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A thorough DFT investigation of over 800 small fullerenes reveals the ones with promising thermochemical properties for electronics applications.

In the present study, we have investigated the performance of RIJCOSX DLPNO-CCSD(T)-F12 methods for a wide range of systems. Calculations with a high-accuracy option ["DefGrid3 RIJCOSX DLPNO-CCSD(T

Density functional theory (DFT) is currently experiencing a golden age. The past two decades witnessed remarkable advances in the general applicability of density functionals in the top rungs of Jacob’s Ladder. Nevertheless, Jacob’s Ladder may have reached its highest rung in terms of dependencies on occupied (rung four) and unoccupied orbitals (rung five). Moreover, the fifth rung is associated with a computational cost far greater than the lower rungs. Another limitation is that each rung includes dozens of different functionals, and at present, there is no clear pathway for systematic improvements within each rung of the ladder. This highlight provides an overview of the exchange–correlation (XC) hole and how it could be used in developing new density functionals. We begin with a brief overview of the current status and challenges in developing better density functionals, followed by the intimate relationship between the XC functional and hole. We present a conceptually simple and computationally economical method for calculating the XC hole and how this method could offer new directions in developing better exchange–correlation functionals.

Angewandte Chemie / International edition 62(19), e202301301 (2023). doi:10.1002/anie.202301301, Enzymes actuate catalysis through a combination of transition state stabilization and ground state destabilization, inducing enantioselectivity through chiral binding sites. Here, we present a supramolecular model system which employs these basic principles to catalyze the enantiomerization of [5]helicene. Catalysis is hereby mediated not through a network of functional groups but through $\pi-\pi$ catalysis exerted from the curved aromatic framework of a chiral perylene bisimide (PBI) cyclophane offering a binding pocket that is intricately complementary with the enantiomerization transition structure. Although transition state stabilization originates simply from dispersion and electrostatic interactions, enantiomerization kinetics are accelerated by a factor of ca. 700 at 295 K. Comparison with the meso-congener of the catalytically active cyclophane shows that upon configurational inversion in only one PBI moiety the catalytic effect is lost, highlighting the importance of precise transition structure recognition in supramolecular enzyme mimics., Published by Wiley-VCH, Weinheim

Directing groups play an important role in controlling the selectivity of C-H bond activation. Here we demonstrate that for iron, the nature of the directing group (

Metal–ligand cooperation is an important aspect in earth-abundant metal catalysis. Utilizing ligands as electron reservoirs to supplement the redox chemistry of the metal has resulted in many new exciting discoveries. Here, we demonstrate that iron bipyridine-diimine (BDI) complexes exhibit an extensive electron-transfer series that spans a total of five oxidation states, ranging from the trication [Fe(BDI)]3+ to the monoanion [Fe(BDI]−1. Structural characterization by X-ray crystallography revealed the multifaceted redox noninnocence of the BDI ligand, while spectroscopic (e.g., 57Fe Mössbauer and EPR spectroscopy) and computational studies were employed to elucidate the electronic structure of the isolated complexes, which are further discussed in this report., In this study, the multifaceted electrochemistry of a bis(imino)bipyridine iron(II) complex is described. Spectroscopic studies demonstrate that throughout the various reduction processes, the oxidation state on the metal center remains constant (Fe(II); S = 1), whereas the ligand accesses four distinct oxidation states: [BDI]0 ⇄ [BDI]3−. The observed redox noninnocence of the ligand was investigated by computational methods, which is further discussed in this report.

We evaluate the performance of ten common carbon force fields for the interaction energies in double and triple layered carbon onions. In particular, we consider the C20@C60, C20@C80, C20@C180, C80@C240, C60@C240 and C240@C540 double-layer carbon onions and C60@C240@C540 and C80@C240@C540 triple-layered carbon onions. We consider the following carbon force fields: Tersoff, REBO-II, AIREBO, AIREBO-M, screened versions of Tersoff and REBO-II, LCBOP-I, 2015 and 2020 versions of ReaxFF, and the machine-learning GAP force field. We show that the ReaxFF force fields give the best performance for the interaction energies of the cabon onions relative to density functional theory interaction energies obtained at the PBE0-D3/def2-TZVP level of theory. We proceed to use the ReaxFF-15 force field to explore the interaction energies in a giant ten-layered carbon onion with a C60 core and show that the interaction energy between the outer layer and the inner layers increases linearly with the number of layers in the carbon onion (with a squared correlation coefficient of R2 = 0.9996). This linear increase in the stabilization energy with each consecutive layer may have important thermodynamic consequences for describing the formation and growth of large carbon onions.

