A DFT Study of Catechol Polymer Adhesion onto γ-Alumina (110) Surfaces.

The adhesion mechanism of catechol, a key functional group in marine bioadhesives, to dehydroxylated γ-alumina (γ-AlO) (110) and hydroxylated (γ-AlO) (110) surfaces was investigated using periodic density functional theory (DFT) calculations. Adhesion interface models were constructed by integrating catechol, modeled after the experimentally synthesized poly(3,4-dihydroxystyrene), with γ-AlO (110) and γ-AlO (110) surfaces, referred to as the catechol/γ-AlO (110) and catechol/γ-AlO (110) interfaces. Stable catechol-surface complexes, adhesion energies, and interaction sites were identified through DFT-based geometric optimizations of selected models.

Visible-Light-Driven Cycloaddition of CO with Epoxides Catalyzed by Recyclable Mg⁺/TiO Photocatalyst Operating at Room Temperature.

The utilization of CO as a C building block remains a key challenge in sustainable organic synthesis. We now report a recyclable metal ion modified titanium oxide (M/TiO, where M represents Mg, Rh, Cr, Mn, Fe, Ni, Cu, Zn, and Al) photocatalytic system used with a tetrabutylammonium halide (TBAX, X = I, Br, Cl) as a co-catalyst, which enables the cycloaddition of CO with various epoxides under visible light irradiation at room temperature. This catalyst system exhibits a broad range of responsiveness to visible light and is compatible with simulated solar light, and operates solvent-free conditions without the need for high pressure.

Theoretical Study of Nitric Oxide Reduction Catalyzed by a Mononuclear Nonheme Iron Complex.

In contrast with the extensive studies on the mechanism of nitric oxide (NO) reduction to nitrous oxide (NO) catalyzed by heme-type complexes, the analogous reaction catalyzed by mononuclear nonheme-type complexes remains scarcely explored. In this study, density functional theory (DFT) calculations were performed on the nonheme mononuclear iron complex [Fe(MeTACN)(SSiMe)] (TACN = 1,4,7-triazacyclononane) to unveil the mechanism of the NO reduction to NO. The results reveal that the NO reduction can be divided into three steps: (i) N-N bond formation between NO and an iron nitrosyl complex, (ii) change in the coordination mode of the resulting hyponitrite (NO) ligand, and (iii) N-O bond cleavage.

Mechanistic Insight into Water Oxidation Catalysis by a Mononuclear Ruthenium Complex.

A reaction mechanism of water oxidation involving a mononuclear Ru-oxo complex () as an intermediate with use of (NH)[Ce(NO)] (CAN) as an oxidant has been scrutinized to provide a clear view of O-O bond formation and O release. This work includes the spectroscopic and theoretical characterization of an end-on Ru-superoxo complex (), together with the crystallographic characterization of a side-on Ru-peroxo complex () which should be in equilibrium with in an aqueous solution. The formation of the Ru-oxo intermediate as a responsible species for the water oxidation was supported by a square wave voltammogram of in an aqueous solution, showing an oxidation wave at +1.

Photosynthesis of NH from NO Using CH in Homogenous Rhenium Catalysis.

We present Re catalysis of one-pot synthesis of NH from NO using CH as a reductant under UV light irradiation at room temperature. NO leads to environmental issues such as water contamination, eutrophication, and biodiversity loss. In a natural system and a sewage facility, NO can be detoxified to N using hydrogen donors by a microbial process.

Theoretical Study of Guanine Oxidation Catalyzed by a Ruthenium Complex with an Oxygen Molecule.

The oxidation of an aromatic ring in guanosine monophosphate by a Ru-aqua complex, [Ru(OH)(η-CMe)(bpy)] (bpy = 2,2'-bipyridine), using O gases in an aqueous solution has been reported (Takenaka et al. 13, 3480-3184). However, its mechanism has not been sufficiently clarified to facilitate the design of optimal catalysts.

Redox-active tin(II) complexes with sterically demanding -phenylenediamido ligands and their reactivity with organic azides.

A series of tin(II) complexes R1 supported by phenylene-1,2-diamido ligands containing a bulky -substituent TIPT (2,4,2'',4''-tetraisopropyl-[1,1':3',1'']terphenyl) and different aromatic substituents R (Cl, H, Me, OMe) at the 4,5-positions and by a naphthalene-2,3-diamido ligand with the TIPT substituent naph1 are synthesised and characterised. Tin(II) complexes SnLMe and SnLPh(tBu)2 supported by phenylene-1,2-diamido ligands with sterically less hindered -substituents, Ph or 3,5-di--butylphenyl, are also prepared as reference complexes. Crystal structures of R1 and naph1 show that the tin(II) centers are coordinated with the two amido nitrogen atoms of the respective deprotonated chelating ligand and two solvent molecules such as tetrahydrofuran and/or acetonitrile.

Mechanistic studies of NO reduction reactions involving copper complexes: encouragement of DFT calculations.

