Structure–Property Correlations in Solid Solutions of (CuI)₈P_12−xAs_x, 2.4≤x≤6.6

Abstract

A series of P/As mixed pnicogen phases of composition (CuI)(8)P(12-x)As(x), in which x = 2.4, 4.2, 4.8, 5.4, and 6.6, have been synthesized and characterized by X-ray single crystal and powder diffraction, solid-state NMR spectroscopy, thermal gravimetric analysis, and impedance spectroscopy. These materials are isostructural to (CuI)(8)P(12) and consist of neutral, tubular P/As mixed pnicogen chains associated with Cu(I) and I(-) ions. The As is distributed throughout the pnicogen chains; however, the "roof" sites of the [P8] cage show preferred occupation by As relative to the other sites. Accordingly, the change in cell volume is not a linear function of the As incorporation. Solid-state (31)P NMR spectroscopy of the 40 % As incorporated sample are consistent with the X-ray structural model, with extensive broadening due to (31)P-(75)As coupling and site disorder, and a change in the chemical shifts of the resonances due to the As substitution into the lattice. The degree of copper ion site disorder, probed by single-crystal X-ray diffraction, increases with increasing As content. Although very little change is observed in the copper ionic conductivity of polycrystalline samples, which ranges from 1.8-5.1 x 10(-6) S cm(-1) for (CuI)(8)P(12-x)As(x), x = 0, 4.2, 5.4; a single crystal (x = 4.8) measured along the needle axis has a conductivity of 1.7 x 10(-3) S cm(-1) at 128 degrees C. This represents an order of magnitude improvement in conductivity over (CuI)(8)P(12) at the same temperature.

Icosahedral and Ring‐Shaped Allotropes of Arsenic

“…[11] The copper halide matrix techniques used to prepare red phosphorus chains have also been applied to obtain mixed PAs chains with arsenic contents of up to 55 %. [12,13] Isolating the mixed chains from the matrix results in semiconducting PAs polymers. [14] In the case of the violet phosphorus, 5 % of arsenic can be introduced into the crystal structure.…”

(HgBr2)3(As4S4)2: An Adduct of HgBr2 Molecules and Undistorted As4S4 Cages.

“…The crystal structure consists of molecular units built from two undistorted As 4 S 4 cages which are coordinated [7]. Even mixed arsenic-phosphorus polymers are accessible using this experimental approach [8]. A reason for the stability of these compounds is the structural flexibility of the copper halide framework, which is obviously able to host various molecules.…”

HgI2⋅As4S4: An Adduct from HgI2 Molecules and Undistorted As4S4 Cages

“…Mixed phosphorus-arsenic polymers can also be obtained in this way. [8] The catalytic influence of Cu + ions and the structural flexibility of the copper halide are the major reasons for the success of this approach. A possible stabilizing influence of the matrix on the embedded molecules must also be taken into account.…”

“…[9] The isostructural arsenic-bearing polymers can be obtained in the same way. [8] After the successful synthesis of a number of otherwise unknown or inaccessible phosphorus chalcogenides in a matrix of copper halides, [6] the next challenging task was the synthesis of binary cages As 4 Q 4 (Q = S, Se) that are coordinated as neutral ligands to a transition metal. To date, these molecules, which are also known as minerals, could not be built into complex structures without fragmentation.…”