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As the field of preclinical research on photosensitizers (PSs) for anticancer photodynamic therapy (PDT) continues to expand, a focused effort is underway to develop agents with innovative molecular structures that offer enhanced targeting, selectivity, activation, and imaging capabilities. In this context, we introduce two new heavy-atom-free PSs, DBXI and DBAI, characterized by a twisted π-conjugation framework. This innovative approach enhances the spin-orbit coupling (SOC) between the singlet excited state (S 1 ) and the triplet state (T 1 ), resulting in improved and efficient intersystem crossing (ISC). Both PSs are highly effective in producing reactive oxygen species (ROS), including singlet oxygen and/or superoxide species. Additionally, they also demonstrate remarkably strong fluorescence emission. Indeed, in addition to providing exceptional photocytotoxicity, this emissive feature, generally lacking in other reported structures, allows for the precise monitoring of the PSs' distribution within specific cellular organelles even at nanomolar concentrations. These findings underscore the dual functionality of these PSs, serving as both fluorescent imaging probes and light-activated therapeutic agents, emphasizing their potential as versatile and multifunctional tools in the field of PDT.

Controlling the formation of photoexcited triplet states is critical for many (photo)chemical and physical applications. Here, we demonstrate that a permanent out-of-plane distortion of the benzothioxanthene imide (BTI) dye promotes intersystem crossing by increasing spin-orbit coupling. This manipulation was achieved through a subtle chemical modification, specifically the bay-area methylation. Consequently, this simple yet efficient approach expands the catalog of known molecular engineering strategies for synthesizing heavy atom-free, dual redox-active, yet still emissive and synthetically accessible photosensitizers., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Recent advances in visible light photocatalysis represent a significant stride towards sustainable catalytic chemistry. However, its successful implementation in fine chemical production remains challenging and requires careful optimization of available photocatalysts. Our work aims to structurally modify bioinspired porphyrin catalysts, addressing issues related to their laborious synthesis and low solubility, with the goal of increasing their efficiency and developing reusable catalytic systems. We have demonstrated the catalytic potential of readily available meso -tetrakis[4-(diethoxyphosphoryl)phenyl]porphyrins (M(TPPP)). Novel metal (Pd(II), Co(II) and In(III)) complexes with this ligand were prepared in good yields. These chromophores were characterized in solution using spectroscopic (NMR, UV-vis, fluorescence) and electrochemical methods. The introduction of phosphonate groups on the phenyl substituents of meso -tetraphenylporphyrins (M(TPP)) improves solubility in polar organic solvents without significantly altering the photophysical properties and photostability of complexes. This structural modification also leads to easier reductions and harder oxidations of the macrocycle for all investigated complexes compared to the corresponding TPP derivatives. The free base porphyrin, zinc(II), palladium(II), and indium(III) complexes were studied as photocatalysts for oxidation of sulfides to sulfoxides using molecular oxygen as a terminal oxidant. Both dialkyl and alkyl aryl sulfides were quantitatively transformed into sulfoxides under blue LED irradiation in the acetonitrile-water mixture (10 : 1 v/v) with a low loading (0.005-0.05 mol%) of porphyrin photocatalysts, where H 2 (TPPP) and Pd(TPPP) were found to be the most efficient. The reaction mechanism was studied using photoluminescence and EPR spectroscopies. Then, to access reusable catalysts, water-soluble derivatives bearing phosphonic acid groups, H 2 (TPPP-A) and Pd(TPPP-A), were prepared in high yields. These compounds were characterized using spectroscopic methods. Single-crystal X-ray diffraction analysis of Pd(TPPP-A) reveals that the complex forms a 3D hydrogen-bonded organic framework (HOF) in the solid state. Both H 2 (TPPP-A) and Pd(TPPP-A) were found to catalyze the photooxidation of sulfides by molecular oxygen in the acetonitrile-water mixture (1 : 1 v/v), while only Pd(TPPP-A) resulted in selective production of sulfoxides. The complex Pd(TPPP-A) was easily recovered through extraction in the aqueous phase and successfully reused in five consecutive cycles of the sulfoxidation reaction.

