Radical Cation Research Articles

Біометричний аналіз показників прооксидантно-антиоксидантного стану плазми крові щурів за дії гістаміну і кверцетину

The regularities of the effect of histamine in concentrations of 0.01; 0.1; 1; 10 μM were studied and quercetin in concentrations of 0.1; 0.3; 0.5; 1; 3; 5 mM, as well as their combined effect on the prooxidant-antioxidant state of blood plasma of rats, using cluster and factor biometric analyses. It was established that the experimental groups according to the investigated indicators (TBА-positive products, lipid hydroperoxides, carbonyl groups of neutral and basic proteins, superoxide anion radical, superoxide dismutase, catalase, reduced glutathione, ATP) were distributed among 13 clusters (according to cluster analysis). In one group of similarities, the effect of histamine in concentrations of 0.01 µM and 1 µM was revealed. Quercetin at a concentration of 0.5 mM and histamine at a concentration of 0.1 µM have a similar effect on the indicators of the prоoxidant-antioxidant state of the blood plasma. Combined addition to the blood of histamine at a concentration of 10 μM and quercetin at a concentration of 0.1; 0.5; 3 mM lead to the same changes in the indicated studied indicators. Cluster analysis also combined the combined effects of 0.01 μM histamine and 0.1 and 3 mM quercetin. It is important to note that a decrease in the content of carbonyl groups of proteins was found in those classers whose experimental blood groups were added to histamine and quercetin, which indicates a decrease in protein damage due to free radical oxidation processes. Using factor analysis, it was established the presence of three hidden factors that affect the processes of free radical oxidation of blood under the action of histamine and quercetin. A high correlation of factor I with protein carbonyl groups, reduced glutathione, superoxide anion radical was revealed. Factor II is most correlated with ATP, superoxide dismutase, lipid hydroperoxides. There is a close relationship between factor III and TBА-positive products and catalase. Taking into account the closeness of the relationship, factor I was given the name “factor of action on proteins”, factor II – “factor of action on bioenergetics and initiator of lipid peroxidation processes”, factor III – “factor of enhancement of lipid peroxidation processes”. It was established that quercetin activates factor I (influence on proteins, causing their oxidation) and factor III (intensification of lipid peroxidation processes) depending on the concentration of the drug. Quercetin in a concentration of 1 mM has the property of both factors (I and III).

Harnessing the Reactivity of Nitroarene Radical Anions to Create Quinoline N‐Oxides by Electrochemical Reductive Cyclization

AbstractElectrochemical reduction of 2‐allyl‐substituted nitroarenes using a simple, undivided electrochemical cell with non‐precious electrodes to generate nitroarene radical anions was developed. The nitroarene radical anion intermediates participate in 1,5‐hydrogen atom transfer reactions to construct quinoline N‐oxides bearing aryl‐, heteroaryl‐, alkenyl‐, benzyl‐, sulfonyl‐, or carboxyl groups.

The Photodynamic Agent Designed by Involvement of Hydrogen Atom Transfer for Enhancing Photodynamic Therapy.

Although Type-I photodynamic therapy has attracted increasingly growing interest due to its reduced dependence on oxygen, the design of effective Type-I photosensitizers remains a challenge. In this work, we report a design strategy for Type-I photosensitizers by the involvement of hydrogen atom transfer (HAT). As a proof of concept, a HAT-involved Type-I PS, which simultaneously generates superoxide and carbon-centered radicals under light-irradiation, was synthesized. This photosensitizer is comprised of a fluorene-substituted BODIPY unit as an electron acceptor covalently linked with a triphenylamine moiety as an electron donor. Under light-irradiation, photo-induced intramolecular electron transfer occurs to generate the BODIPY anion radical and triphenylamine cation radical. The former transfers electrons to oxygen to generate O2 -⋅, while the latter loses a proton to produce a benzyl carbon-centered radical which is well characterized. The resulting carbon-centered radicals efficiently oxidize NADH by HAT reaction. This photosensitizer demonstrates remarkable photocytotoxicity even under hypoxic conditions, along with outstanding in vivo antitumor efficacy in mouse models bearing HeLa tumors. This work offers a novel strategy for the design of Type-I photosensitizers by involvement of HAT.

