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New nitronyl nitroxide radicals, 2-(4′(5′)-methylimidazol-2′-yl)- and 2-(4′(5′)-trifluoromethylimidazol-2′-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl 3-oxide, were synthesized. The molecular and crystal structures of the paramagnetic trifluoromethyl derivative were determined. A previously unknown type of hydrogen bonding of imidazol-2-yl-substituted nitronyl nitroxides to form ribbons was established. Within the ribbons, the molecules face in the same direction, with all oxygen atoms of the paramagnetic moieties being involved in H-bonding. The spectral and electrochemical properties of the radicals were compared. The first quantum chemical calculations of the electronic spectra of nitronyl nitroxide radicals taking account of the vibrational structure were performed. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS) are double-edged swords in biological systems-they are essential for normal cellular functions but can cause damage when accumulated due to oxidative stress. Manganese superoxide dismutase (MnSOD), located in the mitochondrial matrix, is a key enzyme that neutralizes superoxide radicals (O 2 ), maintaining cellular redox balance and integrity. This review examines the development and therapeutic potential of MnSOD mimetics-synthetic compounds designed to replicate MnSOD's antioxidant activity. We focus on five main types: Mn porphyrins, Mn salens, MitoQ10, nitroxides, and mangafodipir. These mimetics have shown promise in treating a range of oxidative stress-related conditions, including cardiovascular diseases, neurodegenerative disorders, cancer, and metabolic syndromes. By emulating natural antioxidant defenses, MnSOD mimetics offer innovative strategies to combat diseases linked to mitochondrial dysfunction and ROS accumulation. Future research should aim to optimize these compounds for better stability, bioavailability, and safety, paving the way for their translation into effective clinical therapies.•- ), maintaining cellular redox balance and integrity. This review examines the development and therapeutic potential of MnSOD mimetics-synthetic compounds designed to replicate MnSOD's antioxidant activity. We focus on five main types: Mn porphyrins, Mn salens, MitoQ10, nitroxides, and mangafodipir. These mimetics have shown promise in treating a range of oxidative stress-related conditions, including cardiovascular diseases, neurodegenerative disorders, cancer, and metabolic syndromes. By emulating natural antioxidant defenses, MnSOD mimetics offer innovative strategies to combat diseases linked to mitochondrial dysfunction and ROS accumulation. Future research should aim to optimize these compounds for better stability, bioavailability, and safety, paving the way for their translation into effective clinical therapies.

A series of eight nitroxide compounds (four substituted piperidines, three pyrrolidines and one oxo-piperidine) are found to undergo electron transfer to 2'-deoxyribose-peroxyl and the guanyl radical. One-electron oxidation potentials of the nitroxides to oxoammonium cations (oxoammonium reduction potential), E 0' , have been measured against a common redox indicator, chlorpromazine, and found to span the range 751 ± 15 mV to 973 ± 15 mV. Fast chemical reduction of the 2'-deoxyribose-peroxyl radical to the hydroperoxide, generated by • OH radical attack on 2-deoxyribose, dR, in oxygenated aqueous solution, is a redox-dependent reaction, with rate constants of 0.8-3.5 x 10 7 M -1 s -1 , react with the nitroxides in a redox-independent reaction with diffusion rate constants of 1-2 x 10 3 • - . These findings represent a possible antioxidant role for nitroxides in the fast chemical repair of DNA radicals, which is supported by an 8 M -1 s -1 . These findings represent a possible antioxidant role for nitroxides in the fast chemical repair of DNA radicals, which is supported by an in vitro strand break study using a plasmid.

Microbial biofilms are becoming increasingly difficult to treat in the medical setting due to their intrinsic resistance to antibiotics. To combat this, several biofilm dispersal agents are currently being developed as treatments for biofilm infections. Combining biofilm dispersal agents with antibiotics is emerging as a promising strategy to simultaneously disperse and eradicate biofilms or, in some cases, even inhibit biofilm formation. Here we review studies that have investigated the anti-biofilm activity of some well-studied biofilm dispersal agents (e.g., quorum sensing inhibitors, nitric oxide/nitroxides, antimicrobial peptides/amino acids) in combination with antibiotics from various classes. This review aims to directly compare the efficacy of different combination strategies against microbial biofilms and highlight synergistic treatments that warrant further investigation. By comparing across studies that use different measures of efficacy, we can conclude that treating biofilms in vitro and, in some limited cases in vivo, with a combination of an anti-biofilm agent and an antibiotic, appears overall more effective than treating with either compound alone. The review identifies the most promising combination therapies currently under development as biofilm inhibition and eradication therapies.

The assessment of unregulated level of enzyme activity is a crucial parameter for early diagnoses in a wide range of pathologies. In this study, we propose the use of electron paramagnetic resonance (EPR) as an easy method to probe carboxylesterase (CE) enzymatic activity in vitro. For this application, were synthesized two amphiphilic, nitroxide containing esters, namely Tempo‐C12 (T‐C12) and Tempo‐2‐C12 (T‐2‐C12). They exhibit low solubility in water and form stable micelles in which the radicals are EPR almost silent, but the hydrolysis of the ester bond yields narrows and intense EPR signals. The intensity of the EPR signals is proportional to the enzymatic activity. CEs1, CEs2 and esterase from porcine liver (PLE) were investigated. The obtained results show that T‐C12 and T‐2‐C12‐containing systems display a much higher selectivity toward the CEs2, with a Limit of Detection of the same order of those ones obtained with optical methods. [ABSTRACT FROM AUTHOR]

Pyrrolidine nitroxides with four bulky alkyl substituents adjacent to N–O group are known for their high resistance to bioreduction. The 3,4-unsubstituted 2-tert-butyl-2-ethylpyrrolidine-1-oxyls were prepared from the corresponding 2-tert-butyl-1-pyrroline-1-oxides via either the addition of ethinylmagnesium bromide with subsequent hydrogenation or via treatment with ethyllithium. The new nitroxides showed excellent stability to reduction with ascorbate with no evidence for additional large hyperfine couplings in the EPR spectra. [ABSTRACT FROM AUTHOR]

In this context, natural polymer-based carriers (with core-shell structure) have presented multifunctional capabilities and enabled the simultaneous encapsulation of active agents of different physical/chemical properties for their targeted delivery and sustained release. Choosing the right polymer is very important in this process due to its impact on target delivery and controlled release, and therefore, on the bioavailability of active agents. Encapsulation technology comprises enclosing active agents (core materials) within a homogeneous/heterogeneous matrix (wall material) at the micro/nano scale. Despite these creative reports in the field of smart polymers, the need to create new polymer lattices has always existed owing to the broad plethora of industrial applications involved. [Extracted from the article]

