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Four related sterically restricted peri-substitutedacenaphthenes have been prepared containing mixed tin–phosphorusmoieties in the proximal 5,6-positions (Acenap[SnR3][PiPr2]; Acenap = acenaphthene-5,6-diyl;R3= Ph3(1), Ph2Cl(2), Me2Cl (3), Bu2Cl (4)). The degree of intramolecular P–Sn bondingwithin the series was investigated by X-ray crystallography, solutionand solid-state NMR spectroscopy, and density functional theory (DFT/B3LYP/SBKJC/PCM)calculations. All members of the series adopt a conformation suchthat the phosphorus lone pair is located directly opposite the tincenter, promoting an intramolecular donor–acceptor P→Sntype interaction. The extent of covalent bonding between Sn and Pis found to be much greater in triorganotin chlorides 2–4in comparison with the triphenyl derivative 1. Coordination of a highly electronegative chlorine atomnaturally increases the Lewis acidity of the tin center, enhancingthe lp(P)−σ*(Sn–Y) donor–acceptor 3c-4etype interaction, as indicated by conspicuously short Sn–P peridistances and significant 1J(31P,119Sn) spin–spin coupling constants(SSCCs) in the range 740–754 Hz. Evidence supporting the presenceof this interaction was also found in solid-state NMR spectra of someof the compounds which exhibit an indirect spin–spin couplingon the same order of magnitude as observed in solution. DFT calculationsconfirm the increased covalent bonding between P and Sn in 2–4, with notable WBIs of ca. 0.35 obtained, incomparison to 0.1 in 1. [ABSTRACT FROM AUTHOR]

We here present the synthesis of a new material, Na 3 (VO)Fe(PO 4 ) 2 F 2 , by the sol-gel method. Its atomic and electronic structural descriptions are determined by a combination of several diffraction and spectroscopy techniques such as synchrotron X-ray powder diffraction and synchrotron X-ray absorption spectroscopy at V and Fe K edges, 57 Fe Mössbauer, and 31 P solid-state nuclear magnetic resonance spectroscopy. The crystal structure of this newly obtained phase is similar to that of Na 3 (VO) 2 (PO 4 ) 2 F, with a random distribution of Fe 3+ ions over vanadium sites. Even though Fe 3+ and V 4+ ions situate on the same crystallographic position, their local environment can be studied separately using 57 Fe Mössbauer and X-ray absorption spectroscopy at Fe and V K edges, respectively. The Fe 3+ ion resides in a symmetric octahedral environment, while the octahedral site of V 4+ is greatly distorted due to the presence of the vanadyl bond. No electrochemical activity of the Fe 4+ /Fe 3+ redox couple is detected, at least up to 5 V, whereas the reduction of Fe 3+ to Fe 2+ has been observed at ∼1.5 V versus Na + /Na through the insertion of 0.5 Na + into Na 3 (VO)Fe(PO 4 ) 2 F 2 . Comparing to Na 3 (VO) 2 (PO 4 ) 2 F, the electrochemical profile of Na 3 (VO)Fe(PO 4 ) 2 F 2 in the same cycling condition shows a smaller polarization which could be due to a slight improvement in Na + diffusion process thanks to the presence of Fe 3+ in the framework. Furthermore, the desodiation mechanism occurring upon charging is investigated by operando synchrotron X-ray diffraction and operando synchrotron X-ray absorption at V K edge.

Layered oxide compositions Li 3- x Na x Ni 2 SbO 6 have been prepared by solid-state synthesis. A complete solid solution is evidenced and characterized by X-ray and neutron diffraction as well as 7 Li and 23 Na solid-state nuclear magnetic resonance spectroscopy. The transition-metal layer is characterized by the classic honeycomb Ni 2+ /Sb 5+ ordering, whereas a more uncommon randomly mixed occupancy of lithium and sodium is evidenced within the alkali interslab space. In situ X-ray diffraction and density functional theory calculations show that this alkali disordered feature is entropically driven. Fast cooling then appears as a synthesis root to confine bidimensional alkali glass within crystalline layered oxides.

Solid-state NMR spectra of new P-Se heterocycles based on peri-substituted naphthalene motifs show the presence of unusual J couplings between Se and P. These couplings are between atoms in adjacent molecules and occur "through space", rather than through conventional covalent bonds. Experimental measurements are supported by relativistic DFT calculations, which confirm the presence of couplings between nonbonded atoms, and provide information on the pathway of the interaction. This observation improves the understanding of J couplings and offers insight into the factors that affect crystal packing in solids, for future synthetic exploitation.