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Here, we quantify the relationship between microphase segregation and local structure development in thermoplastic polyurethanes. Samples were prepared with varying ratios of 4,4′‐methylene diphenyl diisocyanate (MDI) and 1,4‐butanediol (BDO) to polytetrahydrofuran (PTHF) and annealed at temperatures Tabetween RT–140 °C for 20 h each. Distinct populations of smaller and larger ordered domains are distinguished by pair distribution function analysis. The intermediate‐range order of nanoscale hard domains in the paracrystalline state (form I) is directly extracted and characterized. The results suggest that form I of the MDI‐BDO:PTHF system presents a conformational and packing order similar to the form III structure, typically obtained from stretching/annealing, but with limited spatial coherence of 3–7 nm. Heating above Tgof the hard segments is necessary to achieve a substantial structural response from the annealing treatment. Increasing Tapromotes purification of the soft phase via microphase segregation, coalescence of the hard blocks, and growth of paracrystalline phase, while a minority fraction of longer‐range ordered domains left over from production remains relatively constant. We observe a composition‐dependent decrease in the average nearest‐neighbor distance that can be correlated with the greater number of CC, CN, and CO bonds with increased hard segment content. A non‐linear deviation in the trend is observed to correlate with sample densification. The mechanical and thermal behavior of the samples is intimately tied to the segregation state.

Cesium dicyanamide Cs[C2N3] (≡ Cs[N(CN)2] or Cs[dca]) was obtained by a metathesis reaction in form of transparent colorless platelets. The results of single-crystal X-ray structure measurements and refinements (C2/c, Z= 8) with the monoclinic cell parameters a= 932.31(8), b= 1274.67(9), c= 824.94(7) pm, β= 110.803(3)° at −70 °C and a= 939.59(7), b= 1281.58(8), c= 827.57(6) pm, β= 110.610(3)° at 20 °C corroborate earlier results for this compound. The Raman and IR spectra of Cs[C2N3] are presented for the first time and the result compares well with those of NaCs2[C2N3]3. The heat-driven cyclotrimerization process of Cs[C2N3] was studied by thermal analyses (DSC) and temperature-dependent X-ray powder diffraction methods. At 370 °C, its trimerization product Cs3[C6N9] is formed, crystallizing in the orthorhombic space group Pbamwith the cell parameters a= 3043.0(3), b= 1052.4(1) and c= 415.21(4) pm for Z= 4. The IR spectrum of this cesium tricyanomelaminate (Cs3[C6N9] or Cs3[TCM]) is presented, but a well-resolved Raman spectrum could not be acquired owing to fluorescence phenomena. An overview about the cyclotrimerization reactions of all pseudo-binary alkali-metal dicyanamides (A[C2N3]) to their corresponding tricyanomelaminates (A3[C6N9]) with A= Li–Cs gives a basis for a discussion of the different thermal and structural characteristics.

The structure of the first lithium-containing bismuth ortho (o)-thiophosphate was determined using a combination of powder X-ray, neutron, and electron diffraction. Li60–3xBi16+x(PS4)36with xin the range of 4.1–6.5 possesses a complex monoclinic structure [space group C2/c(No. 15)] and a large unit cell with the lattice parameters a= 15.4866 Å, b= 10.3232 Å, c= 33.8046 Å, and β = 85.395° for Li44.4Bi21.2(PS4)36, in agreement with the structure as observed by X-ray and neutron pair distribution function analysis. The disordered distribution of lithium ions within the interstices of the dense host structure and the Li ion dynamics and diffusion pathways have been investigated by solid-state nuclear magnetic resonance (NMR) spectroscopy, pulsed field gradient NMR diffusion measurements, and bond valence sum calculations. The total lithium ion conductivities range from 2.6 × 10–7to 2.8 × 10–6S cm–1at 20 °C with activation energies between 0.29 and 0.32 eV, depending on the bismuth content. Despite the highly disordered nature of lithium ions in Li60–3xBi16+x(PS4)36, the underlying dense host framework appears to limit the dimensionality of the lithium diffusion pathways and emphasizes once more the necessity of a close inspection of the structure–property relationships in solid electrolytes.

