Optoelectronic properties of quasi-linear, self-assembled platinum complexes: Pt-Pt distance dependence

Charge-carrier mobilities of various self-assembled platinum complexes were measured by time-resolved microwave conductivity techniques in the temperature range -80 to +100degreesC. Eight compounds were investigated in the present study, including the original. Magnus' green salt ([Pt(NH3)(4)][PtCl4]) and derivatives with the general structure [Pt(NH2R)(4)][PtCl4], where R denotes an alkyl side chain. In one instance, the chlorines were substituted with bromines. For these complexes, which all consist of a linear backbone of platinum atoms, with Pt-Pt distances, d, varying from 3.1 to greater than or equal to 3.6 Angstrom, a strong, inverse correlation was found between d and the one-dimensional charge-carrier mobility, Sigmamu(1D). The highest value of Sigmamu(1D) at room temperature was observed for R = (S)-3,7-dimethyloctyl (dmoc) with Sigmarho(1D) greater than or equal to 0.06 cm(2) V-1 s(-1). Almost all materials exhibited a charge-carrier mobility that was relatively independent of the temperature, over the range studied. One exceptional compound (R = (R)-2-ethylhexyl) showed a pronounced negative temperature dependence of the charge-carrier mobility; upon decreasing the temperature from +100 degreesC to -80 degreesC the charge-carrier mobility increased by a factor of about ten.