Bromoplumbate mit kettenförmigen und isolierten Anionen: (Bzl4P)2[Pb3Br8], (Bzl4P)2[Pb3Br8(dmf)2], (Bzl4P)[PbBr3], (Bzl4P)2[PbBr4] und (Bzl4P)4[Pb2Br6][PbBr4]

Bromoplumbates with One‐dimensional Polymeric and Isolated Anions: (Bzl₄P)₂[Pb₃Br₈], (Bzl₄P)₂[Pb₃Br₈(dmf)₂], (Bzl₄P)[PbBr₃], (Bzl₄P)₂[PbBr₄], and (Bzl₄P)₄[Pb₂Br₆][PbBr₄] PbBr₂ reacts with LiBr and (Bzl₄P)(PF₆) (Bzl = CH₂C₆H₅) in acetone to form a series of bromoplumbate complexes with compositions and structures depending on the conditions of reaction and crystallization. While the anions in (Bzl₄P)₂[Pb₃Br₈] ( 1 ) and (Bzl₄P)[PbBr₃] ( 2 ) are one‐dimensional polymers with penta‐ and hexacoordinated Pb atoms, the metal atoms in the mono‐ and dinuclear complex anions of (Bzl₄P)₂[PbBr₄] · 2acetone ( 3 · 2acetone) and (Bzl₄P)₄[Pb₂Br₆][PbBr₄] ( 4 ) bind to four bromo ligands. From DMF as a solvent (Bzl₄P)₂[Pb₃Br₈(dmf)₂] ( 1 b ) crystallizes with the same bromoplumbate structure as in 1 a , but with dmf ligands occupying the coordination sites vacant in 1 a . Upon radiation of compound 3 with ultraviolet light greenish yellow photoluminescence (emssion maximum at 547 nm) is observed. Crystallographic details see “Inhaltsübersicht”.     

Symmetry‐Breaking Transitions in SmCu1+δAs2—χPχ(δ = 0 — 0.2, χ = 0 — 2). Effect of P and Additional Cu Atoms on Crystal Structures and Magnetic Properties

Crystal structures of the compounds SmCu_1+δAs_2—χP_χ (δ = 0 — 0.2, χ = 0 — 2) undergoing symmetry‐breaking transitions and SmCuP_2.3 have been investigated by the X‐ray single crystal and powder methods. While the phases SmCuAs₂ through SmCuAs_1.22P_0.78 retain the tetragonal HfCuSi₂ structure (P4/nmm space group), the compounds SmCuAs_1.11P_0.89 through SmCuAs_0.56P_1.44 adopt the GdCuAs_1.15P_0.85—type structure (Pmmn space group), an orthorhombic variant of the HfCuSi₂‐type. Further distortion follows in SmCuAs_0.33P_1.67 through SmCuP_2.3, the powder patterns of which were indexed in the P2/n space group (P2/c in a standard setting). According to Landau theory the transitions from tetragonal SmCuAs_1.22P_0.78 to orthorhombic SmCuAs_1.11P_0.89 and from orthorhombic SmCuAs_0.56P_1.44 to monoclinic SmCuAs_0.33P_1.67 can be continuous. Introducing extra copper into some of the orthorhombic arsenophosphides restabilizes tetragonal phases (0 < δ ≤ 0.2) with the P4/nmm symmetry, and the reverse transition Pmmn → P4/nmmcan be continuous. Inserting copper atoms into monoclinic SmCuP₂ yields the SmCu_1+δP₂ phosphides with Cmmm symmetry, and this transition is first‐order. Single crystals of SmCu_1.05As_1.67P_0.33, SmCu_1.07As_0.85P_1.15 and SmCu_1.15P₂ have been prepared using iodine as a mineralizing agent. Their structures have partially occupied Cu sites around the square As/P or P layers and they are a stuffed variant of the HfCuSi₂ structure for SmCu_1.05As_1.67P_0.33 (P4/nmm, a = 3.9163(6), c = 9.932(2)Å), a stuffed GdCuAs_1.15P_0.85 structure for SmCu_1.07As_0.85P_1.15 (Pmmn, a = 3.859(1), b = 3.862(1), c = 9.852(3)Å) and a CeCu_1.12P_1.97‐type structure for SmCu_1.15P₂ (Cmmm, a = 5.453(3), b = 19.511(10), c = 5.439(3)Å). The P net in SmCu_1.15P₂ is broken into rectangular units. The results of magnetic measurements for SmCuAsP are reported.     

