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Two-Dimensional CsAg 5 Te 3– x S x Semiconductors: Multi-anion Chalcogenides with Dynamic Disorder and Ultralow Thermal Conductivity
Metal chalcogenides underpin a wide variety of energyrelated applications and are ideal systems for probing lattice dynamics and fundamental transport phenomena. Here we describe the synthesis and transport properties of CsAg 5 TeS 2 and its solid solution CsAg 5 Te 3-x S x (x = 1-2), new semiconductors with tunable band gaps ranging from 0.17 to 0.30 eV. CsAg 5 TeS 2 has a fully ordered two-dimensional structure that includes a group of Ag atoms in a heteroleptic tetrahedral coordination geometry (AgTe 2 S 2 ). Single-crystal X-ray diffraction indicates that the compounds crystallize in the tetragonal space group P 4/ mmm , while pair distribution function (PDF) analysis reveals off-centering at the heteroleptic Ag sites, signifying the lower-symmetry I4/ mcm space group. The underlying disorder as a phonon-blocking mechanism that helps facilitate an ultralow lattice thermal conductivity below 0.40 Wm -1 • K -1 at , ~ 300 K , highlighting the importance of local disorder in thermal transport. In conclusion, density functional theory provides additional insight into the electronic and thermal properties of the materials, which are good candidates for p-type thermoelectrics.
Decoding the Effect of Anion Identity on the Solubility of N -(2-(2-Methoxyethoxy)ethyl)phenothiazine (MEEPT)
Variations in the solubility of redox-active organic molecules (ROM) of interest for nonaqueous redox flow batteries (RFB), especially as the ROM state-of-charge changes during charge-discharge cycling, present significant molecular design challenges. The situation is further complicated as ROM solubility can be regulated by the choice of electrolyte salt and solvent that together with the ROM comprise the catholyte or anolyte (redox electrolyte) formulation, presenting materials design challenges. The ROM N-(2-(2-methoxyethoxy)ethyl)phenothiazine (MEEPT) is a viscous liquid at room temperature and is miscible in several organic solvents, including acetonitrile and propylene carbonate. The MEEPT radical cation (MEEPT +· ) paired with tetrafluoroborate (BF 4 - ) in acetonitrile presents a 0.5 M solubility, a dramatic decrease when compared to the viscous liquid of neutral MEEPT. Here, in this study, we present a joint experimental, regression modeling, and molecular dynamics (MD) simulations investigation to explore MEEPT-X (where X represents the counteranion) salt solubility variability as a function of concentration and counteranion chemistry in acetonitrile. We find a strong dependence of the salt solubility on the counteranion and relate these findings to explicit intermolecular interactions between MEEPT +· and the counteranion in the electrolyte solution.
Iron(II) Complexes of an Anionic Bis(ylide)diphenylborate Ligand
Double deprotonation of the salt [Ph 2 B(PMe 3 ) 2 ][OTf] provides access to a bis(ylide)diphenylborate ligand that is readily transferred in situ to iron(II). Depending on the reaction stoichiometry, both the “ate” complex [Ph 2 B(Me 2 PCH 2 ) 2 Fe(μ-Cl) 2 Li(THF) 2 ] and the homoleptic complex [Ph 2 B(Me 2 PCH 2 ) 2 ] 2 Fe can be prepared from FeCl 2 (THF) 1.5 . Further reaction of with FeCl 2 (THF) 1.5 produces the chloride-bridged dimer [Ph 2 B(Me 2 PCH 2 ) 2 Fe(μ-Cl) 2 Fe(CH 2 PMe 2 ) 2 BPh 2 ]. Attempts to reduce or alkylate provide as the only isolable product, likely a consequence of the low steric hindrance of the bis(ylide)diphenylborate ligand. On the other hand, reaction of with the strong field ligand CN t Bu provides the six-coordinate, diamagnetic complex [Ph 2 B(Me 2 PCH 2 ) 2 Fe(CN t Bu) 4 ][Cl]. Here, the electronic structure calculations for the bis(ylide)diphenylborate ligand and homoleptic complex suggest that the C(ylide) atoms are strong σ-donors with little π-bonding character. These initial results suggest the potential for this bis(ylide)diphenylborate ligand in coordination chemistry.
Rapid Cs[supercript +] Capture via Multiple Supramolecular Interactions in Anionic Metal?Organic Fra
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