Abstract
Two novel paramagnetic conductors have been prepared with the organic donor bis(ethylenedithio)tetrathiafulvalene (BEDT‐TTF = ET) and paramagnetic Mn‐containing metallic complexes: κ′‐ET4[KMnIII(C2O4)3]∙PhCN (1) and ET[MnIICl4]∙H2O (2). Compound 1 represents the first Mn‐containing ET salt of the large Day’s series of oxalato‐based molecular conductors and superconductors formulated as (ET)4[AM(C2O4)3]∙G (A+ = H3O+, NH4+, K+, ...; MIII = Fe, Cr, Al, Co, ...; G = PhCN, PhNO2, PhF, PhCl, PhBr, ...). It crystallizes in the orthorhombic pseudo‐κ phase where dimers of ET molecules are surrounded by six isolated ET molecules in the cationic layers. The anionic layers contain the well‐known hexagonal honey‐comb lattice with Mn(III) and H3O+ ions connected by C2O42- anions. Compound 2 is one of the very few examples of ET salts containing ET2+. It also presents alternating cationic‐anionic layers although the ET molecules lie parallel to the layers instead of the typical almost perpendicular orientation. Both salts are semiconductors with room temperature conductivities of ca. 2 x 10-5 and 8 x 10−5 S/cm and activation energies of 180 and 210 meV, respectively. The magnetic properties are dominated by the paramagnetic contributions of the high spin Mn(III) (S = 2) and Mn(II) (S = 5/2) ions.
Highlights
The design and synthesis of multifunctional molecular materials combining electrical and magnetic properties is one of the main challenges in the field of molecular materials [1,2,3,4]
The higher resistance increases the potential of the source needed to apply the desired constant intensity since the electrochemical synthesis is performed under constant current
The combination of the magnetic anion [Mn(C2O4)3]3− with the organic donor ET under different synthetic conditions has resulted in the synthesis of two very original magnetic and conducting radical salts: (ET)4[KMn(C2O4)3]·PhCN (1) and (ET)[MnCl4]·H2O (2)
Summary
The design and synthesis of multifunctional molecular materials combining electrical and magnetic properties is one of the main challenges in the field of molecular materials [1,2,3,4]. This series constitutes, by far, the largest family of paramagnetic superconductors, metals and semiconductors prepared to date In this series, we can distinguish three different crystal structures: (i) a C2/c (#15) monoclinic β phase (Table 1); (ii) an orthorhombic Pbcn (#60) pseudo-κ phase (Table 2) and (iii) a triclinic P1 (#1) or P-1 (#2) αβ or α-pseudo-κ phase (Table 3). The monoclinic C2/c (#15) β phase presents parallel ET molecules, the orthorhombic Pbcn (#60) pseudo-κ phase contains ET dimers surrounded by six monomers, the triclinic phase presents a mixture of alternating θ and β (or θ and pseudo-κ) layers, and, the 3:1 salts present alternating tilted dimers and monomers These structural differences lead to different physical properties: the triclinic and orthorhombic phases are semiconductors (Tables 2–4), whereas the monoclinic salts are metallic or even superconductors (Table 1). We present the synthesis, structure, magnetic and electrical properties of the first example of radical salt of the Day’s series obtained with Mn(III): κ -(ET)4[KMnIII(C2O4)3]·PhCN (1) and of a very original salt obtained with the same [Mn(C2O4)3]3− anion but using different synthetic conditions: (ET)[MnCl4]·H2O (2)
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