A cluster-based luminescent porous metal-organic framework has been constructed through a "cluster linker" approach. The luminescent gold(I) cluster, prefunctionalized with pyrazinyl groups, was used as a cluster linker, similar to an organic linker, to connect silver ions in order to form a 3D framework. 1D channels with 1.1 nm diameter were observed in the framework. The cluster with its intrinsic luminescence was incorporated into a porous framework to give a luminescent bifunctional NbO net. This MOF shows solvatochromic behavior, and the interactions between solvent molecules and silver ions inside the channels account for the changes in absorption and emission spectra.
An intensely luminescent gold(I)-silver(I) cluster [(C)(AuPPhpy ) Ag (CF CO ) ](BF ) (PPhpy =bis(2-pyridyl)phenylphosphine) (3) is synthesized by the reaction of [(C)(AuPPhpy ) Ag ](BF ) with AgCF CO . All eight faces of the octahedral C@Au core in 3 are capped, that is, six faces are capped by silver ions and two by tetrafluoroborates. Cluster 3 is intensely luminescent in solution with a quantum yield of 92 %. Ligation of CF CO ions is vital for the construction and emission properties of 3, as confirmed by DFT calculations. BF ions are involved in the protecting sphere of the metal core, as evidenced by F NMR data. The participation of phosphines, CF CO , and BF ions in the protection of the emissive core and the enhancement of the rigidity of the cluster result in the high emission efficiency. This is the first example of organic ligands and inorganic anions forming a rigid protecting sphere for luminescent coinage-metal clusters.
Cluster-based functional materials are appealing, because clusters are well-defined building units that can be rationally incorporated for the tuning of structures and properties. Postclustering modification (PCM) allows for tailoring properties through the structural modification of a cluster with preorganized funtional groups. By introducing aldehydes into a robust gold-silver cluster via a protection-deprotection process, we manage to synthesize a new cluster bearing six reactive sites, which are available for PCM through dynamic covalent imine bonds formation with chiral monoamines. Chirality is transferred from the amine to the gold-silver cluster. The homochirality of the resulted cluster has been confirmed by X-ray structural determination and CD spetroscopy. Intense CD signals make it practical for chiral recognition and ee value determination of chiral monoamines. The strategy of prefunctionalizing of cluster and the concept of PCM open a broader prospect for cluster design and applications.
A red-near-IR dual-emissive nanocluster with the composition [Au10 Ag2 (2-py-C≡C)3 (dppy)6 ](BF4 )5 (1; 2-py-C≡C is 2-pyridylethynyl, dppy=2-pyridyldiphenylphosphine) has been synthesized. Single-crystal X-ray structural analysis reveals that 1 has a trigonal bipyramidal Au10 Ag2 core that contains a planar Au4 (2-py-C≡C)3 unit sandwiched by two Au3 Ag(dppy)3 motifs. Cluster 1 shows intense red-NIR dual emission in solution. The visible emission originates from metal-to-ligand charge transfer (MLCT) from silver atoms to phosphine ligands in the Au3 Ag(dppy)3 motifs, and the intense NIR emission is associated with the participation of 2-pyridylethynyl in the frontier orbitals of the cluster, which is confirmed by a time-dependent density functional theory (TD-DFT) calculation.
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