The S66x8 noncovalent interactions benchmark has been re-evaluated at the "sterling silver" level, using explicitly correlated MP2-F12 near the complete basis set limit, CCSD(F12*)/aug-cc-pVTZ-F12, and a (T) correction from conventional CCSD(T)/sano-V{D,T}Z+ calculations. The revised reference value disagrees by 0.1 kcal/mol RMS with the original Hobza benchmark and its revision by Brauer et al, but by only 0.04 kcal/mol variety from the "bronze" level data in Kesharwani et al., Aust. J. Chem. 71, 238-248 (2018). We then used these to assess the performance of localized-orbital coupled cluster approaches with and without counterpoise corrections, such as PNO-LCCSD(T) as implemented in MOLPRO, DLPNO-CCSD (T1) as implemented in ORCA, and LNO-CCSD(T) as implemented in MRCC, for their respective "Normal", "Tight", and "very Tight" settings. We also considered composite approaches combining different basis sets and cutoffs. Furthermore, in order to isolate basis set convergence from domain truncation error, for the aug-cc-pVTZ basis set we compared PNO, DLPNO, and LNO approaches with canonical CCSD(T). We conclude that LNO-CCSD(T) with veryTight criteria performs very well for "raw" (CP-uncorrected), but struggles to reproduce counterpoise-corrected numbers even for veryVeryTight criteria: this means that accurate results can be obtained using either extrapolation from basis sets large enough to quench basis set superposition error (BSSE) such as aug-cc-pV{Q,5}Z, or using a composite scheme such as Tight{T,Q}+1.11[vvTight(T) - Tight(T)]. In contrast, PNO-LCCSD(T) works best with counterpoise, while performance with and without counterpoise is comparable for DLPNO-CCSD(T1). Among more economical methods, the highest accuracies are seen for dRPA75-D3BJ, {\omega}B97M-V, {\omega}B97M(2), revDSD-PBEP86-D4, and DFT(SAPT) with a TDEXX or ATDEXX kernel., Comment: Final published version with CC license

The computational modeling of fullerenes plays a fundamental role in designing low-dimension carbon nanostructures. Nevertheless, the relative energies of fullerenes larger than C

The relative free energies of the isomers formed upon N-chlorination of each nitrogen atom within the DNA nucleobases (adenine, guanine, and thymine) have been obtained using the high-level G4(MP2) composite ab initio method (the free energies of the N-chlorinated isomers of cytosine have been reported at the same level of theory previously). Having identified the lowest energy N-chlorinated derivatives for each nucleobase, we have computed the free energies associated with chlorine transfer from N-chlorinated nucleobases to other unsubstituted bases. Our results provide quantitative support pertaining to the results of previous experimental studies, which demonstrated that rapid chlorine transfer occurs from N-chlorothymidine to cytidine or adenosine. The results of our calculations in the gas-phase reveal that chlorine transfer from N-chlorothymine to either cytosine, adenine, or guanine proceed via exergonic processes with ΔG o values of −50.3 (cytosine), −28.0 (guanine), and −6.7 (adenine) kJ mol–1. Additionally, we consider the effect of aqueous solvation by augmenting our gas-phase G4(MP2) energies with solvation corrections obtained using the conductor-like polarizable continuum model. In aqueous solution, we obtain the following G4(MP2) free energies associated with chlorine transfer from N-chlorothymine to the three other nucleobases: −58.4 (cytosine), −26.4 (adenine), and −18.7 (guanine) kJ mol–1. Therefore, our calculations, whether in the gas phase or in aqueous solution, clearly indicate that chlorine transfer from any of the N-chlorinated nucleobases to cytosine provides a thermodynamic sink for the active chlorine. This thermodynamic preference for chlorine transfer to cytidine may be particularly deleterious since previous experimental studies have shown that nitrogen-centered radical formation (via N–Cl bond homolysis) is more easily achieved in N-chlorinated cytidine than in other N-chlorinated nucleosides.

