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The formation of supramolecular complexes between C60 and a molecular nanographene endowed with both positive and negative curvatures is described. The presence of a corannulene moiety and the saddle shape of the molecular nanographene allows the formation of complexes with 1:1, 1:2, and 2:1 stoichiometries. The association constants for the three possible supramolecular complexes were determined by 1H NMR titration. Furthermore, the stability of the three complexes was calculated by theoretical methods that also predict the photoinduced electron transfer from the curved nanographene to the electron acceptor C60. Time‐resolved transient absorption measurements on the ns‐time scale showed that the addition of C60 to NG‐1 solutions and photo‐exciting them at 460 nm leads to the solvent‐dependent formation of new species, in particular the formation of the one‐electron reduced form of C60 in benzonitrile was observed. [ABSTRACT FROM AUTHOR]

The formation of supramolecular complexes between C60 and a molecular nanographene endowed with both positive and negative curvatures is described. The presence of a corannulene moiety and the saddle shape of the molecular nanographene allows the formation of complexes with 1:1, 1:2, and 2:1 stoichiometries. The association constants for the three possible supramolecular complexes were determined by 1H NMR titration. Furthermore, the stability of the three complexes was calculated by theoretical methods that also predict the photoinduced electron transfer from the curved nanographene to the electron acceptor C60. Time‐resolved transient absorption measurements on the ns‐time scale showed that the addition of C60 to NG‐1 solutions and photo‐exciting them at 460 nm leads to the solvent‐dependent formation of new species, in particular the formation of the one‐electron reduced form of C60 in benzonitrile was observed. [ABSTRACT FROM AUTHOR]

The Diels–Alder cycloaddition reaction between 1,3-cyclohexadiene and a series of C60 fullerenes with encapsulated (super)alkali/(super)halogen species (Li+@C60, Li2F+@C60, Cl−@C60, and LiF2−@C60) was explored by means of DFT calculations. The reactivity of the ion encapsulating systems was compared to that of the parent C60 fullerene. Significant enhancement in reactivity was found for cation-encapsulating Li+/Li2F+@C60 complexes. The cycloadduct formed by LiF2−@C60 was found to be the most thermodynamically favorable among the studied ones. In contrast, encapsulation of Cl− anions disfavors the cycloaddition reaction both kinetically and thermodynamically. Higher activation energy barrier and less stability of the reaction product in the case of Cl−@C60 were associated with the higher deformation energies of the fullerene cage and the lower interaction energy between the reactants in comparison with the other studied complexes. [ABSTRACT FROM AUTHOR]

The cascade cyclization reactions of 1,5‐bisallenes grant access to a great variety of products by precisely tuning the catalyst system and/or the reagents involved. Herein, we present our findings that 1,5‐bisallenes react with two molecules of dimethyl acetylenedicarboxylate to afford, in a completely diastereoselective manner, cis‐3,4‐arylvinyl pyrrolidines and cyclopentanes. DFT calculations have been used to postulate a mechanism for the developed reaction which encompasses a [2+2+2] cycloaddition reaction of the two alkynes and the external double bond of one allene, followed by a cycloisomerization involving the internal double bond of the second allene. [ABSTRACT FROM AUTHOR]

Predictive catalysis must be the tool that does not replace experiments, but acts as a selective agent, so that synthetic strategies of maximum profitability are used in the laboratory in a surgical way. Here, nanotechnology has been used in olefin metathesis from homogeneous Ru‐NHC catalysts, specifically annulating a C60 fullerene to the NHC ligand. Based on results with the C60 in the backbone, a sterile change with respect to the catalysis of the metal center, an attempt has been made to bring C60 closer to the metal, by attaching it to one of the two C−N bonds of the imidazole group of the SIMes (1,3‐bis(2,4,6‐trimethylphenyl)imidazolin‐2‐ylidene) ligand (reference NHC ligand of the 2nd generation Grubbs catalysts) to increase the steric pressure of C60 in the first sphere of reactivity of the metal. The DFT calculated thermodynamics and the kinetics of SIMes‐derived systems show that they are efficient catalysts for olefin metathesis. [ABSTRACT FROM AUTHOR]

3D shape and the resulting physicochemical properties of double‐helical DNA/RNA structures are determined not only by individual nucleobases, but also by their additive intermolecular interactions. Energetic contribution from aromatic π–π stacking to the stabilization of DNA/RNA is not small and sometimes even comparable to that from H‐bonding. The basis of the stacking interactions lies in the π‐electron structure of individual nucleobases, which can be described by various aromaticity indices. Heteroatoms and exocyclic functional groups make the electronic structure of nucleobases different from aromatic hydrocarbons. Consequently, the cyclic π‐electron delocalization is not the only factor responsible for the relative stability of their tautomers. This review puts the spotlight on interplay between aromaticity of purine and pyrimidine nucleobases and their tautomeric preferences, as well as on the effects of different noncovalent interactions (hydrogen bonding, metal ion coordination, and π–π stacking) on π‐electron delocalization of five‐ and six‐membered rings in individual nucleobases and their complexes. This article is categorized under:Structure and Mechanism > Molecular StructuresElectronic Structure Theory > Density Functional Theory [ABSTRACT FROM AUTHOR]

Herein described is a facile preparation protocol by which amino-alcohol derivatives of graphene oxide (GO) can be conveniently synthesized in high yield and short time by an ultrasound treatment of ethanol-graphite-oxide suspensions and amines. Linear primary amines of different chain length rapidly react with graphite oxides prepared from powder and flakes, leading to the formation of GO amino-alcohol derivatives. Characterization of the amine-modified materials by XRD, TGA, FTIR, and Raman spectroscopy demonstrates the proposed derivatization; the findings are corroborated by SEM and TEM observations. Additionally, quantum-chemical investigations shed additional light on the reaction, suggesting an alcohol-accelerated SN2 mechanism where the initial step, the simultaneous formation of a C–N bond (GO-amine) and rupture of an epoxide bond in GO, is rate-determining. Energy barriers lower than 8 kcal/mol are estimated, which can be overcome with the energy supplied by the sonotrode tip (ca. 2 kcal) and the use of ethanol to facilitate it. [ABSTRACT FROM AUTHOR]

A recent paper (Phys. Chem. Chem. Phys. 2020, 22:22,459) shows that the energy components of the extended transition state energy decomposition analysis (ETS-EDA) are path functions, and therefore, they are not uniquely defined. In this work, we apply the ETS-EDA to analyse all possible dissociation paths of the water tetramer to four free water molecules. Our results confirm that the energy components of the ETS-EDA are path functions. However, they also show that differences among energy components obtained for the different paths are relatively small, and therefore, we conclude that the information obtained from an ETS-EDA can be used to discuss the nature of chemical bonds and analyse the origin of isomerization energies and energy barriers. However, if a given process can be attained by means of different and chemically reasonable paths, we recommend to perform the ETS-EDA of a given reaction for all different paths to confirm that energy components of the ETS-EDA do not differ very much from one path to another. [ABSTRACT FROM AUTHOR]