Diastereoselective Photocycloaddition Reactions of 2-Naphthalenecarboxylates and 2,3-Naphthalenedicarboxylates with Furans Governed by Chiral Auxiliaries and Hydrogen Bonding Interactions
H. Maeda, N. Koshio, Y. Tachibana, K. Chiyonobu, G. Konishi, K. Mizuno
J. Photochem. Photobiol. A: Chem., 349, 7–17 (2017)
DOI: 10.1016/j.jphotochem.2017.08.052
TOC: to be announced.
Abstract: to be announced.


# by konishi_lab | 2017-08-21 12:33 | 2017 (7)


小西 玄一


# by konishi_lab | 2017-07-29 10:28 | 2017 (7)


The K-region in Pyrenes as a Key Position to Activate Aggregation-Induced Emission: Effects of Introducing Highly Twisted N,N-Dimethylamines
S. Sasaki, S. Suzuki, K. Igawa, K. Morokuma, G. Konishi*
J. Org. Chem., 82, 6865–6873 (2017).
DOI: 10.1021/acs.joc.7b00996

A new design strategy to activate aggregation-induced emission (AIE) in pyrene chromophores is reported. In a previous report, we demonstrated that highly twisted N,N-dialkylamines of anthracene and naphthalene exhibit drastic AIE when these donors are introduced at appropriate positions to stabilize the S1/S0 minimum energy conical intersection (MECI). In the present study, this design strategy was applied to pyrene: the introduction of N,N-dimethylamine substituents at the 4,5-positions of pyrene, the so-called K-region, are likely to stabilize MECIs. To examine this hypothesis, four novel pyrene derivatives, which contain highly twisted N,N-dimethylamino groups at the 4- (4-Py), 4,5- (4,5-Py), 1- (1-Py), or 1,6-positions (1,6-Py) were tested. The non-radiative transitions of 107 s-1), so that its fluorescence quantum yield in acetonitrile decreases to Φfl = 0.04. The solid-state fluorescence of 4,5-Py is efficient (Φfl = 0.49). In contrast, 1,6-Py features 107 s-1) that is subject to severe quenching (Φfl = 0.03) in the solid state. These results underline that the chemistry of the pyrene K-region is intriguing, both from a photophysical perspective and with respect to materials science.


# by konishi_lab | 2017-07-10 07:28 | 2017 (7)




# by konishi_lab | 2017-06-14 21:36 | 2017 (7)

Press Release



# by konishi_lab | 2017-06-05 10:40 | News


A Smart Network Polymer with Bis(piperidyl)naphthalene Cross-linkers: Selective Fluorescence Quenching and Photodegradation in the Presence of Trichloromethyl–Containing Chloroalkanes
S. Sasaki, Y. Sugita, M. Tokita, T. Suenobu, O. Ishitani, G. Konishi*
Macromolecules, 50, 3544–3556 (2017).
DOI: 10.1021/acs.macromol.7b00213

Abstract: 1,4-Bis(piperidyl)naphthalene (1,4-BPN) was employed as a cross-linker for poly(n-butyl methacrylate) gels to generate soft materials that exhibit selective fluorescence quenching and photodegradation in 1,1,1-trichloromethyl-containing chloroalkanes. In chloroform and 1,1,1-trichloroethane, 1,4-BPN is subject to efficient fluorescence quenching via the formation of exciplexes, which results in rapid photodegradation. Similarly, poly(n-butyl methacrylate) gels cross-linked with 1,4-BPN were highly fluorescent and stable in various organic solvents and chloroalkanes but exhibited less intense fluorescence and rapid photodegradation in 1,1,1-trichloromethyl-containing chloroalkanes. Upon swelling in 1,1,1-trichloroethane, these gels exhibited a steep drop in the storage modulus during first 10 s of photoirradiation (λ = 365 nm). Further photoirradiation for 10–30 min led to the decomposition of the gels. Thus, we propose that the 1,4-BPN-based cross-linker can be used for the facile preparation of diverse polymeric materials with synergistic fluorescence, detection, and photodecomposition properties toward unreactive and neutral analytes.


