Planar-rotor architecture based pyrene-vinyl-tetraphenylethylene conjugated systems: photophysical properties and aggregation behavior.

Four pyrene-vinyl-tetraphenylethylene based conjugated materials were synthesized and characterized by FT-IR, NMR, and mass spectroscopy. The photophysical (including absorption, fluorescence, and fluorescence lifetime) and aggregation properties in tetrahydrofuran were investigated. The photophysical and aggregation behavior depends on the spacer, substituent, and also the architecture (mono or tetra-branched) of the molecule. The vinyl spacer mono-branched compound is aggregation induced emission (AIE) active (αAIE = ∼6). Vinyl spacer tetra-branched compounds are AIE inactive, but their emitting efficiency is good in both solution (Φfl = 63%) phase and in the aggregated state (Φfl = 43%). Phenylvinyl spacer tetra-branched compounds emit light strongly in solution (Φfl = 92%), but not in the aggregated state (Φfl = 8%). They are shown to be thermally stable and emit light in the green region (500-550 nm). The results of cyclic voltammetry measurements of these materials showed irreversible oxidation waves, and have high HOMO energy levels (-5.66 to -5.53 eV).

Binding of hairpin polyamides to DNA studied by fluorescence correlation spectroscopy for DNA nanoarchitectures.

We have recently constructed a "DNA strut" consisting of two DNA-binding hairpin polyamides of Dervan-type connected via a long flexible linker and were able to show that this strut can be used to sequence-selectively connect DNA helices. This approach provides a second structural element (besides the Watson-Crick base pairing) for the assembly of higher-order DNA nanoarchitectures from smaller DNA building blocks. Since none of the existing analytical techniques for studying this kind of system were found suitable for detection and quantification of the formation of the resulting complexes, we chose fluorescence correlation spectroscopy (FCS). In the present study we show that FCS allowed us in a versatile and fast way to investigate the binding of Dervan polyamides to DNA. In particular it also shows its power in the quantitative detection of the formation of multimeric complexes and the in investigation of binding under nonphysiological conditions.