ABSTRACT
Due to the lack of effective synthetic strategies, the preparation of chemically stable chiral Ag(I) cluster-based materials for assembly remains challenging. Here, we have developed an approach to synthesize three pairs of chiral Ln-Ag(I) cluster-based metal-organic frameworks (MOFs) named l-LnAg5-3D (Ln = Gd for 1-L, Eu for 2-L, and Tb for 3-L) and d-LnAg5-3D (Ln = Gd for 1-D, Eu for 2-D, and Tb for 3-D) by employing a chiral Ag(I) cluster ({Ag5S6}) as the node and Ln3+ ion as the inorganic linker. Structural analysis revealed that the chiral ligands induced chirality through the entire structure, resulting in a chiral helix arrangement of the C3-symmetric chiral {Ag5S6} nodes and Ln3+ ions. These compounds showed high solvent stability in various polar organic solvents. The solid-state circular dichroism (CD) spectra of compounds l-LnAg5-3D and d-LnAg5-3D exhibited obvious mirror symmetrical peaks. The emission spectra in the solid state revealed that compound 1-L only exhibited the emission peak of {Ag5S6}, while compounds 2-L and 3-L exhibited overlapping peaks of Ln3+ and {Ag5S6} at different excitation wavelengths. This demonstrates the tunable photoluminescence from {Ag5S6} to Ln3+ by introducing different Ln3+ ions and manipulating the excitation wavelengths. The study underscores the enhanced stability of Ag(I) cluster-based MOFs achieved through the incorporation of Ln3+ ions and establishes chiral Ln-Ag(I) cluster-based MOFs as promising candidates for advanced materials with tunable photoluminescence.
ABSTRACT
Atomically precise metal nanoclusters have received tremendous attention due to their unique structures and properties. Although synthetic approaches to this kind of nanomaterial have been well developed, methods toward precision functionalization of the as-synthesized metal nanoclusters are extremely limited, hindering their interfacial modification and related performance improvement. Herein, an amidation strategy has been developed for the precision functionalization of the Au11 nanocluster based on preorganized nitrogen sites. The nanocluster amidation did not change the number of gold atoms in the Au11 kernel and their bonding mode to the surface ligands but slightly modified the arrangement of gold atoms with the introduction of functionality and chirality, thus representing a relatively mild method for the modification of metal nanoclusters. The stability and oxidation barrier of the Au11 nanocluster are also improved accordingly. The method developed here would be a generalizable strategy for the precision functionalization of metal nanoclusters.
ABSTRACT
Two endophytic strains SS01 and SS02 with the potential for producing steroidal saponins were isolated from the underground stems of Paris polyphylla var. chinensis Franch. The TLC comparison indicated that there are 3 sports with similar R(f) between the metabolites of SS01 and the saponins of Paris polyphylla var. chinensis Franch. And there are 2 sports with similar R(f) between the metabolites of SS02 and the saponins of Paris polyphylla var. chinensis The and that biochemical SS01 Franch. characteristics of morphology, physiological belonged showed to Enterobacteriaceae and SS02 belonged to Bacillus sp.. The 16S rDNA of SS01 and SS02 were PCR and sequenced. The accessions of GenBank are AY842143 and AY842144, respectively. The two 16S rDNA phylogenetic trees were constructed by comparing with the published 16S rDNA sequences of the relative bacteria species. In the first phylogenetic tree SS01 and Cedecea davisae DSM 4568 was the closest relative with 98.9% sequence similarity, and in the second phylogenetic tree SS02 and Paenibacillus daejeonensis was the closest relative with 97.7% sequence similarity. According to the phylogenetic analysis they were identified as Cedecea davisae SS01 and Paenibacillus daejeonensis SS02, respectively.
