Above Room Temperature Organic Ferroelectrics: Diprotonated 1,4-Diazabicyclo[2.2.2]octane Shifts between Two 2‑Chlorobenzoates

A pure organic single crystal, [H₂dabco]·[2CB]₂ ([H₂dabco]²⁺ = diprotonated 1,4-diaza­bicyclo­[2.2.2]­octane, 2CB^– = 2-chloro­benzoate), which undergoes a ferroelectric-to-paraelectric phase transition above room temperature (∼323 K upon heating), was prepared and characterized. This ferroelectric crystal possesses a distinctive supramolecular architecture composed of discrete H-bonded trimeric units (two 2CB^– anions bridged by one [H₂dabco]²⁺ cation through N–H···O hydrogen bond interactions). In the paraelectric phase, the [H₂dabco]²⁺ cation is rotationally disordered and lies at the symmetric center of the trimer. Upon cooling, it is frozen in an ordered state and deviates toward a 2CB^– anion at one end along the H-bond. The collective displacement of the cations leads to a polarization of the single crystal along the crystallographic <i>c</i> axis, which is confirmed by the temperature dependence of the second harmonic generation and spontaneous polarization. A significant increase in the phase transition temperature of the deuterated analogue suggests that the proton plays an important role in the ferroelectric phase transition

Field-Induced Slow Magnetic Relaxation in an Octacoordinated Fe(II) Complex with Pseudo‑<i>D</i>_2<i>d</i> Symmetry: Magnetic, HF-EPR, and Theoretical Investigations

An octacoordinated Fe­(II) complex, [Fe^II(dpphen)₂]­(BF₄)₂·1.3H₂O (<b>1</b>; dpphen = 2,9-bis­(pyrazol-1-yl)-1,10-phenanthroline), with a pseudo-<i>D</i>_2<i>d</i>-symmetric metal center has been synthesized. Magnetic, high-frequency/-field electron paramagnetic resonance (HF-EPR), and theoretical investigations reveal that <b>1</b> is characterized by uniaxial magnetic anisotropy with a negative axial zero-field splitting (ZFS) (<i>D</i> ≈ −6.0 cm^–1) and a very small rhombic ZFS (<i>E</i> ≈ 0.04 cm^–1). Under applied dc magnetic fields, complex <b>1</b> exhibits slow magnetic relaxation at low temperature. Fitting the relaxation time with the Arrhenius mode combining Orbach and tunneling terms affords a good fit to all the data and yields an effective energy barrier (17.0 cm^–1) close to the energy gap between the ground state and the first excited state. The origin of the strong uniaxial magnetic anisotropy for <b>1</b> has been clearly understood from theoretical calculations. Our study suggests that high-coordinated compounds featuring a <i>D</i>_2<i>d</i>-symmetric metal center are promising candidates for mononuclear single-molecule magnets

Ruthenium Ion-Catalyzed Oxidation of Shenfu Coal and Its Residues

Shenfu coal (SFC), its liquefaction residue (R_L), and carbon disulfide (CS₂)/tetrahydrofuran (THF)-inextractable matter (R_E) were subject to ruthenium ion-catalyzed oxidation to understand the differences in structural features among the above three samples. The results suggest that SFC is rich in long-chain arylalkanes and α,ω-diarylalkanes (DAAs) with carbon number of methylene linkage from 2 to 4 and that long-chain arylalkanes and DAAs are reactive toward hydroliquefaction and soluble in a CS₂/THF mixed solvent, whereas highly condensed aromatic species in SFC show poor solubility in the CS₂/THF mixed solvent

Ruthenium Ion-Catalyzed Oxidation of Shenfu Coal and Its Residues

Shenfu coal (SFC), its liquefaction residue (R_L), and carbon disulfide (CS₂)/tetrahydrofuran (THF)-inextractable matter (R_E) were subject to ruthenium ion-catalyzed oxidation to understand the differences in structural features among the above three samples. The results suggest that SFC is rich in long-chain arylalkanes and α,ω-diarylalkanes (DAAs) with carbon number of methylene linkage from 2 to 4 and that long-chain arylalkanes and DAAs are reactive toward hydroliquefaction and soluble in a CS₂/THF mixed solvent, whereas highly condensed aromatic species in SFC show poor solubility in the CS₂/THF mixed solvent