In summary, we synthesized and characterized a series of methine-bridged trichalcogenophenes, 1S and 1O, as model compounds to investigate the stereochemistry and chalcogen bonding effects in PTMs. The synthesized compounds were obtained as mixtures of the geometric isomers ZZ, EZ, and EE, whose identities were unambiguously established through detailed NMR analyses. The thermal equilibrium ratios of these isomers showed distinct patterns depending on the chalcogen atom: 1S exhibited a strong preference for the ZZ isomer, whereas 1O showed a near-statistical distribution.