Electron transport chains (ETCs) are ubiquitous in nearly all living systems. Replicating the complexity and control inherent in these multicomponent systems using ensembles of small molecules opens up promising avenues for molecular therapeutics, catalyst design, and the development of innovative energy conversion and storage systems. Here, we present a noncovalent, multistep artificial electron transport chains comprising cyclo[8]pyrrole ( 1 ), a meso -aryl hexaphyrin(1.0.1.0.1.0) (naphthorosarin 2 ), and the small molecules I 2 and trifluoroacetic acid (TFA). Specifically, we show that 1) electron transfer occurs from 1 to give I 3 - upon the addition of I 2 , 2) proton-coupled electron transfer (PCET) from 1 to give H 3 2 •2+ and H 3 2 + upon the addition of TFA to a dichloromethane mixture of 1 and 2 , and 3) that further, stepwise treatment of 1 and 2 with I 2 and TFA promotes electron transport from 1 to give first I 3 - and then H 3 2 •2+ and H 3 2 + . The present findings are substantiated through UV-vis-NIR, 1 H NMR, electron paramagnetic resonance (EPR) spectroscopic analyses, cyclic voltammetry studies, and DFT calculations. Single-crystal structure analyses were used to characterize compounds in varying redox states., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Dinuclear transition metal complexes with direct metal-metal interactions have the potential to generate unique reactivities and properties. Using asymmetric triazine ligands HN 3 t BuR (R = Et, i Pr, n Bu) featuring different alkyl substituents at 1,3-N centers, we report here the first rational synthesis of 'tetragonal lantern' type Fe(II) triazenides [Fe 2 (N 3 t BuR) 4 ] [R = Et (1), i Pr (2), n Bu (3)] having an exceptionally short Fe-Fe distance (2.167-2.174 Å). Unlike the previously reported lantern structures with related amidinate or guanidinate ligands, highly air-sensitive 1-3 show a lower spin ground state, as indicated by Mössbauer, 1 H NMR and DFT studies.

Metal imine-thiolate complexes, M(NS) 2 are known to undergo imine C-C bond formation to give M(N 2 S 2 ) complexes (M=Co, Ni) containing a redox-active ligand. Although these transfor-mations are not typically quantitative, we demonstrate here that the one-electron reduction of a related Ni bis(imine-thiolate) complex affords the corresponding paramagnetic [Ni(N 2 S 2 )] - anion (2⋅ - ) exclusively; subsequent oxidation with [Cp 2 Fe]BF 4 then affords a high yield of neutral 2 (Cp=η 5 -cyclopentadienyl). Moreover, electrochemical studies indicate that a second one-electron reduction affords the diamagnetic dianion. Both anionic products were isolated and characterized by SC-XRD and their electronic structures were investigated by UV-vis spectro-electrochemistry, EPR and NMR spectroscopy, and DFT studies. These studies show that reduction proceeds primarily on the ligand, with (N 2 S 2 ) 4- containing both thiolate and ring-delocalized anions., (© 2023 Wiley-VCH GmbH.)

