Chen-Ho Tung

Copper(I)‐Catalyzed Interrupted Click Reaction: Synthesis of Diverse 5‐Hetero‐Functionalized Triazoles

The 5-heterofunctionalized triazoles are important scaffolds in bioactive compounds, but current click reactions (CuAAC) cannot produce these core structures. A copper(I)-catalyzed interrupted click reaction to access diverse 5-functionalized triazoles is reported. Various 5-amino-, thio-, and selenotriazoles were readily assembled in one step in high yields. The reaction proceeds under mild conditions with complete regioselectivity. It also features a broad substrate scope and good functional group compatibility.

Strain-Promoted Oxidative Annulation of Arynes and Cyclooctynes with Benzamides: Palladium-Catalyzed C–H/N–H Activation for the Synthesis of N-Heterocycles

Strained alkynes include arynes and cyclooctynes reacted with N-methoxyamides through palladium-catalyzed C-H/N-H activation for the first time. A variety of important N-heterocycles such as phenanthridinones and isoquinolones were constructed in one step with high efficiency.

Regioselective synthesis of multisubstituted 1,2,3-triazoles: moving beyond the copper-catalyzed azide–alkyne cycloaddition

Copper(i)-catalyzed azide-alkyne cycloaddition (CuAAC) is an essential click chemistry reaction that is widely used in chemical biology, medicinal chemistry and materials science. The CuAAC reaction of terminal alkynes provides a mild and efficient synthesis of 1,4-disubstituted 1,2,3-triazoles. However, the click reaction of internal alkynes with azides, giving trisubstituted triazoles, is very challenging. This feature article highlights the recent progress addressing this fundamental problem. Particular emphasis is on the current and emerging strategies to introduce functional groups to the C-5 position of triazoles in a regioselective manner.

Beyond Clusters: Supramolecular Networks Self‐Assembled from Nanosized Silver Clusters and Inorganic Anions

Assembly of small clusters into rigid bodies with precise shape and symmetry has been witnessed by the significant advances in cluster-based metal-organic frameworks (MOFs), however, nanosized silver cluster based MOFs remain largely unexplored. Herein, two anion-templated silver clusters, CO3 @Ag20 and SO4 @Ag22 , were ingeniously incorporated into a 2D sql lattice (1, [CO3 @Ag20 (iPrS)10 (NO3 )8 (DMF)2 ]n ) and an unprecedented 3D two-fold interpenetrated dia network (2, [SO4 @Ag22 (iPrS)12 (NO3 )6 ⋅2u2009NO3 ]n ), respectively, under mild solvothermal conditions. Their atomically precise structures were confirmed by single-crystal X-ray diffraction analysis and further consolidated by IR spectroscopy, thermogravimetric analysis (TGA), and elemental analysis. Each drum-like CO3 @Ag20 cluster is extended by twelve NO3 (-) ions to form the 2D sql lattice of 1, whereas each ball-shaped SO4 @Ag22 cluster with a twisted truncated tetrahedral geometry is pillared by four [Ag6 (NO3 )3 ] triangular prisms to form the 3D interpenetrated dia network of 2. Notably, 2 is the first interpenetrated 3D MOF constructed from silver clusters. These results demonstrate the dual role of the anions, which not only internally act as anion templates to induce the formation of silver thiolate clusters but also externally extend the cluster units into the rigid networks. The photoluminescent and electrochemical properties of 2 are discussed in detail.

Cu/Pd-Catalyzed, Three-Component Click Reaction of Azide, Alkyne, and Aryl Halide: One-Pot Strategy toward Trisubstituted Triazoles

A Cu/Pd-catalyzed, three-component click reaction of azide, alkyne, and aryl halide has been developed. By using this Cu/Pd transmetalation relay catalysis, a variety of 1,4,5-trisubstituted 1,2,3-triazoles were quickly assembled in one step in high yields with complete regioselectivity, just like assembling Lego bricks. Notably, different from the well-established CuAAC click reactions only working on terminal alkynes, this reaction offers an alternative solution for the problem of the click reaction of internal alkynes.

