Crystal structure and physical properties of a metallic charge-transfer salt: (BEDT-TTF)₂Ag(CN)₂.H₂O

Abstract

A new organic salt, bis[3,4;3',4'-bis(ethylenedithio)2,2',5,5'-tetrathiafulvalenium] dicyanoargentate(I) monohydrate [(BEDT-TTF)2Ag(CN)2.H20] (I), has been synthesized and its crystal structure and physical properties determined. The structure of (I) is different from those of the superconducting (fl), metallic (fl) and insulating (fl' and a') phases of anhydrous (BEDT-TTF)2X, where X is a triatomic monoanion, but is similar to the newly found superconducting salts x-(BEDT-TTF)213 and (BEDT-TTF)2Cu(NCS)2. Crystal data for (I): [C10HsS8]2[Ag(CN)2].H20, Mr=9472, monoclinic, P21, a = 12.593 (3), b = 8.642 (1), c = 16.080 (3) A, fl =109.33(2) ° , U =1651.2(5) A 3, Z=2, Dx= 1.905 g cm -3, Mo Ka X-radiation (graphite monochromator), ,~ = 0.71069 A, # = 16.03 cm-~, F(000) = 950, T= 298 K, R (wR) = 0-033 (0.034) for 3884 unique observed [F> 2o-(F)] data. The anion array consists of linear chains of three-coordinate Ag atoms linked by H20 to form layers parallel to the BEDT-TTF layers, with which they form. alternating stacks parallel to c. (I) is metallic over the temperature range 150-300 K. The EPR spectrum at 295 K consists of a single line at g = 2.007 (3), with a peak-to-peak width Hpp of 70 G (0.007 T). Between 50 and 300 K an activated spin susceptibility with Ea = 0.01 eV is observed.