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Polycrystalline [FeL 2 ][BF 4 ] 2 (L=2,6-di(pyrazol-1-yl)isonicotinonitrile) exhibits an abrupt hysteretic spin transition near 240 K, with a shoulder on the warming branch whose appearance depends on the sample history. The freshly isolated material is a ca 60 : 40 mixture of triclinic (HS1) and tetragonal (HS2) high-spin polymorphs, which are structurally closely related. Both HS1 and HS2 undergo a high→low-spin transition on cooling at 230±10 K. HS1 transforms to a new triclinic low-spin phase with a doubled unit cell volume (LS3), while HS2 forms a monoclinic low-spin phase (LS4) with similar unit cell dimensions to HS2. Single crystals of LS3 and LS4 both convert to HS1 on rewarming. The low→high-spin transition for LS4 is ca 10 K higher in temperature than for LS3, explaining the asymmetric thermal hysteresis. Powder diffraction, calorimetry and magnetic data show that multiple cycling about the spin-transition leads to slow enrichment of the HS1 and LS3 phases at the expense of HS2 and LS4. That is consistent with the HS2/LS4 fraction of the polycrystalline sample undergoing rare, bifurcated HS2→(LS3+LS4) and LS4→(HS1+HS2) phase transitions. The rate of enrichment of HS1/LS3 differed between these experiments, implying it is sample and/or measurement-dependent. Three other salts of this iron(II) complex and the coordination polymer [Ag(μ-L)]BF 4 are also briefly described., (© 2024 The Author(s). Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Extraskeletal myxoid chondrosarcoma (EMC) is an uncommon mesenchymal neoplasm characteristically composed of uniform-appearing round to spindle-shaped cells with eosinophilic cytoplasm and abundant myxoid extracellular matrix. Although the majority of cases harbor a pathognomonic t(9;22) translocation that fuses EWSR1 with the orphan nuclear receptor NR4A3, there are less common variants that partner NR4A3 with TAF15, TCF12, or TFG. By immunohistochemistry, EMC has features of both cartilaginous and neuroendocrine differentiation, as evidenced by inconsistent expression of S100 protein and synaptophysin or INSM1, respectively, in a subset of cases. Given the limitations of available immunohistochemical stains for the diagnosis of EMC, we analyzed genome-wide gene expression microarray data to identify candidate biomarkers based on differential expression in EMC in comparison with other mesenchymal neoplasms. This analysis pointed to CHRNA6 as the gene with the highest relative expression in EMC (96-fold; P = 8.2 × 10 -26 ) and the only gene with >50-fold increased expression in EMC compared with other tumors. Using RNA chromogenic in situ hybridization, we observed strong and diffuse expression of CHRNA6 in 25 cases of EMC, including both EWSR1-rearranged and TAF15-rearranged variants. All examined cases of histologic mimics were negative for CHRNA6 overexpression; however, limited CHRNA6 expression, not reaching a threshold of >5 puncta or 1 aggregate of chromogen in >25% of cells, was observed in 69 of 685 mimics (10.1%), spanning an array of mesenchymal tumors. Taken together, these findings suggest that, with careful interpretation and the use of appropriate thresholds, CHRNA6 RNA chromogenic in situ hybridization is a potentially useful ancillary histologic tool for the diagnosis of EMC., (Copyright © 2024 United States & Canadian Academy of Pathology. Published by Elsevier Inc. All rights reserved.)

