Near-Infrared Light-Induced Spin-State Switching Based on Fe(II)-Hg(II) Spin-Crossover Network.

The development of molecular switches with tunable properties has garnered considerable interest over several decades. A novel spin-crossover (SCO) material based on iron(II) complexes incorporating 4-acetylpyridine (4-acpy) and [Hg(SCN)] anions was synthesized and formulated as [Fe(4-acpy)][Hg(μ-SCN)] (1). Compound 1 is crystallized in a three-dimensional network in the non-centrosymmetric orthorhombic space group Pna2 with two octahedral [Fe(4-acpy)(NCS)] entities featuring two distinct Fe centers (Fe1 and Fe2).

Thermal Bistability of Magnetic Susceptibility, Light Absorption, Second Harmonic Generation, and Dielectric Properties in a Polar Spin-Crossover Iron-Rhenium Chain Material.

The bistability of multiple physical properties driven by external stimuli in a solid is a desired prerequisite for its application in memory devices with convenient data readout. We present a pathway for thermal bistability detectable in four physical properties: magnetic, light absorption, second-harmonic generation (SHG), and dielectric. We report a novel heterometallic (TBA){[Fe(phIN)][Re(CN)]} ⋅ (phIN) (1) (TBA=tetrabutylammonium cation, phIN=phenyl isonicotinate) cyanido-bridged chain material.

A mononuclear Fe(III) complex showing thermally induced spin crossover and slow magnetic relaxation with reciprocating thermal behaviour.

AC susceptibility measurements of [Fe(L)(NCSe)] reveal a field supported slow magnetic relaxation. On cooling, the relaxation time of the high-frequency fraction decreases which is a sign of reciprocating thermal behaviour. The relaxation time for the low-frequency mode at = 2.

Pressing of Functionalized Polymer Composite Materials to Improve Mössbauer Measurement Signals.

Coordination compounds, like iron(II) triazole complexes, exhibit spin crossover (SCO) behavior at around room temperature. Therefore, they are interesting for a variety of possible applications, and it is convenient to integrate them into polymers. Due to a reduction of the iron content and thus also Fe content in the sample through integration in polymers, Mössbauer measurements are only possible with greater difficulty or very long measurement times without expensive enrichment of the samples with Fe.

Investigation of the molecular switching process between spin crossover states of triazole complexes as basis for optical sensing applications.

With the advent of the first laser sources and suitable detectors, optical sensor applications immediately also came into focus. During the last decades, a huge variety of optical sensor concepts were developed, yet the forecast for the future application potential appears even larger. In this context, the development of new sensor probes at different scales down to the atomic or molecular level open new avenues for research and development.

Development of a Novel Passive Monitoring Technique to Showcase the 3D Distribution of Tritiated Water (HTO) Vapor in Indoor Air of a Nuclear Facility.

Tritiated water (HTO), a ubiquitous byproduct of the nuclear industry, is a radioactive contaminant of major concern for environmental authorities. Although understanding spatiotemporal heterogeneity of airborne HTO vapor holds great importance for radiological safety as well as diagnosing a reactor's status, comprehensive HTO distribution dynamics inside nuclear facilities has not been studied routinely yet due to a lack of appropriate monitoring techniques. For current systems, it is difficult to simultaneously achieve high representativeness, sensitivity, and spatial resolution.

Incorporation and Deposition of Spin Crossover Materials into and onto Electrospun Nanofibers.

We synthesized iron(II)-triazole spin crossover compounds of the type [Fe(atrz)]X and incorporated and deposited them on electrospun polymer nanofibers. For this, we used two separate electrospinning methods with the goal of obtaining polymer complex composites with intact switching properties. In view of possible applications, we chose iron(II)-triazole-complexes that are known to exhibit spin crossover close to ambient temperature.

Untangling the intertwined: metallic to semiconducting phase transition of colloidal MoS nanoplatelets and nanosheets.

2D semiconducting transition metal dichalcogenides (TMDCs) are highly promising materials for future spin- and valleytronic applications and exhibit an ultrafast response to external (optical) stimuli which is essential for optoelectronics. Colloidal nanochemistry on the other hand is an emerging alternative for the synthesis of 2D TMDC nanosheet (NS) ensembles, allowing for the control of the reaction tunable precursor and ligand chemistry. Up to now, wet-chemical colloidal syntheses yielded intertwined/agglomerated NSs with a large lateral size.

Development and calibration of a modifiable passive sampler for monitoring atmospheric tritiated water vapor in different environments.

