Flying-seed-like liquid crystals 5: Liquid crystals based on octakisphenylthiophthalocyanine and their optical properties

We have synthesized three novel flying-seed-like liquid crystals based on phthalocyaninato copper(II) (abbreviated as PcCu) substituted by bulky groups {(o-C-1)PhS (i), (m-C-1)PhS (j), [m, p(C-1)(2)]PhS (k)} instead of using long alkyl chains, in order to investigate their mesomorphism. Their phase transition behavior and the mesophase structures have been established by using a polarizing optical microscope, a differential scanning calorimeter, and a temperature-dependent small angle X-ray diffractometer. As the results, [(o-C-1)PhS](8)PcCu (8i), [(m-C-1)PhS](8)PcCu (8j) and {[m,p-(C-1)(2)]PhS}(8)PcCu (8k) show a Col tet. o mesophase at 314.9 similar to 362.9 degrees C, a Col(ro) (P2m) mesophase at 287.4 similar to 334.2 degrees C and a Col(ro) (P2m) mesophase at 331.8 similar to 386.8 degrees C, respectively. Very interestingly, each of the derivatives thus exhibits a columnar mesophase at very high temperatures. The mesomorphism is apparently originated from the novel bulky groups (i similar to k). It is also noteworthy that the Q-bands of the present PhScontaining Pc derivatives 8i similar to 8k in THF significantly red-shift by about 35 nm in comparison with those of the corresponding PhO-containing derivatives in THF.ArticleJOURNAL OF PORPHYRINS AND PHTHALOCYANINES. 19(5):639-650 (2015)journal articl

Flying-seed-like mesogens 6: Synthesis and mesomorphism of phthalocyanine derivatives substituted by pentafluorosulfanylphenoxy group

We have synthesized two novel phthalocyanines, (m-SF5PhO)(8)PcCu (7b) and (p-SF5PhO)(8)PcCu (7c), in order to investigate their flying-seed-like mesomorphism. Their phase transition behavior and the mesophase structure have been established by using a polarizing optical microscope, a differential scanning calorimeter, and a temperature-dependent small angle X-ray diffractometer. Very interestingly, the derivative (m-SF5PhO)(8)PcCu (7b) substituted a SF 5 group at m-position showed a Col(10)(P2(1)/a) (= p2gg) mesophase from rt to 315.0 degrees C, whereas the derivative (p-SF5PhO)(8)PcCu (7c) substituted a SF 5 group at p-position showed a crystalline (K) phase from rt to the decomposition temperature at ca. 336 degrees C without showing mesomorphism. Thus, the novel phthalocyanine derivative (m-SF5PhO)(8)PcCu (7b) substituted a strong electron withdrawing SF 5 group at m-position shows only one columnar mesophase in a very wide temperature region from rt to 315.0 degrees C. Furthermore, the Q-band wavelengths (672.2 and 672.1 nm) of the present (m-SF5PhO)(8)PcCu (7b) and (p-SF5PhO)(8)PcCu (7c) are shorter than that (680.3 nm) of the previous [(m-C-1) PhO](8)PcCu (5c) derivative. It can be attributed to strong electron withdrawing nature of the SF5 group on the phenoxy group.ArticleJOURNAL OF PORPHYRINS AND PHTHALOCYANINES. 20(7):822-832 (2016)journal articl

Flying-seed-like liquid crystals 7(+): Synthesis and mesomorphism of novel octakis(m-chloropyridyloxy) phthalocyanato copper(II) complexes

We have synthesized three novel octakis(m-chloropyridyloxy) phthalocyaninato copper(II) complexes, [x-PyO(m-Cl)](8)PcCu(x = 2, 3, 4: 2a-2c), keeping a chlorine atom at the meta position on the 2-, 3- and 4-pyridyloxy group, in which the nitrogen atom is located at the 2-, 3-and 4-positions, respectively. Their phase transition behavior and the mesophase structure have been established by using a polarizing optical microscope, a differential scanning calorimeter, and a temperature-dependent small angle X-ray diffractometer. Very interestingly, the mesomorphism appears with strong dependence of the position of nitrogen in m-chloropyridyloxy group. The derivative [3-PyO(m-Cl)](8)PcCu (2b) introduced a nitrogen atom at the 3-position is not mesogenic but crystalline. On the other hand, the derivative [2-PyO(m-Cl)](8)PcCu (2a) introduced a nitrogen atom at the 2-position shows columnar mesomorphism only at very high temperatures over 325 degrees C. The derivative [4-PyO(m-Cl)](8)PcCu (2c) introduced a nitrogen atom at the 4-position shows columnar mesomorphism in a very wide temperature region from rt to the decomposition temperature at 306 degrees C. From the viewpoint of N center dot center dot center dot Cl halogen bond, we have discussed about relationship between their mesomorphism and the position of nitrogen atom in m-chloropyridyloxy group.ArticleJOURNAL OF PORPHYRINS AND PHTHALOCYANINES. 21(1):48-58 (2017)journal articl

