Synthesis and Photophysical Properties of Colorful Salen-Type Schiff Bases

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• 作者：Jinghui Cheng ; Kaiyi Wei ; Xiaofeng Ma ; Xiangge Zhou ; Haifeng Xiang
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：August 15, 2013
• 年：2013
• 卷：117
• 期：32
• 页码：16552-16563
• 全文大小：659K
• 年卷期：v.117,no.32(August 15, 2013)
• ISSN：1932-7455

文摘

A series of colorful Salen-type Schiff bases derived from the different diamine bridges including 1,2-ethylenediamine (Et1鈥?b>Et3), 1,2-cyclohexanediamine (Cy1鈥?b>Cy3), 1,2-phenylenediamine (Ph1鈥?b>Ph4), dicyano-1,2-ethenediamine (CN1鈥?b>CN3), phenazine-2,3-diamine (Phen1鈥?b>Phen3), and naphthalene-2,3-diamine (Naph1 and Naph2) have been designed and prepared. The presence of electron-accepting substituents, electron-donating substituents, donor鈥揳cceptor (DA) systems, and/or 蟺-extended systems leads to not only full absorption and emission spectra (300鈥?00 nm) in the visible region but also high fluorescence quantum yields up to 0.83 in solution. The experimental results and density functional theory (DFT) calculations have proved that the highest occupied molecular orbital (HOMO) levels, the lowest unoccupied molecular orbital (LUMO) levels, and consequently the energy gaps of these Salen ligands can be well tuned. The LUMO levels of these Salen ligands are mainly affected by the diamine bridges, whereas both the HOMO and LUMO levels are influenced by the phenol fragments. Adding Cu²⁺ and Co²⁺ to CN1 solution leads to a drastic color change from pink into brownish red and purple, respectively, which is useful not only for the ratiometric detection but also for rapid visual sensing even by the naked eye. Moreover, the properties of the cis鈥?i>trans isomer of CN1 are examined. The Salen ligands have coordination chemistry similar to other well-known tetradentate porphyrin ligands as well as much easier preparation and rich photophysical properties.