A superior fluorescent sensor for Al3+ and UO22+ based on a Co(II) metal–organic framework with exposed pyrimidyl Lewis base sites

A robust 3D pcu Co(II) metal–organic framework (MOF) based on a designed bent pyrimidyl–biimidazole ligand, [Co2(dmimpym)(nda)2]n (1; dmimpym = 4,6-di(2-methyl-imidazol-1-yl)-pyrimidine, H2nda = 1,4-naphthalenedicarboxylic acid), was successfully synthesized under solvothermal conditions and characterized using single-crystal X-ray diffraction. Compound 1 has a 2-fold interpenetrated 6-connected pcu network based on a [Co2(COO)4] paddle-wheel secondary building unit (SBU). It contains exposed pyrimidyl Lewis base sites, has porosity, and exhibits ligand-based blue emission in the solid state, which render it suitable as a fluorescent sensor for the detection of metal ions. Fluorescence titration experiments reveal that 1 is highly selective for Al3+ with exclusively enhanced emission as compared to other metal ions, and the limit of detection (LOD) reaches as low as 0.7 μM. Importantly, 1 can be cycled at least five times without the loss of emission signals. Moreover, 1 is able to detect low concentration of uranyl ions via fluorescence quenching. The present study sheds light on the realization of the practical application of MOFs as luminescent sensors via tailoring of the ligand and extends the way towards low-cost transition metal-based MOF sensors.

Water-Soluble Pentagonal-Prismatic Titanium-Oxo Clusters

By using solubility control to crystallize the prenucleation clusters of hydrosol, a family of titanium-oxo clusters possessing the {Ti18O27} core in which the 18 Ti(IV)-ions are uniquely connected with μ-oxo ligands into a triple-decked pentagonal prism was obtained. The cluster cores are wrapped by external sulfate and aqua ligands, showing good solubilities and stabilities in a variety of solvents including acetonitrile and water and allowing their solution chemistry being studied by means of electrospray ionization mass spectroscopy, (17)O NMR, and vibrational spectroscopy. Furthermore, this study provides new titanium oxide candidates for surface modifications and homogeneous photocatalysis.

Copper(I)-Catalyzed Three-Component Click/Alkynylation: One-Pot Synthesis of 5-Alkynyl-1,2,3-triazoles

A copper(I)-catalyzed tandem CuAAC/alkynylation reaction of various alkynes, organic azides, and bromoalkynes to provide rapid access to 5-alkynyl-1,2,3-triazoles has been developed. The reaction proceeded via a copper-catalyzed alkyne azide cycloaddition followed by interception of the in situ formed cuprate-triazole intermediate with bromoalkyne. This reaction offers a new method to afford fully substituted triazoles in high yields with complete regioselectivity under mild reaction conditions.

Anisotropic Assembly of Ag52 and Ag76 Nanoclusters

Although there has been an upsurge of interest in anisotropic assembly of inorganic nanoparticles, atomically precise self-assembly of anisotropic metal clusters is extremely rare. Herein, we presented two novel silver nanoclusters, Ag52 (SD/Ag23) and Ag76 (SD/Ag24), which are interiorly templated by five MoO42- and a pair of Mo6O228- anions, respectively, and coprotected by bridging RSH and terminal diphosphine ligands exteriorly. Regiospecific distribution diphosphine ligands on the surface and the arrangement of multiple molybdate templates within the nanoclusters synergetically tailor their shapes to anisotropic oblate spheroid and elongated rod, respectively. This work not only open up new avenues for the synthesis of silver nanoclusters with novel metal skeleton shapes and anisotropic surface structures but also give important insights for the anisotropic growth of silver nanoclusters through surface modifications or/and template organizations.

Core–Shell {Mn7⊂(Mn,Cd)12} Assembled from Core {Mn7} Disc

Postsynthetic decoration of the Mn7, {MnIII⊂MnII6}, core with CdII in the outer shell to form the next generation Mn13Cd6, {MnIII⊂MnIII3MnII3⊂ MnII6CdII6}, core-shell disc was achieved and confirmed by single-crystal X-ray diffraction. The formation of Mn13Cd6 has only been successful with CdII and if the Cd salt is added within the first half hour window when the inner Mn7 has formed. EDX and ICP-AES gave the accurate content and confirm the average found by X-ray diffraction. HR-ESI-MS was even more precise by revealing three prominent molecular species, Mn13Cd6, Mn14Cd5 and Mn15Cd4, having a distribution of metals. The presence of nonmagnetic metal on the periphery reduces the exchange between these clusters as well as the low magnetic moment decreases the dipolar interaction resulting in a paramagnet compared to the ferrimagnetism found for the parent Mn19, {MnIII⊂MnIII3MnII3⊂MnII12}, disc. This study opens the way for the syntheses of heterometallic core-shell clusters in a controllable fashion.