Photocatalytic Transformations Research Articles

Novel Triangulenes: Computational Investigations of Energy Thresholds for Photocatalytic Water Splitting.

Organic materials with Inverted Singlet-Triplet (INVEST) gaps are interesting for their potential use in photocatalytic small molecule transformations such as the entirely solar-driven water splitting reaction. However, only a few INVEST emitters are thermodynamically able to split water requiring a first singlet excited dark state, S1 , above 1.27 or 1.76 eV, and absorption near solar the maximum, 2.57 eV. These requirements and the INVEST character are key for achieving a long-lived photocatalyst for water splitting. The only known INVEST emitters that conform to these criteria are large triangular boron carbon nitrides with unknown synthesis pathways. Using ADC(2), a quantum-mechanical method, we describe three triangulenes. 3 a is a cyano azacyclopenta[cd]phenalene derivative while 3 b and 3 c are cycl[3.3.3]azine derivatives. 3 b has a previously undescribed disulfide bridge. Overall, 3 a fulfills requirements for photocatalytic four-electron reduction of water while the S1 states of 3 b and 3 c are likely slightly low for the two-electron reduction process. By analyzing impacts of ligands, we find that there are guidelines describing how S1 -S5 energies and oscillator strengths, T1 energies, and ΔES1T1 gaps are affected, requiring deep-learning algorithms for which studies will be presented by us in due time. The impact of ground-state geometries, solvation effects, as well as reduced-cost ADC(2) algorithms on our findings are also discussed.

Supramolecular organic framework for recyclable heterogeneous photocatalysis of the reductive dechlorination of α-Chloroacetophenones and acetylation of amines with thioacetate

Due to the urgent demand for environmentally friendly synthetic methods, metal-free materials have gained increasing prominence in various photocatalytic organic transformations. The utilization of supramolecular organic frameworks (SOFs) as photocatalysts has gradually emerged in photo-induced organic reactions, which complements the widespread use of porous organic polymers and covalent organic frameworks. SOFs, which are constructed through noncovalent interactions, can function as heterogeneous catalysts due to their low solubility in typical organic solvents. The present study reports the application of a SOF for heterogeneous photocatalysis. A tetraphenylmethane-based monomer (TM) incorporating four 4,4′-(thiazolo[5,4-d]thiazole-2,5-diyl)bis(1-methyl-1-pyridinium) units (MPT) has been synthesized and co-assemble with cucurbit[8]uril (CB[8]) to afford a photoactive three-dimensional supramolecular organic framework (TM-SOF) through the encapsulation of two MPT units by CB[8]. Various methods have been employed to characterize the optical and electronic properties of TM-SOF and reveal its exceptional light-absorbing properties that facilitate photoredox catalysis by generating reactive radical species. As a heterogeneous photocatalyst, TM-SOF efficiently catalyzes photoinduced reductive dichlorination of α-chloroacetophenones and acetylation of amines with thioacetate with high recyclability. Mechanistic studies were further conducted to reveal the effect of the framework on the photocatalytic efficiency of the MPT unit.

Recent trends in metal-doped carbon nitride-catalyzed heterogeneous light-driven organic transformations

Doping carbon nitride with metal nanoparticles and metal single atoms is an efficient way to enhance the photocatalytic activity of the material for light-driven synthetic transformations. The metal-doped carbon nitride composites have also been recently demonstrated as one of the most powerful and sustainable metallaphotocatalysts in organic synthesis. A series of metals such as Pd, Ni, Cu, Fe, Co, and others have been incorporated into carbon nitride and used in photocatalytic reactions, such as cross-couplings, reductions, oxygenations, etc. These newly developed heterogeneous photocatalytic systems exhibit inherent advantages of easy separation and remarkable recyclability. In this review, we summarize the emergence, recent development, as well as unexplored aspects of the metal-doped carbon nitride in the heterogeneous photocatalytic organic transformations.

Diaryl Dihydrophenazine-Based Porous Organic Polymers Enhance Synergistic Catalysis in Visible-Light-Driven Organic Transformations.

