Synthesis and evaluation of dinaphthylacetylene nematic liquid crystals for high-birefringence materials Y. Arakawa, S. Nakajima, S. Kang, M. Shigeta, G. Konishi,* J. Watanabe Liq. Cryst., 39, 1063-1069 (2012). DOI:10.1080/02678292.2012.696730
Design of Weak-Donor Alkyl–Functionalized Push–Pull Pyrene Dyes Exhibiting Enhanced Fluorescence Quantum Yields and Unique On–Off Switching Properties Y. Niko, S. Sasaki, S. Kawauchi, K. Tokumaru, G. Konishi* Chem. Asian J., 9, 1797–1807 (2014). DOI: 10.1002/asia.201402088 Link
We designed, synthesized, and evaluated novel environmentally-responsive solvatochromic fluorescent dyes by incorporating weak push–pull moieties. The quantum yields of the push (alkyl)–pull (formyl) pyrene dyes were dramatically enhanced by the introduction of alkyl groups into formylpyrene (1-formylpyrene (P0): QY = 0.10; 3,6,8-tri-n-butyl-1-formylpyrene (P3a): QY = 0.90; in MeOH). The new dyes exhibited unique sensitivity to solvents polarity and H-bond donor ability, and specific fluorescence turn on-off properties (e.g., P3a: QY = 0.004, 0.80, 0.37, and 0.90 in hexane, chloroform, DMSO, and MeOH, respectively). Here, the alkyl groups act as weak donors to suppress intersystem crossing by destabilizing the HOMOs of 1-formylpyrene, while maintaining weak intramolecular charge transfer properties. Using alkyl groups as weak donors, environmentally responsive, in particular, pH-responsive fluorescent materials may be developed in the future.
Synthesis of new wide nematic diaryl-diacetylenes containing thiophene-based heteromonocyclic and heterobicyclic structures, and their birefringence properties Y. Arakawa, S. Kang, S. Nakajima, K. Sakajiri, S. Kawauchi, J. Watanabe, and G. Konishi* Liq. Cryst., 41, 642-651 (2014). DOI: 10.1080/02678292.2013.873492 Link
New monocyclic and bicyclic thiophene-based diaryl-diacetylene liquid crystal (LC) materials were synthesised and demonstrated to exhibit wide enantiotropic nematic phases. One thiophenyl-benzene derivative, in particular, displayed a stable nematic phase across a temperature range of over 100 °C. The birefringence properties of the compounds were measured using a multiple-beam interference (MBI) method, with the highest value found to be for the same thiophenyl-benzene molecule (Δn = 0.57, 550 nm) at 10 °C above the crystal-to-nematic transition temperature. Furthermore, the effects of the cyclic structure on the mesomorphic behaviours, transition temperatures, and birefringence properties were investigated in detail from both experimental and theoretical viewpoints.
1.Y. Niko, S. Kawauchi, G. Konishi, “Synthesis, Luminescence Properties, and Theoretical Insights of N-Alkyl- or N,N-Dialkyl-pyrene-1-carboxamide” Tetrahedron Lett., 52, 4843 (2011). [DOI: 10.1016/j.tetlet.2011.07.020] 2.Y. Niko, G. Konishi, “Polymer-Chain-Induced Tunable Luminescence Properties: Amphiphilic Poly(2-oxazoline)s Possessing a N,N-Dialkylpyrene-1-carboxamide Chromophore in the Side Chain” Macromolecules, 45, 2327-2337 (2012). [DOI: 10.1021/ma3001252] 3.Y. Niko, Y. Hiroshige, S. Kawauchi, G. Konishi, “Additional Insights into New Luminescence Process of Polycyclic Aromatic Hydrocarbons with Carbonyl Groups: Photophysical Properties of Secondary N-Alkyl and Tertiary N,N-Dialkyl Carboxamides of Naphthalene, Anthracene, and Pyrene” J. Org. Chem., 77, 3986-3996 (2012). [DOI: 10.1021/jo300317r] 4.Y. Niko, Y. Hiroshige, S. Kawauchi, G. Konishi, “Fundamental Photoluminescence Properties of Pyrene Carbonyl Compounds through Absolute Fluorescence Quantum Yield Measurement and Density Functional Theory” Tetrahedron, 68, 6177-6185 (2012). [DOI: 10.1016/j.tet.2012.05.072] 5.Y. Niko, G. Konishi “Molecular Design of Highly Fluorescent Dyes” J. Syn. Org. Chem. Jpn. 2012, 70, 918-927 (2012) 6. M. Uchimura, R. Ishige, M. Shigeta, Y. Arakawa, Y. Niko, J. Watanabe, G. Konishi, “Synthesis and properties of thermotropic liquid crystalline polyesters containing 9,10-diphenylanthracene moiety in the main chain” Res. Chem. Intermed. 