Chemistry Reference
In-Depth Information
FIGURE10.3
(a) Amodel of amulticoordination equilibrium systembased on a four-layered
dendrimer. Definition of four independent equilibria enables calculations of the entire com-
plexation status for the given coordination constants. (b) Calculated profiles of the number of
metal complexations in each layer versus the added equivalent ratio of the metal ion for three
different situations. The assumed concentration of the dendrimer is 2
10
5
mol
1
L and the
number of coordination sites in each layer is 1, 2, 4, and 8. (See the color version of this figure in
Color Plates section.)
the midway (5M amounts) to the full complexation (Table 10.1). In contrast, the
coordination profiles were changed by downward trend in the coordination constants
(Case 2: K
a
¼
10
7
mol
1
L). At the initial point of the
addition, the distribution priority to the core-side layer is higher than that to the outer
layer, and then the prior coordination site is gradually moved to the outer layer. If 5M
amounts ofmetal ionwere added to the dendrimer, 89%(4.46/5) of the addedmetal ion is
distributed to the inner three layers. The behavior became striking when a larger change
in the constants is assumed (Case 3: K
a
¼
10K
b
¼
100K
c
¼
1000K
d
¼
10
10
mol
1
L). In
this case, the added metal ions clearly distinguished the sites to which they should
coordinate. During the initial stage (0
10
2
10
4
10
6
K
b
¼
K
c
¼
K
d
¼
<
[M]
0
/[dendrimer]
0
<
1), most of the metal ions
TABLE 10.1 Number of metals distributed to each layer of the dendrimers assumed in
Fig. 10.3 upon the quantitative addition of 5 molar amounts
Ligands
a
Layer
1
2
3
A
1 (1)
1.00
0.99
0.33
B
2 (2)
1.98
1.76
0.66
C
4 (2)
1.90
1.68
1.33
D
8 (0)
0.07
0.54
2.66
a
Values in the parentheses are the number of metals distributed to each layer if the ideal stepwise
coordination was occurred from the core side.