Anthropogenic release of tritium from nuclear facilities is expected to increase significantly in the coming decades, which may cause radiation exposure to humans through the contamination of water and food chains. It is necessary and urgent to acquire detailed information about tritium in various environments for studying its behavior and assessing the potential radiation risk. In the atmosphere, although the passive sampling technique provides a low-cost and convenient way to characterize the dynamics of tritiated water vapor (HTO), a single, simple sampler configuration makes it difficult to collect sufficient and representative samples within the expected period from different environments.

Second harmonic generation on chiral cyanido-bridged Fe-Nb spin-crossover complexes.

Incorporating chiral organic ligands into cyanido-bridged FeII-NbIV assemblies synthesized chiral spin-crossover complexes, FeII2[NbIV(CN)8](L)8·6H2O (L = R-, S-, or rac-1-(3-pyridyl)ethanol: R-FeNb, S-FeNb, or rac-FeNb). Rietveld analyses based on a racemic complex of rac-FeNb indicate that the chiral complexes have a cubic crystal structure in the I213 space group with a three-dimensional cyanido-bridged FeII-NbIV coordination network. All the complexes exhibit spin crossover between the high-spin (HS) and the low-spin (LS) FeII states without thermal hysteresis.

Polymer Optical Waveguide Sensor Based on Fe-Amino-Triazole Complex Molecular Switches.

We report on a polymer-waveguide-based temperature sensing system relying on switchable molecular complexes. The polymer waveguide cladding is fabricated using a maskless lithographic optical system and replicated onto polymer material (i.e.

Spin-crossover in an iron(III) complex showing a broad thermal hysteresis.

A pentadentate Schiff-base ligand 3,5Cl-L2- and NCSe- form an iron(iii) mononuclear complex, namely [Fe(3,5Cl-L)(NCSe)], which shows a thermally induced spin crossover with a broad hysteresis width of 24 K between 123 K (warming) and 99 K (cooling). Analogous complexes of the [Fe(3,5X-L)(Y)] type, where X = Cl or Br and Y = Cl-, N3-, NCS-, and NCSe-, are high-spin over the whole temperature interval.

Slow magnetic relaxation in a high-spin pentacoordinate Fe(iii) complex.

A mononuclear pentacoordinate iron(iii) complex shows slow magnetic relaxation with three relaxation channels. The high-frequency relaxation time of the order of microseconds is prolonged on cooling in accordance with the direct and Raman processes. The low frequency relaxation time is little dependent on temperature and varies in the range τ(LF) = 0.

Solid-State Hydrogen-Bond Alterations in a [Co Fe ] Complex with Bifunctional Hydrogen-Bonding Donors.

A hydrogen-bonding donor-acceptor system, [Co Fe (bpy*) (CN) (tp*) ](PF ) ⋅2ABA⋅4BN⋅2PE (1 s ), was prepared by co-crystallization of an external stimuli-responsive cyanide-bridged tetranuclear [Co Fe ] complex and bifunctional hydrogen-bonding donors, p-aminobenzoic acid. Compound 1 s exhibited a gradual electron-transfer-coupled spin transition (ETCST), and the removal of solvent molecules led to an abrupt thermal ETCST behavior with increased transition temperature. X-ray structural analysis revealed that the modification of ETCST was caused by a significant alteration of a hydrogen-bonding mode between the tetranuclear [Co Fe ] cations and ABA molecules.

A Brønsted-Ligand-Based Iron Complex as a Molecular Switch with Five Accessible States.

A mononuclear Fe complex, prepared with a Brønsted diacid ligand, H L (H L=2-[5-phenyl-1H-pyrazole-3-yl] 6-benzimidazole pyridine), shows switchable physical properties and was isolated in five different electronic states. The spin crossover (SCO) complex, [Fe (H L) ](BF ) (1 ), exhibits abrupt spin transition at T =258 K, and treatment with base yields a deprotonated analogue [Fe (HL) ] (1 ), which shows gradual SCO above 350 K. A range of Fe analogues were also characterized.

Effect of the degree of inversion on optical properties of spinel ZnFeO.

Spinel ferrites (T[M1-xFex]O[MxFe2-x]O4 with 0 ≤ x ≤ 1, where M is a bivalent metal ion and the superscripts denote tetrahedral and octahedral sites) are materials commonly used in electronics due to their outstanding magnetic properties. Thus, the effect of the degree of inversion, x, on these properties is well known. However, its effect on other properties of these materials has rarely been investigated in detail.

