Oxidizing polyazaaromatic Ru(II) complexes containing two TAP ligands (TAP = 1,4,5,8-tetraazaphenanthrene) are able under illumination to cross-link irreversibly the two strands of an oligonucleotide (ODN) duplex by covalent bond formation. The cross-linking proceeds by two successive absorptions of a photon. An adduct of the metallic complex on a guanine (G) base of one ODN strand is first photoproduced, followed by a second photoaddition of the same Ru species to a G base of the complementary strand, provided that the two G moieties are separated by 0 or 1 base pair. These two processes lead to the cross-linking of the two strands. Such a photo-cross-linking is easily detected with [Ru(TAP)(2)(phen)](2+) (1; phen = 1,10-phenanthroline) and [Ru(HAT)(2)(phen)](2+) (2; HAT = 1,4,5,8,9,12-hexaazatriphenylene), whereas it is not observed with [Ru(TAP)(2)TPAC](2+) (3; TPAC = tetrapyridoacridine) at the same level of loading of the duplex by 3. With a concentration of 3 similar to that of 1 and 2, when the loading of the duplex by 3 is much more important than with 1 and 2, the photo-cross-linking with 3 can thus also be observed. As 3 intercalates its TPAC ligand into the base pairs stack, its mobility is restricted in the duplex. In contrast, 1 and 2 can adopt different geometries of interaction, which probably facilitate the photo-cross-linking.

The optically active cyclometalated Rh(III) complexes, delta[Rh(thpy4,5p(R,R)py)(2)TAP]Cl, lambda[Rh(thpy4,5p(S,S)py)(2)TAP]Cl, and delta[Rh(phpy4,5p(R,R)py)(2)TAP]Cl (where TAP = 1,4,5,8-tetraazaphenanthrene, thpy4,5p(R,R)py = (8R,10R)-2-(2'-thienyl)-4,5-pinenopyridine and phpy4,5p(R,R)py = (8R,10R)-2-(2'-phenyl)-4,5-pinenopyridine) have been prepared and characterized. Their photophysics has been examined in parallel with that of rac[Rh(thpy)(2)TAP]Cl and rac[Rh(phpy)(2)TAP]Cl. Their behaviors have been rationalized from results of TD-DFT calculations. The complexes with thienylpyridine (thpy) as cyclometalating ligands exhibit (3)CT (from thpy to TAP) and (3)LC(pi-pi) (centered on thpy) emissions in a solvent matrix at 77 K and one (3)CT luminescence at room temperature. In contrast, with phenylpyridine (phpy), the complexes show only one (3)CT emission (from phpy to TAP) at both temperatures.

Dinuclear and polynuclear metal complexes with octahedral eluent contains NaCl. Modeling the ΛΛ and the ∆Λ isomers of the dinuclear species shows crowding of the pinene centers coordinated to di-or polydentate ligands are often obtained as complicated mixtures of various stereoisomers. groups in both cases; however, the strain can be released by relatively small distortions only in the case of the ΛΛ isomer. Stereospecific synthesis of such species is therefore of high current interest. Chiral derivatives of pyridine can be used NO 3 -cleaves the dichloro bridge, yielding the mononuclear species ∆[Rh(L 2 ) 2 (NO 3 )] (2) in a completely stereoselective for this purpose. Dinuclear µ-chloro-bridged Rh III complexes with two didentate, cyclometalated thienylpyridine-type manner when NaCl is replaced by KNO 3 in the eluent mixture. The molecular structure has been determined by Xligands at each metal center are formed stereoselectively when pinene groups are fused to the pyridine rings. The two ray structure analysis for both the ∆∆ and the mononuclear complex ∆[Rh(L 2 ) 2 (NO 3 )] (2) in order to confirm the octahedral Rh III centers have homochiral configurations, ∆∆ and ΛΛ. The heterochiral diastereomer ∆Λ is not observed. configuration at the metal center.1 H-NMR, 13 C-NMR and CD spectra were measured and the latter shows that the CD With (8R,10R)-2-(2Ј-thienyl)-4,5-pinenopyridine [Hth4,5-(R,R)ppy] the ∆∆ to ΛΛ ratio is 9:1 when the separation activity is solely due to the chirality at the metal center.

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