State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093, China.
J Phys Chem A. 2009 Dec 24;113(51):14081-6. doi: 10.1021/jp907331q.
A boron-dipyrromethene (BODIPY)-based fluorescence probe with a N,N'-(pyridine-2, 6-diylbis(methylene))-dianiline substituent (1) has been prepared by condensation of 2,6-pyridinedicarboxaldehyde with 8-(4-amino)-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene and reduction by NaBH(4). The sensing properties of compound 1 toward various metal ions are investigated via fluorometric titration in methanol, which show highly selective fluorescent turn-on response in the presence of Hg(2+) over the other metal ions, such as Li(+), Na(+), K(+), Ca(2+), Mg(2+), Pb(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Ag(+), and Mn(2+). Computational approach has been carried out to investigate the mechanism why compound 1 provides different fluorescent signal for Hg(2+) and other ions. Theoretic calculations of the energy levels show that the quenching of the bright green fluorescence of boradiazaindacene fluorophore is due to the reductive photoinduced electron transfer (PET) from the aniline subunit to the excited state of BODIPY fluorophore. In metal complexes, the frontier molecular orbital energy levels changes greatly. Binding Zn(2+) or Cd(2+) ion leads to significant decreasing of both the HOMO and LUMO energy levels of the receptor, thus inhibit the reductive PET process, whereas an oxidative PET from the excited state fluorophore to the receptor occurs, vice versa, which also quenches the fluorescence. However, for 1-Hg(2+) complex, both the reductive and oxidative PETs are prohibited; therefore, strong fluorescence emission from the fluorophore can be observed experimentally. The agreement of the experimental results and theoretic calculations suggests that our calculation method can be applicable as guidance for the design of new chemosensors for other metal ions.
一种基于硼二吡咯甲川（BODIPY）的荧光探针，具有 N，N' - （吡啶-2,6-二基双（亚甲基））-二苯胺取代基（1），通过 2,6-吡啶二甲醛与 8-（4-氨基）-4,4-二氟-1,3,5,7-四甲基-4-硼-3a,4a-二氮杂-s-茚并和由 NaBH(4)还原缩合而成。通过甲醇中的荧光滴定研究了化合物 1 对各种金属离子的传感性质，结果表明，在存在 Hg(2+)的情况下，它对其他金属离子（如 Li(+)、Na(+)、K(+)、Ca(2+)、Mg(2+)、Pb(2+)、Fe(2+)、Co(2+)、Ni(2+)、Cu(2+)、Zn(2+)、Cd(2+)、Ag(+)和 Mn(2+)）具有高度选择性的荧光开启响应。还进行了计算方法研究，以探讨化合物 1 对 Hg(2+)和其他离子提供不同荧光信号的原因。能级的理论计算表明，硼二吡咯甲川荧光团的亮绿色荧光猝灭是由于苯胺基团到 BODIPY 荧光团激发态的还原光致电子转移（PET）。在金属配合物中，前线分子轨道能级发生了很大的变化。结合 Zn(2+)或 Cd(2+)离子会导致受体的 HOMO 和 LUMO 能级显著降低，从而抑制还原 PET 过程，而从激发态荧光团到受体的氧化 PET 发生，反之亦然，这也会猝灭荧光。然而，对于 1-Hg(2+)配合物，还原和氧化 PET 都被禁止；因此，实验上可以观察到荧光团的强荧光发射。实验结果与理论计算的一致性表明，我们的计算方法可以作为设计其他金属离子新型化学传感器的指导。
