Masahiro Ichihara

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

Different disk structures in the hexagonal columnar mesophases of 2,3‐dicyano‐6,7,10,11‐tetraalkoxy‐1,4‐diazatriphenylenes and 2,3‐dicyano‐6,7,10,11‐tetraalkoxytriphenylenes

We have synthesized two series of C2v symmetric discotic liquid crystals of 2,3‐dicyano‐6,7,10,11‐tetraalkoxy‐1,4‐diazatriphenylene [referred to as (C n O)4DADCT (1); n = 8, 10, 12, 14] and 2,3‐dicyano‐6,7,10,11‐tetraalkoxytriphenylene [referred to as (C n O)4DCT (2); n = 8, 10, 12, 14]. Polarizing microscopic observations, differential scanning calorimetry and temperature‐dependent X‐ray diffraction studies revealed that each of the (C n O)4DADCT (1) and (C n O)4DCT (2) derivatives exhibits a hexagonal ordered columnar (Colho) mesophase, and that each of the (C n O)4DADCT (1) derivatives forms monomer disks in the Colho mesophase, whereas each of the (C n O)4DCT (2) derivatives forms dimer disks in the Colho mesophase. It is very interesting that the different disk structures may originate from the kind of atoms at the α‐position to the CN groups in (C n O)4DADCT (1) and (C n O)4DCT (2).

Discotic liquid crystals of transition metal complexes 38†: peripheral chain substituent position effect on columnar mesophase and stacking structures of novel phthalocyanine-based liquid crystals

In order to clarify the peripheral chain substitution position effect on columnar mesophase and stacking structures, we have synthesized three novel series of discotic liquid crystals (1-3) having octakis(phenoxy)phthalocyaninato copper(II) as a central core and one peripheral chain at the para position (1), meta position (2) or ortho position (3) of each phenoxy group, and three more novel series of discotic liquid crystals (4-6) having the same central core and two peripheral chains at para and meta positions (4), meta and meta positions (5) or ortho and meta positions (6) of each phenoxy group. Their columnar mesophase and stacking structures were investigated with a polarizing optical microscope, a differential scanning calorimeter and a temperature-dependent X-ray diffractometer. According to the results, their columnar mesophase and stacking structures strongly depended on the peripheral chain substitution positions and the number of peripheral chains. Derivatives 3 and 5 are viscous isotropic liquid at room temperature. Derivatives 1, 2, 4 and 6 exhibit various kinds of columnar mesophases: 1 Colhd; 2 Colhd and Colho; 4 Colhd, Colrd(P21/a), Coltet.d and Cub(Pn[three bar]m); 6 Colhd, Colrd(P21/a) and Colrd(X). Moreover, derivatives 1, 4 and 6 exhibit disordered columnar mesophases. However, derivative 2 only exhibits an ordered columnar mesophase and its X-ray diffraction pattern shows a sharp reflection corresponding to a very short intracolumnar stacking distance of 3.33 A. Thus, we can drastically change the mesophase and stacking structures by the peripheral chain substitution positions and the number of peripheral chains at each phenoxy group. This is a new way of controlling mesomorphic structure.

Discotic liquid crystals of transition metal complexes, part 36: syntheses and mesomorphic properties of very large discotic liquid crystals based on triphenylenocyanine and 1,4-diazatriphenylenocyanine

Two series of very large discotic complexes of tetrakis (2,3,6,7-tetraalkoxy)triphenylenocyaninato copper(II) (abbreviated as (CnO)16TcCu; n = 8, 10, 12 and 14) and tetrakis(2,3,6,7-tetraalkoxy)-1,4-diazatriphenylenocyaninato copper(II) (abbreviated as (CnO)16TzCu; n = 8, 10, 12 and 14), were synthesized to investigate their mesomorphic properties by differential scanning calorimetry, thermogravimetry analysis, polarizing optical microscope observation and temperature-dependent X-ray studies. The results show that each of the (CnO)16TcCu derivatives exhibits two or three disordered rectangular columnar (Colrd) mesophases from room temperature to the decomposition temperature at ca. 330-340°C under nitrogen gas. However, each of the (CnO)16TzCu complexes exhibits only one ordered tetragonal columnar (Coltet.o) mesophase in an extremely wide temperature region from room temperature to the decomposition temperature at ca 300°C and ca. 340-350°C under the atmosphere and nitrogen gas, respectively. It is very interesting that the Coltet.o mesophase of (CnO)16TzCu for n = 10, 12 and 14 shows remarkable spontaneous homeotropic alignment in a large area, without disclinations and polydomains, in the temperature range from room temperature to the decomposition temperature. As far as we know, these discotic liquid crystals are the first examples to show homeotropic alignment at room temperature. Furthermore, the difference between the mesomorphic properties of (CnO)16TcCu and (CnO)16TzCu originated only from the additional eight nitrogen atoms in the central core in (CnO)16TzCu.

