La@C60: A metallic endohedral fullerene

Cl@Si20X20 cages: evaluation of encapsulation nature, structural rigidity, and 29Si-NMR patterns using relativistic DFT calculations

The experimental characterization of Cl@Si₂₀ endohedral clusters, featuring different ligands such as [Cl@Si₂₀H₂₀]^- (1) [Cl@Si₂₀H₁₂Cl₈]^- (2), and [Cl@Si₂₀Cl₂₀]^- (3), provides insight into the variable encapsulation environment for chloride anions. The favorable formation of such species enables the evaluation of the encapsulation nature and the role of the inner anion in the rigidity of the overall cluster. Our results show a sizable interaction which increases as -66.7, -100.8, and -130.3 kcal mol^-1 from 1 to 3, respectively, featuring electrostatic character. The orbital interaction involves 3p-Cl → Si₂₀X₂₀ and 3s-Cl → Si₂₀X₂₀ charge transfer channels and a slight contribution from London dispersion-type interactions. These results show that the inner bonding environment can be modified by the choice of exobonded ligands. Moreover, ²⁹Si-NMR parameters are depicted in terms of the chemical shift anisotropy (CSA), leading to a strong variation of the three principal tensor components (δ₁₁, δ₂₂, δ₃₃), unraveling the origin of the experimental ²⁹Si-NMR chemical shift (δ_iso) differences along the given series. Thus, the Si₂₀ cage is a useful template to further evaluate different environments for encapsulating atomic species.

Water-soluble Self-assembled {Pd84 }Ac Polyoxopalladate Nano-wheel as a Supramolecular Host

Polyoxopalladates (POPs) are a class of self-assembling palladium-oxide clusters that span a variety of sizes, shapes and compositions. The largest of this family, {Pd₈₄ }^Ac , is constructed from 14 building units of {Pd₆ } and lined on the inner and outer torus by 28 acetate ligands. Due to its high water solubility, large hydrophobic cavity and distinct ¹ H NMR fingerprint {Pd₈₄ }^Ac is an ideal molecule for exploring supramolecular behaviour with small organic molecules in aqueous media. Molecular visualisation studies highlighted potential binding sites between {Pd₈₄ }^Ac and these species. Nuclear Magnetic Resonance (NMR) techniques, including ¹ H NMR, ¹ H Diffusion Ordered Spectroscopy (DOSY) and Nuclear Overhauser Spectroscopy (NOESY), were employed to study the supramolecular chemistry of this system. Here, we provide conclusive evidence that {Pd₈₄ }^Ac forms a 1 : 7 host-guest complex with benzyl viologen (BV²⁺ ) in aqueous solution.

Understanding the Nascent Plasmons and Metallic Bonding in Atomically Precise Gold Nanoclusters

The metallic bond is arguably the most intriguing one among the three types of chemical bonds, and the resultant plasmon excitation (e.g. in gold nanoparticles) has garnered wide interest. Recent...

Vibrational spectra of La@C60 and Ce@C60 endohedral fullerenes: Influence of spin state multiplicity

Endohedral fullerenes with paramagnetic encapsulated atoms are new magnetic materials of interest for numerous applications from medicine to quantum computers. An important phenomenon with endohedral fullerenes is the appearance of new vibrational frequencies not associated with empty fullerenes. The vibrational spectra of the lanthanide endohedral fullerenes La@C₆₀ and Ce@C₆₀ in various spin states are calculated using the density functional method. Most of the spectral lines lie in the 300-1600 cm^-1range, and their intensities change dramatically depending on the molecule's symmetry and spin state, which are determined by the encapsulated lanthanide atom. The average frequency shift of the carbon cage vibrations caused by spin transition is only 5 cm^-1. The calculated frequencies of the coupled "metal-carbon cage" vibrations of the lanthanide endohedral fullerenes La@C₆₀ and Ce@C₆₀ in various spin states lie in the 10-170 cm^-1range. The computational results for both the frequencies and intensities of the metal-cage modes depend considerably on the spin state. The changes in these vibrational modes are due to the changes in the molecular symmetry and the metal-carbon bond lengths. Such dependence can be used as a basis for controlling the spin state of metallofullerenes by measuring the vibration frequencies in the far-infrared zone, which could be important for nanoelectronics and quantum informatics.

Stability of Coinage Metals Interacting with C60

Buckminsterfullerene (C₆₀) has been advocated as a perfect candidate material for the encapsulation and adsorption of a variety of metals and the resultant metallofullerenes have been considered for the use in different scientific, technological and medical areas. Using spin-polarized density functional theory together with dispersion correction, we examine the stability and electronic structures of endohedral and exohedral complexes formed between coinage metals (Cu, Ag and Au) and both non-defective and defective C₆₀. Encapsulation is exoergic in both forms of C₆₀ and their encapsulation energies are almost the same. Exohedral adsorption of all three metals is stronger than that of endohedral encapsulation in the non-defective C₆₀. Structures and the stability of atoms interacting with an outer surface of a defective C₆₀ are also discussed. As the atoms are stable both inside and outside the C₆₀, the resultant complexes can be of interest in different scientific and medical fields. Furthermore, all complexes exhibit magnetic moments, inferring that they can be used as spintronic materials.

CdS nanoclusters doped with divalent atoms

ZnS and CdS small nanoclusters have been predicted to trap alkali metals and halogen atoms. However would this kind of nanocompounds be able to encapsulate dianions and dications? This would be very interesting from an experimental point of view, since it would allow the isolation of such divalent ions. Moreover, the resulting endohedral complexes would serve as building blocks for new cluster-assembled materials, with enhanced stability arising from the electrostatic interaction between the incarcerated ions. In this work we have studied the structure and stability of (X@(CdS)i)(±2) with X = Be, Mg, Ca, O, S, Se and i = 9, 12, 15, 16 on the basis of Density Functional Theory and Quantum Molecular Dynamics simulations. Most of the nanoclusters are found to trap both chalcogen and alkaline earth atoms. Furthermore, the chalcogen doped clusters are calculated to be both thermodynamically and thermally stable. However, only a few of alkaline earth metal doped structures are predicted to be thermally stable. Therefore, the charge of the dopant atom appears to be crucial in the endohedral doping. Additionally, the absorption spectra of the title compounds have been simulated by means of Time Dependent Density Functional Theory (TDDFT) calculations. The calculated optical features show a blueshift with respect to the bulk CdS wurtzite. Furthermore, doping modifies notably the optical spectra of nanoclusters, as the absorption spectra shift to lower energies upon encapsulation.