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Nitride (N 3- ) or cyanamide (CN 2 2- ) based mixed-anion compounds stand as attractive materials due to their unique properties derived from the binary or multiple anions, although their synthesis remains challenging in incorporating the N 3- or CN 2 2- anions safely. This work highlights the first demonstration of in situ single phase formation of a LaCl(CN 2 ) mixed-anion compound from a stable single source precursor, melamine modified with LaCl 3 preparable under aqueous conditions. The in situ formation of LaCl(CN 2 ) involves the chemical modification of melamine with LaCl 3 to form a complex. Upon heating of the precursor under N 2 flowing, this complex generates cyanamide species around 400 °C, which react with LaCl 3 and nonsublimated melamine to afford a binary LaCl(CN 2 )/g-C 3 N 4 composite. Further pyrolysis at 800 °C decomposes the g-C 3 N 4 counterpart, resulting in the LaCl(CN 2 ) single-phase formation. The electronic properties of the precursor-derived single phase LaCl(CN 2 ) were studied by the density functional theory calculation and UV-vis spectroscopy combined with X-ray photoelectron spectroscopy analyses and characterized by measuring 4.7, 1.8, and -2.9 eV for the band gap energy, the valence band maximum, and the conduction band minimum relative to Fermi energy, respectively. This study paves the way for exploring various cyanamide-based mixed anion compounds, advancing their potential applications in various fields.

Recent advances in "hybrid-improper" ferroelectricity in Dion-Jacobson (DJ)-type layered perovskites have caused renewed interest in the search for new ferroelectrics. Here, we present an approach for the tailored synthesis of a new homologous series of DJ-type layered perovskites Cs(Bi 2 Sr n -3 )(Ti n -1 Nb)O 3 n +1 . Starting from CsBi 2 Ti 2 NbO 10 ( n = 3), higher-order homologous phases with n = 4 and 5 were successfully synthesized by repeated solid-state calcination with SrTiO 3 . Characterizations by X-ray diffraction, electron diffraction, transmission electron microscopy, Raman scattering, and second harmonic generation showed the detailed structural features in Cs(Bi 2 Sr n -3 )(Ti n -1 Nb)O 3 n +1 , and the polar structures could be stabilized by proper or hybrid-improper ferroelectricity, depending on the odd or even number of the perovskite layers. Our results provide important insights into the competition between the different mechanisms and the consequences of the ferroelectric properties in homologous layered perovskites.

Molybdenum carbides (MoC and Mo 2 C) are being reported for various applications, for example, catalysts for sustainable energies, nonlinear materials for laser applications, protective coatings for improving tribological performance, and so on. A one-step method for simultaneously fabricating molybdenum monocarbide (MoC) nanoparticles (NPs) and MoC surfaces with a laser-induced periodic surface structure (LIPSS) was developed by using pulsed laser ablation of a molybdenum (Mo) substrate in hexane. Spherical NPs with an average diameter of 61 nm were observed by scanning electron microscopy. The X-ray diffraction pattern and electron diffraction (ED) pattern results indicate that a face-centered cubic MoC was successfully synthesized for the NPs and on the laser-irradiated area. Notably, the ED pattern suggests that the observed NPs are nanosized single crystals, and a carbon shell was observed on the surface of MoC NPs. The X-ray diffraction pattern of both MoC NPs and LIPSS surface indicates the formation of FCC MoC, agreeing with the results of ED. The results of X-ray photoelectron spectroscopy also showed the bonding energy attributed to Mo-C, and the sp 2 -sp 3 transition was confirmed on the LIPSS surface. The results of Raman spectroscopy have also supported the formation of MoC and amorphous carbon structures. This simple synthesis method for MoC may provide new possibilities for preparing Mo x C-based devices and nanomaterials, which may contribute to the development of catalytic, photonic, and tribological fields., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Ferrochiral transition, i.e., a transition involving an emergence of chirality, provides an unique opportunity to achieve a nonvolatile reversible control of chirality with external fields. However, materials showing pure ferrochiral transitions, which are accompanied by no other types of ferroic transition, are exceedingly rare. In this study, we propose that a pure ferrochiral transition is achieved by a combination of antipolar and antiferroaxial orderings of structural units, and substantiate this proposal through a study of the chiral compound Ba(TiO)Cu 4 (PO 4 ) 4 . Single crystal X-ray diffraction measurements have revealed that this material undergoes a second order ferrochiral transition whose order parameter is described by an antiferroaxial (staggered) rotation of antipolar structural units, thus demonstrating our proposal. Furthermore, by measuring spatial distributions of optical rotation, we successfully visualized a temperature evolution of ferrochiral domains across the transition temperature and demonstrated the relationship between chirality and optical rotation. This work provides a guide to find a pure ferrochiral transition, thus providing an opportunity to achieve a ferroic control of chirality.

