Abstract
During the last decade, polyazaaromatic Ru(II) complexes have been developed as molecular tools for the study of the genetic material. Useful Ru(II) photoprobes could be designed by taking advantage of the great sensitivity of their luminescent properties toward their micro-environment [1]. Complexation of the Ru centre with p-deficient ligands such as TAP (1,4,5,8-tetra-azaphenanthrene), which provide a high oxidising power in the excited state, has also led to new photoreactive agents toward DNA [2] and could lead to biomedical applications.
Recently, increasing efforts have been made to study the possible stereoselectivity of interaction of Ru(II) complexes with the chiral DNA double helix. Therefore, the optical resolution of Ru(II) polyazaaromatic complexes has been developped according to different strategies. In this work, we present the synthesis and optical resolution of Ru(II) precursor complexes aimed to be used as "Chiral Building Blocks" [3]. In this general strategy, optical resolution is achieved with a precusor complex [Ru(L)2(pyridine)2]2+ for which the replacement of the two pyridine ligands by a chosen bidentate ligand occurs with retention of the absolute configuration to yield Ru(II) optically pure complexes. The synthesis and resolution of the precursor bearing phen (1,10-phenanthroline) ancillary ligands has been described in the litterature [3] and allows the design of chiral photoprobes of DNA whereas the TAP analogue should give the resulting complex properties of photoreactivity.
D-[Ru(phen)2(pyridine)2]2+ has been obtained by diastereoisomeric crystallisation with 96% e.e. (as determined by polarimetry measurements) but our different attempts to optically resolve the TAP analogue have not yet been successful probably because of the high polarity of this complex.
[1] B. Norden, P. Lincoln, B. Akerman, E. Tuite, "DNA Interactions with Substitution-Inert Transition Metal Ion Complexes", in Metal Ions in Biological Systems, 1996, vol. 33, p. 177
[2] A. Kirsch-De Mesmaeker, J.-P. Lecomte, J.M. Kelly, "Photoreactions of Metal Complexes with DNA, Especially Those Involving a Primary Photo-Electron Transfer", in Topics in Current Chemistry: Electron Transfer II; Springer Verlag, 1996, vol. 177, p. 25