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Density functional theory calculations have been performed to probe the reaction mechanism of the recently reported twofold C−H annulation of arylformamides with alkynes by Ni−Al bimetallic catalysis. The main pathway consisted of the formyl C−H activation, phenyl C−H activation, migratory insertion, and reductive elimination steps in succession. The desired annulation product was found to be the equilibrium‐controlled product, while the minor hydrocarbamoylation product was the kinetics‐controlled product. Calculated free‐energy profiles indicated that the annulation and hydrocarbamoylation pathways could intersect with each other and merge into a mechanism unity, in which the reaction system entered the hydrocarbamoylation pathway in early stage and switched to the annulation pathway afterwards via suitable transition states. The modified mechanism picture demonstrated the phenyl C−H activation step to be the rate‐determining step with a free‐energy barrier of 27.7 kcal/mol. However, this barrier was only 19.4 kcal/mol on the basis of a single annulation pathway, which could not satisfactorily agree with the experimental conditions and kinetic isotope effects. In addition, the crucial role of the bifunctional secondary phosphine oxide ligand in promoting the reactivity and selectivity was elucidated in detail. [ABSTRACT FROM AUTHOR]

N,O‐bidentate BF2 complexes with five‐ and six‐membered core rings have been thoroughly investigated. However, the development of seven‐membered N,O‐boron complexes is still an area to be explored. We have developed BF3 ⋅ OEt2‐induced self‐condensation and coordination reactions based on a single starting material, which had been elucidated by experiment and calculation. This parent asymmetric core‐expanded borondifluoride‐(Z)‐1,3‐di(1H‐pyrrol‐2‐yl)but‐2‐en‐1‐one (BOPYO) showed reactivity with a wide range of aldehydes, thus providing a series of conjugation BOPYOs. Moreover, a BOPYO derivative with a dimethylamino group was developed as a new NIR dye that responds to acid with favorable photophysical properties based on intramolecular charge transfer effect. [ABSTRACT FROM AUTHOR]

Borondifluoride‐3,3‐dimethyl‐2‐[2‐(2‐pyrrolyl) ethenyl] indole (BOPYIN), a seven‐membered, nonplanar boron complex, features typical photophysical properties, such as relatively large Stokes shift. Herein, a series of BOPYINs are prepared by a two‐step, one‐flask synthesis. Based on the modification position, these derivatives could be divided into three sections, including withdrawing substituted dyes, dyes with donating substitution on the pyrrole unit, and dyes with further π‐enlarged substitution on indole unit. The relationship between diverse modified structures and photophysical properties are systematically discussed by experiments and DFT calculations. This work illustrates that donating‐group modifications on pyrrole and π‐enlargement on the indole unit may promote the red shift of the photophysical spectra synergistically. [ABSTRACT FROM AUTHOR]

The cycloaddition reactions between isatin azomethine imine and in situ generated azaoxyallyl cation were explored by density functional theory calculations to elucidate the competition among different pathways. The [3+2] cycloaddition between azaoxyallyl cation and carbonyl group could proceed via either the N‐alkylated pathway or O‐alkylated pathway, which finally afforded the 4‐oxazolidinone or imidate skeleton, respectively. The exclusive formation of the 4‐oxazolidinone product should result from the higher stability and feasible conversion. The possibly competing [3+3] reaction between azaoxyallyl cation and azomethine imine was predicted to be less favorable kinetically than the [3+2] one. Lastly, charge and orbital analyses were performed on isatin azomethine imine to explain the observed reactivities. [ABSTRACT FROM AUTHOR]

