Metallic Bi- and Monolayered Radical Cation Salts Based on Bis(ethylenedithio)­tetrathiafulvalene (BEDT-TTF) with the Tris(oxalato)gallate Anion.

New metallic triclinic ( 1) and monoclinic ( 2) crystals of the (BEDT-TTF)₄A^I[M^III(C₂O₄)₃]G family of organic molecular conductors have been prepared: α-'pseudo-κ'-(BEDT-TTF)₄K _x(H₃O)_{1- x}[Ga^III(C₂O₄)₃] ·1,2-C₆H₄Br₂ ( x ≈ 0.45) ( 1) and β″-(BEDT-TTF)₄K _x(H₃O)_{1- x}[Ga^III(C₂O₄)₃] ·PhBr ( x ≈ 0.33) ( 2). The triclinic crystals belong to a quite rare type of bilayered radical ion salts and contain alternating BEDT-TTF layers with two distinct packing motifs (α- and 'pseudo-κ'). The monoclinic crystals contain one kind of BEDT-TTF radical cation layers. The crystal structure, transport, and magnetotransport properties of 1 and 2 have been studied. The Shubnikov-de Haas (SdH) oscillations were found in both phases. The structure and properties of 1 and 2 are compared with another similar phase with M = Fe^III. [ABSTRACT FROM AUTHOR]