Spontaneous in situ generation of photoemissive aurophilic oligomers in water solution based on the 2-thiocytosine ligand

Complexes [Au(S-2-thiocytosinate)(PMe₃)] (2, 2-thiocytosine = 4-amino-2-mercaptopyrimidine) and [Au(S-2-thiocytosine)(PMe₃)](CF₃CO₂) (3) have been prepared by the reaction of [Au(acac)(PMe₃)] (1, acac = acetylacetonate) or [Au(OCOCF₃)(PMe₃)] with 2-thiocytosine, respectively. The equimolecular mixture of complexes 1 and 3 also produces [{Au(PMe₃)}₂(μ-S,N¹-2-thiocytosinate)](CF₃CO₂) (4), which features two distinct [Au(PMe₃)]⁺ groups coordinated to the S and N¹ atoms of the heterocycle. Complex 4 experiences a ligand redistribution process in water solution that liberates [Au(PMe₃)₂](CF₃CO₂) and a brightly coloured and luminescent species of [Au_n(μ-S,N¹-2-thiocytosinate)_n] stoichiometry, presumably as a tetraauracycle (n = 4).

The doubly-aurated [{Au(PMe₃)}₂(μ-S,N¹-2-thiocytosinate)]⁺ cation breaks up in water solution to form a strongly-coloured and photoluminescent neutral aurophilic oligomer.

Transition Metal Chain Complexes Supported by Soft Donor Assembling Ligands

The chemistry of discrete molecular chains constituted by metals in low oxidation states, displaying metal-metal proximity and stabilized by suitable metal-bridging, assembling ligands comprising at least one soft donor atom is comprehensively reviewed; complexes with a single (hard or soft) bridging atom (e.g., μ-halide, μ-sulfide, or μ-PR₂ etc.) as well as "closed" metal arrays (that fall in the realm of cluster chemistry) are excluded. The focus is on transition metal-based systems, with few excursions to cases combining transition and post-transition elements. Most relevant supporting ligands have neutral C, P, O, or S donor (mainly, N-heterocyclic carbene, phosphine, ether, thioether) or anionic donor (mainly phenyl, ylide, silyl, phosphide, thiolate) groups. A supporting-ligand-based classification of the metal chains is introduced, using as the classifying parameter the number of "bites" (i.e., ligand bridges) subtending each intermetallic separation. The ligands are further grouped according to the number of donor atoms interacting with the metal chain (called denticity in the following) and the column of the Periodic Table to which the set of donor atoms belongs (in ascending order). A complementary metal-based compilation of the complexes discussed is also provided in a concise tabular form.

Molecular gold strings: aurophilicity, luminescence and structure-property correlations

This review covers the compound class of one-dimensional gold strings. These compounds feature a formally infinite repetition of gold complexes as monomers/repeating units that are held together by aurophilic interactions, i.e. direct gold-gold contacts. Their molecular structures are primarily determined in the solid state using single crystal X-ray diffraction. The chemical composition of the employed gold complexes is diverse and furthermore plays a key role in terms of structure characteristics and the resulting properties. One of the most common features of gold strings is their photoluminescence upon UV excitation. The emission energy is often dependent on the distance of adjacent gold ions and the electronic structure of the whole string. In terms of gold strings, these parameters can be fine-tuned by external stimuli such as solvent, pH value, pressure or mechanical stress. This leads to direct structure-property correlations, not only with regard to the photophysical properties, but also electric conductivity for potential application in nanoelectronics. Concerning these correlations, gold strings, consisting of self-assembled individual complexes as building blocks, are the ideal compound class to look at, as perturbations by an inhomogeneity in the ligand sphere (such as the end of a molecule) can be neglected. Therefore, the aim of this review is to shed light on the past achievements and current developments in this area.

Aurophilicity in action: stepwise formation of dinuclear Au(i) macrocycles with rigid 1,8-dialkynylanthracenes

1,8-Bis(gold(i)-ethynyl)anthracene units find stabilisation by maximising aurophilic contacts under formation of macrocyclic anions linked to cationic gold(i) fragments.

Silver(i) dithiocarboxylate complexes – clustering and aggregation

Molecular structures and aggregation motifs of a series of neutral homoleptic silver(i) dithiocarboxylate are presented and a correlation between the substituent and aggregation motif as well as the differences from the (almost) analogous gold(i) complexes are discussed.