Synthesis and optical spectroscopy of linear long-chain di-terminal alkynes and their Pt-σ-acetylide polymeric complexes

A variety of straight-chain alkynes with extended π-conjugation through benzene, anthracene and thiophene linker units in the backbone, H-C≡C-R′-C≡C-R-C≡C-R′-C≡C-H (R = p-C ₆H₄, 9,10-C₁₄H₈, 2,5-C ₄H₂S; R′ = p-C₆H₄, p-C ₆H₄-C₆H₄-p) has been synthesized. The alkynyl chromophores with an anthracene spacer unit are highly emissive in solution with luminescence quantum yields of up to 0.5. The platinum σ-acetylide polymeric complexes of the above ligands show strong absorptions associated with metal-to-alkynyl ligand charge transfer (MLCT) transitions. It is clear that the π-conjugation is maintained through the metal centres and the optical gap for the polymer, [Pt(PBuⁿ ₃)₂-C≡C-p-C₆H₄-C≡C-9,10- C₁₄H₈-C≡C-p-C₆H₄-C≡C] _n is lower than for the complexes [Pt(PBⁿ ₃)₂-C≡C-R′-C≡C-R-C≡C-R′- C≡C]_n (R = p-C₆H₄, 2,5-C ₄H₂S; R′ = p-C₆H₄; p-C ₆H₄-C₆H₄-p).