Metallocene–nucleobase conjugates. Synthesis, structure and nucleic acid binding

The ferrocenylnucleobase conjugates [Fe(η5-C5H5){η5-C5H4CH2NMe2CH2CH2CH2[graphic omitted]H}][BF4]1 and [Fe(η5-C5H5){η5-C5H4CH2[C5H2N4(NH2)]}]2 of thymine and adenine respectively, have been prepared and their crystal and molecular structures determined. The molecular packing of the two compounds differs markedly in terms of intermolecular hydrogen-bonding interactions. In 1 such interactions are confined to discrete cation ⋯ anion ⋯ solvate units, whereas in 2 the hydrogen-bonding patterns are extensive and involve both the Watson–Crick and Hoogsteen donor and acceptor sites. Electrochemical studies of the interaction of 1 with nucleic acids showed that the incorporation of this single nucleoside base with the metallocene moiety enhances the binding in aqueous solution compared to a cationically charged derivative devoid of this functionality. Moreover, with immobilised nucleic acid, binding was observed exclusively for the conjugate 1.