21 research outputs found
Cupriphication of gold to sensitize d10âd10 metalâmetal bonds and near-unity phosphorescence quantum yields
Outer-shell s0/p0 orbital mixing with d10 orbitals and symmetry reductionuponcupriphicationofcyclic trinucleartrigonal-planargold(I) complexes are found to sensitize ground-state Cu(I)âAu(I) covalent bonds and near-unity phosphorescence quantum yields. Heterobimetallic Au4Cu2 {[Au4(ÎŒ-C2,N3-EtIm)4Cu2(ÎŒ-3,5-(CF3)2Pz)2], (4a)}, Au2Cu {[Au2(ÎŒ-C2,N3-BzIm)2Cu(ÎŒ-3,5-(CF3)2Pz)], (1) and [Au2(ÎŒ-C2, N3-MeIm)2Cu(ÎŒ-3,5-(CF3)2Pz)], (3a)}, AuCu2 {[Au(ÎŒ-C2,N3-MeIm)Cu2(ÎŒ3,5-(CF3)2Pz)2], (3b) and [Au(ÎŒ-C2,N3-EtIm)Cu2(ÎŒ-3,5-(CF3)2Pz)2], (4b)} and stacked Au3/Cu3 {[Au(ÎŒ-C2,N3-BzIm)]3[Cu(ÎŒ-3,5-(CF3)2Pz)]3, (2)} formuponreactingAu3 {[Au(ÎŒ-C2,N3-(N-R)Im)]3 ((N-R)Im = imidazolate; R =benzyl/methyl/ethyl =BzIm/MeIm/EtIm)} with Cu3 {[Cu(ÎŒ-3,5(CF3)2Pz)]3 (3,5-(CF3)2Pz = 3,5-bis(trifluoromethyl)pyrazolate)}. The crystal structures of 1 and 3a reveal stair-step infinite chains whereby adjacent dimer-of-trimer units are noncovalently packed via twoAu(I)âŻCu(I)metallophilicinteractions,whereas 4a exhibitsa hexanuclear cluster structure wherein two monomer-of-trimer units are linked by a genuine d10âd10 polar-covalent bond with ligandunassisted Cu(I)âAu(I) distances of 2.8750(8) Ă
eachâthe shortest such an intermolecular distance ever reported between any two d10 centers so as to deem it a âmetalâmetal bondâ vis-Ă -vis âmetallophilic interaction.â Density-functional calculations estimate 35â 43kcal/molbindingenergy,akintotypicalMâMsingle-bondenergies. Congruently, FTIR spectra of4a showmultiple far-IR bands within 65â 200 cmâ1, assignable to vCu-Au as validated by both the HarveyâGray method of crystallographic-distance-to-force-constant correlation and dispersive density functional theory computations. Notably, the heterobimetallic complexes herein exhibit photophysical properties that are favorable to those for their homometallic congeners, due to threefold-to-twofold symmetry reduction, resulting in cuprophilicsensitizationinextinctioncoefficientandsolid-state photoluminescence quantum yields approaching unity (ΊPL = 0.90â0.97 vs. 0â0.83 for Au3 and Cu3 precursors), which bodes well for potential future utilization in inorganic and/or organic LED applications
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Photochemical and Photophysical Properties of Mononuclear and Multinuclear Closed Shell D10 Coinage Metal Complexes and Their Metallo-organometallic Adducts
This dissertation covers the studies of two major topics: the photochemistry of mononuclear and multinuclear gold(I) complexes and synthetic approaches to tailor photophysical properties of cyclic trinuclear d10 complexes. First a detailed photochemical examination into the photoreactivity of neutral mononuclear and multinuclear gold(I) complexes is discussed, with the aim of gold nanoparticle size and shape control for biomedical and catalysis applications. Next is a comprehensive systematic synthetic approach to tailor the photophysical properties of cyclic trinuclear d10 complexes. This synthetic approach includes an investigation of structure-luminescence relationships between cyclic trinuclear complexes, an examination into their Ï-acid/Ï-base reactivity with heavy metal cations and an exploration into the photophysical properties of new heterobimetallic cyclic trinuclear complexes. These photophysical properties inspections are used to screen materials for their employment in molecular electronic devices such as organic light-emitting diodes (OLEDs) and thin film transistors (OTFTs)
<i>In vitro </i>and<i> in vivo</i> generation and characterization of <i>Pseudomonas aeruginosa </i>biofilm-dispersed cells via c-di-GMP manipulation
Bis-(3âČ-5âČ)-cyclic dimeric guanosine monophosphate (c-di-GMP) is a global secondary bacterial messenger that controls the formation of drug-resistant multicellular biofilms. Lowering the intracellular c-di-GMP content can disperse biofilms, and it is proposed as a biofilm eradication strategy. However, freshly dispersed biofilm cells exhibit a physiology distinct from biofilm and planktonic cells, and they might have a clinically relevant role in infections. Here we present in vitro and in vivo protocols for the generation and characterization of dispersed cells from Pseudomonas aeruginosa biofilms by reducing the intracellular c-di-GMP content through modulation of phosphodiesterases (PDEs). Unlike conventional protocols that demonstrate biofilm dispersal by biomass quantification, our protocols enable physiological characterization of the dispersed cells. Biomarkers of dispersed cells are identified and quantified, serving as potential targets for treating the dispersed cells. The in vitro protocol can be completed within 4 d, whereas the in vivo protocol requires 7 d.NRF (Natl Research Foundation, Sâpore)MOE (Min. of Education, Sâpore)Accepted versio
In vitro and in vivo generation and characterization of Pseudomonas aeruginosa biofilmâdispersed cells via c-di-GMP manipulation
Pyruvate-depleting conditions induce biofilm dispersion and enhance the efficacy of antibiotics in killing biofilms in vitro and in vivo
CRISPR interference to interrogate genes that control biofilm formation in Pseudomonas fluorescens
Measurement of the branching fraction for inclusive semileptonic B meson decays
A largely model-independent measurement of the inclusive electron momentum
spectrum and branching fraction for semileptonic decays of B mesons is
presented based on data recorded at the Upsilon(4S) resonance with the BABAR
detector. Backgrounds from secondary charm decays are separated from prompt B
decays using charge and angular correlations between the electron from one B
meson and a high momentum electron tag from the second B meson. The resulting
branching fraction is BR(B -> X e nu) = (10.87 +-0.18(stat)+-0.30(syst))%.
Based on this measurement we determine the CKM matrix element |V_cb|
Measurement of the branching fraction for inclusive semileptonic B meson decays
A largely model-independent measurement of the inclusive electron momentum
spectrum and branching fraction for semileptonic decays of B mesons is
presented based on data recorded at the Upsilon(4S) resonance with the BABAR
detector. Backgrounds from secondary charm decays are separated from prompt B
decays using charge and angular correlations between the electron from one B
meson and a high momentum electron tag from the second B meson. The resulting
branching fraction is BR(B -> X e nu) = (10.87 +-0.18(stat)+-0.30(syst))%.
Based on this measurement we determine the CKM matrix element |V_cb|