RESUMO
Ligand shells of gold nanoclusters play important roles in regulating their molecular and electronic structures. However, the similar but distinct impacts of the homologous analogues of the protecting ligands remain elusive. The C2v symmetric monoarsine-protected cluster [Au13(AsPh3)8Cl4]+ (Au13As8) was facilely prepared by direct reduction of (Ph3As)AuCl with NaBH4. This cluster is isostructural with its previously reported stibine analogue [Au13(SbPh3)8Cl4]+ (Au13Sb8), enabling a comparative study between them. Au13As8 exhibits a blue-shifted electronic absorption band, and this is probably related to the stronger π-back donation interactions between the Au13 core and AsPh3 ligands, which destabilize its superatomic 1P and 1D orbitals. In comparison to the thermodynamically less stable Au13Sb8, Au13As8 achieves a better trade-off between catalytic stability and activity, as demonstrated by its excellent catalytic performance towards the aldehyde-alkyne-amine (A3) coupling reaction. Moreover, the ligand exchange reactions between Au13As8 with phosphines, as exemplified by PPh3 and Ph2P(CH2)2PPh2, suggest that Au13As8 may be a good precursor cluster for further cluster preparation through the "cluster-to-cluster" route.
RESUMO
The composition of protection monolayer exerts great influence on the molecular and electronic structures of atomically precise monolayer protected metal nanoclusters. Four isostructural Ag/cyanurate/phosphine metallamacrocyclic monolayer protected Ag22 nanoclusters are synthesized by kinetically controlled in-situ ligand formation-driven strategy. These eight-electron superatomic silver nanoclusters feature an unprecedented interfacial bonding structure with diverse E-Ag (E=O/N/P/Ag) interactions between the Ag13 core and metallamacrocyclic monolayer, and displays thermally activated delayed fluorescence (TADF), benefiting from their distinct donor-acceptor type electronic structures. This work not only unmasks a new core-shell interface involving cyanurate ligand but also underlines the significance of high-electron-affinity N-heterocyclic ligand in synthesizing TADF metal nanoclusters. This is the first mixed valence Ag0/I nanocluster with TADF characteristic.
RESUMO
OBJECTIVE: To establish a rat model of hypophyseal compression and observe and analyze the changes in its biological characteristics after operation. METHODS: The rats were subjected to compression of the pituitary gland by stuffing the autologous muscular tissue into the hypophyseal fossa. The postoperative mortality of the rats was recorded and the volume of the hypophyeseal fossa, body weight, daily food intake, water intake, urine volume and urine specific gravity were measured. RESULTS: Rat models of the hypophyseal compression model were successfully established by this procedure, which resulted in an increase of the volume of hypophyseal fossa by 35%. Rapid body weight loss occurred within 5 weeks after the operation (by as much as 31% on day 10). The rats exhibited recovery of appetite after 2 weeks, but their food intake was still less than that in the control group. Manifestations of central diabetes insipidus occurred gradually, which were especially obvious at 2 weeks and persisted afterwards, and at this time point, significant increment of urine volume (55.4-/+15.9 vs 18.5-/+5.8 ml) and lowered urine gravity (1.011-/+0.004 vs 1.036-/+0.006) were observed. CONCLUSION: Rat models of hypophyseal compression can be established successfully by the described procedure, and the compression results in alteration of the rats' metabolic behaviors, which may differ from the effects of hypophysectomy and damage of pituitary stalk.