Porphyrin based Metal-Organic Frameworks (MOFs) have generated high interest because of their unique combination of light absorption, electron transfer and guest adsorption/desorption properties. In this study, we expand the range of available MOF materials by focusing on the seldom studied porphyrin ligand H 10 TcatPP, functionalized with tetracatecholate coordinating groups. A systematic evaluation of its reactivity with M(iii) cations (Al, Fe, and In) led to the synthesis and isolation of three novel MOF phases. Through a comprehensive characterization approach involving single crystal and powder synchrotron X-ray diffraction (XRD) in combination with the local information gained from spectroscopic techniques, we elucidated the structural features of the solids, which are all based on different inorganic secondary building units (SBUs). All the synthesized MOFs demonstrate an accessible porosity, with one of them presenting mesopores and the highest reported surface area to date for a porphyrin catecholate MOF (>2000 m 2 g -1 ). Eventually, the redox activity of these solids was investigated in a half-cell vs. Li with the aim of evaluating their potential as electrode positive materials for electrochemical energy storage. One of the solids displayed reversibility during cycling at a rather high potential (∼3.4 V vs. Li + /Li), confirming the interest of redox active phenolate ligands for applications involving electron transfer. Our findings expand the library of porphyrin-based MOFs and highlight the potential of phenolate ligands for advancing the field of MOFs for energy storage materials., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Photodynamic therapy (PDT) ideally relies on the administration, selective accumulation and photoactivation of a photosensitizer (PS) into diseased tissues. In this context, we report a new heavy-atom-free fluorescent G-quadruplex (G4) DNA-binding PS, named DBI. We reveal by fluorescence microscopy that DBI preferentially localizes in intraluminal vesicles (ILVs), precursors of exosomes, which are key components of cancer cell proliferation. Moreover, purified exosomal DNA was recognized by a G4-specific antibody, thus highlighting the presence of such G4-forming sequences in the vesicles. Despite the absence of fluorescence signal from DBI in nuclei, light-irradiated DBI-treated cells generated reactive oxygen species (ROS), triggering a 3-fold increase of nuclear G4 foci, slowing fork progression and elevated levels of both DNA base damage, 8-oxoguanine, and double-stranded DNA breaks. Consequently, DBI was found to exert significant phototoxic effects (at nanomolar scale) toward cancer cell lines and tumor organoids. Furthermore, in vivo testing reveals that photoactivation of DBI induces not only G4 formation and DNA damage but also apoptosis in zebrafish, specifically in the area where DBI had accumulated. Collectively, this approach shows significant promise for image-guided PDT., (© The Author(s) 2023. Published by Oxford University Press on behalf of Nucleic Acids Research.)

Synthesis of high quality colloidal Cerium(III) doped yttrium aluminum garnet (Y 3 Al 5 O 12 :Ce 3+ , "YAG:Ce") nanoparticles (NPs) meeting simultaneously both ultra-small size and high photoluminescence (PL) performance is challenging, as generally a particle size/PL trade-off has been observed for this type of nanomaterials. The glycothermal route is capable to yield ultra-fine crystalline colloidal YAG:Ce nanoparticles with a particle size as small as 10 nm but with quantum yield (QY) no more than 20%. In this paper, the first ultra-small YPO 4 -YAG:Ce nanocomposite phosphor particles having an exceptional QY-to-size performance with an QY up to 53% while maintaining the particle size ≈10 nm is reported. The NPs are produced via a phosphoric acid- and extra yttrium acetate-assisted glycothermal synthesis route. Localization of phosphate and extra yttrium entities with respect to cerium centers in the YAG host has been determined by fine structural analysis techniques such as X-ray diffration (XRD), solid state nuclear magnetic resonance (NMR), and high resolution scanning transmission electron microscopy (HR-STEM), and shows distinct YPO 4 and YAG phases. Finally, a correlation between the additive-induced physico-chemical environment change around cerium centers and the increasing PL performance has been suggested based on electron paramagnetic resonance (EPR), X-ray photoelectron spectrometry (XPS) data, and crystallographic simulation studies., (© 2023 The Authors. Small published by Wiley-VCH GmbH.)

Visible light photooxidation of naphthols to produce naphthoquinones, such as the natural product juglone, has been known for decades and has been widely utilized to benchmark the performances of a variety of photocatalytic systems. We discovered that these transformations can occur without the help of a photocatalyst and, even more intriguingly, that the photocatatyst-free process provides higher yields compared to control experiments utilizing state-of-the-art photocatalysts. In addition, we demonstrate that naphthoquinones and their corresponding naphthol precursors can act as alternatives to commonly used organic and organometallic photocatalysts with applications to challenging targets, such as the antimalarial drug artemisinin. This approach was finally transposed in continuous flow reactors where high photocatalyst stability and process efficiency are demonstrated with a 23× improvement in the space-time yield.

