Biology Reference
In-Depth Information
10.7
Electrochemical Sensing by Metallacyclic
Supramolecules
In addition to Lewis acid/base and luminescence properties, the
electrochemical behavior of a metallacyclic supramolecular host
can be influenced by the guest encapsulation. Beer
reported
dinuclear copper(II) metallacyclic supramolecules, which showed
quasi-reversible oxidation potentials [92]. They found that the
interaction of metallacycles with various anions showed cathodic
shifts in the oxidation potential on host
et al.
−
guest complex formation.
In the case of the larger metallacycle
significant cathodic
shifts were observed in the presence of tetrahedral anions such
as dihydrogenphosphate and perrhenate (
50
∼
85 mV), while the
smaller anions such as chloride, bromide, or nitrate did not yield a
noticeable effect. In contrast, the smaller metallacycle
showed
substantial cathodic shifts in the presence of smaller anions such as
chloride (20 mV), with little or no response to the larger anions. The
aforementioned observations indicate that these metallacycles are
size-selective anion sensors.
51
N
n
Bu
N
n
Bu
N
n
Bu
N
n
Bu
S
S
S
S
S
S
S
S
Cu
Cu
Cu
Cu
S
S
S
S
S
S
S
S
N
n
Bu
N
n
Bu
N
n
Bu
N
n
Bu
50
51
Li and coworkers reported a fairly large but uncommon cathodic
potential shift (
∼
380 mV) in oxidation potential for octanuclear
metallacycle (Ni
Fc
)
52
(structure adopted from Ref. [59]) on
4
4
2+
encapsulation of the Mg
cation in the solution as well as in the
solid state [93]. The stepwise addition of up to 2 eq. of Mg(NO
)
3
2
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