Uracil-fused and isocytosine-fused tetrathiafulvalenes (TTF) are compounds easily synthesised from barbituric acid and its derivatives. The compounds can be easily oxidised, they form cation-radical salts and at the same time intermolecular hydrogen bonds with complementary components enhancing the electroconductivity of crystalline samples. The formation of hydrogen bonds produces changes in the ultraviolet absorption spectra of compounds and in their redox properties: it may be used for the recognition complementary components of nucleic acids. An oligonucleotide containing a TTF group has been synthesised and its redox activity studied.