Density Functional Theory Quantum Research Articles

A molecular insight into the development of sensitive glucometers along with DFT investigation of glucose adsorption by a beryllium oxide particle

A molecular insight into the sensitive glucometers along with examining the adsorption of glucose (GLU) with the assistance of a representative beryllium-oxide (BeO)-particle (BOP) was provided in this work. Quantum density functional theory (DFT) calculations were performed for optimizing the models and obtaining their required information. The results indicated the possibility of formations of six interacting configurations of GLU@BOP complexes, I - VI, with the existence of H⋯O and O⋯Be interactions from GLU to BOP, with a detected mode of non-classical hydrogen bond in two of the complexes. The results of interaction strengths and frontier molecular orbitals variations indicated possibilities of formations of reasonable complexes. The existence of non-covalent physical interactions helped approach a recovery time for employing the BOP in a re-adsorption process besides indicating different conductance levels. Consequently, the models of GLU@BOP complexes were found suitable for working in a sensitive adoption of GLU for developing sensitive glucometers.

High-Pressure Phases of Boron Pnictides BX (X = As, Sb, Bi) with Quartz Topology from First Principles

The superdense hexagonal boron pnictides BX (X = As, Sb, Bi), whose structures are formed by distorted tetrahedra and characterized by a quartz-derived (qtz) topology, have been predicted from first principles as potential high-pressure phases. From full geometry structure relaxation and ground state energy calculations based on quantum density functional theory (DFT), qtz BX was found to be mechanically (elastic constants) and dynamically (phonons) stable. From the energy–volume equations of state, at high but experimentally accessible pressures, qtz boron pnictides were found to be more energetically favorable than corresponding cubic zinc–blende phases with diamond-like (dia) topology. According to the electronic band structures, the zinc–blende BX have larger band gaps than the qtz phases, which can be attributed to the higher covalence of the latter. A metallic behavior is only observed for qtz BBi, which is related to the dynamic instability as it follows from the phonon band structure.

Carbon Nanohoops: Multiple Molecular Templates for Exploring Spectroscopic, Electronic, and Thermoelectric Properties.

A combination of density functional theory (DFT) methods and quantum transport theory (QTT) has been used to investigate the spectroscopic, electronic, and thermoelectric properties of carbon nanohoop molecules with different molecular templates. The connectivity type, along with inherent strain, impacts the transport behavior and creates a destructive quantum interference (DQI), which proves itself to be a powerful strategy to enhance the thermoelectric properties of these molecules, making them promising candidates for thermoelectric applications.

Revisiting Dynamic Processes and Relaxation Mechanisms in a Heterocyclic Glass-Former: Direct Observation of a Transient State.

Despite decades of studies, a clear understanding of near-Tg phenomena remains challenging for glass-forming systems. This review delves into the intricate molecular dynamics of the small, heterocyclic thioether, 6-methyl-2,3-dihydro-1,4-benzodithiine (MeBzS2), with a particular focus on its near-Tg cold crystallization and relaxation mechanisms. Investigating isothermal crystallization kinetics at various temperatures reveals a significant interplay between its molecular dynamics and recrystallization from a supercooled liquid. We also identify two independent interconversion paths between energetically privileged conformers, characterized by strained transition states. We demonstrate that these spatial transformations induce substantial alterations in the dipole moment orientation and magnitude. Our investigation also extends to the complex salt PdCl2(MeBzS2), where we observe the transient conformers directly, revealing a direct relationship between their abundance and the local or macroscopic electric field. The initially energetically privileged isomers in an undisturbed system become less favored in the presence of an external electric field or ions, resulting even in an unexpected inversion of states. Consequently, we confirm the intramolecular character of secondary relaxation in MeBzS2 and its mechanism related to conformational changes within the heterocyclic ring. The research is based on the combination of broadband dielectric spectroscopy, X-ray diffraction, and quantum density functional theory calculations.