It is very challenging to prepare stable radicals as they are usually thermodynamically or kinetically unstable in air. Herein, a series of star‐shaped aromatic nitric acid radicals were prepared via facile demethylation and consequent oxidation. As phenol radicals without steric hindrance group protection, they exhibit high electrochemical and thermal stability due to their rich resonance structures including closed‐shell nitro‐like and open‐shell nitroxide structure with unpaired electrons delocalized in conjugated backbones. Among them, TPA‐TPA‐O6 powder exhibited extremely wide absorption from 300 to 2000 nm covering the whole solar spectral irradiance, high photothermal conversion efficiency, and negligible photobleaching effect in seawater desalination. Under the irradiation of one sunlight, the water evaporation efficiency of TPA‐TPA‐O6 is recorded to be as high as 89.41 % and the water evaporation rate is 1.293 kg m−2 h−1, which represents the top performance in pure organic small molecule photothermal materials. [ABSTRACT FROM AUTHOR]

Practical synthesis of polyolefin–polyvinyl block copolymers remains a challenge for transition‐metal catalyzed polymerizations. Common approaches functionalize polyolefins for post‐radical polymerization via insertion methods, yet sacrifice the livingness of the olefin polymerization. This work identifies an orthogonal radical/spin coupling technique which affords tandem living insertion and controlled radical polymerization. The broad tolerance of this coupling technique has been demonstrated for diverse radical/spin traps such as 2,2,5‐trimethyl‐4‐phenyl‐3‐azahexane‐3‐nitroxide (TIPNO), 1‐oxyl‐(2,2,6,6‐tetramethylpiperidine) ‐4‐yl‐α‐bromoisobutyrate (TEMPO‐Br), and N‐tert‐butyl‐α‐phenylnitrone (PBN). Subsequent controlled radical polymerization is demonstrated with nitroxide‐mediated polymerization (NMP) and atom transfer radical polymerization (ATRP), yielding polyolefin–polyvinyl di‐ and triblock copolymers (Đ<1.3) with acrylic, vinylic and styrenic segments. These findings highlight radical trapping as an approach to expand the scope of polyolefin‐functionalization techniques to access polyolefin macroinitiators. [ABSTRACT FROM AUTHOR]

Overproduction of reactive oxygen species (ROS) during oxidative stress is hallmark of acute kidney injury (AKI), which induced the damage to the renal cells and mitochondrial injury. In this contribution, we prepared mitochondrial targeted nitroxide, which linked 3-carboxy-2,2,5,5-tetramethylpyrrolidine 1-oxyl (carboxy-PROXYL) with (2-aminoethyl)triphenylphosphonium bromide (TPP), named TPP-PROXYL to eliminate the ROS in situ and image the oxidative stress reaction by MRI. 2,7-Dichlorodi-hydrofluorescein diacetate (DCFH-DA) staining, mitochondrial membrane potential assay (JC-1) staining and transmission electron microscope (TEM) experiments were processed to verify that TPP-PROXYL could target mitochondria, scavenge the ROS, and prevent damage to mitochondria in live cells. Contrast enhanced MRI also been used to monitor these redox reaction in AKI model. TPP-PROXYL demonstrated excellent ROS T1-weighted magnetic resonance imaging enhancement in vitro and in vivo, with r1 value about 0.190 mM−1 s−1. In vivo AKI treatment experiments proved that TPP-PROXYL could improve the survival rate of mice and inhibit kidney damage. Moreover, the great ROS scavenging capability and the renal damage reduction during AKI treatment of TPP-PROXYL was verified via MR imaging technology. Collectively, this research provides TPP-PROXYL would serve as a powerful platform to realize ROS scavenging, treatment, and MR imaging of AKI. [ABSTRACT FROM AUTHOR]

A series of new pyridyl‐ or 2‐pyridyloxide‐containing donor‐acceptor diarylnitroxides was obtained and characterized; high stability of the ortho‐2‐pyridyl‐containing diarylnitroxides was determined by kinetic measurements (τ1/2=1733 h in benzene). Comparative voltammetric study of new nitroxides and their analog in which the Py replaces the Ph group revealed both through‐bond and through‐space stabilization of the NO redox states with the pyridyl/ 2‐pyridyloxide moiety, providing reversibility of both oxidation and reduction processes. Adaptive conformational behavior of new pyridyl/pyridyloxide containing nitroxides upon one‐electron oxidation and reduction was confirmed by DFT calculations. Stimuli‐responsive conformational changes allow switching on/off dispersion and electrostatic interactions within the molecule and increase stability of the redox states. Spectroelectrochemical measurements provided experimental evidence for reversibility of the through‐space stabilization of the oxidized state of the nitroxides with the neighboring pyridine lone pair. [ABSTRACT FROM AUTHOR]

With a view to fabricating a new remote input‐output system by applying functional ionic liquid crystalline (ILC) materials, we have developed novel ILC compounds containing a nitroxide radical unit in the organic cations, which show an enantiotropic smectic A (SmA) phase. We have implemented the magnetic manipulation of a droplet of one of the ILC compounds on the basis of the intermolecular magnetic interactions between radical moieties. This ILC monoradical compound shows a 55 % larger increase in paramagnetic susceptibility at the solid‐to‐LC melting point in the first heating process than the non‐ionic LC monoradical compounds. It is most likely owing to the nanosegregation of strongly bonded ionic and non‐ionic moieties. The increased molar magnetic susceptibility is preserved not only in the SmA phase but also in the isotropic liquid and solid phases during the first cooling process. [ABSTRACT FROM AUTHOR]

The structures of Ni(II), Cu(II), and Zn(II) complexes with anions of 2,5-pyrrolyl-disubstituted nitronyl nitroxide (L1) and iminonitroxide (L2) diradicals (HL1 is 2,2′-(1H-pyrrole-2,5diyl)-bis(4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl; HL2 is 2,2′-(1H-pyrrole-2,5-diyl)-bis(4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl) are studied. It is established that in all synthesized compounds, a tridentate meridional coordination of paramagnetic ligands is responsible for a distorted octahedral environment of the metal ion. In bis-chelates, the metal ion environment is an octahedron compressed along the NPyr–M–MPyr axis. When one of the ligands in the molecule is replaced by a reduced L2H monoradical, a typical Cu(II) environment in the form of elongated octahedron arises in [CuL2L2H]. It is found that in complexes with bis-nitronyl nitroxide, the character of the temperature dependence of the effective magnetic moment μeff(T) is determined by antiferromagnetic exchange in coordinated diradicals. In complexes with iminonitroxides, ferromagnetic exchange interactions between unpaired electrons of the metal ion and diradicals dominate. [ABSTRACT FROM AUTHOR]