Two mononuclear ferric complexes are reported that respond to a pH change with a 27- and 71-fold jump, respectively, in their capacity to accelerate the longitudinal relaxation rate of water-hydrogen nuclei, and this starting from a negligible base value of only 0.06. This unprecedented performance bodes well for tackling the sensitivity issues hampering the development of Molecular MRI. The two chelates also excel in the fully reversible and fatigue-less nature of this phenomenon. The structural reasons for this performance reside in the macrocyclic nature of the hexa-dentate ligand, as well as the presence of a single pendant arm displaying a five-membered lactam or carbamate which show (perturbed) pK a values of 3.5 in the context of this N6 ⇔ ${ \Leftrightarrow }$ N5O1 coordination motif., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Ammonia, NH 3 , is an essential molecule, being part of fertilizers. It is currently synthesized via the Haber-Bosch process, from the very stable dinitrogen molecule, N 2 and dihydrogen, H 2 . This process requires high temperatures and pressures, thereby generating ca 1.6 % of the global CO 2 emissions. Alternative strategies are needed to realize the functionalization of N 2 to NH 3 under mild conditions. Here, we show that boron-centered radicals provide a means of activating N 2 at room temperature and atmospheric pressure whilst allowing a radical process to occur, leading to the production of borylamines. Subsequent hydrolysis released NH 4 + , the acidic form of NH 3 . EPR spectroscopy supported the intermediacy of radicals in the process, corroborated by DFT calculations, which rationalized the mechanism of the N 2 functionalization by R 2 B radicals., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Photodynamic therapy is a clinically approved anticancer modality that employs a light-activated agent (photosensitizer) to generate cytotoxic reactive oxygen species (ROS). There is therefore a growing interest for developing innovative photosensitizing agents with enhanced phototherapeutic performances. Herein, we report on a rational design synthetic procedure that converts the ultrabright benzothioxanthene imide (BTI) dye into three heavy-atom-free thionated compounds featuring close-to-unit singlet oxygen quantum yields. In contrast to the BTI, these thionated analogs display an almost fully quenched fluorescence emission, in agreement with the formation of highly populated triplet states. Indeed, the sequential thionation on the BTI scaffold induces torsion of its skeleton reducing the singlet-triplet energy gaps and enhancing the spin-orbit coupling. These potential PSs show potent cancer-cell ablation under light irradiation while remaining non-toxic under dark condition owing to a photo-cytotoxic mechanism that we believe simultaneously involves singlet oxygen and superoxide species, which could be both characterized in vitro. Our study demonstrates that this simple site-selected thionated platform is an effective strategy to convert conventional carbonyl-containing fluorophores into phototherapeutic agents for anticancer PDT., (© 2022. The Author(s).)

We herein report the synthesis and magnetic properties of a Ni(II)-porphyrin tethered to an imidazole ligand through a flexible electron-responsive mechanical hinge. The latter is capable of undergoing a large amplitude and fully reversible folding motion under the effect of electrical stimulation. This redox-triggered movement is exploited to force the axial coordination of the appended imidazole ligand onto the square-planar Ni(II) center, resulting in a change in its spin state from low spin ( S = 0) to high spin ( S = 1) proceeding with an 80% switching efficiency. The driving force of this reversible folding motion is the π-dimerization between two electrogenerated viologen cation radicals. The folding motion and the associated spin state switching are demonstrated on the grounds of NMR, (spectro)electrochemical, and magnetic data supported by quantum calculations.

