Measurement of the Positive Muon Anomalous Magnetic Moment to 0.20 ppm.

We present a new measurement of the positive muon magnetic anomaly, a_{μ}≡(g_{μ}-2)/2, from the Fermilab Muon g-2 Experiment using data collected in 2019 and 2020. We have analyzed more than 4 times the number of positrons from muon decay than in our previous result from 2018 data. The systematic error is reduced by more than a factor of 2 due to better running conditions, a more stable beam, and improved knowledge of the magnetic field weighted by the muon distribution, ω[over ˜]_{p}^{'}, and of the anomalous precession frequency corrected for beam dynamics effects, ω_{a}.

Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm.

We present the first results of the Fermilab National Accelerator Laboratory (FNAL) Muon g-2 Experiment for the positive muon magnetic anomaly a_{μ}≡(g_{μ}-2)/2. The anomaly is determined from the precision measurements of two angular frequencies. Intensity variation of high-energy positrons from muon decays directly encodes the difference frequency ω_{a} between the spin-precession and cyclotron frequencies for polarized muons in a magnetic storage ring.

Multifunctionality of organometallic quinonoid metal complexes: surface chemistry, coordination polymers, and catalysts.

Quinonoid metal complexes have potential applications in surface chemistry, coordination polymers, and catalysts. Although quinonoid manganese tricarbonyl complexes have been used as secondary building units (SBUs) in the formation of novel metal-organometallic coordination networks and polymers, the potentially wider applications of these versatile linkers have not yet been recognized. In this Account, we focus on these diverse new applications of quinonoid metal complexes, and report on the variety of quinonoid metal complexes that we have synthesized.

Physically separated references for diffusion coefficient-formula weight (D-FW) analysis of diffusion-ordered NMR spectroscopy (DOSY) in water.

Development and application of physically separated references for aqueous (1)H DOSY diffusion coefficient-formula weight (D-FW) correlation analysis is reported. Commercially available biological buffers (Tris and HEPES) and a water-soluble alcohol (tert-butanol) were used as physically separated references for a Ru and a Mn complex in D(2)O. This extension of DOSY D-FW analysis expands its applicability to a wide variety of water-soluble molecules or metal complexes, with particular application to green chemistry.

Microstructure and elution of tetracycline from block copolymer coatings.

A critical metrology issue for pharmaceutical industries is the application of analytical techniques for the characterization of drug delivery systems to address interrelationships between processing, structure, and drug release. In this study, cast coatings were formed from solutions of poly(styrene-b-isobutylene-b-styrene) (SIBS) and tetracycline in tetrahydrofuran (THF). These coatings were characterized by several imaging modalities, including time-of-flight secondary ion mass spectrometry (TOF-SIMS) for chemical imaging and analysis, atomic force microscopy (AFM) for determination of surface structure and morphology, and laser scanning confocal microscopy (LSCM), which was used to characterize the three-dimensional structure beneath the surface.

Preservation of cocoa antioxidant activity, total polyphenols, flavan-3-ols, and procyanidin content in foods prepared with cocoa powder.

Little is known about the effects of common cooking processes on cocoa flavanols. Antioxidant activity, total polyphenols (TP), flavanol monomers, and procyanidin oligomers were determined in chocolate frosting, a hot cocoa drink, chocolate cookies, and chocolate cake made with natural cocoa powder. Recoveries of antioxidant activity, TP, flavanol monomers, and procyanidins ranged from 86% to over 100% in the chocolate frosting, hot cocoa drink, and chocolate cookies.

Incorporation of Fe3O4 nanoparticles into organometallic coordination polymers by nanoparticle surface modification.

Surface-modified Fe(3)O(4) nanoparticles (NPs) can be obtained by substituting [(eta(5)-semiquinone)Mn(CO)(3)] for oleylamine surface protecting groups. The resulting NP can function as a nucleus or template to generate crystalline coordination polymers that contain superparamagnetic Fe(3)O(4) NPs. Hybridized magnetic properties can be obtained by introducing paramagnetic metal nodes, such as Mn(2+), into the polymers (see picture).

Patterned monolayers of neutral and charged functionalized manganese arene complexes on a highly ordered pyrolytic graphite surface.

Complex patterns: The arene manganese tricarbonyl complexes [Mn(eta(5)-2,5-didodecoxy-1,4-semiquinone)(CO)(3)] and [Mn(eta(6)-1,4-dioctyloxybenzene)(CO)(3)] BF(4) form patterned monolayers on the surface of highly ordered pyrolytic graphite (HOPG), as a result of hydrogen-bonding, hydrophobic, and electrostatic interactions, leading to an ordered 2D array of manganese atoms or ions.

Impact of alkalization on the antioxidant and flavanol content of commercial cocoa powders.

Cocoa is a food ingredient that is important for the contribution of flavor to foods but is also associated with potential health benefits. The chemistry thought to be responsible for its cardiovascular health benefits is the flavanol (flavan-3-ol) antioxidants. Evidence from the literature indicates that natural cocoas are high in flavanols, but when the cocoa is processed with alkali, also known as Dutch processing or Dutching, the flavanols are substantially reduced.

Self-supported organometallic rhodium quinonoid nanocatalysts for stereoselective polymerization of phenylacetylene.

