Circularly Polarized Light Probes Excited-State Delocalization in Rectangular Ladder-type Pentaphenyl Helices.

Ladder-type pentaphenyl chromophores have a rigid, planar π-system and show bright fluorescence featuring pronounced vibrational structure. Such moieties are ideal for studying interchromophoric interactions and delocalization of electronic excitations. We report the synthesis of helical polymers with a rigid square structure based on spiro-linked ladder-type pentaphenyl units. The variation of circular dichroism with increasing chain length provides direct evidence for delocalization of electronic excitations over at least 10 monomeric units. The change in the degree of circular polarization of the fluorescence across the vibronic side bands shows that vibrational motion can localize the excitation dynamically to almost one single unit through breakdown of the Born-Oppenheimer approximation. The dynamic conversion between delocalized and localized excited states provides a new paradigm for interpreting circular dichroism in helical polymers such as proteins and polynucleic acids.

Electrooxidative generation of polymer films from rigid tricarbazole monomers.

In this report, syntheses and subsequent electropolymerization of a series of five rigid tricarbazole monomers are described. The monomers involve three planar triphenylene-cored tricarbazole-benzenes (with the carbazole units connected via their a- or b-planes) and two triptycene-cored derivatives. Oxidative electropolymerization of these monomers leads to a continuous growth of smooth and freestanding thin films. Moreover, one type of polymer film, based on a poly-a-tricarbazole network (paTC), shows the occurrence of intrinsic microporosity properties, with a specific BET surface area of 260 m2 g-1.