Synthesis and photophysics of platinum capped phenylene ethynylene oligomers

A series of dinuclear platinum-acetylide oligomers PhnPt2 were synthesized, consisting of alkylated phenylene ethynylene oligomers of varying lengths (n = 1, 2, 4 and 9) capped by trans-bis(tributylphosphine)(2phenylethynyl)-platinum(II) end groups.The oligomers were designed to examine the effects on the excited state properties between two platinum moieties of increasing organic spacer distances.Optical data conclude that the ground state and singlet exciton remain delocalized throughout the series, but approaching its limit.The extent of delocalization in the triplet exciton is reached by Ph4Pt2, and phosphorescence yields at ambient temperatures decreased with increasing spacer length until phosphorescence emission was almost elusive in the n = 9 oligomer.Lifetime trends of the singlet and triplet excited states correlate well with the decreasing percent heavy metal character as the organic spacer is lengthened.