The Photodynamic Agent Designed by Involvement of Hydrogen Atom Transfer for Enhancing Photodynamic Therapy

AbstractAlthough Type‐I photodynamic therapy has attracted increasingly growing interest due to its reduced dependence on oxygen, the design of effective Type‐I photosensitizers remains a challenge. In this work, we report a design strategy for Type‐I photosensitizers by the involvement of hydrogen atom transfer (HAT). As a proof of concept, a HAT‐involved Type‐I PS, which simultaneously generates superoxide and carbon‐centered radicals under light‐irradiation, was synthesized. This photosensitizer is comprised of a fluorene‐substituted BODIPY unit as an electron acceptor covalently linked with a triphenylamine moiety as an electron donor. Under light‐irradiation, photo‐induced intramolecular electron transfer occurs to generate the BODIPY anion radical and triphenylamine cation radical. The former transfers electrons to oxygen to generate O2−⋅, while the latter loses a proton to produce a benzyl carbon‐centered radical which is well characterized. The resulting carbon‐centered radicals efficiently oxidize NADH by HAT reaction. This photosensitizer demonstrates remarkable photocytotoxicity even under hypoxic conditions, along with outstanding in vivo antitumor efficacy in mouse models bearing HeLa tumors. This work offers a novel strategy for the design of Type‐I photosensitizers by involvement of HAT.

Comment on "Localized and Delocalized States of a Diamine Cation: Resolution of a Controversy".

Since its appearance in [Cheng, X.; Zhang, Y.; Jónsson, E.; Jónsson, H.; Weber, P. M. Nat. Commun. 2016, 7, 11013] and recent re-investigation in [Gałyńska, M.; Ásgeirsson, V.; Jónsson, H.; Bjornsson, R. J. Phys. Chem. Lett., 2021, 12, 1250-1255], the dimethylpiperazine cation (DMP+) has generated considerable discussion and controversy in the scientific literature over the existence of stable, local energy minima in this molecular system. Specifically, prior assumptions that the Rydberg state and radical cation of DMP are similar have led to significant confusion and debate regarding the accuracy of various quantum chemistry methods and the existence of stable configurations of DMP+ itself. The purpose of this Viewpoint is to highlight recent studies that call into question the main findings in the previously mentioned works as well as present new CCSDT (Coupled-Cluster with Single, Double, and Triple excitations) calculations to finally bring closure to this controversy.

Photocatalysis Meets Copper Catalysis: A New Opportunity for Asymmetric Multicomponent Radical Cross-Coupling Reactions.

ConspectusIn recent years, radical-mediated cross-coupling reactions have emerged as a compelling strategy for achieving a rich diversity in molecular topologies under benign conditions. However, the inherent high reactivity of radicals presents considerable challenges in controlling reaction pathways and selectivity, which often results in a limited range of substrates and a constrained reaction profile. Given the capacity of visible-light photoredox catalysis to generate a wide variety of reactive radicals and radical ions in a controlled manner and the propensity of copper complexes toward radical species, we envisaged that the synergy between chiral copper catalysts and photoactive catalysts would pave the way for developing innovative strategies. This integration is poised to unlock a broad spectrum of enantioselective multicomponent radical cross-coupling reactions.In this Account, we describe our insights and recent efforts in the realm of enantioselective multicomponent radical cross-coupling reactions. These advancements have been achieved through the innovative application of dual photoredox/copper catalysis or bifunctional copper catalysis under visible light irradiation. Our work is systematically divided into two sections based on the activation modes. The first section focuses on photoinduced copper-catalyzed chiral C-C and C-O bond formation through a radical addition/nucleophilic trap sequence. Our discussion of chiral C-C bond formation is particularly concentrated on the asymmetric carbocyanation and carboarylation of vinylarenes, 1,3-enynes, and 1,3-dienes. Our findings underscore that irradiation with visible light can adeptly modulate the pace of radical generation, thus orchestrating consecutive reaction stages and ensuring the attainment of both chemo- and stereoselectivity. In the domain of chiral C-O bond formation, leveraging carboxylic acids as a nucleophilic oxygen source, we introduce a suite of esterification reactions of benzylic, allylic, and propargylic radicals. These radicals are derived from a variety of radical precursors, showcasing the versatility of our approach. The following section highlights our innovative discovery in the field of dual photoredox/copper catalysis, which enables enantioselective three-component radical transformations via the direct activation of aromatic alkenes. This methodology begins with the generation of formal distonic radical anions through the photocatalytic single-electron reduction of aromatic alkenes, thus, enabling orthogonal reactivity. Employing H2O, D2O, and CO2 as external electrophile agents, we have developed three types of radical cyanofunctionalization reactions: hydrocyanation, deuteriocyanation, and cyanocarboxylation. These reactions provide practical access to diversely functionalized chiral nitriles with high enantiomeric excess.Collectively, these synthetic methodologies highlight the immense potential inherent in the synergistic integration of photocatalysis and asymmetric copper catalysis. This Account aspires to deepen our comprehension of the advantages conferred by these catalytic systems, elucidating the crucial role of photocatalysis in facilitating enantioselective multicomponent radical cross-couplings. We anticipate that this Account will provide valuable insights and stimulate the evolution of innovative methodologies within this rapidly expanding field.

