Phenanthroline complexes intercalation

Tris(phenanthroline) complexes of ruthenium(II), cobalt(III), and rhodium(III) are octahedral, substitutionally inert complexes, and as a result of this coordina-tive saturation the complexes bind to double-helical DNA through a mixture of noncovalent interactions. Tris(phenanthroline) metal complexes bind to the double helix both by intercalation in the major groove and through hydrophobic association in the minor groove. " " Intercalation and minor groove-binding are, in fact, the two most common modes of noncovalent association of small molecules with nucleic acids. In addition, as with other small molecules, a nonspecific electrostatic interaction between the cationic complexes and the DNA polyanion serves to stabilize association. Overall binding of the tris(phenanthroline) complexes to DNA is moderate (log K = 4)." ... 

Typical OH-scavengers suppress this reaction of (OP)2Cu+ (Que et al. 1980) yet, acetate and benzoate seem to be equally efficient, despite the fact that acetate is nearly two orders of magnitude less reactive towards OH than benzoate (k=7 X 107 dm3 mol-1 s 1 vs k = 5 X 109 dm3 mol-1 s 1 Buxton et al. 1988), and obviously it is not a freely diffusing OH that is responsible for the reaction. The reaction is also suppressed by Cu-complexing compounds and by transition metal ions such as Zn2+, Co2+, Cd2+ and Ni2+ that form stable complexes with 1,10-phenanthroline (Que et al. 1980) and also by competitive intercalators such as ethidium bromide and 2,9-dimethyl-l,10-phenanthroline (Reich et al. 1981). Interestingly, compared to its parent, the latter is inactive. NADH may serve as a reductant, but 02, seems to be a salient intermediate in this cleavage reaction, because cleavage is fully suppressed in the presence of SOD (Reich et al. 1981). 

Researchers have also studied DNA-mediated electron transfer by using donor-acceptor pairs that bind DNA noncovalently (27-30). Early work in our laboratory used cationic tris(phenanthroline) metal complexes as donor-acceptor pairs (29, 30). These complexes, shown in Figure 1, associate with DNA through two modes, (i) intercalation and... 

Herein we wish to report another approach, namely the use of the coordination complexes and bulky organosulfonate counter anions as building blocks, to generate porous ionic network which intercalates 1,10-phenanthroline or water guest molecules. The structures of adduct [Co(trien)(phen)](l,5NDS), 5 (phen)2 (H20)8 (1) and... 

Intercalation of the luminescent cyclometalated [Pt(C6ANAN)(MeCN)]+ 46 (HC6ANAN=2,9-diphenyl-l,10-phenanthroline) and [Pt2(C1 ANAN)2(/U-dppm)]2+ 7b complexes into calf-thymus DNA leads to a dramatic enhancement of their photoluminescence [16d]. The intercalation is likely to prohibit the solvent-induced quenching process, which typically occurs at the coor-dinative unsaturated platinum site for the MLCT excited state. The DNA-in-tercalating platinum(II) complex, [Pt(dppz)(tNAC)]CF3S03 (dppz=dipyri-do[3,2-a 2, 3 -c]phenazine, fNACH=4-ferf-butyl-2-phenylpyridine) 47 similarly exhibits an increase in emission intensity at Amax 650 nm on addition of calf thymus DNA (Fig. 22) [46]. 

As discussed above, the tris(phenanthroline)ruthenium(II) complexes offer a novel spectroscopic probe of nucleic acids, since their luminescence is increased upon intercalation into the double helix. As a result the complexes provide a simple luminescent stain for DNA in fluorescent microscopy experiments. More interesting, perhaps, is the conformational selectivity of derivatives of tris(phenanthro-... 

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