Cobalt(II) Aqua Complex-Mediated Hydrogen Peroxide Activation: Possible Roles of HOOOH and Co(II)-OOOH Intermediates in Singlet Oxygen Generation.

Density functional theory (DFT) calculations indicate that [Co(HO)] reacts with two HO molecules to form [(HO)Co(OOH)(HO)] reactant complexes, which decompose through three distinct pathways depending on the relative orientation between the coordinated OOH and HO ligands. The reactive intermediates produced via these activation pathways include hydroperoxyl (OOH)/superoxide (O) radicals, singlet oxygen (O), and Co(III) species [(HO)Co(O)], [(HO)Co(OH)], and [(HO)Co(OH)]. The Co(III) species display from moderate to strong oxidizing abilities that have long been overlooked.

Intrinsic 77 K Phosphorescence Characteristics and Computational Modeling of Ru(II)-(Bidentate Cyclometalated-Aromatic Ligand) Chromophores: Their Relatively Low Nonradiative Rate Constants Originating from Low Spin-Orbit Coupling Driven Vibronic Coupling Amplitudes between Emitting and Ground States.

We investigated the photoinduced relaxation of Kasha-type emitting ruthenium-(bidentate cyclometalated aromatic ligand), Ru-CM, chromophores of [Ru(pzpy)(CM)] ions (CM = 1-phenylisoquinoline, 2,3-diphenylpyrazine, and 1,4-diazatriphenylene and pzpy = 2-pyrazol-1-yl-pyridine). This is the first report of the phosphorescence behavior of pure Ru-(bidentate CM) chromophores. The 77 K photoinduced relaxation characteristics of phosphorescence chromophores showed emission quantum yields higher than those of reference Ru-bpy (bpy = 2,2'-bipyridine) chromophores in the emission region of 670-900 nm.

Steric and electronic influence on Cu-Cu short contacts in β-thioketiminato tricopper(I) clusters.

A series of β-thioketiminate copper(I) complex trimers [LCu] were synthesized by modifying the ligand framework with electron-withdrawing groups (F and Cl) or electron-donating groups (Pr and Me) at the -aryl ring as well as with CF groups on the chelating backbone. This ligand modification significantly impacts the enhancement of Cu⋯Cu short contacts, which can be rationalized by using steric and electronic factors of the chelated ligand. We observed that this intramolecular cuprophilicity among [LCu] complexes is primarily governed by the size of -aryl -substituents.

KCO-mediated annulation of 1,3-acetonedicarboxylates with 2-fluoro-1-nitroarenes: synthesis of indoles.

The KCO-mediated one-pot reaction of 1,3-acetonedicarboxylates with 2 equiv. of substituted 2-fluoro-1-nitrobenzenes has been developed to synthesize various 2,3-dicarboxylate indoles a tandem annulation pathway. In the effective reaction, one carbon-carbon double bond, one carbon-carbon single bond and one carbon-nitrogen single bond are formed under open-vessel conditions.

Unraveling the binding mechanisms of SARS-CoV-2 variants through molecular simulations.

The emergence of SARS-CoV-2 variants like Delta (AY.29) and Omicron (EG.5) poses continued challenges for vaccines and therapeutics.

Improvement of catalytic activity of aluminum complexes for the ring-opening polymerization of ε-caprolactone: aluminum thioamidate and thioureidate systems.

In this study, a series of Al complexes bearing amidates, thioamidates, ureidates, and thioureidates were synthesized and their catalytic activity for ε-caprolactone (CL) polymerization was evaluated. SPr-Al exhibited a higher catalytic activity than OPr-Al (3.2 times as high for CL polymerization; [CL] : [SPr-Al] : [BnOH] = 100 : 0.

DFT study on the catalytic decomposition of hydrogen peroxide by iron complexes of nitrilotriacetate.

