Hydroxyl Research Articles

Theoretical Studies on the Reaction Mechanism of Schiff Base Formation from Hexoses.

The Maillard reaction is one of the nonenzymatic post-translational modifications of proteins. Products of this reaction are considered to be related to aging diseases and the sensation of taste. In the initial stage of the Maillard reaction, Schiff base formation first occurs by the nucleophilic attack of amine nitrogen in proteins, and then, the reaction proceeds through the formation of 1,2-eminal and Amadori compounds. In this study, we computationally investigated the reaction pathway of Schiff base formation from hexoses. The optimized geometries of energy minima and transition states were calculated by using the density functional theory with the CAM-B3LYP/6-311+G(2d,2p) level of theory. The Schiff base formation progressed through three steps: two steps of carbinolamine formation and one step of dehydration. The dehydration is considered to be the rate-determining step in all hexoses because the activation barrier of the dehydration was higher than that of the carbinolamine formation. Furthermore, the steric configuration of the OH group at positions 2 and 3 affected the activation barrier.

Thymus vulgaris-assisted growth of nickel nanoparticles onto Luffa fibers: A robust and recyclable catalyst for the reduction of organic pollutants

A green and efficient synthetic pathway was developed to prepare nickel@Luffa nanocomposite. Thymus vulgaris extract was used to functionalize the surface of Luffa fibers with hydroxyl, carbonyl, and amide groups, which assisted in the adsorption of nickel ions. The scanning electron microscope images revealed that nickel nanoparticles grew as aggregates of semi-spherical particles and randomly dispersed on the Luffa fibers. The X-ray diffraction pattern of the nickel@Luffa nanocomposite showed the diffraction pattern of a face-centered cubic Ni crystal. XPS spectrum indicated the formation of metallic Ni at the Luffa surface. The prepared nickel@Luffa was used to catalyze the degradation of 4-nitrophenol, methyl orange, bromophenol blue and a mixture of both. The reaction rate constant for nickel@Luffa nanocomposite was calculated as 15.47 × 10−3 s−1 at pH = 10 and even after ten cycles its conversion was about 90%. The nickel nanoparticles could be recycled/reused for ten catalytic cycles with adequate catalytic activity. Such synthetic pathways encourage the application of renewable natural resources to fabricate separable/recyclable heterogeneous catalyst for many important reactions. The proposed nanocomposite is industrially applicable and environmentally-benign, fulfilling the requirements for the sustainable development.

Specific, nondestructive, and durable adhesion primer for polyolefins

AbstractGluing polyolefins [e.g., polyethylene (PE) and polypropylene (PP)] results in a very challenging task. The main reason relies on their low surface energy, which reduces the affinity between the polyolefin surface and the chosen adhesive. To tackle this problem, the most commonly used solutions are physical surface treatments, such as plasma, corona, and flame, which introduce hydrophilic moieties on the plastics surface, thus increasing their surface energy. These approaches require special setups, are unspecific, and can induce material degradation. Furthermore, they provide a transient solution, making the storage of pretreated substrates not recommended. In this work, we developed an easy-to-apply primer for durable bonding of adhesives on PE and PP, as robust alternative to physical treatments. Our primer contains a surface-anchoring moiety and an adhesive-binding group to covalently react with the polyolefin substrate and with the glue. As a surface-anchoring moiety, we chose the perfluorophenylazide (PFPA), which is known to undergo a C–H insertion reaction upon UV activation, while as adhesive-binding groups, we selected OH functions, which can covalently react with the most common commercially available glues. When these two features (i.e., PFPA and OH) are combined in a single molecule, the reaction with the substrate does not occur and the molecule is only physisorbed, inducing no adhesion improvement. Chemisorption only occurs with bicomponent formulations, comprising a hydrophobic trifunctional PFPA and a polymer bearing OH and PFPA groups. Those induced improved adhesion on PP compared to the golden standard plasma with polyurethane-based and two-component epoxy adhesives. Storing the coated substrates at room temperature for up to two months did not alter the adhesion performance, thus further ascribing the developed primers as a promising alternative to plasma treatment.