Microbial biofilms are becoming increasingly difficult to treat in the medical setting due to their intrinsic resistance to antibiotics. To combat this, several biofilm dispersal agents are currently being developed as treatments for biofilm infections. Combining biofilm dispersal agents with antibiotics is emerging as a promising strategy to simultaneously disperse and eradicate biofilms or, in some cases, even inhibit biofilm formation. Here we review studies that have investigated the anti-biofilm activity of some well-studied biofilm dispersal agents (e.g., quorum sensing inhibitors, nitric oxide/nitroxides, antimicrobial peptides/amino acids) in combination with antibiotics from various classes. This review aims to directly compare the efficacy of different combination strategies against microbial biofilms and highlight synergistic treatments that warrant further investigation. By comparing across studies that use different measures of efficacy, we can conclude that treating biofilms in vitro and, in some limited cases in vivo , with a combination of an anti-biofilm agent and an antibiotic, appears overall more effective than treating with either compound alone. The review identifies the most promising combination therapies currently under development as biofilm inhibition and eradication therapies. [ABSTRACT FROM AUTHOR]

This paper describes the stepwise aza‐Wittig reaction of 1,1′‐bis(triphenylphosphoranylidenamino)‐ferrocene with a paramagnetic isocyanate, namely, 3‐isocyanato‐2,2,5,5‐tetramethyl‐2,5‐dihydro‐1H‐pyrrole‐1‐oxyl, and then with substituted arylisocyanates. The intermediate product (a paramagnetic betaine), which is the product of an intramolecular nucleophilic attack of the nitrogen atom of the iminophosphorane moiety on the carbon atom of the carbodiimide functional group, was isolated and structurally characterized. Subsequent interaction of the betaine with arylisocyanates under mild conditions gave spin‐labeled ferrocenophanes with the 1,3‐diazetidine‐2,4‐diimine coupler. It was found that the mutual arrangement of the substituents in the latter depends on the nature of the substituents in the arylisocyanate. Iodophenyl derivatives of 1,3‐diazetidine‐2,4‐diimines were cross‐coupled with the gold(I) nitronyl nitroxide‐2‐ide complex, thus yielding diradicals: metallocenophanes functionalized with various types of nitroxide substituents. Molecular and crystal structures of all mono‐ and diradicals were solved by X‐ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Electroactive coatings based on non-conjugated redox-active polymers have increased in popularity with the development of thin film organic batteries. Control over coating deposition, redox-activity, and ion transport are key to improving their energy storage performance. In this work, the synthesis, solution state electrochemical characterization, and layer-by-layer (LbL) assembly of a nitroxide-based polycation and polyanion are presented. Solution state electrochemical characterization indicates that the rate of electron transfer for the nitroxide polyanion is much higher as compared to the nitroxide polycation. LbL thin films of the nitroxide polyanion and nitroxide polycation are assembled, demonstrating linear growth and tunable thickness (28 nm/layer pair). This work confirms that the ion transport mechanism of the LbL films during the redox reaction is influenced depending on the charge of the terminating layer, where the nitroxide polyanion can participate in self-doping, which leads to a contribution from cation transport. The nitroxide polyanion-terminated film also exhibits a higher capacity and a slightly reduced charge transfer resistance. However, it was also observed that a more pronounced capacity fade occurred for the polyanion-terminated film than the polycationterminated film. Taken together, this highlights how oppositely charged radical-containing polyelectrolytes can form electroactive coatings for possible applications in energy storage or sensing. [ABSTRACT FROM AUTHOR]

A methodology for the oxidative amidation of aldehydes to yield N‐acyl azoles is reported. The approach employs sodium persulfate and a catalytic amount of a nitroxide and is applicable to a range of structurally diverse substrates. [ABSTRACT FROM AUTHOR]

The insufficiency of clean water sources has become a perilous tension for the future of the world that one of the eco-friendly and cost-effective solutions is the photocatalytic process for removal of artificial dyes and poisonous organic impurities. In the current research, an eco-friendly sonochemistry process was accomplished to gain Gd 2 Sn 2 O 7 (GSO) nanoparticles with progressive photo-catalytic proficiency. Lysine amino acid as a green capping agent and ethylenediamine (en) as an alkaline agent were utilized with effective surface categories aiming to manage the growth of formed nuclei with the design of spatial barriers around the metal cations and lastly, stop nano-sample accumulation. The figure and dimension of products was studied by various characterization procedures of spectroscopic and microscopic. The photo-degradation performances of the pure Gd 2 Sn 2 O 7 , Gd 2 Sn 2 O 7 /SnO 2 and Gd 2 Sn 2 O 7 /SnO 2 /Gd 2 O 3 nanocomposites were tested to the removal of diverse synthetic dyes. The outcome of the type of dye, nano-catalyst composition, pH and scavenger kind was labeled on modifying ability of Gd-Sn-O nano-catalyst task. Optimized Gd 2 Sn 2 O 7 /SnO 2 /Gd 2 O 3 nanocomposites have an efficiency of 98% for degradation of erythrosine dye that •OH radicals support photo-degradation of contamination. • Synthesis of Gd 2 Sn 2 O 7 nanoparticles via rapid and green ultrasonic technique. • Investigation of diverse synthesis circumstances on dimension properties of nanostructures. • Consideration of photo-degradation efficiency of Gd-Sn-O nanostructures in different experimental conditions. • Investigation of photocatalytic mechanism of Gd 2 Sn 2 O 7 /Gd 2 O 3 /SnO 2 nanocomposites and kinetic study. [ABSTRACT FROM AUTHOR]

The oxidative damage of DNA is associated with aging and the development of various diseases. Although nucleoside-derived radicals play an important role in DNA oxidation, their analysis methods are limited. Herein, we propose a fluorometric detection and structural analysis of radicals on the surface of oxidatively damaged DNA using a profluorescent nitroxide probe combined with liquid chromatography–fluorometry and high-resolution tandem mass spectrometry. [ABSTRACT FROM AUTHOR]