The Fenton system in the presence of nitrilotriacetate (NTA) ligand is studied by DFT approach. The calculations show that complexation of Fe(II) with NTA significantly facilitates the H O activation. The ferric-hydroperoxo intermediate NTAFe(III)OOH predominantly decays via the disproportionation into NTAFe(II)OH and NTAFe(IV)O involving the formation of a μ-1,2-hydroperoxo-bridged biferric intermediate.

Ligand Degradation Study of Unsymmetrical β-Diketiminato Copper Dioxygen Adducts: The Length Chelating Arm Effect.

An investigation on the reactivity of O binding to unsymmetrical β-diketiminato copper(I) complexes by spectroscopic and titration analysis was performed. The length of chelating pyridyl arms (pyridylmethyl arm vs pyridylethyl arm) leads to the formation of mono- or di-nuclear copper-dioxygen species at -80 °C. The pyridylmethyl arm adduct (CuO) forms mononuclear copper-oxygen species and shows ligand degradation, resulting in the formation of (2,3)--(2,6-diisopropylphenyl)-4-((()-pyridin-2-ylmethylene)amino)pent-3-en-2-imine, which slowly converts to its cyclization isomer 1-(2,6-diisopropylphenyl)-4,6-dimethyl-2-(pyridin-2-yl)-1,2-dihydropyrimidine after addition of NHOH at room temperature.

Denticity governs the formation of β-thioketiminato tri-copper(I) and mono-copper(I) complexes.

Two classes of β-thioketiminate ligands, SN chelators (HL1 and HL2) and SNN chelators (HL3 and HL4), were prepared to understand their coordination behavior in copper(I) complex formation. The formation of these copper(I) complexes bearing β-thioketiminate ligands and their corresponding adducts toward isocyanide, PPh, and CO was investigated to address two important issues. First, whether the denticity governs the copper(I) thiolate species formation between SN chelators and SNN chelators.

An investigation on catalytic nitrite reduction reaction by bioinspired Cu complexes.

Catalytic nitrite reductions by Cu complexes containing anionic Tp, neutral Tpm, or neutral TIC ligands in the presence of L-ascorbic acid, which served as an electron donor and proton source, were investigated. The results showed that auxiliary ligands are important for copper-mediated catalytic nitrite reduction. Furthermore, the electronic effects of the ligand govern the nitrite reduction efficiency, which should be considered at two control points: one is the susceptibility of the LCu-nitrite species to protonation and the other is the susceptibility of LCu to reduction giving LCu.

Synthesis of Distorted Nitrogen-Doped Nanographenes by Partially Oxidative Cyclodehydrogenation Reaction.

A series of partially fused N-doped nanographenes (2-4) are synthesized via the oxidative cyclodehydrogenation of oligoaryl-substituted dibenzo[e,l]pyrene (1), and five, six, and seven new C-C bonds are formed, respectively, implying stepwise C-C bond fusion and extended π-conjugation. Single-crystal X-ray diffraction analysis of compound 4 a revealed that the presence of sterically demanding groups hindered the formation of planar and fully fused nanographene in the oxidative cyclodehydrogenation reaction step. Optical study of compounds 2 to 4 showed that extended π-conjugation leads to a regular stepwise bathochromic shift in the absorption and emission spectra.

Ring-Opening Polymerization of ε-Caprolactone by Using Aluminum Complexes Bearing Aryl Thioether Phenolates: Labile Thioether Chelation.

In this study, aluminum complexes bearing ferrocene-based and arylthiomethylphenolate ligands were synthesized, and their catalytic activity for ε-caprolactone (CL) polymerization was investigated. The catalytic activity of the reduced form of Al complexes was higher than that of the oxidized form. The CL polymerization rate of the reduced form (75 min, conversion = 100%) was higher than that of the oxidized form (4320 min, conversion = 45%), and the CL polymerization rate of (40 min, conversion = 100%) was higher than that of (60 min, conversion = 97%).

Responsive fluorescence enhancement for in vivo Cu(II) monitoring in zebrafish larvae.

