Hidetomo Mukai

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 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 39: columnar mesomorphism and homeotropic alignment speed of sandwich-type of double-deckers and triple-deckers based on phthalocyaninato lutetium metal complexes

A series of sandwich-type metal complexes, bis[2,3,9,10,16,17,23,24-octakis(3,4-dialkoxyphenoxy)phthalocyaninato]lutetium(III) ({[(CnO)2PhO]8Pc}2Lu (n = 8−16): double-deckers (2)), were synthesized. As the by-product, tris[2,3,9,10,16,17,23,24-octakis(3,4-diakoxyphenoxy)phthalocyaninato]dilutetium(III) ({[(CnO)2PhO]8Pc}3Lu2 (n = 8, 9, 11, 12, 14, 16): triple-deckers (3)) were successfully separated. The mesomorphic properties of these double-deckers (2) and triple-deckers (3) were investigated using a polarization microscope, differential scanning calorimetry and temperature-dependent X-ray diffraction techniques. The double-deckers (2) showed Colh, Cub and Coltet mesophases for n ≥ 10. On the other hand, the triple-deckers (3) showed only a Colr mesophase for n = 8, only a Coltet mesophase for n = 14, and both Colr and Coltet mesophases for n = 9, 11, 12 and 16. For the Coltet mesophase, both the double-deckers (2) and the triple-deckers (3) exhibited spontaneous homeotropic alignment in a large area. In comparison with the homeotropic alignment of these present lutetium complexes 2, 3 and the previous copper complexes, 2,3,9,10,16,17,23,24-octakis(3,4-dialkoxyphenoxy)phthalocyaninato copper(II) ([(CnO)2PhO]8PcCu (n = 9-14): single-decker (1)), the alignment was fast, slow and fast, respectively, in the order of the single-deckers (1), double-deckers (2) and triple-deckers (3). Very interestingly, the complexes 1 and 3 which have flat Pc macrocycles gave fast alignment, whereas the complexes, 2, which have non-flat Pc macrocycles, gave slow alignment. Thus, it was revealed for the first time that the flatness of discotic liquid crystalline molecules influences the speed of homeotropic alignment.

Discotic liquid crystals of transition metal complexes 40: unique double-clearing behavior of a series of novel discotic metallomesogens based on bis(phthalocyaninato)europium(III) complexes

It has long been believed that the phase transition behavior and clearing points (c.p.s) of phthalocyanine-based metallomesogens scarcely change regardless of the kind of central metal. In this work, we have synthesized a series of novel sandwich-type, europium complexes, bis[2,3,9,10,16,17,23,24-octakis(3,4-dialkoxyphenoxy)phthalocyaninato]europium(III) (abbreviated as {[(CnO)2PhO]8Pc}2Eu (n = 8-16) (2a–2i)). Their mesomorphic properties were investigated by polarization microscope, differential scanning calorimeter and temperature dependent X-ray diffraction techniques to make a comparison with the phase transition behavior and c.p.s of the previously reported lutetium homologs ({[(CnO)2PhO]8Pc}2Lu (n = 8-16) (1). Very interestingly, the c.p.s of {[(CnO)2PhO]8Pc}2Eu complexes (2) are higher by 35–61°C than those of {[(CnO)2PhO]8Pc}2Lu complexes (1) having the same chain length (n). Furthermore, these Eu complexes (2) exhibited unique double-clearing behavior, whereas the Lu complexes (1) did not. For instance, the Eu complex (2i: n = 16) exhibited the following phase transition sequence: crystalline phase (K) 49°C Colh 133°C 158°C 216°C I.L.; the I.L. very slowly transformed into a Coltet mesophase; on further heating, Coltet cleared into I.L. again at 240°C. On the other hand, the corresponding Lu complex (1i: n = 16) exhibited a phase transition sequence of K 50°C Colh 124°C 148°C Coltet 205°C I.L., and did not exhibit the doubleclearing behavior. Thus, it was revealed for the first time, in the phthalocyanine-based metallomesogens, that the central metal had a large influence on their c.p.s and their phase transition behavior.

Discotic liquid crystals of transition metal complexes 43: the effect of the length of alkoxy chains at the m-positions in phenoxy groups on mesomorphism for the novel octaphenoxyphthalocyaninato copper(II) and terbium(III) complexes

We have synthesised two novel series of octaphenoxyphthalocyaninato copper(II) complexes, (m-C n O)PcCu (n = 2–10: 2b–f), and bis(octaphenoxyphthalocyaninato)terbium(III) complexes, [(m-C n O)Pc]2Tb (n = 2–10: 3b–f), which were substituted by dodecyloxy chains at the p-positions in the phenoxy groups and various length of alkoxy chains at the m-positions in the phenoxy groups. Their mesomorphic properties were investigated by polarising microscopy, differential scanning calorimetry (DSC) and temperature-dependent X-ray diffraction techniques. The Cu complex (2b) and the Tb complexes (3b–d), having shorter chains at the m-positions in the phenoxy groups, exhibited a lamellocolumnar (ColL) mesophase. Moreover, it was revealed that the complexes (2 and 3) tend to change their mesophases of the order of Colh → ColL → Colr → Cub → Coltet with elongating the length of the alkoxy chains at the m-positions. †Reference [1].

Discotic liquid crystals of transition metal complexes 41: influence of rare-earth metal ions on clearing points of sandwich-type bis[octakis(3,4-didodecyloxyphenoxy)phthalocyaninato]lanthanoid(III) complexes

It has long been believed that the phase transition behavior and clearing points (c.p.s.) of phthalocyanine-based metallomesogens scarcely change regardless of the kind of central metal. In this work, we have synthesized a series of novel sandwich-type phthalocyanine-based lanthanoid complexes, bis[2,3,9,10,16,17,23,24-octakis(3,4-didodecyloxyphenoxy)phthalocyaninato]lanthanoid(III) (abbreviated as {[(C12O)2PhO]8Pc}2M, M = La, Ce, Eu, Gd, Tb, Yb and Lu: 1–7). Their mesomorphic properties were investigated by polarization microscope, DSC and temperature-dependent X-ray diffraction techniques to compare with the phase transition behavior and c.p.s. of the complexes. Very interestingly, the c.p.s. of these seven rare-earth metal complexes increased in an order of La (1) → Ce (2) → Eu (3), reached to a maximum for Gd (4), and decreased in an order of Tb (5) → Yb (6) → Lu (7). We have noticed that their rise and fall of c.p.s. correspond to the values of total spin quantum number (S) of the central rare-earth ...