Accelerated First-Principles Exploration of Structure and Reactivity in Graphene Oxide.

Graphene oxide (GO) materials are widely studied, and yet their atomic-scale structures remain to be fully understood. Here we show that the chemical and configurational space of GO can be rapidly explored by advanced machine-learning methods, combining on-the-fly acceleration for first-principles molecular dynamics with message-passing neural-network potentials. The first step allows for the rapid sampling of chemical structures with very little prior knowledge required; the second step affords state-of-the-art accuracy and predictive power.

Synergistic Steric and Electronic Effects on the Photoredox Catalysis by a Multivariate Library of Titania Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) that display photoredox activity are attractive materials for sustainable photocatalysis. The ability to tune both their pore sizes and electronic structures based solely on the choice of the building blocks makes them amenable for systematic studies based on physical organic and reticular chemistry principles with high degrees of synthetic control. Here, we present a library of eleven isoreticular and multivariate (MTV) photoredox-active MOFs, UCFMOF-, and UCFMTV--% with a formula TiO[], where the links are linear oligo--arylene dicarboxylates with number of -arylene rings and mol% of multivariate links containing electron-donating groups (EDGs).

Nernstian Li intercalation into few-layer graphene and its use for the determination of K co-intercalation processes.

Alkali ion intercalation is fundamental to battery technologies for a wide spectrum of potential applications that permeate our modern lifestyle, including portable electronics, electric vehicles, and the electric grid. In spite of its importance, the Nernstian nature of the charge transfer process describing lithiation of carbon has not been described previously. Here we use the ultrathin few-layer graphene (FLG) with micron-sized grains as a powerful platform for exploring intercalation and co-intercalation mechanisms of alkali ions with high versatility.

Efficient Iridium Catalysts for Formic Acid Dehydrogenation: Investigating the Electronic Effect on the Elementary β-Hydride Elimination and Hydrogen Formation Steps.

We report herein a series of Cp*Ir complexes containing a rigid 8-aminoquinolinesulfonamide moiety as highly efficient catalysts for the dehydrogenation of formic acid (FA). The complex [Cp*Ir(L)Cl] (HL = -(quinolin-8-yl)benzenesulfonamide) displayed a high turnover frequency (TOF) of 2.97 × 10 h and a good stability (>100 h) at 60 °C.

Impact of Surface Modification on the Lithium, Sodium, and Potassium Intercalation Efficiency and Capacity of Few-Layer Graphene Electrodes.

In a conventional lithium-ion battery (LIB), graphite forms the negative electrode or anode. Although Na is considered one of the most attractive alternatives to Li, achieving reversible Na intercalation within graphitic materials under ambient conditions remains a challenge. More efficient carbonaceous anode materials are desired for developing advanced LIBs and battery technologies.

Gold-Catalyzed Cross-Coupling Reactions: An Overview of Design Strategies, Mechanistic Studies, and Applications.

Transition-metal-catalyzed cross-coupling reactions are central to many organic synthesis methodologies. Traditionally, Pd, Ni, Cu, and Fe catalysts are used to promote these reactions. Recently, many studies have showed that both homogeneous and heterogeneous Au catalysts can be used for activating selective cross-coupling reactions.

Stabilizing polymer electrolytes in high-voltage lithium batteries.

Electrochemical cells that utilize lithium and sodium anodes are under active study for their potential to enable high-energy batteries. Liquid and solid polymer electrolytes based on ether chemistry are among the most promising choices for rechargeable lithium and sodium batteries. However, uncontrolled anionic polymerization of these electrolytes at low anode potentials and oxidative degradation at working potentials of the most interesting cathode chemistries have led to a quite concession in the field that solid-state or flexible batteries based on polymer electrolytes can only be achieved in cells based on low- or moderate-voltage cathodes.

Criticality of Symmetry in Rational Design of Chalcogenide Perovskites.

