Chemistry Reference
In-Depth Information
FIGURE 6.2
Dendritic receptors
4
-
7
with a CTV core and guest
C
61
(CO
2
Et)
2
.
dendritic CTV derivatives, Job's plot provided good evidence for 1:1 complex
formation in solution. The formation of host-guest complexes in CH
2
Cl
2
or C
6
H
6
solutions betweenmethanofullerene
C
61
(CO
2
Et)
2
(Figure 6.2) and the dendritic CTV
derivatives was also investigated. The association constant values, determined by
standard UV-vis titrations, are summarized in Table 6.1.
Interestingly, in both solvents and for both substrates, the K
a
values are signif-
icantly increased as the generation number of the dendritic substituents is increased.
Therefore, the surrounding dendritic branches appear to be able to increase the
TABLE 6.1 Association Constants K
a
(M
1
) from UV-vis Binding Titrations for 1:1
Complexes of C
60
and C
61
(CO
2
Et)
2
to 4-7 in CH
2
Cl
2
and C
6
H
6
at 298K
a
C
60
C
61
(CO
2
Et)
2
CH
2
Cl
2
C
6
H
6
CH
2
Cl
2
C
6
H
6
%
b
%
b
4
85
20
90
30
5
120
20
115
15
130
20
110
30
6
200
10
190
20
190
20
180
20
7
340
20
345
20
300
30
290
30
a
The association constants K
a
have been determined bymonitoring the variations of absorbance at different
wavelengths in the 430-445 nm region where the strongest spectral changes are observed. Identical results
within the error range in duplicate and triplicate runs were obtained, and average values are reported.
b
Not determined due to the poor solubility of
4
in C
6
H
6
.
