Bis(formazanate)iron(II) complexes undergo a thermally induced S = 0 to S = 2 spin transition in solution. Here we present a study of how steric effects and π-stacking interactions between the triarylformazanate ligands affect the spin-crossover behavior, in addition to electronic substituent effects. Moreover, the effect of increasing the denticity of the formazanate ligands is explored by including additional OMe donors in the ligand ( 7 ). In total, six new compounds ( 2 – 7 ) have been synthesized and characterized, both in solution and in the solid state, via spectroscopic, magnetic, and structural analyses. The series spans a broad range of spin-crossover temperatures ( T 1/2 ) for the LS ⇌ HS equilibrium in solution, with the exception of compound 6 which remains high-spin ( S = 2) down to 210 K. In the solid state, 6 was shown to exist in two distinct forms: a tetrahedral high-spin complex ( 6a , S = 2) and a rare square-planar structure with an intermediate-spin state ( 6b , S = 1). SQUID measurements, 57 Fe Mössbauer spectroscopy, and differential scanning calorimetry indicate that in the solid state the square-planar form 6b undergoes an incomplete spin-change-coupled isomerization to tetrahedral 6a . The complex that contains additional OMe donors ( 7 ) results in a six-coordinate (NNO) 2 Fe coordination geometry, which shifts the spin-crossover to significantly higher temperatures ( T 1/2 = 444 K). The available experimental and computational data for 7 suggest that the Fe···OMe interaction is retained upon spin-crossover. Despite the difference in coordination environment, the weak OMe donors do not significantly alter the electronic structure or ligand-field splitting, and the occurrence of spin-crossover (similar to the compounds lacking the OMe groups) originates from a large degree of metal–ligand π-covalency.

Spray coating paper with plasmonic aggregates/hydroxyethylcellulose solution allows fabrication of cheap SERS active substrates for direct analysis of protein/mud samples.

A multilayer coating, with a different photochrome in each layer, enables predictable control over transmission and colour with a single wavelength of light, which is an important goal in functional optical materials and devices.

Renewable polysaccharide feedstocks are of interest in bio-based food packaging, coatings and hydrogels. Their physical properties often need to be tuned by chemical modification, e.g. by oxidation using periodate, to...

Renewable polysaccharide feedstocks are of interest in bio-based food packaging, coatings and hydrogels. Their physical properties often need to be tuned by chemical modification, e.g. by oxidation using periodate, to introduce carboxylic acid, ketone or aldehyde functional groups. The reproducibility required for application on an industrial scale, however, is challenged by uncertainty about the composition of product mixtures obtained and of the precise structural changes that the reaction with periodate induces. Here, we show that despite the structural diversity of gum arabic, primarily rhamnose and arabinose subunits undergo oxidation, whereas (inchain) galacturonic acids are unreactive towards periodate. Using model sugars, we show that periodate preferentially oxidises the anti 1,2-diols in the rhamnopyranoside monosaccharides present as terminal groups in the biopolymer. While formally oxidation of vicinal diols results in the formation of two aldehyde groups, only traces of aldehydes are observed in solution, with the main final products obtained being substituted dioxanes, both in solution and in the solid state. The substituted dioxanes form most likely by the intramolecular reaction of one aldehyde with a nearby hydroxyl group, followed by hydration of the remaining aldehyde to form a geminal diol. The absence of significant amounts of aldehyde functional groups in the modified polymer impacts crosslinking strategies currently attempted in the preparation of renewable polysaccharide-based materials.