Masuo Takeda

The Pair Intermolecular Interaction Energy of the Two Nematogenic Liquid Crystals

Abstract The dispersion term in the intermolecular potential calculated from the Rayleigh-Schrodinger perturbation theory exhibits the similar angle dependence as assumed by Maier-Saupe for the model system of MBBA.

A Mössbauer spectroscopic study of the electronic states of tetragonal iron(II) pyridine complexes

Abstract The Mossbauer spectra of FeL 4 Cl 2 (L = pyridine, 4-methylpyridine, 3-acetylpyridine) and Fe L 2 Cl 2 (L = pyridine, 4-acetylpyridine, 4-chloropyridine, 3-chloropyridine) were measured between 4·2 and 290°K. The magnitudes of the quadrupole splittings ( ΔE Q ) of FeL 4 Cl 2 are much larger than those of FeL 2 Cl 2 , probably because of the different orbital ground-states: d xy for FeL 4 Cl 2 and, most likely, d xz and d yz for FeL 2 Cl 2 . The energy separation, δt 2 g , was estimated from the temperature dependence of ΔE Q . No effect on the isomer shift of a substituent at the 3- or 4-position of pyridine is observed in either FeL 4 Cl 2 or FeL 2 Cl 2 .

Moussbauer Spectroscopic Study of the Reentrant Phase Transitions in TBA[Fe(tdas)2]

Abstract Temperature dependence of 57Fe Mossbauer spectra for TBA[Fe(tdas)2] is measured to obtain the information on the spin state and the phase transitions. The large quadrupole splitting due to the S = 3/2 spin state increases reenteringly in the intermediate temperature region (190–230 K on cooling and 200–240 K on heating). The small increase in the quadrupole splitting and the continuous decrease in the isomer shift suggests the 3/2 spin state does not change, supporting the interpretation of the magnetic susceptibility.

Proton Spin – Spin Relaxation Time in MBBA

Abstract The proton spin-spin relaxation time of the liquid crystal, N-(p-methoxybenzylidene)-p-butylaniline (MBBA), was obtained by a modified Carr-Purcell method in the temperature range from – 110 to 65°C. The measurements were carried out both on the warming and cooling processes of the sample. Two discrete relaxation times were found in either the solid or the nematic phase of the sample. The origin of these two relaxation times was discussed on the basis of the fraction of each component. In the solid phase an anomalous temperature dependence of these two relaxation times was observed over 0 ∼ 15°C only on the warming process, and it was interpreted as an indication of the structural change toward a closer molecular packing. In the nematic phase, two relaxation times showed a different temperature dependence around 20 ∼ 25°C and then came to show a similar temperature dependence at higher temperature. This was explained in terms of a steric hindrance between adjacent MBBA molecules enhanced by the m...

13C Relaxation Times Study of Liquid Crystalline p-Methoxybenzylidene-p-Butylaniline

Abstract The 13C relaxation times T1 and T2 for all resolved carbon lines are reported as a function of temperature in the nematic and isotropic phases of MBBA. Also the NOE measurements were performed in the both nematic and isotropic phases. The discontinuity of 13C T2s was observed at the nematic-isotropic transition point. From T1 and T2 data, it is shown that a short range order remains in the small temperature range just above the isotropic-nematic transition point. The region of small temperature dependence was found in the plots of 13C T1 vs reciprocal temperature. The rotational motion around the molecular axis was estimated to be three orders faster than the motion around the axis perpendicular to the molecular axis.

Tellurium-125 Mössbauer spectra of some tellurium subhalides

The 125Te Mossbauer spectra at 4.2 K for the crystalline tellurium subhalides Te3Cl2, Te2X (X = Br or I), Te2Br0.75- I0.25, β-Tel, and α-Tel show the presence of at least two different tellurium sites in each subhalide in accordance with their known crystal structures. The chemical isomer shifts δ(relative to Zn125mTe at 4.2 K) in four different types of co-ordination have been found to be 0.6 mm s–1 for trigonal bipyramidal tellurium atoms [Te(Te)2(Cl)2E], 0.8–1.0 mm s–1 for square-planar (pseudo-octahedral) tellurium atoms [Te(Te)2(X)2E2](X = Br or I), and 0.8 mm s–1 for two-co-ordinate (pseudo-tetrahedral) tellurium atoms [Te(Te)2E2]. The symbols in square brackets indicate the nearest-neighbour environment of the relevant tellurium atom, the symbol E being used to represent an essentially non-bonding pair of electrons. The corresponding quadrupole splittings for the four environments were 11.0, 12.1–13.7, 3.4–6.1, and 8.1 mm s–1 respectively. The bonding scheme for square-planar tellurium atoms in the tellurium subhalides is considered to involve two three-centre four-electron bonds and is thus similar to that in the isostructural and isoelectronic species [ICl4]– and XeCl4. The Mossbauer spectra at 4.2 K for the glassy phases Te2Br0.75I0.25 and TeBr2 were different from those of the corresponding crystalline compounds but again showed the existence of at least two different tellurium sites in each compound.