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>·BF₄ {<b>2</b>⁺ = [Cu­(Mepypm)­(dppp)]⁺, where Mepypm = 4-methyl-2-(2′-pyridyl)­pyrimidine and dppp = 1,3-bis­(diphenylphosphino)­propane} and previously reported <b>1</b>·BF₄, which possesses a bulky diphosphine ligand (<b>1</b>⁺ = [Cu­(Mepypm)­(DPEphos)]⁺, where DPEphos = bis­[2-(diphenylphosphino)­phenyl] ether). Two rotational isomers of <b>2</b>⁺ 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>·BF₄ in CDCl₃ (Δ<i>H</i> = 6 kJ mol^–1; Δ<i>S</i> = 25 J K^–1 mol^–1) were more positive than that tested under other conditions, such as in more polar solvents CD₂Cl₂, acetone-<i>d</i>₆, and CD₃CN. 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>⁺ with a bulky counterion, such as B­(C₆F₅)₄^–. 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>_{I<i>i→o</i>} = 10^–4 s^–1) but is active in the copper­(II) state (<i>k</i>_{II<i>i→o</i>} = 10^–1 s^–1) 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⁺), 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>·BF₄ {<b>2</b>⁺ = [Cu­(Mepypm)­(dppp)]⁺, where Mepypm = 4-methyl-2-(2′-pyridyl)­pyrimidine and dppp = 1,3-bis­(diphenylphosphino)­propane} and previously reported <b>1</b>·BF₄, which possesses a bulky diphosphine ligand (<b>1</b>⁺ = [Cu­(Mepypm)­(DPEphos)]⁺, where DPEphos = bis­[2-(diphenylphosphino)­phenyl] ether). Two rotational isomers of <b>2</b>⁺ 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>·BF₄ in CDCl₃ (Δ<i>H</i> = 6 kJ mol^–1; Δ<i>S</i> = 25 J K^–1 mol^–1) were more positive than that tested under other conditions, such as in more polar solvents CD₂Cl₂, acetone-<i>d</i>₆, and CD₃CN. 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>⁺ with a bulky counterion, such as B­(C₆F₅)₄^–. 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_Mes)]­BF₄ (<b>1</b>·BF₄, Mepypm = 4-methyl-2-(2′-pyridyl)­pyrimidine, L_Mes = 2,9-dimesityl-1,10-phenanthroline) was compared with previously reported complexes of [Cu­(MepmMepy)­(L_Mes)]­BF₄ (<b>2</b>·BF₄, MepmMepy = 4-methyl-2-(6′-methyl-2′-pyridyl)­pyrimidine), Cu­(Mepypm)­(DPEphos)]­BF₄ (<b>3</b>·BF₄, DPEphos = bis­[2-(diphenylphosphino)­phenyl]­ether), [Cu­(Mepypm)­(L_Anth)]­BF₄ (<b>4</b>·BF₄, L_Anth = 2,9-bis­(9-anthryl)-1,10-phenanthroline), and [Cu­(Mepypm)­(L_Macro)]­BF₄ (<b>5</b>·BF₄). 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_Mes)]­BF₄ (<b>1</b>·BF₄, Mepypm = 4-methyl-2-(2′-pyridyl)­pyrimidine, L_Mes = 2,9-dimesityl-1,10-phenanthroline) was compared with previously reported complexes of [Cu­(MepmMepy)­(L_Mes)]­BF₄ (<b>2</b>·BF₄, MepmMepy = 4-methyl-2-(6′-methyl-2′-pyridyl)­pyrimidine), Cu­(Mepypm)­(DPEphos)]­BF₄ (<b>3</b>·BF₄, DPEphos = bis­[2-(diphenylphosphino)­phenyl]­ether), [Cu­(Mepypm)­(L_Anth)]­BF₄ (<b>4</b>·BF₄, L_Anth = 2,9-bis­(9-anthryl)-1,10-phenanthroline), and [Cu­(Mepypm)­(L_Macro)]­BF₄ (<b>5</b>·BF₄). 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