Effect of hydroxy-terminated hyperbranched polymer coated separator on the lithium-ion battery performances

Abstract The hydrophobicity of polyolefin separators causes poor compatibility with the internal environment of lithium-ion batteries and thus elevates lithium-ion migration barriers. In this research, hydroxy-terminated hyperbranched polymer (HTHP) coated separators are fabricated successfully based on the simple and easy-on impregnation method. Abundant hydroxyl groups in HTHP reinforce separator electrolyte affinity, generating the much lower contact angle and higher electrolyte uptake. Accordingly, HTHP-coated separators show broader electrochemical window and superior ionic conductivity and Li+ transport number, which facilitate the Li+ migration within porous pathways and hence maximally weaken counteranions-induced polarizations. The lower interfacial resistances also guarantee the Li+ accelerated diffusion via the separator–electrodes interfaces. Therefore, batteries containing modified separators exhibit optimized C-rate capacity and cycling stability. However, immoderate HTHP coating blocks partial pores and thus restricts Li+ transference, which deteriorates C-rate capacity and cycling durability in turn. This separator modification scheme possesses advantages of simple preparation, environment-friendly, and low manufacturing cost, providing practical guidance for low-cost and high-performance separator manufacture.

Carboxylesterase Activatable Molecular Probe for Personalized Treatment Guidance by Analyte-Induced Molecular Transformation.

Accurate visualization of tumor microenvironment is of great significance for personalized medicine. Here, we develop a near-infrared (NIR) fluorescence/photoacoustic (FL/PA) dual-mode molecular probe (denoted as NIR-CE) for distinguishing tumors based on carboxylesterase (CE) level by an analyte-induced molecular transformation (AIMT) strategy. The recognition moiety for CE activity is the acetyl unit of NIR-CE, generating the pre-product, NIR-CE-OH, which undergoes spontaneous hydrogen atom exchange between the nitrogen atoms in the indole group and the phenol hydroxyl group, eventually transforming into NIR-CE-H. In cellular experiments and in vivo blind studies, the human hepatoma cells and tumors with high level of CE were successfully distinguished by both NIR FL and PA imaging. Our findings provide a new molecular imaging strategy for personalized treatment guidance.

Unveiling the therapeutic potential of organotellurium(IV) Schiff base complexes through structural elucidation, antimalarial, antioxidant and antimicrobial studies

Infectious diseases have long been a formidable adversary to human health and well-being, presenting a persistent global challenge with far-reaching implication for individuals, communities and societies at large. Thus, with the aim of a combating agent against malarial and oxidant causing ailments, the newly synthesized Organotellurium(IV) complexes with a hydroxynaphthaldehyde Schiff base ligand are proposed in the present research. The structures of the complexes were established through various physical and spectral analysis. The weak electrolytic (8.77 to 35.08 ohm−1 cm2 mol−1) and crystalline nature of the compounds were demonstrated by molar conductivity and TGA, respectively. The ligand and complexes (7a-7f) shows molecular ion peaks at m/z 458.3563, 726.1039, 713.6978, 727.6179, 799.4780, 771.3178 and 799.3978 amu which were well consistent with their formula, revealing formation of compounds. The shifting of ligand's azomethine peak (7.74 ppm) and disappearance of naphthyl hydroxyl proton (12.28 ppm) in 1H NMR spectra confirmed the chelation of ligand with metal ion in proposed manner. In the FT-IR spectra, the complexation of ligand with metal ion was confirmed by disappearance of hydroxyl group (3355 cm−1) band and shifting of C = N (1245 cm−1) and CO (1632 cm−1) band whereas appearance of Te-O (of 285–293 cm−1) and Te-N (458–467 cm−1) bands, revealed the bonding of metal with metal and octahedral nature of the complexes. Optimized structures, HOMO-LUMO energies and associated chemical reactivity descriptors of the compounds were computed by DFT calculations. The in vitro studies demonstrate that the complexes 7c (1.06 ± 0.11 μM) and 7f (1.22 ± 0.05 μM) exhibited moderate inhibition of the Plasmodium falciparum 3D7 strain, complexes 7a (100.96 ± 0.32 μg/mL) and 7d (96.32 ± 0.40 μg/mL) demonstrated the highest free radical quenching ability. Complex 7c displayed the highest antibacterial actions, whereas 7f exhibited the highest antifungal actions against the tested pathogens. Molecular docking and ADMET studies demonstrated enhanced binding affinity of the complexes compared to the Schiff base and their drug-like qualities.

