Synthesis, Structures and Properties of Novel Platinum(II) Acetylide Complexes and Polymers with Tri(tolyl)phosphine as the Auxiliary Ligand

A new family of luminescent platinum(II) acetylide complexes and polymers were formed by the copper(I) catalyzed reaction of cis-[PtCl2(PR3)2] (R=C6H5–p-CH3) with appropriate acetylide ligands. The reaction of metal precursors with 2.5 equivalents of monoterminal acetylide ligands provided metal complexes trans-[Pt(p-tolyl3P)2(C≡C-R)2] (R=C6H4-p-NO2 (1) C6H4 -p-CH3 (2)), and equimolar amounts of diterminal ligand and metal chloride precursor, under reflux, afforded the metal poly-yne polymers [-Pt(p-tolyl3P)2C≡C–R–C≡C–]n, (R=biphenyl and 2,5-dioctyloxybenzene). Characterization of the newly developed polymer and metal complexes was accomplished by FT-IR, multinuclear NMR (1H, 31P, 13C) and mass spectrometry, as well as elemental analysis. The molecular structure of the metal complex trans-[Pt(p-tolyl3P)2(C≡CC6H4–p-NO2)2] (1) was confirmed by single crystal X-ray crystallography. The electronic absorption and photoluminescence spectra of the metal complexes and polymers have been used to probe their photophysical properties. The studies reveal that the presence of heavy metal atom and substituent groups on the phenyl ring of the ligands can enhance the efficiency of intersystem crossing from the S1 singlet excited state to the T1 triplet excited state and thus give intense phosphorescence.