The reduction of nitrogen oxides (NO), which is mainly mediated by metalloenzymes and metal complexes, is a critical process in the nitrogen cycle and environmental remediation. This Frontier article highlights the importance of density functional theory (DFT) calculations to gain mechanistic insights into nitrite (NO) and nitric oxide (NO) reduction reactions facilitated by copper complexes by focusing on two key processes: the reduction of NO to NO by a monocopper complex, with special emphasis on the concerted proton-electron transfer, and the reduction of NO to NO by a dicopper complex, which involves N-N bond formation, NO isomerization, and N-O bond cleavage. These findings underscore the utility of DFT calculations in unraveling complicated reaction mechanisms and offer a foundation for future research aimed at improving the reactivity of transition metal complexes in NO reduction reactions.

The Effect of Intramolecular Proton Transfer on the Mechanism of NO Reduction to NO by a Copper Complex: A DFT Study.

DFT calculations were performed to explore the mechanism underlying the reduction of NO to NO by a Cu complex. A nitrosyl complex reacts with another NO molecule and the Cu complex, leading to the formation of a dicopper-hyponitrite complex (CuNO). The first steps follow a common pathway until the formation of the intermediate [Cu-NO], after which the reaction pathway diverges into three CuNO species: κ-N,N', κ-O,O', and κ-N,O,O'.

B-Catalyzed Carbonylation of Carbon Tetrahalides: Using a Broad Range of Visible Light to Access Diverse Carbonyl Compounds.

Visible-light-driven organic synthesis is a green and sustainable method for producing fine chemicals and is highly desirable at both laboratory and industrial scales. In this study, we developed a broad-range (including the red region) visible-light-driven carbonylation of CCl, CBr, and CBrF with nucleophiles, such as amines and alcohols, using a B-Mg/TiO hybrid catalyst. Carbonyl molecules such as ureas, carbamates, carbonate esters, and carbamoyl fluorides were synthesized with high selectivity and efficiency under mild conditions.

A Stealthiness Evaluation of Main Chain Carboxybetaine Polymer Modified into Liposome.

Acrylamide polymers with zwitterionic carboxybetaine (CB) side groups have attracted attention as stealth polymers that do not induce antibodies when conjugated to proteins. However, they induce antibodies when modified onto liposomes. We hypothesized that antibodies are produced against polymer backbones rather than CB side groups.

Dynamic Luminescence Vapochromism of Pyridinium-Based Organic Salts.

Organic vapochromic materials which undergo a drastic change in their photophysical properties upon exposure to vapors or gases are attracting growing scientific attention because of their low price and wide range of possible applications. In this work, luminescence vapochromism of carbazole-pyridinium-based organic salts with a general structure of (CzPy)X (CzPy=2,3-di(9H-carbazol-9-yl)pyridinium ion; X=Cl, Br or I) is reported. It was found that (CzPy)X compounds form J-aggregates, which rearranged back to monomeric form upon exposure to methanol, ethanol, acetone, and water vapors.

Ferrocenyl PNNP Ligands-Controlled Chromium Complex-Catalyzed Photocatalytic Reduction of CO to Formic Acid.

3d-transition metal complexes have been gaining much attention as promising candidates for photocatalytic carbon dioxide (CO) reduction systems. In contrast to the group 7-12 elements, Cr in group 6 has not yet been investigated as the catalyst of CO photoreduction because of its intrinsic disadvantages. Cr has a weak reducing ability due to an insufficient number of d electrons and high Lewis acidity which may deactivate the catalyst by strong coordination with a product formate.

Self-Assembly of Thienopyrrole-Fused Thiadiazoles Containing an Amide Linker: Control of Supramolecular Polymerization Mechanism and Chiroptical Properties by Trialkoxy Side Chains.

Three thienopyrrole-fused thiadiazole (TPT) fluorescent dyes featuring a common amide linker and different alkoxy substituents on peripheral trialkoxybenzene moieties were synthesized, and their self-assembly behavior in solution was investigated. The obtained results revealed a substantial steric effect of the alkoxy substituents on the supramolecular polymerization mechanism, which results from a combination of π-stacking and hydrogen (H)-bonding interactions. Detailed spectroscopic measurements revealed that with increasing steric demand of the substituents, the supramolecular polymerization processes in pure methylcyclohexane (MCH) or a mixture of MCH and toluene become temperature-sensitive and enthalpically favorable, resulting in a change from the isodesmic assembly mechanism to the cooperative mechanism.

Cyclopropanation Using Electrons Derived from Hydrogen: Reaction of Alkenes and Hydrogen without Hydrogenation.

Have you ever imagined reactions of alkenes with hydrogen that result in anything other than hydrogenation or hydrogenative C-C coupling? We have long sought to develop not only hydrogenation catalysts that activate H as hydride ions but also electron transfer catalysts that activate H as a direct electron donor. Here, we report the reductive cyclopropanation of alkenes using an iridium electron storage catalyst with H as the electron source without releasing metal waste from the reductant. We discuss the catalytic mechanism with selectivity to give the -isomer.