Porous organic polymers (POPs) have emerged as a novel class of porous materials that are synthesized by the polymerization of various organic monomers with different geometries and topologies. The molecular tunability of organic building blocks allows the incorporation of functional units for photocatalytic organic transformations. Here, we report the synthesis of two POP-based photocatalysts via homopolymerization of vinyl-functionalized diaryl dihydrophenazine (DADHP) monomer (POP1) and copolymerization of vinyl-functionalized DADHP and 2,2'-bipyridine monomers (POP2). The fluorescence lifetimes of DADHP units in the POPs significantly increased, resulting in enhanced photocatalytic performances over homogeneous controls. POP1 is highly effective in catalysing visible-light-driven C-N bond forming cross-coupling reactions. Upon coordination with Ni2+ ions, POP2-Ni shows strong synergy between photocatalytic and Ni catalytic cycles due to the confinement effect within the POP framework, leading to high efficiency in energy, electron, and organic radical transfer. POP2-Ni displays excellent activity in catalysing C-P bond forming reactions between diarylphosphine oxides and aryl iodides. They increased the photocatalytic activities by more than 30-fold in C-N and C-P cross-coupling reactions. These POP catalysts were readily recovered via centrifugal separation and reused in six catalytic cycles without loss of activities. Thus, photosensitizer-based POPs provide a promising platform for heterogeneous photocatalytic organic transformations.

Diaryl Dihydrophenazine‐Based Porous Organic Polymers Enhance Synergistic Catalysis in Visible‐Light‐Driven Organic Transformations

AbstractPorous organic polymers (POPs) have emerged as a novel class of porous materials that are synthesized by the polymerization of various organic monomers with different geometries and topologies. The molecular tunability of organic building blocks allows the incorporation of functional units for photocatalytic organic transformations. Here, we report the synthesis of two POP‐based photocatalysts via homopolymerization of vinyl‐functionalized diaryl dihydrophenazine (DADHP) monomer (POP1) and copolymerization of vinyl‐functionalized DADHP and 2,2′‐bipyridine monomers (POP2). The fluorescence lifetimes of DADHP units in the POPs significantly increased, resulting in enhanced photocatalytic performances over homogeneous controls. POP1 is highly effective in catalysing visible‐light‐driven C−N bond forming cross‐coupling reactions. Upon coordination with Ni2+ ions, POP2‐Ni shows strong synergy between photocatalytic and Ni catalytic cycles due to the confinement effect within the POP framework, leading to high efficiency in energy, electron, and organic radical transfer. POP2‐Ni displays excellent activity in catalysing C−P bond forming reactions between diarylphosphine oxides and aryl iodides. They increased the photocatalytic activities by more than 30‐fold in C−N and C−P cross‐coupling reactions. These POP catalysts were readily recovered via centrifugal separation and reused in six catalytic cycles without loss of activities. Thus, photosensitizer‐based POPs provide a promising platform for heterogeneous photocatalytic organic transformations.

Recent Advances in Visible Light‐induced Asymmetric Transformations of Carbonyl Compounds into Chiral Alcohols

AbstractVisible light‐induced photocatalysis has been widely investigated, which offers exciting opportunities to build new catalytic platforms that are unattainable under ground state conditions. Asymmetric photocatalysis has been a longstanding challenge due to the high reactivity of photogenerated intermediates leading to strong background reaction. Carbonyl group is an important fundamental scaffold in organic synthesis. The photocatalytic asymmetric transformations of carbonyl compounds for synthesizing enantioenriched secondary and tertiary alcohols are of significant value but remain problematic. Even so, a series of intriguing works concerning this topic have been reported in recent year. This review summarizes the advances in this area, mainly dividing into single and synergetic catalyst systems, and the mechanism of each reaction is discussed.

An olefin-linked pyridinium covalent organic frameworks bearing donor–acceptor structure for highly efficient photocatalytic organic transformations

As we know, the photoelectric properties of the covalent organic frameworks (COFs) can be properly adjusted by introducing an electron donor–acceptor (D–A) structure. In here, a two-dimensional D–A type Py-BPDAIP-COF with an excellent photoelectric characteristic was prepared in a post-modified method. Significantly, the introducing of very strong electron-withdrawing pyridinium structure dramatically improve inductive and conjugative effects of the electron acceptor unit of Py-BPDAIP-COF. And the electron-rich pyrene skeleton on the knot of the COF was as an electron donor. Then a strong electron push–pull effect between the donor and acceptor units can be transmitted to the COFs backbone, significantly improving the transfer and separation of light-generated electrons. The Py-BPDAIP-COF showed very excellent photocatalytic activity in visible light-induce aerobic hydroxylation, thiocyanation transformation and oxidative C-H functionalization. Therefore, we design and construct a highly efficient olefin-linked D–A type COF photocatalysts via tuning inductive and conjugative effects of pore wall surface.

