Since the synthesis of bullvalene, closed-shell shapeshifting hydrocarbon cages have been extensively studied both experimentally and theoretically. However, considerably less attention has been given to shapeshifting radical hydrocarbon cages. Despite being synthesized over 30 years ago, the shapeshifting barbaralyl radical (CH)₉• has not been studied computationally, and very few experimental studies have been reported. Here, we brush the dust off this shapeshifting radical using the high-level W1-F12 composite ab initio method. We find that consistent with the experimental results, rearrangement of the barbaralyl radical proceeds through a series of β-scission and cyclization steps, which are kinetically favorable over degenerate Cope rearrangements. We proceed to examine these chemical processes in a larger shapeshifting radical cage (CH)₁₁•, which has not been previously investigated. This shapeshifting radical involves a more complex set of rearrangements through β-scissions and cyclizations and is predicted to be less fluxional than the barbaralyl radical.

Influenza A virus (IAV) is reported to develop Pimodivir resistance because of multiple mutations within the Polymerase basic 2 protein (PB2) of IAV. The lack of a high-resolution structure of these PB2 mutants complexed with Pimodivir hinders efforts to understand the drug resistance. Here we decipher the binding differences of Pimodivir in the wild-type and mutant systems Q306H, S324I, S324N, S324R, F404Y, and N510 T of IVA PB2 using homology modelling, molecular dynamics, molecular docking, and density functional theory simulations. The key residues responsible for Pimodivir binding were identified as Glu361, Arg355, Arg332, His357, and Phe323. Those mutations, mainly N510 T, result in significant conformational changes of Pimodivir in the PB2 active site. As a result, the affinity of Pimodivir is significantly reduced in the N510 T system. The mutation effects are less pronounced in the other mutant systems. Dynamic cross-correlation matrix (DCCM) analyses suggest that the singlepoint mutation N510 T produces an allosteric effect on the ligand-binding domain, thus reducing ligand-binding affinity. The present study reveals how a single-point mutation modulates the Pimodivir binding in IAV PB2, which provides important insights into designing new Pimodivir analogues with better binding affinities.

[5.5.5.5]hexaene is a [12]annulene ring with a symmetrically bound carbon atom in its center. This is the smallest hydrocarbon with a hyperbolic paraboloid shape. [5.5.5.5]hexaene and related hydrocarbons are important building blocks in organic and materials chemistry. For example, pentagraphene—a puckered 2D allotrope of carbon—is comprised of similar repeating subunits. Here, we investigate the thermochemical and kinetic properties of [5.5.5.5]hexaene at the CCSD(T) level by means of the G4 thermochemical protocol. We find that this system is energetically stable relative to its isomeric forms. For example, isomers containing a phenyl ring with one or more acetylenic side chains are higher in energy by ∆_H298 = 17.5–51.4 kJ mol⁻¹. [5.5.5.5]hexaene can undergo skeletal inversion via a completely planar transition structure; however, the activation energy for this process is ∆H‡_H298 = 249.2 kJ mol⁻¹ at the G4 level. This demonstrates the high configurational stability of [5.5.5.5]hexaene towards skeletal inversion. [5.5.5.5]hexaene can also undergo a π-bond shift reaction which proceeds via a relatively low-lying transition structure with an activation energy of ∆H‡_H298 = 67.6 kJ mol⁻¹. Therefore, this process is expected to proceed rapidly at room temperature.

The thermal stability of fullerenes plays a fundamental role in their synthesis and in their thermodynamic and kinetic properties. Here, we perform extensive molecular dynamics (MD) simulations using an accurate machine-learning-based Gaussian Approximation Potential (GAP-20) force field to investigate the energetic and thermal properties of the entire set of 1812 C₆₀ isomers. Our MD simulations predict a comprehensive and quantitative correlation between the relative isomerization energy distribution of the C₆₀ isomers and their thermal fragmentation temperatures. We find that the 1812 C₆₀ isomers span over an energetic range of over 400 kcal mol^-1, where the majority of isomers (~85%) lie in the range between 90 and 210 kcal mol^-1 above the most stable C₆₀-I_h buckminsterfullerene. Notably, the MD simulations show a clear statistical correlation between the relative energies of the C₆₀ isomers and their fragmentation temperature. The maximum fragmentation temperature is 4800 K for the C₆₀-I_h isomer and 3700 K for the energetically least stable isomer, where nearly 80% of isomers lie in a temperature window of 4000–4500 K. In addition, an Arrhenius-based approach is used to map the timescale gap between simulation and experiment and establish a connection between the MD simulations and fragmentation temperatures.