Polar Crystals Using Molecular Chirality: Pseudosymmetric Crystallization toward Polarization Switching Materials.

Polar compounds with switchable polarization properties are applicable in various devices such as ferroelectric memory and pyroelectric sensors. However, a strategy to prepare polar compounds has not been established. We report a rational synthesis of a polar CoGa crystal using chiral cth ligands (-cth and -cth, cth = 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane).

Efficient Synthesis and Structural Analysis of Chiral 4,4'-Biazulene.

4,4'-Biazulene is a potentially attractive key component of an axially chiral biaryl compound, however, its structure and properties have not been clarified owing to the lack of its efficient synthesis. We report a breakthrough in the reliable synthesis of 4,4'-biazulene, which is achieved by the access to azulen-4-ylboronic acid pinacol ester and 4-iodoazulene as novel key synthetic intermediates for the Suzuki-Miyaura cross-coupling reaction. The X-ray crystallographic analysis of 4,4'-biazulene confirmed its axial chirality.

A rhodium(II)/rhodium(III) redox couple for C-H bond amination with alkylazides: a rhodium(III)-nitrenoid intermediate with a tetradentate [14]-macrocyclic ligand.

The catalytic activity of a rhodium(II) dimer complex, [Rh(TMAA)] (TMAA = tetramethyltetraaza[14]annulene), in C-H amination reactions with organic azides is explored. Organic azides (N-R) with an electron-withdrawing group such as a sulfonyl group (trisylazide; R = S(O)CH (Trs)) and a simple alkyl group (R = (CH)Ph, (CH)OCHPh, CHPh, or CHNO) are employed in intra- and intermolecular C-H bond amination reactions. The spectroscopic analysis using ESI-mass and EPR spectroscopy techniques on the reaction intermediate generated from [Rh(TMAA)] and N-R reveals that a rhodium(III)-nitrenoid species is an active oxidant in the C-H bond amination reaction.

Enhancement of Reactivity of a Ru-Oxo Complex in Oxygen-Atom-Transfer Catalysis by Hydrogen-Bonding with Amide Moieties in the Second Coordination Sphere.

We have synthesized and characterized a Ru-OH complex (), which has a pentadentate ligand with two pivalamide groups as bulky hydrogen-bonding (HB) moieties in the second coordination sphere (SCS). Complex exhibits a coordination equilibrium through the coordination of one of the pivalamide oxygens to the Ru center in water, affording a η-coordinated complex, . A detailed thermodynamic analysis of the coordination equilibrium revealed that the formation of from is entropy-driven owing to the dissociation of the axial aqua ligand in .

Mechanistic Study of Reduction of Nitrite to NO by the Copper(II) Complex: Different Concerted Proton-Electron Transfer Reactivity between Nitrite and Nitro Complexes.

The literature contains numerous reports of copper complexes for nitrite (NO) reduction. However, details of how protons and electrons arrive and how nitric oxide (NO) is released remain unknown. The influence of the coordination mode of nitrite on reactivity is also under debate.

Effect of Macrocycles on the Photochemical and Electrochemical Properties of Cobalt-Dehydrocorrin Complex: Formation and Investigation of Co(I) Species.

Co(II)-pyrocobester (), a dehydrocorrin complex, was semisynthesized from vitamin B (cyanocobalamin), and its photochemical and electrochemical properties were investigated and compared to those of the cobester (), the cobalt-corrin complex. The UV-vis absorptions of in CHCl, ascribed to the π-π* transition, were red-shifted compared to those of due to the π-expansion of the macrocycle in the pyrocobester. The reversible redox couple of was observed at = -0.

Site-selective radical reactions of kinetically stable open-shell singlet diradicaloid difluorenoheteroles with tributyltin hydride and azo-based radical initiators.

We have demonstrated site-selective radical reactions of the kinetically stable open-shell singlet diradicaloids difluoreno[3,4-:4',3'-]thiophene (DFTh) and difluoreno[3,4-:4',3'-]furan (DFFu) with tributyltin hydride (HSn(-Bu)) and azo-based radical initiators. Treatment of these diradicaloids with HSn(-Bu) induces hydrogenation at the -carbon in the five-membered rings, while treatment with 2,2'-azobis(isobutyronitrile) (AIBN) induces substitution at the carbon atoms in the peripheral six-membered rings. We have also developed one-pot substitution/hydrogenation reactions of DFTh/DFFu with various azo-based radical initiators and HSn(-Bu).

Selective methane oxidation by molecular iron catalysts in aqueous medium.

Using natural gas as chemical feedstock requires efficient oxidation of the constituent alkanes-and primarily methane. The current industrial process uses steam reforming at high temperatures and pressures to generate a gas mixture that is then further converted into products such as methanol. Molecular Pt catalysts have also been used to convert methane to methanol, but their selectivity is generally low owing to overoxidation-the initial oxidation products tend to be easier to oxidize than methane itself.