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the sample such as small cracks generated in the crystal. These cracks limit the
current pass in the crystal to reduce the effective cross-sectional area of the crystal.
Compared with the
s
RT
at stage 1 and 3,
s
RT
at each stages were comparable in
the case of the complexes (B
2+
NC
3
N
2+
, Me-NC
3
N
2+
, Cl-NC
3
N
2+
), whereas
they decreased to 0.008, 0.14 and 0.007 times larger than those of stage 1 in the case
of the complexes (B
2+
¼
¼ cis
-NC
4
N
2+
,
trans
-NC
4
N
2+
,NC
5
N
2+
, respectively). Since
the crystal structure recovered perfectly in K
2
(
cis
-NC
4
N)[Pt
2
(pop)
4
I]
4H
2
O and
K
2
(
trans
-NC
4
N)[Pt
2
(pop)
4
I]
4H
2
O, this decrease may also be due to the partial
degradation of the sample. The slight rehydration of K
2
(NC
5
N)[Pt
2
(pop)
4
I] also
reduced the quality of the crystal.
Hence, we can summarize that the robustness of the MMX chains with binary
countercations decreases in the following order of B
2+
:NC
3
N
2+
, Me-NC
3
N
2+
,
Cl-NC
3
N
2+
NC
2
OC
2
N
2+
. This order
indicates that the complex with longer B
2+
has weaker framework. In the case of
the complexes (B
2+
> trans
-NC
4
N
2+
> cis
-NC
4
N
2+
NC
5
N
2+
>
>
NC
3
N
2+
, Me-NC
3
N
2+
, Cl-NC
3
N
2+
), B
2+
are in well-ordered
zigzag conformation, while in the case of the complexes (B
2+
¼
¼ cis
-NC
4
N
2+
,
trans
-
NC
4
N
2+
,NC
5
N
2+
,NC
2
OC
2
N
2+
), longer B
2+
are disordered and/or in less stable
bending conformation due to the limitation of the region, as mentioned above
(Fig.
10.2
.). These differences in stability of B
2+
are assumed to induce the different
robustness of the complexes.
10.4 Conclusion
In this study, the development of new electronic state of MMX chains by
introducing binary countercations, the control of the electronic states, and the
conductance of MMX chains by dehydration-rehydration were carried out.
Single-crystal X-ray structure analysis indicates that MMX chains in binary
system, A
2
B[Pt
2
(pop)
4
I]
K
+
,Rb
+
;B
n
H
2
O(A
¼
¼
alkyldiammonium;
n ¼
2
or 4) have rare “synchronized” packing induced by the hydrogen bond and coordi-
nation bond networks among the chains and short Pt-I-Pt distance. These features
play an important role in water-vapor-induced changes and high conductivity of the
complexes. Various analyses indicated that the electronic state is novel ACP + CDW
state when MMX chains contain shorter alkyldiammonium ion (B
2+
NC
3
N
2+
,
Me-NC
3
N
2+
Cl-NC
3
N
2+
) but is general CDW state in other cases. The twisting of
pop ligands caused by steric hindrance around A
+
¼
is the origin of the ACP-like
distortion in ACP + CDW state.
Water-vapor-induced switching of MMX chains is the other focus of this
chapter.
4H
2
O showed
vapochromism with the switching of the electronic states from CP to CDW
state by the dehydration. MMX chains with binary countercations also showed
water-vapor-induced switching. The single-crystal X-ray structure analysis of
K
2
(NC
3
N)[Pt
2
(pop)
4
I] provided us the important information about the electronic
state in the dehydrated state. K
2
(NC
3
N)[Pt
2
(pop)
4
I]
(NC
4
N)
2
[Pt
2
(pop)
4
I]
4H
2
O and
(NC
5
N)
2
[Pt
2
(pop)
4
I]
4H
2
O is the first MMX
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