Investigation of the mechanism of [M-H]+ ion formation in photoionized N-alkyl-substituted thieno[3,4-c]-pyrrole-4,6-dione derivatives during higher order MSn high-resolution mass spectrometry.

The mechanism underlying dopant-assisted atmospheric pressure photoionization's (APPI) formation of ions is unclear and still under debate for many chemical classes. In this study, we reexamined the gas-phase reaction mechanisms responsible for the generation of [M-H]+ precursor ions, resulting from the loss of a single hydrogen atom, in a series of N-alkyl-substituted thieno[3,4-c]-pyrrole-4,6-dione (TPD) derivatives. Atmospheric pressure photoionization combined with higher order MS/MSn using high-resolution mass spectrometry (APPI-HR-CID-MSn) and electronic structure calculations using density functional theory were used to determine the chemical structure of observed [M-H]+ ions. As a result, the higher order MSn (n = 3) experiments revealed a reversed Diels-Alder fragmentation mechanism, leading to a common fragment ion at m/z 322 from the studied [M1-5-H]+ ion species. In addition, the calculation for two chemical structure models (N-alkyl-TPD1 and N-alkyl-TPD5) showed that the fragment structure, resulting from the removal of the hydrogen atom connected to the third carbon atom of the N-alkyl side chain, has a more stable cyclic form compared with the linear one. The proposed chemical structure of the N-alkyl TPD ion species, following the loss of a single hydrogen atom, was revealed during APPI-HR-CID-MSn (n= 3) experiments on the [M-H]+ species. Hydrogen radical (H•) abstraction from the alkyl side chain (e.g., hexyl, heptyl, octyl, 2-ethylhexyl, and nonyl) triggered a rearrangement in the radical cation structure of the N-alkyl-TPD derivatives, initiating cyclization and forming a six-membered ring that connects the oxygen atom to the third carbon atom in the alkyl chain. In addition, theoretical calculations supported the APPI-HR-CID-MSn (n = 3) experiments by demonstrating that the proposed chemical structure, resulting from the intramolecular cyclization of the N-alkyl-TPD ion species, was stable in the presence of chlorobenzene. These findings will aid the structural determination and elucidation of molecules with similar core structures.

Independent LUMO Reactivity in Mesoionic N‐Heterocyclic Thiones: Synthesis of a Stable Radical Anion

AbstractMesoionic compounds, with positive and negative charges, are expected to have dual‐site highest occupied molecular orbital (HOMO, donor) and lowest unoccupied molecular orbital (LUMO, acceptor) reactivity. Herein, we report a novel class of air‐stable mesoionic N‐heterocyclic thiones (mNHTs) synthesized from abnormal N‐heterocyclic carbenes (aNHCs). DFT studies revealed a highly polarized exocyclic thione moiety and computed Fukui function analysis suggests the dual‐site HOMO/LUMO reactivity of mNHTs predicting donor property at the negatively charged ‘S’ center while acceptor property at the cationic imidazole ring. The independent LUMO reactivity of the mNHT was realized by its chemical reduction to an elusive radical anion, which was characterized by a single crystal X‐raydiffraction study. Further, we explore the reactivity of radical anion for the activation of SO2 gas, C−Br bonds of aryl bromide and photocatalytic functionalization of C−X (X = F, Br) bonds. This work unlocks the independent LUMO reactivity of a mesoionic compound.