Atomic ordered doping leads to enhanced sensitivity of phosgene gas detection in graphene nanoribbon: a quantum DFT approach

We explore a novel sensor for detection of phosgene gas by graphene derivatives such as pristine and doped graphene nanoribbons via first principles calculations. The interaction of phosgene molecule with various edge and center doped configurations of boron, phosphorus and boron-phosphorus co-doped armchair graphene nanoribbon (AGNR) and zigzag graphene nanoribbon (ZGNR) is investigated through density functional theory (DFT). P-doped systems showcase chemisorption, displaying enhanced sensitivity to phosgene detection as reflected by a more negative adsorption energy values, accompanied by a prominent charge transfer due to the doping. Regardless of nanoribbon geometry, the binding energies of P-doped systems exhibit notable uniformity within the range of −8.01 eV to −8.49 eV, however the adsorption energies in ZGNR are significantly lower than those observed in AGNR. Due to much higher(lower) electron-donating (accepting) capacity of phosphorous(boron) atoms in comparison to ‘C’ atom, substitutional doping with ‘P’ or ‘B’ atoms in AGNR has signifiant impact on the structural, electronic and adsorption properties of the nanoribbons. We observe that phosphorus doped configurations (edge/center) effectively interact with phosgene molecule with higher adsorption that corresponds to the chemisorption phenomenon. The strongest adsorption energy (−8.83 eV) is obtained for P doped configurations, followed by that for B+P co-doped AGNR (−4.23 eV). These results suggest significantly stronger adsorption of phosgene gas on P doped AGNR than on any other systems reported so far. Band structure analysis estimates that by phosphorus doping, changes in the band gap is significant and it also shows prominent changes in the band structures. Isosurface electronic charge density plots identify that the transfer of charge takes place from graphene system to phosgene molecule. Thus, significant variation in adsorption and electronic properties of P doped AGNR reveal that these geometries immensely promote the detection of phosgene gas, and may be considered as promising chemical sensor for phosgene removal.

Monophasic coamorphous sulpiride: a leap in physicochemical attributes and dual inhibition of GlyT1 and P-glycoprotein, supported by experimental and computational insights

Study aimed to design and development of a supramolecular formulation of sulpiride (SUL) to enhance its solubility, dissolution and permeability by targeting a novel GlyT1 inhibition mechanism. SUL is commonly used to treat gastric and duodenal ulcers, migraine, anti-emetic, anti-depressive and anti-dyspeptic conditions. Additionally, Naringin (NARI) was incorporated as a co-former to enhance the drug’s intestinal permeability by targeting P-glycoprotein (P-gp) efflux inhibition. NARI, a flavonoid has diverse biological activities, including anti-apoptotic, anti-oxidant, and anti-inflammatory properties. This study aims to design and develop a supramolecular formulation of SUL with NARI to enhance its solubility, dissolution, and permeability by targeting a novel GlyT1 inhibition mechanism, extensive experimental characterization was performed using solid-state experimental techniques in conjunction with a computational approach. This approach included quantum mechanics-based molecular dynamics (MD) simulation and density functional theory (DFT) studies to investigate intermolecular interactions, phase transformation and various electronic structure-based properties. The findings of the miscibility study, radial distribution function (RDF) analysis, quantitative simulations of hydrogen/π–π bond interactions and geometry optimization aided in comprehending the coamorphization aspects of SUL-NARI Supramolecular systems. Molecular docking and MD simulation were performed for detailed binding affinity assessment and target validation. The solubility, dissolution and ex-vivo permeability studies demonstrated significant improvements with 31.88-fold, 9.13-fold and 1.83-fold increments, respectively. Furthermore, biological assessments revealed superior neuroprotective effects in the SUL-NARI coamorphous system compared to pure SUL. In conclusion, this study highlights the advantages of a drug-nutraceutical supramolecular formulation for improving the solubility and permeability of SUL, targeting novel schizophrenia treatment approaches through combined computational and experimental analyses. Communicated by Ramaswamy H. Sarma

Theoretical investigations on electronic structure and optoelectronic properties of vinyl fused monomeric and oligomeric benzimidazole derivatives using DFT and TDDFT techniques.

