DNA Binding of a Molecular‐Scale Receptor in the Presence of Zinc( II ) Ions

The properties of a tritopic artificial biological probe are described. This probe consists of a luminescent pyrene–thiophene unit connected by an ethynylene group to a 2,2':6',2‐terpyridine (terpy) cation binding site. The pyrene unit, as evidenced by fluorescence spectroscopy under illumination at 400 nm, is capable of intercalating into double‐stranded calf‐thymus DNA in H 2 O (buffered, pH = 7.0) at 25 °C. The binding constant K was calculated to be 6.0 × 10 5 M –1 . Titration of zinc( II ) ions in an aqueous (pH = 7.0) solution containing the intercalated probe results in fluorescence quenching which again is a consequence of the zinc( II ) ions binding to the terpy site. The DNA‐bound probe has also been shown to undergo singlet energy transfer to intercalated ethidium bromide with a rate constant of 9.4 × 10 9 s –1 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)