An [FeIII34] Molecular Metal Oxide

The dissolution of anhydrous iron bromide in a mixture of pyridine and acetonitrile, in the presence of an organic amine, results in the formation of an [Fe₃₄] metal oxide molecule, structurally characterised by alternate layers of tetrahedral and octahedral Fe^III ions connected by oxide and hydroxide ions. The outer shell of the complex is capped by a combination of pyridine molecules and bromide ions. Magnetic data, measured at temperatures as low as 0.4 K and fields up to 35 T, reveal competing antiferromagnetic exchange interactions; DFT calculations showing that the magnitudes of the coupling constants are highly dependent on both the Fe‐O‐Fe angles and Fe?O distances. The simplicity of the synthetic methodology, and the structural similarity between [Fe₃₄], bulk iron oxides, previous Fe^III–oxo cages, and polyoxometalates (POMs), hints that much larger molecular Fe^III oxides can be made.     

High-speed varifocal imaging with a tunable acoustic gradient index of refraction lens

Fluidic lenses allow for varifocal optical elements, but current approaches are limited by the speed at which focal length can be changed. Here we demonstrate the use of a tunable acoustic gradient (TAG) index of refraction lens as a fast varifocal element. The optical power of the TAG lens varies continuously, allowing for rapid selection and modification of the effective focal length at time scales of 1 mus and shorter. The wavefront curvature applied to the incident light is experimentally quantified as a function of time, and single-frame imaging is demonstrated. Results indicate that the TAG lens can successfully be employed to perform high-rate imaging at multiple locations.     

Fast optical preparation, control, and readout of a single quantum dot spin

We propose and demonstrate the sequential initialization, optical control, and readout of a single spin trapped in a semiconductor quantum dot. Hole spin preparation is achieved through ionization of a resonantly excited electron-hole pair. Optical control is observed as a coherent Rabi rotation between the hole and charged-exciton states, which is conditional on the initial hole spin state. The spin-selective creation of the charged exciton provides a photocurrent readout of the hole spin state.     

Single-Molecule Observation of Intermediates in Bioorthogonal 2-Cyanobenzothiazole Chemistry

We report a single-molecule mechanistic investigation into 2-cyanobenzothiazole (CBT) chemistry within a protein nanoreactor. When simple thiols reacted reversibly with CBT, the thioimidate monoadduct was approximately 80-fold longer-lived than the tetrahedral bisadduct, with important implications for the design of molecular walkers. Irreversible condensation between CBT derivatives and N-terminal cysteine residues has been established as a biocompatible reaction for site-selective biomolecular labeling and imaging. During the reaction between CBT and aminothiols, we resolved two transient intermediates, the thioimidate and the cyclic precursor of the thiazoline product, and determined the rate constants associated with the stepwise condensation, thereby providing critical information for a variety of applications, including the covalent inhibition of protein targets and dynamic combinatorial chemistry.     

Dual copper- and photoredox-catalysed reactions

The merger of transition metal catalysis with visible light photoredox catalysis in a cooperative fashion has recently emerged as a versatile way of developing new synthetic methodologies. This review will focus on the relatively new but fast expanding area of dual copper- and photoredox-catalysis, detailing recent developments in the area.     

The problem of irregular perfect systems of sets of iterated differences

Fors2, the set of iterated differences associated with the prescribed integersa(s, j), 1js, is the set {a(i, j): 1jis} wherea(i–1,j)=|a(i, j)–a(i, j+1)|, general problem raised by work of Kreweras and Loeb concerns the existence of partitions of runs of consecutive integers into full sets of iterated differences. In the regular case, where all the sets of iterated differences have the same valencys, it is known that such partitions do not exist at least fors>8. We find here that the problem is more challenging in the case where the sets have different valencies.