We have examined the use of systematic bond-separation reactions and purposely constructed chemistry-preserving isodesmic reactions for the thermochemical calculation of aromatic hydrocarbon species. The bond-separation approach yields somewhat disappointing accuracy even when the reaction energies are obtained with generally robust composite and double-hybrid (DH) density functional theory (DFT) methods. In contrast, for the purposely constructed reactions, we find a dramatic improvement in the accuracy for energies calculated with all methods examined. Notably, for medium-sized aromatic hydrocarbons, we find that an effective approach for formulating a well-balanced reaction is to split the target species into two halves with an aromatic overlapping region. Overall, the G4(MP2)-XK, MPW2PLYP, MN15, PBE, and DC-DFTB3 methods are reasonable within their respective classes of methods for the calculation of bond-separation as well as chemistry-preserving isodesmic reactions. We have further computed per-carbon atomization energy (AE) for a series of D6h benzene-type molecules, and thus obtained a formula for extrapolation to the graphene limit [AEn = 711.5 × (1 − 1/n0.640) kJ mol−1, where n = number of carbons]. It suggests that nano-graphene with a length larger than 10 nm would resemble properties of bulk graphene, and conversely, downsizing a nano-graphene beyond this point may lead to considerably altered properties from the bulk.

Perylene bisimide (PBI) cyclophanes have been shown to form ideal hosts for large aromatic molecules, offering rigid cavities and ideal monomer spacing for π–π stacking interactions between the host and guest. Here, we show computationally that these characteristics also make PBI cyclophanes ideal receptors for the planar transition structures of a number of representative stereoinversion processes. The observed catalytic effect can hereby be explained using two fundamental concepts: transition state stabilization due to shape-complementarity between cyclophane and the transition structures and, to a smaller extent, ground state destabilization due to non-complementarity between cyclophane and equilibrium structures. Energy decomposition analyses of the noncovalent interactions between the host and guest structures reveal that dispersion and electrostatic interactions make the largest contributions to stabilizations and thus suggest that catalysis in this system is mainly driven by π–π stacking interactions.

The 21-homododecahedryl cation is a unique system in terms of its complete fluxionality based on two different rearrangements. In this work, we report the quantum tunneling effects that drive the reactions at temperatures where the semi-classical kinetics are impossible. We postulate that the tunnel effect in this system can serve to create a refrigerator that may operate at arbitrarily low temperatures.

Ethynylcyclopropenylidene (

The isomerisation energies and thermal stabilities of the entire set of C40 fullerene isomers are investigated using molecular dynamics simulations with the recently developed machine-learning-based Gaussian Approximation Potential (GAP-20) force field. Our simulations predict high statistical correlation between the relative isomerisation energy distribution of all C40 isomers and their thermal fragmentation temperatures. The most energetically and thermally stable isomer is the symmetric C40-D2 isomer and its fragmentation temperature is 3875 ± 25 K. In contrast, the least stable isomer is the D5d nanorod-shaped isomer which is 146.8 kcal mol−1 higher in energy and decomposes at 2975 ± 25 K, i.e., around 900 K below the most stable isomer. In addition, we show that most isomers lie in the range between 20 and 60 kcal mol−1 above the most stable isomer, and nearly 60% of isomers decompose in the temperature range of 3425–3675 K. These computational results provide valuable insights into the synthesis of C40 fullerenes at high-temperatures.

The need for sustainable and large-scale energy supply has led to significant development of renewable energy and energy storage technologies. Divalent metal ion (Mg, Ca, and Zn) batteries are promising energy storage technologies for the sustainable energy future, but the need for suitable electrode materials have limited their commercial development. This paper investigates, at the atomic scale, the adsorption and migration of Mg, Ca, and Zn on pristine and defective graphene surfaces, to bring insight into the metal storage and mobility in graphene and carbon-based anodes for divalent metal ion batteries. Such atomistic studies can help address the challenges facing the development of novel divalent metal battery technologies, and to understand the storage differences between divalent and monovalent metal-ion batteries. The adsorption of Ca on the graphene-based system is shown to be more energetically favorable than the adsorption of both Mg and Zn, with Ca showing adsorption behavior similar to the monovalent ions (Li, Na, and K). This was further investigated in terms of metal migration on the graphene surface, with much higher migration energy barriers for Ca than for Mg and Zn on the graphene systems, leading to the trapping of Ca at defect sites to a larger extent.

Gas-sensing properties of nitrogenated holey graphene (C2N), graphdiyne (GDY) and their van der Waals heterostructure (C2N…GDY) have been studied towards particular volatile organic compounds (VOCs) by means of spin-polarized, dispersion-corrected DFT calculations. We find that VOCs such as acetone, ethanol, propanal, and toluene interact weakly with the GDY monolayer; however, the bindings are significantly enhanced with the C2N monolayer and the hybrid C2N…GDY heterostructure in AB stacking. Electron localization function (ELF) analysis shows that all VOCs are van der Waals bound (physical binding) to the 2D materials, which result in significant changes of the charge density of C2N and GDY monolayers and the C2N…GDY heterostructure. These changes alter the electronic properties of C2N and GDY, and the C2N…GDY heterostructure, upon VOC adsorption, which are investigated by density-of-states plots. We further apply thermodynamic analysis to study the sensing characteristics of VOCs under varied conditions of pressure and temperature. Our findings clearly indicate that the C2N…GDY heterostructure is a promising material for sensing of certain VOCs.