[Fe(bpp) 2 ][ClO 4 ] 2 (bpp = 2,6-bis{pyrazol-1-yl}pyridine; monoclinic, C 2/ c ) is high-spin between 5-300 K, and crystallises with a highly distorted molecular geometry that lies along the octahedral-trigonal prismatic distortion pathway. In contrast, [Ni(bpp) 2 ][ClO 4 ] 2 (monoclinic, P 2 1 ) adopts a more regular, near-octahedral coordination geometry. Gas phase DFT minimisations (ω-B97X-D/6-311G**) of [M(bpp) 2 ] 2+ complexes show the energy penalty associated with that coordination geometry distortion runs as M 2+ = Fe 2+ (HS) ≈ Mn 2+ (HS) < Zn 2+ ≈ Co 2+ (HS) ≲ Cu 2+ ≪ Ni 2+ ≪ Ru 2+ (LS; HS = high-spin, LS = low-spin). Slowly crystallised solid solutions [Fe x Ni 1- x (bpp) 2 ][ClO 4 ] 2 with x = 0.53 (1a) and 0.74 (2a) adopt the P 2 1 lattice, while x = 0.87 (3a) and 0.94 (4a) are mixed-phase materials with the high-spin C 2/ c phase as the major component. These materials exhibit thermal spin-transitions at T ½ = 250 ± 1 K which occurs gradually in 1a, and abruptly and with narrow thermal hysteresis in 2a-4a. The transition proceeds to 100% completeness in 1a and 2a; that is, the 26% Ni doping in 2a is enough to convert high-spin [Fe(bpp) 2 ][ClO 4 ] 2 into a cooperative, fully SCO-active material. These results were confirmed crystallographically for 1a and 2a, which revealed similarities and differences between these materials and the previously published [Fe x Ni 1- x (bpp) 2 ][BF 4 ] 2 series. Rapidly precipitated powders with the same compositions (1b-4b) mostly resemble 1a-4a, except that 2b is a mixed-phase material; 2b-4b also contain a fraction of amorphous solid in addition to the two crystal phases. The largest iron fraction that can be accommodated by the P 2 1 phase in this system is 0.7 ± 0.1.

Four bis[2-{pyrazol-1-yl}-6-{pyrazol-3-yl}pyridine] ligands have been synthesized, with butane-1,4-diyl (L 1 ), pyrid-2,6-diyl (L 2 ), benzene-1,2-dimethylenyl (L 3 ) and propane-1,3-diyl (L 4 ) linkers between the tridentate metal-binding domains. L 1 and L 2 form [Fe 2 (μ-L) 2 ]X 4 (X - =BF 4 - or ClO 4 - ) helicate complexes when treated with the appropriate iron(II) precursor. Solvate crystals of [Fe 2 (μ-L 1 ) 2 ][BF 4 ] 4 exhibit three different helicate conformations, which differ in the torsions of their butanediyl linker groups. The solvates exhibit gradual thermal spin-crossover, with examples of stepwise switching and partial spin-crossover to a low-temperature mixed-spin form. Salts of [Fe 2 (μ-L 2 ) 2 ] 4+ are high-spin, which reflects their highly twisted iron coordination geometry. The composition and dynamics of assembly structures formed by iron(II) with L 1 -L 3 vary with the ligand linker group, by mass spectrometry and 1 H NMR spectroscopy. Gas-phase DFT calculations imply the butanediyl linker conformation in [Fe 2 (μ-L 1 ) 2 ] 4+ influences its spin state properties, but show anomalies attributed to intramolecular electrostatic repulsion between the iron atoms., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The opportunity to create different patterns of magnetic nanoparticles on surfaces is highly desirable across many technological and biomedical applications. In this paper, this ability is demonstrated for the first time using a computer-controlled aerosol jet printing (AJP) technology. AJP is an emerging digitally driven, non-contact and mask-less printing process which has distinguishing advantages over other patterning technologies as it offers high-resolution and versatile direct-write deposition of a wide range of materials onto a variety of substrates. This research demonstrates the ability of AJP to reliably print large-area, fine-feature patterns of superparamagnetic iron oxide nanoparticles (SPIONs) onto both rigid material (glass) and soft and flexible materials (polydimethylsiloxane (PDMS) films and poly-L-lactic acid (PLLA) nanofilms). Investigation identified and controlled influential process variables which permitted feature sizes in the region of 20 μm to be realised. This method could be employed for a wide range of applications that require a flexible and responsive process that permits high yield and rapid patterning of magnetic material over large areas. As a first proof of concept, we present patterned magnetic nanofilms with enhanced manipulability under external magnetic field gradient control and which are capable of performing complex movements such as rotation and bending, with applicability to soft robotics and biomedical engineering applications., (© 2022. The Author(s).)

