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We directly link iridium (Ir) anomalies in New Jersey to the mass extinction of marine plankton marking the Cretaceous-Paleogene (K-Pg) boundary. We confirm previous reports of an Ir anomaly 20 cm below the extinction of Cretaceous macrofauna (the 'Pinna' bed) with new results from a muddy sand section from Tighe Park, Freehold, New Jersey (United States), but we also show that Ir anomalies correlate with marine mass extinctions at three other clay-rich New Jersey sections. Thus, we attribute the anomaly at Freehold to the downward movement of Ir and reaffirm the link between impact and mass extinction. doi: 10.1130/G31135.1

The synthesis and characterization of neutral heteroleptic molecular iridium(III) complexes with (2,4-difluoro)phenylpyridine and different pyridine-1,2,4-triazole ligands are described. The studies have shown high external quantum efficiencies and color points better than the standard for blue iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,[C.sup.2]]picolinate.

The synthesis and photophysics properties of new homocysteine-selective sensor based on the iridium(III) complex are described. The studies have shown that the complex can selectively recognize homocysteine over other amino acids and thiol-related peptides through a color change.

The studies about the photophysical and electrochemical properties of [Ir[(ppy or pq).sub.2] (substituted-1,10-phenanthroline)]-[P[F.sub.6]] (ppy = 2-phenypyridine, pq = 2-phenylquinoline) is presented. The results provide insight into nature and number of the phenanthroline substituents to tune the color, quantum yield, and lifetime of the emission.

The mechanism for triplet energy transfer from the green-emitting fac-tris[2-(4'-tert-butylphenyl)pyridinato]-iridium (Ir[(tBu-ppy).sub.3]) complex to the red-emitting bis[2-(2'-benzothienyl)pyridinato-N,[C.sup.3')(acetylacetonato)-iridium (Ir[(btp).sub.2](acac)) phosphor is reported. The findings suggest that the triplet energy transfer occurs via the Forster mechanism when the transition dipole moments involved on energy donor and acceptor are not neglible.

Selective NO reduction under excess O2 conditions on Ir is studied in detail and it is shown that excess O2 can poison the Ir catalyst for NO reduction and the poisoning starts from a low O coverage on the surface. It is demonstrated that NO reduction is sensitive to the choice of reductant and that alkenes are the most effective because they are able to produce surface C atoms that can selectively remove O atoms from Ir steps.

A study on the molecular design of a highly efficient red-phosphorescent complex suitable for red OLED devices is conducted. With a decrease in the energy of the lowest excited triplet state, the Kr value of phosphorescence from the Ir(thp)(sub 3) family significantly decreases, thereby leading to a low quantum yield of red phosphorescence.

The mechanisms governing the transformation of thin, polycrystalline diamond films into single crystal films by textured growth are studied. Different experimental results study show that the heteroepitaxial nucleation on iridium buffer layers yields an alternative class of diamond films.

It is found that incorporation of SnO2 and Sb2O5 into IrOx not only saved the precious content significantly but also generated a synergic effect to make Ti/IrOx-Sb2O5-SnO2 much more stable. Ternary IrOx-Sb2O5-SnO2 is a promising electocatalyst for O2 evolution.

Research is presented concerning the photophysical and synthesis investigation of a family of cyclometalated iridium(III) complexes. The ligands within the cyclometalated complexes are discussed.

The low temperature adsorption of cyclobutane on the hexagonally closed-packed (hcp) Ir(111) surface is studied using temperature-programmed desorption and high-resolution electron energy loss spectroscopy. The occurrence on the Ir(111) surface by multilayered induced reaction (MIR) of cyclobutane is conclusively proved.

The roles of carboxylato and sulfonamido ligands is made clear by a comparative synthetic, structural and thermodynamic study of coordinatively unsaturated chelate complexes, which are monomeric in solution and in the solid states. However, the oxalato complex exists as a 'n' oligomer or polymer that serves as a versatile precursor to monomeric adducts 6-L.

Research has been conducted on the bis(mu-chloro)tetracarbonyldirhodium(I) and chlorotricarbonyliridium(I). The reactions of these compounds in conjugate Bronsted-Lewis superacid and in CO atmosphere are described.

