Cadmium Dicyanoaurates and Their Reaction with Ammonia

The synthesis and crystal structures of two anionic cadmium dicyanoaurate coordination polymers, [nBu4N]6[(Cd4Cl4)2(Au(CN)2)12][CdCl4] (TCCA) and [nBu4N]2[Cd(Au(CN)2)4], and their reaction with ammonia vapour is reported. TCCA and the isostructural [nBu4N]6[(Cd4Br4)2(Au(CN)2)12][CdBr4] form 3-D arrays with [Cd4X4]4+ (X=Cl, Br) cubane clusters linked from each octahedral Cd(II) centre by three bridging [Au(CN)2]- units. TCCA reacts with ammonia with concentrations of 1000 ppm or higher to give a product with a quantum yield of 0.88, while [nBu4N]2[Cd(Au(CN)2)4], which forms a 2-D anionic Cd[Au(CN)2]2 sheet structure with axially pendant [Au(CN)2]- units, reacts with concentrated ammonia vapour to generate Cd(NH3)2[Au(CN)2]2; this has a similar 2-D sheet structure but with axial NH3 units. Vibrational spectroscopy illustrated that the reaction of both Cd/[Au(CN)2]-based materials with ammonia proceeded by breaking Cd-NC bonds. For [nBu4N]2[Cd(Au(CN)2)4], this results in decomposition into [nBu4N][Au(CN)2] ⋅ 0.5H2O and Cd(NH3)2[Au(CN)2]2, while the reaction of ammonia with TCCA is reversible by heating the ammonia-bound sample above 110 °C. Cd[Au(CN)2]2 can be prepared by thermal removal of NH3 units from Cd(NH3)2[Au(CN)2]2.

Terpyridine isomerism as a tool for tuning red-to-NIR emissive properties in heteronuclear gold(I)-thallium(I) complexes

The polymeric linear chain [AuTl(C6Cl5)2]n reacts with three terpyridine-type ligands substituted with thiophene groups containing N-donor centres in different relative positions (L1, L2 and L3), leading to the Au(I)/Tl(I) complexes [AuTl(C6Cl5)2(L1)]n (1), [{AuTl(C6Cl5)2}2(L2)]n (2) and [AuTl(C6Cl5)2(L3)]n (3). X-Ray diffraction studies reveal that L1 acts as a chelate, while L2 and L3 act as bridging ligands, resulting in different coordination indexes for the thallium(I) centre. These structural differences strongly influence their optical properties, and while compounds 2 and 3 emit near the limit of the visible range, complex 1 emits in the infrared region. DFT calculations have also been carried out in order to determine the origin of the electronic transitions responsible for their optical properties.

Homoleptic Alkynylphosphonium Au(I) Complexes as Push-Pull Phosphorescent Emitters

A series of compounds P1-P4 bearing terminal alkynyl sites connected with a phosphonium group via different π-conjugated linkers have been synthesized. The compounds themselves are efficient push-pull emitters and exhibit bright fluorescence in blue and near-UV regions. P1-P4 were used as alkynyl ligands to obtain a series of homoleptic bis-alkynyl Au(I) complexes 1-4. The complexes demonstrate bright phosphorescence and dual emission with dominating phosphorescence (2-4). Terphenyl derivative complex 3 exhibits warm white emission in DMSO solution and pure white emission in PMMA films. Time-dependent density functional theory calculations have shown that the T₁ excited state has a hybrid MLCT/ILCT nature with a dominant contribution of charge transfer across a ligand-centered "D-π-A" system. The variation of linker allows tuning the effect of intermolecular charge transfer and thus changing the electronic and photophysical properties of the organogold "D-π-A" system. The results presented unambiguously display the advances of the conception of organometallic "D-π-A" construction.

Keep it tight: a crucial role of bridging phosphine ligands in the design and optical properties of multinuclear coinage metal complexes

Copper subgroup metal ions in the +1 oxidation state are classical candidates for aggregation via non-covalent metal-metal interactions, which are supported by a number of bridging ligands. The bridging phosphines, soft donors with a relatively labile coordination to coinage metals, serve as convenient and essential components of the ligand environment that allow for efficient self-assembly of discrete polynuclear aggregates. Simultaneously, accessible and rich modification of the organic spacer of such P-donors has been used to generate many fascinating structures with attractive photoluminescent behavior. In this work we consider the development of di- and polynuclear complexes of M(i) (M = Cu, Ag, Au) and their photophysical properties, focusing on the effect of phosphine bridging ligands, their flexibility and denticity.