Plasmon-Determined Selectivity in Photocatalytic Transformations on Gold and Gold-Palladium Nanostructures.

Noble metal nanostructures absorb light producing coherent oscillations of the metal's electrons, so-called localized surface plasmon resonances (LSPRs). LSPRs can decay generating hot carriers, highly energetic species that trigger chemical transformations in the molecules located on the metal surfaces. The number of chemical reactions can be expanded by coupling noble and catalytically active metals. However, it remains unclear whether such mono- and bimetallic nanostructures possess any sensitivity toward one or another chemical reaction if both of them can take place in one molecular analyte. In this study, we utilize tip-enhanced Raman spectroscopy (TERS), an emerging analytical technique that has single-molecule sensitivity and sub-nanometer spatial resolution, to investigate plasmon-driven reactivity of 2-nitro-5-thiolobenzoic acid (2-N-5TBA) on gold and gold@palladium nanoplates (AuNPs and Au@PdNPs). This molecular analyte possesses both nitro and carboxyl groups, which can be reduced or removed by hot carriers. We found that on AuNPs, 2-N-5TBA dimerized forming 4,4'-dimethylazobenzene (DMAB), the bicarbonyl derivative of DMAB, as well as 4-nitrobenzenethiol (4-NBT). Our accompanying theoretical investigation based on density functional theory (DFT) and time-dependent density functional theory (TDDFT) confirmed these findings. The theoretical analysis shows that 2-N-5TBA first dimerized forming the bicarbonyl derivative of DMAB, which then decarboxylated forming DMAB. Finally, DMAB can be further reduced leading to 4-NBT. This reaction mechanism is supported by TERS-determined yields on these three molecules on AuNPs. We also found that on Au@PdNPs, 2-N-5TBA first formed the bicarbonyl derivative of DMAB, which is then reduced to both bihydroxyl-DMAB and 4-amino-3-mercaptobenzoic acid. The yield of these reaction products on Au@PdNPs strictly follows the free-energy potential of these molecules on the metallic surfaces.

Modern Applications of Porphyrin-Based MOFs in Agriculture

Nanosized metal-porphyrinic frameworks are an interesting class of porous electro- and photoactive materials finding applications in medicine (photodymanic therapy, photothermal therapy, drug delivery and chemotherapy, immunotherapy), [1], sanitary and antimicrobial devices [2], waste water purification [3], photocatalytic organic transformations [4], production of solar fuels [5], and more recently, in agriculture [6]. The fact that porphyrin derivatives are colored, they are prone for the photosensitization of singlet oxygen (1O2(g); a reactive oxygen species of type II) either at the solid state/air interfaces or in solution leading to applications listed above using visible light. In fact, they even do this efficiently. Reactive oxygen species of type I (for examples, H-O radical, HO-OH, superoxide radical, perhydroxyl radical, etc) are also photo-produced when given metals inside the porphyrins and metallic nodes in the frameworks are used, or when the metal-porphyrinic frameworks form a composite with another semiconductor. Moreover, the size of the nanoparticles can be tailored. All of these properties are cleverly exploited in the field of agriculture and include the following applications: controlled delivery of pesticides and agro-chemicals, detection of pesticides and pathogenic metals, elimination of pesticides and toxic metals, and photodynamic antimicrobial activity, and the nanosized metal-porphyrinic frameworks also have an important implication in food safety. This presentation will describe these features along with new experimental results.

Relevance of photocatalytic redox transformations of selected pharmaceuticals in a copper- and iron-rich Mediterranean intermittent river

