Resonant X-ray emission spectroscopy reveals d–d ligand-field states involved in the self-assembly of a square-planar platinum complex

Resonant X-ray Emission Spectroscopy (RXES) is used to characterize the ligand field states of the prototypic self-assembled square-planar complex, [Pt(tpy)Cl]Cl (tpy=2,2′:6′,2′′-terpyridine), and determine the effect of weak metal-metal and π-π interactions on their energy. © 2012 the Owner Societies

A Theoretical Simulation of Deformed Carbon Nanotubes with Adsorbed Metal Atoms: Enhanced Reactivity by Deformation

First-principles simulations were performed to investigate reaction of carbon nanotubes with adsorbed metal atoms. Mechanical modification of their structures enhances chemical reactivity of carbon nanotubes. Adsorption of a tungsten, tantalum, or niobium atom on a (5, 0) nanotube with a Stone-Wales defect was shown to have characteristically strong chemisorption. Bond-breaking in the carbon-carbon network and formation of a local metal-carbon complex were observed during the simulation. Adsorption of W, Ta, Ni or Mo on a twisted (5, 0) nanotube showed a preferred breaking of several bonds, even creating an opening in the wall. The enhanced chemical reactivity of deformed nanotubes is characterized by formation of a metal-carbon complex. Applications of the reaction are suggested.Comment: 12 pages, 4 figure

Ligand Substitution Dynamics

Substitution of a ligand in an inner sphere complex by an outside group is the most fundamental reaction in metal ion chemistr

Reclamation with Recovery of Radionuclides and Toxic Metals from Contaminated Materials, Soils, and Wastes

A process has been developed at Brookhaven National Laboratory (BNL) for the removal of metals and radionuclides from contaminated materials, soils, and waste sites. In this process, citric acid, a naturally occurring organic complexing agent, is used to extract metals such as Ba, Cd, Cr, Ni, Zn, and radionuclides Co, Sr, Th, and U from solid wastes by formation of water soluble, metal-citrate complexes. Citric acid forms different types of complexes with the transition metals and actinides, and may involve formation of a bidentate, tridentate, binuclear, or polynuclear complex species. The extract containing radionuclide/metal complex is then subjected to microbiological degradation followed by photochemical degradation under aerobic conditions. Several metal citrate complexes are biodegraded, and the metals are recovered in a concentrated form with the bacterial biomass. Uranium forms binuclear complex with citric acid and is not biodegraded. The supernatant containing uranium citrate complex is separated and upon exposure to light, undergoes rapid degradation resulting in the formation of an insoluble, stable polymeric form of uranium. Uranium is recovered as a precipitate (polyuranate) in a concentrated form for recycling or for appropriate disposal. This treatment process, unlike others which use caustic reagents, does not create additional hazardous wastes for disposal and causes little damage to soil which can then be returned to normal use

Studies of the complexation behavior of tetramorpholinylo-PNP-lariat ether with Ag(I), Ca(II), Cd(II), Cu(II) and Pb(II) using Electrospray Ionization Mass Spectrometry

In this publication the cationic metal complexes of tetramorpholinylo-PNP-lariat ether have been studied using electrospray ionization mass spectrometry (ESI-MS). The tandem mass spectra (MS/MS) of these complexes have also been tested to evaluate the stability of the different types of the complexes formed. As occurred, all selected metal cations form the complexes with 1 : 1 stoichiometry with the investigated ligand. Only silver ions create a ‘‘sandwich’’ type complex. Furthermore, the divalent cations form complexes with the nitrate anion adduct. In the case of Ca(II), Cd(II) and Pb(II) we also observed another type of the species with an additional water molecule attached to the parent complex

A catalytic cycle for oxidation of tert-butyl methyl ether by a double C−H activation-group transfer process

A square-planar, iridium(I) carbene complex is shown to effect atom and group transfer from nitrous oxide and organic azides, releasing the corresponding formate or formimidate and an iridium(I)−dinitrogen adduct. The dinitrogen complex performs C−H activation upon photolysis or thermolysis, regenerating the carbene from tert-butyl methyl ether with loss of H_2. Taken together, these reactions represent a net catalytic cycle for C−H functionalization by double C−H activation to generate metal−carbon multiple bonds. Additionally, the unusual group transfer from diazo reagents underscores the unique nature of the reactivity observed for nucleophilic-at-metal carbene complexes

Alkali-metal-mediated zincation (AMMZn) meets N-heterocyclic carbene (NHC) chemistry : Zn–H exchange reactions and structural authentication of a dinuclear Au(I) complex with a NHC anion

