9 research outputs found
Solvated-Ion-Pairing-Sensitive Molecular Bistability Based on Copper(I)-Coordinated Pyrimidine Ring Rotation
We describe herein the effect of solvated ion pairing
on the molecular
motion of a pyrimidine ring coordinated on a copper center. We synthesized
a series of heteroleptic copper(I) complex salts bearing an unsymmetrically
substituted pyridylpyrimidine and a bulky diphosphine. Two rotational
isomers of the complexes were found to coexist and interconvert in
solution via intramolecular ligating atom exchange of the pyrimidine
ring, where the notation of the inner (i-) and outer (o-) isomers
describes the orientation of the pyrimidine ring relative to the copper
center. The stability of the pyrimidine orientation was solvent- and
counterion-sensitive in both <b>2</b>·BF<sub>4</sub> {<b>2</b><sup>+</sup> = [Cu(Mepypm)(dppp)]<sup>+</sup>, where Mepypm
= 4-methyl-2-(2′-pyridyl)pyrimidine and dppp = 1,3-bis(diphenylphosphino)propane}
and previously reported <b>1</b>·BF<sub>4</sub>, which
possesses a bulky diphosphine ligand (<b>1</b><sup>+</sup> =
[Cu(Mepypm)(DPEphos)]<sup>+</sup>, where DPEphos = bis[2-(diphenylphosphino)phenyl]
ether). Two rotational isomers of <b>2</b><sup>+</sup> were
separately obtained as single crystals, and the structure of each
isomer was examined in detail. Both the enthalpy and entropy values
for the rotation of <b>2</b>·BF<sub>4</sub> in CDCl<sub>3</sub> (Δ<i>H</i> = 6 kJ mol<sup>–1</sup>; Δ<i>S</i> = 25 J K<sup>–1</sup> mol<sup>–1</sup>) were more positive than that tested under other
conditions, such as in more polar solvents CD<sub>2</sub>Cl<sub>2</sub>, acetone-<i>d</i><sub>6</sub>, and CD<sub>3</sub>CN. The
reduced contact of the anion to the cation in a polar solvent seems
to contribute to the enthalpy, entropy, and Gibbs free energy for
rotational isomerization. This speculation based on solvated ion pairing
was further confirmed by considering the rotational behavior of <b>2</b><sup>+</sup> with a bulky counterion, such as B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub><sup>–</sup>. The findings are valuable
for the design of molecular mechanical units that can be readily tuned
via weak electrostatic interactions
Reversible Copper(II)/(I) Electrochemical Potential Switching Driven by Visible Light-Induced Coordinated Ring Rotation
We here describe the first metal complex system in which
electronic
signals can be repeatedly extracted by converting bistable states
related to an intramolecular ligand rotational motion, which is fueled
by visible light. The molecular structure for relating an electron
transfer and a motion consists of a copper center and a coordinated
unsymmetrically substituted pyrimidine derivative, whose rotational
isomerization causes an electrochemical potential shift. To harness
light energy effectively through metal-to-ligand charge transfer (MLCT)
excitation, we prepared a simple copper(I) complex coordinated by
a 4-methyl-2-(6′-methyl-2′-pyridyl)pyrimidine and a
bulky diimine. The thermodynamic and kinetic parameters of redox and
rotational reactions were analyzed by cyclic voltammograms at variable
temperatures, by considering four stable isomers related to copper(II)/(I)
states and rotational isomeric states. The key feature of this compound
is that the rotation is frozen in the copper(I) state (rate constant
for the rotation, <i>k</i><sub>I<i>i→o</i></sub> = 10<sup>–4</sup> s<sup>–1</sup>) but is active
in the copper(II) state (<i>k</i><sub>II<i>i→o</i></sub> = 10<sup>–1</sup> s<sup>–1</sup>) at 203 K.
The compound makes a bypass route to the isomeric metastable copper(I)
state, via a tentative copper(II) state formed by photoelectron transfer
(PET) in the presence of a redox mediator, decamethylferrocenium ion
(DMFc<sup>+</sup>), or upon a partial oxidation of the complex. Light-
and heat-driven rotation in the copper(I) state with a potential shift
(Δ<i>E</i>°′ = 0.14 V) was analyzed by
electrochemical measurements of the complex in the solution state.