Issues concerning the examination of the intramolecular dihydrogen/hydride exchange in the iridium complexes IrXH2(eta squared-H2)(PR3)2 (X=Cl, Br, I) using density functional theory are discussed. Calculations indicate that the oxidative-addition/reductive-elimination route is the preferred mechanism for this process.

Research has been conducted on the iridium(III) nitrosyl complex. Reactions of the complex with hydrosulfide and arenethiolate anions have been investigated.

Research has been conducted on the Rh-Te and Ir-Te binary systems. The use of Huckel calculations in investigating the systems' differences in phase and structure at low temperatures is described.

The article discusses synthesis of different iridium carboxamides that are analogous to intermediates in metal-catalyzed nitrile hydration reactions. Experiments include generation of these carboxamides by addition of Cp (super)* (PMe (sub)3)IrPh(OH) to RCN.

A study conducted the first in situ electrochemical scanning tunneling microscopy of sulfate adsorption on the atomically flat surface of Ir(111) with well defined, step terrace structure. The Ir(111) in HClO4 solution had a hexagonal structure with atomic distance of 0.27 nm in the potential range from 0.1 V - 1.0 V. A model for the co-adsorption of water and sulfate was used to explain the observed adlayer structure. Other experimental findings are presented.

Research was conducted to examine the iridium-catalyzed enantioselective hydrogenation of imines in supercritical carbon dioxide. Detailed experiments including high-pressure NMR and in situ reflectance FT-IR spectroscopy offered an insight into the phase behavior, the solubility and possible interactions of the different reaction components with compressed CO2. Results suggest that the reactivity of the products to form the corresponding carbamic acids has an important role to play for the application of the new methodology.

A study was conducted to determine the liquid crystal and nonlinear optical properties of rhodium (I) and iridium (I) complexes containing beta-diketonate or pyrazole ligands. X-ray single-crystal diffraction analysis show that some beta-diketonate compounds have two different polymorphs at the solid state. It was also found that the color and infrared spectra of the solid forms seem to be influenced by a different intermetallic-packing arrangement in the metal centers.

Density functional method and a zeolite cluster model were used to study computationally the interaction of Ir4 and a zeolite support. The zeolite model consisted of six O atoms and six Si or Al atoms facing a supercage of a faujasite framework. Results showed that the interaction induces an electron transfer from the faujasite support to the metal cluster and a moderate charge rearrangement in the bonding site between the Ir and O centers.

Research was conducted to examine the synthesis of cationic dinuclear hydrido complexes of ruthenium, rhodium, and iridium with bridging thiolato ligands and their reactions with nitrosobenzene. X-ray diffraction studies of the molecular structures of the three nitrosobenzene complexes showed that in each case, nitrosobenzene serves as a mu-eta(super 1):eta(super 1)-N,O ligand. The unpaired electron is considered to be located mainly on the nitrosobenzene ligand in the diruthenium and dirhodium complexes.

Research was conducted to examine the spectroscopic characterization of the cyclometalated complex (IrH(dppf(-H))(dppf))+ that results from the intramolecular oxidative addition of the ortho C-H bond of the phenyl substituents in 1,1'-bis(diphenylphosphino)ferrocene (dppf)(Ir(dppf)2)+. Results provide a rade example of compounds in which the same set of ligands appears to sustain the metal in four different oxidation states. Findings also provide the opportunity to investigate the structural changes of the (IrP4)(super n) moiety on changing the charge of the complex (n = +1, 0, -1).

The synthesis, the electrochemical nature and the spectroscopic and photophysical characteristics of IrLL'3+ complexes are described. The favorable properties of IrLL'3+ reveal that the Ir(III)-tpy center will not be the final recipient of the energy-harvesting mechanisms in multipartite systems built around them. Results demonstrate that the Ir-tpy-type complexes are appropriate as photoactive centers and electron relays.

The reaction of laser-ablated iridium atoms with dioxygen afforded the linear dioxide OIrO and the side-bound dioxygen adduct (O2)IrO2 as primary reaction products. Iridium and oxygen isotopic splittings characterized the strong insertion product OIrO, with the isotopic shifts showing the product to be linear. Density functional theory and the D95* basis set gave accurate calculations of the geometry and frequencies for OIrO with 0.96 and 0.94 scale factors. Experimental results agreed well with the calculated v(sub 1) and V(sub 3) ordering and spacing.