We report the successful synthesis, crystal structure, and electrical properties of Sr 3 Re 2 O 9 , which contains Re 6+ with the 5d 1 configuration. This compound is isostructural with Ba 3 Re 2 O 9 and shows a first-order structural phase transition at ∼370 K. The low-temperature (LT) phase crystallizes in a hettotype structure of Ba 3 Re 2 O 9 , which is different from that of the LT phase of Sr 3 W 2 O 9 , suggesting that the electronic state of Re 6+ plays an important role in determining the crystal structure of the LT phase. The structural transition is accompanied by a sharp change in the electrical resistivity. This is likely a metal-insulator transition, as suggested by the electronic band calculation and magnetic susceptibility. In the LT phase, the ReO 6 octahedra are rotated in a pseudo- a 0 a 0 a + manner in Glazer notation, which corresponds to C -type orbital ordering. Paramagnetic dipole moments were confirmed to exist in the LT phase by muon spin rotation and relaxation measurements. However, the dipole moments shrink greatly because of the strong spin-orbit coupling in the Re ions. Thus, the electronic state of the LT phase corresponds to a Mott insulating state with strong spin-orbit interactions at the Re sites.

Quasi-zero-dimensional antiferromagnets with weakly coupled clusters of multiple spins can provide an excellent platform for exploring exotic quantum states of matter. Here, we report the synthesis and the characterization of a copper-based insulating antiferromagnet, K(NbO)Cu 4 (PO 4 ) 4 . Single-crystal X-ray diffraction measurements reveal that the crystal structure belongs to the tetragonal space group P 4/ nmm , in which Cu 2+ ions align to form a quasi-two-dimensional layer of spin-1/2 coupled square tetramers. The structure is quasi-isostructural to recently reported magnetoelectric antiferromagnets, A (TiO)Cu 4 (PO 4 ) 4 ( A = Ba, Sr, and Pb) with the P 42 1 2 space group. Despite their structural similarities, whereas the antiferromagnetic transition in A (TiO)Cu 4 (PO 4 ) 4 produces conventional anomalies in magnetization and heat capacity, that in K(NbO)Cu 4 (PO 4 ) 4 has several unusual features such as an upturn in magnetic susceptibility and a very weak specific heat anomaly that corresponds to a spin entropy release as small as 3%. These results indicate that the magnetism of K(NbO)Cu 4 (PO 4 ) 4 is far different from that of A (TiO)Cu 4 (PO 4 ) 4 and suggest that the ground state is very close to a quantum nonmagnetic singlet state. The origin of the distinct magnetism in K(NbO)Cu 4 (PO 4 ) 4 is discussed in terms of structural modifications of a Cu 4 O 12 unit forming a square tetramer. Our study demonstrates that the present material family, represented by an extended chemical formula A ( B O)Cu 4 (PO 4 ) 4 ( AB = KNb, BaTi, SrTi, and PbTi), has broad chemical controllability of their magnetism. This makes this system an attractive material platform to study the physics of quantum spin-1/2 coupled square tetramers.

We have for the first time clarified the incommensurately modulated crystal structure as well as the photoluminescence properties of Eu 2+ -activated Ca 2 SiO 4 solid solution, the chemical formula of which is (Ca 1.88 Eu 2+ 0.01 □ 0.11 )(Si 0.78 P 0.22 )O 4 , where □ denotes vacancies in Ca sites with the replacement of Si 4+ by P 5+ . The emission spectrum upon the 335 nm excitation showed a relatively broad band centered at ca. 490 nm and a full width at half-maximum of ca. 80 nm. The crystal structure was made up of the four types of β-Ca 2 SiO 4 -like layers with one type of interlayer. The incommensurate modulation with superspace group Pnma(0 β 0)00 s was induced by the long-range stacking order of these layers. The modulation wavevector was 0.27404(2) × b*, with the basic unit-cell dimensions being a = 0.68355(2) nm, b = 0.54227(2) nm, and c = 0.93840(3) nm ( Z = 4). The basic structure contained two nonequivalent Ca sites. One site was fully occupied by Ca 2+ and free from Eu 2+ in the overall incommensurate structure. The occupational modulation at the other site was so significant that the sum of site occupation factors for Ca 2+ and Eu 2+ as low as 0.5 was seen at the interlayer. This site was too large for accommodation of Ca 2+ but was suitable for Eu 2+ . Thus, the Eu 2+ ions would exclusively concentrate at the relevant site, which would cause the emission peak of the incommensurate phase to be shifted to the shorter wavelength ranges as compared with those of the other commensurate phases such as β and α' L .