Carboxylesterase Activatable Molecular Probe for Personalized Treatment Guidance by Analyte‐Induced Molecular Transformation

Accurate visualization of tumor microenvironment is of great significance for personalized medicine. Here, we develop a near‐infrared (NIR) fluorescence/photoacoustic (FL/PA) dual‐mode molecular probe (denoted as NIR‐CE) for distinguishing tumors based on carboxylesterase (CE) level by an analyte‐induced molecular transformation (AIMT) strategy. The recognition moiety for CE activity is the acetyl unit of NIR‐CE, generating the pre‐product, NIR‐CE‐OH, which undergoes spontaneous hydrogen atom exchange between the nitrogen atoms in the indole group and the phenol hydroxyl group, eventually transforming into NIR‐CE‐H. In cellular experiments and in vivo blind studies, the human hepatoma cells and tumors with high level of CE were successfully distinguished by both NIR FL and PA imaging. Our findings provide a new molecular imaging strategy for personalized treatment guidance.

Ga(OTf)3 catalysed rapid nucleophilic substitution of propargyl alcohols with enoxysilanes

Ga(OTf)3 efficiently catalyses the nucleophilic substitution of the hydroxyl group of propargyl alcohols with enoxysilanes to aid in CC bond formation. The reactions can be performed in an undried solvent under air to obtain the desired products quickly in good yields. Other nucleophiles, such as indole, phenol, and furan are also suitable for this transformation. The use of inexpensive and readily available catalysts makes this method simple, convenient, and practical.

Ultra‐High Energy Density in Cyanoethyl Biomass Polymers

AbstractDielectric polymers are essential to capacitive capacitors widely used in modern electronic and electrical systems. Most useful dielectric polymers are derived from petroleum while environmentally sustainable dielectric biomass remains mostly unexplored although they are abundant, renewable, and cost‐effective. Here an ultrahigh energy density in cyanoethyl cellulose (CEC) and cyanoethyl pullulan (CEP) obtained by replacing the hydroxyl groups of cellulose and pullulan with cyanoethyl is reported. Large dielectric constants of 16.7 and 20.0 in CEC and CEP due to the strong polarity of cyanoethyl which are comparable to high‐dielectric ferroelectric polymers are shown. CEC and CEP show nearly no degradation of the dielectric constant with increasing electric fields, inhabiting the early polarization saturation and thus leading to improved energy density, which is different from relaxor ferroelectric polymers. Consequently, solution‐processable CEP films exhibit an ultrahigh discharged energy density of 28.2 J cm−3 with an efficiency of 72% at 600 MV m−1, outperforming other all‐organic dielectric biomass materials. The work paves the way for the development of high‐performance dielectric biomass for energy storage applications.

Selective SERS Detection of TATB Explosives Based on Hydroxy-Terminal Nanodiamond-Multilayer Graphene Substrate.

Selective surface-enhanced Raman scattering (SERS) detection of target explosives with good reproducibility is very important for monitoring soldiers' health and ecological environment. Here, the specific charge transfer pathway was constructed between a stable nanodiamond-multilayer graphene (MGD) film substrate and the target explosives. Two-step wet chemical oxidation methods of H2O2 (30%) and HNO3 (65%) solutions were used to regulate the terminal structure of MGD films. The experimental results showed that the hydroxyl (-OH) functional groups are successfully modified on the surface of MGD thin films, and the MGD-OH substrates having good selectivity for 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) explosive in mixed solutions of the TATB, 2,2-dinitroethene-1,1-diamine, 2,4,6-trinitrotoluene, and 1,3,5-trinitroperhydro-1,3,5-triazine explosives compared with MGD substrates were demonstrated. Finally, first-principles density functional theory simulations revealed that the SERS enhancement of the MGD-OH substrate is mainly attributed to the transferred electrons between the -NO2 groups of TATB and the -OH groups of the MGD-OH substrate.

