AbstractWe 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)(O₂CEt)]⋅H₂O. The latter when used to hydrolyse 1,3,4,6-tetrathiapentalene-2,5-dione (TPD), in the presence of NiCl₂, forms a new material whose elemental composition is in accord with the formula [(EtCO₂Ba)₄Ni₈{(O₃S)₂C = C(SO₃)₂}₅]⋅22H₂O (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