A luminescent Ag8(DPPY)6(PhCC)6 cluster with a triangular superatomic Ag8 core.

We have synthesized single crystals of a highly stable Ag8 nanocluster protected by six ligands of diphenyl-2-phosphinic pyridine (DPPY) plus six ligands of phenylacetylene (PhCC). This Ag8(DPPY)6(PhCC)6 cluster bears a triangular superatomic Ag8 core, with the vertex and edge Ag atoms (quasi-triangle Ag6) being protected by both P and N bidentate coordination of the six DPPY ligands; meanwhile, the six PhCC ligands via µ3-C coordination form coordination on the two central Ag atoms capped on both sides of the triangle facet. Apart from the well-organized coordination of the two ligands pertaining to the balanced interactions with the Ag8 core, this Ag8 nanocluster exhibits superatomic stability with two delocalized valence electrons (1S2||1P0), assuming that the six PhCC ligands fix 6 localized electrons from the Ag atoms. Interestingly, the Ag8(DPPY)6(PhCC)6 NCs display temperature-dependent dual emissions at 330 and 535 nm under deep ultraviolet excitation. TD-DFT calculations reproduced the experimental spectrum, shedding light on the nature of excitation states and metal-ligand interactions in such a superatomic metal cluster.

A stable superatomic Cu6(SMPP)6 nanocluster with dual emission.

We have synthesized single crystals of a highly stable Cu6 nanocluster protected by six ligands of 2-mercapto-5-n-propylpyrimidine (SMPP). This Cu6(SMPP)6 cluster has a quasi-octahedral superatomic Cu6 core, with the Cu atoms being protected by both -S- and N-bidentate coordination of the SMPP ligands. Interestingly, each Cu atom is linked with an N atom, while the two neighboring Cu atoms on the same triangular facet are linked by the -S- bridge of the ligand. Single-crystal parsing results show that the altered orientation of the SMPP ligands give rise to three packing modes (named as 1, 2, and 3) of the Cu6(SMPP)6 NCs. Apart from the well-organized coordination, this Cu6(SMPP)6 nanocluster exhibits superatomic stability with a metallic core of 4 valence electrons (1S22S2||3S2), enabling to largely balance the interactions between the polynuclear core and delocalized electrons. Interestingly, the Cu6(SMPP)6 NCs display dual emissions in both ultraviolet-visible (UV-Vis) and near-infrared (NIR) regions. First-principles calculations well reproduce the experimental spectrum, shedding light on the nature of excitation states and metal-ligand interactions in the Cu6(SMPP)6 cluster.

A mono-copper doped undeca-gold cluster with up-converted and anti-stokes emissions of fluorescence and phosphorescence.

We have synthesized single crystals of a highly stable Cu-doped undeca-gold cluster protected by both triphenylphosphine (PPh3) and 2-pyridinethiol (-SPy) ligands, formulated as [Au11Cu1(PPh3)7(SPy)3]+. This cluster (Au11Cu1 NCs for short) has a metallic core of C3v Au@Au10 with the Cu atom capped on one of the nine triangular facets and it is triply-coordinated to three N atoms of the SPy ligands of which the sulfur atom simultaneously binds to three adjacent Au atoms via singly-coordinated S-Au bonds, respectively. The other seven gold atoms form a crown structure by a link of three orthogons with common sides and are protected by seven PPh3 ligands. Besides the well-organized coordination, this Au11Cu1 nanocluster is demonstrated to exhibit superatom stability of the metallic core within 8 valence electrons (assuming that the 3 electrophilic-SPy ligands capture 3 electrons from the metal center). More interestingly, this Au11Cu1 nanocluster shows interesting emissions in both ultraviolet visible (UV-Vis) and near infrared (NIR) regions, and the emissions display novel anti-Stokes up-conversion lasing characteristics. TD-DFT calculated UV-vis and emission spectra well reproduce the experimental results, shedding light on the nature of excitation states and underlying mechanism of electronic transitions between diverse energy levels of such a monolayer-protected bimetallic cluster.

Cl@Ag22 Au6 (4-TBBT)28 (PPh4 ): A Chloride-Centered Ag-Au Bimetallic Cluster for Optics.

We report the single-crystal synthesis of a chlorine-centered bimetallic cluster, Cl@Ag22 Au6 (4-TBBT)28 (PPh4 ), which bears a quatrefoil-structured Cl@Ag22 (SR)16 core studded by six Au(SR)2 staples showing a quasi Td symmetry. This cluster bears 28 metal atoms and 28 ligands, with a chlorine atom hosted in the center of the metallic Ag22 Au6 core. Single-crystal analysis shows that this cluster possesses essentially a different bonding nature compared with other monolayer-protected metal clusters (MPCs) or traditional metal-sulfur complexes. We fully dissect the structure evolution in forming such a chlorine-centered cluster. Interestingly, this cluster, Cl@Ag22 Au6 (4-TBBT)28 (PPh4 ), displays a fluorescence emission at 570 nm and supports the solid emission with a minor red shift at 574 nm. On the other hand, we have tested the nonlinear optical property and observed unambiguous nonlinear optical property with a normal valley-shaped transmittance curve corresponding to reverse saturated absorption (RSA) of the cluster.