Tomoyuki Mochida

Ionic Liquids of Cationic Sandwich Complexes

Simple cationic sandwich complexes that contained alkyl- or halogen substituents provided ionic liquids (ILs) with the bis(perfluoroalkanesulfonyl)imide anion. Ferrocenium- and cobaltocenium ILs [M(C(5)H(4)R(1))(C(5)H(4)R(2))][Tf(2)N] (M=Fe, Co) and arene-ferrocenium ILs [Fe(C(5)H(4)R(1))(C(6)H(5)R(2))][Tf(2)N] were prepared and their physical properties were investigated. A detailed comparison of their thermal properties revealed the effects of molecular symmetry and substituents on their melting points. Their viscosity increased on increasing the length of the substituent on the cation and the perfluoroalkyl chain length on the anion. Upon cooling, ILs with low viscosities exhibited crystallization, whereas those with higher viscosities tended to exhibit glass transitions. Most of these salts showed phase transitions in the solid state. A magnetic-switching phenomenon was observed for the paramagnetic ferrocenium IL, which was associated with a liquid/solid transformation, based on the magnetic anisotropy of the ferrocenium cation. (57)Fe Mössbauer spectroscopy was applied to [Fe(C(5)H(4)nBu)(2)][Tf(2)N] to investigate the vibrational behavior of the iron atom in the crystal and glassy states of the ferrocenium IL.

Preparation, Properties, and Crystal Structures of Organometallic Ionic Liquids Comprising 1-Ferrocenyl-3-alkylimidazolium-Based Salts of Bis(trifluoromethanesulfonyl)amide and Hexafluorophosphate

Bis(trifluoromethanesulfonyl)amide (TFSA), hexafluorophosphate (PF(6)(-)), and iodide salts of 1-ferrocenyl-3-alkylimidazolium were prepared and their thermal and physical properties, including the dependence on alkyl chain length (methyl-hexadecyl), were investigated. The TFSA salts were highly viscous ionic liquids with melting points around room temperature. 1-Ferrocenyl-4-methyltriazolium salts were also prepared for comparison. The ferrocenylimidazolium and ferrocenyltriazolium cations showed redox waves for both the ferrocenyl moiety and the azolium moiety and exhibited corresponding charge-transfer bands at around 330 nm, which were analyzed using the Marcus-Hush model. Crystal structure determinations at low temperature revealed that the PF(6) and iodide salts form layerlike structures composed of ionic layers of the charged moieties. The TFSA salt exhibited short hydrogen-bond-like intermolecular contacts between the hydrogen atoms of the cation and oxygen atoms of the anion.

Synergistic Spin Transition between Spin Crossover and Spin-Peierls-like Singlet Formation in the Halogen-Bonded Molecular Hybrid System: [Fe(Iqsal)2][Ni(dmit)2]⋅CH3CN⋅H2O†

To introduce halogen-bond interactions between a cation and an anion, a novel Fe(III) complex from iodine-substituted ligands involving a paramagnetic nickel dithiolene anion was prepared and characterized. The compound exhibited the synergy between a spin-crossover transition and a spin-Peierls-like singlet formation. The halogen-bond interactions between the iodine and the sulfur atoms stabilized the paramagnetic state of π-spins and played a crucial role in the synergistic magnetic transition between d- and π-spins. In addition, the compound showed the light-induced excited spin state trapping effect.

Organic hydrogen‐bonded dielectrics: Quantum paraelectricity based on tautomerization of 9‐hydroxyphenalenone derivatives

Dielectric properties based on tautomerization in 9‐hydroxyphenalenone derivatives were examined. While the 5‐methyl derivative 2 exhibits an antiferroelectric transition at 41 K, such a phase transition was not observed in 5‐bromo derivative 3 down to 4.2 K. Suppression of the phase transition in the latter may be interpreted in terms of quantum paraelectricity based on proton‐tunneling along the hydrogen bond. The reason for the appearance of antiferroelectric ordering coupled with the phase transition in 2 may be ascribed to reduction of the tunneling frequency due to symmetry breaking caused by the methyl group. The present system can be regarded as zero‐dimensional hydrogen‐bonded system and is interesting in reference to inorganic hydrogen‐bonded dielectrics.