Research was conducted to examine the synthesis of several functionalized polypyridine ligands and of five new Ir(III) cyclometalated derivatives as well as the absorption spectra, luminescence properties and the redox behavior of the new metal complexes. The ligands present a bidentate 6-phenyl-2,2'-bipyridine framework substituted in the 4'-position with a phenyl ring having different para X substituents. Results suggest that the complexes may be considered as useful building blocks for light- and redox-active, multicomponent supramolecular systems.

The catalysis of alkane dehydrogenation by iridium(III) complexes is investigated using density functional theory. Theoretical results reveal that catalytic alkane dehydrogenation to alkane occurs through alkane oxidative addition, beta-H transfer from alkyl ligand to metal, dihydride reductive elimination and elimination of the olefin. The reaction endothermicity is gradually achieved in the catalytic cycle for alkane dehydrogenation by (PCP')Ir(H)(sub 2).

A study was conducted to analyze continuous thin iridium films and iridium island films supporting iridium particles bigger than 25 Angstrom in diameter. Vacuum evaporation was carried out to prepare the samples. An electron microscope was then utilized to determine the particle size and electron-diffraction pattern. Results indicated that optical plasma-resonance absorption was absent in the iridium island films. The absence was correlated with the localization of conduction electrons of iridium.

Combined Ir, Os, Cu, and S concentrations from 18 eastern Australian peridotite xenoliths demonstrate systematic variations in Os concentrations with S loss and require a late-stage process capable of fractionating Os from the geochemically similar Ir. This effect accounts for the greater variability and lower mean Os concentrations observed in peridotite xenoliths as compared with massif peridotites and abyssal peridotites. Late-stage mobility of Os in xenoliths has important implications for interpreting Os isotopic data, and strong correlations between Cu/S and Ir/Os may provide a method for screening Re-Os data to provide more reliable Os isotopic model ages. The ability of cryptic secondary processes to fractionate some platinum-group elements (PGEs), in this case Ir and Os, must be taken into account before attributing fractionated PGE patterns in xenoliths to primary mantle processes.

Oxygen quenching of the luminescence of mononuclear and dinuclear Ir(III) cyclometalated complexes immobilized in the pPEGMA matrixes has been studied. Linear Stern-Volmer plots, even when experiments at different emission wavelengths have been performed, were evidenced. Despite the different luminescence lifetimes of the chromophores in the absence of quencher, similar Stern-Volmer slopes have been calculated. This behavior was tentatively interpreted by taking into account the size and charge of the chromophores. Increased sizes and lower charges seem to enhance the sensitivity of the systems. Such findings could be of interest for the design of new solid-state luminescent oxygen sensors with improved performance.

In the present paper, fabrication, characterization, and physiological applications of a solid-state pH electrode are described. The pH sensing layer was based on an anodic electrodeposited iridium oxide film (AEIROF). Sputtered platinum electrodes (1 mm diameter) fabricated on flexible Kapton films or platinum wires were used as planar or cylindrical supports. Each electrode site was coated with Nation to attenuate the interference of anionic redox species and to protect the electrode surface during in vivo measurements. Performance of the AEIROF was evaluated, for the first time, as a pH electrode and proved to have a slightly super-Nernstian response with slope of -63.5 [+ or -] 2.2 mV/pH unit for both wire and planar sputtered platinum electrodes. Linear pH responses were obtained in the pH range 2-10. The electrodes have a working lifetime of at least 1 month with accuracy of about 0.02 pH unit and fast response time. The electrodes showed very low sensitivities for different species, such as [Na.sup.+], [K.sup.+], [Li.sup.+], N[[H.sub.4].sup.+], [Ca.sup.2+], [Mg.sup.2+], dissolved oxygen, lactate, ascorbate, and urate, which are important for physiological applications. The electrodes were applied in extracellular pH measurements during brief regional ischemia in a swine heart and no-flow ischemia in an isolated rabbit papillary muscle. A first report on extracellular pH, [K.sup.+], and lactate simultaneous measurements during no-flow ischemia using the AEIROF pH electrode and the previously described [K.sup.+] and lactate electrodes is presented as well.

