Probing Nucleic Acid Structure with Shape-Selective Rhodium and Ruthenium Complexes

In this unit, transition metal complexes are used as photochemical probes for the structure of RNA and DNA. The transition metal ion provides a rigid substitutionally inert framework and an octahedral geometry for ligand coordination. The complexes can be constructed to define shapes, symmetries, and functionalities that complement those of the nucleic acid target. Complex formation is easily detected by light-induced nucleic acid cleavage. The modular construction of the complexes makes it possible to generate probes to examine a wide variety of structural characteristics of nucleic acids

Essays in chemistry

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Equilibria in complexes of N-heterocycles. Part 50.1 the formation and properties in solution of the 1:1 adducts of bis(2,2'-bipyridine)platinum(II) and related ions with hydroxide

Equilibrium constants are given for addition (mol ratio 1:1) of hydroxide to several palladium(II) and platinum(II) cations. [Pt(bpy)2]2+ (bpy: 2,2'-bipyridine) and hydroxide ion form the well-known 1:1 adduct rapidly in water; the rate is given at 25°C by k = 1.6 × 102 mol-1 dm3 s-1. The equilibrium constants for adding hydroxide to [Pt(bpy)2]2+ and to [Pt(3,3'-[2H]2-bpy)2]2+ are the same, but differ considerably from those for [Pt([2H]8-bpy)2]2+ and for [Pt(6,6'-[2H]2-bpy)2]2+ with hydroxide. In this reaction, the infrared spectrum (1700-900 cm-1) of the cation initially [Pt(bpy)2]2+ in the aqueous solution shows distinct changes between pH = 7.0 and pH = 11.0, notably in the aromatic region, where the intensity of the band due to C=N at ca. 1600 cm-1 is much reduced. At pH = 7.0, the methyl groups in [Pt(5,5'-dmbpy)2]2+ (dmbpy: dimethyl-2,2'-bipyridine) or the 4,4'-isomer are equivalent in 1H magnetic resonance but become inequivalent in the 1:1 adducts with hydroxide. In the presence of (-)-methylbenzylamine, both [Pt(terpy)Cl]Cl (terpy: 2,2',2¨-terpyridine) and [Pt(bpy)2]2+ manifest a strong Pfeiffer effect, but not the 'exciton' coupling characteristic of cis-octahedral ions. These observations are interpreted in terms of addition of hydroxide to the bipyridine ligands