The outstanding diversity of Zr-based frameworks is inherently linked to the variable coordination geometry of Zr-oxo clusters and the conformational flexibility of the linker, both of which allow for different framework topologies based on the same linker–cluster combination. In addition, intrinsic structural disorder provides a largely unexplored handle to further expand the accessibility of novel metal–organic framework (MOF) structures that can be formed. In this work, we report the concomitant synthesis of three topologically different MOFs based on the same M6O4(OH)4clusters (M = Zr or Hf) and methane-tetrakis(p-biphenyl-carboxylate) (MTBC) linkers. Two novel structural models are presented based on single-crystal diffraction analysis, namely, cubic c-(4,12)MTBC-M6and trigonal tr-(4,12)MTBC-M6, which comprise 12-coordinated clusters and 4-coordinated tetrahedral linkers. Notably, the cubic phase features a new architecture based on orientational cluster disorder, which is essential for its formation and has been analyzed by a combination of average structure refinements and diffuse scattering analysis from both powder and single-crystal X-ray diffraction data. The trigonal phase also features structure disorder, although involving both linkers and secondary building units. In both phases, remarkable geometrical distortion of the MTBC linkers illustrates how linker flexibility is also essential for their formation and expands the range of achievable topologies in Zr-based MOFs and its analogues.

Thin films comprised of 2D materials have attracted significant attention, as they can be assembled into novel functional materials. However, to further enhance their application scope, it is necessary to harvest the large property space of 2D materials by fine-tuning them on a molecular level, e.g., by intercalation. In order to fully exploit the potential of intercalated 2D materials and design their properties, it is vital to gain a fundamental understanding of the underlying intercalation mechanism. In this work, we present a method for the quantitative analysis of changes in the peak profile and position observed by in situsynchrotron measurements upon the intercalation of the guest molecule into the layered host. We do this by monitoring the intercalation of n-butylamine (3 M in ethanol) into a H3Sb3P2O14thin film in real time. Our approach includes a state-of-the-art recursive supercell approach that accounts for peak broadening and shifting caused by randomly occurring intercalation, which enabled quantitative Rietveld refinements of the XRD patterns obtained during the interstratification process. This allowed us to reveal the transient formation of intermediates and the critical role of ethanol, which acts as a vehicle for amine intercalation into the layered host.

Covalent organic frameworks (COFs) with a pore size beyond 5 nm are still rarely seen in this emerging field. Besides obvious complications such as the elaborated synthesis of large linkers with sufficient solubility, more subtle challenges regarding large-pore COF synthesis, including pore occlusion and collapse, prevail. Here we present two isoreticular series of large-pore imine COFs with pore sizes up to 5.8 nm and correlate the interlayer interactions with the structure and thermal behavior of the COFs. By adjusting interlayer interactions through the incorporation of methoxy groups acting as pore-directing “anchors”, different stacking modes can be accessed, resulting in modified stacking polytypes and, hence, effective pore sizes. A strong correlation between stacking energy toward highly ordered, nearly eclipsed structures, higher structural integrity during thermal stress, and a novel, thermally induced phase transition of stacking modes in COFs was found, which sheds light on viable design strategies for increased structural control and stability in large-pore COFs.

Metal complexes exhibiting multifunctional properties are very rare. Here, we report a Zn(II) complex, [Zn(benzoate)(25F-spy)2], where 25F-spy = 2′,5′-difluoro-4-styrylpyridine, displays unpredicted photosalient behavior while it undergoes a [2 + 2] cycloaddition reaction and exhibits unusual thermal expansion with occasional jumping, second-harmonic generation (SHG), and two-photon photoluminescence (2PPL). In the solid state, the 25F-spy ligands are packed in a head-to-tail manner. The distance between the pairs of olefin bonds, 4.279(2) Å, is not suitable for undergoing a [2 + 2] photocycloaddition reaction. However, these crystals not only undergo photodimerization quantitatively but also exhibit a photosalient effect under UV light. An interesting anisotropic thermal expansion facilitates the crystals to jump occasionally when they are heated to 140 °C, similarly to the thermosalient effect. Thermal expansion values along X1, X2, and X3are −54.46, 106.42, and 151.69 × 10–6K–1, respectively, with V= 204.26 × 10–6K–1(30–140 °C). Furthermore, these crystals exhibit light-frequency upconversion via both SHG and 2PPL. Altogether, a single crystal shows all of these diverse solid-state properties.

