Shiraishi Yasuhiro, Kohno Yoshiko, Hirai Takayuki
Research Center for Solar Energy Chemistry, and Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan.
J Phys Chem B. 2005 Oct 20;109(41):19139-47. doi: 10.1021/jp052645x.
A bis-azamacrocyclic anthracene (L2), which has two a 12-membered cyclic tetraamine (cyclen) connected through a 9,10-dimethylanthracene spacer, has been synthesized as a new fluorescent chemosensor for detection of pH and metal cations in aqueous solution (cyclen = 1,4,7,10-tetraazacyclododecane, L2 = 9,10-bis(1,4,7,10-tetraazacyclododecane-1-ylmethyl)anthracene). The fluorescence response of L2 has been studied in comparison to that of the previously reported monoazamacrocyclic anthracene (L1 = 1-(9-anthrylmethyl)-1,4,7,10-tetraazacyclododecane). Plots of the fluorescence intensity of L2 against pH demonstrate a sigmoidal curve with pKa 7.4, which is lower than that of L1 (8.3). Potentiometric titration reveals that the increase in the L2 fluorescence requires protonation of both cyclen rings, thus resulting in the lower pKa value. L2 demonstrates impressive fluorescence response against metal cations. At basic pH, upon addition of Zn2+ or Cd2+, L1 leads to an increase in the fluorescence intensity with a 1:1 metal-intensity response. L2, however, shows a 2:1 response to Zn2+, while showing a 1:1 response to Cd2+. At neutral pH, L1 fluorescence decreases upon addition of Zn2+ or Cd2+ because of a formation of metal-anthracene pi complex. L2, however, still demonstrates a Zn2+-induced increase in intensity with a 2:1 response, while no change in intensity is observed upon Cd2+ addition. The obtained findings suggest potential utilities of L2 as a new type fluorescent chemosensor for the detection of cations in aqueous solution.
一种双氮杂大环蒽（L2）已被合成出来，它是一种新型荧光化学传感器，用于检测水溶液中的pH值和金属阳离子。L2由两个通过9,10 - 二甲基蒽间隔基连接的12元环状四胺（环烯）组成（环烯 = 1,4,7,10 - 四氮杂环十二烷，L2 = 9,10 - 双（1,4,7,10 - 四氮杂环十二烷 - 1 - 基甲基）蒽）。与之前报道的单氮杂大环蒽（L1 = 1 - （9 - 蒽基甲基） - 1,4,7,10 - 四氮杂环十二烷）相比，对L2的荧光响应进行了研究。L2荧光强度相对于pH值的曲线呈现出pKa为7.4的S形曲线，这低于L1的pKa值（8.3）。电位滴定表明，L2荧光增强需要两个环烯环都质子化，因此导致较低的pKa值。L2对金属阳离子表现出令人印象深刻的荧光响应。在碱性pH值下，加入Zn2 + 或Cd2 + 时，L1的荧光强度会增加，呈现1:1的金属 - 强度响应。然而，L2对Zn2 + 表现出2:1的响应，而对Cd2 + 表现出1:1的响应。在中性pH值下，加入Zn2 + 或Cd2 + 时，L1的荧光会因形成金属 - 蒽π络合物而降低。然而，L2在加入Zn2 + 时仍表现出强度增加且为2:1的响应，而加入Cd2 + 时强度无变化。所得结果表明L2作为一种新型荧光化学传感器在检测水溶液中阳离子方面具有潜在用途。