Heterogeneous self-supported organometallic nanocatalysts (ONs) were synthesized by treatment of the eta6-pi-hydroquinone rhodium complex [(1,4-hydroquinone)Rh(COD)]+ with Al(Oi-Pr)3. The organometallic nanocatalysts, the size of which can be controlled by alteration of the reaction conditions, show high catalytic activities in the stereoselective polymerization of phenylacetylene to produce cis-poly(phenylacetylene). A key feature of the ON catalyst synthesis is a facile eta6 to eta4 hapticity change occurring in the quinonoid ring, which is triggered by deprotonation of the -OH groups by Al(Oi-Pr)3, with concomitant coordination of the quinone oxygen atoms to the aluminum.

Pi-bonded quinonoid transition-metal complexes.

Coordination of the carbocyclic ring of hydroquinones to electrophilic transition-metal fragments such as Mn(CO)3+ and Rh(COD)+ produces stable pi-bonded eta6-complexes that are activated to facile reversible deprotonation of the -OH groups. The deprotonations are accompanied by electron transfer to the transition metal, which acts as an internal oxidizing agent or electron sink. With manganese as the metal, the resulting eta5-semiquinone and eta4-quinone complexes have been used to synthesize one- two- and three-dimensional polymeric metal-organometallic coordination networks.

Organometallic crystal engineering of [(1,4- and 1,3-hydroquinone)Rh(P(OPh)3)2]BF4 by charge assisted hydrogen bonding.

The ionic complexes [(1,4- and 1,3-hydroquinone)Rh(P(OPh)3)2]BF4 form porous organometallic structures dictated by charge assisted hydrogen bonding.

An anionic rhodium eta4-quinonoid complex as a multifunctional catalyst for the arylation of aldehydes with arylboronic acids.

The pi-bonded rhodium quinonoid complex, K+[(1,4-benzoquinone)Rh(COD)]-, functions as a good catalyst for the coupling of arylboronic acid and aldehydes to afford diaryl alcohols. The catalysis is heterobimetallic in that both the transition metal and concomitant alkali metal counterion play an integral part in the reaction. In addition, the anionic quinonoid catalyst itself plays a bifunctional role by acting as a ligand to the boronic acid and as a Lewis acid receptor site for the transferring aryl group.

Chemical and electrochemical reduction of polyarene manganese tricarbonyl cations: hapticity changes and generation of syn- and anti-facial bimetallic eta4,eta6-naphthalene complexes.

(Eta6-naphthalene)Mn(CO)(3)(+) is reduced reversibly by two electrons in CH(2)Cl(2) to afford (eta4-naphthalene)Mn(CO)(3)(-). The chemical and electrochemical reductions of this and analogous complexes containing polycyclic aromatic hydrocarbons (PAH) coordinated to Mn(CO)(3)(+) indicate that the second electron addition is thermodynamically easier but kinetically slower than the first addition. Density functional theory calculations suggest that most of the bending or folding of the naphthalene ring that accompanies the eta6 --> eta4 hapticity change occurs when the second electron is added.

Supramolecular metal-organometallic coordination networks based on quinonoid pi-complexes.

The use of organometallic pi-complexes in the coordination-directed self-assembly of polymeric structures is a new area with many potential applications. Supramolecular metal-organometallic coordination networks (MOMNs), which are described herein, consist of metal ion or metal cluster nodes connected by bifunctional "organometalloligands" that serve as spacers. The organometalloligand utilized in this work is the stable anionic complex (eta(4)-benzoquinone)Mn(CO)(3)(-) (p-QMTC), which binds through both quinone oxygen atoms to generate MOMNs having both backbone and pendant metal sites.

A coordination network containing metal-organometallic secondary building units based on pi-bonded benzoquinone complexes.

In DMSO-MeOH solvent the complex [(eta 4-benzoquinone)Mn(CO)3]- (QMTC) reacts with Mn2+ ions to produce the coordination polymer (Mn2[(eta 4-benzoquinone)Mn(CO)3]4(DMSO))n, which consists of dimanganese secondary building units interconnected by QMTC spacers.

Metal-Mediated Self-Assembly of π-Bonded Benzoquinone Complexes into Polymers with Tunable Geometries.

Coordination of Mn(CO) to the π system in hydroquinone facilitates proton loss to afford benzoquinone complexes. Subsequent σ coordination of the benzoquinone oxygen atoms to added metal ions results in neutral one-, two-, or three-dimensional quinoid polymers. The geometrical requirements of the metal ion and the presence of added "spacer" ligands dictate the type of polymer formed.

Activation of a Carbon-Oxygen Bond of Benzofuran by Precoordination of Manganese to the Carbocyclic Ring: A Model for Hydrodeoxygenation.

Stable unsaturated heterocycles such as benzofuran are difficult to remove from petroleum by conventional catalytic hydrotreating. However, in a model system, coordination of Mn(CO)(3)(+) to the aromatic ring of benzofuran activates the C-O bond towards insertion of [Pt(PPh(3))(2)] [Eq. (1)].

Structure of a neutral N-alkylated diaminedithiol (dadt) 99TcV complex: syn[99TcO(NEt-tmdadt)].

syn-(4-Ethyl-2,9-dimethyl-4,7-diaza-2,9-decanedithiolato)oxo (99Tc) technetium(V), syn-[99TcO(NEt-tmdadt)], [Tc(O)(C12H25N2S2)], Mr = 375, monoclinic, P2(1)/n, a = 9.638(2), b = 14.371(5), c = 11.