Covalent organic frameworks have emerged as a powerful synthetic platform for installing and interconverting dedicated molecular functions on a crystalline polymeric backbone with atomic precision. Here, we present a novel strategy to directly access amine-linked covalent organic frameworks, which serve as a scaffold enabling pore-wall modification and linkage-interconversion by new synthetic methods based on Leuckart–Wallach reduction with formic acid and ammonium formate. Frameworks connected entirely by secondary amine linkages, mixed amine/imine bonds, and partially formylated amine linkages are obtained in a single step from imine-linked frameworks or directly from corresponding linkers in a one-pot crystallization-reduction approach. The new, 2D amine-linked covalent organic frameworks, rPI-3-COF, rTTI-COF, and rPy1P-COF, are obtained with high crystallinity and large surface areas. Secondary amines, installed as reactive sites on the pore wall, enable further postsynthetic functionalization to access tailored covalent organic frameworks, with increased hydrolytic stability, as potential heterogeneous catalysts.

Thermally responsive crystals hold great potential for their use as actuating materials by acting as energy transducers to convert heat energy to mechanical work. Control over defined phase transition temperature with rapid reconfiguration is of great advantage for actuation. The thermosalient (TS) effect is a rarely observed phenomenon in coordination polymers (CPs), let alone the reversibility of thermosalience in CPs. Herein, we report the reversible TS effect in a one-dimensional CP due to the martensitic phase transition during both heating and cooling cycles. The TS effect was preceded by anisotropic thermal expansion showing high expansion coefficients. In addition, the nonmolecular crystals show reversible contraction and recovery during multiple heating–cooling cycles due to the self-restorative shape memory effect. The reversible actuation of the CP could be repeated for 20 heating–cooling cycles in differential scanning calorimetry experiments, suggesting its great potential as a multicyclic actuator. Such thermal responsive behavior is unique in metal–organic materials.

Structural and morphological interplay between hard and soft phases determine the bulk properties of thermoplastic polyurethanes. Commonly employed techniques rely on different physical or chemical phenomena for characterizing the organization of domains, but detailed structural information can be difficult to derive. Here, total scattering pair distribution function (PDF) analysis is used to determine atomic-scale insights into the connectivity and molecular ordering and compared to the domain size and morphological characteristics measured by AFM, TEM, SAXS, WAXS, and solid-state NMR 1H–1H spin-diffusion. In particular, density distribution functions are highlighted as a means to bridging the gap from the domain morphology to intradomain structural ordering. High real-space resolution PDFs are shown to provide a sensitive fingerprint for indexing aromatic, aliphatic, and polymerization-induced bonding characteristics, as well as the hard phase structure, and indicate that hard phases coexist in both ordered and disordered states.

Dehydration of calcium acetate monohydrate (Ca(CH3COO)2·H2O) by heating to 300 °C leads to the formation of anhydrous α-Ca(CH3COO)2. During heating and cooling cycles, high- and low-temperature forms of α-Ca(CH3COO)2were discovered. The reversible first-order phase transformation between the two forms occurs in a temperature range between 150 and 170 °C. The crystal structures were solved from laboratory powder X-ray diffraction (PXRD) data. The low temperature form of α-calcium acetate (LT-α-Ca(CH3COO)2) crystallizes at room temperature in a primitive triclinic unit cell with space group P1with lattice parameters of a= 8.7168(3) Å, b= 12.6408(3) Å, c= 12.3084(3) Å, α = 117.4363(17)°, β = 77.827(2)°, γ = 115.053(2)°, and a unit cell volume of 1090.23(6) Å3. High-temperature α-calcium acetate (HT-α-Ca(CH3COO)2) crystallizes at 300 °C in a rhombohedral unit cell with space group R3, lattice parameters of a= 21.1030(5) Å, c= 8.7965(2) Å, and a unit cell volume of 3392.58(17) Å3. In both crystal structures, edge sharing polyhedra of calcium cations and acetate anions that coordinate in both a mono- and bidentate way build up channel-like motifs. During the phase transition, the coordination mode of a bridging acetate anion changes from monodentate to bidentate, and the elliptical channels of the low temperature form become circular. This leads to both negative and positive thermal expansion along different principal axes in the crystal structure of LT-α-Ca(CH3COO)2and to an overall considerably big volumetric thermal expansion.

