Favorable structures for higher fullerenes

Direct Estimation of Aromatization Energy from 1H NMR and UV-Vis Absorption Data of Homodesmotic Molecules

This study delves into the ring-opening reaction of two distinct diaryl-ring-pyran systems, referred to as drnp1 and drnp2, where the term 'ring' encompasses aromatic, nonaromatic, or antiaromatic motifs. These systems transform into the corresponding cis-ortho quinonoid systems, denoted as c-drnq1 and c-drnq2. Homodesmotic pairs (drnp1, drnp2) and (c-drnq1, c-drnq2) are categorized as (aromatic, nonaromatic), (aromatic, partially aromatic), (antiaromatic, nonaromatic), and (nonaromatic, nonaromatic), with their energy difference representing aromatization energy (Earoma). Using reliable density functional theory, Earoma is assessed for various aromatic and antiaromatic ring motifs, including borderline cases and nonaromatic structures. For example, benzene exhibits an Earoma of 23.4 kcal/mol, indicating 3.9 kcal/mol aromatic stabilization per CC bond, while cyclobutadiene shows -29.9 kcal/mol, indicating a 7.5 kcal/mol destabilization of the CC bond. This approach extends to evaluating global and local aromatic stabilization effects in polycyclic hydrocarbons, nonbenzenoid systems, and heterocyclic compounds. Additionally, variation in 1H NMR chemical shift (δavg) correlates with Earoma, suggesting that a -1.0 ppm shift corresponds to 24.2 kcal/mol aromatization energy. UV-vis absorption maxima difference (Δλavg) correlates linearly with Earoma, enabling direct assessment of aromatization energy from UV-vis spectra using suitable homodesmotic pairs. This comprehensive approach enhances our understanding of structural, energetic, and spectroscopic aspects of aromatic and antiaromatic systems.

Optimizing cell voltage dependence on size of carbon nanotube-based electrodes in Na-ion and K-ion batteries

Sodium-ion batteries (NIBs) and potassium-ion batteries (KIBs) are gaining extensive attention as promising alternatives to lithium-ion batteries owing to their superior energy density and cost-effectiveness. However, the larger ionic radius of Na+ and K+ ions in comparison to Li+ ions poses a challenge in designing anode materials characterized by enduring structures and elevated voltage to facilitate the efficacy of high-performance NIBs and KIBs. Carbon nanomaterials, particularly carbon nanotubes (CNTs), have emerged as a potential candidate in anode materials. Herein, we used density functional theory calculations to study the cell voltage of CNTs in relation to Na-ion and K-ion storage as a function of CNT size. The adsorption energy profiles of both Na+@CNT and K+@CNT systems exhibit a descending trend concomitant with the increase in the CNT diameter, where Na+/K+ ion primarily prefers to adsorb in the interior wall of CNT. Conversely, the cell voltage for the Na and K system gradually increases with the increasing diameter of CNT, which can be attributed to the stronger electrostatic interaction validated by energy decomposition calculation. The voltage of Na-ion adsorbed on the inter wall of (10,10) CNT attains 1.29 V, close to the previously theoretical voltage of Li-ion on the same CNT (1.35 V), while the much lower voltage pertaining to K-ion adsorption on the inter wall of (10,10) CNT just stands at 0.59 V, suggesting the viability of CNT-based electrode for NIBs but not for KIBs. These findings lay a solid foundation for delineating the interrelationship between the voltage properties of CNT as prospective anode material and their structural characteristics, thereby expanding the application of CNT-based optoelectronic devices.

Cyclohexanone-Based Chalcones as Alternatives for Fuel Additives

The use of small molecules, such as chalcones and their derivatives, for more efficient fuels is in increasing demand due to environmental factors. Here, three crystal structures (BH I, II, and III) of cyclohexanone-based chalcones were synthesized and described by single-crystal X-ray diffraction and Hirshfeld surface analysis. The supramolecular modeling analysis on the hyperconjugative interaction energies and QTAIM analysis at the ωB97XD/6-311++G(d,p) level of theory were carried out to analyze the intermolecular interactions in the solid-state. The structure-property relationship, frontier molecular orbital, molecular electrostatic potential, and the experimental calorific value analysis show that the three compounds are a good alternative to be used as an additive for some fuels. Our findings represent a further step forward in the development of cheaper and more efficient fuel additives and pose an opportunity for further investigation on similar analogues.