Light Engineering and Silicon Diffractive Optics Assisted Nonparaxial Terahertz Imaging

The art of light engineering unveils a world of possibilities through the meticulous manipulation of photonic properties such as intensity, phase, and polarization. Precision control over these properties finds application in a variety of fields spanning communications, light–matter interactions, laser direct writing, and imaging. Terahertz (THz) range, nestled between microwaves and infrared light, stands out for its remarkable ability to propagate with minimal losses in numerous dielectric materials and compounds, making THz imaging a powerful tool for noninvasive control and inspection. In this study, a rational framework for the design and optimal assembly of nonparaxial THz imaging systems is established. The research is centered on lensless photonic systems composed solely of high-resistivity silicon-based nonparaxial elements such as the Fresnel zone plate, the Fibonacci lens, the Bessel axicon, and the Airy zone plate, all fabricated using laser ablation technology. Through a comprehensive examination through illumination engineering and scattered light collection from raster-scanned samples in a single-pixel detector scheme, the imaging systems are evaluated via diverse metrics including contrast, resolution, depth of field, and focus. These findings chart an exciting course toward the development of compact and user-friendly THz imaging systems where sensors and optical elements seamlessly integrate into a single chip.     

Conformational transitions in macromolecules of complex chemical structure during liquid crystalline ordering

Conformational transitions in thermotropic main-chain polymers of complex chemical structure including homopolymers with possibility of conformational transformations in mesogens and random copolymers (CPLs) containing mesogens of the same type and spacers of different lengths were investigated. It was demonstrated that liquid crystalline (LC) state influences conformational transformations in fragments of chain restraining them in comparison with an isotropic melt. It was found that CPLs studied form LC order of smectic type. Peculiarities in spacers behaviour during transition to LC state ensure formation of such type of LC order. Conclusion about dependence of mechanism of smectic LC order formation on chemical structure of rigid components of CPLs is made.     

Spin-wave eigenmodes of permalloy squares with a closure domain structure

Quantized spin-wave eigenmodes in single, 16 nm thick and 0.75 to 4 mum wide square permalloy islands with a fourfold closure domain structure have been investigated by microfocus Brillouin light scattering spectroscopy and time resolved scanning magneto-optical Kerr microscopy. Up to six eigenmodes were detected and classified. The main direction of the spin-wave quantization in the domains was found to be perpendicular to the local static magnetization. An additional less pronounced quantization along the direction parallel to the static magnetization was also observed.     

The alpha--> gamma transition in Ce: a theoretical view from optical spectroscopy

Using a novel approach to calculate optical properties of strongly correlated systems, we address the old question of the physical origin of the alpha--> gamma transition in Ce. We find that the Kondo collapse model, involving both the f and the spd electrons, describes the optical data better than a Mott transition picture involving the f electrons only. Our results compare well with existing experiments on thin films. We predict the full temperature dependence of the optical spectra and find the development of a hybridization pseudogap in the vicinity of the alpha--> gamma phase transition.     

Modular Construction of Fluoroarenes from a New Difluorinated Building Block by Cross‐Coupling/Electrocyclisation/Dehydrofluorination Reactions

Palladium‐catalysed coupling reactions based on a novel and easy‐to‐synthesise difluorinated organotrifluoroborate were used to assemble precursors to 6π‐electrocyclisations of three different types. Electrocyclisations took place at temperatures between 90 and 240 °C, depending on the central component of the π‐system; nonaromatic trienes were most reactive, but even systems that required the temporary dearomatisation of two arenyl subunits underwent electrocyclisation, albeit at elevated temperatures. Photochemical conditions were effective for these more demanding reactions. The package of methods delivered a structurally diverse set of fluorinated arenes, spanning a 20 kcal mol^?1 range of reactivity, by a flexible route.     

Two‐Step Spin Transition in a 1D FeII 1,2,4‐Triazole Chain Compound

A thermochromic 1D spin crossover coordination (SCO) polymer [Fe(βAlatrz)₃](BF₄)₂ ? 2 H₂O ( 1? 2 H₂O), whose precursor βAlatrz, (1,2,4‐triazol‐4‐yl‐propionate) has been tailored from a β‐amino acid ester is investigated in detail by a set of superconducting quantum interference device (SQUID), ⁵⁷Fe Mössbauer, differential scanning calorimetry, infrared, and Raman measurements. An hysteretic abrupt two‐step spin crossover (T_1/2^↓=230 K and T_1/2^↑=235 K, and T_1/2^↓=172 K and T_1/2^↑=188 K, respectively) is registered for the first time for a 1,2,4‐triazole‐based Fe^II 1D coordination polymer. The two‐step SCO configuration is observed in a 1:2 ratio of low‐spin/high‐spin in the intermediate phase for a 1D chain. The origin of the stepwise transition was attributed to a distribution of chains of different lengths in 1? 2 H₂O after First Order Reversal Curves (FORC) analyses. A detailed DFT analysis allowed us to propose the normal mode assignment of the Raman peaks in the low‐spin and high‐spin states of 1? 2 H₂O. Vibrational spectra of 1? 2 H₂O reveal that the BF₄^? anions and water molecules play no significant role on the vibrational properties of the [Fe(βAlatrz)₃]²⁺ polymeric chains, although non‐coordinated water molecules have a dramatic influence on the emergence of a step in the spin transition curve. The dehydrated material [Fe(βAlatrz)₃](BF₄)₂ ( 1 ) reveals indeed a significantly different magnetic behavior with a one‐step SCO which was also investigated.