Inorganic Photochemistry and Solar Energy Harvesting: Current Developments and Challenges to Solar Fuel Production

Abstract

The large and continuous use of fossil fuels as a primary energy source has led to several environmental problems, such as the increase of the greenhouse effect. In order to minimize these problems, attention has been drawn to renewable energy production. Solar energy is an attractive candidate as renewable source due to its abundance and availability. For this, it is necessary to develop devices able to absorb sunlight and convert it into fuels or electricity in a economical, technical and sustainable way. The so-called artificial photosynthesis has called the attention of researchers due to the possibility of using solar photocatalysts in converting water and CO2 into fuels. This manuscript presents a review of the recent developments of hybrid systems based on molecular photocatalysts immobilized on semiconductor surfaces for solar fuel production through water oxidation and CO2 reduction and also discusses the current challenges for the potential application of these photocatalyst systems.

Nonadiabatic Coupling in Trajectory Surface Hopping: How Approximations Impact Excited-State Reaction Dynamics

“…Photochemically active compounds, molecules that react due to exposure to light, are ubiquitous in both nature and human activities forming the basis of photosynthesis and having applications in fields ranging from medicine to materials. − Interest in these types of molecules, while always present, has exploded in recent years with the development of sustainable energy sources. − The synthesis of chemicals in a “green manner” using solar energy via photochemical reactions is also a very active research domain. − Probing photoreactivity with experimental methods, however, remains difficult due to the short-lived character of excited states. In this context, first-principles calculations are often used to understand photochemical transformations.…”

Rhenium(I) Complexes with Neutral Monodentate Coligands and Monoanionic 2-(1,2,4-Triazol-5-yl)pyridine-Based Chelators as Bidentate Luminophores with Tunable Color and Photosensitized Generation of 1O2: An Integrated Case Study Involving Photophysics and Theory

“…Rhenium­(I) complexes with polypyridyl ligands comprise a group of coordination compounds with interesting physicochemical features that can be exploited for the realization of photofunctional materials with appealing properties, such as thermal and photochemical stability, rich excited-state behavior, , large Stokes shifts as well as long excited-state lifetimes, , among many others. In particular, due to their photoluminescence and intrinsic stabilities, rhenium­(I) tricarbonyl complexes with a monodentate coligand (L 1 ) and an α-diimine as the bidentate chromophore (L 2 ) (i.e., fac -[Re­(CO) 3 (L 1 )­(L 2 )] complexes) have been explored for a vast range of applications in broad research areas including solar energy conversion, − catalysis, − and metal-based medicine. − In addition, the use of these molecular species as noncovalent luminescent probes, , in biomedical imaging, − and in anticancer treatments , has been explored due to their versatility resulting from the judicious choice of adequate ligands, allowing the fine-tuning of their physical and chemical properties while optimizing specific processes. ,− ,, In addition, rhenium­(I) tricarbonyl complexes bearing polypyridine ligands constitute excellent photosensitizers for the generation of singlet molecular dioxygen ( 1 O 2 ); therefore, their use in photodynamic therapy can be envisaged in the context of photomedicine, including oncology and antibiotic therapy. , In such rhenium­(I) complexes, the involved photoexcited states are mainly described as metal-to-ligand charge-transfer (MLCT), ligand-to-ligand charge-transfer (LLCT), and/or ligand-centered (LC) excited electronic configurations (or admixtures thereof). While in most cases the photoluminescence evolves from 3 MLCT states, 3 LC or 1 LC configurations have also been invoked to describe the photoactivity, depending on the nature of the ligands employed. , In the past few years, a new family of substituted rhenium­(I) complexes bearing neutral mono-, di-, or triazole-based ligands was proposed. − In those systems, while the features regarding the coordination-chemical structure remain almost constant, the replacement of a pyridyl ring by a smaller π system, such as the triazole moiety, can change the nature of the LC orbitals, leading to new photophysical properties.…”

Neutral and Cationic Re(I) Complexes with Pnictogen-Based Coligands and Tunable Functionality: From Phosphorescence to Photoinduced CO Release

“…In particular, antimony-based ligands were elegantly implemented in Co(II)and Cu(I)-based coordination compounds described by Rose et al to modulate their magnetic and photoluminescence properties, respectively. 45−47 To the best of our knowledge, there is currently only one study available from our group that examines the influence of pnictogen-based coligands on d 8 configured transition metal-based complexes with squareplanar geometry while correlating the bonding nature and photophysical properties. 48 However, there are no reports on analogous efforts concerning (pseudo)octahedral d 6 -metal ions so far.…”

“…Late-transition metal complexes play a major role in modern science. − Especially 4d and 5d cations lead to interesting luminescence properties due to the strong spin–orbit coupling, which can be tuned by means of different metal centers as well as ligand arrays. In particular, rhenium­(I) complexes, which involve a d 6 -configured metal center, exhibit interesting physicochemical properties, including photochemical stability, tunable excited-state characteristics, large Stokes shifts, and long excited-state lifetimes. , Therefore, Re­(I)-based coordination compounds have emerged as promising candidates for various fields in the past few decades, including solar energy conversion, − catalysis, − photosensitization of singlet oxygen, and as luminophores for light-emitting devices . Furthermore, these compounds find potential aplications as noncovalent luminescent probes, , in biomedical imaging − and for metal-based medicine, , owing to their versatile properties.…”