The present work encompasses the theoretical investigation of 14 benzimidazole-based (seven vinyl fused monomeric benzimidazole (VFMBI) and seven vinyl fused oligomeric benzimidazole (VFOBI)) derivatives using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) techniques. The effects of electron donor and acceptor groups on the electronic structure such as HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energies, HOMO-LUMO energy gap, ionization potentials (IPs), electron affinities (EAs), internal reorganization energies of holes and electrons (λh/e), and excited state properties have been explored in the present work. In addition, natural bond orbital (NBO) analysis of these compounds has been investigated to reveal the typical stabilization interactions in these molecules. Hence, the aim of the present work is to explore the electronic structures and optoelectronic properties of the title molecules on the basis of the DFT quantum chemical calculations and to make an idea on the parameters influencing the optoelectronic efficiency toward a better understanding of the structure-property relationships. Moreover, the calculated results reveal the suitable optoelectronic properties of benzimidazole oligomer derivatives using theoretical techniques. Of the investigated molecules, 4_MABIMCY and 4_MABIOCY show potential optoelectronic properties and can be used as a potential charge transport material due to their narrow band gap, high hyperpolarizability, low ionization potential, and high electron affinity. The larger λab and λem values favor the system to be used as a potential optoelectronic material with better optical properties. All quantum chemical calculations were carried out using Gaussian09 theoretical chemistry code. Ground state calculations were made using the B3LYP/6-31+G(d,p) method. All excited state calculations had been computed using TDB3P86/6-311++(d,p). The initial structure for excited state calculations was optimized using the AM1 semi-empirical method.

Preparation and characterization of activated carbon from pine bark biomass for malachite green removal

ABSTRACT Using agricultural waste to prepare biomass materials to remove pollutants has become a research hotspot with the rise of the circular economy. This paper focused on the removal of Malachite Green (MG) as a cationic dye from an aqueous solution using adsorbents (ACBP1 and ACBP2) chemically activated from pine bark (PB) and phosphoric acid (H3PO4) as activated agent. Samples Characterisation was carried out by X-ray diffraction (XRD), Scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS), Fourier transform infrared spectroscopy (FTIR) and Zeta potential measurement. The MG adsorption study was carried out under the variation of several parameters such as pH, adsorbent dosage, contact time and medium temperature. The adsorption experimental capabilities of ACPB1 and ACPB2 for MG dye were 150.18 and 148.16 mg/g, respectively. The data fit the nonlinear equation of the Pseudo-first-order kinetic model for the two adsorbents ACBP1 and ACBP2 with correlation coefficients of 0.998 and 0.997, respectively, indicating that chemisorption controls adsorption. Temperature was found to have a slight impact on adsorption performance, with ACPB1 demonstrating a removal capacity of 184.510 mg/g at 25°C to 186.670 mg/g at 55°C. In addition, a theoretical study was performed using the Density Functional Theory (DFT) quantum calculation method to examine the interactions of reactive sites of the best adsorbent ACPB1 and the cationic dye MG. The theoretical results revealed that the – OH and – COOH groups of ACPB1 were involved in adsorption. The comparative investigation between the experimental and the theoretical results concluded that the ACPB1 adsorbent has a potential removal against the cationic MG dye.

Nucleation mechanism of gas-phase InGaN nanoparticles

The nucleation mechanism of nanoparticles during the growth of InGaN by metal–organic chemical vapor deposition was investigated using density functional theory quantum chemical calculations to explore molecules that are most likely to become the cores of nanoparticles. On the basis of previous research on the nucleation mechanism of nanoparticles in the III-V system, several possible nucleation pathways are proposed for gas-phase InGaN nanoparticles, focusing on the cross-reaction between In and Ga. The possibility of forming different cross-reaction products is also discussed. Among the several reaction pathways examined, the possibilities of generating several cross-reaction products with similar configurations (i.e., [MMGaNHDMInNH2]2 and [MMInNHDMGaNH2]2, [MMGaNHDMInNH2]3 and [MMInNHDMGaNH2]3) were similar; the self-polymerization of [MMXNH]n was most likely to occur, and [MMInNH]4 and [MMInNH]6 were most likely to become the core of nanoparticles.

Photolytic splitting of homodimeric quinone-derived oxetanes studied by ultrafast transient absorption spectroscopy and quantum chemistry.