Inverse vulcanization provides dynamic and responsive materials made from elemental sulfur and unsaturated cross-linkers. These polymers have been used in a variety of applications such as energy storage, infrared optics, repairable materials, environmental remediation, and precision fertilizers. In spite of these advances, there is a need for methods to recycle and reprocess these polymers. In this study, polymers prepared by inverse vulcanization are shown to undergo reactive compression molding. In this process, the reactive interfaces of sulfur polymers are brought into contact by mechanical compression. Upon heating these molds at relatively low temperatures (≈100 °C), chemical bonding occurs at the polymer interfaces by S-S metathesis. This method of processing is distinct from previous studies on inverse vulcanization because the polymers examined in this study do not form a liquid phase when heated. Neither compression nor heating alone was sufficient to mold these polymers into new architectures, so this is a new concept in the manipulation of sulfur polymers. Additionally, high-level ab initio calculations revealed that the weakest S-S bond in organic polysulfides decreases linearly in strength from a sulfur rank of 2 to 4, but then remains constant at about 100 kJ mol-1 for higher sulfur rank. This is critical information in engineering these polymers for S-S metathesis. Guided by this insight, polymer repair, recycling, and repurposing into new composites was demonstrated.

Two-dimensional nanoporous graphene (NPG) with uniformly distributed nanopores has been synthesized recently and shown remarkable electronic, mechanical, thermal, and optical properties with potent...

Eleven isomers of SiC4H2 lying within 50 kcal mol-1 have been theoretically investigated using density functional theory and high-level coupled-cluster methods. Among them, four isomers, 1-ethynyl-3-silacycloprop-1(2)-en-3-ylidene (1), diethynylsilylidene (2), 1-sila-1,2,3,4-pentatetraenylidene (4), and 1,3-butadiynylsilylidene (5), have already been identified in the laboratory. The current investigation reports three low-lying ( 1 eV) silylidenes [2-sila-(didehydrovinylidene)cyclopropene (8), an isomer with a planar tetracoordinate carbon (ptC) atom (10), and 1-ethynyl-1-silapropadienylidene (11)], which remain elusive in the laboratory to date. Isomer 9 also contains a ptC atom, which turned out to be a transition state at all levels. Though all isomers are polar (μ ≠ 0), rotational spectrum is available only for 4. Using matrix isolation, three isomers (1, 2, and 5) have been trapped in the laboratory at 10 K. Considering the astrochemical relevance of silicon-carbide clusters in the interstellar medium, the current theoretical data demand new molecular spectroscopic studies on SiC4H2. Surprisingly, unlike the isovalent C5H2 isomers, where the bent carbenes are yet to be identified in the laboratory, the bent silylidenes (2 and 5) have been trapped in the case of SiC4H2. In both the cases, molecules with transannular C-C and/or Si-C bonds remain elusive, though they lie in the low-lying region. Using suitable precursors, whether these peculiar geometries (especially 3 and 6) would be identified or not in the laboratory needs to be addressed by molecular spectroscopists. The present investigation documents structural and spectroscopic information of SiC4H2 isomers, which may compliment future molecular spectroscopic observations including radioastronomical searches.

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

Stable equilibrium compounds containing a planar antiaromatic cyclooctatetraene (COT) ring are promising candidates for organic electronic devices such as organic semiconductor transistors. The planarization of COT by incorporation into rigid planar π-systems, as well as by oxidation or reduction has attracted considerable attention in recent years. Using dispersion-corrected density functional theory calculations, we explore an alternative approach of planarizing COT derivatives by adsorption onto graphene. We show that strong π-π stacking interactions between graphene and COT derivatives induce a planar structure with an antiaromatic central COT ring. In addition to being reversible, this strategy provides a novel approach for planarizing COT without the need for incorporation into a rigid structure, atomic substitution, oxidation, or reduction.