Investigations of the atomic structures within polyamides started over 80 years ago and continue today. These weakly ordered materials diffract X‐rays poorly and typically require postprocessing to obtain idealized samples for structural studies. An important goal remains to develop techniques to study the local structure in its natural state, with atomic resolution, and with sensitivity to subtle changes due to synthesis conditions or other technologically relevant processing procedures. Here, we compare the structures of as‐produced, nonoriented polyamide 6 ([C6H11NO]n) from both hydrolytic and anionic processes. A total scattering pair distribution function approach is used to elucidate information about the atomic bonding, molecular conformation, chain packing, crystallite size, and ratio of ordered to disordered domain content. The results are compared with those from standard analytical methods. Pair distribution function analysis of synchrotron x‐ray scattering measurements was used to assess the local atomic structure in industrially produced samples of semicrystalline polyamide 6. Real‐space structure refinements allow the quantification of interatomic distances and lattice parameters even for poorly diffracting and partially amorphous polymer samples. Details of the local structure, long‐range ordered domains, and phase quantification are benchmarked against imaging, spectroscopic, and thermal methods.

The reaction of Mn(NCS)2with 4-cyanopyridine (CNpy) leads to the formation of discrete complexes with the composition [Mn(NCS)2(CNpy)4] (1), [Mn(NCS)2(H2O)2(CNpy)2] (2-Iand 2-II), and [Mn(NCS)2(H2O)2(CNpy)2]·xCNpy (x= 4, 3; x= 2, 4), in which the Mn(II) centers are octahedrally coordinated by two terminal N-bonded thiocyanate anions and by four (1) or two CNpy coligands and two water molecules (2-I, 2-II, 3, and 4). If an excess of Mn(NCS)2is used, two additional compounds with the compositions [Mn(NCS)2(CNpy)2]n(5) and [Mn(NCS)2(CNpy)]n(6-Iand 6-II) are obtained. In all compounds the Mn(II) cations are octahedrally coordinated and linked into linear chains (5), into layers (6-I), or into a 3D network (6-II) by the thiocyanate anions. Investigations using TG-DTA and temperature-dependent powder X-ray diffraction prove that the discrete complexes 2-II, 3, and 4decompose in several steps, leading to the formation of Mn(NCS)2via 5and 6-Ias intermediates. For compounds 2-II, 4, and 6-IIonly one batch was obtained, indicating that these compounds are metastable. Magnetic measurements for compounds 5and 6-Ireveal dominating antiferromagnetic interactions and maxima in the susceptibility curve at 20 K (5) and 24 K (6-I), which are reproduced by quantum Monte Carlo simulations. The specific heat proves magnetic ordering at 2.8 K (5) and 12.4 K (6-I). The ordering of 6-Iis associated with a weak ferromagnetism.

While in situsynchrotron X-ray powder diffraction has revolutionized mechanistic studies of mechanochemistry and inspired the development of other real-time monitoring approaches, the full potential of such data remains unexploited, with most applications addressing only reaction kinetics. Focusing on UiO-type metal–organic frameworks (MOFs) as models, we now show how in-depth analysis of real-time diffraction data can provide insight into the evolution of both crystallographic structure and crystallite size, including the direct relation to the particle size of mechanochemically formed MOFs.

