Rotational sublevels of an ortho-hydrogen molecule encapsulated in an isotropic C60 cage.

From specific heat measurements in high quality H2@C60 samples performed over a broad temperature range, we obtain the smallest yet observed splitting of rotational energy sublevels of encapsulated single H2 molecules, 0.1-0.2 meV, in the nearly spherical potential well provided by highly isotropic C60 cages. Additionally, we find evidence of the quantized oscillation state of isolated H2 in the C60 cage. The minuscule splitting indicates that H2@C60 provides unprecedented opportunities to study free-molecule quantum dynamic properties.

High temperature end of the so-called "Koga line": anomalies in temperature derivatives of heat capacities.

The so-called "Koga line" is a collection of the loci of anomalies in various third derivatives of the Gibbs function, G, in the temperature-mole fraction field for aqueous solutions of nonelectrolytes. This splits the H(2)O-rich region into two, in each of which the molecular organization and interactions we call it mixing scheme is qualitatively different. In this work, we attempt to locate the high temperature end of the Koga line. This is a particularly interesting range of the boundary, since its extrapolation to zero solute concentration provides information on possible temperature induced changes in the properties of pure water. To this end, we determine semi-isobaric heat capacities of aqueous 2-butoxyethanol by adiabatic calorimetry up to a maximum of 95 degrees C. The corrections due to vaporization were not applied due to the lack of required vapor pressure and thermal expansivity data. Furthermore, we measured directly the isobaric heat capacities per molar volume for aqueous 1-propanol as well as 2-butoxyethanol by differential scanning calorimetry up to 120 degrees C at 3 atm. We then took one more temperature derivative of the respective heat capacity data. The resulting third derivative quantities from the former data showed step-type anomalies, while those from the latter negative peak-type anomalies. The loci of these anomalous points seem to point to about 70 degrees C at infinite dilution.

Calorimetric and dielectric study of organic ferroelectrics, phenazine-chloranilic acid, and its bromo analog.

The heat capacities of single crystals of organic ferroelectric complexes phenazine-chloranilic acid (Phz-H(2)ca) and phenazine-bromanilic acid (Phz-H(2)ba) were measured. At temperatures below those of the reported ferroelectric phase transitions, heat capacity anomalies due to successive phase transitions were found in both complexes. Excess entropies involved in the low-temperature successive phase transitions are much larger than those due to the ferroelectric phase transitions. The temperature dependence of the complex dielectric constants showed the existence of multiple dielectric relaxation modes in both complexes and their deuterated analogs (Phz-D(2)ca and Phz-D(2)ba). We discuss the possibility of concerted hopping of neighboring protons within a hydrogen-bonded chain while taking into account the one-dimensional nature of the chain.

Spin crossover phenomenon accompanying order-disorder phase transition in the ligand of [FeII(DAPP)(abpt)](ClO4)2 compound (DAPP = bis(3-aminopropyl)(2-pyridylmethyl)amine, abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) and its successive self-grinding effect.

The spin crossover phenomenon of the recently described spin crossover complex [FeII(DAPP)(abpt)](ClO4)2 [DAPP = bis(3-aminopropyl)(2-pyridylmethyl)amine, abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole] accompanying an order-disorder phase transition of the ligand was investigated by adiabatic heat capacity calorimetry, far-IR, IR, and Raman spectroscopies, and normal vibrational mode calculation. A large heat capacity peak due to the spin crossover transition was observed at T(trs) = 185.61 K. The transition enthalpy and entropy amounted to Delta(trs)H = 15.44 kJ mol-1 and Delta(trs)S = 83.74 J K-1 mol-1, respectively. The transition entropy is larger than the expected value 60.66 J K-1 mol-1, which is contributed from the spin multiplicity (R ln 5; R: the gas constant), disordering of the carbon atom of the six-membered metallocycle in the DAPP ligand, and one of the two perchlorate anions (2R ln 2), and change of the normal vibrational modes between the high-spin (HS) and low-spin (LS) states (35.75 J K-1 mol-1). The remaining entropy would be ascribed to changes of the lattice vibrations and molecular librations between the HS and LS states. Furthermore, [Fe(DAPP)(abpt)](ClO4)2 crystals disintegrated and became smaller crystallites whenever they experienced the phase transition. This may be regarded as a successive self-grinding effect, evidenced by adiabatic calorimetry, DSC, magnetic susceptibility, and microscope observation. The relationship between the crystal size and the physical quantities is discussed.