Enantioselective Electrocatalysis for Cross‐Dehydrogenative Heteroarylation with Indoles, Pyrroles, and Furans

AbstractOxidative cross‐dehydrogenative C−H/C−H functionalizations represent an exemplary approach for synthesizing carbonyl compounds via α‐heteroarylation. Here we present the development of a direct anodic oxidative coupling process between 2‐acylimidazoles and divergent heterocyclic systems including indole, pyrrole, and furan, facilitated by ferrocene‐assisted asymmetric nickel electrocatalysis with high levels of enantioselectivity. Mechanistic investigations indicate that the reaction initially involves the formation of a chiral Ni‐bound α‐carbonyl radical, which is then captured by the heteroarene radical cation via intermolecular stereoselective radical/radical cation coupling. The mild, scalable, and robust reaction conditions allow for a broad substrate scope and excellent functional group tolerance, enabling access to a wide range of chiral hetero‐compounds. The consequential α‐heteroaromatic carbonyl products can potentially be transformed into a plethora of synthetically valuable frameworks, as exemplified by their application in the asymmetric total synthesis of (−)‐COX‐2 inhibitor, (+)‐acremoauxin A, and (+)‐pemedolac.

Enhancing CO2 uptake by aqueous K2CO3 solutions using H2O2‐derived reactive oxygen species: Novel rate promotion for CCU processes

AbstractThis study introduces a novel approach to promote CO2 absorption by aqueous K2CO3 solutions through the in‐situ generation of reactive oxygen species (ROS) via the alkali activation of H2O2. The superoxide radical anion (O2•‐) is recognized as a major contributor in this process, with its presence confirmed by UV‐Vis (Ultraviolet–visible) spectroscopy through the characteristic diformazan peak formed from the reaction between nitro blue tetrazolium (NBT) and superoxide. CO2 absorption experiments and 13C NMR (Carbon‐13 nuclear magnetic resonance) characterization demonstrate the enhanced efficiency of the promoted solution in both CO2 absorption and the conversion of K2CO3 to KHCO3. Comparative analysis with traditional promoters reveals the superior kinetic performance of the H2O2‐promoted system at room temperature. Notably, our system yields pure KHCO3 without by‐products, making it highly suitable for carbon capture and utilization (CCU) by enabling versatile subsequent transformation processes. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

INFLUENCE OF SODIUM GLUTAMATE ON REACTIVE OXYGEN AND NITROGEN SPECIES PRODUCTION IN KIDNEY TISSUES OF RATS UNDER ACUTE DESYNCHRONIZATION AND LIPOPOLYSACCHARIDE-INDUCED SYSTEMIC INFLAMMATORY RESPONSE

The study investigated the effect of sodium glutamate on the production of reactive oxygen and nitrogen species (ROS/RNS) in kidney tissues of rats under conditions of acute desynchronization (AD) and lipopolysaccharide (LPS)-induced systemic inflammatory response (SIR) and, thus, contributed to a deeper understanding of the mechanisms involved in the development of renal dysfunction under these conditions. The experiment was conducted on 21 male Wistar rats (210-230 g), randomly divided into three groups: intact animals, a group exposed to AD modeling under LPS-induced systemic inflammatory response (Group II), and a group (Group 3) exposed to AD modeling under LPS-induced systemic inflammatory response, who received sodium glutamate in a dose of 20 mg/kg. The administration of sodium glutamate significantly increased the generation rate of the superoxide anion radical by 13.8% through microsomal monooxygenases, by 8.7% through the mitochondrial respiratory chain, and by 7.7% through leukocyte NADPH oxidase compared to Group 2. However, sodium glutamate did not affect the total NO synthase activity or the activity of its constitutive and inducible isozymes in the kidney homogenate compared to Group 2. The uncoupling index of constitutive NO synthases in kidney tissues also remained unchanged under the administration of sodium glutamate, but the peroxynitrites were 20.5% higher, and S-nitrosothiols were 11.6% higher, than in group 2. The findings indicate that sodium glutamate significantly increases oxidative-nitrosative stress in rat kidney tissues under AD and LPS-induced SIR, resulting in excessive ROS/RNS formation.

