Biomedical Engineering Reference
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a
b
0.7
0.8 0.9
1.0
1.1
0.7
0.9
1.1
VM
VM
Fig. 10 CVs of (a) a 2.0 mM 9 solution in 0.10 M Bu
4
NPF
6
/MeCN; (b) 9 + four times excess of
Zn
2+
. Potential scan rate of 100 mV/s
K
N
L2 · Cd (NO
3
)
2
R
N
n
O
N
10
R=Me,n=1
11
R=H,n=1
12
R=Me,n=2
N
O
n
N
+
R
K
N
L6 · Zn (NO
3
)
2
L6 · Cd (NO
3
)
2
Scheme 3 Possible complex formed by ligands 10-12
in energetic terms to be accompanied by amidic hydrogen removal. For this very
reason, when no base is present in the medium, it interacts with Zn
2+
in the same
way as ligand 10 does, resulting in 80% quenching. When an excess of base
(tetrabutylammonium hydroxide) is added, amidic hydrogen is removed and, in
this situation, Zn
2+
is chelated by both nitrogens of the same branch (Fig.
11b
). This
disposition does not constrain the torsion angle between the aromatic biphenyl rings
and quenching is not induced.
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