The nitroxide, Tempol, prevents obesity related changes in mice fed a high fat diet (HFD). The purpose of this study was to gain insight into the mechanisms that result in such changes by Tempol in female C3H mice. Microarray methodology, Western blotting, bile acid analyses, and gut microbiome sequencing were used to identify multiple genes, proteins, bile acids, and bacteria that are regulated by Tempol in female C3H mice on HFD. The effects of antibiotics in combination with Tempol on the gut microflora were also studied. Adipose tissue, from Tempol treated mice, was analyzed using targeted gene microarrays revealing up-regulation of fatty acid metabolism genes (Acadm and Acadl > 4-fold, and Acsm3 and Acsm5 > 10-fold). Gene microarray studies of liver tissue from mice switched from HFD to Tempol HFD showed down-regulation of fatty acid synthesis genes and up-regulation of fatty acid oxidation genes. Analyses of proteins involved in obesity revealed that the expression of aldehyde dehydrogenase 1A1 (ALDH1A1) and fasting induced adipose factor/angiopoietin-like protein 4 (FIAF/ANGPTL4) was altered by Tempol HFD. Bile acid studies revealed increases in cholic acid (CA) and deoxycholic acid (DCA) in both the liver and serum of Tempol treated mice. Tempol HFD effect on the gut microbiome composition showed an increase in the population of Akkermansia muciniphila , a bacterial species known to be associated with a lean, anti-inflammatory phenotype. Antibiotic treatment significantly reduced the total level of bacterial numbers, however, Tempol was still effective in reducing the HFD weight gain. Even after antibiotic treatment Tempol still positively influenced several bacterial species such as as Akkermansia muciniphila and Bilophila wadsworthia. The positive effects of Tempol moderating weight gain in female mice fed a HFD involves changes to the gut microbiome, bile acids composition, and finally to changes in genes and proteins involved in fatty acid metabolism and storage. [Display omitted] • Tempol remodels the gut microbiome in female mice fed a high fat diet. • Bile acid profiles in liver and serum were modulated by Tempol. • Tempol regulates fatty acid synthesis and metabolism genes. • The obesity related protein ALDH1A1 was downregulated. • Adipokine FIAF was upregulated by Tempol. [ABSTRACT FROM AUTHOR]

Two Cd–Ln coordination polymers (CPs), with the open-chain ether Schiff base bis(5-bromine-3-methoxysalicylidene)-3-oxapentane-1,5-diamine (H2L), {[CdLnL(OAc)(NO3)(CH3OH)(isonicotinate)]·(3CH2Cl2)}n (Ln = Gd (1) and Er (2)), have been synthesized by the interfacial diffusion method. The structure analysis reveals that both CPs 1 and 2 are infinite one-dimensional zigzag coordination polymers, which are formed by isonicotinate bridging CdLnL cluster units. The fluorescence properties of H2L, 1 and 2 in the solid-state were studied. Compared with the free H2L, the fluorescence peaks of the two Cd–Ln CPs have undergone a significant blue shift (about 80 nm) and enhancement. This is due to the increased rigidity of the ligand after coordination of the metal ions with the ligand, which reduces the energy loss of thermal vibration. The fluorescence enhancement of 1 is greater than that of 2, which may be caused by the lanthanide contraction. Moreover, the results of experiments in vitro indicate that H2L, 1 and 2 have good ability to scavenge superoxide radical and that 1 and 2 are higher than free H2L, where their IC50 value is in the range 12.5–21.4 μM. [ABSTRACT FROM AUTHOR]

Nitroxide radicals are characterized by a long‐lived spin‐unpaired electronic ground state and are strongly sensitive to their chemical surroundings. Combined with electron paramagnetic resonance spectroscopy, these electronic features have led to the widespread application of nitroxide derivatives as spin labels for use in studying protein structure and dynamics. Site‐directed spin labelling requires the incorporation of nitroxides into the protein structure, leading to a new protein–ligand molecular model. However, in protein crystallographic refinement nitroxides are highly unusual molecules with an atypical chemical composition. Because macromolecular crystallography is almost entirely agnostic to chemical radicals, their structural information is generally less accurate or even erroneous. In this work, proteins that contain an example of a radical compound (Chemical Component Dictionary ID MTN) from the nitroxide family were re‐refined by defining its ideal structural parameters based on quantum‐chemical calculations. The refinement results show that this procedure improves the MTN ligand geometries, while at the same time retaining higher agreement with experimental data. [ABSTRACT FROM AUTHOR]

The Kabachnik-Fields reaction is a multicomponent reaction that provides α-aminophosphonates and phosphorus analogs of α-amino acids. While paramagnetic α-amino acids are well known, to the best of our knowledge, this is the first report on paramagnetic α-aminophosphonate syntheses. We present examples of nitroxide-containing α-aminophosphonates starting from five- and six-membered paramagnetic aldehydes, a paramagnetic ketone, and five- and six-membered paramagnetic amines. Starting from a β-bromo-α,β unsaturated aldehyde, we constructed a pyrroline-nitroxide-condensed heterocycle with a phosphonate ester substituent. [ABSTRACT FROM AUTHOR]

The structures of hexafluoroacetylacetonate complexes of Cu(II)–Cu(hfac)2– with nitroxide radicals LR1/R2, where R1 and R2 are alkyl substituents in the 1,3-pyrazole moiety are studied by X-ray crystallography. It is found that solid phases of all [Cu(hfac)2LR1/R2] are formed by polymeric chains whose common structural motif is a ditopic bridging coordination of paramagnetic ligands in the head-to-head fashion. The study of the temperature structure dynamics and the related change in the temperature dependence of the effective magnetic moment of the complex shows that changes in both R1 and R2 can substantially affect not only the possibility of the appearance of magnetic anomalies on the temperature curve of the effective magnetic moment but also its shape. [ABSTRACT FROM AUTHOR]

Ligand reorganization has been shown to have a profound effect on the outcome of cerium redox chemistry. Through the use of a tethered, tripodal, trianionic nitroxide ligand, [((2-tBuNOH)C6 H4 CH2 )3 N](3-) (TriNOx (3-) ), controlled redox chemistry at cerium was accomplished, and typically reactive complexes of tetravalent cerium were isolated. These included rare cationic complexes [Ce(TriNOx )thf][BAr(F) 4 ], in which Ar(F) =3,5-(CF3 )2 -C6 H3 , and [Ce(TriNOx )py][OTf]. A rare complete Ce-halide series, Ce(TriNOx )X, in which X=F(-) , Cl(-) , Br(-) , I(-) , was also synthesized. The solution chemistry of these complexes was explored through detailed solution-phase electrochemistry and (1) H NMR experiments and showed a unique shift in the ratio of species with inner- and outer-sphere anions with size of the anionic X(-) group. DFT calculations on the series of calculations corroborated the experimental findings.

