Radical ion states of platinum acetylide oligomers

The ion radicals of two series of platinum acetylide oligomers have been subjected to study by electrochemical and pulse radiolysis/transient absorption methods. One series of oligomers, Pt-n,, has the general structure Ph-C C-[Pt(PBU3)(2)-C C-(1,4-Ph)-C C-],-Pt(PBU3)2-C C-Ph (where x = 0-4, Ph = phenyl and 1,4-Ph = 1,4-phenylene). The second series of oligomers, Pt4Tn,,, contain a thiophene oligomer core, -C C-(2,5-Th),,-C C- (where n = 1-3 and 2,5-Th = 2,5-thienylene), capped on both ends with -Pt(PBU3)2-C C-(1,4-Ph)-C C-Pt(PBU3)2-C C-Ph segments. Electrochemical studies reveal that all of the oligomers feature reversible or quasi-reversible one-electron oxidation at potentials less than 1 V versus SCE. These oxidations are assigned to the formation of radical cations on the platinum acetylide chains. For the longer oligomers multiple, reversible one-electron waves are observed at potentials less than 1 V, indicating that multiple positive polarons can be produced on the oligomers. Pulse-radiolysis/transient absorption spectroscopy has been used to study the spectra and dynamics of the cation and anion radical states of the oliomers in dichloroethane and tetrahydrofuran solutions, respectively. All of the ion radicals exhibit two allowed absorption bands: one in the visible region and the second in the near-infrared region.