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Comprehensive Summary: The family of [M(dmit)2]‐ salts (dmit2‐ = 2‐thioxo‐1,3‐dithiole‐4,5‐dithiolate; M = Ni, Pd and Pt) generally show novel magnetic, electric, magnetoelectric and photoelectric properties. Herein, a blockwall‐type layered [Me3S][Ni(dmit)2] radical salt (1; Me3S+ = trimethylsulfonium) was prepared and characterized by microanalysis, IR spectroscopy, thermal analysis, powder and single crystal X‐ray diffraction techniques. Salt 1 crystalizes in triclinic space group P‐1, with two pairs of [Ni(dmit)2]‐ and Me3S+ ions in an asymmetric unit. The anions form blockwall‐type monolayer, being parallel to crystallographic (0 1 1) plane, and the cations are accommodated in the spaces of anion monolayer. Salt 1 features a two‐dimensional S = ½ antiferromagnetic (AFM) spin system with θ = ‐97.8(1) K and a semiconductor with σ ≈ 10‐4 S·cm‐1 and activation energy Ea = 0.24(1) eV in 308—368 K. 1 shows two‐step dielectric relaxations ranged from 173—373 K and 1—107 Hz for the dipole motions of two different polar cations. Most importantly, the dielectric constant of 1 reaches to ~17, with high‐κ nature. This study suggests the possibility of achieving high‐κ materials by introducing polar and low rotation barrier components into van der Waals crystal and high‐κ [Ni(dmit)2]‐‐based electrode materials for applications in supercapacitors. [ABSTRACT FROM AUTHOR]

The zero/negative thermal expansion (ZTE/NTE), which is an intriguing physical property of solids, has been observed in a few families of materials. ZTE materials possess practical applications in specific circumstances such as space-related applications, engineering structures and precision instrument. Generally, NTE materials are used as additives to form a composite of the ZTE material with positive thermal expansion material. It is still a tremendous challenge to design new families of ZTE/NTE materials. Herein, we presented a temperature-dependent single crystal structure analysis in 110–300 K for a layered (NH4)2V3O8, which crystallizes in a tetragonal space group P4bm and comprises mixed valence [V3O82−]∞ monolayers and NH4+ residual in the interlayer spaces. Along the c-axis, (NH4)2V3O8 demonstrated uniaxial expansion behaviors, i.e., ZTE with αc = −1.10 × 10−6 K−1 in 110–170 K and NTE with αc = −16.25 × 10−6 K−1 in 170–220 K. Along the a-axis, (NH4)2V3O8 exhibited ZTE with αa = + 2.06 × 10−6 K−1 in 240–300 K. The mechanisms of ZTE and NTE were explored using structural analysis. The conduction of NH4+ ions in the interlayer space was studied, indicating that the conductivity rapidly rises with the expansion of interlayer space at temperatures of >293 K. This study discloses that layered vanadates are promising ZTE/NTE materials. [ABSTRACT FROM AUTHOR]

In this study, a multi-step phase transition hybrid composed of (Pr-dabco)2Ag4I6 clusters (Pr-dabco+ = 1-propyl-1,4-diazabicyclo[2.2.2]octan-1-ium) has been prepared and characterized by microanalysis, IR and UV-vis spectroscopy, TG and DSC techniques, etc. This hybrid is thermally stable up to ∼486 K with five phases in the temperature region below 486 K. The phase transition shows symmetry breaking (SB) character between phases II (space group P21/c) and III (space group Pa3¯), while inverse symmetry breaking (ISB) between phases II and I (space group Pbca), and it is rather exceptional for matter to exhibit simultaneously SB and ISB nature in two successive phase transitions. Most importantly, each phase transition is associated with a dielectric anomaly, and phase V appears to be a plastic crystal with extra high ac conductivity (>10−2 S cm−1). Our work opens up new avenues to find a multi-phase transition material in silver halide hybrids. [ABSTRACT FROM AUTHOR]

The zero/negative thermal expansion (ZTE/NTE), which is an intriguing physical property of solids, has been observed in a few families of materials. ZTE materials possess practical applications in specific circumstances such as space-related applications, engineering structures and precision instrument. Generally, NTE materials are used as additives to form a composite of the ZTE material with positive thermal expansion material. It is still a tremendous challenge to design new families of ZTE/NTE materials. Herein, we presented a temperature-dependent single crystal structure analysis in 110–300 K for a layered (NH4)2V3O8, which crystallizes in a tetragonal space group P4bm and comprises mixed valence [V3O82−]∞ monolayers and NH4+ residual in the interlayer spaces. Along the c-axis, (NH4)2V3O8 demonstrated uniaxial expansion behaviors, i.e., ZTE with αc = −1.10 × 10−6 K−1 in 110–170 K and NTE with αc = −16.25 × 10−6 K−1 in 170–220 K. Along the a-axis, (NH4)2V3O8 exhibited ZTE with αa = + 2.06 × 10−6 K−1 in 240–300 K. The mechanisms of ZTE and NTE were explored using structural analysis. The conduction of NH4+ ions in the interlayer space was studied, indicating that the conductivity rapidly rises with the expansion of interlayer space at temperatures of >293 K. This study discloses that layered vanadates are promising ZTE/NTE materials. [ABSTRACT FROM AUTHOR]

In this study, a multi-step phase transition hybrid composed of (Pr-dabco)2Ag4I6 clusters (Pr-dabco+ = 1-propyl-1,4-diazabicyclo[2.2.2]octan-1-ium) has been prepared and characterized by microanalysis, IR and UV-vis spectroscopy, TG and DSC techniques, etc. This hybrid is thermally stable up to ∼486 K with five phases in the temperature region below 486 K. The phase transition shows symmetry breaking (SB) character between phases II (space group P21/c) and III (space group Pa3[combining macron]), while inverse symmetry breaking (ISB) between phases II and I (space group Pbca), and it is rather exceptional for matter to exhibit simultaneously SB and ISB nature in two successive phase transitions. Most importantly, each phase transition is associated with a dielectric anomaly, and phase V appears to be a plastic crystal with extra high ac conductivity (>10-2 S cm-1). Our work opens up new avenues to find a multi-phase transition material in silver halide hybrids.