Octadentate zirconium(IV)-loaded macrocycles with varied stoichiometry assembled from hydroxamic acid monomers using metal-templated synthesis

Published: February 28, 2017The reaction between Zr(IV) and the forward endo-hydroxamic acid monomer 4-[(5-aminopentyl)(hydroxy)amino]-4-oxobutanoic acid (for-PBH) in a 1:4 stoichiometry in the presence of diphenylphosphoryl azide and triethylamine gave the octadentate Zr(IV)-loaded tetrameric hydroxamic acid macrocycle for-[Zr(DFOT₁)] ([M + H]⁺ calc 887.3, obs 887.2). In this metal-templated synthesis (MTS) approach, the coordination preferences of Zr(IV) directed the preorganization of four oxygen-rich bidentate for-PBH ligands about the metal ion prior to ring closure under peptide coupling conditions. The replacement of for-PBH with 5-[(5-aminopentyl) (hydroxy)amino]-5-oxopentanoic acid (for-PPH), which contained an additional methylene group in the dicarboxylic acid region of the monomer, gave the analogous Zr(IV)-loaded macrocycle for-[Zr(PPDFOT₁)] ([M + H]⁺ calc 943.4, obs 943.1). A second, well-resolved peak in the liquid chromatogram from the for-PPH MTS system also characterized as a species with [M + H]⁺ 943.3, and was identified as the octadentate complex between Zr(IV) and two dimeric tetradentate hydroxamic acid macrocycles for-[Zr(PPDFOT1D)₂]. Treatment of for-[Zr(PPDFOT₁)] or for-[Zr(PPDFOT1D)₂] with EDTA at pH 4.0 gave the respective hydroxamic acid macrocycles as free ligands: octadentate PPDFOT₁ or two equivalents of tetradentate PPDFOT1D (homobisucaberin, HBC). At pH values closer to physiological, EDTA treatment of for-[Zr(DFOT₁)], for-[Zr(PPDFOT₁)], or Zr(IV) complexes with related linear tri- or tetrameric hydroxamic acid ligands showed the macrocycles were more resistant to the release of Zr(IV), which has implications for the design of ligands optimized for the use of Zr(IV)-89 in positron emission tomography (PET) imaging of cancer.William Tieu, Tulip Lifa, Andrew Katsifis, and Rachel Cod

Entanglement of single-photons and chiral phonons in atomically thin WSe2_2

Quantum entanglement is a fundamental phenomenon which, on the one hand, reveals deep connections between quantum mechanics, gravity and the space-time; on the other hand, has practical applications as a key resource in quantum information processing. While it is routinely achieved in photon-atom ensembles, entanglement involving the solid-state or macroscopic objects remains challenging albeit promising for both fundamental physics and technological applications. Here, we report entanglement between collective, chiral vibrations in two-dimensional (2D) WSe$_2$ host --- chiral phonons (CPs) --- and single-photons emitted from quantum dots (QDs) present in it. CPs which carry angular momentum were recently observed in WSe$_2$ and are a distinguishing feature of the underlying honeycomb lattice. The entanglement results from a "which-way" scattering process, involving an optical excitation in a QD and doubly-degenerate CPs, which takes place via two indistinguishable paths. Our unveiling of entanglement involving a macroscopic, collective excitation together with strong interaction between CPs and QDs in 2D materials opens up ways for phonon-driven entanglement of QDs and engineering chiral or non-reciprocal interactions at the single-photon level

Complexes Formed in Solution Between Vanadium(IV)/(V) and the Cyclic Dihydroxamic Acid Putrebactin or Linear Suberodihydroxamic Acid

The ability of microbial siderophores to coordinate metal ions, particularly Fe(III), continues to generate interest in the poten-tial applications of these bioligands in the environment and medicine.13 Siderophores produced by terrestrial and marin

Mapping the medical outcomes study HIV health survey (MOS-HIV) to the EuroQoL 5 Dimension (EQ-5D-3L) utility index

10.1186/s12955-019-1135-8Health and Quality of Life Outcomes1718