Colorless and transparent polyimide nanocomposites using organically modified montmorillonite and mica

In this study, we introduce a method for replacing the glass used in existing display electronic materials, lighting, and solar cells by synthesizing a colorless and transparent polyimide (CPI) film with excellent mechanical properties and thermal stability using a combination of new monomers. Poly(amic acid) (PAA) was synthesized using dianhydride 4,4′-biphthalic anhydride (BPA) and diamine 2,2-bis(3-amino-4-hydroxyphenyl) hexafluoropropane (AHP). Various contents of organically modified montmorillonite (MMT) and mica were dispersed in PAA solution through solution intercalation, and then CPI hybrid films were prepared through multi-step thermal imidization. The organoclays synthesized to prepare CPI hybrid films were Cloisite 93A (CS-MMT) and hexadimethrine-mica (HM-Mica) based on MMT and mica, respectively. In particular, the diamine monomer AHP containing a –OH group was selected to increase the dispersibility and compatibility between the hydrophilic clays and the CPI matrix. To demonstrate the characteristics of CPI, the overall polymer structure was bent and a strong electron withdrawing –CF3 group was used as a substituent. The thermomechanical properties, morphology of clay dispersion, and optical transparency of the CPI hybrid films were investigated and compared according to the type and content of organoclays. Two types of organoclays, CS-MMT and HM-Mica, were dispersed in a CPI matrix at 1 to 7 wt%, respectively. In electron microscopy, most of the clays were uniformly dispersed in a plate-like shape of less than 20 nm at a certain critical content of the two types of organoclays, but agglomeration of the clays was observed when the content was higher than the critical content. Hybrids using HM-Mica had better thermomechanical properties and hybrids containing CS-MMT had better optical transparency.

Metal-organic frameworks constructed with base-acid mixed ligands and its potential as dual-functional fluorescent probe toward Fe3+/Al3+ ions

By virtue of mixed ligand strategy (2,5-Bis(1H-pyrazole-4-ylmethylene)-cyclopentanone and 2,5-dihydroxyterephthalic acid / terephthalic acid), four new metal–organic frameworks (MOFs) were fabricated and characterized. When 2,5-dihydroxyterephthalic acid acted as auxiliary ligand, MOFs 1–3 show 1D chain structure. 4 containing auxiliary ligand terephthalic acid (without − OH group) displays a 2D layer structure. Notably, 1 exhibits the significant selectivity toward Fe3+ and Al3+ ions, whereas the fluorescence intensity of 4 changed slightly in the presence of various metal ions, indicating that uncoordinated –OH in 1 plays an important role in sensing process. Moreover, it is revealed that 1 could act as dual-functional fluorescent probe toward Fe3+ and Al3+ with selectivity, sensitivity and reusability, and it could be prepared as fluorescent test papers for rapid on-site detection.

Plasma-deposited reactive species assisted synthesis of colloidal zinc-oxide nanostructures

