부산대학교 도서관

Substitution of each phenyl in 1,3,5-triphenyl-6-oxoverdazyl with three alkoxy groups induces an ordered columnar hexagonal phase (Colh(o)) below 130°C in1b[n], while in the alkylsulfanyl analogues1a[n]additional periodicity along the columns was found rendering the phase a true three-dimensional columnar hexagonal phase (Colh(3D)) below 60°C. Both series exhibit broad absorption bands in the visible region with maxima at 540 and 610 nm in series1a[n]and at 486 and 614 nm in series1b[n]. Unusual reversible thermochromism is observed in series1b[n], in which the dark green isotropic phase turns red in the discotic phase. Analysis of1a[8]revealed redox potentials E0/+11/2 = +0.99 V and E0/ −11/2 = –0.45 V vs. saturated calomel electrode (SCE), while the potentials in the alkoxy analogue1b[8]are shifted cathodically by 0.16 V. Photovoltaic studies of1a[8]demonstrated hole mobility of μh = 1.52 × 10−3 cm2V−1s−1in the mesophase with an activation energyEa = 0.06 ± 0.01 eV. Magnetisation studies of1a[8]revealed nearly ideal paramagnetic behaviour in either the solid or fluid phase above 200 K and weak antiferromagnetic interactions at low temperatures. In contrast, a noticeable drop of about 4% in μeffwas observed during the I→Colphase transition in1b[8], which coincide with the thermochromic effect. [ABSTRACT FROM AUTHOR]