A Soluble ‘Ba(Ni-ett)’ (ett = 1,1,2,2-Ethenetetrathiolate) Derived Thermoelectric Material

We describe the synthesis and characterisation of the first of a new class of soluble ladder oligomeric thermoelectric material based on previously unutilised ethene-1,1,2,2-tetrasulfonic acid. Reaction of Ba(OH) 2 and propionic acid at a 1:1 stoichiometry leads to the formation of the previously unrecognised soluble [Ba(OH)(O 2 CEt)]⋅H 2 O. The latter when used to hydrolyse 1,3,4,6-tetrathiapentalene-2,5-dione (TPD), in the presence of NiCl 2 , forms a new material whose elemental composition is in accord with the formula [(EtCO 2 Ba) 4 Ni 8 {(O 3 S) 2 C = C(SO 3 ) 2 } 5 ]⋅22H 2 O ( 4 ). Compound 4 can be pressed into pellets, drop-cast as DMSO solutions or ink-jet printed (down to sub-mm resolutions). While its room temperature thermoelectric properties are modest (σ max 0.04 S cm −1 and Seebeck coefficient, α max − 25.8 μV K −1 ) we introduce a versatile new oligomeric material that opens new possible synthetic routes for n-type thermoelectrics. Graphical Abstract