Yusuke Funasako

Crystal Structures and Phase‐Transition Dynamics of Cobaltocenium Salts with Bis(perfluoroalkylsulfonyl)amide Anions: Remarkable Odd–Even Effect of the Fluorocarbon Chains in the Anion

Crystal structures and thermal properties of cobaltocenium salts with bis(perfluoroalkylsulfonyl)amide (C(n)F2(n+1)SO2)2N anions [n = 0 (1), 1 (1 a), 2 (1 b), 3 (1 c), and 4 (1 d)] and the 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylamide anion (2) were investigated. In these solids, the cations are surrounded by four anions around their C5 axis, and stacking of these local structures forms two kinds of assembled structures. In the salts with even n (1, 1 b, and 1 d), the cation and anion are arranged alternately to form mixed-stack columns in the crystal. In contrast, in the salts with odd n (1 a and 1 c), the cations and anions independently form segregated-stack columns. An odd-even effect was also observed in the sum of the phase-change entropies from crystal to melt. All of the salts exhibited phase transitions in the solid state. The phase transitions to the lowest-temperature phase in 1, 1 a, and 2 are accompanied by order-disorder of the anions and symmetry lowering of the space group, which results in the formation of an ion pair. Solid-state (13)C NMR measurements on 1 a and 1 b revealed enhanced molecular motions of the cation in the higher-temperature phases.

Thermochromic Magnetic Ionic Liquids from Cationic Nickel(II) Complexes Exhibiting Intramolecular Coordination Equilibrium

Among the various thermochromic materials, liquid thermochromic materials are comparatively rare. To produce functional thermochromic liquids, we have designed ionic liquids based on cationic nickel complexes with ether side chains, [Ni(acac)(Me2 NC2 H4 NR1 R2 )]Tf2 N ([1]Tf2 N: R1 =C3 H6 OEt, R2 =Me; [2]Tf2 N: R1 =C3 H6 OMe, R2 =Me; [3]Tf2 N: R1 =R2 =C3 H6 OMe), where acac=acetylacetonate and Tf2 N=(F3 CSO2 )2 N- . The side chains (R1 , R2 ) can moderately coordinate to the metal center, enabling temperature-dependent coordination equilibria in the liquid state. [1]Tf2 N is a liquid at room temperature. [2]Tf2 N is obtained as a solid (Tm =352.7 K) but remains liquid at room temperature after melting. [3]Tf2 N is a solid with a high melting point (Tm =422.3 K). These salts display thermochromism in the liquid state, appearing red at high temperatures and orange, light-blue, or bluish-green at lower temperatures, and exhibiting concomitant changes in their magnetic properties. This phenomenon is based on temperature-dependent equilibrium between a square-planar diamagnetic species and a paramagnetic species with intramolecular ether coordination.

Crystal Structures and Phase Sequences of Metallocenium Salts with Fluorinated Anions: Effects of Molecular Size and Symmetry on Phase Transitions to Ionic Plastic Crystals

Sandwich compounds often exhibit various phase transitions, including those to plastic phases. To elucidate the general features of the phase transitions in metallocenium salts, the thermal properties and crystal structures of [Fe(C5 Me5 )2 ]X ([1]X), [Co(C5 Me5 )2 ]X ([2]X), and [Fe(C5 Me4 H)2 ]X ([3]X) have been investigated, where the counter anions (X) are Tf2 N (=(CF3 SO2 )2 N- ), OTf (=CF3 SO3- ), PF6 , and BF4 . The Tf2 N salts commonly undergo phase transitions from an ordered phase at low temperatures to an anion-disordered phase, followed by a plastic phase and finally melt at high temperatures. All these salts exhibit a phase transition to a plastic phase, and the transition temperature generally decreases with decreasing cation size and increasing anion size. The crystal structures of these salts comprise an alternating arrangement of cations and anions. About half of these salts exhibit phase transitions at low temperatures, which are mostly correlated with the order-disorder of the anion.

Valence engineering of ionic molecular crystals: monovalent–divalent phase diagram for biferrocene–tetracyanoquinodimethane salts

The valence state of ionic molecular solids composed of biferrocene derivatives (D) and tetracyanoquinodimethane (TCNQ) derivatives (A), either monovalent ([D]+[A2]−) or divalent ([D]2+[A2]2−), can be controlled by changing the redox potentials and molecular volumes of the components.

Thermoresponsive light scattering device utilizing surface behavior effects between polyimide and an ionic liquid-water mixture exhibiting lower critical solution temperature (LCST)-type phase separation

We proposed a thermoresponsive light scattering device that utilizes the surface behavior between polyimide and an ionic liquid-water mixture exhibiting lower critical solution temperature (LCST)-type phase separation. The LCST behavior for an ionic liquid device utilizing the polyimide with and without alkyl side chains was investigated. In the here-reported ionic liquid device that utilized the polyimide with alkyl side chains, [nBu4P][CF3COO] droplets were generated by phase separation—they were predominantly formed at the alkyl surface by a surface pinning effect. A stable transmittance in the opaque state could be obtained with this device. In contrast, an ionic liquid device using polyimide without alkyl side chains deteriorated transmittance in the opaque state because there was no surface pinning effect. Additionally, the viewing angle, contrast ratio, and heat cycle testing of this ionic liquid device with polyimide with alkyl side chains were also investigated. The results indicated that no parallax was obtained and that the ionic liquid device has a stable transmittance (verified by heat cycle testing). This unique device is expected to find use in the smart window applications that are activated by temperature changes.We proposed a thermoresponsive light scattering device that utilizes the surface behavior between polyimide and an ionic liquid-water mixture exhibiting lower critical solution temperature (LCST)-type phase separation. The LCST behavior for an ionic liquid device utilizing the polyimide with and without alkyl side chains was investigated. In the here-reported ionic liquid device that utilized the polyimide with alkyl side chains, [nBu4P][CF3COO] droplets were generated by phase separation—they were predominantly formed at the alkyl surface by a surface pinning effect. A stable transmittance in the opaque state could be obtained with this device. In contrast, an ionic liquid device using polyimide without alkyl side chains deteriorated transmittance in the opaque state because there was no surface pinning effect. Additionally, the viewing angle, contrast ratio, and heat cycle testing of this ionic liquid device with polyimide with alkyl side chains were also investigated. The results indicated that no para...