College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044, China.
Chemphyschem. 2012 Apr 10;13(5):1313-24. doi: 10.1002/cphc.201100885. Epub 2012 Feb 16.
This paper presents experimental and theoretical investigations into excited-state intramolecular proton transfer (ESIPT) in new chromophores with hydroxyl and imino groups under one- and two-photon excitation. The results show that internal hydrogen bonding exhibits a remarkable influence on the maximum absorption wavelength of 2-[(4'-N,N-diethylaminodiphenylethylene-4-ylimino)methyl]phenol (C1) and 2-[(4'-methoxyl-diphenylethylene-4-ylimino)methyl]phenol (C3). Compounds C1 and C3 exhibit well-separated dual fluorescence emission bands under one- and two-photon excitation. The second fluorescence peaks of C1 and C3 are characterized by much larger Stokes shift than the first normal peaks (ca. 140 vs. 30 nm). 4-[(4'-N,N-Diethylaminodiphenylethylene-4-ylimino)methyl]phenol (C2) and 4-[(4'-methoxyldiphenylethylene-4-ylimino)methyl]phenol (C4) display single emission bands with small Stokes shifts (ca. 30 nm) in various solvents under one- and two-photon excitation. Furthermore, the first emission maxima of C1 and C3 are almost identical to the maximum fluorescence emission wavelengths of C2 and C4, respectively. These results show that C1 and C3 can undergo ESIPT via a reasonable six-membered ring, while there is no ESIPT in C2 and C4 under one- and two-photon excitation. Compounds C1 and C2 have larger two-photon absorption cross-sections under various near-infrared laser frequencies tuned from 700 to 880 nm. Molecular geometry optimization of the phototautomers (enol and keto) was performed to analyze the experimental results. The possibility of using these chromophores for metal ions as chemosensors of was thoroughly investigated. In DMF C3 exhibits excellent sensing responses to Zn(2+) and Fe(3+) ions through a greatly increased greatly and a largely reduced emission, respectively. In methanol disappearance of ESIPT emission with added Zn(2+) ions confirms its existence. The binding constants of C3 with Zn(2+) and Fe(3+) ions in DMF are also estimated.
本文对具有羟基和亚氨基的新型发色团在单光子和双光子激发下的激发态分子内质子转移（ESIPT）进行了实验和理论研究。结果表明，分子内氢键对 2-[(4'-N,N-二乙氨基二苯乙烯-4-基亚氨基)甲基]苯酚（C1）和 2-[(4'-甲氧基二苯乙烯-4-基亚氨基)甲基]苯酚（C3）的最大吸收波长有显著影响。在单光子和双光子激发下，C1 和 C3 表现出双峰荧光发射。C1 和 C3 的第二个荧光峰的斯托克斯位移比第一个正常峰大得多（约 140 对 30nm）。在单光子和双光子激发下，4-[(4'-N,N-二乙氨基二苯乙烯-4-基亚氨基)甲基]苯酚（C2）和 4-[(4'-甲氧基二苯乙烯-4-基亚氨基)甲基]苯酚（C4）在各种溶剂中表现出单发射带，斯托克斯位移较小（约 30nm）。此外，C1 和 C3 的第一个发射峰与 C2 和 C4 的最大荧光发射波长几乎相同。这些结果表明，C1 和 C3 可以通过合理的六元环发生 ESIPT，而在单光子和双光子激发下，C2 和 C4 则没有 ESIPT。在从 700nm 到 880nm 的各种近红外激光频率下，C1 和 C2 的双光子吸收截面较大。对光互变异构体（烯醇和酮）进行了分子几何优化，以分析实验结果。还彻底研究了这些发色团作为金属离子化学传感器的可能性。在 DMF 中，C3 对 Zn(2+)和 Fe(3+)离子表现出优异的传感响应，分别通过大大增加和大大减少发射来实现。在甲醇中，加入 Zn(2+)离子后 ESIPT 发射的消失证实了其存在。还估计了 C3 与 Zn(2+)和 Fe(3+)离子在 DMF 中的结合常数。