Extension and Quantification of the Fries Rule and Its Connection to Aromaticity: Large-Scale Validation by Wave-Function-Based Resonance Analysis

The Fries rule is a simple, intuitive tool to predict the most dominant Kekulé structures of polycyclic aromatic hydrocarbons (PAHs), which is valuable for understanding the structure, stability, reactivity, and aromaticity of these conjugated compounds. However, it still remains an empirical hypothesis, with limited qualitative applications. Herein, we verify, generalize, and quantify the Fries rule based on the recently developed resonance analysis of the DFT wave functions of over 1500 PAH and fullerene molecules with over a billion Kekulé structures. The extended rules, counting the numbers of electrons within all rings (not just sextets), are able to rank the relative importance of all Kekulé structures for all considered systems. The statistically meaningful quantification also opens a way to evaluate ring aromaticity based on the resonance theory, which generally agrees well with conventional aromaticity descriptors. Furthermore, we propose a purely graph-based aromaticity indicator nicely applicable to PAHs and fullerenes, with no need of any quantum chemistry calculations, so that it can make valuable predictions for molecular properties that are related to local aromaticity.

Combined spectroscopic and quantum chemical approach to study the effect of hydrogen bonding interactions in ezetimibe

Molecular structure, chemical and physical reactivity, spectroscopic behavior, intermolecular interactions play an important role in understanding the biological nature of pharmaceutical drugs. The objective of the study is to combine the spectroscopic and computational methodology for the investigation of structural behavior of ezetimibe (EZT). Computational study was done on monomeric, dimeric and trimeric models of EZT using B3LYP/6-311G(d,p). Hydrogen bond interactions were taken into consideration to validate the theoretical results with the experimental one. Results obtained for trimeric model were better than monomer and dimer. HOMO-LUMO energy band gap shows that the chemical reactivity calculated using dimeric and trimeric model is higher than that of monomeric model. Higher value of electrophilicity index (ω = 2.5654 eV) also confirms that trimer behaves as a strong electrophile in comparison with monomer and dimer. To examine the hyperconjugation interactions and the stability of the molecule, natural bond analysis (NBO) was done on dimer and trimer of EZT. Nature and the strength of hydrogen bonds were examined by quantum theory of atoms in molecules (QTAIM). Binding energy calculated from counterpoise method was -7.40 kcal/mol for dimer and -21.47 kcal/mol for trimer.

Noble gas dimers confined inside C70

The potential energy surfaces for the interior rotation of a series of pairs of noble gas atoms encapsulated in the C₇₀ cavity have been explored.

Synthesis and spectroscopic characterization on 4-(2,5-di-2-thienyl-1H-pyrrol-1-yl) benzoic acid: A DFT approach

A complete structural and vibrational analysis of the 4-(2,5-di-2-thienyl-1H-pyrrol-1-yl) benzoic acid (TPBA), was carried out by ab initio calculations, at the density functional theory (DFT) method. Molecular geometry, vibrational wavenumbers and gauge including atomic orbital (GIAO) (13)C NMR and (1)H NMR chemical shift values of (TPBA), in the ground state have been calculated by using ab initio density functional theory (DFT/B3LYP) method with 6-311G(d,p) as basis set for the first time. Comparison of the observed fundamental vibrational modes of (TPBA) and calculated results by DFT/B3LYP method indicates that B3LYP level of theory giving yield good results for quantum chemical studies. Vibrational wavenumbers obtained by the DFT/B3LYP method are in good agreement with the experimental data. The study was complemented with a natural bond orbital (NBO) analysis, to evaluate the significance of hyperconjugative interactions and electrostatic effects on such molecular structure. By using TD-DFT method, electronic absorption spectra of the title compound have been predicted and a good agreement with the TD-DFT method and the experimental one is determined. In addition, the molecular electrostatic potential (MEP), frontier molecular orbitals analysis and thermodynamic properties of TPBA were investigated using theoretical calculations.

Designing a C84 fullerene as a specific voltage-gated sodium channel blocker

Fullerene derivatives demonstrate considerable potential for numerous biological applications, such as the effective inhibition of HIV protease. Recently, they were identified for their ability to indiscriminately block biological ion channels. A fullerene derivative which specifically blocks a particular ion channel could lead to a new set of drug leads for the treatment of various ion channel-related diseases. Here, we demonstrate their extraordinary potential by designing a fullerene which mimics some of the functions of μ-conotoxin, a peptide derived from cone snail venom which potently binds to the bacterial voltage-gated sodium channel (NavAb). We show, using molecular dynamics simulations, that the C84 fullerene with six lysine derivatives uniformly attached to its surface is selective to NavAb over a voltage-gated potassium channel (Kv1.3). The side chain of one of the lysine residues protrudes into the selectivity filter of the channel, while the methionine residues located just outside of the channel form hydrophobic contacts with the carbon atoms of the fullerene. The modified C84 fullerene strongly binds to the NavAb channel with an affinity of 46 nM but binds weakly to Kv1.3 with an affinity of 3 mM. This potent blocker of NavAb may serve as a structural template from which potent compounds can be designed for the targeting of mammalian Nav channels. There is a genuine need to target mammalian Nav channels as a form of treatment of various diseases which have been linked to their malfunction, such as epilepsy and chronic pain.