Calorimetric study of proton tunneling in solid 5-bromo-9- hydroxyphenalenone and deuteration-induced phase transitions in its deuteroxy analog

The heat capacities of 5-bromo-9-hydroxyphenalenone (BHP) and its deuteroxy derivative (BDP) were measured at temperatures between 2 and 310 K. The heat capacity of BHP is a smooth function of temperature and that of BDP has two peaks at 21.3 and 33.9 K. By analyzing the data on BHP, a tunnel splitting of (64±2) cm−1 associated with the quantum mechanical motion of the hydrogen atom in the intramolecular O–H–O hydrogen bond was derived along with the Debye temperature 60.8 K and two Einstein temperatures 131.4 (nondegenerate) and 210.4 K (doubly degenerate). The enthalpy change of 225 J mol−1 and entropy change of 6.8 J K−1 mol−1 were determined for the total thermal effects associated with the two phase transitions in BDP. The value of the transition entropy is consistent with the twofold disorder in the high temperature phase. The tunneling energy and transition enthalpy satisfy an inequality demanded, on the assumption that the potential energies experienced by the proton and deuteron are the same, by ...

Supramolecular assembly of ferrocenes via hydrogen bonds: dimensional variation in ferrocenylpyrimidine complexes with carboxylic acids and aromatic alcohols

Co-crystallization of 5-ferrocenylpyrimidine (FcPM) with various carboxylic acids and aromatic alcohols produces hydrogen-bonded supramolecular architectures. Thus, reaction of FcPM with compounds containing two hydrogen-bonding sites gives 2:1 co-crystals with discrete structures of the type [(FcPM)2·D] [where D = succinic acid (1), hydroquinone (2), resorcinol (3) and 2,2′-thiodiglycolic acid (4)]. A complex with a chiral chain structure, [FcPM·{(R)-(+)-1,1′-bi-2-naphthol}]n (5), is obtained by the combination of FcPM with (R)-(+)-1,1′-bi-2-naphthol. The binaphthol molecules form hydrogen-bonded helical chains, which carry ferrocene units as pendants. The combination of FcPM with trimesic acid and pyromellitic acid produces supramolecular complexes with tape structures, [FcPM·(trimesic acid)]n (6) and [FcPM2·(pyromellitic acid)]n (7), respectively. The tape structure of 6 consists of repeating units of large hexagonal rings while that of 7 consists of rhomboidal rings. Combination of FcPM with phloroglucinol produces a layered structure complex, [FcPM·(phloroglucinol)·2H2O]n (8), exhibiting three-dimensional hydrogen bonding. In this complex, FcPM molecules link hydrogen-bonded sheets composed of phloroglucinol and water molecules. The dimensionality of the assembled structures is influenced by the number of hydrogen-bonding substituents on the donor molecules.

Electronic states and anti-ferromagnetic order in mixed-stack charge-transfer compound (BEDT-TTF)(F2TCNQ)

Abstract Crystal structure, optical and magnetic properties are reported for a unique class of donor-acceptor charge-transfer (CT) complex (BEDT-TTF)(F 2 TCNQ). Charge-transfer from the donor to the acceptor is complete, forming an ionic mixed-stack CT crystal. “Side-by-side” interaction between BEDT-TTF molecules results in a one-dimensional (1D) correlated electronic system that is perpendicular to the donor-acceptor mixed-stack column. Consequently, F 2 TCNQ radical spins are strongly isolated from neighboring molecules, showing Curie-like behavior in magnetic susceptibility, followed by an anti-ferromagnetic order at around T N = 30 K.

Intermolecular Methoxycarbonylation of Terminal Alkynes Catalyzed by Palladium(II) Bis(oxazoline) Complexes

Boxing clever: Direct conversion of a terminal alkyne group into a beta-methoxyacrylate is realized with the aid of the bis(oxazoline) ligand (box). Acetyl and ketal protecting groups, free hydroxy groups, and acid-sensitive glycosidic bonds are not affected under the reaction conditions. The one-pot synthesis of (+/-)-dihydrokawain from the homopropargyl alcohol is also achieved. tfa = trifluoroacetate.

Transformation between monovalent and divalent ionic solids : An ionic(I)-ionic(II) phase transition in a biferrocene-F1TCNQ charge-transfer complex

An “ionic(I)–ionic(II)” charge-transfer transition has been observed in a new molecular solid composed of dineopentylbiferrocene (D) and fluorotetracyanoquinodimethane (A). The material is a monova...

Low-frequency spectra of metallocenium ionic liquids studied by terahertz time-domain spectroscopy

Terahertz (THz) time-domain spectroscopic measurements have been done on five novel metallocenium ionic liquids based on the electro-optic sampling method. The study covered the spectral range from 10 to 85 cm(-1). The complex dielectric spectra were broad and dispersive in nature, and the imaginary part of the dielectric constant consisting of part of the dielectric constant was simulated with different combinations of model functions to unravel the intermolecular dynamics. We compared our results with the previous results on the other ionic liquid. It was revealed that the librational motion of the cations as well as the interion vibration between the cations and the anions are responsible for observed dynamics in THz region. No intramolecular vibrational mode has been found in the low-frequency region.