Foliar application of Verticillium dahliae Aspf2‐like protein improved the heat tolerance of creeping bentgrass by regulating photosynthetic and antioxidant capabilities

AbstractContinuous high ambient temperature in hot summer months leads to a sharp decline in turf quality of cool‐season turfgrass. Verticillium dahliae Aspf2‐like protein (VDAL) is a secretory protein of V. dahliae that can improve crop yield and resistance to disease, but its role in improving heat tolerance of cool‐season turfgrass has not been reported so far. The objectives of this study were to explore the effect and mechanism of foliar application of VDAL on improving heat tolerance in cool‐season creeping bentgrass (Agrostis stolonifera) and to further examine the advantage of foliar spraying with VDAL in mitigating summer bentgrass decline (SBD) in the US transition zone or other regions with similar climate. The results demonstrated that the optimal dose of VDAL for improving thermotolerance of two creeping bentgrass cultivars (heat‐tolerant 13 M and heat‐sensitive Seaside II) was screened as 0.2 g L−1 based on analyses of chlorophyll content, photochemical efficiency of PSII, and cell membrane stability under controlled heat stress conditions. Foliar application of the optimal dose of VDAL significantly restricted chlorophyll loss under heat stress and also alleviated heat‐induced declines in net photosynthetic rate, transpiration rate, stomatal conductance, and water use efficiency. In addition, overaccumulations of superoxide anion radical and hydrogen peroxide could be significantly alleviated by the exogenous application of VDAL through improving the activity of antioxidant enzymes including superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase in two cultivars. A further 2‐year field trial showed that foliar application of VDAL improved turf quality, chlorophyll content, photochemical efficiency, and cell membrane stability of the two cultivars during hot summer months of 2022 and 2023. The results indicate that the appropriate dose of VDAL plays a positive role in photosynthetic performance and antioxidant capacity for thermotolerance of creeping bentgrass, and foliar application of VDAL could be considered an effective approach for alleviating SBD.

THE EFFECT OF NF-ΚB ON THE INTENSITY OF OXIDATIVE STRESS IN THE CEREBRAL CORTEX OF RATS UNDER THE COMBINED INFLUENCE OF THE LIGHT-DARK CYCLE, SYSTEMIC INFLAMMATORY RESPONSE, AND SODIUM GLUTAMATE ADMINISTRATION

To date, scientists have confirmed the link between the development of oxidative stress and disruptions in the light regime, as well as the systemic inflammatory response. The impact of monosodium glutamate on increasing oxidative damage to rat brain tissue has also been identified. The aim of this study was to investigate the role of the transcription factor NF-κB by examining the effect of its inhibitor, ammonium pyrrolidinedithiocarbamate, on the development of oxidative stress in the cerebral hemispheres of rats, in combination with acute desynchronosis, systemic inflammatory response, and monosodium glutamate administration. The study was conducted on 45 white Wistar rats weighing 150-200 g, divided into three groups: control (n=15), a group subjected to a combination of acute desynchronosis, systemic inflammatory response, and sodium glutamate administration (n=15), and a group exposed to the combination of acute desynchronosis, systemic inflammatory response, and received sodium glutamate and pyrrolidinedithiocarbamate (n=15). To induce acute desynchronosis, the rats were initially kept under a regular light-dark cycle (12 hours of light, 12 hours of darkness) for 3 weeks, followed by a shift in the light-dark phases by 6 hours back over the next 3 days. The systemic inflammatory response was modeled through intraperitoneal administration of Salmonella typhi lipopolysaccharide. During the first week, lipopolysaccharide was administered three times at a dose of 0.4 μg per 1 kg of body weight, and during the following seven weeks, it was given once a week. Sodium glutamate, at a dose of 30 mg/kg, dissolved in 0.5 ml of distilled water, was administered intragastrically for 20 days. The NF-kB activation inhibitor ammonium pyrrolidinedithiocarbamate (Sigma-Aldrich, Inc., USA) was administered at a dose of 76 mg/kg three times a week for 20 days. In a 10% homogenate of the cerebral hemispheres, the following were measured: the rate of superoxide anion radical production, the content of thiobarbituric acid-reactive substances (TBARS), the increase in these parameters, as well as the activity of catalase and superoxide dismutase. Administration of pyrrolidinedithiocarbamate in combination with acute desynchronosis, systemic inflammatory response, and sodium glutamate reduced the rate of basic superoxide anion radical production by 10%, NADPH-induced production by 17.6%, NADH-induced production by 13%, reduced the concentration and growth of TBC-active products by 6.6% and 14.6%, respectively, increased the activity of superoxide dismutase by 35.2%, catalase by 10.5% compared to the group exposed to the combination of acute desynchronosis, systemic inflammatory response, and sodium glutamate administration. Conclusion. The administration of pyrrolidinedithiocarbamate in combination with a systemic inflammatory response, acute desynchronosis and the action of sodium glutamate reduces the production of the superoxide anion radical, the concentration and increase in TBC-active products, enhances antioxidant protection that indicates the possible influence of the nuclear factor NF-κB on the development of oxidative processes in the cerebral hemispheres of rats.