We present results of a pulsed dynamic nuclear polarization (DNP) study at 0.35 T (9.7 GHz/ 14.7 MHz for electron/¹H Larmor frequency) using a lab frame-rotating frame cross polarization experiment that employs electron spin locking fields that match the ¹H nuclear Larmor frequency, the so called NOVEL (nuclear orientation via electron spin locking) condition. We apply the method to a series of DNP samples including a single crystal of diphenyl nitroxide (DPNO) doped benzophenone (BzP), 1,3-bisdiphenylene-2-phenylallyl (BDPA) doped polystyrene (PS), and sulfonated-BDPA (SA-BDPA) doped glycerol/water glassy matrices. The optimal Hartman-Hahn matching condition is achieved when the nutation frequency of the electron matches the Larmor frequency of the proton, ω1S = ω0I, together with possible higher order matching conditions at lower efficiencies. The magnetization transfer from electron to protons occurs on the time scale of ~100 ns, consistent with the electron-proton couplings on the order of 1-10 MHz in these samples. In a fully protonated single crystal DPNO/BzP, at 270 K, we obtained a maximum signal enhancement of e = 165 and the corresponding gain in sensitivity of e(T1/TB)1/2 = 230 due to the reduction in the buildup time under DNP. In a sample of partially deuterated PS doped with BDPA, we obtained an enhancement of 323 which is a factor of ~3.2 higher compared to the protonated version of the same sample and accounts for 49% of the theoretical limit. For the SA-BDPA doped glycerol/water glassy matrix at 80 K, the sample condition used in most applications of DNP in nuclear magnetic resonance, we also observed a significant enhancement. Our findings demonstrate that pulsed DNP via the NOVEL sequence is highly efficient and can potentially surpass continuous wave DNP mechanisms such as the solid effect and cross effect which scale unfavorably with increasing magnetic field. Furthermore, pulsed DNP is also a promising avenue for DNP at high temperature. [ABSTRACT FROM AUTHOR]

1,1,3,3‐Tetramethylisoindolin‐2‐yloxyl (TMIO) is a well‐known stable 2,3‐dihydroisoindoline aminoxyl radical, which is thermally generated (at >100 °C) from literature alkoxyamine derivatives. Herein is the synthesis of visible light activated benzimidazolequinone alkoxyamines of TMIO using oxidative methods and the first room temperature nitroxide‐exchange experiments with 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) analogues. For the alkoxyamine TMIO‐Vis dissociation rate constants are provided using TEMPO and oxygen as radical traps. [ABSTRACT FROM AUTHOR]

Asthma is characterized by airway inflammation, hyper-responsiveness, symptoms of dyspnea, wheezing and coughing. In most patients, asthma is well controlled using inhaled corticosteroids and bronchodilators. A minority of patients with asthma develop severe disease, which is frequently only partially responsive or even resistant to treatment with corticosteroids. Severe refractory asthma is associated with structural changes in the airways, termed "airway remodeling", and/or with neutrophilic rather than eosinophilic airway inflammation. While oxidative stress plays an important role in the pathophysiology of asthma, cyclic nitroxide stable radicals, which are unique and efficient catalytic antioxidants, effectively protect against oxidative injury. We have demonstrated that the nitroxide 3-carbamoyl proxyl (3-CP) attenuates airway inflammation and hyperresponsiveness in allergic asthma as well as bleomycin-induced fibrosis both using murine models, most probably through modulation of oxidative stress. The present study evaluates the effect of 3-CP on airway inflammation and remodeling using two murine models of severe asthma where mice are sensitized and challenged either by ovalbumin (OVA) or by house dust mite (HDM). 3-CP was orally administered during the entire period of the experiment or during the challenge period alone where its effect was compared to that of dexamethasone. The induced increase by OVA and by HDM of BALf cell counts, airway hyperresponsiveness, fibrosis, transforming growth factor-beta (TGF-β) levels in BALf and protein nitration levels of the lung tissue was significantly reduced by 3-CP. The effect of 3-CP, using two different murine models of severe asthma, is associated at least partially with attenuation of oxidative stress and with TGF-β expression in the lungs. The results of this study suggest a potential use of 3-CP as a novel therapeutic agent in different forms of severe asthma. [Display omitted] • Severe asthma is related to airway remodeling and/or neutrophilic airway inflammation. • Nitroxides, such as 3-carbamoyl-proxyl (3-CP), are powerful catalytic antioxidants. • 3-CP was delivered orally to mice using two models of severe asthma. • 3-CP reduces airway inflammation, airway remodeling, AHR, TGF-β and protein nitration levels. • The protective effect of 3-CP is associated at least partially with attenuation of oxidative injury. [ABSTRACT FROM AUTHOR]

A heteroatomic analog of 1,1,2,3,3-pentamethylenepropane, the diradical N-[bis(4,4,5,5-tetramethyl-3-oxide-1-oxyl-4,5-dihydro-1H-imidazol-2-yl)methylene]-2-methylpropane-2-amine oxide (1) with two C(sp2)-bonded nitronyl nitroxide fragments in magnetically concentrated (single crystal) and magnetically diluted (frozen solution) forms was studied by EPR spectroscopy. The longitudinal and transverse relaxation times of diradical 1 in the frozen solution were measured for the first time; a significant difference in the intramolecular exchange interaction was demonstrated for the cases of the single crystal and the frozen solution. The influence of solvation on the value of the intramolecular exchange interaction in this class of compounds was discussed. [ABSTRACT FROM AUTHOR]

Solution state Overhauser-effect-type dynamic nuclear polarization (ODNP) has been studied in the last years. The basis of ODNP is a polarization mechanism that presents nuclei with electron spin polarization. ODNP enhancements studies are presented 4-fluorobenzyl alcohol (4FBA) with the stable nitroxide radical as the polarizing agent for 15, 30 and 60 mM concentrations at 1.53 mT. Major ODNP parameters were obtained. The significant parameter is the coupling parameter, since it determines the maximum NMR signal enhancements and the interactions between the nuclear spin and the electron spin. The coupling parameter can vary from -0.152 to 0.001. The obtained ODNP parameters show that both scalar and dipolar interactions occur. The results show that nitroxide radical can be taken as polarizing agent for ODNP studies of 4-fluorobenzyl alcohol solvent. The effect of dissolved molecular oxygen on the enhancement factor for the sample with the smallest concentration was experimentally investigated. [ABSTRACT FROM AUTHOR]

