A new crystal phase of N,N,N′,N′-tetra­phenyl-1,1′-biphenyl-4,4′-diamine

The complete molecule of the title compound, C36H28N2, is generated by a crystallographic centre of inversion. The biphenyl unit is forced by symmetry to be essentially flat (r.m.s. deviation = 0.008 Å); the dihedral angles between it and the two terminal phenyl rings are 69.39 (5) and 59.53 (5)°

Infrared study on structural phase transition in (NMe4)2TCNQ3

Temperature dependence of linearly polarized infrared absorption spectrum has been measured in (NMe4)2TCNQ3 single crystals. Strongly temperature dependent electron-molecular-vibration coupled bands are observed at 2173, 1576, 1351, and 1170 cm-1. The singular behaviour of the intensity of these bands is discussed in relation to the structural phase transition observed previously by visible to near-infrared optical absorption and X-ray measurements, where the slipped TCNQ radical dimers in the low-temperature phase tend to be eclipsed in the high-temperature phase

Infrared study on pressure-induced charge delocalization in Cs2TCNQ3

Pressure dependence of several molecular vibration modes in Cs2TCNQ3 has been observed through the infrared absorption measurements. The behavior of the C-CN and C-H stretching modes suggests that phase transition takes place at around 3.6 GPa. The π* electrons, which are localized on TCNQ- molecules in the low-pressure phase, are delocalized significantly in the high-pressure phase. However, the radical-like and neutral-like molecules still coexist in the high-pressure phase indicating that the electrons are not completely delocalized. The electron-molecular-vibration (emv) coupled mode disappears in the high-pressure phase in coincident with the disappearance of the inter-radical charge transfer band S1, proving the strong coupling between them

High-pressure infrared absorption in Cs2TCNQ3 crystals grown under magnetic field

Pressure dependence of infrared absorption has been measured in Cs2TCNQ3 single crystals grown under magnetic field of 5 T (5 T crystals). The behavior of the C-CN as well as C-H stretching modes suggest that there occurs a phase transition which resembles to the one related to the insulator to metal transition in the crystals grown without magnetic field (0 T crystals). This transition, however, takes place at 4.1 GPa, slightly higher than the case of 0 T crystals. The charge transfer degree of the neutral and radical molecules are found to be ρ = 0.30-0.37 and 0.81-0.85, respectively, which are significantly different from that of 0 T crystals. These differences are suggested to arise from the changes in the relative positions of the TCNQ molecules, as indicated from the behavior of the EMV mode

Temperature dependence of electronic optical absorption in (NMe4+· TCNQ-·)2TCNQ

The temperature dependence of the linearly polarized optical absorption spectrum has been measured in single crystals of (NMe4+·TCNQ−·)2TCNQ, where NMe4 and TCNQ are tetramethylammonium and tetracyanoqui nodi methane, respectively, in the temperature range between −100 and +150 ℃. In addition to intense TCNQ−· dimer bands, strongly temperature-dependent satellite bands appear at around 1.3 eV and 1.9 eV. The singular behavior of the intensity and peak position of the 1.3 eV band shows that a second order phase transition takes place at 126 ℃. The origin of this band is discussed in relation to the mechanism of the phase transition

High pressure optical absorption in Cs2TCNQ3 complexes grown under the influence of magnetic field

Crystals of the organic semiconductor Cs2TCNQ3 have been grown under the influence of magnetic field of 5 T and their optical properties have been compared with the crystals grown without magnetic field. The magnetic field effect manifests itself as the enhancement of the intradimer charge transfer band S1, which appears at around 1.3 eV in the E//a polarization. The high-pressure optical absorption measurements have shown that the S1 band of the crystal grown at 5 T contains a new component, which is significantly intensified with increasing pressure up to 1 GPa, but diminishes as pressure increases further up to 4 GPa, and remains constant at higher pressures. This new component is additional to the component of S1 band which has similar properties to that of the crystals grown without magnetic filed, which continuously grows up to 3 GPa and abruptly broadens out at higher pressures. The new component of S1 is strongly linked to the ferromagnetism in this substance

Electronic properties of Cs2TCNQ3 crystals grown under magnetic field

The influence of magnetic field on the crystallization process has been examined in Cs2TCNQ3 (TCNQ = tetracyaniquinodimethane), a strongly Coulomb-correlated organic semiconductor. The crystal structure is unaffected by the magnetic field, while the electric, magnetic and optical properties change markedly if the magnetic field higher than a threshold (～ 4 T) is applied during the crystal growth. The high-field crystals exhibit a very weak but distinct spontaneous magnetization with the exceedingly high Curie temperature of ～ 420 K. The infrared and visible spectroscopy data show that this novel ferromagnetism concurs with the renormalization of the π* state of TCNQ radical anions, TCNQ-

イオウカキョウカルボニウムイオンノカガク : チオピリリウムカチオンノハンノウ

京都大学0048新制・課程博士工学博士甲第1403号工博第344号新制||工||258(附属図書館)3705UT51-48-J41京都大学大学院工学研究科合成化学専攻(主査)教授 吉田 善一, 教授 松浦 輝男, 教授 庄野 達哉学位規則第5条第1項該当Kyoto UniversityDA