39, 403-414 (2013). [DOI: 10.1007/s11164-012-0658-y] 7.Y. Niko, S. Kawauchi, S. Otsu, K. Tokumaru, G. Konishi, “Fluorescence Enhancement of Pyrene Chromophores Induced by Alkyl Groups through sigma-pi Conjugation: Systematic Synthesis of Primary, Secondary, and Tertiary Alkylated Pyrenes at the 1, 3, 6, and 8 Positions and Their Photophysical Properties” J. Org. Chem. 78, 3196-3207 (2013). [DOI: 10.1021/jo400128c]. 8. K. Sumi, Y. Niko, K. Tokumaru, G. Konishi, “Three-Dimensional Assembly of Pyrene Dye on Tetraphenylethane Scaffold Enhances Fluorescent Quantum Yield” Chem. Commun., 49, 3893-3895 (2013). [DOI:10.1039/C3CC41312H] 9.Y. Niko, S. Kawauchi, G. Konishi, “Solvatochromic Pyrene Analogs of Prodan Exhibiting Extremely High Fluorescence Quantum Yields in Apolar and Polar Solvents” Chem. Eur. J., 19, 9760-9765 (2013).. [DOI: 10.1002/chem.201301020] 10. S. Ji, M. Shigeta, Y. Niko, J. Watanabe, G. Konishi, “Synthesis of highly soluble fluorescent π-extended 2-(2-thienyl)benzothiazole derivatives via oxidative cyclization of 2-thienylthioanilide as the key step” Tetrahedron Lett., in press. [DOI: 10.1016/j.tetlet.2013.10.071] 11.Y. Niko, S. Sasaki, S. Kawauchi, K. Tokumaru, G. Konishi, “Design of Weak-Donor Alkyl–Functionalized Push–Pull Pyrene Dyes Exhibiting Enhanced Fluorescence Quantum Yields and Unique On–Off Switching Properties” Chem. Asian J., accepted (2014). [DOI: 10.1002/asia.201402088]
1.Y. Arakawa, S. Nakajima, R. Ishige, M. Uchimura, S. Kang, G. Konishi,* J. Watanabe, “Synthesis of diphenyl-diacetylene-based nematic liquid crystals and their high birefringence properties” J. Mater. Chem. 22, 8394-8398 (2012). [DOI: 10.1039/c2jm16002a] 2.Y. Arakawa, S. Nakajima, S. Kang, M. Shigeta, G. Konishi, J. Watanabe, “Design of an Extremely High Birefringence Nematic Liquid Crystal Based on Dinaphthyl-diacetylene Mesogen” J. Mater. Chem., 22, 13908-13910 (2012). [DOI:10.1039/C2JM32448B] 3.Y. Arakawa, S. Nakajima, S. Kang, M. Shigeta, G. Konishi, J. Watanabe, “Synthesis and evaluation of high-birefringence polymethacrylate having diphenyl-diacetylene LC moiety in side chain” J. Mater. Chem., 22, 14346-14348 (2012). [DOI: 10.1039/C2JM32489J] 4.Y. Arakawa, S. Nakajima, S. Kang, M. Shigeta, G. Konishi, J. Watanabe, “Synthesis and evaluation of dinaphthylacetylene nematic liquid crystals for high-birefringence materials” Liq. Cryst., 39, 1063-1069 (2012). [DOI:10.1080/02678292.2012.696730] 5. M. Uchimura, R. Ishige, M. Shigeta, Y. Arakawa, Y. Niko, J. Watanabe, G. Konishi, “Synthesis and properties of thermotropic liquid crystalline polyesters containing 9,10-diphenylanthracene moiety in the main chain” Res. Chem. Intermed. 39, 403-414 (2013). [DOI: 10.1007/s11164-012-0658-y] 6.Y. Arakawa, H. Furuya, G. Konishi, “Synthesis of a New Poly(dinaphthylacetylene) and Evaluation of Its Solution Conformation” Polym. Bull., 70, 47-57 (2013). [DOI: 10.1007/s00289-012-0819-6] 7. Y. Tojo, Y. Arakawa, J. Watanabe, G. Konishi, “Synthesis of High-Refractive-Index and Low-Birefringence Acrylate Polymers with Tetraphenylethane Skeleton in the Side Chain” Polym. Chem., 4, 3807-3812 (2013). [DOI: 10.1039/C3PY00377A] 8. S. Kang, S. Nakajima, Y. Arakawa, G. Konishi, J. Watanabe, “Large extraordinary refractive index in highly birefringent nematic liquid crystals of dinaphthyldiacetylene-based