Four (BEDT‐TTF)4A[M(C2O4)3]·DMF (DMF = dimethylformamide) salts of the organic donor molecule bis(ethylenedithio)tetrathiafulvalene (BEDT‐TTF) with metal oxalate anions, where A = (NH4, K), M = Cr (1); A = NH4, M = Fe (2); A = K, M = Cr (3); and A = NH4, M = Cr (3′) were prepared by electrocrystallization. These salts were characterized by single‐crystal X‐ray diffraction, electron spin resonance (ESR) spectroscopy, electrical resistance measurements, and electronic band structure calculations. The structures (with space group C2/c) consist of alternating β″‐type layers of BEDT‐TTF and an approximately hexagonal network formed by the A+ cation and the metal, with the solvent molecule, DMF, occupying hexagonal cavities in the anion layer. All of the salts are two‐dimensional organic metals down to 4.2 K and do not exhibit superconductivity. Their electronic band structure is similar to that of the known organic superconductor β″‐(BEDT‐TTF)4H3O[Fe(C2O4)3]·BN. The ESR spectra of salts 1 and 3′ are characterized by two resonances, one of Gaussian shape arising from the 3d localized electrons of Cr3+ and the other of Lorentzian (and Dysonian) shape due to the conduction electrons in the organic layers. On the basis of the calculated Fermi surfaces it is suggested that these salts could exhibit an interesting magnetoresistance behavior if disorder does not prevent the observation of the Shubnikov‐de Haas oscillations.

A qualitative scheme that leads to the step‐by‐step construction of the band structure and Fermi surface of molecular conductors is developed based on a simple analytical treatment as well as some fundamental symmetry and overlap ideas and the concept of folding. This treatment is valuable in that it provides a detailed understanding of how the crystal and electronic structures of molecular conductors are related. Specifically, the proposed perspective clarifies how relatively weak structural changes can result in significant differences in the transport properties of these materials. Molecular conductors with donor layers of the β″‐type are used in order to illustrate the approach.

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BEDO-TTF) 4 [Fe(CN) 5 NO] was synthesized by electrocrystallization using the nitroprussides M 2 [Fe(CN) 5 NO]?2H 2 O (M~K, Rb) as supporting electrolytes and TCE (1,1,2-trichloroethane) and DCE (1,2dichloroethane) as solvents. The crystal structure of this new salt (a~4.0251(3), b~15.266(2), c~19.259(2) A Ê , a~97.02(1), b~93.23(1), c~96.04(1)³, V~1165.1(2) A Ê 3 , Z~3/4, space group P1 Å ) is characterized by the presence of b@-type radical cation layers and anion layers containing disordered nitroprusside anions. The stoichiometry was con®rmed by a micro-Raman spectroscopic study and the band structure and Fermi surface of this new salt were studied by means of the extended Hu È ckel tight binding method. (BEDO-TTF) 4 [Fe(CN) 5 NO] is a two dimensional metal stable down to liquid helium temperatures.

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