Ruthenate experiments

The second kind of DNA duplex examined had the following base sequence forthenonruthenated strand 5 -ACGACGGTGACG12CTGAGACT-3 [79]. In these experiments G12 on the 32P-labeled strand was either matched with C (G/C) or mismatched with A (G/A) or T (G/T) on the complementary ruthenated strand. 

The luminescence of the hybridized [Ru(phen)2(dppz)]2+ derivative may be used to characterize the molecular assembly (77). Dilution experiments show that intercalation is intramolecular at concentrations <5 mM duplex addition of unmodified duplex to the covalently bound duplex results in <5% change in the luminescence. The results of experiments performed on duplexes containing mismatches in various positions along the duplex are also consistent with intramolecular intercalation. In this series, luminescence is higher for mismatches near the ruthenated end of the oligomer, where the ruthenium complex can intercalate intramolecularly and stabilize the mismatched site. 

Luminescence titrations further demonstrate that the ruthenated duplex behaves as a 15 mer bearing one intercalator (76). As free [Ru(phen)2(dppz)]2+ is added to a solution of unmetallated 15 mer duplex, the luminescence increases linearly until the emission reaches saturation at about three equivalents of ruthenium(II) per duplex, consistent with competitive binding of [Ru(phen)2(dppz)]2+ to the 15-mer duplex and an average binding site size of a little more than four base pairs. When the analogous experiment is conducted with the ruthenated duplex, saturation of luminescence occurs after almost two equivalents of [Ru(phen)2(dppz)]2+ are added. This comparison indicates that the covalently bound ruthenium(II) complex is not displaced by additional intercalators. 

Chirality effects are also reported in the energy transfer from the ruthen-ium(II) polypyridyl complex to the osmium(II) complex in Langumuir-Blodgett (LB) films [76]. In this experiment, the LB film was prepared with [Ru(dp-phen)3]2+ (dp-phen = 4,7-dipheny 1-1,10-phenanthroline) and stearic acid, where the molar ratio was 1 1 to 1 4. The quenching reaction of the ruthenium(II) complex was carried out with optically pure osmium(II) complex, [Os(dp-phen)3]2+. This reaction consists of photoexcitation of the ruthenium(II) and osmium(II) complexes [Eqs. (29) and (30)], spontaneous decays of the excited ruthenium(H) and osmium(II) complexes [Eqs. (32) and (33)], and the energy transfer between the exited ruthenium(II) complex and the osmium(II) complex [Eq. (31)]. 

Hydroxyl group-directed oxidative annulations with alkynes for the production of fluorescent pyrans were reported (Eq. (7.7)) [12]. Not only naphthols but also 4-hydroxycoumarin and 4-hydroxy-substituted quinolin-2-one underwent this ruthenium(II)-catalyzed C-H/O-H bond functionalization process in a highly chemo- and regioselective manner. Competition reactions showed that electron-deficient alkynes are more reactive. Deuterium experiments also revealed a reversible C-H bond ruthenation step via carboxylate assistance. 

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