A surface-wave microwave discharge is applied to deposit reactive oxygen and nitrogen species (RONS) into the liquid subsequently used as a medium for laser ablation of a Zn metallic target. It is shown that during laser ablation in plasma-treated liquids the H2O2 concentration decreases, while in deionized water (DIW) significant H2O2 is produced. Meanwhile, the pH—initially adjusted by applying reductive metals—increases in the acidic liquids and decreases in the alkaline ones. During months of storage the pH of colloids stabilize around pH 6, which insures the long-term stability of RONS. It is demonstrated that in DIW metallic Zn NPs are created, which gradually oxidize during storage, while in the plasma-treated liquids ZnO NPs are produced with the mean size of 18 nm. In the alkaline plasma-treated liquid the NPs form large aggregates, which slows the dissolution of NPs. In the acidic and neutral solutions besides NPs nanosheets are also formed, which during storage evolve into nanosheet networks as a result of the dissolution of NPs. The band gap of the colloidal ZnO is found to decrease with the formation of aggregates and nanosheet networks. The ZnO NPs ablated in plasma-treated liquids exhibit a high-intensity visible emission covering the green-to-red spectral region. The photoluminescence spectra is dominated by the orange-red emission—previously not detected in the case of laser-ablated ZnO NPs and attributed to the interstitial Zn and oxygen sites—and the yellow emission, which can be attributed to the OH groups on the surface. It is shown that during months of storage, due to the dissolution of NPs and formation of nanosheets, the intensity of the visible emission decreases and shifts to the blue-green spectral region.

Molecular Simulation Studies of Pharmaceutical Pollutant Removal (Rosuvastatin and Simvastatin) Using Novel Modified-MOF Nanostructures (UIO-66, UIO-66/Chitosan, and UIO-66/Oxidized Chitosan).

The ubiquitous presence of pharmaceutical pollutants in the environment significantly threatens human health and aquatic ecosystems. Conventional wastewater treatment processes often fall short of effectively removing these emerging contaminants. Therefore, the development of high-performance adsorbents is crucial for environmental remediation. This research utilizes molecular simulation to explore the potential of novel modified metal-organic frameworks (MOFs) in pharmaceutical pollutant removal, paving the way for the design of efficient wastewater treatment strategies. Utilizing UIO-66, a robust MOF, as the base material, we developed UIO-66 functionalized with chitosan (CHI) and oxidized chitosan (OCHI). These modified MOFs' physical and chemical properties were first investigated through various characterization techniques. Subsequently, molecular dynamics simulation (MDS) and Monte Carlo simulation (MCS) were employed to elucidate the adsorption mechanisms of rosuvastatin (ROSU) and simvastatin (SIMV), two prevalent pharmaceutical pollutants, onto these nanostructures. MCS calculations demonstrated a significant enhancement in the adsorption energy by incorporating CHI and OCHI into UIO-66. This increased ROSU from -14,522 to -16,459 kcal/mol and SIMV from -17,652 to -21,207 kcal/mol. Moreover, MDS reveals ROSU rejection rates in neat UIO-66 to be at 40%, rising to 60 and 70% with CHI and OCHI. Accumulation rates increase from 4 Å in UIO-66 to 6 and 9 Å in UIO-CHI and UIO-OCHI. Concentration analysis shows SIMV rejection surges from 50 to 90%, with accumulation rates increasing from 6 to 11 Å with CHI and OCHI in UIO-66. Functionalizing UIO-66 with CHI and OCHI significantly enhanced the adsorption capacity and selectivity for ROSU and SIMV. Abundant hydroxyl and amino groups facilitated strong interactions, improving performance over that of unmodified UIO-66. Surface functionalization plays a vital role in customizing the MOFs for pharmaceutical pollutant removal. These insights guide next-gen adsorbent development, offering high efficiency and selectivity for wastewater treatment.

Steering Interfacial Renovation with Highly Electronegative Cl Modulated Trinity Effect for Exceptional Durable Zinc Anode

AbstractThe poor anode/electrolyte interface triggered by abysmal dendritic growth and hydrogen evolution reactions (HER) hinders the development of aqueous zinc‐ion batteries (AZIBs). Here, a highly efficient electrolyte is formulated with sucralose (Sucral) additive to refresh solvated structure and steer interfacial renovation, for building highly electronegative Cl‐modulated trinity effect in the bulk‐interface between electrolyte and electrode. Experiment results and theoretical studies jointly reveal that Sucral with highly zincophilic and hydrophilic hydroxyl groups can remodel primary Zn2+ solvation shell and interrupt strong H‐bond network from H2O molecules, thus boosting fast de‐solvation and restricting undesirable HER. Simultaneously, three highly electronegative chlorides in the adsorbed Sucral possessing hydrophobic features can enable a H2O‐poor electric double‐layer (EDL), thus remodeling the Zn surface against corrosion. Additionally, it realizes preferential exposure of the Zn (002) plane for helping uniform interfacial deposition. The synergy of the above factors achieves a prolonged lifespan of 3000 h (1.0 mA cm−2, 1.0 mAh cm−2), much better than that with Sucrose (Suc) electrolyte. The Zn//V2O5 full cell at 5 A g−1 also maintains enhanced stability of 1500 cycles with 160 mAh g−1.

