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Angew Chem Int Ed Engl ; 62(29): e202304088, 2023 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-37102264


C60 donor dyads in which the carbon cage is covalently linked to an electron-donating unit have been discussed as one possibility for an electron-transfer system, and it has been shown that spherical [Ge9 ] cluster anions show a close relation to fullerenes with respect to their electronic structure. However, the optical properties of these clusters and of functionalized cluster derivatives are almost unknown. We now report on the synthesis of the intensely red [Ge9 ] cluster linked to an extended π-electron system. [Ge9 {Si(TMS)3 }2 {CH3 C=N}-DAB(II)Dipp ]- (1- ) is formed upon the reaction of [Ge9 {Si(TMS)3 }2 ]2- with bromo-diazaborole DAB(II)Dipp -Br in CH3 CN (TMS=trimethylsilyl; DAB(II)=1,3,2-diazaborole with an unsaturated backbone; Dipp=2,6-di-iso-propylphenyl). Reversible protonation of the imine entity in 1- yields the deep green, zwitterionic cluster [Ge9 {Si(TMS)3 }2 {CH3 C=N(H)}-DAB(II)Dipp ] (1-H) and vice versa. Optical spectroscopy combined with time-dependent density functional theory suggests a charge-transfer excitation between the cluster and the antibonding π* orbital of the imine moiety as the cause of the intense coloration. An absorption maximum of 1-H in the red region of the electromagnetic spectrum and the corresponding lowest-energy excited state at λ=669 nm make the compound an interesting starting point for further investigations targeting the design of photo-active cluster compounds.

Dalton Trans ; 50(39): 13671-13675, 2021 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-34570145


The syntheses and the characterization of two 17-atom endohedral Ge clusters, [Co2@Ge17]6- (1a) and [Ni2@Ge17]4- (2a), are reported. The anions 1a and 2a, which close the gap between the known 16- and 18-atom Ge clusters, are investigated by single crystal X-ray diffraction and by quantum chemical calculations. The structures mark a new example on the pathway for cluster growth towards larger clusters with icosahedral symmetry. Furthermore, the [Co@Ge10]3- anion (3a) is obtained from liquid ammonia.

Talanta ; 225: 122028, 2021 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-33592757


Silver-based nanoparticles (Ag-b-NPs) are currently a cause for concern because they are being produced in increasing quantities for use in industrial goods and consumer products. This goes hand in hand with their release to the environment and the resultant risks for the entire ecosystem. Therefore, it is essential that these materials are monitored. A promising technique that overcomes a number of shortcomings in handling environmental samples is magnetic solid phase extraction (MSPE) of Ag-b-NPs, which is applied in this study. It has been possible to extract different kinds of Ag-b-NPs at environmentally relevant concentrations in the low ng L-1 range using iron oxide magnetic particles (IOMPs) of different size and shape with efficiencies in the range from 80 to 100%. Furthermore, environmentally relevant inorganic ions and TiO2 particles exhibited no major effect on the extraction efficiency. However, natural organic matter (NOM) exhibited a significant influence from 1 mg L-1 resulting in a 50% drop in extraction efficiency. This effect could be overcome by adding 10 mM Ca2+ or increasing the iron oxide magnetic particle (IOMP) concentration to 500 mg L-1. Applying the presented procedure, Ag-b-NPs added to a river water sample at ßAg = 50 ng L-1 were successfully extracted. We also investigated the coextraction of Ag+, demonstrating that NOM could eliminate coextraction. The subsequent species-selective elution of Ag2S-NPs after MSPE, was carried out based on ethylene diamine tetraacetate (EDTA) as eluent in different matrices. A desorption efficiency of 76 ± 6% could be achieved while preserving the Ag2S-NPs' size. By contrast, core Ag-NPs and AgCl-NPs are dissolved if the presented method is followed.