Fluorescent di-nuclear rhenium(I) complexes bioconjugated with PNA for DNA targeting

New materials for applications both in diagnosis and gene therapy should posses good affinity with DNA, together with some spectroscopic or radiochemical properties. For diagnostic purposes, the conjugation of peptide nucleic acids (PNA) with luminescent rhenium(I) complexes seems to be an interesting tool. Indeed, the former have a high binding affinity for DNA and RNA while the latter have good photoluminescent properties. We have recently published [1] a new family of dinuclear carbonyl rhenim(I) complexes containing 1,2-diazine ligand, whose high PLQY was strongly correlated with the substituent on the diazine ring. Moreover, we have previously reported the stable adduct between thymine-PNA monomer and the complex [Re2(-Cl)2(CO)6(-4-COOH-pydz)] (1) [2]. Owing to the electron-withdrawing of the carbonylic substituent, the PLQY of this adduct was negligble. In order to increase the quantum yield of the bioconjugated compound, we have now synthetized a much more luminescent complex namely [Re2(-Cl)2(CO)6(-4-(CH2)3-COOH-pydz)] (2). Here we report the synthesis and the photophysical characterization of the adducts obtained by the coupling of the homo-thymine PNA decamer with both metal complexes 1 and 2. [1] M. Mauro, E. Quartapelle Procopio, Y. Sun, C.H. Chien, D. Donghi, M. Panigati, P. Mercandelli, P. Mussini, G. D’Alfonso, L. De Cola, Adv. Func. Mat., in press [2] D. Donghi, M. Panigati, G. Prencipe, E. Licandro, S. Maiorana, L. D’Alfonso, Luminescence, 2008, 23, 215