Gallic acid improves color quality and stability of red wine via physico-chemical interaction and chemical transformation as revealed by thermodynamics, real wine dynamics and benchmark quantum mechanical calculations

The aim of this study was to explore the copigmentation effect of gallic acid on red wine color and to dissect its mechanism at the molecular level. Three-dimensional studies, e.g., in model wine, in real wine and in silico, and multiple indicators, e.g., color, spectrum, thermodynamics and phenolic dynamics, were employed. The results showed that gallic acid significantly enhanced the color quality and stability of red wine. Physico-chemical interactions and chemical transformations should be the most likely mechanism, and physico-chemical interactions are also a prerequisite for chemical transformations. QM calculations of the physico-chemical interactions proved that the binding between gallic acid and malvidin-3-O-glucoside is a spontaneous exothermic reaction driven by hydrogen bonding and dispersion forces. The sugar moiety of malvidin-3-O-glucoside and the phenolic hydroxyl groups of gallic acid affect the formation of hydrogen bonds, while the dispersion interaction was related to the stacking of the molecular skeleton.

Towards a natural treatment for mania: red onion husk extract modulates neuronal resilience, redox signalling, and glial activation

BackgroundRed onion husk, a readily available agricultural waste material, contains diverse bioactive compounds with potential health benefits. This study aimed to assess the safety and therapeutic potential of red onion husk extract in managing manic-like symptoms and associated neurochemical dysfunctions.MethodsAcute and repeated oral dose studies were conducted in mice and rats to evaluate the safety profile of the extract. FT-IR analysis identified functional groups in the extract, while GC-MS analysis identified specific bioactive compounds in the flavonoid-rich fraction. A ketamine-induced manic behaviour model in Wistar rats was employed to assess the extract’s efficacy in attenuating manic-like symptoms. Behavioural and neurochemical analyses were performed to further investigate the extract’s effects.ResultsThe extract demonstrated a favourable safety profile in both acute and repeated dose studies. FT-IR analysis revealed a complex mixture of organic compounds, including hydroxyl groups, alkynes/nitriles, aromatic and non-aromatic C = C bonds, amines, and polysaccharides. GC-MS analysis identified 17 bioactive compounds, including five-methyl-2-phenylindolizine, methadone N-oxide, and 3-phenylthiane, S-oxide. Ketamine administration significantly increased oxidative stress markers, TBARS, and suppressed antioxidant enzyme activities (SOD, GPx, CAT) in both the cerebral cortex and hippocampus, alongside elevated acetylcholinesterase (AchE) activity, indicating enhanced neuronal excitability. Pre-treatment with FRF (25 mg/kg) effectively mitigated ketamine-induced oxidative stress, as evidenced by reduced TBARS levels and partially restored SOD and GPx activities. Interestingly, FRF significantly increased CAT activity (p < 0.001), potentially suggesting an additional compensatory mechanism. Notably, FRF pre-treatment also counteracted ketamine-upregulated AchE activity, offering neuroprotection against heightened neuronal excitability.ConclusionRed onion husk extract exhibits a favourable safety profile and exerts potent antioxidant and neuroprotective effects, possibly through modulating Nrf2 signalling pathways. Its ability to counteract ketamine-induced oxidative stress and neuronal hyperactivity highlights its potential as a complementary therapeutic strategy for managing manic episodes in bipolar disorder. Further research is warranted to elucidate the precise molecular mechanisms underlying FRF’s action and explore its clinical efficacy in human studies.

