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 +100 °C. 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 ≥ 3.6 Å, a strong, inverse correlation was found between d and the one-dimensional charge-carrier mobility, Σμ1D. The highest value of Σμ1D at room temperature was observed for R = (S)-3,7-dimethyloctyl (dmoc) with Σμ1D ≥ 0.06 cm2 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 °C to –80 °C the charge-carrier mobility increased by a factor of about ten.