The use of 3,3-bis(2-imidazolyl) propionic acid (bip-OH) as a new chelating ligand for Re(CO)3 and Ru complexes:: Formation of organometallic PNA oligomers with (bip)Re(CO)3 and their interaction with complementary DNA

We report the use of 3,3-bis(2-imidazolyl) propionic acid (bip-OH, 1) as a new chelating bis(imidazole) ligand. The synthesis and full characterization of complexes Re(bip-O)(CO)(3) 2 and [Ru(bpy)(2)(bip-OH)](2+) 3 is reported. Both complexes show interesting spectroscopic properties, namely IR for compound 2 and H-1 NMR for 3, respectively. The free carboxylic acid functionality of 1 may be used for the coupling to biomolecules. We have prepared two peptide nucleic acid (PNA) decamers to which the rhenium complex 2 is coupled. All reactions were carried out by solid phase synthesis methods. The Re-PNA oligomer conjugates Re(CO)3(bip- tgt eta gca a -NH2) 4 and Re(CO)(3)(bip- agg age aac t-Lys-NH2) 5 were obtained in good yield and high purity after HPLC purification and identified by their mass spectra. The interaction of 5 with complementary DNA yields a melting temperature of (53.9 +/- 1) degreesC. This is the first DNA melting temperature reported for an organometallic metal-PNA conjugate. (C) 2004 Published by Elsevier B.V.