Spherical g-C3N4@PDA nanocarrier for synergistic chemo-photothermal tumor therapy

In this paper, by wrapping the near-infrared (NIR) response polydopamine (PDA) as a nanocoating on the surface of spherical nano graphitic phase carbon nitride (g-C3N4), a multifunctional g-C3N4/PDA (CNP) nanocarrier platform was prepared. The π-conjugation system in PDA and the electronegative hydroxyl groups on the surface of CNP promote the creation of abundant active sites, which had a high drug loading rate of about 98.5 % for the electropositive GA. Due to the strong NIR reaction of CNP, the release of GA from CNP/GA can be greatly accelerated by the rising temperature, bonding disruption and charge transfer. Moreover, the photo-generated electron-hole pairs could be excited by the NIR effect of CNP, which promotes the production of ROS (·OH, ·O2– and 1O2) to induce apoptosis in HepG2 cells. Thus, the present spherical CNP nanocarrier with a combination of enzyme-mimic activity and NIR-responsive properties has a great potential for chemo-photothermal synergistic tumor therapy.

The Heptazine-Based Materials through Intrinsically Modification for the Cycloaddition of CO2 and Bisepoxides.

For the efficient utilization of CO2 into valuable product, the attractive carbon nitride catalysts have been widely studied. In this work, heptazine-related materials with varying degree of polymerization were designed by an intrinsically modification strategy and employed in the cycloaddition of CO2 with the bisepoxide 1, 4-butanediol diglycidyl ether (BDODGE). We initially figured out that the sample prepared at 450 °C contained more melem hydrate, exhibiting the best performance. The epoxides conversion and corresponding cyclic carbonates selectivity could achieve 93.1 % and 99.3 % at 140 °C for 20 h without any cocatalyst and solvent, respectively. Results of the catalytic tests suggested that the high catalytic activity was dependent on big size porous structure and the synergetic effect of active amino groups and -OH groups. The role of water in maintaining the specific structure and providing active site has been proved. Moreover, the CN-450-W catalyst exhibited outstanding recycling stability. And finally, a plausible reaction mechanism was proposed.

Identification, Characterization, and Electronic Structures of Interconvertible Cobalt-Oxygen TAML Intermediates.

The reaction of Li[(TAML)CoIII]·3H2O (TAML = tetraamido macrocyclic tetraanionic ligand) with iodosylbenzene at 253 K in acetone in the presence of redox-innocent metal ions (Sc(OTf)3 and Y(OTf)3) or triflic acid affords a blue species 1, which is converted reversibly to a green species 2 upon cooling to 193 K. The electronic structures of 1 and 2 have been determined by combining advanced spectroscopic techniques (X-band electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), X-ray absorption spectroscopy/extended X-ray absorption fine structure (XAS/EXAFS), and magnetic circular dichroism (MCD)) with ab initio theoretical studies. Complex 1 is best represented as an S = 1/2 [(Sol)(TAML•+)CoIII---OH(LA)]- species (LA = Lewis/Brønsted acid and Sol = solvent), where an S = 1 Co(III) center is antiferromagnetically coupled to S = 1/2 TAML•+, which represents a one-electron oxidized TAML ligand. In contrast, complex 2, also with an S = 1/2 ground state, is found to be multiconfigurational with contributions of both the resonance forms [(H-TAML)CoIV═O(LA)]- and [(H-TAML•+)CoIII═O(LA)]-; H-TAML and H-TAML•+ represent the protonated forms of TAML and TAML•+ ligands, respectively. Thus, the interconversion of 1 and 2 is associated with a LA-associated tautomerization event, whereby H+ shifts from the terminal -OH group to TAML•+ with the concomitant formation of a terminal cobalt-oxo species possessing both singlet (SCo = 0) Co(III) and doublet (SCo = 1/2) Co(IV) characters. The reactivities of 1 and 2 at different temperatures have been investigated in oxygen atom transfer (OAT) and hydrogen atom transfer (HAT) reactions to compare the activation enthalpies and entropies of 1 and 2.