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π
-complexation of silver triflate. These
π
-complexed silver
−
platinum
−
−
1
−
1
squares showed large intensity decreases (15
) on
inclusion of nitrogen bases. Similarly, pronounced effects were
observed in the case of Pt
20 M
cm
−
Pd squares, too.
, acted as a chromatic
sensor that was sensitive to the micromolar concentrations of Ni
The rectangle
40
, reported by Stang
et al.
2+
,
2+
3+
−
Cd
, and Cr
[89]. A change in UV
vis spectra was observed when
a solution of rectangle
40
was treated with either Ni(NO
)
•6H
O,
3
2
2
−
Cd(NO
)
•6H
O, or Cr(NO
)
•4H
O up to a 1:1 host
guest ratio.
3
2
2
3
3
2
×
7
×
4
The binding constants were found to be 2.01
10
, 3.39
10
, and
3
−
1
2+
2+
3+
7.53
, respectively. The observed
equilibrium constants follow the same trend for the affinity as those
for free 1,10-phenanthroline with the same ions.
×
10
M
for Ni
, Cd
, and Cr
4+
PEt
3
PE
3
Pt
N
N
Pt
N
N
PEt
3
PEt
3
PEt
3
PEt
3
N
N
Pt
N
N
Pt
PEt
3
PEt
3
40
Lin and coworkers reported luminescent, Re(I)-based chiral
molecular square
[44] by incorporating a chiral ligand that was
able to interact with chiral amino alcohols, which resulted in chirality-
based quenching of their luminescence. For example, the Stern
3h
−
Volmer
luminescence quenching constants of
(R)-3h
, were found to be
K
=
sv
−
1
−
1
7.35 M
)-2-amino-
1-propanol, respectively, giving an enantioselectivity factor
and 6.02 M
for (
S
)-2-amino-1-propanol and (
R
−
K
(R
S)/
sv
K
R) of 1.22 for luminescence quenching (see Fig. 10.7), which
favors (S)-2-amino-1-propanol. Similarly, an opposite trend in the
enantioselectivity factor for luminescence quenching was observed
for
(R
−
sv
by the same guest molecules. Thus, the luminescence
quenching of chiral molecular square
(S)-3h
by 2-amino-1-propanol is
dependent on the absolute configuration of the square ligand as well
as the analytes. On the basis of these observations, it can be concluded
that the square ligand and analyte of opposite configuration constitute
the match pair for effective luminescence quenching. Moreover, the
magnitude of the enantioselectivity for square
3h
was significantly
higher than that of the ligand, suggesting a better defined chiral
environment was conferred by the square structure. Therefore, the
3h
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