Chemistry Reference
In-Depth Information
Figure 4.20
Structure of the 1D coordination polymer [(1-MeU-N3,O2,O4)
2
Ag
2
Pt]
n
Figure 4.21
Schematic representation of the linear chain of {[Ag(1-MeC)](NO
3
)}
n
as shown in Figure 4.20.
21
This complex represents one of the few examples of infi -
nite architecture based on nucleobases with two different metals.
The reaction of AgNO
3
with 1-methylcytosine (1-MeC) results in the polymeric
{[Ag(1 - MeC)](NO
3
)}
n
complex. This contains centrosymmetric dimers in which the
1-MeC ligands are bridged by two Ag(I) coordinated to O2 and N3 (Figure 4.21).
The nitrate ion is also coordinated to the silver ion. The dimeric units [Ag(1-
MeC)(NO
3
)]
2
form columns where the nucleobases are stacked. Based on this
structure, new models for the binding of Ag(I) to regions of high G-C content in
duplex DNA were proposed.
22
Another interesting example, obtained by Lippert using platinated nucleo-
bases as building blocks for supramolecular entities, is the product from the
reaction of
trans
- [(NH
3
)
2
Pt(9 - MeA -
N7
)(9 - MeHx -
N7
)](ClO
4
)
2
with AgNO
3
. This
yields a 1D helical coordination polymer
trans
- [{(NH
3
)
2
Pt(9 - MeA -
N7
)(9 - MeHx -
N7
)}Ag(NO
3
)(H
2
O)] (ClO
4
)(NO
3
) (Figure 4.22 ). The 9 - MeA coordinates through
the N1 and N3 positions to two Ag(I) centres. The backbone of the polymer is a
helical [Ag1 - N3a - C2a - N1a]
∞
chain. This complex was the fi rst example reported of
simultaneous binding of three metal ions to a neutral adenine, via N7 (Pt(II)), N1
(Ag(I)) and N3 (Ag(I)).
23
Coordination polymers containing Cu(II) have been reported for adenine and
guanine, respectively.
24
These compounds, prepared by reacting Cu(II) ions with
alkyldiamine-tethered adenine or guanine, were isolated as helical polymers. In both
