Chiral Selectivity in the Binding of [4]Helicene Derivatives to Double‐Stranded DNA

Abstract

The interaction of a series of chiral cationic [4]helicene derivatives, which differ by their substituents, with double-stranded DNA has been investigated by using a combination of spectroscopic techniques, including time-resolved fluorescence, fluorescence anisotropy, and linear dichroism. Addition of DNA to helicene solutions results to a hypochromic shift of the visible absorption bands, an increase of fluorescence quantum yield and lifetime, a slowing down of fluorescence anisotropy decay, and a linear dichroism in flow-oriented DNA, which unambiguously points to the binding of these dyes to DNA. Both helicene monomers and dimeric aggregates, which form at higher concentration, bind to DNA, the former most probably upon intercalation and the latter upon groove binding. The binding constant depends substantially on the dye substituents and is, in all cases, larger with the M than the P enantiomer, by factors ranging from 1.2 to 2.3, depending on the dye.

Physicochemical and Electronic Properties of Cationic [6]Helicenes: from Chemical and Electrochemical Stabilities to Far‐Red (Polarized) Luminescence

“…Applications in several fields of chemistry can be foreseen, from bio-imaging to polarized emitting devices. [ 17,27 ]…”

“…It is worth mentioning that 1 - 3 conserve a non-negligible fluorescence quantum yield in water (from 7% for 2 up to 10% for 3 ) which is of importance for possible uses as red bio-imaging probes. [ 5b,17 ]…”

Helicene-Based Chiral Auxiliaries and Chirogenesis

“…Chiral cationic [4]helicenes 191 (Figure 19), having methoxy substituents at the innermost position, were also able to bind with DNA molecules, as evident from a noticeable change in absorption, fluorescence, and CD spectra obtained during the corresponding host-guest studies [102]. It was concluded that the molecular plane of the helicene dye lies essentially parallel to the DNA bases, implying intercalation mode rather than groove binding.…”

Dutch Resolution of a configurationally stable [5]helquat

“…Representative examples are heterohelicenium systems studied by Lacour group or helical dications called helquats developed by our group . These and similar cationic systems promise attractive range of properties and applications that may be complementary to non‐ionic helicenes. For example, they can strongly interact with their environment due to their positively charged helical skeleton.…”

“…For example, they can strongly interact with their environment due to their positively charged helical skeleton. Also, their solubility in aqueous media and electron‐accepting properties associated with their cationic nature can be advantageous.…”