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Uncommon structural and bonding properties in Ag₁₆B₄O₁₀.

ABSTRACT: Ag₁₆B₄O₁₀ has been obtained as a coarse crystalline material via hydrothermal synthesis, and was characterized by X-ray single crystal and powder diffraction, conductivity and magnetic susceptibility measurements, as well as by DFT based theoretical analyses. Neither composition nor crystal structure nor valence electron counts can be fully rationalized by applying known bonding schemes. While the rare cage anion (B₄O₁₀)^8- is electron precise, and reflects standard bonding properties, the silver ion substructure necessarily has to accommodate eight excess electrons per formula unit, (Ag⁺)₁₆(B³⁺)₄(O^2-)₁₀ × 8e^-, rendering the compound sub-valent with respect to silver. However, the phenomena commonly associated with sub-valence metal (partial) structures are not perceptible in this case. Experimentally, the compound has been found to be semiconducting and diamagnetic, ruling out the presence of itinerant electrons; hence the excess electrons have to localize pairwise. However, no pairwise contractions of silver atoms are realized in the structure, thus excluding formation of 2e-2c bonds. Rather, cluster-like aggregates of an approximately tetrahedral shape exist where the Ag-Ag separations are significantly smaller than in elemental silver. The number of these subunits per formula is four, thus matching the required number of sites for pairwise nesting of eight excess electrons. This scenario has been corroborated by computational analyses of the densities of states and electron localization function (ELF), which clearly indicate the presence of an attractor within the shrunken tetrahedral voids in the silver substructure. However, one bonding electron pair of s and p type skeleton electrons per cluster unit is extremely low, and the significant propensity to form and the thermal stability of the title compound suggest d¹⁰-d¹⁰ bonding interactions to strengthen the inter-cluster bonding in a synergistic fashion. With the present state of knowledge, such a particular bonding pattern appears to be a singular feature of the oxide chemistry of silver; however, as indicated by analogous findings in related silver oxides, it is evolving as a general one.

SUBMITTER: Kovalevskiy A

PROVIDER: S-EPMC8145714 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundMany reports have also shown that the silver nanoparticles can effectively increase the anticancer drug activity and intensely enhance the drug curative effect. The adsorption of 6MP on nanomaterials has received a lot of attentions because of the drug coordination to its chemotherapeutic activity. The geometrical structures, chemical bonds, molecular orbital properties as well as density of states for the configurations were analyzed to deeply understand the interactions between the 6MP and Ag8 clusters for high effect anticancer drug production.ResultsIn this work, the density functional theory B3LYP has been used to investigate the structures and properties of the configurations between 6-mercaptopurine (6MP) and Ag8 clusters using 6-311++G** level as well as an effective pseudo potential LANL2DZ. The geometries of ten configurations were optimized with full freedom. The geometrical structures, chemical bonds, molecular orbital properties as well as density of states for partial configurations were analyzed based on the density functional calculations. Polarizable continuum solvent model (PCM) in self-consistent reaction field (SCRF) were used for the aqueous calculations. The influences of temperature and pressure on the stability of the predominant configurations in the gas phase were further considered using standard statistical thermodynamic methods from 50 to 500 K and at 1 bar or 100 bar.ConclusionThe result shows that there are ten stable configurations in the gas phase and there is a strong chemical bond between a Ag and S atom in the most stable configuration. The analysis of density of states also shows that the Ag-S chemical bond in the most stable configuration has been formed. Moreover, the results show that the temperature and the pressure will significantly influence the stability of the configurations in the gas phase. Additionally, when the solvent effect was considered, we found that there are only seven stable configurations and the solvent have different effect on various configurations.

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Uncommon structural and bonding properties in Ag₁₆B₄O₁₀.

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