A new polymorphism of Ba 3 W 2 O 9 is discovered with the use of a high-pressure synthesis technique and its crystal structure is determined by single-crystal X-ray diffraction and transmission electron microscopy. The crystal structure was isostructural with that of Ba 3 Re 2 O 9 , having a hexagonal unit cell of R3̅m symmetry with a = 0.574060(10) nm and c = 2.08256(4) nm. The high-pressure (HP) phase is obtained from a transformation of an ambient-pressure (AP) phase of the compound, which has the Cs 3 Tl 2 Cl 9 -type structure. The most notable change in the transformation is the connection of WO 6 octahedra. The HP phase has corner-sharing octahedra, which form a bilayer structure, while the AP phase has face-sharing octahedra of isolated [W 2 O 9 ] dimers. This type of the structural phase transition is unreported although it is possibly that a sequence of high-pressure structural transformations occurs for similar chemical compositions. The HP phase has W ions in WO 6 octahedra with an unusual off-center displacement; although the displacement is slightly relaxed compared with that of the AP phase. The off-center displacement suggests strong hybridization between the W 5d orbitals and O 2p orbitals.

The crystal structure of Al3O3.5C0.5 (Z = 3) has been characterized by X-ray powder diffraction (XRPD), transmission electron microscopy, and electron probe microanalysis. The title compound is trigonal with space group R3̅m (centrosymmetric) and hexagonal unit-cell dimensions a = 0.29588(1) nm, c = 2.84080(7) nm, and V = 0.21538(1) nm(3). The initial structural model was determined by the charge-flipping method and subsequently refined by the Rietveld method. The final structural model showed the positional disordering of one of the two types of Al sites. The maximum-entropy method-based pattern fitting (MPF) method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. The reliability indices calculated from the MPF were Rwp = 4.03%, S (= Rwp/Re) = 1.17, Rp = 3.08%, RB = 0.82%, and RF = 0.72%. The crystal was composed of antiphase domains, suggesting the occurrence of the high-low phase transition during the cooling process. The transition would be accompanied by the loss of unit-lattice translation, and hence the disordered structural model determined by XRPD might be of the average structure of the low-temperature phase.

The structural grounds of the decrease of point and lattice symmetries coupled with switching of the exchange interaction in single crystals of a highly strained, coordinationally unsaturated bisdiaminecopper(II) cation are described. The combined magnetic susceptibility and X-ray diffraction results indicate that the interplay between the inherent vibronic instability and ligand-field strain imposed by moderately flexible, coordinationally shielding ligands enables effective switching of the pseudo-Jahn-Teller d9 centers between states with different exchange interaction in the low-temperature regime and valence orbital orientation and coordination geometry in the high-temperature regime. Within the low-temperature hysteresis region, the phase transition can also be induced by excitation of the ligand-to-metal charge-transfer bands, resulting in overall shrinkage of the lattice. The compound is a prototype of weakly electronically coupled one-dimensional Jahn-Teller systems, which can undergo phase transitions induced by light, in addition to heating, cooling, and change of pressure, and it represents a prospective basis for the design of switching materials capable of multimode external control.

A novel series of acylides, 3-O-(aryl)acetylerythromycin A derivatives, were synthesized and evaluated. These compounds have significant potent antibacterial activity against not only Gram-positive pathogens, including inducibly macrolide-lincosamide-streptogramin B (MLS(B))-resistant and efflux-resistant strains, but also Gram-negative pathogens, such as H. influenzae. 6,9:11,12-dicarbonate acylide 47 (FMA0122) was twice as active against H. influenzae than azithromycin, whereas it showed only moderate in vivo efficacy in mouse protection tests. However, the 11,12-carbamate acylide 19 (TEA0929), which showed potent antibacterial activity against almost all of the main causative pathogens of community-acquired pneumonia tested, exhibited excellent in vivo efficacy comparable to those of second-generation macrolides.

Introduction of an acyl group to the 3-O-position of erythromycin A derivatives instead of L-cladinose led to a novel class of macrolide antibiotics that we named "acylides". The 3-O-nitrophenylacetyl derivative TEA0777 showed significantly potent activity against not only erythromycin-susceptible Gram-positive pathogens but also inducibly macrolides-lincosamides-streptogramin B (MLS(B))-resistant Staphylococcus aureus and efflux-resistant Streptococcus pneumoniae. These results indicated that acylides have potential as next-generation macrolide antibiotics.