Fr Francium

Highly multibranched gold nanostars were obtained by a room-temperature synthesis assisted by deep-eutectic solvents (DES). The concentration of the ascorbate ions and the presence of water in the solution were found to both have a profound influence on branch formation. A growth mechanism of the nanostar is therefore proposed from the analysis of the particle dimensions, the aspect ratio of their protuberances, and the gold crystal size. These spiky nanoparticles would find an application as conductive filler in polymeric piezoresistive composites, based on a tunneling conduction mechanism.

The dimension and morphology of gold nanostars, prepared through a room-temperature synthesis assisted by deep-eutectic solvents, can be tuned by varying the concentration of water and L-ascorbic acid. The obtained shapes fit with the requirements for the preparation of piezoresistive composites based on a tunneling conduction mechanism.

Hydroxyapatite (HAP) microspheres composed of nanorods have successfully been prepared by a facile co-precipitation method without any template. We propose the formation mechanism of the microspheres to be a four-step process on the basis of the evolution of their morphology as a function of reaction time. We investigate the competitive sorption of the HAP microspheres for Pb²⁺, Cu²⁺, Cd²⁺, Zn²⁺, and Ni²⁺ to show that HAP microspheres are a highly selective adsorbent for Pb²⁺ in wastewater.

Hierarchically structured microspheres self-assembled from hydroxyapatite nanorods have successfully been prepared by a simple co-precipitation method without any template. The as-prepared materials exhibit high selective adsorption for Pb²⁺ in wastewater.

Conflicting results have been reported with respect to the photoinduced switching of the magnetic properties of [Fe^III(salten)]⁺ complexes [salten = 4-azaheptamethylene-1,7-bis(salicylideneiminate)] coordinated by photoisomerizable ligands. In order to address this problem, two Fe^III complexes [Fe(salten)(3-azpy)]BPh₄ (1) and [Fe(salten)(4-azpy)]BPh₄ (2) have been synthesized and characterized by various physicochemical methods (azpy = phenylazopyridine). Both 1 and 2 exhibit a low spin (S = 1/2) to high spin (HS, S = 5/2) transition in the solid state. In solution at room temperature both complexes are predominantly HS. Upon exposure to 310 (trans → cis) and 440 nm radiation (cis → trans) the free and coordinated 3- and 4-azpy ligands undergo a reversible cis–trans isomerization. For 2 a corresponding reduction of the HS fraction 2 % is observed, whereas in 1 no effect is observed. Extensive DFT calculations, which employ different functionals and basis sets, explain this experimental result. The consequences of these findings with respect to the design of spin-switchable iron(III) complexes with photoactive ligands are discussed.

[Fe(salten)(3-azpy)]BPh₄ (1) and [Fe(salten)(4-azpy)]BPh₄ (2) have been synthesized and characterized [salten = 4-azaheptamethylene-1,7-bis(salicylideneiminate), azpy = phenylazopyridine]. Both exhibit a low to high spin transition in the solid state and are predominantly high spin in solution. cis–trans isomerization of coordinated azpy leaves their spin equilibria almost unaffected.

α- and γ-Fe₂O₃ nanorods have been prepared from a β-FeOOH precursor that was obtained by aqueous-phase precipitation of ferric chloride. The oxyhydroxide precursor had a rodlike shape with a diameter of 30–40 nm and a length of 400–500 nm. Calcination at 500 °C of the rod-shaped oxyhydroxide in air yielded α-Fe₂O₃ nanorods, whereas heating to reflux in polyethylene glycol (PEG) at 200 °C resulted in the formation of γ-Fe₂O₃ nanorods. Both oxides inherited the rodlike morphology of the precursor but exposed different crystalline facets. When being used to catalyze NO reduction by CO, an environmentally important reaction in NO abatement, the γ-Fe₂O₃ nanorods were much more active than the α-Fe₂O₃ nanorods and showed an apparent crystal-phase effect. This was because the γ-Fe₂O₃ nanorods simultaneously exposed iron and oxygen ions on their surfaces, which facilitated the adsorption and activation of NO and CO molecules.

α- and γ-Fe₂O₃ nanorods were obtained by proper dehydration of a rod-shaped β-FeOOH precursor. The Fe₂O₃ nanorods showed a distinct crystal-phase effect in the reduction of NO by CO on the basis of their exposed surface facets.

Heterobimetallic lithium–iron coordination compounds are interesting targets for several reasons: they can be used as precursors for mixed metal oxides, as catalysts, for example, for ring-opening polymerization reactions or to study oxidation/reduction processes. Finally their magnetic properties are also of interest. New heterobimetallic aryloxide complexes, namely [(thf)₄Li₃Fe(OPh)₃(O₂C₆H₄)Cl]₂ (1), [{(thf)₃Li₃Fe(OPh)₅Cl}₃]_n (2), and[(thf)₃Li₃Fe(OPh)₆]₂ (3), have been synthesized and characterized by single-crystal X-ray diffraction. While compounds 1 and 3 were synthesized by an oxidative substitution reaction, compound 2 was directly obtained from the Fe^III salt. These compounds are accessible by both synthetic pathways. Additionally, in compound 1, the phenoxy ligand was catalytically oxidized to ortho-catechol, which was incorporated into the structure of 1 as a ligand that coordinates strongly to iron. All compounds feature the Fe^III ion with a trigonal, bipyramidal environment, with coordination number 5.

Three new pentacoordinate Fe^III complexes, [(thf)₄Li₃Fe(OPh)₃(O₂C₆H₄)Cl]₂ (1), [{(thf)₃Li₃Fe(OPh)₅Cl}₃]_n (2), and [(thf)₃Li₃Fe(OPh)₆]₂ (3), two dinuclear, molecular species (1 and 3) and one trinuclear 1D coordination polymer, are reported. Compound 1 has a coordination sphere close to a square pyramid and might thus be useful for applications such as catalyst for the ring-opening polymerization of lactide.

Molecular imaging relies on the availability of imaging probes designed to modify their efficiency in the presence of a specific parameter, among which pH is one of the most investigated. Introduction of an aminoethyl moiety into the well-known DO3A platform imparts the desired pH sensitivity to the corresponding Gd³⁺ complex. The amine group is accessible and easy to functionalize; in particular, the possibility of tuning its pK_AH through N-substitution makes it a good pH-responsive functionality to access a novel class of tailored pH-sensitive MRI contrast agents. This was demonstrated by a relaxometric study on a functionalized Gd-DO3A complex bearing a simple primary amine group and comparison with the results of the corresponding N,N-dimethyl analogue.

Gd³⁺ complexes of aminoethyl-substituted DO3A show pH-sensitive behaviour with a relaxivity jump close to physiologically relevant pH values. The response to pH of this novel platform may be fine tuned by N-substitution.