Great attention is currently paid to the synthesis of polynuclear transition metal complexes and the study of their photochemical, photophysical, and electrochemical properties. This interest is stimulated, in particular, by attempts to design and construct multicomponent systems (often called supramolecular species) capable of performing useful lightand/or redox-induced functions.1-16 A great deal of investigations on mononuclear transition metal complexes had previously shown that several families of these compounds are very interesting from the electrochemical, photochemical, and photophysical viewpoints.17-22 The metalligand interaction, in fact, is often (i) weak enough to allow the manifestation of intrinsic properties of metal and ligands (e.g., ligand-centered and metalcentered absorption bands and redox waves) and, at the same time, (ii) strong enough to cause the appearance of new properties, characteristic of the whole compound (e.g., metal-to-ligand or ligand-tometal charge-transfer bands). On passing from mononuclear to polynuclear transition metal complexes, the situation becomes even more interesting because in the latter (supramolecular) compounds one can find, besides properties related to each metal-based component, properties related to the structure and composition of the whole array. A suitable choice of the mononuclear building blocks and bridging ligands and an appropriate design of the (supramolecular) structure can in fact allow the occurrence of very interesting and potentially useful processes such as energy transfer along predetermined pathways, photoinduced charge separation, multielectron exchange at a predetermined potential, etc. The knowledge on the luminescence and redox properties of polynuclear transition metal complexes is rapidly accumulating, but it is disperse in a great number of journals. We have made an attempt to collect the available results, and we present them together with some fundamental introductory concepts and a few comments. One of the main problems, of course, was to delimit the field of this review. Using personal criteria which are related to our own research interests, we decided to consider only polynuclear transition metal complexes that can be defined as supramolecular species (section 2.2) and that are reported to exhibit luminescence. For such compounds only, the electrochemical properties have also been reviewed. Furthermore, we decided to include only classical (Werner-type) polynuclear transition metal compounds where the number of metal-based units is exactly known and the connection between the metal centers is provided only by bridging ligands. Thus, a number of interesting systems such as polymer-appended metal † In memoriam of Mauro Ciano. 759 Chem. Rev. 1996, 96, 759−833

Luminescent and Redox-Active Polynuclear Transition Metal Complexes.

Matrix-assisted ultraviolet laser desorption of non-volatile compounds

Atomically precise pieces of matter of nanometer dimensions composed of noble metals are new categories of materials with many unusual properties. Over 100 molecules of this kind with formulas such as Au25(SR)18, Au38(SR)24, and Au102(SR)44 as well as Ag25(SR)18, Ag29(S2R)12, and Ag44(SR)30 (often with a few counterions to compensate charges) are known now. They can be made reproducibly with robust synthetic protocols, resulting in colored solutions, yielding powders or diffractable crystals. They are distinctly different from nanoparticles in their spectroscopic properties such as optical absorption and emission, showing well-defined features, just like molecules. They show isotopically resolved molecular ion peaks in mass spectra and provide diverse information when examined through multiple instrumental methods. Most important of these properties is luminescence, often in the visible–near-infrared window, useful in biological applications. Luminescence in the visible region, especially by clusters prot...

Atomically Precise Clusters of Noble Metals: Emerging Link between Atoms and Nanoparticles

Metabolomics, which is the profiling of metabolites in biofluids, cells and tissues, is routinely applied as a tool for biomarker discovery. Owing to innovative developments in informatics and analytical technologies, and the integration of orthogonal biological approaches, it is now possible to expand metabolomic analyses to understand the systems-level effects of metabolites. Moreover, because of the inherent sensitivity of metabolomics, subtle alterations in biological pathways can be detected to provide insight into the mechanisms that underlie various physiological conditions and aberrant processes, including diseases.

Metabolomics: beyond biomarkers and towards mechanisms

Small gold clusters (∼1 nm) protected by molecules of a tripeptide, glutathione (GSH), were prepared by reductive decomposition of Au(I)−SG polymers at a low temperature and separated into a number of fractions by polyacrylamide gel electrophoresis (PAGE) Chemical compositions of the fractionated clusters determined previously by electrospray ionization (ESI) mass spectrometry (Negishi, Y et al J Am Chem Soc 2004, 126, 6518) were reassessed by taking advantage of freshly prepared samples, higher mass resolution, and more accurate mass calibration; the nine smallest components are reassigned to Au10(SG)10, Au15(SG)13, Au18(SG)14, Au22(SG)16, Au22(SG)17, Au25(SG)18, Au29(SG)20, Au33(SG)22, and Au39(SG)24 These assignments were further confirmed by measuring the mass spectra of the isolated Au:S(h-G) clusters, where h-GSH is a homoglutathione It is proposed that a series of the isolated Au:SG clusters corresponds to kinetically trapped intermediates of the growing Au cores The relative abundance of

Glutathione-Protected Gold Clusters Revisited: Bridging the Gap between Gold(I)−Thiolate Complexes and Thiolate-Protected Gold Nanocrystals

Protein and polymer analyses up to m/z 100 000 by laser ionization time-of-flight mass spectrometry

Mass distributions of copper, silver and gold clusters and electronic shell structure

Use of field desorption mass spectra of polystyrene and polypropylene glycol as mass references up to mass 10000

The computer program PAAS 3 is developed to determine the probable amino acid sequences of a peptide from sequence ion peaks experimentally obtained by mass spectrometry.

PAAS 3: A computer program to determine probable sequence of peptides from mass spectrometric data

Photosubstitution of Ru(bpy) 2 BX 2 (bpy = 2,2'-bipyridine ; B = 3,3'-dimethyl-2,2'-bipyridine (dmbpy) or 2-(aminomethyl)pyridine (ampy) ; and X = ClO 4 - or PF 6 - ) has been studied in both acetonitrile and pyridine by using on-line electrospray mass spectrometry. For the complexes with B = dmbpy and ampy, intermediates with a monodentate (one-legged) B ligand, Ru(bpy) 2 BS 2 and Ru(bpy) 2 BSX + (S = solvent molecule), were detected for the first time in the electrospray mass spectra, together with the photosubstitution products Ru(bpy) 2 S 2 2+ and Ru(bpy) 2 S 2 X + . For the complex with B = ampy, minor photoproducts that resulted from dissociation of bpy, Ru(bpy)BS 2 2+ and Ru(bpy)BS 2 X + , were detected. The solvent-released ions Ru(bpy) 2 S 2+ , Ru(bpy) 2 2+ , and Ru(bpy) 2 SX + , which were secondary products from collision-induced dissociation of the photosubstitution reaction, were also seen. The effects of solvent and intensity of irradiation on the photoreactions were also studied. It was shown for the first time that the reaction intermediates with B = dmbpy can be detected after photoirradiation of electrosprayed charged droplets at the spray needle of the electrospray mass spectrometer. The electrospray technique, combined with use of a flow-through photoreaction cell or with direct photoirradiation of electrosprayed charged droplets, was demonstrated to be a powerful tool for the study of photosubstitution and for the detection of reaction intermediates

Takekiyo Matsuo

Papers

Protein and polymer analyses up to m/z 100 000 by laser ionization time-of-flight mass spectrometry

Mass distributions of copper, silver and gold clusters and electronic shell structure

Use of field desorption mass spectra of polystyrene and polypropylene glycol as mass references up to mass 10000

PAAS 3: A computer program to determine probable sequence of peptides from mass spectrometric data

Detection of Reaction Intermediates: Photosubstitution of (Polypyridine)ruthenium(II) Complexes Using Online Electrospray Mass Spectrometry