Sam C. K. Hau

Enlargement of globular silver alkynide cluster via core transformation.

The multinuclear metal-ligand supramolecular synthon R-C≡C⊃Ag(n) (R = alkyl, cycloalkyl; n = 3, 4, 5) has been employed to construct two high-nuclearity silver ethynide cluster compounds, [Cl(6)Ag(8)@Ag(30)((t)BuC≡C)(20)(ClO(4))(12)]·Et(2)O (1) and [Cl(6)Ag(8)@Ag(30)(chxC≡C)(20)(ClO(4))(10)](ClO(4))(2)·1.5Et(2)O (chx = cyclohexyl) (2), that bear the same novel Cl(6)Ag(8) central core. The synthesis of 1 made use of [Cl@Ag(14)((t)BuC≡C)(12)]OH as a precursor, and its reaction with AgClO(4) in CH(2)Cl(2) resulted in an increase in nuclearity from 14 to 38. The results presented here strongly suggest that the formation of multinuclear silver ethynide cage complexes 1 and 2 proceeds by a reassembly process in solution that involves transformation of the encapsulated chloride template within a Ag(14) cage into a cationic pseudo-O(h) Cl(6)Ag(8) inner core, leading to the generation of a much enlarged Cl(6)Ag(8)@Ag(30) cluster within a cluster. To our knowledge, this provides the first example of the conversion of a silver cluster into one of higher nuclearity via inner-core transformation.

A quinolinyl antipyrine based fluorescence sensor for Zn2+ and its application in bioimaging

By incorporating 4-aminoantipyrine moiety onto 8-aminoquinoline with a suitable spacer, a highly selective and sensitive fluorescent Zn2+ sensor, QPA, was designed and constructed. In 25% ACN-HEPES buffer pH 7.0 solution, QPA exhibited 10.6-fold fluorescence enhancement at 500 nm upon addition of Zn2+. The limit of detection (LOD) was calculated to be 1.3 × 10−7 M according to fluorescence titration. The 1 : 1 binding mode of the metal complex was established by combined UV-vis, fluorescence and HRMS spectroscopic method. The membrane permeability of QPA to living cells and bioimaging of Zn2+ are demonstrated.

Systematic Investigation of Silver–Carbon Bonding in Coordination Frameworks with Aryl Ligands That Contain Ethynyl and Ethenyl Substituents

Single-crystal X-ray diffraction of a series of ten crystalline silver(I)-trifluoroacetate complexes that contained designed ligands, each of which was composed of an aromatic system that was functionalized with terminal and internal ethynyl groups and a vinyl substituent, provided detailed information on the influence of ligand disposition and orientation, coordination preferences, and the co-existence of different types of silver(I)-carbon bonding interactions (silver-ethynide, silver-ethynyl, silver-ethenyl, and silver-aromatic) on the construction of coordination networks that were consolidated by argentophilic and weak inter/intramolecular interactions. The complex AgL10⋅6 AgCF3CO2⋅H2O⋅ MeOH (HL10 = 1-{[4-(prop-2-ynyloxy)-3-vinylphenyl]ethynyl}naphthalene) is the first reported example that exhibits all four kinds of silver(I)-carbon bonding interactions in the solid state.

Synthesis of unstable carbides Ag2C(2n) (n = 3, 4) and characterization via crystallographic analysis of their double salts with silver(I) trifluoroacetate.

Two new silver(I) carbides, Ag2C6 and Ag2C8, have been synthesized, and single-crystal X-ray analysis of their crystalline silver(I) trifluoroacetate complexes, Ag2C6·8AgCF3CO2·6H2O, 4(Ag2C6)·16AgCF3CO2·14.5DMSO, and 2.5(Ag2C8)·10AgCF3CO2·10DMSO, provides detailed information on the influence of ligand disposition and orientation of the all-carbon anionic ligands in the construction of multidimensional supramolecular structures, which are consolidated by argentophilic and weak inter-/intramolecular interactions.

