Staggered Assembly of a Dimeric Au13 Cluster: Impacts on Coupling of Geometric Isomerism.

The specific states of aggregation of metal atoms in sub-nanometer-sized gold clusters are related to the different quantum confinement volumes of electrons, leading to novel optical and electronic properties. These volumes can be tuned by changing the relative positions of the gold atoms to generate isomers. Studying the isomeric gold core and the electron coupling between the basic units is fundamentally important for nanoelectronic devices and luminescence; however, appropriate cases are lacking. In this study, the structure of the first staggered di-superatomic Au25 -S was solved using single-crystal X-ray diffraction. The optical properties of Au25 -S were studied by comparing with eclipsed Au25 -E. From Au25 -E to Au25 -S, changes in the electronic structures occurred, resulting in significantly different optical absorptions originating from the coupling between the two Au13 modules. Au25 -S shows a longer electron decay lifetime of 307.7 ps before populating the lowest triplet emissive state, compared to 1.29 ps for Au25 -E. The experimental and theoretical results show that variations in the geometric isomerism lead to distinct photophysical processes owing to isomerism-dependent electronic coupling. This study offers new insights into the connection between the geometric isomerism of nanosized building blocks and the optical properties of their assemblies, opening new possibilities for constructing function-specific nanomaterials.

Ligand engineering to achieve enhanced ratiometric oxygen sensing in a silver cluster-based metal-organic framework.

Ratiometric luminescent oxygen sensing based on dual fluorescence and phosphorescence emission in a single matrix is highly desirable, yet the designed synthesis remains challenging. Silver-chalcogenolate-cluster-based metal-organic frameworks that combine the advantages of silver clusters and metal-organic frameworks have displayed unique luminescent properties. Herein, we rationally introduce -NH2 groups on the linkers of a silver-chalcogenolate-cluster-based metal-organic framework (Ag12bpy-NH2) to tune the intersystem crossing, achieving a dual fluorescence-phosphorescence emission from the same linker chromophore. The blue fluorescence component has a 100-nm gap in wavelength and 8,500,000-fold difference in lifetime relative to a yellow phosphorescence component. Ag12bpy-NH2 quantifies oxygen during hypoxia with the limit of detection of as low as 0.1 ppm and 0.3 s response time, which is visualized by the naked eye. Our work shows that metal cluster-based MOFs have great potential in luminescent sensing, and the longer-lived charge-separated states could find more photofunctional applications in solar energy transformation and photocatalysis.

Extra Silver Atom Triggers Room-Temperature Photoluminescence in Atomically Precise Radarlike Silver Clusters.

Luminescent metal clusters show promise for applications in imaging and sensing. However, promoting emission from metal clusters at room temperature is a challenging task owing to the lack of an efficient approach to suppress the nonradiative decay process in metal cores. We report herein that the addition of a silver atom into a metal interstice of the radarlike thiolated silver cluster [Ag27 (St Bu)14 (S)2 (CF3 COO)9 (DMAc)4 ]⋅DMAc (NC1, DMAc=dimethylacetamide), which is non-emissive under ambient conditions, produced another silver cluster [Ag28 (AdmS)14 (S)2 (CF3 COO)10 (H2 O)4 ] (NC2) that displayed bright green room-temperature photoluminescence aided by the new ligand 1-adamantanethiol (AdmSH). The 28th Ag atom, which hardly affects the geometrical and electronic structures of the Ag-S skeleton, triggered the emission of green light as a result of the rigidity of the cluster structure.

A new silver cluster that emits bright-blue phosphorescence.

A new hexanuclear silver(i) cluster (NC-Ag6) that emits bright-blue phosphoresce with a lifetime of 22.4 µs and a quantum yield (QY) of 22% under ambient conditions was synthesized. A film combining NC-Ag6 with yellow cerium(iii)-doped yttrium aluminum garnet phosphors (YAG:Ce3+) displays "chameleon"-like emission (including white), which is related to excitation-dependent Förster resonance energy transfer (FRET) between dual phosphors. The mechanoresponsive luminescence colour of this silver cluster ranges from blue to green virtually without loss of QY.

Sulfonic Groups Lined along Channels of Metal-Organic Frameworks (MOFs) for Super-Proton Conductor.

Designing high-performance proton-conducting metal-organic frameworks simultaneously having highly hydrothermal stability and a high-density proton carrier remains a great challenge. Fe-MIL-88B is a classic metal-organic framework (MOF) with a large-size one-dimensional (1D) channel lined with a high-density uncoordinated metal atom for postfunctionalization; however this MOF cannot act as a proton conductor due to the weak hydrothermal stability. Here, we prepared an ultrastable isostructure Cr-MIL-88B, which is subsequently functionalized by anchoring 3-pyridinesulfonic acid and 2-(4-pyridyl) ethanesulfonic acid on the naked Cr atoms exposed on the surface of the host-framework, producing two new MOFs, i.e. Cr-MIL-88B-pyridine sulfonic acid (abbreviated as Cr-MIL-88B-PSA) and Cr-MIL-88B-pyridine ethanesulfonic acid (abbreviated as Cr-MIL-88B-PESA). Thus, Cr atoms on the host framework were modified by functional sulfonic groups, which stick out toward the center of the channel forming ordered high-density sulfonic groups as proton donors along the open channel and achieving the highest proton conductivity of 4.50 × 10-2 S cm-1 for Cr-MIL-88B-PESA and 1.58 × 10-1 S cm-1 for Cr-MIL-88B-PSA, surpassing that of the Nafion membrane.

New stable isomorphous Ag34 and Ag33Au nanoclusters with an open shell electronic structure.

A novel atom-precise 3-electron homosilver nanocluster (Ag34) has been assembled for the first time by the oxidation of a thiol. When adding AuPPh3Cl in the reaction, we obtained an alloyed Ag33Au nanocluster, which shares a similar framework as that of Ag34, in which a doping Au atom replaced a core silver atom. Notably, both Ag34 and alloyed Ag33Au demonstrated exceptional stability in solution and solid state over 3 months, which is difficult to explain by using the superatom model. Such Ag34 and Ag33Au complexes complement the nanoclusters with an open shell electronic structure and unveil a new approach to synthesize monodisperse nanoclusters under mild conditions.

Self-Assembly of a Stable Silver Thiolate Nanocluster Encapsulating a Lacunary Keggin Phosphotungstate Anion.

A polyoxometalate-templated silver(I) thiolate nanocluster has been synthesized by a one-pot reaction in high yield. This novel and stable nanocluster exhibits a core-shell structure with a Ag67S36 shell and two lacunary Keggin [PW9O34]9- cores, which is fully characterized by X-ray crystallography, X-ray photoelectron spectroscopy, UV-vis, powder X-ray diffraction, and cyclic voltammetry.