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-60) dyad (C14S)(6)PcCu-VAN-C-60 (3a) bridged by an inexpensive natural product of vanillin (VAN), instead of the previous long n-alkylene chain spacer. We have also synthesized a comparative dyad (C14S)(6)PcCu-OPh-C-60 (3b) bridged by p-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 (C14S)(6)PcCu-VAN-C60 (3a) having a methoxy group in the vanillin moiety, whereas it could not be observed for the dyad (C14S)(6)PcCu-OPh-C-60 (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(ho)) mesophases. Each of the Col(ho) 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.ArticleJOURNAL OF PORPHYRINS AND PHTHALOCYANINES. 20(12):1444-1456 (2016)journal articl

Flying-seed-like liquid crystals. Part 4:dagger a novel series of bulky substituents inducing mesomorphism instead of using long alkyl chains

We synthesized a novel series of flying-seed-like derivatives (3a-g) based on phthalocyaninato copper(II) (abbreviated as PcCu) substituted by bulky groups {PhO (a), (o-C-1)PhO (b), (m-C-1)PhO (c), (p-C-1)PhO (d), [m, p-(C-1)(2)]PhO (e), [m, m'-(C-1)(2)]PhO (f), and [m,p,m'-(C-1)(3)]PhO (g)} instead of using long alkyl chains, in order to investigate their mesomorphism. Their phase transition behaviour and the mesophase structures were established using a polarizing optical microscope, a differential scanning calorimeter, a thermogravimetry analyser and a temperature-dependent small angle X-ray diffractometer. It was demonstrated that (PhO)(8)PcCu (3a) and [(p-C-1)PhO](8)PcCu (3d) show no mesophase, whereas [(m-C-1)PhO](8)PcCu (3c), {[m,p-(C-1)(2)]PhO}(8)PcCu (3e), {[m,m'-(C-1)(2)]PhO}(8)PcCu (3f), and {[m, p, m'-(C-1)(3)] PhO}(8)PcCu (3g) show various kinds of columnar mesophases of Col(ro)(P2(1)/a), Col(ro)(P2(1)/a), Col(ro)(C2/m) and Col(tet.o), respectively, while [(o-C-1)PhO](8)PcCu (3b) shows a monotropic Col(ro)(P2m) mesophase. Thus, we revealed that mesomorphism could be induced by these novel bulky substituents instead of using long alkyl chains, and that the mesophase structures were greatly affected by the number and position of the methoxy groups. In particular, it is very interesting that the derivatives with methoxy group(s) at the meta position(s), namely, 3c, 3e, 3f and 3g, tend to show enantiotropic mesophase(s), whereas neither the derivative with no methoxy group, 3a, nor the derivative with a methoxy group at the para position, 3d, show a mesophase.ArticleRSC ADVANCES. 5(18):13828-13839 (2015)journal articl

Phthalocyanine-based discotic liquid crystals switching from a molten alkyl chain type to a flying-seed-like type

first published on 29 Jun 2017We have synthesised a series of phthalocyanine-based discotic liquid crystals, (m-CnOPhO)(8)PcCu (n = 1-20: 2a-o), and investigated their mesomorphism by using a polarizing optical microscope (POM), a differential scanning calorimeter (DSC) and a temperature-dependent small angle X-ray diffractometer. We found that each of the derivatives 2a-o shows mesomorphism. However, the mesomorphism of the (m-CnOPhO)(8)PcCu derivatives strongly depends on the alkoxy chain length (n). The mesomorphism of the short chain-substituted derivatives 2a-e for n = 1-5 is a flying-seed-like type induced by flip-flop of the peripheral bulky substituents, whereas the mesomorphism of the long chain-substituted derivatives 2j-o for n = 10-20 is a conventional molten alkyl chain type induced by melting of the long alkyl chains. The moderately long chain derivatives (2f-i) for n = 6-9 in between show both types of mesophases. The detailed temperature-dependent X-ray diffraction measurements were carried out for three representative derivatives, 2b (n = 2 for n = 1-5), 2h (n = 8 for n = 6-9), and 2o (n = 20 for n = 10-20). As a result, we revealed that the Col(ro)(P2m) mesophase in 2b (n = 2) gave a halo denoted as Halo(arom). at d congruent to 5.2 angstrom due to flip-flop of the bulky aromatic substituents, and that the Colho mesophase in 2o (n = 20) gave a halo denoted as Halo(alkyl) at d congruent to 4.6-4.8 angstrom due to melting of the long alkyl chains. Therefore, we can distinguish the type of mesophase from Halo(arom). and Halo(alkyl). Very interestingly, the (m-C8OPhO)(8)PcCu (2h) derivative having moderately long alkyl chains gave Halo(alkyl) at about 4.8 angstrom in the lower temperature mesophase of Col(ho), but Halo(arom). at about 5.2 angstrom in the higher temperature mesophase of Col(ro)(P2(1)/a). This means that melting of the alkyl chains induces the Col(ho) phase in the lower temperature region, but that flip-flop of the bulky aromatic substituents induces the Col(ro)(P2(1)/a) phase in the higher temperature region. This unusual reverse phase transition sequence from a higher symmetry of the Col(h) mesophase to a lower symmetry of the Col(r) mesophase on a heating stage is attributable to such a unique stepwise melting of these two different types of substituents. To the best of our knowledge, this mesogen (2h) is the first example switching mesomorphism from the molten alkyl chain type to the flying-seed-like type in a discotic liquid crystal.ArticleJOURNAL OF MATERIALS CHEMISTRY C. 5(29):7297-7306 (2017)journal articl

