal-to-ligand charge transfer
MM
Molecular mechanics
OIRE
Oxidatively induced reductive elimination
ONIOM
Own N-layered integrated molecular orbital and molecular mechanics
OSS
Open-shell singlet
PET
Photoinduced electron transfer
QM
Quantum mechanics
SET
Single electron transfer
SMD
Solvation model based on density
TD-DFT Time-dependent density functional theory
UFF
Universal force field
1 Introduction
The increasing chemical use of light is one of the most exciting developments of
modern chemistry. Sunlight is an inexhaustible source of energy, [1] and
photoactivated reactions allow the generation of kinetically and thermodynamically
disfavored products which are not accessible through thermal activation [2]. Moreover, photochemistry can be considered as a green and sustainable methodology in
the sense that using the activation force of sunlight avoids the necessity of hightemperature or high-pressure conditions. Photoactivation can also facilitate process
tuning, as the photoactivity of the absorbent molecule can be turned off by shutting
down the light source, either totally or in a specific wavelength.
Despite their potential advantages, light-driven transformations have been an
underdeveloped field for many decades. The excited state of many organic molecules can only be accessed upon irradiation in the ultraviolet (UV) region, and this
high-energy light can cause undesired side processes, such as decomposition. For
instance, the absorbed energy may be in the order of the bond dissociation energy of
some C–C bonds [3]. Another problem is the possible role of deactivation pathways
such as fluorescence, phosphorescence, or nonradiative relaxation, which can restore
the original ground state of the molecule and hence shut down the photoactivated
reaction [4].
The development of transition metal-based photosensitizers has allowed to tackle
some of these problems and lead to the efficient transformation of solar energy into
chemical potential [5, 6]. Photosensitizers have some characteristic features: they
132
A. de Aguirre et al.
CASPT2 Complete active space second-order perturbation theory
CASSCF Complete active space self-consistent field
DFT
Density functional theory
LMCT
Ligand-to-metal charge transfer
MECP
Minimum energy crossing point
MLCT
Metal-to-ligand charge transfer
MM
Molecular mechanics
OIRE
Oxidatively induced reductive elimination
ONIOM
Own N-layered integrated molecular orbital and molecular mechanics
OSS
Open-shell singlet
PET
Photoinduced electron transfer
QM
Quantum mechanics
SET
Single electron transfer
SMD
Solvation model based on density
TD-DFT Time-dependent density functional theory
UFF
Universal force field
1 Introduction
The increasing chemical use of light is one of the most exciting developments of
modern chemistry. Sunlight is an inexhaustible source of energy, [1] and
photoactivated reactions allow the generation of kinetically and thermodynamically
disfavored products which are not accessible through thermal activation [2]. Moreover, photochemistry can be considered as a green and sustainable methodology in
the sense that using the activation force of sunlight avoids the necessity of hightemperature or high-pressure conditions. Photoactivation can also facilitate process
tuning, as the photoactivity of the absorbent molecule can be turned off by shutting
down the light source, either totally or in a specific wavelength.
Despite their potential advantages, light-driven transformations have been an
underdeveloped field for many decades. The excited state of many organic molecules can only be accessed upon irradiation in the ultraviolet (UV) region, and this
high-energy light can cause undesired side processes, such as decomposition. For
instance, the absorbed energy may be in the order of the bond dissociation energy of
some C–C bonds [3]. Another problem is the possible role of deactivation pathways
such as fluorescence, phosphorescence, or nonradiative relaxation, which can restore
the original ground state of the molecule and hence shut down the photoactivated
reaction [4].
The development of transition metal-based photosensitizers has allowed to tackle
some of these problems and lead to the efficient transformation of solar energy into
chemical potential [5, 6]. Photosensitizers have some characteristic features: they
132
A. de Aguirre et al.