The rotor could be reset to the initial state by heating, thereby
completing the cycle and enabling repeated operation fueled by light
energy. A significant redox potential shift associated with the copper(II)/(I)
transition accompanied the rotation, thereby providing a new type
of molecular signaling system
Solvated-Ion-Pairing-Sensitive Molecular Bistability Based on Copper(I)-Coordinated Pyrimidine Ring Rotation
We describe herein the effect of solvated ion pairing
on the molecular
motion of a pyrimidine ring coordinated on a copper center. We synthesized
a series of heteroleptic copper(I) complex salts bearing an unsymmetrically
substituted pyridylpyrimidine and a bulky diphosphine. Two rotational
isomers of the complexes were found to coexist and interconvert in
solution via intramolecular ligating atom exchange of the pyrimidine
ring, where the notation of the inner (i-) and outer (o-) isomers
describes the orientation of the pyrimidine ring relative to the copper
center. The stability of the pyrimidine orientation was solvent- and
counterion-sensitive in both <b>2</b>·BF<sub>4</sub> {<b>2</b><sup>+</sup> = [Cu(Mepypm)(dppp)]<sup>+</sup>, where Mepypm
= 4-methyl-2-(2′-pyridyl)pyrimidine and dppp = 1,3-bis(diphenylphosphino)propane}
and previously reported <b>1</b>·BF<sub>4</sub>, which
possesses a bulky diphosphine ligand (<b>1</b><sup>+</sup> =
[Cu(Mepypm)(DPEphos)]<sup>+</sup>, where DPEphos = bis[2-(diphenylphosphino)phenyl]
ether). Two rotational isomers of <b>2</b><sup>+</sup> were
separately obtained as single crystals, and the structure of each
isomer was examined in detail. Both the enthalpy and entropy values
for the rotation of <b>2</b>·BF<sub>4</sub> in CDCl<sub>3</sub> (Δ<i>H</i> = 6 kJ mol<sup>–1</sup>; Δ<i>S</i> = 25 J K<sup>–1</sup> mol<sup>–1</sup>) were more positive than that tested under other
conditions, such as in more polar solvents CD<sub>2</sub>Cl<sub>2</sub>, acetone-<i>d</i><sub>6</sub>, and CD<sub>3</sub>CN. The
reduced contact of the anion to the cation in a polar solvent seems
to contribute to the enthalpy, entropy, and Gibbs free energy for
rotational isomerization. This speculation based on solvated ion pairing
was further confirmed by considering the rotational behavior of <b>2</b><sup>+</sup> with a bulky counterion, such as B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub><sup>–</sup>. The findings are valuable
for the design of molecular mechanical units that can be readily tuned
via weak electrostatic interactions
Structural Modification on Copper(I)-pyridylpyrimidine Complexes for Modulation of Rotational Dynamics, Redox Properties, and Phototriggered Isomerization
The
redox properties of copper pyridylpyrimidine complexes, which undergo
linkage isomerism based on pyrimidine ring rotation, were compared
under different coordination environments. A newly synthesized compound,
[Cu(Mepypm)(L<sub>Mes</sub>)]BF<sub>4</sub> (<b>1</b>·BF<sub>4</sub>, Mepypm = 4-methyl-2-(2′-pyridyl)pyrimidine, L<sub>Mes</sub> = 2,9-dimesityl-1,10-phenanthroline) was compared with
previously reported complexes of [Cu(MepmMepy)(L<sub>Mes</sub>)]BF<sub>4</sub> (<b>2</b>·BF<sub>4</sub>, MepmMepy = 4-methyl-2-(6′-methyl-2′-pyridyl)pyrimidine),
Cu(Mepypm)(DPEphos)]BF<sub>4</sub> (<b>3</b>·BF<sub>4</sub>, DPEphos = bis[2-(diphenylphosphino)phenyl]ether), [Cu(Mepypm)(L<sub>Anth</sub>)]BF<sub>4</sub> (<b>4</b>·BF<sub>4</sub>, L<sub>Anth</sub> = 2,9-bis(9-anthryl)-1,10-phenanthroline), and [Cu(Mepypm)(L<sub>Macro</sub>)]BF<sub>4</sub> (<b>5</b>·BF<sub>4</sub>).
Isomer ratios, isomerization dynamics, redox properties, and photoelectron
conversion functions varied with the coordination structure. Methyl
substituents on the 6-position of the pyridine moiety increased steric
repulsion and contributed to quicker rotation, enhanced photoluminescence,
and increased photodriven rotational isomerization
Structural Modification on Copper(I)-pyridylpyrimidine Complexes for Modulation of Rotational Dynamics, Redox Properties, and Phototriggered Isomerization
The
redox properties of copper pyridylpyrimidine complexes, which undergo
linkage isomerism based on pyrimidine ring rotation, were compared
under different coordination environments. A newly synthesized compound,
[Cu(Mepypm)(L<sub>Mes</sub>)]BF<sub>4</sub> (<b>1</b>·BF<sub>4</sub>, Mepypm = 4-methyl-2-(2′-pyridyl)pyrimidine, L<sub>Mes</sub> = 2,9-dimesityl-1,10-phenanthroline) was compared with
previously reported complexes of [Cu(MepmMepy)(L<sub>Mes</sub>)]BF<sub>4</sub> (<b>2</b>·BF<sub>4</sub>, MepmMepy = 4-methyl-2-(6′-methyl-2′-pyridyl)pyrimidine),
Cu(Mepypm)(DPEphos)]BF<sub>4</sub> (<b>3</b>·BF<sub>4</sub>, DPEphos = bis[2-(diphenylphosphino)phenyl]ether), [Cu(Mepypm)(L<sub>Anth</sub>)]BF<sub>4</sub> (<b>4</b>·BF<sub>4</sub>, L<sub>Anth</sub> = 2,9-bis(9-anthryl)-1,10-phenanthroline), and [Cu(Mepypm)(L<sub>Macro</sub>)]BF<sub>4</sub> (<b>5</b>·BF<sub>4</sub>).
Isomer ratios, isomerization dynamics, redox properties, and photoelectron
conversion functions varied with the coordination structure. Methyl
substituents on the 6-position of the pyridine moiety increased steric
repulsion and contributed to quicker rotation, enhanced photoluminescence,
and increased photodriven rotational isomerization
真空プロセスで作製したリチウム金属負極を用いたバルク型全固体電池の作製と評価
identifier:oai:t2r2.star.titech.ac.jp:5068677
メカノケミカル法による複合化NCM活物質の全固体電池特性
identifier:oai:t2r2.star.titech.ac.jp:5068675