Faster Excited-State Intramolecular Electron Transfer from Perylenediimide Dianion Compared to Its Radical Anion.

The properties of the excited perylenediimide dianion (PDI2-∗) and its intramolecular electron transfer (ET) behavior were examined using femtosecond laser flash photolysis on PDI2- and PDI2--acceptor (A) dyads. Upon laser excitation, the dianion of PDI first generated a singlet (S1) state, followed by a triplet (T1) state. In all of the dyads, rate constants of the intramolecular ET from PDI2-∗ (S1) varied with the driving forces. Comparison of the PDI2-∗-A and PDI•-∗-A dyad systems revealed higher rate constants for the ET from PDI2-∗ than from PDI•-∗, which can be attributed to the difference in electronic coupling for the ET. These findings elucidate the previously unexplored photoinduced ET characteristics of PDI2-, thereby advancing the groundwork for photochemical studies of excited multi-ions and their applications in related materials.

Frustrated Radical Pairs: From Fleeting Intermediates to Isolable Species.

We present the design and comprehensive investigation of stable para-substituted triarylamine-2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) radical ion pairs (RIPs) generated via single-electron transfer (SET). We quantified the degree of SET in both solution and solid phases, utilising a suite of spectroscopic techniques including IR, EPR, NMR, and single-crystal X-ray diffraction (SC-XRD). Our findings reveal that the extent of SET is significantly influenced by the nature of the substituents (MeO > tBu > Br) and the polarity of the solvent (MeCN > DCM > toluene). The radical ion pair [(pMeOPh)3N]•+[DDQ]•- was unambiguously identified using EPR and UV-vis spectroscopy, and its structure was confirmed by SC-XRD. Detailed analysis indicates an open-shell singlet ground state with a thermally accessible triplet state, as corroborated by EPR, magnetic susceptibility measurements, and DFT calculations. This study offers crucial insights into the mechanistic pathways of RIP formation and tuning both in solution and solid states, laying the groundwork for future exploration of their reactivity and potential applications.

An Isolable Triarylphosphine Radical Cation Electronically Stabilized by Through-Space Radical Delocalization

An Isolable Triarylphosphine Radical Cation Electronically Stabilized by Through-Space Radical Delocalization

Synthesis of Bicyclo[3.2.0]heptanes by Organophotoredox Catalytic Diastereoselective Anion Radical [2+2] Photocycloadditions of Arylenones under Batch and Flow Conditions

AbstractIn this study, the anion radical [2+2] photocycloaddition of aryl‐enones was investigated under batch and flow conditions. The reaction was promoted by LiBr as a Lewis acid and catalyzed by Eosin Y under visible light irradiation. Symmetrical enones and asymmetrical unsaturated ketoesters were effectively cyclized to yield substituted bicyclo[3.2.0]heptanes in high yield and diastereoselectivity. Through the exploration of different experimental setups and reaction conditions, a precise control over the diastereoselectivity of the process was achieved, favoring the formation of either cis or trans substituted bicyclo[3.2.0]heptanes. In‐flow experiments allowed to further improve the efficiency of the methodology, leading to higher productivity and space time yields. Furthermore, DFT investigations were conducted in order to elucidate the reaction mechanism.