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 DLPNObased 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., Computational and Theoretical Chemistry, 1217, art. no. 113874; 2022

Density functional theory (DFT) has been extensively benchmarked for energetic properties; however, less attention has been given to equilibrium structures and the effect of using a certain DFT geometry on subsequent energetic properties. We evaluate the performance of 52 contemporary DFT methods for obtaining the structures of 122 species in the W4-11-GEOM database. This dataset includes a total of 246 unique bonds: 117 H─X, 65 X─Y, 49 X═Y, and 15 XY bonds (where X and Y are first- and second-row atoms) and 133 key bond angles: 96 X-Y-H, 22 X-Y-Z, and 15 H-X-H angles. The reference geometries are optimized at the CCSD(T)/jul-cc-pV(n+d)Z level of theory (n = 5, 6). The performance of DFT is evaluated in conjunction with the Def2-nZVPP (n = T, Q), cc-pV(T+d)Z, and jul-cc-pV(T+d)Z basis sets. The root-mean-square deviations (RMSDs) over the bond distances of the best performing functionals from each rung of Jacob's Ladder are 0.0086 (SOGGA11), 0.0088 (τ-HCTH), 0.0059 (B3LYP), 0.0054 (TPSSh), and 0.0032 (DSD-PBEP86) A. We evaluate the effect of the choice of the DFT geometry on subsequent molecular energies calculated with W1-F12 theory. Geometries obtained with GGA and MGGA methods result in large RMSDs in the subsequent W1-F12 energies; however, six hybrid GGA functionals (B3LYP, B3P86, mPW3PBE, B3PW91, mPW1LYP, and X3LYP) result in an excellent performance with RMSDs between 0.25 and 0.30 kJ mol-1 relative to the CCSD(T)/CBS reference geometries. The B2GP-PLYP and mPW2-PLYP DHDFT methods result in near-CCSD(T) accuracy with RMSDs of 0.11 and 0.10 kJ mol-1 , respectively.

Reactions involving Criegee intermediates (CIs, R1 R2 COO) are important in atmospheric ozonolysis models. In recent years, density functional theory (DFT) and CCSD(T)-based ab initio methods are increasingly being used for modeling reaction profiles involving CIs. We obtain highly accurate CCSDT(Q)/CBS reaction energies and barrier heights for ring-closing reactions involving atmospherically important CIs (R1 /R2 = H, Me, OH, OMe, F, CN, cyclopropene, ethylene, acetaldehyde, and acrolein). We use this benchmark data to evaluate the performance of DFT, double-hybrid DFT (DHDFT), and ab initio methods for the kinetics and thermodynamics of these reactions. We find that reaction energies are more challenging for approximate theoretical procedures than barrier heights. Overall, taking both reaction energies and barrier heights into account, only one of the 58 considered DFT methods (the meta-GGA MN12-L) attains near chemical accuracy, with root-mean-square deviations (RMSDs) of 3.5 (barrier heights) and 4.7 (reaction energies) kJ mol-1 . Therefore, MN12-L is recommended for investigations where CCSD(T)-based methods are not computationally feasible. For reaction barrier heights performance does not strictly follow Jacob's Ladder, for example, DHDFT methods do not perform better than conventional DFT methods. Of the ab initio methods, the cost-effective CCSD(T)/CBS(MP2) approach gives the best performance for both reaction energies and barrier heights, with RMSDs of 1.7 and 1.4 kJ mol-1 , respectively. All the considered Gaussian-n methods show good performance with RMSDs below the threshold of chemical accuracy for both reaction energies and barrier heights, where G4(MP2) shows the best overall performance with RMSDs of 2.9 and 1.5 kJ mol-1 , respectively. © 2019 Wiley Periodicals, Inc.

Inspired by the promise of hydrogen (H2) as a clean alternate to the existing energy sources, we have employed spin-polarized density functional theory calculations on a recently designed two-dimensional C 4 N monolayer as a promising H 2 storage material. By means of first principles DFT calculations, we have comprehensively studied the geometric and electronic properties of pristine, defected and metal-doped C 4 N nanosheets and further explored their H 2 storage properties. We found that light metal dopants such as Li, Na, K, Mg, and Ca bind strongly to defects on a C 4 N nanosheet with binding energies of 3–4 eV per dopant. These binding energies are sufficiently strong to surpass metal clustering. Thermal stability of the metal-doped C 4 N nanosheets has been further verified by means of ab initio molecular dynamics simulations. The bonding nature of the metal dopants with the C 4 N nanosheet has been studied through Bader analysis and Roby-Gould methods and the electronic properties were studied through density of states. We found that each dopant in the metal-doped C 4 N nanosheet can bind up to five H 2 molecules with adsorption energies ranging between 0.15 and 0.60 eV/ H 2 , which results in optimal H 2 storage capacities. Finally, we employed thermodynamic analysis to investigate the H 2 adsorption/desorption mechanism under practical operating conditions.