Low-temperature heat capacity of room-temperature ionic liquid, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

Heat capacities of liquid, stable crystal, and liquid-quenched glass of a room-temperature ionic liquid (RTIL), 1-hexyl-3-methylimidazolium bis(trifluromethylsulfonyl)imide were measured between 5 and 310 K by adiabatic calorimetry. Heat capacity of the liquid at 298.15 K was determined for an IUPAC project as (631.6 +/- 0.5) J K(-1) mol(-1). Fusion was observed at T(fus) = 272.10 K for the stable crystalline phase, with enthalpy and entropy of fusion of 28.34 kJ mol(-1) and 104.2 J K(-1) mol(-1), respectively. The purity of the sample was estimated as 99.83 mol % by the fractional melting method. The liquid could be supercooled easily and the glass transition was observed around T(g) approximately 183 K, which was in agreement with the empirical relation, T(g) approximately ((2)/(3)) T(fus). The heat capacity of the liquid-quenched glass was larger than that of the crystal as a whole. In the lowest temperature region, however, the difference between the two showed a maximum around 6 K and a minimum around 15 K, at which the heat capacity of the glass was a little smaller than that of crystal.

Spin-frustrated (VO)36+-triangle-sandwiching octadecatungstates as a new class of molecular magnets.

Spin-frustrated polyoxometalates, K(11)H[(VO)(3)(SbW(9)O(33))(2)].27H(2)O (1) and K(12)[(VO)(3)(BiW(9)O(33))(2)].29H(2)O (2), containing approximately equilateral and isosceles (VO)(3)(6+)-triangles (V(IV)...V(IV) separation of 5.4-5.5 A) sandwiched by two diamagnetic alpha-B nonatungstate ligands ([SbW(9)O(33)](9)(-) and [BiW(9)O(33)](9)(-)) with approximate D(3)(h) symmetry, are found to show magnetization jumps with distinct hysteresis for the S = (1)/(2) <--> S = (3)/(2) level crossing under fast sweeping pulsed magnetic fields (approximately 10(3) T/s) at T < or = 0.5 K. This unusual phenomenon is attributed to the theoretical prediction of half step magnetization, which is expected for an antiferromagnetic spin triangle with antisymmetrical Dzyaloshinky-Moriya interaction. The degeneracy of the S = (1)/(2) states for 1 is removed by slightly lower symmetry effects of triangular structure for 2. The calorimetry of 1 and 2 shows the heat capacity anomaly at 2 < or = T < or = 20 K which is associated with a thermal excitation from the S = (1)/(2) ground states to the S = (3)/(2) state at zero field. Zero-field splitting energies (5-7 K) between S = (1)/(2) and S = (3)/(2) states for 1 and 2, readily estimated by the level-crossing field for the magnetization, allow us to measure the hyperfine-structural 22 lines due to three equivalent I = (7)/(2) (51)V nuclei, the fine-structural triplet line of the S = (3)/(2) excited state, and the g anisotropy on the high-frequency ESR spectra. The spin-frustrated (VO)(3)(6+)-triangle for 1 and 2 is a good model of the magnetization between pure quantum states S = (1)/(2) and (3)/(2) and provides a new class of single-molecule magnets.

Specific-heat anomaly caused by ferroelectric nanoregions in Pb(Mg(1/3)Nb(2/3))O3 and Pb(Mg(1/3)Ta(2/3))O3 relaxors.

The specific heat of typical relaxors, Pb(Mg(1/3)Nb(2/3))O3 (PMN) and Pb(Mg(1/3)Ta(2/3))O3 (PMT), was measured by adiabatic and relaxation methods between 2 and 420 K. A broad anomaly was found in the specific heat curve over the wide temperature range between 150 and 500 K for PMN, and between 50 and 400 K for PMT, which provides evidence for the formation of ferroelectric nanoregions (FNR) in the paraelectric matrix. The entropy of the anomaly was estimated as 3.3 J K(-1) mol(-1) and 2.9 J K(-1) mol(-1) for PMN and PMT, respectively, which implies an order-disorder-type mechanism for the formation of FNR.