Density functional calculations were carried out on the mechanism of a palladium‐catalyzed hydroarylation reaction of β,γ‐unsaturated carbonyl compounds with arylboronic acids reported by Engle's group. The proposed reaction pathway consists of several key mechanistic steps, including the chelation of substrate 1 a, transmetalation of organoboron 2 a, migratory insertion, protodepalladation, and dechelation of product 3 a, among which the transmetalation step is rate‐determining with a free‐energy barrier of 27.0 kcal/mol. Experimental researchers proposed that the chelation of Daugulis's 8‐aminoquinoline (AQ) directing group facilitated the desired hydroarylation in a γ‐selective manner. However, the present study revealed that the chelation of AQ indeed retarded the delivery of the aryl group to the double bond and the regioselectivity was not necessarily the result of this group. Indeed, it could effectively prevent the homocoupling of 2 a, because the homocoupling was predicted to be easier than the desired hydroarylation in the absence of AQ. Additionally, some reductive coupling pathways between 1 a and 2 a were designed, and the competition of them was discussed in great detail. Lastly, the extension of this synthetic strategy to other types of alkenes was predicted. [ABSTRACT FROM AUTHOR]

Density functional theory calculations have been performed to probe the detailed mechanisms of Brønsted‐acid‐catalyzed ring‐opening reactions of donor‐acceptor cyclopropanes. The reaction model without consideration of the explicit solvation effect was characterized by a high activation free energy of 29.5 kcal/mol, while inclusion of the explicit solvation effect in calculations lowered the activation free energy to 20.5 kcal/mol, which demonstrated the cooperative role of HOTf and HFIP in facilitating the ring‐opening step. Additionally, we put forward two distinct reaction mechanisms, including the nucleophile‐induced mechanism and the protonation‐induced mechanism, for the ring‐opening step of donor‐acceptor cyclopropanes. Computational results revealed that modulation of the reaction conditions could result in the shift of the reaction mechanisms. [ABSTRACT FROM AUTHOR]

A seriesof meso-ferrocenyl-porphyrin dyads linkedby four different π-conjugated bridging units (directly bound,vinyl, ethynyl, and phenyl) have been synthesized to investigate theinfluence of the conjugated linker on both the electronic and photochemicalproperties of the porphyrin chromophore. The basic structure consistsof 5-(Fc)-15-(4-methylbenzoate)-10,20-diphenylporphyrin zinc(II),where Fc = ferrocene, vinylferrocene, ethynylferrocene, or phenylferrocene.Upon introduction of the various electron-donating ferrocenyl moietiesat the meso-position of the porphyrin ring, Soretand Q-band electronic transitions of the resultant dyads are red-shiftedcompared with those of the nonferrocenyl reference porphyrin system15-(4-methylbenzoate)-10,20-diphenylporphyrin zinc(II). The electronicproperties of these systems have been investigated by electrochemical(cyclic voltammetry) and computational (DFT/TDDFT) methods, whileUV/vis absorption and fluorescence emission spectroscopic analysisis also presented. Collectively, electronic and photophysical analysisindicate a strong electronic communication between the porphyrin macrocycleand directly bound ferrocenyl, vinylferrocenyl, and ethynylferrocenyldyads. The presence of a phenyl spacer acts to inhibit such electroniccommunication due to the orthogonal geometry of the bridging phenylring at the meso-position of the porphyrin macrocycle.In addition to electronic factors, and in particular for the directlybound 5-(ferrocenyl)-15-(4-methylbenzoate)-10,20-diphenylporphyrinzinc(II) dyad, computational analysis suggests that a significantruffling of the porphyrin macrocyle from planarity is required tofacilitate the bulky ferrocene group directly at the meso-position. Of particular note for each of the meso-ferrocenyl-porphyrin dyads is how fluorescence emission derivedfrom the porphyrin S1(π–π*) excitedstate is quantitatively quenched due to photoinduced charge-transferfrom the ferrocene unit onto the excited state porphyrin. Spectroelectrochemicalstudies demonstrate redox off/on switching of the porphyrin fluorescenceemission via ferricenium/ferrocene redox cycling. Interestingly, itwas found that the S0← S1fluorescenceemission is also switched-on following titration with the metal ionsCe(IV), Cu(II), and Fe(III) in acetonitrile. [ABSTRACT FROM AUTHOR]