Artificial Light-Harvesting Systems with a Three-Step Sequential Energy Transfer Mechanism for Efficient Photocatalytic Minisci-Type Late-Stage Functionalization.

The natural process of photosynthesis involves a series of consecutive energy transfers, but achieving more steps of efficient energy transfer and photocatalytic organic conversion in artificial light-harvesting systems (ALHSs) continues to pose a significant challenge. In the present investigation, a range of ALHSs showcasing a sophisticated three-step energy transfer mechanism is designed, which are meticulously crafted using pillar[5]arene (WP[5]) and p-phenylenevinylene derivative (PPTPy), utilizing host-guest interactions as energy donors. Three distinct types of fluorescent dyes, namely Rhodamine B (RhB), Sulforhodamine 101 (SR101), and Cyanine 5 (Cy5), are employed as acceptors of energy. Starting from PPTPy-2WP[5], energy is sequentially transferred to RhB, SR101, and Cy5, successfully constructing a multi-step continuous energy transfer system with high energy transfer efficiency. More interestingly, as energy is progressively transferred, the efficiency of superoxide anion radical (O2 •-) generation gradually increased, while the efficiency of singlet oxygen (1O2) generation decreased, achieving the transformation from type II photosensitizer to type I photosensitizer. Furthermore, in order to fully utilize the energy harvested and reactive oxygen species (ROS) obtained, the ALHSs employ a multi-step sequential energy transfer process to enhance Minisci-type alkylation reactions with aldehydes through photocatalysis for late-stage functionalization in an aqueous environment, achieving a 91% yield.

On the Photosensitizer Activity From Psoralen in Lipid and Aqueous Media: A Theoretical Study

ABSTRACTThe photosensitizer mechanism by the psoralen (PSO) reacts to produce reactive oxygen species has not been thoroughly studied; thus, this work was carried out a study of the reaction and mechanism involved in the photosensitizer activity of PSO, employing M06‐2X/6‐311++G(d,p) of the density functional theory. There is a competition between the generation of radical anion superoxide (type I mechanism) and the singlet oxygen molecule (type II mechanism) in lipid media; therefore, the ROS anion superoxide and singlet oxygen could be formed as products of the reaction involved in the photosensitizer activity of PSO in lipid media. In aqueous media, the reaction involved in the photosensitizer activity of PSO was only attributed to the type I mechanism; hence, in aqueous media, the photosensitizer activity of PSO yielded the anion superoxide. The present study supports the photosensitizer activity of the PSO in lipid and aqueous media. It enhances the knowledge of these reactions in different media and their application to reactivity, including the physiology media.

Insights into C-H Activation Reactivity of Fe (IV)O Porphyrinoid Complexes: A Computational Investigation.

This work presents a detailed comparative analysis of C-H activations catalyzed by three different Fe(IV)O porphyrinoid complexes. The study considers the usual heme porphyrin (complex I) as the base compound, porphyrazine (complex II), which is obtained by replacing carbon with nitrogen at the meso position, and phthalocyanine (complex III), which is obtained through the peripheral benzoannulation of porphyrazine. The focus here is to explore the impact of bridging groups and peripheral functionalization in heme systems on reactivity. Factors such as distortion energy and electron acceptor orbitals significantly affect the overall reactivity. The effect of substitution on quantum mechanical tunneling, using H/D kinetic isotope effect studies, is also included. The results reveal a fascinating reactivity order: meso nitrogen substitution enhances reactivity, while additional benzo-annulation hinders reactivity, leading to the order complex II > complex I > complex III. In comparison to the usual Cpd I, which is Fe(IV)O-porphyrin π cation radical with an -SH axial ligand, complex II was found to be more reactive. The electron affinity of the Fe(IV)O complexes and the dissociation energy of the forming Fe(IV)O-H bond aligns with observed reactivity trend. These findings support the use of accessible iron frameworks derived from porphyrin in C-H activation processes.