The activation of SF 6 , a potent greenhouse gas, under metal-free and visible light conditions is reported. Herein, mechanistic investigations including EPR spectroscopy, NMR studies and cyclic voltammetry allowed the rational design of a new fluorinating reagent which was synthesized from the 2-electron activation of SF 6 with commercially available TDAE. This new SF 5 -based reagent was efficiently employed for the deoxyfluorination of CO 2 and the fluorinative desulfurization of CS 2 allowing the formation of useful fluorinated amines. Moreover, for the first time we demonstrated that our SF 5 -based reagent could afford the mild generation of Cl-SF 5 gas. This finding was exploited for the chloro-pentafluorosulfanylation of alkynes and alkenes., (© 2022 Wiley-VCH GmbH.)

The first metal-free procedure for the synthesis of arylsulfonyl fluorides is reported. Under organo-photoredox conditions, aryl diazonium salts react with a readily available SO 2 source (DABSO) to afford the desired product through simple nucleophilic fluorination. The reaction tolerates the presence of both electron-rich and -poor aryls and demonstrated a broad functional group tolerance. To shed the light on the reaction mechanism, several experimental techniques were combined, including fluorescence, NMR, and EPR spectroscopy as well as DFT calculations., (© 2021 Wiley-VCH GmbH.)

The use of photosensitizers immobilized on mesoporous materials to produce singlet oxygen ( 1 O 2 ) has opened a new way to synthetic and environmental applications due to the fast development of flow photochemistry and continuous-flow microreactors. 1 O 2 -based photosensitized processes can be employed for the degradation of organic pollutants in an aqueous medium and the photosensitizer can be covalently attached to the support and separated from the effluent reducing the environmental impact. The aim of the present paper is to evaluate the 1 O 2 generation of Rose Bengal (RB) in homogeneous and heterogeneous systems using in-operando evaluation. Mesoporous SiO 2 nanoparticles (MSNs) were successfully conjugated with RB (MSN-RB) and electron paramagnetic resonance (EPR) spectroscopy in combination with the spin trap TEMP was employed to obtain paramagnetic TEMPO via generated 1 O 2 when RB or MSN-RB are exposed to visible light. Additionally, EPR/DMPO was used to exclude the possible generation of other reactive oxygen species (ROS) by the functionalized nanoparticles. We found that in situ 1 O 2 generation was enhanced when the same amount of RB is immobilized inside of mesoporous SiO 2 .

This account highlights some of our recent work on photoinduced trifluoromethylselenolation reactions. This research program relies primarily on the design of a new key shelf-stable selenating reagent that can be involved in various radical processes In particular, we demonstrated that trifluoromethylselenolation of arenes, alkenes, alkynes as well as aliphatic organic building blocks can be readily achieved under visible-light irradiation. Mechanistic investigations based on 19 F NMR studies, EPR spectroscopy, cyclic voltammetry and luminescence studies allowed us to shed the light on the different proposed mechanisms in the designed methodologies. The applicative potential of these strategies was further demonstrated through the synthesis of bioactive analogue containing SeCF 3 motif., (© 2021 The Chemical Society of Japan & Wiley-VCH GmbH.)

Near room temperature hysteretic thermo-induced valence tautomerism was discovered in a layered 2D-coordination polymer of manganese(ii) with nitronyl nitroxide radicals separated by ClO4- anions (1). This opens a novel approach towards switchable materials with hysteresis and under ambient conditions with prospects for applications and for investigating solid-state intramolecular electron transfers. Herein, two new compounds with similar layered structures where the anions (X) are BF4- (2) or PF6- (3) are presented. Their magnetic behaviors also reveal hysteretic thermo-induced valence tautomeric conversions but in two steps and evidencing a strong effect of the anion. This occurs near room temperature (278-220 K) for 2 and higher for 3 (380-330 K). Their single crystal structures at different temperatures show that this involves two successive thermally-triggered electron transfers with switching between three redox tautomers formulated as {[MnII2-yMnIIIy(NITIm)3-y(NITRed)y]X}n, where y is temperature dependent. Upon cooling from the high-temperature redox-tautomer (y = 0) to the intermediate one (y = 1), half of the manganese(ii) centers are oxidized to manganese(iii) and 1/3 of the nitronyl nitroxide radicals (NITIm-) are reduced to the aminoxyl form (NITRed2-). On further cooling, the second half of the manganese(ii) centers are oxidized and another 1/3 of the radicals are reduced to reach the low-temperature redox-tautomer (y = 2). Upon reheating, reverse electron transfers occur. This is complementarily supported by X-ray powder measurements, differential scanning calorimetry, and electron paramagnetic resonance and Raman spectroscopies. These multi-stable compounds in which manganese ions exchange reversibly their electron with the nitronyl nitroxide radical are outstanding rare examples of two-step valence tautomerism in the solid state promoted by the polymeric structure.