A one-step convergent method was proposed for the synthesis of branched macromolecules in the presence of conjugated dinitrones (N,N-dimethylglyoxal dinitrone, N,N-di-tert-butylglyoxal dinitrone, and N,N- diphenylglyoxal dinitrone) under radical initiation. It was found that branched polystyrene macromolecules synthesized with participation of α-dinitrones have lower glass transition temperatures than their linear analogues. Modification methods for the prepared polymers containing alkoxyamine moieties with the goal to increase their thermal stability were developed. [ABSTRACT FROM AUTHOR]

A 12-nuclear heterospin complex of Cu(II) hexafluoroacetylacetonate with dialkylpyrazolyl-substituted nitroxide [Cu2(hfac)4LBu/Et]6 is found, which has a previously unknown molecular structure for heterospin compounds where six {Cu(hfac)2(LBu/Et)} moieties form a 42-membered metallacycle. The ditopic function of connecting organic bridges between Cu atoms is performed by paramagnetic LBu/Et ligands forming a head-to-tail motif inside the metallacycle due to the coordination of the nitrogen atoms of the pyrazole ring (NPz) and one of the oxygen atoms (ONO) of the nitronyl nitroxide moiety. Each LBu/Et completes its structural function to tritopic due to the coordination of the second ONO atom by yet another Cu(hfac)2 moiety. Butyl substituents of the pyrazole moiety tightly fill the space inside the metallacycle, preventing the inclusion of any solvent molecules. Ethyl substituents of the pyrazole rings, methyl groups of the imidazoline moiety, and trifluoromethyl groups of hexafluoroacetylacetonate anions directed into the intermolecular space push the metallacycles apart. As a result, the neighboring metallacycles are magnetically isolated from each other, and the character of the temperature dependence of the effective magnetic moment is determined by strong antiferromagnetic interactions between nitroxides and terminal Cu(hfac)2 moieties inside 12-nuclear molecules. Because of these interactions, below 160 K only spins of intracyclic Cu(II) ions, weakly interacting with each other, contribute to the magnetic susceptibility. [ABSTRACT FROM AUTHOR]

As a highly efficient nitroxide radical catalyst for selective catalytic oxidation of cellulose, N-hydroxyphthalimide (NHPI) has attracted much attention because of its low price and light cellulose degradation. However, NHPI is insoluble in water and is difficult to recycle because of its small molar mass. To address the above issues, the water-soluble polyethylene glycol (PEG)-immobilized NHPI catalyst (PEG-NHPI) was designed and prepared in this work. Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), size exclusion chromatography (SEC) and UV–Vis light spectrophotometry were used to characterize PEG-NHPI. The results showed that PEG-NHPI catalysts with good water solubility and adjustable NHPI loading amounts were successfully synthesized. Using NaBr as promoter and NaClO as oxidant, PEG-NHPI mediated oxidation of cellulose was carried out and good catalytic performance was found. The catalytic performance of PEG-NHPI mediated oxidation of cellulose in water was higher than that in acetonitrile–water. The carboxyl content of PEG-NHPI oxidized cellulose could reach the level of free NHPI oxidized cellulose, and was equivalent to 68% of 2, 2, 6, 6-tetramethylpiperidine-N-oxyl (TEMPO) oxidized cellulose, while the degradation degree of cellulose was greatly reduced by more than 40%. The catalytic performance did not decrease significantly after six oxidation cycles. The structure of recycled PEG-NHPI was not changed. These results indicated that immobilizing NHPI onto PEG can achieve the unification of high catalytic performance and good recyclability. [ABSTRACT FROM AUTHOR]

We report here the syntheses of a diamagnetic Fe complex [Fe(HL)2] (1), prepared by reacting a redox non-innocent ligand precursor N,N′-bis(3,5-di-tert-butyl-2-hydroxy-phenyl)-1,2-phenylenediamine (H4L) with FeCl3, and its phenoxazine derivative [Fe(L′)2] (2), which was obtained via intra-ligand cyclisation of the parent complex. Magnetic measurements, accompanied by spectroscopic, structural and computational analyses show that 1 can be viewed as a rather unusual Fe(III) complex with a diamagnetic ground state in the studied temperature range due to a strong antiferromagnetic coupling between the low-spin Fe(III) ion and a radical ligand. For a paramagnetic high-spin Fe(II) complex 2 it was found that, when crystalline, it undergoes a thermally induced process where 25% of the molecules in the material change to a diamagnetic low-spin ground state below 100 K. Single crystal X-ray studies conducted at 95 K afforded detailed structural evidence for this partial change of spin state of 2 showing the existence of crystallographically distinct molecules in a 3 : 1 ratio which exist in high- and low-spin states, respectively. Also, the magnetic behaviour of 2 was found to be related with the crystallinity of the material as demonstrated by near-IR radiation to unpaired electrons conversion ability of amorphous sample of 2. [ABSTRACT FROM AUTHOR]

It has been observed that acrylate monomers are very difficult to polymerize with the low cost nitroxide catalyst 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO). Therefore, costly acyclic nitroxides such as N-tert-butyl-N-(1-diethylphosphono-2,2-dimethyl)-N-oxyl, (SG1), 2,2,5-Trimethyl-4-phenyl-3-azahexane-3-nitroxide (TIPNO) and TIPNO derivatives have to be used for the polymerization of the acrylic acid derivatives. There are very few reports on the use of TEMPO-derivatives toward the polymerization of n- butyl acrylate. Generally different reducing agents viz. glucose, ascorbic acid, hydroxyacetone etc. have been used to destroy excess TEMPO during the polymerization reaction. The acrylate polymerizations fail in the presence of TEMPO due to the strong C–O bond formed between the acrylate chain end and nitroxide. To the best of our knowledge, no literature report is available on the use of TEMPO without reducing agent or high temperature initiators, toward the polymerization of n- butyl acrylate. The present study has been carried out with a view to re-examine the application of low cost nitroxide TEMPO, so that it can be utilized towards the polymerization of acrylate monomers (e.g. n- butyl acrylate). We have been able to polymerize n- butyl acrylate using the nitroxide TEMPO as initiator (via a macroinitiator). In this synthesis, a polystyrene macroinitiator was synthesized in the first step from TEMPO, after this TEMPO end-capped styrene macroinitiator (PSt-TEMPO) is used to polymerize n- butyl acrylate monomer. The amount of macroinitiator taken was varied from 0.05% to 50% by weight of n- butyl acrylate monomer. The polymerization was carried out at 120°C by bulk polymerization method. The experimental findings showed a gradual increase in molecular weight of the polymer formed and decrease in the polydispersity index (PDI) with increase in amount of PSt-TEMPO macroinitiator taken. In all experiments conversion was more than 80%. These results indicate that the polymerization takes place through controlled polymerization process. Effect of different solvents on polymerization has also been investigated. In the following experiments TEMPO capped styrene has been used as macroinitiator leading to the successful synthesis of poly n- Butyl acrylate. It has been found that styrene macroinitiator is highly efficient for the nitroxide mediated polymerization, even in very small concentration for the synthesis of poly n- butyl acrylate. High concentration of macroinitiator results in the formation of block copolymers of polystyrene and poly (n -butyl acrylate) viz. polystyrene-block-poly-(n -butyl acrylate). The use of TEMPO toward controlled polymerization is of much importance, because it is the nitroxide commercially available at the lowest cost. [ABSTRACT FROM AUTHOR]

