The influence of the configuration of the (C70)2 dimer on its rovibrational spectroscopic properties: a theoretical survey

(Ro)vibrational Spectroscopic Constants, Lifetime and QTAIM Evaluation of Fullerene Dimers Stability

The iconic caged shape of fullerenes gives rise to a series of unique chemical and physical properties; hence a deeper understanding of the attractive and repulsive forces between two buckyballs can bring detrimental information about the structural stability of such complexes, providing significant data applicable for several studies. The potential energy curves for the interaction of multiple van der Waals buckyball complexes with increasing mass were theoretically obtained within the DFT framework at ωB97xD/6-31G(d) compound model. These potential energy curves were employed to estimate the spectroscopic constants and the lifetime of the fullerene complexes with the Discrete Variable Representation and with the Dunham approaches. It was revealed that both methods are compatible in determining the rovibrational structure of the dimers and that they are genuinely stable, i.e., long-lived complexes. To further inquire into the nature of such interaction, Bader's QTAIM approach was applied. QTAIM descriptors indicate that the interactions of these closed-shell systems are dominated by weak van der Waals forces. This non-covalent interaction character was confirmed by the RDG analysis scheme. Indirectly, QTAIM also allowed us to confirm the stability of the non-covalent bonded fullerene dimers. Our lifetime calculations have shown that the studied dimers are stable for more than 1 ps, which increases accordingly with the number of carbon atoms.

Theoretical study of the interaction of fullerenes with the emerging contaminant carbamazepine for detection in aqueous environments

The global increase in drug consumption exposes the growing need to develop new systems for the detection, capture, and treatment of bioactive molecules. Carbamazepine is one instance of such contaminants at the top of the ranking commonly found in sewage treatment systems. This work, therefore, presents a theoretical study of fullerene C₆₀ and its derivatives with substitutional doping with B, Al, Ga, Si, Ge, N and P, for the detection and capture of carbamazepine is aqueous medium. Solvation effects were included by means of the Polarizable Continuum Solvent method. The results indicate that doped fullerenes are sensitive for the detection of carbamazepine both in gaseous and aquatic environments. Investigation on the intermolecular interactions between the drug and the fullerene molecule were carried out, allowing the characterization of the interactions responsible for stabilizing the adsorption of carbamazepine to the fullerenes. The theoretical survey revealed that fullerenes doped with Al, Ga, Si and Ge chemically adsorb carbamazepine whereas for the case of fullerenes doped with other heteroatoms physisorption is responsible for the molecular recognition. Relying on DFT calculations, the fullerene derivatives C₅₉Al, C₅₉Si and C₅₉Ga are the most suitable to act both as a sensor and to uptake carbamazepine in aquatic environments.

Harnessing Greenhouse Gases Absorption by Doped Fullerenes with Externally Oriented Electric Field

In this work, a theoretical investigation of the effects caused by the doping of C₂₀ with silicon (Si) atom as well as the adsorption of CO, CO₂ and N₂ gases to C₂₀ and C₁₉Si fullerenes was carried out. In concordance with previous studies, it was found that the choice of the doping site can control the structural, electronic, and energetic characteristics of the C₁₉Si system. The ability of C₂₀ and C₁₉Si to adsorb CO, CO₂ and N₂ gas molecules was evaluated. In order to modulate the process of adsorption of these chemical species to C₁₉Si, an externally oriented electric field was included in the theoretical calculations. It was observed that C₁₉Si is highly selective with respect to CO adsorption. Upon the increase of the electric field intensity the adsorption energy was magnified correspondingly and that the interaction between CO and C₁₉Si changes in nature from a physical adsorption to a partial covalent character interaction.

Covalently Bonded Fullerene Nano-Aggregates (C60)n: Digitalizing Their Energy–Topology–Symmetry

Fullerene dimers and oligomers are attractive molecular objects with an intermediate position between the molecules and nanostructures. Due to the size, computationally assessing their structures and molecular properties is challenging, as it currently requires high-cost quantum chemical techniques. In this work, we have jointly studied energies, topological (Wiener indices and roundness), and information theoretic (information entropy) descriptors, and have obtained regularities in triad ‘energy–topology–symmetry’. We have found that the topological indices are convenient to indicating the most and least reactive atoms of the fullerene dimer structures, whereas information entropy is more suitable to evaluate odd–even effects on the symmetry of (C60)n. Quantum chemically assessed stabilities of selected C120 structures, as well as linear and zigzag (C60)n, are discussed.

Halogen Interactions in Halogenated Oxindoles: Crystallographic and Computational Investigations of Intermolecular Interactions

X-ray structural determinations and computational studies were used to investigate halogen interactions in two halogenated oxindoles. Comparative analyses of the interaction energy and the interaction properties were carried out for Br···Br, C-H···Br, C-H···O and N-H···O interactions. Employing Møller-Plesset second-order perturbation theory (MP2) and density functional theory (DFT), the basis set superposition error (BSSE) corrected interaction energy (E_int(BSSE)) was determined using a supramolecular approach. The E_int(BSSE) results were compared with interaction energies obtained by Quantum Theory of Atoms in Molecules (QTAIM)-based methods. Reduced Density Gradient (RDG), QTAIM and Natural bond orbital (NBO) calculations provided insight into possible pathways for the intermolecular interactions examined. Comparative analysis employing the electron density at the bond critical points (BCP) and molecular electrostatic potential (MEP) showed that the interaction energies and the relative orientations of the monomers in the dimers may in part be understood in light of charge redistribution in these two compounds.