Kazuchika Ohta

Chromic materials. Part 1.—Liquid-crystalline behaviour and electrochromism in bis(octakis-n-alkylphthalocyaninato)lutetium(III) complexes

Novel bis(phthalocyaninato)lutetium(III) complexes substituted with long n-alkyl chains have been synthesized. These complexes, 1a–c, show three kinds of discotic mesophase (Dhd, Dob.d, and DL). Also 1a–c display the three primary colours (red, green, blue) of electrochromism in their solutions. The solutions of oxidized species of 1a–c are nearly red, although those of conventional bis(phthalocyaninato)lutetium(III) complexes are orange.

Discotic Liquid Crystalline Semiconductors

Our works on discotic liquid crystalline semiconductors are reviewed. Some of them show very fast carrier mobilities. Novel sandwich rare earth metal complex, bis[octakis(alkylthio)phthalocyaninato]lutetium(III), shows a mobility of 0.71 cm 2 /Vs, which is the fastest in liquid crystals at the present time, so far as we know. It was also found that novel octaphenoxy- and/or hexaphenoxy-substituted phthalocyanine-based discotic liquid crystals exhibit spontaneous perfect homeotropic alignment in the tetragonal columnar mesophase. The corresponding polymer films showing the perfect homeotropic alignment at room temperature could be successfully prepared. Such marvelous films can be practically utilized as organic carrier transport materials and solar batteries.

Discotic Liquid Crystals of Transition Metal Complexes, 3: the First-Established Discotic Lamellar Phase in Bis[1,3- di(p-n-alkoxyphenyl)propane-1,3-dionato]copper(II)

Abstract A new series of disk-like complexes, bis[1,3-di(p-n-alkoxyphenyl)propane-1,3-dionato]copper(II) (abbreviated as CnO-Cu, n = 1-12), has been synthesized. It was found that each of the complexes from C3O-Cu to C12O-Cu is a discogen, and that each of them has only one discotic mesophase. C3O-Cu is the first compound substituted by the shortest side chains in the discogen, so far as we know. The mesomorphic textures could be observed as mosaic textures for C3O-Cu ~ C5O-Cu and as big broken fan-like textures for C6O-Cu ~ C12O-Cu. The cutectic point calculated from Le Chatelier-Schroder relations agrees well with the found eutectic point in the binary phase diagram between C8O-Cu and C8-Cu. This is the first example of such agreement in the discogens of the organic transition metal complexes. It has been established for the first time from X-ray diffraction measurements that each of the discotic mesophases in the complexes from C6O-Cu to C12O-Cu is a discotic lamellar phase. It becomes clear that this ...

Mesomorphic phase transitions of tetraphenylporphyrins with four long aliphatic chains

Abstract Studies of 5,10,15,20-tetrakis(4-n-alkylphenyl)porphyrins revealed that the homologues with longer alkyl chains than hexyl were mesomorphic, in contrast to the non-mesomorphic alkoxy derivatives. Metal complexes (Co, Ni, Cu, Zn, and Pd) of the dodecyl derivative were also shown to exhibit mesophases. These mesophases were assigned as discotic lamellar (DL) phases by X-ray diffraction studies.

Discotic liquid crystals of transition metal complexes 37: a thermotropic cubic mesophase having Pn3m symmetry exhibited by phthalocyanine-based derivatives

In order to obtain discotic compounds exhibiting a cubic mesophase, we synthesised two new series of discotic compounds, 2,3,9,10,16,17,23,24‐octakis(4‐alkoxyphenoxy)phthalocyaninato copper(II) complexes, referred to as (C n OPhO)8PcCu (1, n = 10, 12, 14), and 2,3,9,10,16,17,23,24‐octakis(3,4,5‐trialkoxyphenoxy)phthalocyaninato copper(II) complexes, referred to as [(C n O)3PhO]8PcCu (3, n = 10, 12, 14), which both contain octakis(phenoxy)phthalocyaninato copper(II) as the central core and eight or twenty‐four long alkoxy chains in the periphery, respectively. Their mesomorphic properties were compared alongside those of the previously reported 2,3,9,10,16,17,23,24‐octakis(3,4‐dialkoxyphenoxy)phthalocyaninato copper(II) complexes, referred to as [(CnO)2PhO]8PcCu (2, n = 10, 12, 14). The phase transition behaviour of these discotic compounds (1–3) varies considerably with the number of peripheral chains. The eight‐chain‐substituted (CnOPhO)8PcCu complexes (1) exhibited only one hexagonal columnar (Colh) mesophase and did not exhibit a cubic mesophase. Sixteen‐chain‐substituted [(CnO)2PhO]8PcCu complexes (2) exhibited various columnar mesophases. In addition, the [(C n O)2PhO]8PcCu (2) derivatives with n = 12 and 14 exhibited a cubic mesophase with Pn m symmetry [Cub(Pn m)] over a very narrow temperature region (ca. 5–8°C) at high temperatures. In contrast, the twenty‐four‐chain‐substituted [(C n O)3PhO]8PcCu (3) exhibited the Cub(Pn m) phase over a much wider temperature region (ca. 90°C). Thus, it was revealed that these discotic compounds tend to exhibit a cubic mesophase on increasing the number and length of the peripheral chains. It should be emphasized that [(C n O)2PhO]8PcCu (2, n = 12, 14) and [(CnO)3PhO]8PcCu (3, n = 10, 12, 14) are the first discotic compounds exhibiting a thermotropic Cub(Pn m) phase. *. For part 36, see Ichihara et al. 1