materials” J. Mater. Chem. C, 1, 4222-4226 (2013). [DOI: 10.1039/c3tc30640b] 9.Y. Arakawa, S. Kang, S. Nakajima, K. Sakajiri, Y. Cho, S. Kawauchi, J. Watanabe, G. Konishi, “Diphenyltriacetylenes: Novel nematic liquid crystal materials and analysis of their nematic phase-transition and birefringence behaviours” J. Mater. Chem. C, 1, 8094-8102 (2013). [DOI:10.1039/C3TC31658K] 10.Y. Arakawa, S. Kang, S. Nakajima, K. Sakajiri, S. Kawauchi, J. Watanabe, G. Konishi, “Synthesis of new wide nematic diaryl-diacetylenes containing thiophene-based heteromonocyclic and heterobicyclic structures, and their birefringence properties” Liq. Cryst., 41, 642-651 (2014). [DOI: 10.1080/02678292.2013.873492] 11. S. Kang, S. Nakajima, Y. Arakawa, M. Tokita, J. Watanabe, G. Konishi, “Evaluation of optical parameters in side-chain LC polymethacrylate with a dinaphthyl-acetylene mesogenic unit” Polym. Chem., 5, 2253-2258 (2014). [DOI: 10.1039/C2PY90049A]
Evaluation of optical parameters in side-chain LC polymethacrylate with a dinaphthyl-acetylene mesogenic unit S. Kang, S. Nakajima, Y. Arakawa, M. Tokita, J. Watanabe, G. Konishi* Polym. Chem., 5, 2253-2258 (2014). DOI: 10.1039/C2PY90049A Link
We synthesised a highly birefringent liquid crystalline (LC) side-chain polymer based on polymethacrylate with a dinaphthyl-acetylene mesogenic unit in the side chain. Three polymer types with different carbon numbers in the terminal alkoxy chain (m = 1, 3 and 6) were prepared, and their optical properties as well as phase sequential behaviours were investigated. All polymers formed a nematic phase with a wide temperature range, and a smectic C phase was detected between the nematic and crystal phases when m was extended to 6. Notably, for homologous m = 1, we successfully obtained a nematic glassy-state LC film with high optical performance under ambient temperature conditions. The optical properties of this LC film were shown to be consistent with those of a highly birefringent, low molar mass LC material, with birefringence, extraordinary and ordinary refractive indices at 550 nm of 0.36, 1.82 and 1.46, respectively.
Diphenyltriacetylenes: Novel nematic liquid crystal materials and analysis of their nematic phase-transition and birefringence behaviours Y. Arakawa, S. Kang, S. Nakajima, K. Sakajiri, Y. Cho, S. Kawauchi, J. Watanabe, G. Konishi* J. Mater. Chem. C, 1, 8094-8102 (2013). DOI:10.1039/C3TC31658K Link
Improvements in birefringence properties of LC materials are actively being pursued because of the increase in their applications in optical devices. 1,6-diphenyl-1,3,5-hexatriyne, i.e., diphenyltriacetylenes (DPTAs; number of acetylene units, n = 3) are expected to have wide nematic mesophases and exhibit extremely high birefringence properties because of the high aspect ratio of their conjugated structures. Therefore, we synthesised DPTA derivatives as novel, highly birefringent nematic liquid crystal materials. The derivatives exhibit stable enantiotropic nematic phases with longer alkoxy carbon chain lengths (i.e., with dodecyloxy groups, m = 12). High birefringence values of Δn = 0.46 at 550 nm and 140 °C, and a high extraordinary refractive index (ne) of over 2.0 were exhibited for triyne DPTA–OC6. Furthermore, we investigated the effect of the acetylene bond on the nematic transition behaviours and refractive index parameters of the conjugated oligoyne or polyyne compounds with two terminal aromatic rings. An increasing number of acetylene units (n = 1–3), i.e., extended conjugation, led to wider nematic phases and higher birefringence; the increment in Δn per acetylene unit was estimated as approximately 0.14.