The racemization of axially chiral biaryls is a fundamental step toward transforming kinetic resolutions into dynamic kinetic resolutions (DKRs). The high enantiomerization barriers of many biaryl compounds of synthetic relevance, however, may render DKR strategies challenging. Here, we computationally explore the potential of a paraxylene bridged perylene bisimide cyclophane to serve as a conceptually transferrable biaryl enantiomerization catalyst for fundamental biphenyl and binaphthyl scaffolds, as well as the versatile reagent 1,1′-binaphthyl2,2′-diol and a precursor to the heterobiaryl ligand QUINAP. The calculated enantiomerization barriers of the different biaryls decrease by 19.8−73.2% upon complexation, suggesting that the cyclophane may form an effective biaryl racemization catalyst. We find that these observed barrier reductions predominantly originate from a combination of transition structure stabilization through π−π stacking interactions between the shape-complementary transition structures and catalyst, as well as ground-state destabilization of the less complementary reactants, indicating a generalizable strategy toward biaryl racemization catalysis. In exploring all enantiomerization pathways of the biaryls under consideration, we further find a systematic enantiomer- and conformer-dependent chirality transfer from biaryl to cyclophane in host−guest complexes.

The adsorption of aromatic molecules on graphene is essential for many applications. This study addresses the issues associated with predicting accurate binding energies between graphene and benzene using a series of increasingly larger nanographene (C₂₄H₁₂, C₅₄H₁₈, C₉₆H₂₄, C₁₅₀H₃₀, and C₂₁₆H₃₆). For this purpose, we consider several DFT methods developed for accurately predicting noncovalent interactions, namely, PBE0-D4, ωB97X-D4, PW6B95-D4, and MN15. The C₁₅₀H₃₀ and C₂₁₆H₃₆ nanographene predict binding energies converged to sub-kJ mol⁻¹ with respect to the size of the nanographene. For the largest C₂₁₆H₃₆ nanographene, we obtain binding energies of −37.9 (MN15), −39.7 (ωB97X-D4), −40.7 (PW6B95-D4), and −49.1 (PBE0-D4) kJ mol⁻¹. Averaging these values, we obtain ΔE_e,bind = −41.8 ± 8.6 kJ mol⁻¹, which translates to ΔH_0,bind = −41.0 ± 8.6 kJ mol⁻¹. This theoretical binding energy agrees with the experimental value of −48.2 ± 7.7 kJ/mol within overlapping uncertainties.

We evaluate the accuracy of CCSD(T) and density functional theory (DFT) methods for the calculation of equilibrium rotational constants (A_e, B_e, and C_e ) for four experimentally detected low-lying C₅H₂ isomers (ethynylcyclopropenylidene (2), pentatetraenylidene (3), ethynylpropadienylidene (5), and 2-cyclopropen-1-ylidenethenylidene (8)). The calculated rotational constants are compared to semi-experimental rotational constants obtained by converting the vibrationally averaged experimental rotational constants (A₀, B₀, and C₀ ) to equilibrium values by subtracting the vibrational contributions (calculated at the B3LYP/jun-cc-pVTZ level of the theory). The considered isomers are closed-shell carbenes, with cumulene, acetylene, or strained cyclopropene moieties, and are therefore highly challenging from an electronic structure point of view. We consider both frozen-core and all-electron CCSD(T) calculations, as well as a range of DFT methods. We find that calculating the equilibrium rotational constants of these C₅H₂ isomers is a difficult task, even at the CCSD(T) level. For example, at the all-electron CCSD(T)/cc-pwCVTZ level of the theory, we obtain percentage errors ≤ 0.4% (C_e of isomer 3, B_e and C_e of isomer 5, and B_e of isomer 8) and 0.9–1.5% (B_e and C_e of isomer 2, A_e of isomer 5, and C_e of isomer 8), whereas for the A_e rotational constant of isomers 2 and 8 and B_e rotational constant of isomer 3, high percentage errors above 3% are obtained. These results highlight the challenges associated with calculating accurate rotational constants for isomers with highly challenging electronic structures, which is further complicated by the need to convert vibrationally averaged experimental rotational constants to equilibrium values. We use our best CCSD(T) rotational constants (namely, ae-CCSD(T)/cc-pwCVTZ for isomers 2 and 5, and ae-CCSD(T)/cc-pCVQZ for isomers 3 and 8) to evaluate the performance of DFT methods across the rungs of Jacob’s Ladder. We find that the considered pure functionals (BLYP-D3BJ, PBE-D3BJ, and TPSS-D3BJ) perform significantly better than the global and range-separated hybrid functionals. The double-hybrid DSD-PBEP86-D3BJ method shows the best overall performance, with percentage errors below 0.5% in nearly all cases.

