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A comprehensive DFT investigation has been presented to predict how a carboxylate-rich macrocycle would affect the reactivity of a non-heme Fe(IV)O complex towards C–H activation. The popular non-heme iron oxo complex [FeIV(O)(N4Py)]2+, (N4Py = N,N-(bis(2-pyridyl)methyl)N-bis(2-pyridylmethyl)amine) (1), has been selected here as the primary compound. It is transformed to the compound [FeIV(O)(nBu-P2DA)], where nBu-P2DA = N-(1′,1′-bis(2-pyridyl)pentyl)iminodiacetate (2) after the replacement of two pyridine donors of N4Py with carboxylate groups. Two other complexes, namely 3 and 4, have been predicted sequentially substituting nitrogen with the carboxylate groups. Ethylbenzene and dihydrotoluene were chosen as substrates. In terms of C–H activation reactivity, an interesting pattern emerges: as the carboxylate group becomes more equatorially enriched, the reactivity increases, following the trend 1 < 2 < 3 < 4. This also aligns with available experimental reports related to complexes 1 and 2. Fe(IV)O complexes exhibit two-state reactivity (triplet and quintet), whereas the quintet state is more favourable due to the stabilization of the transition states through exchange interactions involving a greater number of unpaired electrons. A detailed analysis of the factors influencing reactivity has been performed, including distortion energy (which decreases for the transition state with the addition of carboxylate groups), the triplet–quintet oxidant energy gap (which consistently decreases as carboxylate group enrichment increases), steric factors, and quantum mechanical tunneling. This investigation provides a detailed explanation of the observed outcomes and predicts the higher reactivity of carboxylate-enriched Fe(IV)O complexes. After potential experimental verification, this could lead to the development of new, optimal catalysts for C–H activation. [ABSTRACT FROM AUTHOR]

A convenient approach for synthesizing indole‐N‐carboxamide derivatives through palladium‐catalyzed isocyanide insertion into the N−H bond of 3‐(phenylhydrazono)oxindoles has been developed. The inclusion of the 3‐phenylhydrazone group proved essential in remotely activating the N−H bond of the oxindole. Also, it has been established that the reaction outcome is highly dependent on the electronic effects of the substituents. [ABSTRACT FROM AUTHOR]

In this article, we present a meticulous computational study to foresee the effect of an oxygen-rich macrocycle on the reactivity for C–H activation. For this study, a widely studied nonheme Fe(IV)O molecule with a TMC (1,4,8,11-tetramethyl 1,4,8,11-tetraazacyclotetradecane) macrocycle that is equatorially attached to four nitrogen atoms (designated as N4) and acetonitrile as an axial ligand has been taken into account. For the goal of hetero-substitution, step-by-step replacement of the N4 framework with O atoms, i.e., N4, N3O1, N2O2, N1O3, and O4 systems, has been considered, and dihydroanthracene (DHA) has been used as the substrate. In order to neutralise the system and prevent the self-interaction error in DFT, triflate counterions have also been included in the calculations. The study of the energetics of these C–H bond activation reactions and the potential energy surfaces mapped therefore reveal that the initial hydrogen abstraction, which is the rate-determining step, follows the two-state reactivity (TSR) pattern, which means that the originally excited quintet state falls lower in the transition state and the product. The reaction follows the hydrogen atom transfer (HAT) mechanism, as indicated by the spin density studies. The results revealed a fascinating reactivity order, in which the reactivity increases with the enrichment of the oxygen atom in the equatorial position, namely the order follows N4 < N3O1 < N2O2 < N1O3 < O4. The impacts of oxygen substitution on quantum mechanical tunneling and the H/D kinetic isotope effect have also been investigated. When analysing the causes of this reactivity pattern, a number of variables have been identified, including the reactant-like transition structure, spin density distribution, distortion energy, and energies of the electron acceptor orbital, i.e., the energy of the LUMO (σ*z2), which validate the obtained outcome. Our results also show very good agreement with earlier combined experimental and theoretical studies considering TMC and TMCO-type complexes. The DFT predictions reported here will undoubtedly encourage experimental research in this biomimetic field, as they provide an alternative with higher reactivity in which heteroatoms can be substituted for the traditional nitrogen atom. [ABSTRACT FROM AUTHOR]

Aryl carbamates exhibit significant utility due to their diverse range of biological activities, including anticancer, antituberculosis, and antioxidant properties. This study will focus on a comparative evaluation of the antioxidant capabilities of two aryl carbamate derivatives, namely Methyl(Z)-(1-(hydroxyamino) ethyl)-5-(methoxycarbonyl) amino)-2-methyl-1H-indole 1 carboxylate (Compound 1) and Dimethyl (1,3-dioxo-2,3-dihydro-1H-indene-2,2-diyl) bis (4,1 phenylene) dicarbamate (Compound 2). To assess the anti-oxidant capacity, two distinct reactive oxygen species, such as highly reactive hydroxyl (HO·) and moderately reactive hydroperoxyl (HOO·), have been taken into consideration. Four distinct scavenging processes, including RAF, HAT, SETPT, and SPLET, have been investigated here. The RAF mechanism was determined to be the most effective anti-oxidant pathway, regardless of the compounds or free radicals investigated here. For both HO· and HOO·, compound 1 demonstrated more potent scavenging capabilities than compound 2. Compounds 1 and 2 react with the HO· radical very quickly due to its extraordinarily high reactivity; in contrast, the less reactive HOO· provides a rather moderate rate. The calculated values of overall rate constant of Comp. 1 reaction with HOO· are 3.7 × 103 M−1 s−1 (gas phase), 5.3 × 101 M−1 s−1 (water), and 3.6 × 100 M−1 s−1 (pentyl ethanoate). With this context it is clear both of the compounds can work as strong and mild antioxidant against HO· and HOO· radical, respectively. [ABSTRACT FROM AUTHOR]

An unprecedented synthetic approach has been devised to efficiently synthesize regioselective 1,4-disubstituted 1,2,3-triazoles. This technique relies on the use of innovative metal-free highly basic N-heterocyclic imino catalysts. The experimental observations have been supported further by TD-DFT computational studies. [ABSTRACT FROM AUTHOR]