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Double salts of silver acetylide with silver perfluoralkyl carboxylates were studied in relation to argentophilicity and solvent-induced structural diversity.

The first isomorphous triple salts of silver acetylide are reported.

A novel Pt(II) terpyridine complex that has a nicotinamide moiety linked to the terpyridyl ligand has been synthesized in good yield and studied structurally and spectroscopically. The complex, [Pt(Nttpy)-Cl](PF6)2 where Nttpy = 4'-(p-nicotinamide-N-methylphenyl)-2,2':6',2''-terpyridine, is observed to be brightly luminescent in the solid state at room temperature and at 77 K. The complex exhibits reversible vapochromic behavior and crystallographic change in the presence of several volatile organic solvents. Upon exposure to methanol vapors, the complex changes color from red to orange, and a shift to higher energy is observed in the emission maximum with an increase in excited-state lifetime and emission intensity. The crystal and molecular structures of the orange and red forms, determined by single-crystal X-ray diffraction on the same single crystal, were found to be equivalent in the molecular sense and only modestly different in terms of packing. In both forms, the cationic Pt(II) complexes possess distorted square planar geometries. Analysis of the orange form's crystal packing reveals the presence of solvent molecules in lattice voids, Pt…Pt separations averaging 3.75 Å and a zigzag arrangement between nearest neighbor Pt atoms, whereas the red form is devoid of solvent within the crystal lattice and contains complexes stacked with a nearly linear arrangement of Pt(II) ions having an average distance of 3.33 Å. On the basis of the crystallographic data, it is evident that sorption of methanol vapor induces a change in intermolecular contacts and Pt…Pt interactions in going from red to orange. Disruption of the d8-d8 metallophilic interactions consequently alters the emitting state from ³[(d)σ*--π*(terpyridine)] that is formally a metal--metal-to-ligand charge transfer (MMLCT) state in the red form to one in which the HOMO corresponds to a more localized Pt(d) orbital in the red form (³MLCT). [ABSTRACT FROM AUTHOR]

The article presents a study on the synthesis, structure, and photophysical properties of a heteronuclear gold(I)-silver(I) cluster that is emissive in solution at room temperature. It notes that the report is the first regarding the luminescence from a gold(I) carbonium system. It cites the findings of the single crystal x-ray structural analysis on the cationic part of the complexes. It mentions that complex 2 is brightly emissive while complex 3 is soluble in polar solvents like chloroform.

An atomically resolved gold nanocluster Au 99 (C≡CC 6 H 3 -2,4-F 2 ) 40 ( Au 99 ) with an unusual 59 valence electrons has been synthesized. Single-crystal X-ray diffraction reveals that its Au 79 kernel is a Au 49 Marks decahedron capped by two Au 15 units. The surface structure of Au 99 consists of 20 linear Au(C≡CR) 2 staples. Intercluster interactions are observed between these D 5 symmetric clusters. The existence of an unpaired electron is verified by magnetic measurement. Interestingly, this open-shell gold cluster Au 99 stays intact in toluene solution at 80 °C for more than a week, and it has good charging-discharging capability under electrochemical conditions. The compact ligand shell protection around the symmetric core accounts for the high stability. This work suggests that geometric factors may play a crucial role in determining the stability of a metal nanocluster, even though the cluster has an open-shell electronic structure.

The boundary between molecular and metallic gold nanoclusters is of special interest. The difficulty in obtaining atomically precise nanoclusters larger than 2 nm limits the determination of such a boundary. The synthesis and total structural determination of the largest all-alkynyl-protected gold nanocluster (Ph 4 P) 6 [Au 156 (C≡CR) 60 ] (R = 4-CF 3 C 6 H 4 -) ( Au 156 ) are reported. It presents an ideal platform for studying the relationship between the structure and the metallic nature. Au 156 has a rod shape with the length and width of the kernel being 2.38 and 2.04 nm, respectively. The cluster contains a concentric Au 126 core structure (Au 46 @Au 50 @Au 30 ) protected by 30 linear RC≡C-Au-C≡CR staple motifs. It is interesting that Au 156 displays multiple excitonic peaks in the steady-state absorption spectrum (molecular) and pump-power-dependent excited-state dynamics as revealed in the transient absorption spectrum (metallic), which indicates that Au 156 is a critical crossover cluster for the transition from molecular to metallic state. Au 156 is the smallest-sized gold nanocluster showing metal-like electron dynamics, and it is recognized that the cluster shape is one of the important factors determining the molecular or metallic nature of a gold nanocluster.