The oxidative addition of dihydrogen to a series of [Ir(bisphosphine)(1,5-cyclooctadiene)]BF4 compounds was described as a model for stereocontrol and dynamic processes involved in catalytic hydrogenation. The activation of dihydrogen by cationic diphosphine derivatives of Rh is crucial in the catalytic asymmetric hydrogenation of prochiral enamides. Results showed a complex pathway for isotope scrambling and diastereomer interconversion that does not involve reductive elimination of hydrogen to form [Ir(Me-DuPhos)(COD)]+.

A study is conducted on the rhodium(I) and iridium(I) chloride complexes of a tris(phosphinine). The SiMe2-linked tris(phosphinine) reacts with (M(COD)Cl)2 (M = Rh, Ir) to yield the complexes Rh(tris(phosphinine)) and Ir(tris(phosphinine)). Results show that the crystal structure of Rh(tris(phosphinine)) features a highly twisted geometry of (tris(phosphinine)) around the rhodium center. Abstraction of the chloride ligands with AgOtf in the presence of CH3CN also forms corresponding cationic complexes.

The facile decapping of a heptanuclear rhenium-iridium carbido carbonyl cluster and the capping reactions of the cluster with (triphenylphosphine)gold(I) derivatives are described. Both monogold and digold derivatives are formed with the addition of [AuP-Ph3]+ caps to the trianion. While the digold complex exhibits only one structure in both the solid and liquid states, several isomers of the monogold complex are seen in the solution.

An extended X-ray absorption fine structure measurement was used to examine the structure of the oxide layers of the RuO2-IrO2/Ti electrode system and the thermal decomposition processes of RuCl3 and IrCls to form their respective oxides. Results showed that the heating of both chlorides causes them to decompose into their respective oxides. The coordination number of the oxide ions around the ruthenium and iridium ions increase with the calcination temperature. Moreover, the binary oxide system of RuO2-IrO2 forms a solid solution.

An investigation of the effect of substituting the Cp ligand of [CpIr(L)H3]BF4 complexes with the hydrotris(1-pyrazolyl)borate (Tp)9 ligand found that partial substitution of the hydride positions with deuterium or tritium results in temperature-dependent isotope shifts and resolvable coupling constants. Data indicate that the isotope shifts result from a preference for the heavy isotope to occupy the hydride site. Analysis of the data provided the limiting chemical shifts of the ligands and the 1JH-D coupling constant in the bound hydrogen ligand.

A study was conducted to provide experimental and computational evidence about the mechanisms involved in the C-H activation reaction by cationic Ir(III) complexes using electrospray ionization tandem mass spectrometry. Intermediate metallaphosphacyclopropane was produced after the elimination of CH4 in the gas phase which then react with the C-H bond of alkanes and arenes. Differences in the results of the gas-phase and the solution-phase were also seen providing proof of the presence of competing mechanisms for C-H activation.

Reaction of the monodeprotonated silaborate with the respective pentamethylcyclopentadienyl transition metal chloride allows the synthesis of the sandwich anions [(eta-5-C5Me5)M(MeSiB10H10)]-(M = Co, Rh, Ir). The thermal reaction between a substituted derivative of the carba-nido-undecaborane, derived from bis(trimethylsilyl)acetylene and decarborane(14), and CpCo(Co)2 produces a mixture of two sandwich complexes. The transition metal adopts an 18-electron configuration in the sandwich complex.

An efficient catalytic transfer of oxygen to carbon monoxide from amine and oranoselenium oxides was performed through the use of rhodium(I) and iridium(I) carbonyls. Findings revealed that the reactions were principally facilitated by metal carbonyl complexes in small proportions in solution. Despite their catalyzing abilities, however, the rhodium and iridium complexes do not react with the oxides without added CO.

The solvent exchange process for (eta5-C5Me5)M(S)3]2+ (M = Rh, S = MeCN) was found to proceed via a dissociative mechanism. Intermolecular exchange with free Me2SO on (eta5-C5Me5)M(S)3]2+ (S = Me2SO) takes place exclusively from a conformational isomer which is in equilibrium with a second, more compact conformer. The rate constants associated with the solvent exchange process on the half-sandwich species were shown to be governed primarily by electronic properties of the ligands.