Ethylenebis(dithiocarbamates) (EBDTCs) have been extensively used as fungicides in agriculture for nearly 80 years. Modern fungicides based on EBDTCs contain metal ions, such as zinc in Zineb and Metiram, manganese in Maneb, or combinations of both, such as in Mancozeb. Despite being commercially available since the 1940s, the molecular structure of the metal complexes of EBDTCs was not described in detail until the crystal structure of Zineb was published in 2020. Zineb (C4H6N2S4Zn) is a single-phase crystalline material. In this study, we present a comprehensive multimethod structural characterization of Metiram (C12H27N9S12Zn3), which is the active ingredient of Polyram WG, a highly effective and plant-compatible organic contact fungicide. Our findings reveal that Metiram comprises two distinct phases. The primary phase, phase I, of Metiram is ethylenebis(dithiocarbamate) zinc(II) ammine, which constitutes 81 wt % of the material, or three-quarters of EBDTC. It is a zinc-coordinating crystalline phase. The crystal structure of this phase was determined by powder X-ray diffraction, revealing 1D S-shaped chains of EBDTC connected by strongly distorted Zn[NH3][S4] tetragonal pyramids. These pyramids share their sulfur atoms, and ammonia molecules occupy the apex of the pyramids, pointing alternately up and down. The secondary phase, phase II, constitutes 19 wt % of the material or one-quarter of EBDTC, and is amorphous. Using a combination of different techniques, including microscopy, diffraction, and spectroscopy, we have concluded that phase II consists of Zn-free EBDTC. We infer that the primary structure of this secondary constituent aligns with previous assumptions, notably the absence of a significant amount of Zn and the presence of disulfide bonds.

Multinary earth-abundant chalcogenides, like kesterite, Cu2ZnSnS4(CZTS), have attracted attention in sustainable energy applications like photovoltaics and thermoelectrics. High-energy ball milling provides a facile way for the synthesis of pure cubic CZTS. This sulfide crystallizes in a sphalerite-type structure with complete occupational disorder in the cationic substructure and a considerable amount of stacking faults. Heating of the material leads to the slow and irreversible transition into disordered, tetragonal kesterite, which is associated with a significant decrease in thermoelectric properties. Hence, a deep understanding of the phase transition process and its kinetics is a prerequisite for further crystal engineering. In situX-ray powder diffraction and Raman spectroscopy supported by density functional theory calculations and ab initiomolecular dynamics simulations (AIMD) were employed to gain microstructural insights into the phase transition process. Heating leads to a growth of the crystalline domains, which is associated with a reduction of strain. The domain growth reduces the stabilization of the metastable cubic phase by nanostructuring. This eventually leads to the segregation of tin cations, which corresponds to the beginning of the transition into the tetragonal phase. AIMD simulations indicate that the presence of faulting planes promotes the tin diffusion. As stacking faults appear to be energetically less favorable in the tetragonal disordered form, the stacking fault disorder is reduced upon heating, leading to an additional strain reduction.

Tetratopic porphyrin-based metal–organic frameworks (MOFs) represent a particularly interesting subclass of zirconium MOFs due to the occurrence of several divergent topologies. Control over the target topology is a demanding task, and reports often show products containing phase contamination. We demonstrate how mechanochemistry can be exploited for controlling the polymorphism in 12-coordinated porphyrinic zirconium MOFs, obtaining pure hexagonal PCN-223 and cubic MOF-525 phases in 20–60 min of milling. The reactions are mainly governed by the milling additives and the zirconium precursor. In situmonitoring by synchrotron powder X-ray diffraction revealed that specific reaction conditions resulted in the formation of MOF-525 as an intermediate, which rapidly converted to PCN-223 upon milling. Electron spin resonance measurements revealed significant differences between the spectra of paramagnetic centers in two polymorphs, showing a potential of polymorphic Zr-MOFs as tunable supports in spintronics applications.