This work aimed at investigating specific attenuation pathways of pharmaceuticals in copper- and iron-rich Mediterranean intermittent and sunlit rivers by combining lab- and field-scale studies. Poorly photodegradable and biodegradable compounds such as fluconazole, oxazepam and venlafaxine attenuated in two river stretches with short hydraulic residence times (<3 h). This result was assumed to be related to their capacity to interact with photoreactive free Cu2+ and Fe3+ or their associated oxides. Lab-scale photodegradation experiments under simulated solar irradiation revealed the beneficial impact of a mixture Cu2+ and colloidal iron hydroxides at environmental concentrations and at neutral pH on the pharmaceuticals photodegradation kinetic rate constants. These latter were consistent with the in-stream attenuation rate constants of targeted contaminants which ranged from 0.104 to 0.154 h−1. Further identification of phototransformation products by LC-HRMS highlighted reductive transformation pathways including reductive dehalogenation and hydrogenation reactions. Several TPs were found to be stable under irradiation and were detected in field monitoring, accordingly. This was ascribed to the formation of a Cu/Fe composite material under solar irradiation with photocatalytic properties. The role of Cu was to trap the electron in the conduction band of the iron-based photocatalyst, which promoted separation efficiency of electron-hole pairs as well as enhanced photoreduction processes at the expense of oxidation ones. Even though, these mechanisms have been reported in water treatment field for organic micropollutants removal, their significance was demonstrated for the first time in natural settings.

Application of Photo-inactive Ru(edta) Complexes in Photocatalytic Small Molecules Transformation over Semiconductor Surface - A Perspective

Abstract: Photocatalytic transformation of small substrate molecules to useful products through an environmentally benign and economically viable pathway is a challenging area of research of continual importance. This review focuses on our perception of the application of ruthenium(III) complexes comprising ‘edta’ ligand (edta4- = ethylenediaminetetraacetate) as a ‘redox mediator’ or ‘relay’ in photocatalytic electron transfer reaction pertaining to the conversion of small substrate molecules viz. hydrazine to ammonia, bicarbonate to formate, dioxygen to hydrogen peroxide. In this article, the prospect of [RuIII(edta)(H2O)]- and [RuIII(edta)(pz)]- to act as ‘redox mediator’ or ‘molecular catalysts’ in photocatalytic transformations of aforesaid small molecules are assessed systematically.

Benzothiadiazole covalent organic framework photocatalysis with an electron transfer mediator for selective aerobic sulfoxidation

Covalent organic frameworks (COFs) are promising visible light photocatalysts for aerobic oxidation reactions. However, COFs usually suffer from the assault of reactive oxygen species, leading to hindered electron transfer. This scenario could be addressed by integrating a mediator to promote photocatalysis. Starting with 4,4′-(benzo-2,1,3-thiadiazole-4,7-diyl)dianiline (BTD) and 2,4,6-triformylphloroglucinol (Tp), TpBTD-COF is developed as a photocatalyst for aerobic sulfoxidation. Adding an electron transfer mediator 2,2,6,6-tetramethylpiperidine-1‑oxyl (TEMPO), the conversions are radically accelerated, over 2.5 times of that without TEMPO. Moreover, the robustness of TpBTD-COF is preserved by TEMPO. Remarkably, TpBTD-COF could endure multiple cycles of sulfoxidation, even with higher conversions than the fresh one. TpBTD-COF photocatalysis with TEMPO implements diverse aerobic sulfoxidation by an electron transfer pathway. This work highlights that benzothiadiazole COFs are an avenue for tailor-made photocatalytic transformations.

Carbazole–anthraquinone conjugated microporous polymer photocatalysis for aerobic oxidative cyanation of tertiary amines irradiated by green light

Conjugated microporous polymers (CMPs), which can be designed through molecular building units, have been widely exploited as photoactive materials. Herein, carbazole and anthraquinone are utilized to prepare a carbazole–anthraquinone CMP (CzAQ-CMP) for visible light photocatalysis. Theoretical calculations suggest hole and electron are located at carbazole and anthraquinone, respectively. Besides, CzAQ-CMP allows for electron transfer to molecular oxygen via anthraquinone, forming superoxide. The hole of CzAQ-CMP drives aerobic oxidative cyanation of N,N-dimethylaniline in methanol. Intriguingly, in the presence of acetic acid, the nucleophilic substitution of trimethylsilyl cyanide by superoxide releases cyanide ion to partake in the α-cyanation of N,N-dimethylaniline. Irradiated by green light, the oxidative cyanation of diverse tertiary amines favorably affords the corresponding α-aminonitriles over CzAQ-CMP in high yields. This work illuminates the rational design of CMPs for photocatalytic selective organic transformations.