The plasmonic features of gold nanomaterials provide intriguing optical effects which can find potential applications in various fields. These effects depend strongly on the size and shape of the metal nanostructures. For instance, Au bipyramids (AuBPs) exhibit intense and well-defined plasmon resonance, easily tunable by controlling their aspect ratio, which can act synergistically with chromophores for enhancing their photophysical properties. In Rose Bengal-nanoparticle systems it is now well established that the control of the dye-to-nanoparticle distance ranging from 10 to 20 nm as well as spectral overlaps is crucial to achieve appropriate coupling between the plasmon resonance and the dye, thus affecting its ability to generate singlet oxygen ( 1 O 2 ). We have developed AuBPs@mSiO 2 core-shell nanostructures that provide control over the distance between the metal surface and the photosensitizers for improving the production of 1 O 2 (metal-enhanced 1 O 2 production - ME 1 O 2 ). A drastic enhancement of 1 O 2 generation is evidenced for the resulting AuBPs and AuBPs@mSiO 2 in the presence of Rose Bengal, using a combination of three indirect methods of 1 O 2 detection, namely in operando Electron Paramagnetic Resonance (EPR) with 2,2,6,6-tetramethylpiperidine (TEMP) as a chemical trap, photooxygenation of the fluorescence probe anthracene-9,10-dipropionic acid (ADPA), and photooxygenation of methionine to methionine sulfoxide in a segmented flow microreactor., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Manganese(iii) complexes were synthesized by one-electron transfer from a Mn(ii) ion to the imino nitroxide radical 2-(2-imidazolyl)-4,4,5,5-tetramethylimidazoline-1-oxyl (IMImH) in methanol. After the manganese ions attained the +III oxidation state, the imino nitroxide radicals were found to be irreversibly reduced in the complexes. Depending on the synthesis conditions, two complexes differing by their counter-anions were isolated as single crystals. These are [Mn(IMHIm) 2 (MeOH) 2 ]ClO 4 ·H 2 O (1) and [Mn(IMHIm) 2 (MeOH) 2 ]PF 6 (2), which crystallize in the monoclinic P2 1 /n and triclinic P1[combining macron] space groups, respectively. The two complexes show Jahn-Teller distortions typical of Mn(iii) centres and only reduced radicals are coordinated, as indicated by the N-O bond lengths and electroneutrality. In addition, the crystal structure analyses reveal two intermolecular hydrogen bonding networks. One involves counter-anions, water molecules and reduced radicals, and the other involves coordinated methanol molecules and imidazole moieties. These intermolecular interactions are driving forces that stabilize the two complexes. They also suggest that the tautomer is in the amino imine-oxide form after reduction of the radical and reveal the deprotonation of the imidazole ring, which is required for electroneutrality. This assessment is supported by single-crystal X-ray diffraction, EPR and Raman spectroscopy as well as magnetic and electrochemical studies.