In this work, Fe2O3@TiO2 nanostructures with staggered band alignment were newly designed by an aerobic oil-phase cyclic magnetic adsorption method. XRD and TEM analyses were performed to verify the uniform deposition of Fe2O3 nanoparticles on the nanotube inner walls of TiO2. The steady-state degradation experiments exhibited that 1FeTi possessed the most superior performance, which might be ascribable to the satisfying dark adsorption capacity, efficient photocatalytic activity, ease of magnetic separation, and economic efficiency. These results indicated that the deposition of Fe2O3 into TiO2 nanotubes significantly enhanced the activity of Fe2O3, which was mainly ascribed to the Fe2O3-induced formation of staggered iron oxides@TiO2 band alignment and thus efficient separation of h+ and e−. Furthermore, the PL intensity and lifetime of the decay curve were considered as key criterions for the activity's evaluation. Finally, the leaching tests and regeneration experiments were also performed, which illustrated the inhibited photodissolution compared with TiO2/Fe3O4 and stable cycling ability, enabling 1FeTi to be a promising magnetic material for photocatalytic water remediation. [ABSTRACT FROM AUTHOR]

N,O-bidentate BF 2 complexes with five- and six-membered core rings have been thoroughly investigated. However, the development of seven-membered N,O-boron complexes is still an area to be explored. We have developed BF 3  ⋅ OEt 2 -induced self-condensation and coordination reactions based on a single starting material, which had been elucidated by experiment and calculation. This parent asymmetric core-expanded borondifluoride-(Z)-1,3-di(1H-pyrrol-2-yl)but-2-en-1-one (BOPYO) showed reactivity with a wide range of aldehydes, thus providing a series of conjugation BOPYOs. Moreover, a BOPYO derivative with a dimethylamino group was developed as a new NIR dye that responds to acid with favorable photophysical properties based on intramolecular charge transfer effect., (© 2022 Wiley-VCH GmbH.)

Sulfolenopyrrole-based normal and N-confused phlorins have been constructed to address the seldom touched phlorin functionalization and simultaneously explore the effect of the pyrrole linkage modes (αα, αβ) on the [4 + 2] cycloaddition reaction. The common sulfolenophlorin 1 contains two sulfolenopyrroles with the same reactivity upon tautomerization and undergoes stepwise [4 + 2]-cycloaddition with fullerene to furnish monoadduct 1-C60 and bisadduct 1-2C60 with a total yield up to 76%. By contrast, the presence of the confused pyrrole in 2 fixes the π-system owing to the low tendency to tautomerize and enables the two sulfolenopyrroles to exhibit in different fashions (i.e., normal NH-type and imino-type). Notably, under milder conditions (120 °C), the monofullerenoadduct 2-C60 forms rapidly and has been isolated from the [4 + 2] cycloaddition reaction of 2 and fullerene as the predominant fraction, accompanied by a trace amount of bisadduct 2-2C60 . Raising the temperature to 140 °C did not improve the yield of 2-2C60 . The structural analysis of 2-C60 indicates the attachment of fullerene at the iminopyrrole part. The high regioselectivity in the [4 + 2] cycloaddition of the imino-type sulfolenopyrrole unit has been rationalized thermodynamically by the DFT calculation on the relative energy of the two diene intermediates.

In this work, Fe 2 O 3 @TiO 2 nanostructures with staggered band alignment were newly designed by an aerobic oil-phase cyclic magnetic adsorption method. XRD and TEM analyses were performed to verify the uniform deposition of Fe 2 O 3 nanoparticles on the nanotube inner walls of TiO 2 . The steady-state degradation experiments exhibited that 1FeTi possessed the most superior performance, which might be ascribable to the satisfying dark adsorption capacity, efficient photocatalytic activity, ease of magnetic separation, and economic efficiency. These results indicated that the deposition of Fe 2 O 3 into TiO 2 nanotubes significantly enhanced the activity of Fe 2 O 3 , which was mainly ascribed to the Fe 2 O 3 -induced formation of staggered iron oxides@TiO 2 band alignment and thus efficient separation of h + and e - . Furthermore, the PL intensity and lifetime of the decay curve were considered as key criterions for the activity's evaluation. Finally, the leaching tests and regeneration experiments were also performed, which illustrated the inhibited photodissolution compared with TiO 2 /Fe 3 O 4 and stable cycling ability, enabling 1FeTi to be a promising magnetic material for photocatalytic water remediation.