Impact of the Supramolecular Organisation of Pyrene – Quinoline Conjugates on their Interaction with ds – DNA

Two novel pyrene – quinoline conjugates differing in the linker flexibility between aryls were prepared. In comparison with referent pyrene derivative, both conjugates showed intramolecular pyrene – quinoline stacking in aqueous medium, much more efficient for rigid conjugate. Consequently, only rigid conjugate showed excimer fluorescence with exceptionally strong bathochromic shift (+ 55 nm) of emission maximum in respect to referent pyrene analogue and flexible conjugate. All studied compounds showed similar, 10 μmol dm−3 affinity toward ds – DNA, characterised in general by fluorescence quenching. The flexible conjugate showed at large excess of DNA over dye formation of pyrene – quinoline excimer, while rigid conjugate retained excimer emission throughout all DNA concentrations. Lack of significant thermal stabilisation of ds – DNA by studied compounds and minor changes in CD spectrum of DNA supported non – specific agglomeration of both conjugates and referent pyrene analogue within hydrophobic DNA grooves as the dominant binding mode.