Chalcogenide perovskites constitute an emerging class of promising photovoltaic materials that are stable and less toxic than popular lead-halide perovskites. Transition-metal and chalcogenide doping are the possible strategies for improving the photovoltaic properties of these materials via the band gap engineering. At the same time, doping can facilitate nonradiative charge-carrier recombination in these materials, adversely affecting their photovoltaic properties.

Direct and Autocatalytic Reductive Elimination from Gold Complexes ([(Ph P)Au(Ar)(CF )(X)], X=F, Cl, Br, I): The Key Role of Halide Ligands.

Kinetic and thermodynamic preferences for the reductive elimination of C -CF , C -X, C -P, and CF -X bonds and competitive phosphine dissociation from a series of Au complexes [(Ph P)Au(Ar)(CF )(X)] (1  ; Ar=4-Me-C H ; X=F, Cl, Br, I) are studied computationally. Kinetically, the most favorable pathways were found to consist of an initial phosphine dissociation from complex 1  , which furnished the respective three-coordinate Au complexes [Au(Ar)(CF )(X)] (2  ). The computed enthalpy barriers for various reductive elimination reactions from complex 2  by a direct (or uncatalyzed) mechanism showed that C -CF bond formation was the most favorable fate for any X group.

Janus all-cis-1,2,3,4,5,6-Hexafluorocyclohexane: A Molecular Motif for Aggregation-Induced Enhanced Polarization.

Recently synthesized all-cis-1,2,3,4,5,6-hexafluorocyclohexane is the least stable among all possible configurational isomers of 1,2,3,4,5,6-hexafluorocyclohexane. This molecule has a remarkably large dipole moment (6.2 D) as well as high facial polarization.

Strain Control: Reversible H2 Activation and H2/D2 Exchange in Pt Complexes.

Experiments have indicated that bulky ligands are required for efficient H2 activation by Pt-Sn complexes. Herein, we unravel the mechanisms for a Pt-Sn complex, Pt(Sn(t)Bu3)2(CN(t)Bu)2 (1a), catalyzed reversible H2 activation. Among a number of Pt-Sn catalysts used to model H2 activation and H2/D2 exchange reactions, only 1a with large strain was found to be suitable because the addition of H2 to 1a requires lowest distortion energy, minimal structural changes, and smallest entropy of activation.

Topochemical Transformations of CaX2 (X=C, Si, Ge) to Form Free-Standing Two-Dimensional Materials.

Topochemical transformations of layered materials CaX2 (X=Si, Ge) are the method of choice for the high-yield synthesis of pristine, defect-free two-dimensional systems silicane and germanane, which have advanced electronic properties. Based on solid-state dispersion-corrected calculations, mechanisms for such transformations are elucidated that provide an in-depth understanding of phase transition in these layered materials. While formation of such layered materials is highly favorable for silicane and germanane, a barrier of 1.

Mechanistic insights into the synergistic catalysis by Au(I), Ga(III), and counterions in the Nakamura reaction.

A computational study based on density functional theory (DFT) establishes the mechanisms for synergistic Au/Ga catalyzed addition of unactivated terminal alkynes to dicarbonyls, the Nakamura reaction. The role played by each of the metal catalysts and the counterion in the reaction has been elucidated. It has been shown that the triazole (TA) ligand could specifically activate the formation of a particular regioisomer through strong non-covalent interactions.

Understanding the mechanisms of unusually fast H-H, C-H, and C-C bond reductive eliminations from gold(III) complexes.

Carbon-carbon bond reductive elimination from gold(III) complexes are known to be very slow and require high temperatures. Recently, Toste and co-workers have demonstrated extremely rapid CC reductive elimination from cis-[AuPPh3 (4-F-C6 H4 )2 Cl] even at low temperatures. We have performed DFT calculations to understand the mechanistic pathway for these novel reductive elimination reactions.

Analyte interactions with a new ditopic dansylamide-nitrobenzoxadiazole dyad: a combined photophysical, NMR, and theoretical (DFT) study.