Given that literature data may give inconsistent results on the effect of a drug on lipid membrane properties, this work aims to investigate the impact of the liposome composition and experimental protocol design on glucocorticoids (GRs: cortisol, cortisone, fludrocortisone acetate, methylprednisolone, prednisolone and prednisone)-modulating membrane fluidity and permeability. GRs-loaded liposomes consisting of dipalmitoylphosphatidylcholine (DPPC) and cholesterol (CHOL) were prepared by reverse phase evaporation technique (REV) at DPPC:CHOL:GR molar ratios of 100:100:2.5, and 100:100:10. The formulations were characterized for their size and homogeneity, encapsulation efficiency and loading rates of GRs, incorporation rates and loading rates of DPPC and CHOL. Changes in DPPC membrane fluidity (CHOL% 0, 10, 20, 30 and 100) after exposure to methylprednisolone were monitored by using 5- and 16-doxyl stearic acids (DSA) as spin probes. For permeability studies, the above-mentioned GRs-loaded liposomes and the preformed liposomes exposed to GRs (2.5 mol%) were compared for the leakage of an encapsulated fluorescent dye, sulforhodamine B (SRB), at 37 °C in buffer (pH 7.5) containing NaCl. The SRB release kinetics were analyzed by the Higuchi model for two release phases (from 0 to 10 h, and from 10 to 48 h). All formulations exhibited a monodispersed size distribution of liposomes with a mean particle value close to 0.4 μm, also the DPPC and CHOL were highly incorporated (>95%). High loading rate values of DPPC and CHOL were also obtained. Except for fludrocortisone acetate (51%) and prednisolone (77%), high loading rate values of GRs were obtained (>81%). Fluidity and permeability studies showed that the GR concentration, CHOL content, experimental protocol design including the period of incubation represent critical parameters to be considered in analyzing the effect of drugs on the membrane properties., (Copyright © 2018 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.)

The reactivity of fluoroalkylselenotoluenesulfonates with unsaturated substrates is explored herein. The direct activation of these shelf-stable reagents under visible light allows the double functionalisation of alkenes or alkynes efficiently, leading to a wide range of β-fluoroalkylselenolated sulfones. Mechanistic investigations have been undertaken supporting the formation of radical intermediates.

The first visible-light-mediated synthesis of trifluoromethylselenolated arenes under metal-free conditions is reported. The use of an organic photocatalyst enables the trifluoromethylselenolation of arene diazonium salts using the shelf-stable reagent trifluoromethyl tolueneselenosulfonate at room temperature. The reaction does not require the presence of any additives and shows high functional-group tolerance, covering a very broad range of starting materials. Mechanistic investigations, including EPR spectroscopy, luminescence investigations, and cyclic voltammetry allow rationalization of the reaction mechanism., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The preparation of reduced TiO 2 photocatalysts with high Ti 3+ concentration is a great challenge due to their instability in air. Here we report a new approach for the synthesis of reduced TiO 2 with {001} facets exposed via a hydrothermal process. By the introduction of fluoride atoms, {001} and {101} facets are formed, which act as hole and electron collectors, respectively, for charge separation. By adjusting the volume of HF added, a rutile-anatase transition is observed for the first time. EPR spectra confirm the generation of Ti 3+ species in the bulk of TiO 2 , and Ti 3+ signals are studied in the anatase and rutile phases separately. The quantified EPR shows that reduced TiO 2 samples present 14 000-fold more spins compared to the pristine TiO 2 , and the intensity can reach as high as 24.6 × 10 19 spins per g. The obtained samples also have a unique disordered layer with a thickness of 1-2 nm on their surfaces, which contributes to the stabilization of the formed Ti 3+ species by preventing their oxidation in air. In addition, the synthesized reduced TiO 2 samples also exhibit wide-spectrum solar light absorption, especially in the near-infrared region. Owing to their enhanced solar light absorption, improved electron-hole separation and special facet exposure, these samples exhibit enhanced photocatalytic CO 2 reduction performance and high CH 4 selectivity under solar light irradiation, in the absence of a noble metal Pt as a co-catalyst.