Synthesis of highly soluble fluorescent π-extended 2-(2-thienyl)benzothiazole derivatives via oxidative cyclization of 2-thienylthioanilide as the key step S. Ji, M. Shigeta, Y. Niko, J. Watanabe, G. Konishi* Tetrahedron Lett., 54, 7103-7106 (2013). DOI: 10.1016/j.tetlet.2013.10.071 Link
In this paper, we synthesize highly soluble push-pull type fluorescent 2-(2-thienyl)benzothiazole dyes and evaluate of their photophysical properties. The key step is the synthesis of 2-(5'-bromothien-2'-yl)-6-alkoxybenzothiazole (2) via oxidative cyclization of 2-thienylthioanilide using PhI(OAc)2 as the oxidant. The target dyes could be easily synthesized by the Suzuki-Miyaura cross-coupling reaction of 2 and an appropriate π-donor. The photophysical properties of the 2-thienylbenzothiazole chromophore were controlled by the π-donor moiety. It was found that 2 exhibited large Stokes shifts (5345 cm-1) and a high quantum efficiency for fluorescence (QY = 0.94 in CH2Cl2). Therefore, it can be expected to be a useful photofunctional material in liquid crystal laser dyes and nonlinear optical materials.
Solvatochromic Pyrene Analogs of Prodan Exhibiting Extremely High Fluorescence Quantum Yields in Apolar and Polar Solvents Y. Niko, S. Kawauchi, G. Konishi* Chem. Eur. J., 19, 9760-9765 (2013). DOI: 10.1002/chem.201301020 Link See, ChemASAP June 25
Solvatochromic dye: Novel pyrene analogs of Prodan exhibit outstanding photophysical properties, i.e., remarkably high fluorescence quantum yield (QY) in solvents ranging from apolar hexane to polar methanol (QY 0.88, 0.97, and 0.85 in hexane, dichloromethane, and methanol, respectively), that are accompanied by strong solvatochromism and large Stokes shifts. These properties have not been previously achieved in enormous solvatochromic dyes but are quite useful for emitting materials and imaging tools.
Large extraordinary refractive index in highly birefringent nematic liquid crystals of dinaphthyldiacetylene-based materials S. Kang,* S. Nakajima, Y. Arakawa, G. Konishi,* J. Watanabe J. Mater. Chem. C, 1, 4222-4226 (2013). DOI: 10.1039/c3tc30640b Link
The extraordinary and ordinary refractive indices in highly birefringent dinaphthyldiacetylene-based nematic liquid crystals with different alkoxy tails were accurately measured by the multiple-beam interference method. The high birefringence in the nematic liquid crystals was attributed to the high value of the extraordinary refractive index, ne. The value of ne increased from 1.8 to 2.1 as the number of carbon atoms in the alkoxy tail decreased from 12 to 3, whereas the ordinary index, no, remained approximately 1.6.
Synthesis of High-Refractive-Index and Low-Birefringence Acrylate Polymers with Tetraphenylethane Skeleton in the Side Chain Y. Tojo, Y. Arakawa, J. Watanabe, G. Konishi* Polym. Chem., 4, 3807-3812 (2013). DOI:10.1039/C3PY00377A. Link
We propose a new acrylate monomer that exhibits attractive optical properties, such as good transparency, high refractive index, low birefringence, desirable optical properties, and high thermal stability. Tetraphenylethane has four aromatic rings that bind without anisotropy. A polymer with this tetraarylethane structure is expected to exhibit a high refractive index and low birefringence. In this study, we synthesized two acrylate-based polymers via radical polymerization of the acrylate monomer and methacrylate derived from 1,1′,2,2′-tetrakis(4-hydroxyphenyl)ethane. We prepared transparent coatings of the polymers on a synthetic quartz plate via spin coating and measured their refractive indices using a prism coupler. Both of the polymers exhibited a high refractive index (1.60) as compared with common PMMA (1.49) and a low birefringence, which indicated that a tetraarylethane skeleton is the preferred candidate for suppressing the birefringence of a material.