# by konishi_lab | 2017-05-09 14:33 | 2017 (7)


Open Access
Thermo-responsive fluorescence of AIE-active
poly(N-isopropylacrylamides) labeled with highly twisted

S. Sasaki, G. Konishi*
RSC Adv., 7, 17403-17416 (2017).
DOI: 10.1039/C7RA01212H

Highly twisted bis(N,N-dialkylamino)arenes, which represent a new class of viscosity-sensitive fluorophores with aggregation-induced emission (AIE) luminogens, were introduced as co-monomers and cross-linkers into poly(N-isopropylacrylamides) (PNIPAMs). Despite the excellent performance of these bis(N,N-dialkylamino)arenes as fluorophores that are sensitive to the steric environment, synthetic methods to endow them with other reactive groups have not yet been reported. This study presents short synthetic pathways to 9,10-bis(N,N-dialkylamino)anthracenes (BDAAs) and 1,4-bis(N,N-dialkylamino)-2,3-dimethylnaphthalenes (DMe-BDANs) with hydroxyl groups at their alkyl chains. These hydroxyl groups were acylated to afford methacrylate moieties, which were subsequently used for the co-polymerization with N-isopropylacrylamide. At T = 20 °C, the resulting BDAA-containing PNIPAMs exhibited faint fluorescence (Φfl ≈ 0.05) in THF, whereas DMe-BDAN-containing PNIPAMs showed substantially stronger fluorescence in THF (Φfl ≈ 0.32) and water (Φfl ≈ 0.55) relative to the corresponding monomers. Moreover, BDAA-containing PNIPAMs featured a sharp increase of fluorescence intensity and quantum yield at T = 27–35 °C, while DMe-BDAN-containing PNIPAMs exhibited a continuous decrease of fluorescence intensity and Φfl with increasing temperature.


# by konishi_lab | 2017-03-22 08:08 | 2017 (7)


Open Access
The design of liquid crystalline bistolane-based materials with extremely high birefringence

Y. Arakawa, S. Kang, H. Tsuji, J. Watanabe, G. Konishi*
RSC Adv., 6, 92845-92851 (2016).
DOI: 10.1039/C6RA14093A

We designed three new bistolanes with alkylsulfanyl groups. A symmetric derivative contains short terminal methylsulfanyl groups (-SC3) on both ends, while two asymmetric derivatives contain a methylsulfanyl group on one end, as well as a highly polarizable cyano (-CN) or isothiocyanate (-NCS) group on the other end. These materials exhibited a well-defined enantiotropic nematic phase, as well as an extremely high birefringence (Δn > 0.6). Most notably, the NCS derivative achieves an extremely high value of 0.77 at 550 nm. These results should be helpful for the design and synthesis of novel nematic materials with high birefringence.


# by konishi_lab | 2016-12-08 09:52 | 2016 (7)


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Gen-ichi KONISHI lab, Tokyo Institute of Technology

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# by konishi_lab | 2016-09-12 15:50 | News


Highly twisted N,N-dialkylamines as a design strategy for turn of typical aromatic hydrocarbons as steric environment-sensitive fluorophores
S. Sasaki, S. Suzuki, W. M. C. Sameera, K. Igawa, K. Morokuma, G. Konishi*
J. Am. Chem. Soc., 138, 8194–8206 (2016).
DOI: 10.1021/jacs.6b03749

This paper is highlighted in Cutting-Edge Chemistry, American Chemical Society (ACS)
Organic, Organometallic, and Metallic Luminogens (15 Aug, 2016)


The steric-environment sensitivity of fluorescence of 9,10-bis(N,N-dialkylamino)anthracenes (BDAAs) was studied experimentally and theoretically. A new design strategy to tune simple aromatic hydrocarbons as efficient aggregation-induced emission (AIE) luminogens and molecular rotors is proposed. For a variety of BDAAs, prominent Stokes shifts and efficient solid-state fluorescence were observed. Calculations on BDAA-methyl suggested that in the ground state (S0) conformations, the pyramidal amine groups are highly twisted, so that their lone-pair orbitals cannot conjugate with the anthracene π orbitals. Fluorescence takes place from the S1 minima, in which one or both amine groups are planarized. The stability of the S1 excited state minima as well as destabilization of the S0 state is the origin of large Stokes shift. Experimental measurement of the non-adiabatic transition rate suggests that para disubstitution by dialkylamino (or strongly electron-donating) groups is a key for fast internal conversion. Minimum energy conical intersection (MECI) between S1 and S0 states was found to have a Dewar-benzene like structure. Although this can be reached efficiently in liquid phase for fast internal conversion, a large amplitude motion is required to reach this MECI, which is prohibited in the solid state and caused efficient AIE. This strategy is used to find experimentally that naphthalene analogues are also efficient AIE luminogens. The flexibility of alkyl chains on amino groups is also found to be important for allowed charge-transfer transition. Thus, three points (1. highly twisted N,N-dialkylamines, 2. substitution at the para positions 3. with flexible alkyl groups) were proposed for activation of small aromatic hydrocarbons.


# by konishi_lab | 2016-07-06 18:01 | 2016 (7)