Several neurodegenerative diseases are ascribed to disorders caused by the secretion of Cu ions. However, a majority of the current techniques for copper ion detection are restricted to in vivo monitoring and nonspecific interactions. Their methods are limited to the systematic analysis of Cu ions in living organisms.

DFT mechanistic study on the formation of 8-oxoguanine and spiroiminodihydantoin mediated by iron Fenton reactions.

Fenton reactions unavoidably take place in the human body and have been demonstrated to cause oxidative DNA damage. However, the molecular-level understanding of DNA damage mediated by Fenton reactions is limited. Herein, density functional theory (DFT) calculations were made to investigate the counterion effects on aqueous Fenton reactions and the detailed mechanisms of chemical modifications to guanine induced by Fenton reactions.

Synergistic Catalysis by Brønsted Acid/Carbodicarbene Mimicking Frustrated Lewis Pair-Like Reactivity.

Carbodicarbene (CDC), unique carbenic entities bearing two lone pairs of electrons are well-known for their strong Lewis basicity. We demonstrate herein, upon introducing a weak Brønsted acid benzyl alcohol (BnOH) as a co-modulator, CDC is remolded into a Frustrated Lewis Pair (FLP)-like reactivity. DFT calculation and experimental evidence show BnOH loosely interacting with the binding pocket of CDC via H-bonding and π-π stacking.

Near-IR Charge-Transfer Emission at 77 K and Density Functional Theory Modeling of Ruthenium(II)-Dipyrrinato Chromophores: High Phosphorescence Efficiency of the Emitting State Related to Spin-Orbit Coupling Mediation of Intensity from Numerous Low-Energy Singlet Excited States.

Efficient charge-transfer (CT) phosphorescence in the near-IR (NIR) spectral region is reported for four substituted Ru-(R-dipyrrinato) complexes, [Ru(bpy)(R-dipy)](PF), where bpy is 2,2'-bipyridine and the substituent R is phenyl (ph), 2,4,6-trimethylphenyl, 4-carboxyphenyl (HOOC-ph), or 4-pyridinyl. The experimentally determined phosphorescence efficiency, ι = /(ν) (where and ν are the phosphorescence rate constant and the phosphorescence frequency, respectively), of the [Ru(bpy)(R-dipy)] complexes was approximately double that of [Ru(bpy)(Am)] complexes (Am = ammine ligand) in the NIR region. Density functional theory (DFT) modeling indicated two strikingly different electronic configurations of the triplet emitting state (T) in the two types of complexes.

In vivo monitoring of carbonic anhydrase expression during the growth of larval zebrafish: a new environment-sensitive fluorophore for responsive turn-on fluorescence.

This study monitors the dynamic progress of a newly developed background-free, target responsive strategy; 2,3-dihydroquinolin-4-imine (DQI) that can instantly respond to environmental changes with fluorescence enhancement, revealing a comprehensive platform for in vivo fluorescence bioimaging of mebrane-bound carbonic anhydrase II in HeLa cells and its expression during the growth of larval zebrafish.

CuBr-Mediated One-Pot Synthesis of Sulfonyl 9-Fluorenylidenes.

In this article, a high-yield method for the synthesis of sulfonyl 9-fluorenylidenes is described, which consists of a one-pot straightforward three-step synthetic route, including (i) CuBr-mediated α-bromination of -arylacetophenone, (ii) sequential nucleophilic substitution of the resulting α-bromo -arylacetophenone with sodium sulfinate (RSONa), and (iii) the CuBr-mediated intramolecular Friedel-Crafts cyclizative dehydration. A plausible mechanism is proposed and discussed. This protocol provides a highly effective regio- and stereoselective annulation via the formation of one carbon-carbon (C-C) bond and one carbon-sulfur (C-S) bond.

The Mechanical Behaviors of Polyethylene/Silver Nanoparticle Composites: an Insight from Molecular Dynamics study.

This research uses molecular dynamics simulation (MD) to study the mechanical properties of pristine polyethylene (PE) and its composites which include silver nanoparticles (PE/AgNPs) at two AgNP weight fractions of 1.05 wt% and 3.10 wt%.

