Photophysics of conjugated organometallic systems: Photoinduced electron and energy transfer, triplet exciton delocalization, and phosphorescent organogelators

We designed and synthesized several series of platinum acetylide oligomers. Their photophysical properties were studied by steady-state and time resolved methods towards the objective of studying exciton and charge transfer. The motivation of this research is to provide a clear understanding of the structure and dynamics of triplet excitons and charged states within conjugated systems that feature organometallic repeats.;First, a series of platinum acetylide oligomers that feature a donor-spacer-acceptor architecture was prepared to investigate photoinduced electron transfer dynamics. The thienylene or bithienylene segments (T1 or T2) were used as electron donors, and naphthalene diimides (NDI) were used as electron acceptors. The donor and the acceptor were connected by several platinum acetylide repeat units. Second, photoinduced energy transfer was studied within anthracene-based platinum acetylide oligomers. Third, triplet exciton delocalization was explored in a series of platinum tetrayne oligomers by varying the carbon chain length. Finally, the properties of triplet excitons and charged states were investigated in supramolecular aggregates (and gels) generated by self-assembly of tailored platinum acetylide oligomers that structurally feature long alkyl chains and amide functional groups.;The most important findings of this research are as follows: (i) Photoinduced electron transfer occurs via a direct or an indirect mechanism depending on the excitation wavelength; (ii) photoinduced energy transfer in the anthracene-based platinum acetylide oligomer occurs via a mechanism that starts from a singlet-triplet energy transfer followed by a triplet-triplet energy transfer; (iii) triplet excitons of the platinum tetrayne oligomers are localized and confined within two repeat units; (iv) in the triplet excited states of the aggregated oligomers, the chromophores interact only weakly and the rate of electron transfer is very rapid likely due to triplet exciton diffusion within closely packed oligomers.