Mono and bisubstituted bis(ethynyl)biphenyl Pt(II) complexes, i.e. trans-[(R-C equivalent toC-)Pt(PPh3)(2)(-C equivalent toC-p-C6H4-p-C6H4-C equivalent toC-H)], R = p-NO2C6H4 (3b), (eta (5)-C5H5)Fe(eta (5)-C5H4) (3c), and trans-[(R-C equivalent toC-)Pt(PPh3)(2)(-C equivalent toC-p-C6H4-p-C6H4-C equivalent toC-)Pt(PPh3)(2)(-C equivalent toC-R)], R = C6H5 (4a), p-NO2C6H4 (4b), (eta (5)-C5H5)Fe(eta (5)-C5H4) (4c), have been synthesized by the dehydrohalogenation reaction from the appropriate Pt monochloro acetylides trans-[(RC equivalent toC)Pt(PPh3)(2)Cl], R = C6H5 (1a), R =p-NO2C6H4 (1b), R = (eta (5)-C5H4)Fe(eta (5)-C5H5) (1c) and HC equivalent toC-p-C6H5-p-C6H5-C equivalent to CH, (4,4'-bis-ethynylbiphenyl), (DEBP) (2). In order to make possible a direct evaluation of the role of Pt centers on the properties of these highly ethynylated complexes, the corresponding species without Pt were prepared, i.e. C6H5-C equivalent toC-C equivalent toC-C6H4-C6H4-C equivalent toC-C equivalent toC-C6H5, (4,4'-(bis-phenylethynyl)-diethynylbiphenyl) (7), and (eta (5)-C5H5)Fe(eta (5)-C5H4)-(C equivalent toC-C equivalent toC-C6H4-C6H4-C equivalent toC-C equivalent toC)-(eta (5)-C5H4)Fe(eta (5)-C5H4)Fe(eta (5)-C5H5), (4,4 '-(bis-ferrocenylethynyl)-diethynylbiphenyl) (8). Preparation of the latter compounds was only achieved by the use of the palladium catalyzed Stille coupling reaction, since the dehydrohalogenation route afforded only homocoupled and polymeric products. The electron-donor or electron-withdrawing ligands coordinated to Pt were chosen for the purpose of tuning the optical properties of the complexes through the different charge distribution along the pi -electron conjugation. Characteristic spectroscopic features (UV-vis, FT-IR and NMR) of these complexes are discussed.