Construction of Sulfonyl Dihydrobenzo[]xanthen-7-ones Core via NHOAc/PdCl/CuCl-Mediated Double Cyclocondensation of α-Sulfonyl -Hydroxyacetophenones with 2-Allylbenzaldehydes.

NHOAc/PdCl/CuCl mediated domino double cyclocondensation of α-sulfonyl -hydroxyacetophenones and 2-allylbenzaldehydes provides tetracyclic sulfonyl dihydrobenzo[]xanthen-7-one core with good to excellent yields in MeOH. The intermediates contain a 3-sulfonyl flavanone motif. Only water is generated as a byproduct.

Ovalbumin-Loaded Gelation Microneedles Made of Predictive Formulation by Molecular Dynamics Simulation for Enhancement of Skin Immunization.

Gelation microneedle (GMNs) based vaccinations with tumor antigens have been considered to be an attractive method for transcutaneous immunization because of their superior ability to deliver vaccines through the stratum corneum (SC) in a minimally invasive manner, which subsequently induces adaptive antitumor immunity. In this study, molecular dynamics (MD) uniaxial tension simulations were conducted to predict the formulation of poly(vinyl alcohol) (PVA; possesses high water solubility) and poly(methyl vinyl ether-altmaleic anhydride) (PMVEMA; possesses high mechanical strength) blend that has the strongest mechanical properties. To validate the accuracy of the Dreiding potential for these two polymers, their densities and Hildebrand solubility parameters were first predicted using MD simulations.

Low-Temperature Spectra and Density Functional Theory Modeling of Ru(II)-Bipyridine Complexes with Cyclometalated Ancillary Ligands: The Excited State Spin-Orbit Coupling Origin of Variations in Emission Efficiencies.

The 77 K emission spectra of cyclometalated ruthenium(II)-2,2'-bipyridine (CM-Ru-bpy) chromophores are very similar to those of related Ru-bpy complexes with am(m)ine or diimmine ancillary ligands, and density functional theory (DFT) modeling confirms that the lowest energy triplet metal to ligand charge transfer (MLCT) excited states of CM-Ru-bpy and related Ru-bpy complexes have very similar electronic configurations. However, the phosphorescence decay efficiencies of CM-Ru-bpy excited states are about twice those of the conventional Ru-bpy analogues. In contrast to the similar MLCT excited state electronic configurations of the two classes of complexes, the CM-Ru-bpy chromophores have much broader visible region MLCT absorptions resulting from several overlapping transitions, even at 87 K.

Why the Reactive Oxygen Species of the Fenton Reaction Switches from Oxoiron(IV) Species to Hydroxyl Radical in Phosphate Buffer Solutions? A Computational Rationale.

It has been shown that the major reactive oxygen species (ROS) generated by the aqueous reaction of Fe(II) and HO (i.e., the Fenton reaction) are high-valent oxoiron(IV) species, whereas the hydroxyl radical plays a role only in very acidic conditions.

Synthesis of 2-Sulfonyl Indenes and Indanes.

In this paper, we developed facile and high-yield synthetic routes for the preparation of 2-sulfonyl indenes and indanes, including: (i) Amberlyst-15-promoted Knoevenagel reaction of β-ketosulfones and arylaldehydes in refluxing toluene; (ii) Grignard reagent (R'MgBr) or reducing reagent (NaBH) promoted regio- and/or stereocontrolled 1,4-addition or 1,4-/1,2-reduction of the resulting sulfonyl chalcones in THF or MeOH/THF at 25 °C; and then (iii) Amberlyst-15 mediated intramolecular Friedel-Crafts annulation of the corresponding β-ketosulfones or β-hydroxysulfones in toluene at reflux. This present method describes a highly efficient (3 + 2) annulation via the formation of two carbon-carbon (C-C) bonds. The DFT calculations were utilized to rationalize the regioselectivity of the addition reaction.