A series of branched high-molecular-weight alkoxyamines (HAAs) based on polystyrene of different molecular weight were synthesized using nitroxide radicals generated in situ in the presence of conjugated dinitrones (N,N-dimethylglyoxaldinitrone, N,N-di-tert-butylgly-oxaldinitrone, and N,N-diphenylglyoxaldinitrone). Structural features of the products obtained were studied by MALDI-TOF mass spectrometry. Modification of the synthesized HAAs in the presence of azobisisobutyronitrile, carbon tetrabromide, dodecyl mercaptane, 4,5,5-trimethyl-2,2-diethyl-2,5-dihydroimidazole-1-oxyl, and 3,5-di-tert-butylbenzoquinone, as well as thermolysis of the HAAs in the presence of atmospheric oxygen showed that the nitroxide fragments are located within the polymer chain irrespective of the initial structure of the conjugated dinitrone. The molecular weight characteristics and conformational properties of the nitroxide-containing linear macromolecules and polymers were studied by static and dynamic light scattering and by viscometry. In most cases, the calculated values of the ρ-parameter (Rg/Rh) and the Zimm viscosity factor of the branched polystyrene samples synthesized using conjugated dinitrones are lower than those of linear analogues. [ABSTRACT FROM AUTHOR]

Nitroxide compounds have been used as redox-sensitive imaging probes by electron paramagnetic resonance (EPR) for assessing oxidative stress in vivo. Fast redox reactions of nitroxide radicals are favorable for assessment of higher redox sensitivity; however, a variety of nitroxides have not been trialed for use as imaging probes due to their very rapid in vivo reduction, which cannot be captured at the slow operation speed of existing EPR imagers. To overcome this limitation, we improved our EPR system to provide a stable and highly sensitive imaging operation. We challenged the improved EPR imager to perform three-dimensional (3D) EPR imaging of mouse brain using two useful nitroxide imaging probes, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (Tempol) and 2,6-dispiro-4′,4ʺ-dipyrane-piperidine-4-one-N-oxyl (DiPy). The second-order rate constant of DiPy with ascorbic acid is 10 times larger than that of Tempol. The improved EPR imager obtained clear 3D EPR images of mouse brain and demonstrated that Tempol could exist with an unpaired electron. The imager also successfully obtained 3D EPR images of mouse head after administration of DiPy. As 126 projections can be acquired in a period of 6 s, 3D EPR imaging can visualize the sequential process of DiPy entering the brain, being distributed within the brain, and being reduced within the brain. These improvements to the EPR imager will enable useful nitroxide imaging probes that were previously unsuitable as imaging probes due to their rapid reduction to be considered for use for sensitive redox assessment in an in vivo system. [ABSTRACT FROM AUTHOR]

• Four new mono-nuclear Ln-radical complexes have been successfully prepared. • Tb complex displays field-induced slow relaxation of the magnetization. • Tb complex acted as luminescence-based probe for detecting Fe3+ and Cr2O72− ions. A series of mono-nuclear rare earth-radical compounds [Ln(hfac) 3 (NIT-Ph-3-COOMe) 2 ]·0.5C 7 H 16 (LnIII = Gd(1) , Tb(2) , Dy(3), Ho (4)) were get by reaction of nitroxide radical NIT-Ph-3-COOMe with Ln(hfac) 3 ·2H 2 O (NIT-Ph-3-COOMe=2-(3-(methoxycarbonyl)-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide; hfac=hexafluoroacetylacetonate). Each Ln(Ⅲ) ion in four complexes is an octa-coordination configuration, in which two O atoms from NO units of two NIT-Ph-3-COOMe radicals and six O atoms are derived from three hfac co-ligands. Magnetic measurements indicate that a ferromagnetic interaction between GdIII and nitroxide radicals, while magnetic coupling of two NOs transmitted by GdIII ion is antiferromagnetic. For compound 2 , non-zero out-of-phase signals (χ″) were gained at 3000 Oe, confirming field-induced magnetic relaxation behavior. Furthermore, fluorescence properties of 2 were investigated, which indicated that it can be used as a highly sensitive and selective fluorescence probe of Fe3+ cation and Cr 2 O 7 2− anion. Four new mono-nuclear Ln-radical complexes have been successfully prepared. The Gd–nitroxide exchange is ferromagnetic while the magnetic coupling between two nitroxide radicals is antiferromagnetic. Tb complex displays field-induced slow relaxation of the magnetization. Moreover, it can be acted as luminescence-based probe for quantitative and highly sensitive detection of Fe3+and Cr 2 O 7 2− ions. [Display omitted] [ABSTRACT FROM AUTHOR]

• Modification of DSSC architecture by incorporating microscopic reference electrodes. • Separation of contributions of photoanode and counter electrode to EIS. • Identification of recombination and mediator regeneration rates in DSSCs. • In-depth analysis of the rate-limiting steps of aqueous TEMPO-based electrolytes. For new components in dye-sensitized solar cells (DSSCs), identification and quantification of rate-limiting steps is needed to evaluate their applicability. This is particularly important if fundamental changes are studied. In this work, the use of a micro-reference electrode in DSSCs is proposed to increase the significance of electrochemical impedance spectroscopy. The recombination of charge carriers at the photoanode and the regeneration of redox mediators at the counter electrode, which typically occur on similar timescales, could be studied separately but simultaneously in cells under operating conditions. This is particularly useful in the study of water-based DSSCs. Here, cells with 2,2,6,6-Tetramethylpiperidinoxyl (TEMPO) or 4-Hydroxy-TEMPO (OH-TEMPO) as redox mediators using additives like 1-Methylbenzimidazole (MBI) are discussed. It was revealed that the charge transfer resistance (R CE) for the reduction of the oxidized redox mediator at the counter electrode (CE) limits the fill factor (FF) of such DSSCs. TEMPO/MBI electrolytes yielded low R CE and high FF , whereas OH-TEMPO in otherwise identical cells resulted in large R CE , low FF , and low conversion efficiencies. This indicates that the interface between the CE and the electrolyte significantly influences the DSSC performance of these cells and strongly depends on the electrolyte composition. Important optimization strategies could be discussed based on the present results. [Display omitted] [ABSTRACT FROM AUTHOR]