The photoinduced cycloreversion of oxetane derivatives is of considerable biological interest since these compounds are involved in the photochemical formation and repair of the highly mutagenic pyrimidine (6-4) pyrimidone DNA photoproducts ((6-4)PPs). Previous reports have dealt with the photoreactivity of heterodimeric oxetanes composed mainly of benzophenone (BP) and thymine (Thy) or uracil (Ura) derivatives. However, these models are far from the non-isolable Thy〈º〉Thy dimers, which are the real precursors of (6-4)PPs. Thus, we have synthesized two chemically stable homodimeric oxetanes through the Paternò-Büchi reaction between two identical enone units, i.e. 1,4-benzoquinone (BQ) and 1,4-naphthoquinone (NQ), that led to formation of BQ-Ox and NQ-Ox, respectively. Their photoreactivity has been studied by means of steady-state photolysis and transient absorption spectroscopy from the femtosecond to the microsecond time scale. Thus, photolysis of BQ-Ox and NQ-Ox led to formation of the monomeric BQ or NQ, respectively, through ring opening in a "non-adiabatic" process. Accordingly, the transient absorption spectra of the triplet excited quinones (3BQ* and 3NQ*) were not observed as a result of direct photolysis of the quinone-derived oxetanes. In the case of NQ-Ox, a minor signal corresponding to 3NQ* was detected; its formation was ascribed to minor photodegradation of the oxetane during acquisitions of the spectra during the laser experiments. These results are supported by computational analyses based on density functional theory and multiconfigurational quantum chemistry (CASSCF/CASPT2); here, an accessible conical intersection between the ground and excited singlet states has been characterized as the main structure leading to deactivation of excited BQ-Ox or NQ-Ox. This behavior contrasts with those previously observed for heterodimeric thymine-derived oxetanes, where a certain degree of ring opening into the excited triplet state is observed.

Quantum DFT analysis and molecular docking investigation of various potential breast cancer drugs.

Breast cancer is among the deadliest cancers worldwide, highlighting the urgent need for effective treatments. This study employs density functional theory (DFT) and molecular docking analyses to evaluate the anti-cancer efficacy and specificity of drug molecules lapatinib, tucatinib, neratinib, anastrozole, and letrozole. DFT analysis provides comprehensive insights into the structural, electronic, optical, and vibrational properties of these drugs, helping to elucidate their molecular stability and reactivity through global reactivity descriptors. Additionally, molecular docking simulations reveal the binding conformations and interaction profiles of these drugs with key breast cancer targets, underscoring their therapeutic potential. Docking results indicate that lapatinib, tucatinib, and neratinib have high binding affinities for HER2, with lapatinib exhibiting the strongest overall binding, particularly with PDK1 (PDB ID: 1UU7), PAK4 (PDB ID: 2X4Z), GSK3 (PDB ID: 1GNG), and HER2 (PDB ID: 2IOK). The stable hydrogen bonding and other interactions observed with lapatinib support its effectiveness in treating HER2-positive breast cancers, tucatinib's selective HER2 binding reduces off-target effects, while neratinib's irreversible binding provides prolonged inhibition, making it useful for overcoming resistance in HER2-positive cases. In contrast, anastrozole and letrozole show lower binding affinities for HER2 and EGFR due to their simpler structures but are potent aromatase inhibitors, making them effective in treating estrogen receptor-positive (ER-positive) breast cancers. In conclusion, DFT and molecular docking studies affirm the suitability of lapatinib, tucatinib, and neratinib for HER2-positive cancers, while anastrozole and letrozole are effective in ER-positive cancers, emphasizing the role of molecular structure and binding affinity in optimizing cancer treatment strategies.

Multiscale Modeling of Aqueous Electric Double Layers.

From the stability of colloidal suspensions to the charging of electrodes, electric double layers play a pivotal role in aqueous systems. The interactions between interfaces, water molecules, ions and other solutes making up the electrical double layer span length scales from Ångströms to micrometers and are notoriously complex. Therefore, explaining experimental observations in terms of the double layer's molecular structure has been a long-standing challenge in physical chemistry, yet recent advances in simulations techniques and computational power have led to tremendous progress. In particular, the past decades have seen the development of a multiscale theoretical framework based on the combination of quantum density functional theory, force-field based simulations and continuum theory. In this Review, we discuss these theoretical developments and make quantitative comparisons to experimental results from, among other techniques, sum-frequency generation, atomic-force microscopy, and electrokinetics. Starting from the vapor/water interface, we treat a range of qualitatively different types of surfaces, varying from soft to solid, from hydrophilic to hydrophobic, and from charged to uncharged.