Vibrational spectra, UV-vis spectral analysis and HOMO-LUMO studies of 2,4-dichloro-5-nitropyrimidine and 4-methyl-2-(methylthio)pyrimidine

The FT-IR and FT-Raman vibrational spectra of 2,4-dichloro-5-nitropyrimidine (DCNP) and 4-methyl-2-(methylthio)pyrimidine (MTP) have been recorded in the range 4000-400 and 3600-50 cm(-1), respectively. A detailed vibrational spectral analysis has been carried out and assignments of the observed fundamental bands have been proposed on the basis of peak positions and relative intensities. The optimized molecular geometry and vibrational frequencies in the ground state are calculated using density functional B3LYP method with 6-31+G(d,p) and 6-311++G(d,p) basis set combinations. With the help of specific scaling procedures, the observed vibrational wavenumbers in FT-IR and FT-Raman spectra are analyzed and assigned to different normal modes of the molecules. The predicted first hyperpolarizability reveals that the molecules are an attractive object for future studies of non-linear optical properties. And also HOMO-LUMO energy gap explains the eventual charge transfer interaction taking place within the molecules. UV-vis spectral analysis of the title compounds has been researched by theoretical calculations. The frontier orbital energies, absorption wavelengths (λ), oscillator strengths (f) and excitation energies (E) studied using TD-DFT (B3LYP) with 6-311++G(d,p) basis set are calculated in this work.

Theoretical investigations on the structure, density, thermodynamic and performance properties of amino-, methyl-, nitroso- and nitrotriazolones

We have studied herein the effect of position and the number of -NO, -NO2, -NH2 and -CH3 groups on the structure, stability, impact sensitivity, density, thermodynamic and detonation properties of triazolones by performing density functional theory calculations at the B3LYP/aug-cc-pVDZ level. The optimized structures, vibrational frequencies and thermodynamic values for triazolones have been obtained in their ground state. Kamlet-Jacob equations were used to calculate the detonation velocity and detonation pressure of model compounds. The detonation properties of NNTO (D 8.75 to 9.10 km/s, P 34.0 to 37.57 GPa), DNTO (D 8.80 to 9.05 km/s, P 35.55 to 38.27 GPa), ADNTO (D 9.01 to 9.42 km/s and P 37.81 to 41.10 GPa) and ANNTO (D 8.58 to 9.0 km/s, P 30.81 to 36.25 GPa) are compared with those of 1,3,5-trinitro-1,3,5-triazine (RDX) (D 8.75 km/s, P 34.70 Gpa) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) (D 8.96 km/s, P 35.96 GPa). The designed compounds satisfy the criteria of high energy materials.

Molecular structure and vibrational spectroscopic studies of Chrysin using HF and Density Functional Theory

In the present study, the molecular confirmation, vibrational and electronic transition analysis of 5,7-dihyroxyflavone (Chrysin) were investigated using experimental techniques (FT-IR, FT-Raman and UV) and quantum chemical calculations by HF and DFT/B3LYP method with 6-31G(d,p) as basis set. The FT-IR and FT-Raman spectra in solid phase were recorded in the region 4000-400cm(-1) and 3500-50cm(-1) respectively. The UV absorption spectra of the title compound dissolved in water, methanol and ethanol were recorded in the range of 200-400nm. The complete vibrational assignments were performed on the basis of total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanic (SQM) method. By using TD-DFT calculation, electronic absorption spectra of the title compound have been predicted and a good agreement with experimental one is established. In addition, the molecular electrostatic potential (MEP), natural bond orbital (NBO) analysis have been investigated using theoretical calculations. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule.

