Among the various thiophene-based polymers, polythienylenemethylidenes (PTMs) are a promising class of materials that feature a backbone consisting of alternating thienylene and methine units. Their unique structure, in which oxidized quinoids alternate with thiophene units, results in a narrower bandgap compared to that of simple polythiophenes. Further bandgap reduction can be achieved by incorporating bithiophene or terthiophene units instead of a single thiophene units. Additionally, PTMs offer synthetic versatility through the introduction of substituents, most commonly aryl groups, at the methine carbons. This substitution capability enables the finetuning of material properties. For instance, Akagi at al. demonstrated that incorporating long-chain substituents capable of liquid crystalline behavior can enhance the solubility and stability of PTMs. Despite their promising properties, the stereochemistry of the PTMs remains largely unknown. Double bonds at the methine carbons can potentially exist in either E-or Z-configurations. Previous studies on PTM stereochemistry are limited. While quantum chemical calculations on PTMs containing ethylenedioxy groups at the β-position of thiophenes suggest a planar structure with alternating E-and Z-configurations, stabilized by potential S•••O chalcogen bonding, investigations of simple PTMs are scarce. Few studies have focused on methine-bridged trithiophene fragments which can exist in three isomeric forms (ZZ, EZ/ZE, and EE) because of the E/Z isomerism of the double bonds. A well-documented study examining trithiophenes with cyclopentadienyl anion substituents at the methine carbon demonstrated the preferential formation of the EE isomer through careful nuclear magnetic resonance (NMR) and NOE analyses, attributing this preference solely to steric effects. Although this work provides valuable structural insights, the highly specific nature of the cyclopentadienyl anion limits its broader applicability to more conventional PTM systems. A recent report by Bonomo et al. suggested that the isomers observed in aryl substituted trithiophene systems were conformers arising from the rotation of the terminal thiophene rings in the ZZ isomer rather than geometric isomers. In this study, we focused on the potential for chalcogen bonding between adjacent sulfur atoms in the ZZ configuration of methine-bridged trithiophenes. We hypothesized that these S•••S interactions might stabilize the ZZ isomer relative to the EZ and EE configurations. This hypothesis is supported by the well-documented ability of thiophene sulfur atoms to participate in chalcogen bonding through their σ* orbitals along the C-S bonds, as well as their role as Lewis bases, facilitated by their lone pair (LP) electrons.