Understanding the effects of building block rings of π electron-rich organic photocatalysts in CO2 transformation to amino acids

Understanding the effective factors in the performance of some Oligo (p-phenylenes) (OPPs) and Polycyclic Aromatic Hydrocarbons (PAHs), as efficient organocatalysts in photocatalytic CO2 transformations are the main goals of this investigation. The studies are based on density functional theory (DFT) calculations on the mechanistic aspects of C–C bond formation through a coupling reaction between CO2•– and amine radical. The reaction is performed through two successive single electron transfer steps. After careful kinetic investigations by Marcus’ theory rules, powerful descriptors are used to describe the behavior of observed barrier energies of electron transfer steps. The studied PAHs and OPPs consist of different numbers of rings. Thus, it can be considered different charge densities, afforded from π electrons, of PAHs and OPPs that cause distinguished efficiency in kinetic aspects of electron transfer steps. Electrostatic Surface Potential (ESP) analyses reveal a good relationship between the charge density of the studied organocatalysts in single electron transfer (SET) steps and the kinetic parameters of the steps. Moreover, the contribution of rings in the framework of PAHs and OPPs would be another effective factor in the barrier energies of SET steps. Aromatic properties of the rings, studied by the Anisotropy of the Current-Induced Density (ACID), Nucleus-Independent Chemical Shift (NICS), the multi-center bond order (MCBO), and AV1245 Indexes, are the other impressive factors in the role of rings in SET steps. The results show that the aromatic properties of the rings are not similar to each other. Higher aromaticity affords remarkable reluctance of the corresponding ring to participate in SET steps.

Porphyrin-Based Covalent Organic Frameworks: Design, Synthesis, Photoelectric Conversion Mechanism, and Applications

Photosynthesis occurs in high plants, and certain organisms show brilliant technology in converting solar light to chemical energy and producing carbohydrates from carbon dioxide (CO2). Mimicking the mechanism of natural photosynthesis is receiving wide-ranging attention for the development of novel materials capable of photo-to-electric, photo-to-chemical, and photocatalytic transformations. Porphyrin, possessing a similar highly conjugated core ring structure to chlorophyll and flexible physical and chemical properties, has become one of the most investigated photosensitizers. Chemical modification and self-assembly of molecules as well as constructing porphyrin-based metal (covalent) organic frameworks are often used to improve its solar light utilization and electron transfer rate. Especially porphyrin-based covalent organic frameworks (COFs) in which porphyrin molecules are connected by covalent bonds combine the structural advantages of organic frameworks with light-capturing properties of porphyrins and exhibit great potential in light-responsive materials. Porphyrin-based COFs are expected to have high solar light utilization, fast charge separation/transfer performance, excellent structural stability, and novel steric selectivity by special molecular design. In this paper, we reviewed the research progress of porphyrin-based COFs in the design, synthesis, properties, and applications. We focused on the intrinsic relationship between the structure and properties, especially the photoelectric conversion properties and charge transfer mechanism of porphyrin-based COFs, and tried to provide more valuable information for the design of advanced photosensitizers. The applications of porphyrin-based COFs in photocatalysis and phototherapy were emphasized based on their special structure design and light-to-electric (or light-to-heat) conversion control.

Examination of Electronically Mismatched Diels-Alder Reaction by Online Mass Spectrometry.

Electronically mismatched Diels-Alder reactions have gained much interests as an alternative pathway for C-C bond formation. To faciliate the development of facile organic transformations, mechanistic investigations are required. Spectroscopic methods (NMR, EPR and UV-Vis) are normally adopted for mechainism examinations, but further improvements on direct obtaining of structural information of short-lived intermediates are encouraged. Herein, an electronically mismatched Diels-Alder reaction between indole and 1,3-cyclohexadiene (1,3-CHD) was studied by an in situ electrospray ionization mass spectrometry (in-situ MS). Based on the direct sampling and detection of the in-situ MS without sample pre-treatment, the structures and dynamics of important intermediates were on-line examined. A syringe-based photocatalytic reactor and in-situ AMS evaluation system was constructed for mechanism studies. The role of oxygen was confirmed via control reaction employed in the N2 -bubbled system. The stepwise cation radical-based pathway and the [2+2] cycloaddition process were determined through a series of experiments, including solvent evaluation, MS/MS experiments and dynamic monitoring. The dependence of the reaction on solvent polarity demonstrated that the reaction occurs via the formation of cation radicals, which were captured, identified and dynamically monitored via in situ ESI MS. Without pre-separation, the intermediate of [2+2] cycloaddition was identifiedand the cycloaddition process is thereby determined to be the combination of [4+2] cycloaddition and [2+2] cycloaddition. In addition, oxygen was proved to act as an electron mediator for both catalyst Ru (bpz)3 (PF6 )2 and radical cations. The mechanism of electronically mismatched Diels-Alder reaction was successfully deduced by in-situ MS associated with a syringe-based photocatalytic reactor. The structures and dynamics of cation radicals, the effect of O2 for the reaction and the detailed process of [2+2] cycloaddition have been well demonstrated. This work could not only promote the understanding and development of facile photocatalytic transformations, but also enlarge the application of AMS in on-line monitoring.