Experimental, theoretical calculations of the vibrational spectra and conformational analysis of 2,4-di-tert-butylphenol

In the present work, we reported a combined experimental and theoretical study on conformational stability, molecular structure and vibrational spectra of 2,4-di-tert-butylphenol (2,4-DTBP). The FT-IR (400-4000cm(-1)) and FT-Raman spectra (50-3500cm(-1)) of 2,4-DTBP were recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of 2,4-DTBP in the ground-state have been calculated by using the density functional BLYP/B3LYP methods. The energy calculated by time-dependent density functional theory (TD-DFT) result complements with the experimental findings. The calculated highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies show that charge transfer occurs within the molecule. Finally the calculation results were compared with measured infrared and Raman spectra of the title compound which showed good agreement with observed spectra.

Testing the resistance of fullerenes to chemothermal oxidation used to isolate soots from environmental samples

We tested the resistance of five different fullerenes (C(60), C(70), C(76/78) mix, and C(84)) to chemothermal oxidation at 375 °C (CTO-375), a method that has been used and tested for quantifying black carbon (BC) and CNTs in soils and sediments. C(60) survived CTO-375 the most (50%), while C(70) was the fullerene with the lowest survival rate (<1%). Standard additions of C(60) to soil and sediment reference materials yielded recoveries between 18 and 36%. Although lower than recoveries previously observed for soot and CNTs, these results demonstrate the capability of CTO-375 to partially isolate C(60) from solid environmental matrices. Standard additions of C(70), C(76/78), and C(84) yielded slightly higher survival rates when added to soil and sediment than in their pure form. These results indicate that the mineral matrices of these samples probably had a catalytic effect towards C(60) and a protective effect towards C(70), C(76/78), and C(84) during CTO-375.

Structural and electron properties of the highest epoxygenated fullerene C60O30, a DFT study

Ab initio Hartree-Fock (HF) and density functional theory (DFT) calculations were carried out to determine the structural and electronic properties of the highest epoxygenated fullerenes C(60)O(30). For comparison, other fullerene oxides C(60)O(29), C(60)O(3), C(60)O(2) and C(60)O were also studied. The highly symmetrical I(h) structure of the parent C(60) is reserved in C(60)O(30) and C(60)O(30) was calculated to be a nonpolar molecule. It was demonstrated that C(60)O(30) should be more stable than other C(60) oxides such as C(60)O(29), C(60)O(3), C(60)O(2) and C(60)O. Compared with C(60), it is less possible for C(60)O(30) to accept or donate electrons from the reduced EAs and enhanced IPs. The IR active modes and harmonic vibrational frequencies of C(60)O(30) were also discussed.

Electronic properties of tricoordinated phosphorus in hexagonal phosphininium compounds and molecular aromaticity

Calculations with B3LYP within quantum chemical density functional theory have been carried out for 1-H-phosphininium cation and a series of 1-R-phosphininium molecules (R=cyclopentadiene, alpha and beta pyrroles, alpha and beta phosphole, C5BH5-- and CH2--). The negative nuclear-independent chemical shift values and the positive aromatic stabilization energies confirm that they are aromatic compounds. In particular, the 1-H-phosphininium cation even exhibits stronger aromatic character than the well-known aromatic phosphinine. The aromatic substituents have strong capability to attract electrons. It is the conjugation and aromaticity that keeps the stability and conformations of the molecules investigated. Owing to the perturbation of the aromatic substituted groups, the predicted large T values and the enlarged HOMO-LUMO gap of the phosphininium cation indicate that these compounds are expected in experiment.

Structural and electronic properties of S-doped fullerene C58: Where is the S atom situated?

Structural and electronic properties of S-doped fullerene C58 were calculated systematically via Hartree-Fock self-consistent field (SCF) and density functional B3LYP levels of theory with 6-31G(d) basis set. The most stable C58S represents an open cage structure with a nine-member ring orifice, which provides a large hole for large atoms or small molecules to pass through into the cage. The most stable endohedral S@C58 has the S atom seated near the center of the C58 cage. The calculated highest occupied molecular orbital-lowest unoccupied molecular orbital energy gaps of the isomers lie in the range of 1.42-2.50 eV. The electron affinity and the ionization potential were also presented as an indicator of the kinetic stability. Our results may aid in the design of experimental methods for controlling the nature of fullerene cages (for example, doping, opening, and reclosing them).

Effects of finite carbon nanotube length on sidewall addition of fluorine atom and methylene

Density functional computations (PBE and B3LYP) in conjunction with 3-21G and 6-31G basis sets are used to determine the energy of fluorine atom and CH(2) addition to the sidewall of (5,5) C(30+10)(n)()H(20) (n = 0, 1, 2.18) carbon nanotube slabs. A pronounced oscillation of the addition energy is found for fluorine atom addition, while oscillations are significantly damped for carbene addition due to the insertion into CC bonds. [structure: see text]