激发态分子内质子转移分子2-羟基-1-萘甲醛半碳酰腙的光谱特性

Spectral Properties of (E)-1-[(2-Hydroxynaphthalen-1-yl)Methylene]Semicarbazide with Excited State Intramolecular Proton Transfer Characteristics

通过考察2-羟基-1-萘甲醛半碳酰腙(HNLSC)在不同极性溶剂中的吸收光谱和荧光光谱,详细研究了HNLSC分子在不同溶剂及酸、碱条件下的不同构型,证实了HNLSC具有典型的ESIPT特性。在非极性溶剂中分子主要以分子内氢键的闭式构型存在,这种闭式构型使分子具有ESIPT特性,在环己烷溶剂和高酸度极性溶剂中分子均表现出～415nm的正常荧光和～435nm处的反常ESIPT荧光。在极性质子溶剂中,因溶质和溶剂之间形成了分子间的氢键以及进一步去质子化,HNLSC形成了基态的溶剂化开式构型和离子构型,在吸收光谱中表现出～395nm的离子构型特征吸收。开式构型和离子构型阻断了分子内质子转移途径,因而在荧光光谱中仅表现出一个特征峰。实验进一步通过三乙胺和稀硫酸调节溶液体系的极性和酸度环境,证明在不同溶剂极性和酸度环境下,HNLSC分子不仅存在萘环上羟基变化引起的多种互变异构体间的转化平衡,同时存在—CHN—NH—CO—NH2结构域的烯醇式和酮式结构的相互转化。

Spectral properties of（E）-1-[（2-hydroxynaphthalen-1-yl）methylene] semicarbazide（HNLSC）have been investigated by means of absorption and fluorescence spectra in different solvents.By increasing concentration of acid and base in different solvents,its different configurations were studied,and found that HNLSC was a typical compound with excited state intramolecular proton transfer（ESIPT）.The molecule HNLSC exists mainly as the intramolecularly hydrogen bonded closed conformer in non-polar solvents,and shows ESIPT characteristics.Cyclohexane solvent and high acidity in the polar solvents HNLSC shows two bands at ～415nm and ～435nm,and found to be due to the normal fluorescence and the anomalistic ESIPT fluorescence respectively.In polarity proton solvents,there is a absorption band arises at 395 nm due to intermolecular hydrogen bonding between solute and solvent and the further deprotonation.Open conformer and the anion can block the intramolecular proton transfer channels,so fluorescence spectra of HNLSC in protonic solvent show only emission at ～447nm.Further experiments by TEA and diluted sulfuric acid solution system regulating the polarity and the acidity of the environment,confirms HNLSC molecules exist in a variety of conversion balances of tautomer,not only cause by the change in hydroxyl on the naphthalene ring,but also enol and keto＇s intertransform structures domain of —CHN—NH—CO—NH2.