Discotic liquid crystals of transition metal complexes 42: the detailed phase structures and phase transition mechanisms of two Cub mesophases shown by discotic liquid crystals based on phthalocyanine metal complexes

We found in our previous works that the sandwich-type phthalocyanine-based rare earth metal complexes, bis[2,3,9,10,16,17,23,24-octakis(3,4-dialkoxyphenoxy)phthalocyaninato]lanthanoid(III) ({[(CnO)2PhO]8Pc}2M, M = Eu and Lu, n = 8–16) (1 and 3), exhibited two thermotropic cubic mesophases, Cub1 and Cub2, together with columnar mesophases. It is rare that the discotic liquid crystalline compounds show the cubic mesophase. We revealed that their symmetries of the lower temperature Cub1 mesophase and the higher temperature Cub2 mesophase were and , respectively. However, their detailed phase structures were not revealed in the previous works. In this work, we have synthesized a series of novel sandwich-type phthalocyanine-based terbium complexes, bis[2,3,9,10,16,17,23,24-octakis(3,4-dialkoxyphenoxy)phthalocyaninato]terbium(III) ({[(CnO)2PhO]8Pc}2Tb, n = 8–16) (2). Their mesomorphic properties have been investigated using polarization microscope, DSC and temperature-dependent X-ray diffraction techniques. As the result, the present Tb complexes (2) also showed two cubic mesophases, and , together with columnar mesophases, as well as the previous Eu homologs (1) and Lu homologs (3). We have furthermore investigated by using temperature-dependent electronic absorption spectroscopy to reveal their detailed phase structures and phase transition mechanism of these two Cub mesophases. We have revealed that the mesophase forms a bicontinuous structure consisting of branched columns like jungle gym, but that the mesophase forms a discontinuous structure consisting of short columns like drums that resulted from the cutting off of the branched columns.

Discotic liquid crystals of transition metal complexes 45: parity effect of the number of d-electrons on stacking distances in the columnar mesophases of octakis-(m-alkoxyphenoxy)phthalocyaninato metal(II) complexes

We have synthesized 34 novel homologous discotic liquid crystals, octakis(m-alkoxyphenoxy)phthalocyaninato metal(II) {abbreviated as (m-CnOPhO)8PcM (M = Co(1), Ni(2), Cu(3), Zn(4) and H2(5); n = 8(a), 10(b), 12(c), 14(d), 16(e), 18(f) and 20(g))}, and investigated parity effect of the number of d-electrons on the stacking distances in their columnar mesophases. It was revealed from temperature-dependent wide angle X-ray diffraction studies that each of the cobalt(II) (d7) complexes (1a–1g) and the copper(II) (d9) complexes (3b–3g) showed a single hexagonal ordered columnar (Colho) mesophase with a very short stacking distance at 3.3 A, and that the nickel(II) (d8) complexes (2a–2g) and the metal-free (d0) derivatives (5a–5g) showed a single pseudo-hexagonal ordered columnar (Colrho) mesophase with a little bit longer stacking distances at 3.4 A. Very interestingly, the nickel complex (2a) and metal-free derivatives (5a–5c) gave an extremely big (001) reflection peak with the second (002) reflection peak. Furthermore, the zinc(II) (d10) complexes (4a–4g) showed two different rectangular ordered columnar mesophases, Colro(P2/m) and Colro(P21/a), with a little bit longer stacking distance at 3.4 A. Thus, the shorter stacking distance, 3.3 A, appeared for the odd number of d-electrons, whereas the longer stacking distance, 3.4 A, appeared for the even number of d-electrons. Hence, the stacking distances depend on parity of the number of d-electrons in the central metal(II). To our best knowledge, it is the first example of parity effect on the stacking distances in columnar mesophases.

Synthesis and liquid crystallinity of fullerodendron having cyanobiphenyl groups at the terminals

Liquid-crystalline fullerodendron having cyanobiphenyl terminals was synthesized via Diels-Alder reaction of corresponding anthryl dendron and C60. The liquid-crystalline properties of the fullerodendron was investigated by polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction. Interestingly, the fullerodendron give rise to thermotropic smectic B phase, in which the hexagonal packing arrangement of C60 moiety is observed.

Liquid-Crystalline Behavior of Adducts between Pyridazine and Silver Alkylsulfonates

The silver-ion-based supramolecular adducts bearing long alkyl chains were prepared by reaction of pyridazine and silver alkylsulfonates. The-liquid crystalline behavior of the adducts was studied by differential scanning calorimetry, polarizing microscopy, temperature-dependent IR, and temperature-dependent X-ray diffraction. Each of the adducts exhibits two rectangular columnar mesophases having P2/a symmetry and has a strong tendency of parallel alignment of the alkyl chains orientating toward the surface of the glass substrate.

Very Unique Liquid Crystalline Phase Structures Having Two-Dimensional Silver Sheet for the Adducts of Phenazine and Silver Alkylsulfonates

The silver ion–based supramolecular adducts bearing long alkyl chains (Cn-Phen: n (carbon number of alkyl chain) = 12, 14, 16, 18) were prepared by reaction of phenazine and silver alkylsulfonates. Their liquid crystalline behavior was studied by differential scanning calorimetry, polarizing microscopy, and temperature-dependent X-ray diffraction techniques. Each of the adducts exhibits three mesophases with layer structures; an unidentified smectic phase (Sx), smectic C (SC), and smectic A (SA) phases. Furthermore, it was found that each of the layers has a two-dimensional silver ion sheet sandwiched above and below by two aliphatic sheets.