Highly Emissive Whole Rainbow Fluorophores Consisting of 1,4-Bis(2-phenylethynyl)benzene Core Skeleton: Design, Synthesis, and Light-Emitting Characteristics

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• 作者：Yoshihiro Yamaguchi ; Takanori Ochi ; Yoshio Matsubara ; Zen-ichi Yoshida
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：August 13, 2015
• 年：2015
• 卷：119
• 期：32
• 页码：8630-8642
• 全文大小：939K
• ISSN：1520-5215

文摘

To create the whole-rainbow-fluorophores (WRF) having the small 螖位_em (the difference of 位_em between a given fluorophore and nearest neighboring fluorophore having the same core skeleton) values (<20 nm) in full visible region (位_em: 400鈥?50 nm), the high log 蔚 (>4.5), and the high 桅_f (>0.6), we investigated molecular design, synthesis, and light-emitting characteristics of the 蟺-conjugated molecules (D/A-BPBs) consisting of 1,4-bis(phenylethynyl)benzene (BPB) modified by donor groups (OMe, SMe, NMe₂, and NPh₂) and an acceptor group (CN). As a result, synthesized 20 D/A-BPBs (1a鈥?b>5d) were found to be the desired WRF. To get the intense red fluorophore (桅_f > 0.7, 位_em > 610 nm), we synthesized new compounds (5e鈥?b>5i) and elucidated their photophysical properties in CHCl₃ solution. As a result, 5h, in which a 4-cyanophenyl group is introduced to the para-position of two benzene rings in the terminal NPh₂ group of 5d, was found to be the desired intense red fluorophore (log鈥?= 4.56, 桅_f = 0.76, 位_em = 611 nm). The intramolecular charge-transfer nature of the S₁ state of WRF (1a鈥?b>5d) was elucidated by the positive linear relationship between optical transition energy (谓_em) from the S₁ state to the S₀ state and HOMO(D)鈥揕UMO(A) difference, and the molecular orbitals calculated with the DFT method. It is demonstrated that our concept (桅_f = 1/(exp(鈭?i>A_蟺) + 1)) connected with the relationship between 桅_f and magnitude (A_蟺) of 蟺 conjugation length in the S₁ state can be applied to WRF (1a鈥?b>5d). It is suggested that the prediction of 桅_f from a structural model can be achieved by the equation 桅_f = 1/(exp(鈭?(谓虄_a 鈥?谓虄_f)^1/2 脳 a^3/2) + 1), where 谓虄_a and 谓虄_f are the wavenumber (cm^鈥?) of absorption and fluorescence peaks, respectively, and a is the calculated molecular radius. From the viewpoint of application of WRF to various functional materials, the light-emitting characteristics of 1a鈥?b>5i in doped polymer films were examined. It was demonstrated that 1a鈥?b>5i dispersed in two kinds of polymer film (PST and PMMA) emit light at the whole visible region and have the small 螖位_em values (<20 nm) and the high 桅_f values (>0.6). Therefore, the present D/A-BPBs can be said to be the desired WRF even in the doped polymer film.