Tuning the exciton binding energy of covalent organic frameworks for efficient photocatalysis

Owing to the large exciton binding energy (>100 meV) of most organic materials, the process of exciton dissociation into free electrons and holes is seriously hindered, which plays a key role in the photocatalytic system. In this study, a series of chalcogen (S, Se)-substituted mesoporous covalent organic frameworks (COFs) have been synthesized for enhanced photocatalytic organic transformations. Photoelectrochemical measurements indicate that the introduction of semi-metallic Se atom and the enlargement of conjugation degree can not only reduce the exciton binding energy accelerating the charge separation, but also reduce the band gap of COFs. As a result, the COF-NUST-36 with the lowest exciton binding energy (39.5 meV) shows the highest photocatalytic performance for selective oxidation of amines (up to 98% Conv. and 97.5% Sel.). This work provides a feasible method for designing COFs with high photocatalytic activity by adjusting exciton binding energy.

PH-Triggered Recovery of Organic Polymer Photocatalytic Particles for the Production of High Value Compounds and Enhanced Recyclability.

Pseudo-homogeneous polymeric photocatalysts are an emerging class of highly efficient and tunable photocatalytic materials, where the photocatalytic centers are easily accessible. The creation of highly efficient photocatalytic materials that can be rapidly separated and recovered is one of the critical challenges in photocatalytic chemistry. Here, we describe pH-responsive photocatalytic nanoparticles that are active and well-dispersed under acidic conditions but aggregate instantly upon elevation of pH, enabling easy recovery. These responsive photocatalytic polymers can be used in various photocatalytic transformations, including CrVI reduction and photoredox alkylation of indole derivative. Notably, the cationic nature of the photocatalyst accelerates reaction rate of an anionic substrate compared to uncharged species. These photocatalytic particles could be readily recycled allowing multiple successive photocatalytic reactions with no clear loss in activity.

Carbazolic Conjugated Microporous Polymers for Photocatalytic Organic Transformations.

Heterogeneous photocatalysis have been deemed as a versatile and colorful platform for exploring efficient transformation systems. Henceforth, the design of photocatalysts underpins a wide range of research interests. By virtue of synthetic versatility, stability, non-toxicity, purely organic properties, tunable semiconductive structures, and remarkable visible-light absorbance, conjugated microporous polymers (CMPs) have emerged as an attractive new class of semiconductor materials that show great potential for tackling important energy and environmental challenges. Over the past decade, immense efforts have been devoted toward the construction of CMPs-based photocatalysts for versatile photocatalytic transformations. This review aims to summarize the latest representative advances in the field of carbazolic CMPs, focusing on various design strategies for the construction of tailor-made skeletons that have direct impact on their charge dynamics and thus photocatalytic performances, especially on their specific photocatalytic efficiency for organic transformations. Scrutinizing the photocatalytic features and elucidating the related design principles, it is fully described how structure modification of polycarbazoles could have an effect on optical properties, and thus on photocatalytic performance. Furthermore, the bottlenecks that need to be addressed, and the future research directions of CMPs are identified in the area of photocatalysis.

Ruthenium Catalysis in Biological Habitats

AbstractRecent years have witnessed a considerable progress in research aimed at merging transition metal catalysis with chemical and cell biology. Therefore, a crescent number of metal‐catalyzed transformations have been shown compatible with biological media and even with living settings. Of the different transition metals used to build these biocompatible catalysts, ruthenium has demonstrated to be particularly powerful, in part because the resulting complexes exhibit a very good balance between reactivity and biological stability. Indeed, ruthenium complexes have demonstrated utility to promote a great variety of reactions in biologically relevant contexts, from deprotection and redox processes to cycloadditions or photocatalytic transformations. Many of these reactions may enable the development of new type of biological tools and pharmacological strategies.