Mixture of PLA-PEG and biotinylated albumin enables immobilization of avidins on electrospun fibers.

The application of nanotechnology in biomedical field has enormous potential in basic and applied research. Micro or nanofibers produced by electrospinning technique offer excellent properties because of large specific surface area, high porosity, and ability to incorporate functional additives. Here we embedded biotinylated bovine serum albumin into polylactic acid (PLA)-polyethylene glycol (PEG) fibers, which enabled specific immobilization of fluorescently labelled avidin.

Spin state switching of metal complexes by visible light or hard X-rays.

Electromagnetic stimuli of spin crossover compounds restricted to UV-vis light irradiation for many years could be recently extended to X-ray excitation. This review covers a large variety of light-induced effects, as well as recent analogues stimulated by X-ray irradiation which have not yet been reviewed. The focus is also on multistable multinuclear spin crossover compounds which are the subject of lively discussions within the spin crossover community.

Simultaneous cancer control and diagnosis with magnetic nanohybrid materials.

Coated magnetite nanoparticles were linked to (68)Ga complexes used in the positron emission tomography (PET) for a new technical approach to detect cancer tissue with radiopharmaceuticals. By substitution of the Ga isotope with an alpha emitter the same compound could be used for cancer treatment. Furthermore the nanoparticles were connected to pH-sensitive complexes, enabling a pH-controlled assembly/disassembly and therefore the spreading of the particles in the tissue.

[Fe19 ] "Super-Lindqvist" Aggregate and Large 3D Interpenetrating Coordination Polymer from Solvothermal Reactions of [Fe2 (OtBu)6 ] with Ethanol.

The syntheses, crystal structures, and physical properties of [HFe19 O14 (OEt)30 ] and {Fe11 (OEt)24 }∞ are reported. [HFe19 O14 (OEt)30 ] has an octahedral shape. Its core with a central Fe metal ion surrounded by six μ6 -oxo ligands is arranged in the rock salt structure.

Mixed-valence heptanuclear iron complexes with ferromagnetic interaction.

Three new Prussian blue analogues, heptanuclear mixed-valence iron complexes of the type [Fe(II)(CN)(6){Fe(III)(1(-2H))}(6)]Cl(2)·nH(2)O, were synthesized and structurally and spectrally characterized, and their magnetic properties were investigated (1(-2H) corresponds to doubly deprotoned Schiff-base pentadentate ligands 1a, N,N'-bis(2-hydroxybenzylidene)-1,5-diamino-3-azapentane, 1b, N,N'-bis(3-ethoxy-2-hydroxybenzylidene)-1,7-diamino-4-azaheptane, or 1c, N,N'-bis(3-methoxy-2-hydroxybenzylidene)-1,6-diamino-3-azahexane). These compounds were formed by assembling the [Fe(CN)(6)](4-) building block with mononuclear complexes of the [Fe(1(-2H))Cl] type. X-ray structure analysis revealed that the complexes adopt a star-like architecture: the Fe(II) ion lies at the very center, and on its octahedral nodes the Fe(III) sites are coordinated in the Fe(II)-C≡N-Fe(III) manner.

A rectangular Ni-Fe cluster with unusual cyanide bridges.

An asymmetric polycyanide iron complex, K(2)[Fe(III)(L1)(CN)(4)](MeOH) (HL1 = 2,2'-(1H-pyrazole-3,5-diyl)bis-pyridine), was synthesized and its complexation compatibility with nickel ions was examined. Two kinds of enantiomeric nickel-iron squares were obtained in the presence of a chiral bidentate capping ligand. The compounds display unusual cyanide bridge geometry and have ferromagnetic interactions between nickel and iron ions.

Assessing p-glycoprotein (Pgp) activity in vivo utilizing 68Ga-Schiff base complexes.

Purpose: The p-glycoprotein (Pgp) is the most prominent member of active drug transporters leading to a multidrug-resistant phenotype. For identification of tumors functionally overexpressing Pgp in vivo, non-invasive imaging techniques are needed.

Procedures: Six Schiff base compounds were synthesized and labeled with (68)Ge/(68)Ga generator-derived (68)Ga.

Spin crossover in a heptanuclear mixed-valence iron complex.

The complex [Fe(II){(CN)Fe(III)L(5)}(6)]Cl(2) consists of a mixed-valence heptanuclear cyanide-bridged unit formed of a Schiff-base pentadentate ligand L(5) and it shows a spin crossover of the peripheral Fe(III) centres.