Heat‐Induced Morphological Transformation of Supramolecular Nanostructures by Retro‐Diels–Alder Reaction

Controlling the morphology of supramolecular nanostructures in response to external stimuli is an important challenge in the development of functional soft materials. Here we show that a morphological transformation from 2D nanosheets to a network of 1D nanofibers is triggered by heating, which induces molecular conversion of a bolaamphiphile to a hydrogelator by means of a retro‐Diels–Alder reaction, thereby producing a new heat‐set supramolecular hydrogel. We anticipate that our design will be a starting point for more sophisticated supramolecular systems that integrate the thermodynamics of molecular assembly and the kinetics of chemical reactions to create complex supramolecular nanostructures.     

Construction of supramolecular helical nanofibers using renewable biomaterials: self-assembly of a cytidylic acid-appended bolaamphiphile in lemon juice

We performed the self-assembly of a 1,18-cytidylic acid-appended bolaamphiphile (C18C) in lemon juice, which contained citric acid, and succeeded in forming left-handed helical nanofibers with diameters, lengths, and pitches of ca. 6-7 nm, several hundred nm to 5 μm, and ca. 30-40 nm, respectively.     

Galvanomagnetic properties of air-stable and highly conductive potassium-intercalated graphite sheet

Magnetoresistance and Hall coefficient of air-stable potassium-intercalated graphite sheets (hereafter abbreviated as K-PGS) were determined at room temperature. The magnitude of the magnetoresistance and the absolute value of Hall coefficient of K-PGS decreased with increasing potassium content of K-PGS, n_K/n_C. Two-carrier model was used for calculating carrier density and mobility. The electron density increased with increasing n_K/n_C: 3.07×10²⁰ cm⁻³ (n_K/n_C=0.005), 5.67×10²⁰ cm⁻³ (n_K/n_C=0.008) and 6.40×10²⁰ cm⁻³ (n_K/n_C=0.011). The value of the electron density of K-PGS with n_K/n_C=0.011 (nominal composition KC₉₁) was about 80% of the reported value, 7.8×10²⁰ cm⁻³, for KC₄₈ (n_K/n_C=0.021) prepared from HOPG (highly oriented pyrolytic graphite). The mobility decreased with increasing n_K/n_C: 2.11×10³ cm² V⁻¹ s⁻¹ (n_K/n_C=0.005), 1.42×10³ cm² V⁻¹ s⁻¹ (n_K/n_C=0.008) and 1.34×10³ cm² V⁻¹ s⁻¹ (n_K/n_C=0.011). The value of the mobility of K-PGS with n_K/n_C=0.011 was about 60% of the reported value (2300 cm² V⁻¹ s⁻¹) for KC₄₈ prepared from HOPG.     

Electrochemical preparation of graphite intercalation compounds containing a cyclic amide, [CF2(CF2SO2)2N]

Graphite intercalation compounds (GICs) containing the cyclo-hexafluoropropane-1,3-bis(sulfonyl)amide anion, [CF₂(CF₂SO₂)₂N]⁻, are prepared for the first time. Stages 2 and 3 GICs are obtained by electrochemical oxidation of graphite in a nitromethane electrolyte. Gallery heights of 0.85-0.86 nm are determined by powder X-ray diffraction, and the intercalate anion orientation within the intercalate galleries is modeled using an energy minimized anion structure. GIC compositions are determined by thermogravimetric, fluorine and nitrogen analyses. The chemical preparation and bifluoride displacement reactions are compared with a GIC containing the linear bis(trifluoromethanesulfonyl)amide anion, [(CF₃SO₂)₂N]⁻.     

Solid-phase synthesis of benzazoles,quinazolines, and quinazolinones using an alkoxyamine linker

An alkoxyamine linker was applied for the solid-phase synthesis of benzazoles, quinazolines, and quinazolinones. Aromatic aldehydes were anchored by aldoxime linkage. After some reactions on a solid support, the products were cleaved with paraformaldehyde under the acidic conditions to afford the corresponding aldehydes, which were subsequently subjected to oxidative coupling with 2-substituted anilines under air atmosphere to give the desired compounds.     

Hexafluoro-, heptafluoro-, and octafluoro-salts, and [MnF5n+1] (n = 2, 3, 4) polyfluorometallates of singly charged metal cations, Li-Cs, Cu, Ag, In and Tl

The AMF₆, A₂MF₇, A₃MF₈, AM₂F₁₁, AM₃F_l6 and AM₄F₂₁ compounds (A = Li, Na, K, Rb, Cs, Cu, Ag, In, Tl; M = P, As, V, Rh, Ru, Au, Pt, Ir, Os, Re, Sb, Mo, W, Nb, Ta, Bi) are reviewed.Some of the structural data of the AMF₆ compounds are based just on powder diffraction work from the middle of the last century. The crystal structure types of AMF₆ compounds have been re-classified in this review, based mainly on single crystal data. The crystal structure types of AMF₆ compounds can be classified into six main groups: LiSbF₆ type, NaSbF₆ type, structures of cubic APF₆ and AAsF₆ with orientational disorder of the anions, tetragonal KSbF₆ (T) types and similar structures, AgSbF₆ type and similar structures, and KOsF₆ type.Reported crystal structures of A₂MF₇, A₃MF₈, AM₂F₁₁, AM₃F_l6 and AM₄F₂₁ compounds are limited. K₂MF₇ (M = Nb, Ta) crystallizes in the monoclinic and K₂WF₇ in the orthorhombic crystal system. Among the A₃MF₈ compounds the complete crystal structure has been determined only for Na₃TaF₈, which is monoclinic. The only known examples of crystal structures of AM₂F₁₁ compounds are ASb₂F₁₁ (A = Ag, K, Cs). Crystals of KSb₂F₁₁ are orthorhombic and isostructural to AgSb₂F₁₁, while CsSb₂F₁₁ is monoclinic. CsSb₃F₁₆ is the only example of a structurally characterized AM₃F_l6 compound. Its crystals are orthorhombic. For the rest of the known A₂MF₇, A₃MF₈, AM₂F₁₁, AM₃F_l6 and AM₄F₂₁ compounds, only lattice parameters are known.     

Tautomeric structure of dihydropyrazolo[1,5-a]-pyrimidin-7-one in a solution. A facile synthesis of novel 6-quinoxalinyldihydropyrazolo[1,5-a]pyrimidin-7-ones by ring transformation

6-Quinoxalinyldihydropyrazolo[1,5-a]pyrimidin-7-ones 4a-d were synthesized by the ring transformation of 3-(N,N-dimethylcarbamoyl)furo[2,3-b]quinoxaline hydrochloride 5 . Compounds 4a-d were found to exist as the 4,7-dihydro-7-oxo form E in dimethyl sulfoxide based on the nmr spectral data.