Moiré patterns from two-dimensional (2D) graphene heterostructures assembled via van der Waals interactions have sparked considerable interests in physics with the purpose to tailor the electronic properties of graphene. Here we report for the first time the observation of moiré patterns arising from a bilayer graphone/graphene superlattice produced through direct single-sided hydrogenation of a bilayer graphene on substrate. Compared to pristine graphene, the bilayer superlattice exhibits a rippled surface and two types of moiré patterns are observed: triangular and linear moiré patterns with the periodicities of 11 nm and 8-9 nm, respectively. These moiré patterns are revealed from atomic force microscopy and further confirmed by following fast Fourier transform (FFT) analysis. Density functional theory (DFT) calculations are also performed and the optimized lattice constants of bilayer superlattice heterostructure are in line with our experimental analysis. These findings show that well-defined triangular and linear periodic potentials can be introduced into the graphene system through the single-sided hydrogenation and also open a route towards the tailoring of electronic properties of graphene by various moiré potentials.

Composite ab initio methods based on local coupled-cluster approaches calculate the CCSD(T)/CBS energy at a significantly reduced computational cost than the corresponding canonical methods. While showing promising performance for general thermochemistry, local composite ab initio methods have not been tested for fullerenes. Here we examine the performance of several local G4(MP2)-based methods for calculating the relative stability of a diverse set of C₄₀ fullerenes. We use canonical G4(MP2) isomerization energies as reference data. Fullerenes provide a challenging problem for DLPNO-G4(MP2)-based methods. The DLPNO-based methods result in overall root-mean-square deviations (RMSDs) of 28.6 (NormalPNO with CCSD(T₀)), 23.0 (NormalPNO with CCSD(T₁)), and 16.1 (TightPNO with CCSD(T₀)) kJ mol⁻¹. The local natural orbital LNO-G4(MP2) method provides the best overall performance with an RMSD of 4.9 kJ mol⁻¹. The DLPNO-G4(MP2) and LNO-G4(MP2) methods systematically overestimate the canonical G4(MP2) isomerization energies. Therefore, they provide valuable upper limits of the fullerene isomerization energies.

Two-dimensional nanoporous graphene (NPG) with uniformly distributed nanopores has been synthesized recently and shown remarkable electronic, mechanical, thermal, and optical properties with potential applications in several fields. Here, we explore the potential application of NPG as an anode material for Li-, Na-, K-, Mg-, and Ca-ion batteries. We use density functional theory calculations to study structural properties, defect formation energies, metal binding energies, charge analysis, and electronic structures of NPG monolayers. Pristine NPG can bind effectively K⁺ cations but cannot sufficiently bind the other metal cations strongly, which is a prerequisite of an efficient anode material. However, upon substitution with oxygen-rich functional groups (e.g., O, OH, and COOH) and doping with heteroatoms (B, N, P, and S), the metal binding ability of NPG is significantly enhanced. Of the considered systems, the S-doped NPG (S-NPG) binds the metal cations most strongly with binding energies of -3.87 (Li), -3.28 (Na), -3.37 (K), -3.68 (Mg), and -4.97 (Ca) eV, followed by P-NPG, O-NPG, B-NPG, and N-NPG. Of the substituted NPG systems, O-substituted NPG exhibits the strongest metal binding with binding energies of -3.30 (Li), -2.62 (Na), -2.89 (K), -1.67 (Mg), and -3.40 eV (Ca). Bader charge analysis and Roby-Gould bond indices show that a significant amount of charge is transferred from the metal cations to the functionalized NPG monolayers. Electronic properties were studied by density of states plots, and all the systems were found to be metallic upon the introduction of metal cations. These results suggest that functionalized NPG could be used as a global anode material for Li-, Na-, K-, Mg-, and Ca-ion batteries.