Assembly of Heterometallic Silver(I)–Copper(I) Alkyl-1,3-diynyl Clusters via Inner-Core Expansion

New tetranuclear supramolecular precursors [(R-C≡C-C≡C)Ag]4 (R = iPr, tBu, and chx) are employed to construct a series of heterometallic silver(I)-copper(I) alkyl-1,3-diynyl cluster complexes (1-9) that bear a common CuAg3 core (normally trigonal-planar, but can be distorted to pyramidal) consolidated by cupro-argentophilic interaction under 3.12 Å, as found in 1 and 2. The photophysical properties of the multinuclear supramolecular precursors and selected complexes have been investigated. The present results strongly suggest that the assembly of medium-nuclearity clusters 3 to 9 is initiated by accretion of additional Ag(I) ions by the ubiquitous CuAg3 template through argentophilic (<3.4 Å) interaction, with cooperative cuprophilic enhancement (<2.76 Å) in the case of compound 9. To our knowledge, the present study provides the first report of conversion of a Group 11 homonuclear cluster into a heteronuclear one of higher nuclearity via inner-core expansion.

A colorimetric and ratiometric fluorescent pH probe based on ring opening/closing approach and its applications in monitoring cellular pH change

A colorimetric and ratiometric fluorescent pH probe with a pKa value of 6.0 based on a ring opening/closing approach of N,O-disubstituted hemiaminal ether has been developed. The probe exhibits fast response toward pH change with high selectivity and low cytotoxicity and was applied in HK-1 cells to visualize pH change.

Organosilver(I) Framework Assembly with Multinuclear Heteroaryl Ethynide Supramolecular Synthon R–C≡C⊃Agn (n=4, 5)

A series of six silver(i) trifluoroacetate complexes containing new ligands each composed of a quinolinyl or pyridyl nucleus bearing one or two terminal ethynyl substituent(s) has been synthesised. Single-crystal X-ray analysis of the complexes established the coordination preferences of the ethynide substituent(s) at variable positions with respect to the nitrogen donor atom, which serve as dominant factors in directing the construction of multi-dimensional organosilver(i) networks, which are consolidated by weak intermolecular interactions in supramolecular assembly.

Assembly of Layer-Type Organosilver(I) Complexes Incorporating Nitrate and Isomeric Halophenylethynide Ligands

Single-crystal X-ray analysis of a series of 10 silver(i) nitrate complexes containing carbon-rich ligands each composed of a halosubstituted phenyl nucleus bearing a terminal ethynyl group at various positions provided detailed information on the influence of ligand disposition and orientation, coordination preferences, and the co-existence of silver(i)–ethynide and silver(i)–halogen interactions in the construction of coordination networks, which are consolidated by argentophilic and weak intra or intermolecular interactions.

Organosilver(I) framework assembly with trifluoroacetate and enediyne-functionalized alicycles.

Eight new silver(I) trifluoroacetate complexes based on a series of designed ligands, each featuring an alicyclic ring with enediyne functionality, have been synthesized and characterized by single-crystal X-ray diffraction. Each ethynide terminal is inserted into an Agn (n = 4-5) basket, leading to the generation of coordination chain or layer structures, but the well shielded ethenyl group does not take part in silver-olefin bonding. Variation in ring size of the alicycles is shown to influence the construction of the organosilver(I) coordination networks, which are consolidated by weak intermolecular interactions in the crystal structures. The effect of adding ancillary N-donor ligands to the reaction system on the coordination and supramolecular network assembly is also investigated.

Electronic Spectra of Cs2NaYb(NO2)6: Is There Quantum Cutting?

The crystal structure and electronic spectra of the T h symmetry hexanitritoytterbate(III) anion have been studied in Cs2NaY0.96Yb0.04(NO2)6, which crystallizes in the cubic space group Fm3̅. The emission from Yb3+ can be excited via the NO2- antenna. The latter electronic transition is situated at more than twice the energy of the former, but at room temperature, one photon absorbed at 470 nm in the triplet state produces no more than one photon emitted. Some degree of quantum cutting is observed at 298 K under 420 nm excitation into the singlet state and at 25 K using excitation into either state. The quantum efficiency is ∼10% at 25 K. The energy level scheme of Yb3+ has been deduced from excitation and emission spectra and calculated by crystal field theory. New improved energy level calculations are also reported for the Cs2NaLn(NO2)6 (Ln = Pr, Eu, Tb) series using the f- Spectra package. The neat crystal Cs2NaYb(NO2)6 has also been studied, but results were unsatisfactory due to sample decomposition, and this chemical instability makes it unsuitable for applications.