The Solid Solutions (Per)2[PtxAu(1−x)(mnt)2]; Alloying Para- and Diamagnetic Anions in Two-Chain Compounds

Abstract

Abstract:The α-(Per) 2 [M(mnt) 2 ] compounds with M = Pt and Au are isostructural two-chain solids that in addition to partially oxidized conducting perylene chains also contain anionic chains that can be either paramagnetic in the case of M = Pt or diamagnetic for M = Au. The electrical transport and magnetic properties of the solid solutions (Per) 2 [Pt x -Au (1−x) (mnt) 2 ] were investigated. The incorporation of paramagnetic [Pt(mnt) 2 ] impurities in the diamagnetic chains, and the effect of breaking the paramagnetic chains with diamagnetic centers for the low and high Pt range of concentrations were respectively probed. In the low Pt concentration range, there is a fast decrease of the metal-to-insulator transition from 12.4 K in the pure Au compound to 9.7 K for x = 0.1 comparable to the 8.1 K in the pure Pt compound. In the range x = 0.50−0.95, only β-phase crystals could be obtained. The spin-Peierls transition of the pure Pt compound, simultaneous with metal-to-insulator (Peierls) transition is still present for 2% of diamagnetic impurities (x = 0.98) with transition temperature barely affected. Single crystal X-ray diffraction data obtained a high-quality structural refinement of the α-phase of the Au and Pt compounds. The β-phase structure was found to be composed of ordered layers with segregated donors and anion stacks, which alternate with disordered layers. The semiconducting properties of the β-phase are due to the disorder localization effects.

Structural, magnetic and phase transition properties in S = ½ radical solid solutions of [FxCl1−x-BzPy][Ni(mnt)2] (x = 0.07–0.87)

“…The solid solutions ( x = 0.07–0.54) show higher T C than the two parent salts, and this finding is in contrast to general observations in the phase transition solid solutions, e.g. , [Mn x Zn 1− x (HCOO) 3 ], 6 ( o -DMTTF) 2 (Br) x (Cl) 1− x , 7 (Per) 2 [Pt x Au 1− x (mnt) 2 ], 15 [Cl-BzPy][Ni x Pt 1− x (mnt) 2 ] ( x = 0–1), 34 [NH 3 NH 2 ] 1− x -[NH 3 OH] x Zn(HCOO) 3 , 3 CMBr x I 1− x and CMBr x Cl 1− x ; 2 wherein, the T C in a solid solution is located between that of two parent compounds; moreover, the T C of solid solutions almost changes linearly with respect to x , such anomalous cases are really scarce. 10,35,36…”

“…[Mn x Zn 1−x (HCOO) 3 ], 6 (o-DMTTF) 2 (Br) x (Cl) 1−x , 7 (Per) 2 [Pt x Au 1−x (mnt) 2 ], 15 [Cl-BzPy][Ni x Pt 1−x (mnt) 2 ] (x = 0-1), 34 [NH 3 NH 2 ] 1−x -[NH 3 OH] x Zn(HCOO) 3 , 3 CMBr x I 1−x and CMBr x Cl 1−x ; 2 wherein, the T C in a solid solution is located between that of two parent compounds; moreover, the T C of solid solutions almost changes linearly with respect to x, such anomalous cases are really scarce. 10,35,36 Understanding the phase transition origin and the anomalous changes of both T C and J/k B Theoretically, a regular S = 1 2 AFM linear chain system is thermodynamically unstable owing to the strong spin-lattice interaction, and a spin-Peierls transition occurs at a certain temperature.…”

“…14 In the two-chain solid solution family, (Per) 2 [Pt x Au 1−x (mnt) 2 ] (Per = perylene, mnt 2− = maleonitriledithiolate), metallic systems at high temperatures underwent a Peierls transition towards a CDW ground state at slightly decreasing temperatures in the range of 12 K to 8 K in the low Pt concentration range, while the CDW ground state of the donor chains of perylene coexisted with a spin-Peierls ground state in the anionic chains in the extreme range of high Pt content. 15 The theoretical study unraveled that the two-chain solid solutions (NMP) x (Phen) 1−x TCNQ (NMP = N-methylphenazine, Phen = phenazine, TCNQ = 7,7,8,8-tetracyanopquinodimethane) show three different types of CDW instabilities, i.e., the electrons are delocalized in (1) each type of chain with a 2k F CDW instability as x ≈ 1, (2) the TCNQ chains and the 4k F CDW instability on the TCNQ chains is dominant for 0.5 ≤ x ≤ 0.58, and (3) the TCNQ chains which still presents the 2k F CDW instability together with growing 4k F CDW correlations when x falls in the range of 0.58-1 and approaches to 0.58. 12 Besides regulating the structural and physical properties, it also plays an important role in better understanding the origin of some physical phenomena by investigating the structural and physical properties of solid solutions.…”

Solid-solution (alloying) strategies in crystalline molecular conductors

“…Different elements can be probed simultaneously, as for example S vs. Se in (TSF)x(TTF)1−x(TCNQ), 34 [(TMTSF)1−x(TMTTF)x]2PF6, 43 49 The method however requires that a complete data set is collected and refined for each composition while EDS methods (see above) provide comparable precision in a much faster way. On the other hand, the method gives a precise indication on the evolution of the structure (unit cell, molecular orientations) with x.…”

“…113 This metallic α-phase was still observed in the alloys for x < 0.50 or x > 0.95 while in the intermediate range 0.50 ≤ x ≤ 0.95, the salt adopts another structural β-type associated with a semiconducting behavior on the whole temperate range. 49 One of the most investigated system along these lines is the λ-(BETS)2MCl4 where the diamagnetic GaCl4 − anion can be substituted by the high-spin Fe III FeCl4 − anion (S = 5/2). 92,93 Indeed, λ-(BETS)2GaCl4 undergoes a superconducting transition at ≈ 6 K, and the superconductivity is destroyed under a magnetic field of 13 T parallel to the conduction plane.…”