| Abstract
| - Several photoactive platinum α-diimine intercalators have been prepared to develop new probes of DNA oxidationand reduction chemistry. Five water-soluble bis(mes‘)Pt(II) complexes (mes‘ = N,N,N,3,5-pentamethylaniline) withvarious aromatic α-diimine ligands (dppz = dipyridophenazine, np = naphtha[2,3-f][1,ω]phenanthroline, CN-np =naphtho[2,3-f][1,10]phenanthroline-9-carbonitrile, CN2-np = naphtho[2,3-f][1,10]phenanthroline-9,14-dicarbonitrile,and bp = benzo-[f][1,10]phenanthroline) were synthesized. The complex [(np)Pt(mes‘)2]Cl2 was also characterizedby X-ray crystallography, and the crystal structure shows that the ortho-methyl groups of the mes‘ ligands convenientlyblock substitution at the vacant sites of platinum without overlapping with the intercalating α-diimine ligand. ThePt(II) complexes were found to have excited-state oxidation and reduction potentials of −0.6 to −1.0 and 1.0 to 1.5V versus NHE, respectively, making them potent photoreductants as well as photooxidants. Many of the complexesare found to promote the photooxidation of N2-cyclopropyldeoxyguanosine (dCpG). Photoexcited [(dppz)Pt(mes‘)2]2+is found to be most efficient in this photooxidation, as well as in the photoreduction of N4-cyclopropylcytidine (CpC);these modified nucleosides rapidly decompose in a ring-opening reaction upon oxidation or reduction. Photoexcited[(dppz)Pt(mes‘)2]Cl2, upon intercalation into the DNA π stack, is found, in addition, to promote reductive and oxidativedamage within the DNA duplex, as is also probed using the kinetically fast electron and hole traps, CpC and CpG.These Pt complexes may therefore offer useful reactive tools to compare and contrast directly reductive and oxidativechemistry in double helical DNA.
- Platinum α-diimine complexes have been prepared that are both potent photooxidants and photoreductants and thus serve to promote oxidative and reductive DNA damage. Photoreactions with nucleosides and duplex DNA are probed sensitively using cyclopropylamine-substituted cytosine and guanosine as fast electron and hole traps.
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