Great attention has been paid to nanoclusters having face-centered-cubic (fcc) metal kernels, because of the similarity of metal packing to that of bulk gold. So far, there is no precedent example of an all-alkynyl-protected fcc gold nanocluster with more than 100 gold atoms. We report the synthesis and total structure determination of an alkynyl-protected gold nanocluster [NEt 3 H] 2 [Au 110 ( p- CF 3 C 6 H 4 C≡C) 48 ] ( Au 110 ). It has an fcc Au 86 kernel with 24 peripheral Au(C≡CR) 2 staples. The Au 86 kernel consists of six close packing layers in the pattern of Au 6 :Au 16 :Au 21 :Au 21 :Au 16 :Au 6 . Electronic absorption spectroscopy shows Au 110 has a molecular-like discrete electronic structure, and transient absorption experiments reveal its nonmetallic nature.

Bimetallic nanoclusters Au 19 Cu 30 with chemical composition of [Au 19 Cu 30 (C≡CR) 22 (Ph 3 P) 6 Cl 2 ](NO 3 ) 3 (where RC≡C is from 3-ethynylthiophene (H 3 C 4 S-3-C≡CH) or ethynylbenzene (PhC≡CH)) has been synthesized. Single X-ray structural analysis reveals that Au 19 Cu 30 has a multishelled core structure of Au@Au 12 @Cu 30 @Au 6 , comprising a centered icosahedral Au 13 (Au@Au 12 ) surrounded by an icosidodecahedral Cu 30 shell and an outmost shell of a chairlike hexagonal Au 6 . The alkynyl carbon is bound to the hollow sites on the Au 19 Cu 30 nanocluster surface, which is a novel interfacial binding mode in alkynyl-protected alloy nanoclusters. The Cu 30 icosidodecahedron is unprecedented and Au 19 Cu 30 represents the first alkynyl-protected Au-Cu alloy nanocluster.

The first observation of luminescence from a structurally well-defined Ag(2)S molecular nanocluster is reported. Reaction of AgSBu(t)/AgBF(4) with N(2)H(4) in methanol affords the tetracationic cluster [Ag(62)S(13)(SBu(t))(32)](BF(4))(4), which has a core-shell configuration. The 14 silver(I) centers of the [Ag(14)S(13)] core are in a face-centered cubic arrangement with each edge bridged by a S(2-) ligand; the core is further connected to the [Ag(48)(SBu(t))(32)] shell via both Ag-S bonds and Ag···Ag interactions. This novel cluster displays intense red emission in both the solid state and solution at room temperature.

A new series of isostructural, brilliantly luminescent gold-silver complexes having the formula [Au3(mu3-E)Ag(PPh2py)3](BF4)2 where E = O, S, Se and Ph2Ppy = 2-diphenylphosphinopyridine has been synthesized and characterized. The structural core of these complexes is a Au3Ag metallophilically linked tetrahedron with a group-16 atom functioning as a mu3-ligand capping the three gold atoms. In the solid state, pairs of clusters are joined by two unsupported aurophilic interactions. The emission energy changes strikingly in going from O (blue) to S (yellow) and Se (orange). The luminescence from the E = O system is the first to be reported for a gold(I) oxo system. Additionally, the luminescent 4-methylpyridyl analogue with E = S has been prepared and structurally characterized. For E = S, Se, the change in emission energy with mu3-bridging atom provides a sound basis for an LMMCT assignment of the excited state while lifetime measurements support its spin-forbidden nature. Frozen glass measurements indicate the presence of a higher-energy emitting state for these systems, and for the E = O system, either LMMCT or metal-centered cluster-based emission can be proposed.