2,1,3‐Benzothiadiazole‐Modified DNA
The use of 2,1,3-benzothiadiazole (BTD) as a structural element with advanced electronic properties for DNA hybrids is described. Bis(alkynyl)- and bis(carboxamide)-derived BTD units are shown to support duplex stability through interstrand stacking interactions. Placement of the BTD units opposite to a natural base, however, leads to considerable destabilization. The bis(alkynyl)-derived BTD W is strongly fluorescent, and quantum yields of up to 0.20 are observed. Its fluorescence behavior is strongly dependent on the neighboring nucleobases. The quenching effect of the natural bases decreases in the order G >> A ≥ T ≥ C and correlates very well with the free energies for charge separation (ΔGCS) through photoinduced electron transfer, as calculated by the Rehm–Weller equation. Fluorescence of W is completely quenched when it is placed against the bis(carboxamide)-derived BTD V. The described BTD-based compounds W and V represent valuable building blocks for the construction of highly ordered, DNA-based materials with special optical and electronic properties.