Discotic liquid crystals of transition metal complexes 58 : Novel phthalocyanine-based mesogenic monomers and polymers exhibiting spontaneous homeotropic alignment and helical tetragonal columnar structure

Two synthetizations of a novel series of phthalocyanine-based discotic liquid crystals substituted by a polymerizable group, acryloyl group or a norbornene group: 2-(12-acryloyloxydodecyloxy)-3-methoxy-9,10,16,17,23,24-hexakis (3,4-dialkoxyphenoxy)phthalocyaninato copper(II) [abbreviated as (n,12)PcCu(OCH[Formula: see text])(Acryloyl) (7: e ([Formula: see text] = 10), f ([Formula: see text] = 12), g ([Formula: see text] = 14))] and 2-(12-norborn-2-ene carbonyloxydodecyloxy)-3-methoxy-9,10,16,17,23,24-hexakis(3,4-dialkoxyphenoxy)-phthalocyaninato copper(II): [abbreviated as (n, 12)PcCu(OCH[Formula: see text])(Norb) (9e, f, g)]. Their liquid crystalline properties and homeotropic alignment were investigated using a polarizing microscope, a differential scanning calorimetry (DSC), and a temperature-variable X-ray diffractometer. As a result, each of the derivatives gave a Col[Formula: see text] mesophase in the higher temperature region, displaying perfect homeotropic alignment between the two glass plates. In order to obtain the thin film while keeping their homeotropic alignment at room temperature, attempts to polymerize the monomers, 7 and 9, in the Col[Formula: see text] phase showed homeotropic alignment. The polymerization of the acryloyl-substituted monomers (7) was not successful in any of the methods, whereas the polymerization of norbornene-substituted monomers (9) was quite successful by ring-opening metathesis polymerization with a Grubbs catalyst to obtain the novel polymers, poly-(n, 12)PcCu(OCH[Formula: see text])(Norb) (10e, f, g). Each of the polymers (10) were found to show a perfect homeotropic alignment from room temperature to ca. 200[Formula: see text]C of the decomposition temperature. Moreover, it was also revealed from temperature-variable small-angle X-ray diffraction studies that each of the polymers 10 showed a helical Col[Formula: see text] (helical tetragonal columnar) structure. The helical Col[Formula: see text] phase structure may be able for use in organic electroluminescent devices and solar cells in the future.

Discotic liquid crystals of transition metal complexes, 54: Rapid microwave-assisted synthesis and homeotropic alignment of phthalocyanine-based liquid crystals

The most difficult problem on syntheses of the phthalocyanine-based liquid crystals is the long reaction time. In order to shorten the reaction time, we have developed novel Methods A, B and D, for the syntheses of phthalocyanine-based liquid crystals by using microwave heating and/or adding a phase transfer catalysis of Aliquat 336. A series of phthalocyanine derivatives C[Formula: see text]PcZn(1) ([Formula: see text] 10, 12, 14, 16 and 18: a, b, c and e) could be successfully synthesized in a dramatically short reaction time of 30–60 min using Methods A and B by microwave heating. On the other hand, anothor series of the derivatives C[Formula: see text](OH)PcZn (2a–2e) could not be synthesized by microwave heating. Therefore, all these derivatives were synthesized using conventional Method C by oil bath heating, but the reaction took a very long time (22.5–88 h). To shorten the reaction time, we have developed Method D by oil bath heating with adding a phase transfer catalyst of Aliquat 336. In this method, we successfully shortened the reaction time from 88 h to 3 h for the synthesis of the derivative 2a. Thus, the reaction time for oil bath heating can be also greatly shortened by adding the phase transfer catalyst of Aliquat 336. Furthermore, we have established from POM, DSC and temperature-dependent X-ray diffraction measurements that the derivative C[Formula: see text]PcZn (1a) shows a very rare pseudohexagonal columnar (Col[Formula: see text] phase, and that the derivatives C[Formula: see text]PcZn (1b–1e) and C[Formula: see text](OH)PcZn (2b–2e) exhibit spontaneous perfect homeotropic alignment in a large area between two glass plates in their Col[Formula: see text] phases.

Discotic liquid crystals of transition metal complexes 52: Synthesis and homeotropic alignment of liquid crystalline phthalocyanine-fullerene dyad bridged by vanillin

We have synthesized a novel liquid crystalline phthalocyanine(Pc)-fullerene(C[Formula: see text] dyad (C[Formula: see text]S)[Formula: see text]PcCu-VAN-C[Formula: see text] (3a) bridged by an inexpensive natural product of vanillin (VAN), instead of the previous long [Formula: see text]-alkylene chain spacer. We have also synthesized a comparative dyad (C[Formula: see text]S)[Formula: see text]PcCu-OPh-C[Formula: see text] (3b) bridged by [Formula: see text]-hydroxybenzaldehyde (OPh), in order to investigate the influence of the methoxy group in the vanillin moiety on homeotropic alignment between two glass plates. Very interestingly, homeotropic alignment could be observed only for the dyad (C[Formula: see text]S)[Formula: see text]PcCu-VAN-C[Formula: see text] (3a) having a methoxy group in the vanillin moiety, whereas it could not be observed for the dyad (C[Formula: see text]S)[Formula: see text]PcCu-OPh-C[Formula: see text] (3b) having no methoxy group at the phenoxy group. It is very noteworthy that such a slight difference in these molecular structures between 3a and 3b becomes a crucial point to show the homeotropic alignment. Each of the dyads, 3a and 3b, showed two hexagonal ordered columnar (Col[Formula: see text] mesophases. Each of the Col[Formula: see text] mesophases in 3a and 3b gave an additional very strong reflection peak named as Peak H in a very low angle region of the SAXS (small angle X-ray scattering) pattern. Peak H could be established, from two different SAXS measurement methods, as one pitch in a helical structure of the fullerenes around the Pc column.