Solving the structure of carbon nitrides has been a long-standing challenge due to the low crystallinity and complex structures observed within this class of earth-abundant photocatalysts. Herein, we report on two-dimensional layered potassium poly(heptazine imide) (K-PHI) and its proton-exchanged counterpart (H-PHI), obtained by ionothermal synthesis using a molecular precursor route. We present a comprehensive analysis of the in-plane and three-dimensional structure of PHI. Transmission electron microscopy and solid-state NMR spectroscopy, supported by quantum-chemical calculations, suggest a planar, imide-bridged heptazine backbone with trigonal symmetry in both K-PHI and H-PHI, whereas pair distribution function analyses and X-ray powder diffraction using recursive-like simulations of planar defects point to a structure-directing function of the pore content. While the out-of-plane structure of K-PHI exhibits a unidirectional layer offset, mediated by hydrated potassium ions, H-PHI is characterized by a high degree of stacking faults due to the weaker structure directing influence of pore water. Structure–property relationships in PHI reveal that a loss of in-plane coherence, materializing in smaller lateral platelet dimensions and increased terminal cyanamide groups, correlates with improved photocatalytic performance. Size-optimized H-PHI is highly active toward photocatalytic hydrogen evolution, with a rate of 3363 μmol/gh H2placing it on par with the most active carbon nitrides. K- and H-PHI adopt a uniquely long-lived photoreduced polaronic state in which light-induced electrons are stored for more than 6 h in the dark and released upon addition of a Pt cocatalyst. This work highlights the importance of structure–property relationships in carbon nitrides for the rational design of highly active hydrogen evolution photocatalysts.

Mechanochemistry enables targeted, rapid synthesis of bimetallic metal–organic frameworks (MOFs) with a controlled 1:1 stoichiometric composition of metal nodes. In particular, ball milling enabled the use of specifically synthesized solid coordination complexes of Zn(II), Mg(II), Ni(II), and Co(II) for the assembly of a range of microporous mixed-metal MOF-74 materials composed of pairs of d-block or main group metals in a predetermined 1:1 stoichiometric ratio, including ZnMg-, ZnCo-, ZnCu-, MgZn-, MgCo-, NiZn-, NiMg-, NiCo-, CoZn-, CoMg-, CoCu-, and MgCa-MOF-74. By using specifically prepared precursors in the synthesis of diverse mixed-metal MOF-74 targets, this rational synthesis represents the first entry of mechanochemistry into the target-oriented synthesis of mixed-metal MOFs.

A previously unknown solid phase in the zinc-imidazole system relevant for the synthesis of ZIF-8 was obtained by adding a small excess of methylimidazole (Hmim) to a diluted zinc chloride solution. By chemical and thermal analyses, a composition of Zn3(mim)5ClH2O·xH2O with x= 0.74 was determined and the compound denoted as ZIF-yqt hydrate. The crystal structure was solved from laboratory X-ray powder diffraction (XRPD) data. ZIF-yqt hydratecrystallizes in a C-centered monoclinic unit cell with space group C2/c(15) and lattice parameters of a= 13.1574(3) Å, b= 16.4959(3) Å, c= 13.6403(3) Å, and β = 119.166(2)°. The structure is built up from Zn(mim)4/2and Zn(mim)3/2(Cl0.5H2O0.5)1/1units forming a self-penetrating yqt1 type net. IR spectroscopy was employed to confirm the presence of water in the coordination sphere of zinc. In addition, noncoordinated water is situated in the voids of this net. By heating, ZIF-yqt hydratecan be completely dehydrated resulting in the formation of anhydrous Zn3(mim)5Cl that is denoted as ZIF-yqt anhydrous. The crystal structure of the latter phase was solved from XRPD data as well. A self-penetrating yqt1 type net almost identical to the structure of the hydrated phase is formed by Zn(mim)4/2and Zn(mim)3/2Cl1/2units. By temperature and moisture dependent powder XRD measurement, it was demonstrated that the dehydration of ZIF-yqt hydrateand the transformation into ZIF-yqt anhydrousis completely reversible.