We report herein the synthesis and photophysical studies on a new multicomponent chemosensor dyad comprising two fluorescing units, dansylamide (DANS) and nitrobenzoxadiazole (NBD). The system has been developed to investigate receptor-analyte binding interactions in the presence of both cations and anions in a single molecular system. A dimethyl amino (in the DANS unit) group is used as a receptor for cations, and acidic hydrogens of sulfonamide and the NBD group are used as receptors for anions.

Color polymorphism: understanding the diverse solid-state packing and color in dimethyl-3,6-dichloro-2,5-dihydroxyterephthalate.

Dimethyl-3,6-dichloro-2,5-dihydroxyterephthalate (MCHT) is known to exist in three differently packed crystals having three different colors, namely yellow (Y), light yellow (LY), and white (W). Apart from the difference in their color, the molecules in the crystals also differ in their intramolecular O-H⋅⋅⋅O and O-H⋅⋅⋅Cl hydrogen bonds. Time-dependent DFT calculations reveal the role of the various types of hydrogen bonds in controlling the color of the polymorphs.

Tip enhanced Raman spectroscopy (TERS) as a probe for the buckling distortion in silicene.

Silicene, the all-Si analogue of graphene, is symmetrically buckled in each of the six-membered units and this buckling is periodically translated across the surface. Raman spectra of silicene clusters were calculated using first principles DFT methods to explore the intrinsic buckling in silicene. The presence of metal clusters as a tip over the silicene units affects the intensity of the buckling modes which can be enhanced by increasing the number of atoms in the clusters.

Pattern formation due to fluorination on graphene fragments: structures, hopping behavior, and magnetic properties.

Structures and mechanism of pattern formation for the radical fluorination on selected polyaromatic hydrocarbons (PAH) has been studied using density functional theory (DFT) methods. Our study reveals that the F(•) radical addition occurs preferentially at the edges of PAHs followed by the hopping of F(•) to the center due to the fluxional nature of C-F bond. F(•) migrates preferentially over the C-C bonds having a lower barrier than that over the aromatic π-cloud in cases of monofluorinated PAHs.

Oxidation reactions of thymol: a pulse radiolysis and theoretical study.

The reactions of (•)OH and O(•-), with thymol, a monoterpene phenol and an antioxidant, were studied by pulse radiolysis technique and DFT calculations at B3LYP/6-31+G(d,p) level of theory. Thymol was found to efficiently scavenge OH radicals (k = 8.1 × 10(9) dm(3) mol(-1) s(-1)) to produce reducing adduct radicals, with an absorption maximum at 330 nm and oxidizing phenoxyl radicals, with absorption maxima at 390 and 410 nm.

Ion interactions with a new ditopic naphthalimide-based receptor: a photophysical, NMR and theoretical (DFT) study.

A new multi-component chemosensor system comprising a naphthalimide moiety as fluorophore is designed and developed to investigate receptor-analyte binding interactions in the presence of metal and non-metal ions. A dimethylamino moiety is utilized as receptor for metal ions and a thiourea receptor, having acidic protons, for binding anions. The system is characterized by conventional analytical methods.

Aminoindolines versus quinolines: mechanistic insights into the reaction between 2-aminobenzaldehydes and terminal alkynes in the presence of metals and secondary amines.

DFT computational studies in the cyclization of aminoalkyne (see structure), which is generated in situ by 2-aminobenzaldehydes and terminal alkynes in the presence of metals and secondary amines, has been investigated. The study revealed that the mode of cyclization (exo vs endo) depends on the protecting group on nitrogen, the oxidation state of copper, and substitution on alkyne.

Molecular Balances Based on Aliphatic CH-π and Lone-Pair-π Interactions.

CH···π and lone-pair···π interactions are estimated for a series of conformationally dynamic bicyclic N-aryliimides. On the basis of their strengths and mutual synergy/competition, the molecules prefer a folded/unfolded conformation. Calculations suggest strategies to selectively isolate the folded form by increasing the strength of the attractive CH···π interaction or removing the lone-pair···π repulsion.