Metal-nucleobase binding

N, C, O), or indirectly via its others ligands. This latter possibility includes hydrogen bond formation—for example, between aqua or amine ligands and suitable acceptors of the nucleobase. A number of excellent reviews have been published about this topic. Taking into account the direct metal-nucleobase binding, a few general rules can be summarized ... 

The aim of the present chapter is to look at the structures of transition-metal-oxalate complexes with nucleobases as a valuable source of information on molecular recognition patterns controlling the formation of these systems. Therefore, we focus our attention not only on the metal-nucleobase binding modes but also on the intramolecular interligand interactions, which cooperate with the coordination bond in the stabilization of the resulting mixed-ligand complexes. 

One approach, pursued by two groups in particular, is to use model nucleobases that feature an additional metal-ion binding group. Gokel and co-workers have used this strategy with aza-crown derivatives (50,51). X-ray crystallography of 6is-(3-(l-thyminyl)propyl)-4,13-diaza-18-crown-6, 4, reveals the Na+ is coordinated by T-02 [Na-0 distances 2.488 and 2.468 Al (51). Aza-crown derivatives with multiple base substi-... 

A series of amine-tethered nucleobases such as 8 has also been developed. These ligand systems have allowed the interaction of d-block metal ions with the N3pUrine site to be probed and an indication of base-specific metal-ion binding has begun to emerge (55-58). 

There have been few reports of purine derivatives1 that contain metal-carbon nucleobase binding (75), and those that have been described are often polymetalated (84). Quite recently mononuclear complexes of adenine and guanine have been prepared that contain... 

The availability of different metal ion binding sites in 9-substituted purine and pyrimidine nucleobases and their model compounds has been recently reviewed by Lippert [7]. The distribution of metal ions between various donor atoms depends on the basicity of the donor atom, steric factors, interligand interactions, and on the nature of the metal. Under appropriate reaction conditions most of the heteroatoms in purine and pyrimidine moieties are capable of binding Pt(II) or Pt(IV) [7]. In addition, platinum binding also to the carbon atoms (e.g. to C5 in 1,3-dimethyluracil) has been established [22]. However, the strong preference of platinum coordination to the N7 and N1 sites in purine bases and to the N3 site in pyrimidine bases cannot completely be explained by the negative molecular electrostatic potential associated with these sites [23], Other factors, such as kinetics of various binding modes and steric factors, appear to play an important role in the complexation reactions of platinum compounds. 

Examples of three metal ions binding simultaneously to a neutral nucleobase in its preferred tautomeric structure are scarce. One example, with Pt(II) at N7 of 9-MeA and Ag+ at N1 and N3 (132), gives rise to a helical polymer in the solid state. The effect of the three metal ions on the acidity of the exocyclic amino group has not been determined. 

Monofimctional metal-nucleobase bonds constitute the usual mode of metal binding to nucleotides and... 

Attempts to model the intrastrand d(GpG) crosslink with nucleobases have met with only moderate success. Usually the 06 atoms of the two guanosine rings are on opposite sides of the platinum coordination plane ( head-to-tail isomer). Only for cw-[Pt(NH3)2(9-EtG)2] was the correct isomer obtained. Nucleobase complexes of the ds-diammineplatinum(II) moiety have been valuable for testing the controversial proposal of N7,06 chelate formation, which to date has not been observed. Several interesting discoveries of metal-nucleobase chemistry are that metal binding can stabilize rare tautomers, for example, the... 

Nosenko Y, Menges F, Riehn C, Niedner-Schatteburg G (2013) Investigation by two-color IR dissociation spectroscopy of Hoogsteen-type binding in a metalated nucleobase pair mimic. Phys Chem Chem Phys 15 8171-8178... 

The determination of crystal structures for many platinum metal—nucleobase complexes has elucidated many of the binding features, although the foregoing discussion is evidence of the complexity of these mixtures in solution. The bases studied range from unsubstituted purines and pyrimidines to the nucleosides and nucleotides. One feature of this area is the general difficulty of obtaining suitable crystalline samples of the sugar... 

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