摘要/Abstract
通过Suzuki反应、胺醛缩合两步反应合成了开链的枝状的含联苯胺基片段的有机染料分子.利用核磁氢谱和碳谱、红外光谱、高分辨质谱和元素分析等手段表征了产物的分子结构，结合X-ray单晶结构分析、核磁氢谱分析、紫外-可见吸收光谱的系统研究发现，目标分子C1和C3存在分子间氢键作用.荧光发射光谱证实了只有目标分子C3能在非质子性溶剂中发生激发态分子间质子转移（Excited-state Intermolecular Proton Transfer，ESPT）反应，且随着溶液浓度的增大，C3发生ESPT反应的能力增强.在固态下同样可以发生ESPT反应.
关键词: 氢键, 质子转移, 有机生色团, 激发态, 荧光发射光谱
In this paper, the intermediates 2'-hydroxybiphenyl-2-amine (I1) and 2'-methoxybiphenyl-2-amine (I2) were first synthetized via Suzuki reaction of 2-bromoaniline and arylboronic acid under 80℃. Meanwhile, organic dyes benzidine fragments ((E)-2'-(2-nitrobenzylideneamino)-biphenyl-3-ol (C1) and (E)-2'-(2,4-dinitrobenzylideneamino)-biphenyl-3-ol (C3)) which could undergo intermolecular proton transfer in excited states were synthetized via aminoaldehyde condensation of the intermediates biphenyl-2-amine and corresponding aldehyde. In addition, the dyes without proton transfer segments ((E)-2'-methoxy-N-(2-nitrobenzylidene)biphenyl-3-amine (C2) and (E)-2'-methoxy-N-(2,4-dinitrobenzylidene)biphenyl-3-amine (C4)) were also synthesized to act as references for comparisons experiment. The chemical structures of organic dyes were characterized by nuclear magnetic resonance (NMR) spectra, infrared spectra (IR), high resolution mass spectrometry (HR-MS) as well as elemental analysis. The analysis of X-ray single crystal diffraction and H NMR spectra suggest the presence of internal hydrogen bond with different strength in the target dyes C1 and C3. It indicated that the type of substituents has an effect on the chemical shift of hydroxyl groups, with the electron-withdrawing ability of substituents increases, the hydroxyl shift to higher field. Then the UV/visible spectra also confirm that the target dyes have intermolecular hydrogen bond, while there is no intermolecular hydrogen bond in the reference dyes C2 and C4. The excited-state intermolecular proton transfer (ESPT) properties of the organic dyes were further studied by fluorescence emission spectroscopy. It was found that target dye C3 could occur excited state intermolecular proton transfer (ESPT) via intermolecular hydrogen bonding in non-protonic solvents. In contrast, ESPT properties cannot be processed through hydrogen-bonding interaction of the studied target dye C1 no matter in protonic solvents, non-protonic solvents or in solid state. The target dye C1 and reference dyes (C2 and C4) only show the normal fluorescence emission peaks. It was worth mentioning that with the increasing concentration of C3 in solution, the ESPT reaction ability could be enhanced. Meanwhile, C3 can also occurs ESPT in solid state.
Key words: hydrogen bond, proton transfer, organic chromophore, excited-state, fluorescence emission spectroscopy
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