Vibrational spectra, molecular level solvent interaction, stabilization, donor- acceptor energies, thermodynamic, non-covalent interaction and electronic behaviors of 6-Methoxyisoquinoline- anti tubercular agent

The present research is a theoretical examination of 6-methoxyisoquinoline implementing Density Functional Theory quantum mechanical approach. Structural optimization was performed to achieve a stable molecular structure with the least amount of energy. Several protic and aprotic solvent interactions were performed using the IEF polarization continuum model to examine the reactivity and stability of the molecules. Molecular interactions with solvents were investigated using UV–Visible, HOMO-LUMO, MEP, NBO, and NLO properties, which shows some changes in the compound activity at solvent phases against gas phase. The molecular interaction of π*C1–N2 to π*C5 - C10 shows the higher stabilizing energy. DMSO solvent exhibits a very low band gap energy, favors the molecule's high stability. Molecular reactivity, interactions, and optical behavior were all readily apparent. The chemical reactivity of the compound was found good in water. The percentage of PED contributions was evaluated for each mode of vibrations using vibrational spectral investigation. Topological surface analysis was used for better understanding of molecular electron density, reactive center, and steric effect. ELF, LOL, and RDG was generated for compounds with different solvents. The distance of transition and the overlapping of electron and hole were calculated using electron hole analysis. Pharmacological assessments include drug likeness, ADME, toxicity, and a pre-ADMET online tool, which supports the biological capability of the compound. Finally, molecular docking with anti-tubercular protein was performed, and a Ramachandran plot of chosen protein was shown to explore stability.

Superdense Hexagonal BP and AlP with Quartz Topology: Crystal Chemistry and DFT Study

The superdense hexagonal phosphides BP and AlP, whose structures are formed by distorted tetrahedra and characterized by quartz-derived (qtz) topology, were predicted from crystal chemistry and first principles as potential high-pressure phases. From full geometry structure relaxations and ground state energy calculations based on quantum density functional theory (DFT), qtz BP and AlP were found to be less cohesive than the corresponding cubic zinc-blende (zb) phases with diamond-like (dia) topology, but were confirmed to be mechanically (elastic constants) and dynamically (phonons) stable. From the energy–volume equations of state, qtz phases were found to be energetically favorable at small volumes (high pressures), with zb-to-qtz transition pressures of 144 GPa for BP and 28 GPa for AlP. According to the electronic band structures and the site projected density of states, both phosphides exhibit larger band gaps of the zinc-blende phases compared to the qtz phases; the smaller values for the latter result from the smaller volumes per formula unit, leading to increased covalence.

Understanding the CO2 capture potential of tetrapropylammonium-based multifunctional deep eutectic solvent via molecular simulation

A multiscale theoretical study on the suitability of the bifunctional hydrophobic Deep Eutectic Solvent based on tetrapropylammonium chloride and acetic acid with ethanolamine is reported. Density Functional Theory quantum calculations along with classical Molecular Dynamics simulations provide a nanoscopic characterization of the properties of the studied sorbent in terms of intermolecular forces and liquid phase structuring and the characterization of the mechanism of CO2 absorption considering gas – liquid phase interfaces for neat CO2 and a realistic flue gas mixture. Results in this paper characterize the evolution of CO2 into liquid phases as well as the changes produced in the fluid upon gas capture through hydrogen bonding, void occupation and molecular clustering. The possible effect of having two different types of functionalities in the sorbent, amine and hydroxyl groups, which may lead to possible chemical and/or physical sorption is analyzed, considering their possible competing in CO2 capture. The reported study provides the first characterization of multifunctional Deep Eutectic Solvents for carbon capture from complex realistic gas mixtures.

Robustness of Trion State in Gated Monolayer MoSe2 under Pressure.

Quasiparticles consisting of correlated electron(s) and hole(s), such as excitons and trions, play important roles in the optical phenomena of van der Waals semiconductors and serve as unique platforms for studies of many-body physics. Herein, we report a gate-tunable exciton-to-trion transition in pressurized monolayer MoSe2, in which the electronic band structures are modulated continuously within a diamond anvil cell. The emission energies of both the exciton and trion undergo large blueshifts over 90 meV with increasing pressure. Surprisingly, the trion binding energy remains constant at 30 meV, regardless of the applied pressure. Combining ab initio density functional theory calculations and quantum Monte Carlo simulations, we find that the remarkable robustness of the trion binding energy originates from the spatially diffused nature of the trion wave function and the weak correlation between its constituent electron-hole pairs. Our findings shed light on the optical properties of correlated excitonic quasiparticles in low-dimensional materials.