X-Ray Diffraction Study on Discotic Lamellar Phase in Bis(1,3-di(p-n-alkoxyphenyl)propane-1,3-dionato)copper(II)

Abstract X-ray diffraction measurements have been carried out on bis(1,3-di(p-n-alkoxyphenyl)propane-1,3-dionato)copper(II) to clarify the detailed structural properties on the discotic mesophase. It is confirmed that the lamellar structure is realized in the discotic phase and the tilt angle of molecules to the layer is about 5°. The crystal-to-discotic phase transition occurs involving a large fluctuation of the inter-molecular distance along normal to the molecular plane within the layer. On the other hand, the transition from the discotic-to-isotropic liquid phase is characterized by the destabilization of the layer structure due to the randomizing of both the position and the orientation of molecules.

Discotic liquid crystals of transition metal complexes 27: supramolecular structure of liquid crystalline octakis-alkylthiophthalocyanines and their copper complexes

A series of octakisalkylthiophthalocyanines, (CnS)8PcH2 (n = 8, 10, 12, 16), and their copper(II) complexes, (CnS)8PcCu (n = 8, 10, 12, 16), have been synthesized. Their mesomorphism and supramolecular structures have been investigated by using differential scanning calorimetry, polarizing microscopy, temperature-dependent X-ray diffraction technique and temperature-dependent electronic spectroscopy. From the X-ray diffraction and electronic spectral results, it was revealed that each of the compounds has a Dh mesophase in which columnar structures the molecules form a mixture of the parts of aggregated dimers and monomers. The shapes of dimers are discussed by exciton coupling theory (Kashas rule).

Discotic columnar mesophases derived from 'rod-like' π-conjugated anion-responsive acyclic oligopyrroles

Rod-like pi-conjugated anion-responsive acyclic oligopyrroles have been reported to form stacked disk-like components that result in the formation of discotic columnar mesophases as thermotropic liquid crystals.

Discotic Liquid Crystals of Transition Metal Complexes, 5: Double Melting Behavior and Double Clearing Behavior of Discogens

Abstract Two new octa-substituted disk-like bis(β-diketonato) copper(II) complexes, 8C8-Cu and 8C8O-Cu, have been synthesized. The same type of octa-substituted copper complexes, SC9O-Cu, which was synthesized for the first time by A. M. Giroud-Godquin et al., has also been prepared. The thermal behavior of these three complexes was investigated by means of microscopic observations and DSC measurements. It was found that the 8C8-Cu exhibits not a discotic mesomorphism but a usual double melting behavior via the isotropic liquid, and that the 8C8O-Cu exhibits an unusual double melting behavior via the discophase which had not been reported by A. M. Giroud-Godquin et al. Furthermore, it was found that the 8C8O-Cu exhibits a new thermal phenomenon of “double clearing behavior” which is originated from a superheating of the transition from the crystalline phase to the discotic phase. Such double clearing behavior of the 8C8O-Cu is the first example in the mesomorphic compounds, so far as we know.

Time-of-flight analysis of charge mobility in a Cu-phthalocyanine-based discotic liquid crystal semiconductor

We used a time-of-flight method to study the charge carrier mobility properties of a molecular-aligned discotic liquid crystal semiconductor based on Cu-phthalocyanine. The heated isotropic-phase semiconductor material was sandwiched between transparent electrodes coated onto glass substrates without conventional alignment layers. This was then cooled, and a discotic liquid crystal semiconductor cell was obtained, which we used to make mobility measurements. The material had a fixed molecular alignment due to the supercooling of the hexagonal columnar mesophase. It was clarified that the carrier mobility for electrons was as high as it was for holes at room temperature. The maximum value of negative charge mobility reached 2.60×10−3cm2∕Vs, although negative carrier mobility is often much lower than positive carrier mobility in other organic semiconductors, including conventional Cu-phthalocyanine vacuum-deposited films.