A photoactive copper iodide phosphine-based coordination polymer

Coordination of the polymetallic [Cu₄I₄] center by phenyl-based-diphosphine ligands results in a coordination polymer exhibiting luminescence thermochromic properties.

Novel chloride-centered Ag18 clusters featuring a cuboctahedral Ag12 skeleton

Two novel chloride-centered Ag₁₈ clusters with the same framework but different supporting phosphines are synthesized by the reaction of PhC[triple bond, length as m-dash]CAg, AgSbF₆, PPh₃ (or P(p-Tol)₃), and NaBH₄ in CH₂Cl₂, followed by the addition of PhC[triple bond, length as m-dash]CH and NEt₃. The inner twelve Ag atoms of these two clusters are arranged in a rare cuboctahedral structure, which can be rationalized by considering a ligand effect. Through careful analysis, we find that the central chloride arises from a generally ignored but nonetheless existing reaction between CH₂Cl₂ and NEt₃, which is well recognized as the Menshutkin reaction. This research provides insights into the dependence of the cluster structure on the nature of the ligand and into the cluster formation mechanism of the Menshutkin reaction.

A model electrode of well-defined geometry prepared by direct laser-induced decoration of nanoporous templates with Au-Ag@C nanoparticles

We present an original type of model electrode system consisting of bimetallic Au-Ag nanoparticles embedded in an amorphous carbon matrix with an extremely well-defined geometry of parallel, straight, cylindrical macropores. The samples are prepared in one step by direct laser deposition of the metal/carbon composite onto the inner walls of a porous 'anodic' alumina matrix serving as a template. The coating is homogeneous from top to bottom of the pores, and the amount of material deposited can be tuned by the duration of the deposition procedure. As a test system, we demonstrate that a bimetallic Ag-Au@C system is catalytically active for the electrochemical oxidation of glucose in alkaline solution, the anodic reaction of a direct glucose fuel cell. Furthermore, the electrocatalytic current density increases with the amount of Ag-Au@C NPs deposited, up to a point at which the pores are clogged with it. This type of model system allows for the systematic study of geometric effects in fuel cell electrodes. It can be generalized to a number of different nanoparticle compositions, and thereby, to various electrocatalytic reactions.

New Au(i)–Cu(i) heterometallic complexes: the role of bridging pyridazine ligands in the presence of unsupported metallophilic interactions

The use of N-donor pyridazine ligands in different amounts in the reaction with a Au(i)/Cu(i) precursor allows the control of metallophilic interactions in the solid state.

Effect of solvent polarity on the spectroscopic properties of an alkynyl gold(i) gelator. The particular case of water

The spectroscopic properties of an aurophilic hydrogelator depend on solvent polarity and concentration.

Laser-induced transformation of supramolecular complexes: approach to controlled formation of hybrid multi-yolk-shell Au-Ag@a-C:H nanostructures

In the present work an efficient approach of the controlled formation of hybrid Au–Ag–C nanostructures based on laser-induced transformation of organometallic supramolecular cluster compound is suggested. Herein the one-step process of the laser-induced synthesis of hybrid multi-yolk-shell Au-Ag@a-C:H nanoparticles which are bimetallic gold-silver subnanoclusters dispersed in nanospheres of amorphous hydrogenated a-C:H carbon is reported in details. It has been demonstrated that variation of the experimental parameters such as type of the organometallic precursor, solvent, deposition geometry and duration of laser irradiation allows directed control of nanoparticles’ dimension and morphology. The mechanism of Au-Ag@a-C:H nanoparticles formation is suggested: the photo-excitation of the precursor molecule through metal-to-ligand charge transfer followed by rupture of metallophilic bonds, transformation of the cluster core including red-ox intramolecular reaction and aggregation of heterometallic species that results in the hybrid metal/carbon nanoparticles with multi-yolk-shell architecture formation. It has been found that the nanoparticles obtained can be efficiently used for the Surface-Enhanced Raman Spectroscopy label-free detection of human serum albumin in low concentration solution.

Alkynyl-functionalized gold NHC complexes and their coinage metal clusters

Phenylpropynyl-functionalized N-heterocyclic carbenes as ligands for the synthesis of heterometallic hexanuclear coinagemetal clusters which exhibit mixed metallophillic interactions and intense white photoluminescence at low temperature.