Environment-responsive multicolor fluorescent dyes based on nitrophenyl or nitrophenylethynyl oligothiophene derivatives: correlation between fluorescence and π-conjugation length S. Hachiya, K. Asai, G. Konishi* Tetrahedron Lett.54, 3317-3320 (2013). DOI: 10.1016/j.tetlet.2013.03.054 Link
We report the unique environment-responsive fluorescence of nitrophenyl or nitrophenylethynyl oligothiophene derivatives with different numbers of thiophene rings. With an increase in the number of thiophene rings, the maximum fluorescence quantum yield (QY) was obtained even in low-polarity solvents. For 5,5''-bis(4-nitrophenyl)-2,2'-bithiophene (BNP2T), a nitro-group-containing fluorescent dye without a strong donor moiety, the maximum QY of 0.43 was observed in CHCl3, which is a large value, and multicolor fluorescence with a moderate quantum yield was observed in various solvents. Thus, we can design functional nitrophenyl-based fluorescent dyes that would find applications as bioimaging probes, polarity sensors, etc.
Three-dimensional assembly of pyrene dye on tetraphenylethane scaffold enhances fluorescence quantum yield K. Sumi, Y. Niko, K. Tokumaru, G. Konishi* Chem. Commun., 49, 3893-3895 (2013). DOI:10.1039/C3CC41312H Link
A three-dimensional pyrene assembly on a tetraphenylethane skeleton enhanced the fluorescence quantum yield compared to the yield obtained when using monomeric species, without changing the shape of the emission spectrum. The unique spacing of the pyrene units may prevent intramolecular fluorescence quenching or non-radiative decay.
Fluorescence Enhancement of Pyrene Chromophores Induced by Alkyl Groups through sigma-pi Conjugation: Systematic Synthesis of Primary, Secondary, and Tertiary Alkylated Pyrenes at the 1, 3, 6, and 8 Positions and Their Photophysical Properties Y. Niko, S. Kawauchi, S. Otsu, K. Tokumaru,# G. Konishi* J. Org. Chem., 78, 3196–3207 (2013). DOI: 10.1021/jo400128c Link
We have systematically synthesized 1-, 3-, 6-, and 8-alkyl substituted pyrene derivatives using the latest synthesis methods and investigated the effects of alkyl substitution on the photophysical properties of the pyrene chromophore. Like the trimethylsilyl group, which is known to enhance the fluorescence properties of some chromophores through sigma*-pi* conjugation, alkyl groups (primary, secondary, and tertiary) enhanced the fluorescence quantum yield of the pyrene chromophore through sigma-pi conjugation in most cases. While these enhancements in the fluorescence quantum yield were beyond expectations, the results were supported by absolute measurements. These results also indicate that ubiquitous alkyl groups can be used to tune the photophysical properties of the pyrene chromophore, as well as to improve the solubility or prevent aggregation. In other words, they can be used to develop new photofunctional materials.
Unique Solvent-dependent Fluorescence of Nitro-group-containing Naphthalene Derivatives with Weak Donor-Strong Acceptor System S. Hachiya, K. Asai, G. Konishi* Tetrahedron Lett., 54, 1839-1841 (2013). DOI: 10.1016/j.tetlet.2013.01.096 Link
We synthesized nitro-group-containing pi-conjugated naphthalene derivatives with a weak donor-strong acceptor system and investigated their photophysical properties. The nitro group was introduced into naphthalene through the phenyl or phenylethynyl moiety at the C2 and C7 positions as the strong acceptor moiety, and a methoxy group was introduced into naphthalene directly at the position opposite to the nitro group, as a weak donor moiety. While 2-(4-nitrophenyl)naphthalene did not show fluorescence in various solvents, 2-methoxy-6-(4-nitrophenyl)naphthalene showed fluorescence in weakly polar solvents (QY = 0.11 in CH2Cl2), with a large Stokes shift (delta mu 12000 cm-1). Additionally, 2-methoxy-6-(4-nitrophenyl)naphthalene did not show fluorescence in polar solvents (acetonitrile) and non-polar solvents (toluene). This unique solvent-dependent fluorescence is remarkable for environmental fluorescence sensor applications.
