The new compound Cu(2)P(1.8)As(1.2)I(2), with neutral, mixed pnicogen chains, has been synthesized from a stoichiometric combination of CuI, P, and As heated in vacuo at 550 degrees C. Cu(2)P(1.8)As(1.2)I(2) represents substitution of 40% of P in Cu(2)P(3)I(2) by As, with the As predominantly occupying "roof" positions in the tubular chains. The mixed pnicogen modification demonstrates increased stability (T(d) = 330 degrees C) relative to Cu(2)P(3)I(2) (T(d) = 290 degrees C) but a similar optical band gap (E(g) approximately 1.2 eV). Crystallographic data: Cu(2)P(1.8)As(1.2)I(2), monoclinic P2(1)/c, a = 15.477(3) A, b = 13.200(3) A, c = 15.421(3) A, beta = 115.406(4) degrees, Z = 16 (T = 293 K).

Removal of CuI from Cu(2)P(1.8)As(1.2)I(2) results in a novel P--As allotrope. Although the product is X-ray amorphous, lattice fringes are observed in the transmission electron micrographs with spacings reflecting the diameter of the linear pnicogen polymer in Cu(2)P(1.8)As(1.2)I(2), suggesting the pnicogen chains remain intact upon loss of CuI. The straight needles present in Cu(2)P(1.8)As(1.2)I(2) appear to be kinked in the P--As phase due to lattice mismatch between the liberated polymers, ultrasonic treatment, or a combination of these effects. This new P--As modification is semiconducting with a band gap of 1.05 eV.

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.

A variety of ion exchange techniques for Cu 2 P 3 I 2 and its mixed pnictogen analog Cu 2 P 1.8 As 1.2 I 2 have been studied. Ag 2 P 3 I 2 is an existing material, previously prepared from Cu 2 P 3 I 2 by ion exchange of Ag + for Cu + in aqueous medium. This method is compared to nonaqueous (ionic liquid) and solid state routes for ion exchange. Additionally, the new compound Ag 2 P 1.8 As 1.2 I 2 with cell parameters a = 15.838(17) Å, b = 13.684(10) Å, c = 15.580(17) Å and β = 117.63(7)°, has been prepared by reaction of Cu 2 P 1.8 As 1.2 I 2 with AgNO 3 in aqueous solution.

Structure Structure D 2000Toward an Arsenic Analogue of Hittorf's Phosphorus: Mixed Pnicogen Chains in Cu 2 P 1.8 As 1.2 I 2 .-The title compound is prepared by solid state reaction of a stoichiometric mixture of CuI, red phosphorus, and As (evacuated silica tube, 550°C, 14 d). Cu 2 P 1.8 As 1.2 I 2 crystallizes in the monoclinic space group P2 1 /c with Z = 16 and is fundamentally isostructural to Cu 2 P 3 I 2 ; however, the structure is more complex because of the shared occupancy of the pnicogen positions by P and As. The mixed pnicogen compound exhibits increased thermal stability relative to Cu 2 P 3 I 2 but a similar optical bandgap (E g ≅ 1.2 eV). -(JAYASEKERA, B.; AITKEN, J. A.; HEEG, M. J.; BROCK*, S. L.; Inorg. Chem. 42 (2003) 3, 658-660; Dep. Chem., Wayne State Univ., Detroit, MI 48202, USA; Eng.) -Schramke 18-006