Ferrate (Fe(VI)) is a promising oxidant for water remediation, yet it has limited reactivity towards certain recalcitrant but important emerging contaminants, such as sulfamethoxazole. Here, this study demonstrates that nitroxide redox mediators, specifically 9-azabicyclo[3.3.1]nonasne N -oxyl (ABNO), can catalyze Fe(VI) reaction with sulfamethoxazole by functioning both as Fe(VI) activator and electron shuttle. The underlying mechanism is explained as: (i) Fe(VI) activation: a series of one-electron transfers between Fe(VI) and ABNO produces highly reactive Fe(V)/Fe(IV) and ABNO+; (ii) electron shuttle: the newly formed active ABNO+ reacts with the sulfamethoxazole, contributing to its removal. Concurrently, ABNOH is generated and subsequently converted back to ABNO by reactive species, thereby completing the redox cycle. The as-developed heterogeneous redox mediator, ABNO@SiO 2 , retained its catalytic properties and effectively catalyzed Fe(VI) to remove sulfamethoxazole at environmentally relevant pH levels. [Display omitted] • The nitroxide redox mediators served as Fe(VI) activators and electron shuttles. • Trace redox mediators increased reaction kinetics by 16.8-fold at pH 7.0 • Heterogenous mediator enabled 80% sulfamethoxazole removal by Fe(VI) within 90s. [ABSTRACT FROM AUTHOR]

This article, titled "Selective Transition Enhancement in a g-Engineered Diradical," discusses the synthesis of an asymmetric diradical by grafting a nitroxide radical onto the [Y(Pc)2]⋅ radical system. The molecule exhibits a weak exchange interaction between its two radical units, resulting in electron paramagnetic resonance transitions of different tipping angles. These transitions can be selectively enhanced by choosing the appropriate magnetic field and microwave power. The research article provides more detailed information on this topic. [Extracted from the article]

A series of new Tacrine analogs modified with nitroxides or pre-nitroxides on 9-amino group via methylene or piperazine spacers were synthesized; the nitroxide or its precursors were incorporated into the Tacrine scaffold. The new compounds were tested for their hydroxyl radical and peroxyl radical scavenging ability, acetylcholinesterase inhibitor activity and protection against Aβ-induced cytotoxicity. Based on these assays, we conclude that Tacrine analogs connected to five and six-membered nitroxides via piperazine spacers (9b, 9b/HCl and 12) exhibited the best activity, providing direction for further development of additional candidates with dual functionality (anti Alzheimer's and antioxidant).

Atom‐economy cyclopropyl group turned out to be the substituent of choice for stabilization of diphenylnitroxyl radical in solution (τ1/2=1280 h, i. e., ca. 2 months, in benzene). Though the benzylic H‐atom commonly provokes fast decomposition of nitroxides in solution and the cyclopropyl moiety is prone to the ring opening in substrates with significant spin density at the α‐position, both processes are not implemented in 4,4'‐dicyclopropyldiphenylnitroxide. Instead, the stereoelectronic properties of the cyclopropyl group lead to significant stabilization of the oxidized and reduced states of the nitroxide, making it redox‐amphoteric and suitable for practical application. [ABSTRACT FROM AUTHOR]

Herein, we report an EPR-based method for protease enzymatic characterization and inhibitor screening. This method utilizes dual paramagnetically-labeled probes consisting of a nitroxide spin probe and a Gd3+ ion flanking a peptide that could be specifically cleaved by protease caspase-3. Distance-dependent dipolar coupling between the two paramagnetic centers can be modulated by the protease cleavage activity, thus providing a straightforward and convenient method for protease activity detection using EPR spectroscopy under ambient conditions. Moreover, time-course monitoring of the protease-catalyzed cleavage reaction demonstrated that this EPR-based method could not only allow a direct quantitative enzymatic kinetic assessment, but also could be used for protease inhibitor screening, thus holding great potential in drug discovery studies. [ABSTRACT FROM AUTHOR]

Solution‐based syntheses are omnipresent in chemistry but are often associated with obvious disadvantages, and the search for new mild and green synthetic methods continues to be a hot topic. Here, comparative studies in four different reaction media were conducted, that is, the solid‐state mechano‐ and slow‐chemistry synthesis, melted phase, and solution protocols, and the impact of the employed solvent‐free solid‐state versus liquid‐phase synthetic approaches was highlighted on a pool of products. A moderately exothermic model reaction system was chosen based on bis(pentafluorophenyl)zinc, (C6F5)2Zn, and 2,2,6,6‐tetramethylpiperidinyl oxide (TEMPO) as a stable nitroxyl radical, anticipating that these reagents may offer a unique landscape for addressing kinetic and thermodynamic aspects of wet and solvent‐free solid‐state processes. In a toluene solution two distinct paramagnetic Lewis acid‐base adducts (C6F5)2Zn(η1‐TEMPO) (1) and (C6F5)2Zn(η1‐TEMPO)2 (2) equilibrated, but only 2 was affordable by crystallization. In turn, crystallization from the melt was the only method yielding single crystals of 1. Moreover, the solid‐state approaches were stoichiometry sensitive and allowed for the selective synthesis of both adducts by simple stoichiometric control over the substrates. Density functional theory (DFT) calculations were carried out to examine selected structural and thermodynamic features of the adducts 1 and 2. Compound 2 is a unique non‐redox active metal complex supported by two nitroxide radicals, and the magnetic studies revealed weak‐to‐moderate intramolecular antiferromagnetic interactions between the two coordinated TEMPO molecules. [ABSTRACT FROM AUTHOR]

Herein, the synthesis of a novel nitroxide‐mediated polymerization (NMP) initiator bearing a photolabile ortho‐nitrobenzyl (oNB) group allowing surface‐initiated NMP preparation of well‐defined photoresponsive polystyrene grafted on silica nanoparticles is described. The photocleavable and photoresponsive properties of the prepared materials are demonstrated using small angle X‐ray scattering (SAXS) characterization. [ABSTRACT FROM AUTHOR]