Complexation of Fe[ClO 4 ] 2 ·6H 2 O by 1 equiv. 2,6-bis((4 S )-4-phenyl-4,5-dihydrooxazol-2-yl)pyridine (( S )-L 1 Ph) and 2,6-bis((4 R )-4-phenyl-4,5-dihydrothiazol-2-yl)pyridine (( R )-L 2 Ph) cleanly affords [Fe(( S )-L 1 Ph)(( R )-L 2 Ph)][ClO 4 ] 2 ; [Fe(( R )-L 1 iPr)(( S )-L 2 iPr)][ClO 4 ] 2 (L 1 iPr = 2,6-bis(4-isopropyl-4,5-dihydrooxazol-2-yl)pyridine; L 2 iPr = 2,6-bis(4-isopropyl-4,5-dihydrothiazol-2-yl)pyridine) was prepared by a similar route. The compounds exhibit thermal spin-crossover in solution, at temperatures midway between the corresponding [Fe(( R )-L 1 R)(( S )-L 1 R)][ClO 4 ] 2 and [Fe(( R )-L 2 R)(( S )-L 2 R)][ClO 4 ] 2 (R = Ph or iPr) species. The spin states of [Fe(LR)(bimpy)][ClO 4 ] 2 and [Fe(LR)(bpp)][ClO 4 ] 2 (LR = L 1 R or L 2 R; bimpy = 2,6-bis(1 H -benzimidazol-2-yl)pyridine; bpp = 2,6-di(pyrazol-1-yl)pyridine) are also reported, with most examples exhibiting gradual spin-crossover in solution and the solid state. Although some products undergo partial ligand exchange in solution by 1 H NMR, their solution T ½ values appear unaffected by this and correlate well with their spin state energies from gas phase DFT calculations. The high-spin state of [Fe(L 2 R)(bpp)] 2+ is more stabilised than expected, compared to the other [Fe(LR)L] 2+ complexes studied (L = bimpy, bpp or terpy). That is explained by an interplay between the relative σ-basicities and π-acidities of the two ligands in each molecule. The steric influence of their phenyl or isopropyl 'R' substituents stabilises the heteroleptic complexes by up to 5 kcal mol -1 , compared to analogues lacking these groups.

The complex salts [Fe( L 1 ) 2 ]X 2 ( 1X 2 ; L 1 = 4-(isopropyldisulfanyl)-2,6-bis(pyrazolyl)pyridine; X - = BF 4 - , ClO 4 - ) form solvated crystals from common organic solvents. Crystals of 1X 2 ·Me 2 CO show abrupt spin transitions near 160 K, with up to 22 K thermal hysteresis. 1X 2 ·Me 2 CO cocrystallizes with other, less cooperative acetone solvates, which all transform into the same solvent-free materials 1X 2 ·sf upon exposure to air, or mild heating. Conversion of 1X 2 ·Me 2 CO to 1X 2 ·sf proceeds in a single-crystal to single-crystal fashion. 1X 2 ·sf are not isomorphous with the acetone solvates, and exhibit abrupt spin transitions at low temperature with hysteresis loops of 30-38 K (X - O are mostly isomorphous with each other and show more gradual spin-crossover equilibria near room temperature. All three of these lattice types have similar unit cell dimensions and contain cations associated into chains through pairwise, intermolecular S···π interactions. Polycrystalline [Fe( 4 - ) and 10-20 K (X - = ClO 4 - ), depending on the measurement method. Interestingly, the desolvation has an opposite effect on the SCO temperature and hysteresis in the two salts. The hysteretic spin transitions in 1X 2 ·Me 2 CO and 1X 2 ·sf do not involve a crystallographic phase change but are accompanied by a significant rearrangement of the metal coordination sphere. Other solvates 1X 2 ·MeNO 2 , 1X 2 ·MeCN, and 1X 2 ·H 2 O are mostly isomorphous with each other and show more gradual spin-crossover equilibria near room temperature. All three of these lattice types have similar unit cell dimensions and contain cations associated into chains through pairwise, intermolecular S···π interactions. Polycrystalline [Fe( L 2 ) 2 ][BF 4 ] 2 ·MeNO 2 ( 2[BF 4 ] 2 ·MeNO 2 ; L 2 = 4-(methyldisulfanyl)-2,6-bis(pyrazolyl)pyridine) shows an abrupt spin transition just above room temperature, with an unsymmetrical and structured hysteresis loop, whose main features are reversible upon repeated thermal scanning., Competing Interests: The authors declare no competing financial interest., (© 2022 American Chemical Society.)