The asymmetric unit of 3 consists of one (A in Figure 2 below) and two halves (B and C) of BETS, one isethionate and one water molecule. The anion and the water molecule are disordered as schematically shown in Figure 3a, in which there are two anions having different conformations, which are superimposed at the same position. The crystal structure is shown in Figure 3b. The space group is P1̲
, so four BETS molecules, two anions and two water molecules exist in the unit cell. Figure 3c shows the packing arrangement of a BETS layer, where A′ is a centrosymmetric ally inverted A. The layer has an α-type packing motif with short side-by-side chalcogen–chalcogen contacts, indicating that the salt has 2D conducting layers. The ratio of donor to anion is 2:1 which suggests that the salt would show low resistivity (vide infra). Figure 3d shows a packing arrangement of the anion/water layer. Because there are two molecular configurations (ρ and σ) in the same position and two anion positions (I and II), there are four possible patterns ((1)–(4) in Figure 3d), where ρ′ and σ′ are centrosymmetric ally inverted ρ and σ, respectively. In addition, patterns (1) and (2) are centrosymmetric but (3) and (4) are not exactly centrosymmetric.