Discotic liquid crystals of transition metal complexes, 53: synthesis and mesomorphism of phthalocyanines substituted by m-alkoxyphenylthio groups

We have successfully synthesized a series of novel octakis(m-alkoxyphenylthio) phthalocyaninato copper(II) complexes, (m-CnOPhS)(8)PcCu (n = 2, 4, 6, 8, 10, 12, 14, 16: 1b similar to 1i), by our developed method to reveal their mesomorphism. The phase transition behavior and mesophase structures have been established by using a polarizing optical microscope, a differential scanning calorimeter, and a temperature-dependent small angle X-ray diffractometer. Interestingly, the very short chain-substituted derivatives, (m-C1OPhS)(8)PcCu (1a) and (m-C2OPhS)(8)PCu (1b), show a hexagonal ordered columnar (Col(ho)) mesophase, whereas each of the other longer-chain-substituted derivatives, (m-CnOPhS)(8)PcCu (n = 4 similar to 16: 1c similar to 1i), shows only rectangular ordered columnar (Col(ro)) mesophase(s). In contrast to the present longer-chain-substituted phenylthio derivatives, each of the previous longer-chain-substituted phenoxy derivatives, (m-CnOPhO)(8)PcCu (n = 10-20), shows a different columnar mesophase of Colho. We discuss this difference of mesomorphism from the viewpoint of the different steric hindrance originated by the peripheral substituents, PhO and PhS groups. Moreover, we could estimate the optical band gaps of (m-C10OPhO)(8)PcCu and (m-C10OPhS)(8)PcCu (1f) from absorption edge of the Q-bands to be 1.79 eV and 1.70 eV, respectively. Therefore, the phenylthio-substituted derivative gave a narrower band gap by ca. 0.1 eV in comparison with the phenoxy-substituted derivative.ArticleJOURNAL OF PORPHYRINS AND PHTHALOCYANINES. 21(3):159-178 (2017)journal articl

Discotic liquid crystals of transition metal complexes 51(dagger): Synthesis and mesomorphism of flat-pumpkin-shaped phthalocyanine-fullerene dyads

We have synthesized a novel type of donor-acceptor liquid crystalline material, phthalocyanine-fullerene (Pc-C-60) dyad, [m,p,m'-(C14O)(3)PhO](6)PcCu-C-60 (7), and the Pc precursors, [m,p,m'-(C14O)(3)PhO](6)PcCu-OFBA (6) and [m,p,m'-(C14O)(3)PhO](6)PcCu-OH (5), and established their mesomorphism by using a polarizing optical microscope, a differential scanning calorimeter and a small angle X-ray diffractometer. Very interestingly, their corresponding previous parent Pc derivative, [m,p,m'-(C14O)(3)PhO](8)PcCu (4), shows a very wide temperature region ca. 90 degrees C of a bicontinuous Cub(Pn3m) mesophase, whereas the present children Pc precursors (5 and 6) and Pc-C-60 dyad 7 show not the Cub mesophase but a Col(ho) mesophase. It is also noteworthy that the staking distance in the Col(ho) mesophase of the Pc-C-60 dyad 7 was a very big value of ca. 9.1 angstrom, which is the biggest in discotic liquid crystals to our best knowledge. It may be originated from the biggest excluded volume caused by thermal fluctuation of peripheral long alkoxy chains at m, m'-positions. The excluded volume caused by thermal fluctuation of the peripheral long chains is so big that the molecular shape of the Pc derivative 4 and the Pc-C-60 dyad 7 very resembles a flat pumpkin.ArticleJOURNAL OF PORPHYRINS AND PHTHALOCYANINES. 18(10-11):856-868 (2014)journal articl

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

We have synthesized novel liquid crystalline Pc-C-60 dyads (CnS)(6)PcCu-C-60 (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)(6)PcCu-C-60 dyads shows perfect homeotropic alignment in the Col(ho) 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)(8)PcCu and the Pc precursors (CnS)(6)PcCu-OH and (CnS)(6)PcCu-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.ArticleJOURNAL OF PORPHYRINS AND PHTHALOCYANINES. 18(5):366-379 (2014)journal articl