Discotic liquid crystals of transition metal complexes 50: spiranthes-like supramolecular structure of phthalocyanine-fullerene dyads

We have synthesized novel liquid crystalline Pc - C 60 dyads (CnS)6PcCu-C60 (n = 14, 16, 18: 1a–1c) by using our developed synthetic method in order to investigate the mesomorphism and alignment behavior. Each of the (CnS)6PcCu-C60 dyads shows perfect homeotropic alignment in the Colho mesophase between two glass plates for n = 14, 16, 18 and also on a glass plate for n = 14, although none of the parent Pc compounds (CnS)8PcCu and the Pc precursors (CnS)6PcCu-OH and (CnS)6PcCu-OFBA shows homeotropic alignment. It may be attributed to the strong affinity between fullerene and glass surface. Although the reason is not so clear at the present time, this is very useful guideline for the molecular design to prepare homeotropic alignment-showing discotic liquid crystals. Very interestingly, the spherical C 60 parts form a helical structure around the column formed by the disk-like Pc parts This supramolecular structure very resembles spiranthes. The spiranthes-like supramolecular structure is compatible with one-dimensional nano-array expecting the high conversion efficiency of solar cells.

Supramolecular transformation from ordered columnar to disordered columnar to tetragonal micellar structures in clicked dodeca-alkylated discotic triphenylene liquid crystals

We prepared three discotic liquid crystals (DLCs) based on a triphenylene (TP) disc functionalized with twelve alkyl peripheries. The synthesis of the discogens was performed by a click reaction using Cu(OAc)2 as the catalyst, with six triazolyl groups connecting the TP core with twelve alkyl chains. According to thermal data from differential scanning calorimetry (DSC), discogen , which has the shortest hexyl peripheries, exhibited two LC phases, and and , with decyl and tetradecyl peripheries, respectively, displayed three LC phases as a function of the temperature. Structural analyses using small- and wide-angle X-ray scattering (SAXS and WAXS) techniques revealed ordered and disordered hexagonal columnar LC phases in all the discogens. On the other hand, an unconventional micellar phase with P42/mnm symmetry consisting of thirty micelles was found only in and , when the temperature increased. The thermally induced transformation from the columnar to the micellar phase can be explained by increased chain entropy at higher temperatures. The complex micellar packing in the noncubic phase is attributed to the softness of the DLC micelles because the micellar corona consists of flexible alkyl chains. The discogen design concept in this study (i.e., the introduction of multibranched alkyl peripheries to the discotic mesogens via click chemistry) resulted in unconventional columnar-to-micellar transformation in conventional TP DLCs.

Development of structural complexity by liquid-crystal self-assembly

Since the discovery of the liquid-crystalline state of matter 125 years ago, this field has developed into a scientific area with many facets. This Review presents recent developments in the molecular design and self-assembly of liquid crystals. The focus is on new exciting soft-matter structures distinct from the usually observed nematic, smectic, and columnar phases. These new structures have enhanced complexity, including multicompartment and cellular structures, periodic and quasiperiodic arrays of spheres, and new emergent properties, such as ferroelctricity and spontaneous achiral symmetry-breaking. Comparisons are made with developments in related fields, such as self-assembled monolayers, multiblock copolymers, and nanoparticle arrays. Measures of structural complexity used herein are the size of the lattice, the number of distinct compartments, the dimensionality, and the logic depth of the resulting supramolecular structures.

Discotic liquid crystals of transition metal complexes 47: synthesis of phthalocyanine-fullerene dyads showing spontaneous homeotropic alignment

In previous work, we successfully synthesized the first columnar liquid crystalline 1:1 phthalocyanine(Pc)-fullerene( C60 ) dyad, C12(OMalC60)PcCu (4), showing spontaneous homeotropic alignment, by using Bingel reaction. However, it gave undesirable 2:1 and 3:1 Pc- C60 by-products at the same time, so that the 1:1 Pc- C60 dyad (4) could be obtained in a very low yield (20%). On the other hand, in this work we have prepared novel Pc- C60 dyads, C12(OFbaC60)PcM (8: M = Co (a), Ni (b) and Cu (c)), by using Prato reaction. Very interestingly, it gave almost only the target 1:1 Pc- C60 dyads 8a–8c in very high yields (81–96%) with negligible amount of Pc- C60 by-products. These dyads 8a–8c and the precursor Pc derivatives were characterized by polarizing microscope, differential scanning calorimeter and temperature-dependent X-ray diffractometer. Thus, it was revealed that each of the dyads and precursors shows spontaneous homeotropic alignment in their Coltet mesophase.