Phenoxide-mediated Sonogashira Coupling of Trimethylsilylalkynes and Aryliodides: Practical Synthesis of Phenolic-Hydroxy-Substituted Diarylethynes and 1,4-Diarylbutadiynes M. Shigeta, J. Watanabe, G. Konishi* Tetrahedron Lett., 54, 1761-1764 (2013). DOI: 10.1016/j.tetlet.2013.01.091 Link
We successfully synthesized phenolic-hydroxy-substituted diarylethynes and 1,4-diarylbutadiynes from trimethylsilylalkynes and aryliodides via silyl-group-migration-induced deprotection of alkynes and the usual Sonogashira coupling. The phenol moiety, which works as a desilylating agent, can be attached to any position in the coupling partner. This improvement for Sonogashira coupling would be highly effective, especially when the coupling partner has a phenol moiety. Additionally, the stability of the migrated silyl moiety on the ethynylation of 2-iodophenol is discussed.
Dinuclear Oxarimethylenemethane Complexes. Photoinduced Hydrogen Abstraction from 2-Alkanones by Dinuclear Ruthenium Tetrahydride H. Suzuki, R. Shimogawa, Y. Muroi, T. Takao, M. Oshima, G. Konishi Angew. Chem. Int. Ed. 52, 1773-1776 (2013). DOI: 10.1002/anie.201208185 Link Selected as Hot Paper See, Wiley Science Cafe (in Japanese)
Hydrogen abstraction in the spotlight: UV irradiation (365 nm) of dinuclear ruthenium tetrahydride, [(Cp*Ru)(μ-H)4(RuCp*)] (Cp*=η5-C5Me5), in a 2-alkanone, such as acetone or 2-butanone, resulted in the formation of dinuclear oxatrimethylenemethane complexes, [(Cp*Ru)(μ-η3:η1-CH2COCHR)(μ-H)2(RuCp*)] (R=H and CH3), through hydrogen abstraction from the α and α′ positions of the carbonyl group.
Synthesis of a New Poly(dinaphthylacetylene) and Evaluation of its Solution Conformation Y. Arakawa, H. Furuya, G. Konishi* Polym. Bull., 70, 47-57 (2013). DOI: 10.1007/s00289-012-0819-6 Link
We report the synthesis of various substituted polyacetylenes including a novel poly(dinaphthylacetylene), poly(2-(2-ethylhexyloxy)-6-[2-(6-methoxynaphthyl-2-yl)ethynyl]naphthalene), by the use of a WCl6-Ph4Sn catalyst system, and systematically investigate their solution properties. It is found that poly(diarylacetylene)s such as poly(dinaphthylacetylene)s and poly(diphenylacetylene)s exhibit a solution morphology between rod-like and semi-flexible, whereas the less bulky poly(phenylacetylene)s, poly(silylacetylene)s, and poly(tert-butylacetylene)s exhibit a random coil morphology.
Dedicated to Professor Kazuhiko Mizuno on the occasion of his retirement (Preface) G. Konishi, H. Ikeda Res. Chem. Intermed. 39, 1-3 (2013). Link DOI: 10.1007/s11164-012-0628-4
This Special issue of Research on CHEMICAL INTERMEDIATES (RCI) are dedicated to Professor Kazuhiko Mizuno of Osaka Prefecture University, Japan, on the occasion of his retirement. During his long and productive career, Professor Mizuno conducted pioneering studies in synthetic organic photochemistry. His efforts led to the development of many novel photochemical processes that occur through a variety of reaction intermediates, including singlet or triplet excited states, excimers, exciplexes, radical cations, radical anions, radicals, and biradicals. The work has been reported in more than 250 publications.