The electronic influence of an ancillary ligand on metal-diazenido bonding induces a facile rearrangement of an aryldiazenido ligand from a singly-bent to a bridging geometry. This was demonstrated when the strong pi-base ligands I-, Br- and Cp*Ir(CO)2 were separately reacted with the complex ((eta5-C5Me5)Ir(C2H5)(p-N2C6H4OMe))(BF4) to replace its ethylene ligand. The reactions afforded the diiridium complexes ((eta5-C5Me5)IrX)2(mu-eta2-p-N2C6H4OMe)(mu-eta1-p-N2C6H4OMe) where X = I,Br and (((eta5-C6Me5)Ir(CO))2(mu-eta2-p-N2C6H4OMe))(BF4).

Direct iridium and rhodium insertion into an unstrained aryl-methyl bond at room temperature was performed for the first time. The reaction, which yields ClM(CH3)(C6H(CH3)3(CH2P(t-Bu)2)2), required treating the complex M2(olefin)4Cl4 where M = Rh,Ir with diphosphine 1,3-bis((di-tert-butylphosphino)methyl)-2,4,6-trimethylbenzene in solution. The C-C oxidative addition mechanism, which competes with a C-H activation process, is thermodynamically favored during the reaction.

Suitable reactions in sealed Nb tubing at 850-950 degrees C produced good yields of a family of oligomeric cluster phases that were characterized by single-crystal X-ray diffraction methods. The basic Y16Z4 units can be obtained from 2+2 condensation of centered Y6Br12Z-type clusters or as tetracapped truncated tetrahedra Y16 that are centered by a large tetrahedral Z4. These are surrounded by 36 bromine atoms which bridge edges or cap faces of the Y16Z4 nuclei and, in part, bridge to metal atoms in other clusters.

The trimetallic complexes of the form (((bpy)2Ru(bpm))2MCl2)5+, where M=Rh(III) or Ir(III), are synthesized and characterized to determine the ability of bpm to act as a bridging ligand in this structural motif. These systems also demonstrate how central metal variation can be employed to tune the characteristics of these complexes. These systems are interesting because the have catalytically active Ir or Rh metal centers covalently connected to two light-absorbing ruthenium chromophores, forming the core of a molecular device for photoinitiated electron collection.

A two dimensional quantum mechanical exchange model explains the coupling of the hydrides ligands in cationic iridium trihydride complexes ((eta-C5R5)Ir(L)H3)BF4, where R = H, Me and L = phosphines. The high coupling constant, J(sub AB), is due to quantum mechanical exchange coupling of hydride ligands that occur via vibrational motion. Substitution of hydrogens by deuterium and tritium affects the hydride chemical shift and J(sub AB). However, kinetic isotope effects on thermally activated hydride rearrangement are unaffected by the substitution.

The iridium and ruthenium complexes are reacted with poly(pyrazol)borato complexes to form heterodinuclear species with Co and Ni. The reaction is performed to investigate the coordination capacity of the iridium and ruthenium anions as tridentate ligands. New heterodinuclear complexes with pyrazolate and other mononegative bridging ligands are prepared and their molecular structures reported.

Simple syntheses of dinuclear complexes are provided by protonation of the methoxo groups in M(mu-OMe)(diolefin) 2 (M = Rh, Ir) with acidic proton-bearing binucleating ligands. Py(SH)2 reacts with (Rh mu-OMe cod )2 (cod = 1,5-cyclooctadiene) to form Rh4(mu-PyS2)2(cod)4, 1. Analogous preparations also give the diolefin rhodium complexes Rh4(mu-PyS2)2(nbd)4, 2, and Rh4(mu-PyS2)2(tfbb)4, 3, (nbd = norborna-2,5-diene, tfbb = tetrafluorobenzo 5,6 bicyclo 2.2.2 octa-2,5,7-triene). 1 is a tetranuclear complex with two 2,6-pyridinethiolate groups linking four metal centers.

A new synthetic pathway to Fischer carbene complexes of iridium involving the activation of carbon-hydrogen bonds of methyl and cyclic ethers is introduced. The new route, which was implemented via the thermolysis of a triflate in tetrahydrocortisol, also involves the formation of intermediate cationic iridium alkyl complexes which, in turn, undergo rapid alpha-hydrogen migration to yield hydridocarbene complexes.