Ultrahigh-Density Superhard Hexagonal BN and SiC with Quartz Topology from Crystal Chemistry and First Principles

Based on superdense C6 with a quartz (qtz) topology, new ultrahigh-density hexagonal binary phases, qtz BN and qtz SiC, were identified via full geometry structure relaxations and ground state energies using calculations based on the quantum density functional theory (DFT) with a gradient GGA exchange–correlation XC functional. Like qtz C6, with respect to diamond, the resulting binary qtz BN and qtz SiC were found to be less cohesive than cubic BN and cubic SiC, respectively, but were confirmed to be mechanically (elastic constants) and dynamically (phonon band structures) stable. Higher densities of the new phases correlate with higher hardness values compared to cubic BN and cubic SiC. In contrast to the regular tetrahedra that characterize the cubic BN and SiC phases, the corner-sharing tetrahedra in the new phases are distorted, which accounts for their exceptional density and hardness. All three qtz phases were found to be semiconducting to insulators, with reduced band gaps compared to diamond, cubic BN, and cubic SiC.

Spectral, band gap and DFT studies of novel cobalt (II) complexes of N(4)-cyclohexylthiosemicarbazones: Molecular docking with DNA and SARS-CoV-2 Mpro

The synthesis and characterization of four novel cobalt complexes CoL12 (1), [Co(HL2)L2]Cl (2), CoL22 (3) and [Co(HL2)L2]Br (4) of thiosemicarbazones HL1 and HL2, (where HL1 is 2-benzoylpyridine-N(4)-cyclohexylthiosemicarbazone and HL2 is quinoline-2-carbaldehyde-N(4)-cyclohexylthiosemicarbazone) are reported. The new ligand HL2 was characterized physicochemically and the structure was confirmed by single crystal X-ray diffraction technique. The relevant intermolecular interactions of HL2 were quantified using Hirshfeld surface analysis. The coordination of the Schiff bases to the metal ions were assigned with the help of physicochemical methods, which indicate octahedral geometry for all the complexes. The deprotonated ligands coordinate via pyridinyl nitrogen, azomethine nitrogen and thiolate sulfur atoms in all the complexes. However, the NNS coordination of the neutral thione ligand is also present in the complexes 2 and 4. Furthermore, geometrical optimization and theoretical calculations of the compounds were achieved by density functional theory quantum chemical computational methods. The direct bandgaps of the complexes were calculated experimentally using the Kubelka-Munk model, which shows a range of 1.62–2.09 eV and corroborates with the theoretical studies. In silico molecular docking studies of all the compounds were performed with B-DNA dodecamer and are all indicative of groove mode of binding. All the compounds exhibit strong putative binding potentials toward duplex DNA. Interestingly, the putative binding efficiency of the complexes 1 and 3 with SARS-CoV-2 main protease is also found very higher compared to the repurposed drugs that are specifically active at 6Y2F.

Super‐hard hybrid ene‐C5, yne‐C6, and ene‐yne‐C7 allotropes from crystal engineering and first principles

AbstractBased on tetrahedral lonsdaleite‐like C4 inserted with C(sp2), C(sp1) and both C(sp2)−C(sp1) ultrahard hybrid allotropes ene‐C5, yne‐C6, and ene‐yne‐C7 were generated and identified from quantum density functional theory DFT calculations of ground states. The crystal density and the cohesive energy were found to decrease along the series C4−C5−C6−C7 from the larger openness of the structures due to C insertions; such feature led to decrease the hardness throughout the series. The novel hybrid allotropes were found stable mechanically (elastic constants and their combinations) and dynamically (phonons band structures). From the electronic band structures, the inserted carbons were found to add up rigidly to the diamond‐like bands of C4 while being characterized by small band gap semi‐conductor to metallic‐like behavior. Modified diamonds such as the simple models herein considered exist (ex. nano‐diamond) and their investigations are of growing interest in materials sciences communities with applications as in electrochemistry.

Computational Exploration of the Thermal Rearrangement of Basketene: One Forbidden versus Two Allowed Pericyclic Reactions.

The thermal rearrangement of basketene to Nenitzescu's hydrocarbon has been explored using density functional theory (M06-2X and ωB97X-D) and DLPNO-CCSD(T) quantum mechanics. Both the sequential thermally allowed retro Diels-Alder followed by Cope rearrangement and the thermally forbidden retro-[2 + 2] cycloaddition were studied. The controlling role of orbital symmetry rather than reaction thermodynamics is demonstrated.