Emission and transient absorption measurements of substitution effects of C-C triple bonds on relaxation processes of the fluorescent state of naphthalenes M. Yamaji, H. Maeda, K. Mizuno, K. Minamida, T. Maeda, K. Asai, G. Konishi, K. Mizuno Res. Chem. Intermed. 39, 321-345 (2012). (Prof. K. Mizuno special issue). Link DOI: 10.1007/s11164-012-0652-4
Synthesis and properties of thermotropic liquid crystalline polyesters containing 9,10-diphenylanthracene moiety in the main chain M. Uchimura, R. Ishige, M. Shigeta, Y. Arakawa, Y. Niko, J. Watanabe, G. Konishi,* Res. Chem. Intermed. 39, 403-414 (2013). (Prof. K. Mizuno special issue) Link DOI: 10.1007/s11164-012-0658-y
We synthesized thermotropic liquid crystalline polyesters in which a 9,10-diphenylanthracene moieties are incorporated into the main chain type of polyester forming the chiral smectic C (Sm C*). The polymers were prepared by the isopropyltitanate-catalyzed reaction of biphenyldicarboxylic acid and the corresponding diols, with the different ratios of diol of 9,10-diphenylanthracene moiety to the alkane diols (1, 5, and 10 mol%) under nitrogen atmosphere. The polymers exhibited thermotropic liquid crystals despite the presence of a bulky diphenylanthracene moiety in the main chain. The circular dichroism (CD) spectra revealed that a Sm C* phase was formed in the polymer with 1 mol% of anthracene moiety, although only an Sm A phase was formed in the other polymers. This is the first example of a Sm C* polyester containing a diphenylanthracene moiety in the main chain. Furthermore, we measured the optical properties of the polymers and found that they exhibited very high fluorescent efficiency. The fluorescence spectra of the thin film differed from that of a CH2Cl2 solution.
Preparation of Arylbutadiyne Derivatives via Silyl Migration Inspired by the Mukaiyama Protocol M. Shigeta, J. Watanabe, G. Konishi* Asian J. Org. Chem., 1, 43-46 (2012). DOI: 10.1002/ajoc.201200018 Link
One at a time: A one-pot monodesilylation and arylation of a silyl end-capped butadiyne is presented. Inspired by the Mukaiyama aldehyde alkynylation protocol, this method furnishes arylbutadiynes, which are potentially useful synthetic intermediates in the synthesis of other complex or linear structures. Thetransformation is achieved with reagents that are easily handled and avoids the need to isolate highly volatile intermediates.
Synthesis and evaluation of dinaphthylacetylene nematic liquid crystals for high-birefringence materials Y. Arakawa, S. Nakajima, S. Kang, M. Shigeta, G. Konishi,* J. Watanabe Liq. Cryst., 39, 1063-1069 (2012). Link DOI:10.1080/02678292.2012.696730
We synthesized 1,2-Bis(6-alkoxy-2-naphthyl)acetylene as a new dinaphthylacetylene with alkoxy tails of length m (DNA–OCm) LC compound, and characterized their phase behaviour by polarizing optical microscopy (POM) and differential scanning calorimetry (DSC), which all compounds exhibited each nematic phase. Also, we measured the actual, and not extrapolated, ∆n values of this target compound, and our results show the birefringence potential of the pure LC compound. And they have high birefringence values, especially, with the highest value of approximately 0.5 obtained for DNA–OC2 at 550 nm at 10 °C above the nematic-to-crystal transition temperature.
Synthesis and evaluation of high-birefringence polymethacrylate having diphenyl-diacetylene LC moiety in side chain Y. Arakawa, S. Nakajima, S. Kang, G. Konishi,* J. Watanabe J. Mater. Chem., 22, 14346-14348 (2012). Link DOI:10.1039/C2JM32489J
(Commnunication) We synthesized polymethacrylate with a diphenyl-diacetylene moiety in the side chain. It formed the nematic LC, which appears in the wide temperature region and vitrified at room temperature. The polymer exhibited a high birefringence of ~0.3 at 550 nm at room temperature.
Design of an Extremely High Birefringence Nematic Liquid Crystal Based on Dinaphthyl-diacetylene Mesogen Y. Arakawa, S. Nakajima, S. Kang, M. Shigeta, G. Konishi,* J. Watanabe J. Mater. Chem., 22, 13908-13910 (2012). Link DOI:10.1039/C2JM32448B
(Commnication) We designed dinaphthyl-diacetylene-based nematic liquid crystals with alkoxy tails (DNDA–OCm) and evaluated their birefringence (Delta n). Actual measurements of pure target compounds showed that DNDA-OC2 had the highest value of 0.62 at 550 nm at Tc + 10 °C.