Reaction of Zn(NCS)2with 4-dimethylaminopyridine (DMAP) leads to the formation of three polymorphic modifications of Zn(NCS)2(DMAP)2(I–Zn, II–Zn, and III–Zn), of which only the crystal structure of I–Znis reported in literature. In all three modifications the Zn(II) cations are tetrahedrally coordinated by two terminal N-bonded thiocyanate anions and two DMAP ligands forming discrete complexes, which differ in the dihedral angle between the DMAP ring planes and the arrangement of the complexes in the crystals. All three modifications show melting, and the thermodynamic relations and the transition behavior were investigated by temperature-dependent X-ray powder diffraction, differential scanning calorimetry, thermomicroscopy, and solvent-mediated conversion experiments. These reveal that I–Znand II–Znas well as II–Znand III–Znare related by enantiotropism, whereas I–Znand III–Znare related by monotropism. The thermodynamic transition temperature between I–Znand II–Znis much lower than that between the isotypic Co(II) modifications I–Coand II–Coreported recently.

Iridium(IV) oxides have gained increased attention in recent years owing to the presence of competing spin–orbit coupling and Coulomb interactions, which facilitate the emergence of novel quantum phenomena. In contrast, the electronic structure and magnetic properties of IrIV-based molecular materials remain largely unexplored. In this paper, we take a fresh look at an old but puzzling compound, Na2IrCl6, which can be hydrated to form two stable phases with formulas Na2IrCl6·2H2O and Na2IrCl6·6H2O. Their crystal structures are well illustrated based on X-ray powder diffraction data. Magnetic studies reveal that Na2IrCl6and Na2IrCl6·2H2O are canted antiferromagnets with ordering temperatures of 7.4 and 2.7 K, respectively, whereas Na2IrCl6·6H2O is paramagnetic down to 1.8 K. First-principle calculations on Na2IrCl6reveal a Jeff= 1/2 ground state, and the band structures show that Na2IrCl6is a spin–orbital-induced semiconductor with an indirect gap of about 0.18 eV.

Reaction of Ni(NCS)2with 4-aminopyridine in different solvents leads to the formation of compounds with the compositions Ni(NCS)2(4-aminopyridine)4(1), Ni(NCS)2(4-aminopyridine)2(H2O)2(2), [Ni(NCS)2(4-aminopyridine)3(MeCN)]·MeCN (3), and [Ni(NCS)2(4-aminopyridine)2]n(5-LT). Compounds 1, 2, and 3form discrete complexes, with octahedral metal coordination. In 5-LTthe Ni cations are linked by single thiocyanate anions into chains, which are further connected into layers by half of the 4-aminopyridine coligands. Upon heating, 1transforms into an isomer of 5-LTwith a 1D structure (5-HT), that on further heating forms a more condensed chain compound [Ni(NCS)2(4-aminopyridine)]n(6) that shows a very unusual chain topology. If 3is heated, a further compound with the composition Ni(NCS)2(4-aminopyridine)3(4) is formed, which presumably is a dimer and which on further heating transforms into 6via 5-HTas intermediate. Further investigations reveal that 5-LTand 5-HTare related by enantiotropism, with 5-LTbeing the thermodynamic stable form at room-temperature. Magnetic and specific heat measurements reveal ferromagnetic exchange through thiocyanate bridges and magnetic ordering due to antiferromagnetic interchain interactions at 5.30(5) K and 8.2(2) K for 5-LTand 6, respectively. Consecutive metamagnetic transitions in the spin ladder compound 6are due to dipolar interchain interactions. A convenient formula for susceptibility of the ferromagnetic Heisenberg chain of isotropic spins S= 1 is proposed, based on numerical DMRG calculations, and used to determine exchange constants.

Two different Li/S cathodes are compared in terms of capacity (mA.h.gsulfur[?]1) and intermediates during discharge and charge. One cathode material is based on fibrous SPAN, a sulfur-containing material obtained via the thermal conversion of poly(acrylonitrile), PAN, in the presence of sulfur. In this material, sulfur is covalently bound to the polymeric backbone. The second cathode material is based on porous activated carbon fibers (ACFs) with elemental sulfur embedded inside the ACFs' micropores. Cyclic voltammetry clearly indicates different discharge and charge chemistry of the two materials. While S-containing ACFs show the expected redox-chemistry of sulfur, SPAN does not form long-chain polysulfides during discharge; instead, sulfide is chopped off the polymer-bound sulfur chains to directly form Li2S. The high reversibility of this process accounts for both the high cycle stability and capacity of SPAN-based cathode materials.