Chemistry Reference
In-Depth Information
(a)
OMe
-0.551 mT
(-0.508 mT)
2-
H
·2K
+
O
O
2-
O
O
H
±0.025 mT
-0.434 mT
(-0.478 mT)
1x10
-3
M in diglyme
290 K
(b)
2-
O
O
9.6455240 GHz
g
=2.0037
342.6
343.2
343.8
344.4
345.0
Magnetic field/mT
Figure3.40
(a)Chemicalstructuresandspindensitydistributionsoftheradicaldianionsof
MP3OPO,TB4OPO
,
and
TB6OPO
(potassium salt) with observed and calculated (in parentheses) hfccs of
1
Hand
39
K
+
.(b)EPR
spectrum of the potassium salt of
TB6OPO
radical dianion in a diglyme (bis(2-methoxyethyl) ether) solution.
(bReprintedwithpermissionfrom[37a].Copyright2002AmericanChemicalSociety.)
The observed hfccs include couplings attributable to
39
Kand
23
Na nuclear spins (counter cations),
indicative of tight-ion-pairing structures. DFT calculations suggest extremely delocalized natures of
the two anion charges over the
OPO
skeleton likely to the neutral radical systems, probably leading
to their high stabilities (
vide infra
).
36,37a,38
As expected by their dramatic change of electronic
structures, color changes also occurred depending on the redox states, meaning that the
OPO
system is
electrochromic.
3.8.5 Molecular crystalline secondary battery
Reversible redox processes in a solution can be compared to charge/discharge processes of an electrode
active material in a secondary battery. An organic molecule with multistage redox ability can, therefore,
accommodate a large number of electrons in the molecular skeleton. Thus, there is a unique possibility
to realize a large discharge capacity in the secondary battery system by utilizing such organic molecules
as electrode active materials. In 2002, this idea of a secondary battery utilizing phenalenyl and
OPO
derivatives was independently claimed by different authors.
26,37a,38
Then, the novel secondary battery
based on
TB6OPO
as a cathode active material was developed and termed “molecular crystalline sec-
ondary battery” (Figure 3.41a,b).
50
Importantly, this secondary battery shows a step-wise charge/discharge
behavior and a comparable performance in discharge capacity (182 Ah/kg) to commercially available
lithium ion secondary batteries (150
∼
170 Ah/kg) (Figure 3.41c). This step-wise process and discharge
Search WWH ::
Custom Search