Excited and ionic states of polymers with pendant phenanthryl groups in solution. Model systems for photophysics in phenanthrene aggregates

Using N₂ gas laser and picosecond Nd³⁺:YAG laser photolysis systems, we measured the transient absorption spectra of 9-ethylphenanthrene (EPh), 1,3-di-(9-phenanthryl)propane (DPhP), poly[2-(9-phenanthryl)ethyl vinyl ether] (PPhEVE), and poly(9-vinylphenanthrene) (PVPh) in solution. The S_n ← S₁ absorption spectrum is almost common to the present compounds, indicating a very weak interchromophore interaction in the excited singlet state. The absorption spectrum of the triplet and cationic states changes from compound to compound, while the spectra of their anion radicals are identical. The triplet excitation and the positive hole can be stabilized easily by forming excimer and dimer cation, respectively, whose conformations are discussed in detail. In the case of polymer systems, plural dimer sites with different geometries exist, which is due to the stacking effect of chromophores. On the other hand, the negative charge is always trapped as a monomer anion. On the basis of the present results, the photophysics of phenanthrene aggregates is discussed.