The manganese-nitronyl-nitroxide two-dimensional coordination polymer {[Mn 2 (NITIm) 3 ]ClO 4 } n (1) (NITImH = 2-(2-imidazolyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-3-oxide-1-oxyl) undergoes an unusual hysteretic thermo-induced valence tautomeric transition near room temperature, during which the manganese(II) ions are oxidized to manganese(III) and two of the three deprotonated radicals (NITIm - ) are reduced to their diamagnetic aminoxyl form (denoted NIT Red 2- ). Upon cooling, the high-temperature species {[Mn II 2 (NITIm) 3 ]ClO 4 } n (1 HT ) turns into the low-temperature species {[Mn III 2 (NIT Red ) 2 (NITIm)]ClO 4 } n (1 LT ) around 274 K, while on heating the process is reversed at about 287 K. This valence tautomeric phenomenon is supported by temperature-dependent magnetic susceptibility measurements, differential scanning calorimetry (DSC), crystal structure determination, UV-vis absorption, X-ray absorption (XAS), and emission (XES) and electron paramagnetic resonance (EPR) spectroscopies in the solid state.

The photocatalytic properties of TiO2 modified by chromium are usually found to depend strongly on the preparation method. To clarify this problem, two series of chromium-doped titania with a chromium content of up to 1.56 wt % have been prepared under hydrothermal conditions: the first series (Cr:TiO2) is intended to dope the bulk of TiO2, whereas the second series (Cr/TiO2) is intended to load the surface of TiO2 with Cr. The catalytic properties have been compared in the photocatalytic oxidation of formic acid. Characterization data provides evidence that in the Cr/TiO2 catalysts chromium is located on the surface of TiO2 as amorphous CrOOH clusters. In contrast, in the Cr:TiO2 series, chromium is mostly dissolved in the titania lattice, although a minor part is still present on the surface. Photocatalytic tests show that both series of chromium-doped titania demonstrate visible-light-driven photo-oxidation activity. Surface-doped Cr/TiO2 solids appear to be more efficient photocatalysts than the bulk-doped Cr:TiO2 counterparts., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Three copper(II)@hemicryptophane complexes with various cavity sizes and shapes, Cu(II)@1, Cu(II)@2 and Cu(II)@3, were synthesized and characterized by near-IR/vis and EPR spectroscopies. The spectroscopic data are consistent with the presence of a trigonal-bipyramidal geometry of the N(4)Cu·H(2)O core, in accord with the energy-minimized structures obtained from DFT calculations. Cyclic voltammetry studies in CH(2)Cl(2) showed irreversible redox processes, whereas electrolysis coulometry indicated that Cu(II)/Cu(I) complexes could be interconverted. Electrochemistry data of the complexes stress the crucial role of the cage structure of the hemicryptophane in the thermodynamics of the electron transfer.

Following the structural concept of copper-containing proteins in which dinuclear copper centers are connected by hydroxide bridging ligands, a bidentate copper(II) complex has been incorporated into nano-confined MCM-41 silica by a multistep sequential grafting technique. Characterization by a combination of EPR spectroscopy, X-ray photoelectron spectroscopy (XPS), UV/Vis spectroscopy, IR spectroscopy , and solid-state (13)C and (29)Si cross-polarization magic-angle spinning (CP-MAS) NMR suggests that dinuclear Cu complexes are bridged by hydroxide and other counterions (chloride or perchlorate ions), similar to the situation for EPR-undetectable [Cu(II)···Cu(II)] dimer analogues in biological systems. More importantly, a dynamic mononuclear-dinuclear equilibrium between different coordination modes of copper is observed, which strongly depends on the nature of the counterions (Cl(-) or ClO(4)(-)) in the copper precursor and the pore size of the silica matrix (the so-called confinement effect). A proton-transfer mechanism within the hydrogen-bonding network is suggested to explain the dynamic nature of the dinuclear copper complex supported on the MCM-41 silica., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)