Merging two evolving areas in synthesis, namely cooperative bimetallics and N-heterocyclic carbenes (NHCs), this study reports the isolation of the first intermediates of alkali-metal-mediated zincation (AMMZn) of a free NHC and a Zn–NHC complex using sodium zincate [(TMEDA)NaZn(TMP)(tBu)2] (1) as a metallating reagent. The structural authentication of (THF)3Na[:C{[N(2,6-iPr2C6H3)]2CHCZn(tBu2)}] (2) and [Na(THF)6]+[tBu2Zn:C{[N(2,6-iPr2C6H3)]2CHCZn(tBu2)}]− (4), resulting from the reactions of 1 with unsaturated free NHC IPr (IPr = 1,3-bis(2,6-di-isopropylphenylimidazole-2-ylidene) and NHC complex ZntBu2IPr (3) respectively demonstrates that in both cases, this mixed-metal approach can easily facilitate the selective C4 zincation of the unsaturated backbone of the NHC ligand. Furthermore, the generation of anionic NHC fragments enables dual coordination through their normal (C2) and abnormal (C4) positions to the bimetallic system, stabilising the kinetic AMMZn intermediates which normally go undetected and provides new mechanistic insights in to how these mixed-metal reagents operate. In stark contrast to this bimetallic approach when NHC-complex 3 is reacted with a more conventional single-metal base such as tBuLi, the deprotonation of the coordinated carbene is inhibited, favouring instead, co-complexation to give NHC-stabilised [IPr·LiZntBu3] (5). Showing the potential of 2 to act as a transfer agent of its anionic NHC unit to transition metal complexes, this intermediate reacts with two molar equivalents of [ClAu(PPh3)] to afford the novel digold species [ClAu:C{[N(2,6-iPr2C6H3)]2CHCAu(PPh3)}] (6) resulting from an unprecedented double transmetallation reaction which involves the simultaneous exchange of both cationic (Na+) and neutral (ZntBu2) entities on the NHC framework

Spiropyran modified PDMS micro-fluidic chip device for photonically controlled sensor array detection of metal ions

Micro‐fluidic chips are particularly attractive in biological and life sciences for analytical purposes because they provide a convenient small platform for rapid analysis and detection [1]. Using micro‐fluidic devices for the determination of ions emerges as a potential solution to some of the challenges not overtaken by conventional techniques e.g. atomic absorption, inductively‐coupled plasma‐optical emission, mass spectrometry and ion‐selective electrodes [2]. For example, these devices can integrate complex sample handling processes, calibration, and detection steps into a compact, portable system. Moreover they require small sample volumes (low μl or nl), consume little power, and are easily constructed for multi‐analyte detection, either through multiple parallel fluidic architectures or by using arrays of detection elements. Organic photochromic compounds like spiropyrans are particularly interesting targets for the development of new approaches to sensing since they offer new routes to multi‐functional materials that take advantage of their photo‐reversible interconversion between two thermodynamically stable states (a spiropyran (SP) form, and a merocyanine (MC) form), which have dramatically different charge, polarity and molecular conformations. Furthermore, they can be easily incorporated into membranes for improved robustness and ease of handling [3], but from our perspective, most interesting of all, they have metal ion‐binding and molecular recognition properties which are only manifested by the MC form. Based on the coordinationinduced photochromism characteristic of the MC form, spiropyrans have been employed as molecular probes for metal ions and organic molecules [4]. In this abstract, we show how through integrating the beneficial characteristics of micro‐fluidic devices and spiropyrans photoswitches, a simple and very innovative chip configured as an on‐line metal ion sensor array can be realised (Figure 1). The micro‐fluidic device consists of five independent 94 μm depth, 150 μm width channels fabricated in polydimethylsiloxane. The spiropyran 1’‐(3‐carboxypropyl)‐3,3’‐dimethyl‐6‐nitrospiro‐1‐benzopyran‐2,2’‐indoline (SP‐COOH) is immobilised by physical adsorption directly on ozone plasma activated PDMS micro‐channel walls. When the colourless, inactive, spiropyran coating absorbs UV light it switches to the highly coloured merocyanine form (MC‐COOH), which also has an active binding site for certain metal ions. Therefore metal ion uptake can be triggered using UV light and subsequently reversed on demand by shining white light on the coloured complex, which regenerates the inactive spiropyran form, and releases the metal ion. When stock solutions of several metal ions (Ca2+, Zn2+, Hg2+, Cu2+, Co2+) are pumped independently through the five channels, different optical responses were observed for each metal (Figure 2), (i.e. complex formation with metal ions is associated with characteristic shifts in the visible spectrum), and the platform can therefore be regarded as a micro‐structured device for online multi‐component monitoring of metal cations