Chemistry Reference
In-Depth Information
Figure 5.8
Different ratio of HH and HT conformers in adducts with G (top) and 5,6
dimethylbenzimidazole (bottom). The scheme does not intend to take into account the chiral-
ity of the HT conformer (
D
or
Λ
) (Ref. 119 for related work)
otides.
81,104,105
This is not the case for the previous two types of internucleotide
interactions which involve parts of ligands close to the metal and can be referred
to as ' fi rst - to - fi rst sphere communication' (FFC). SSC interactions are optimal at
pH 6-7, conditions in which the phosphate group is deprotonated while N1 is still
protonated.
Further support for the conclusion that in
cis
- A
2
Pt(5
- GMP)
2
complexes the
LHT conformer is favoured by G phosphate/N1H
cis
G hydrogen bonding (SSC)
came also from our recently reported X-ray crystal structure of Me
4
en - Pt(5
′
-
GMP)
2
.
118
Three unique features not present in all other
cis
- A
2
Pt(GMP)
2
solid - state
structures were found: a LHT conformation, very strong hydrogen-bond interac-
tions between phosphate and N1H of
cis
nucleotides, and a very small dihedral angle
between the planes of the two guanines, although both were nearly perpendicular
to the coordination plane.
′
