【作者】 宋锋玲；

【导师】 彭孝军；

【作者基本信息】 大连理工大学 ， 应用化学， 2006， 博士

【摘要】 七甲川菁染料作为近红外荧光染料,由于能有效避开生物样品的自吸收和自发荧光所造成的背景干扰,近来常被用作生物体内的荧光标记物或制成荧光探针,成为研究热点。旨在提高它的稳定性和光谱性能而进行的分子结构改造或改进的研究工作一直很受关注。 本论文总结前人工作,以一个兼顾光稳定性和水溶性的七甲川吲哚菁染料为母体,对其中位氯原子进行取代,合成出一系列新型近红外菁染料。其中一类新染料在斯托克斯位移这一关键的光谱性能上取得突破,斯托克斯位移超过140nm,远远大于普通多甲川菁染料的25nm。 设计的母体染料在两端吲哚母核的N原子上各引入一个空间位阻大的苄基以期提高光稳定性。同时合成了一个两端N原子上引入乙基的染料作为对照。光稳定性实验证实新合成的母体染料有更好的光稳定性,证明了在吲哚环的N原子上引入苄基确实有提高光稳定性的效果。同时发现染料在水溶液中的光氧化速度明显比其它溶剂快。母体染料的合成以甲苯替代苯作为溶剂,实现在水中二次重结晶提纯,为后续工作奠定了基础。 在母体染料的中位用含-SH基团试剂亲核取代,衍生合成了四个中位硫取代衍生染料。发现这类衍生染料存在分子内光诱导电子转移(PET)现象。并且染料的PET效应与中位硫取代基团的供电能力直接相关。其中,一个取代基供电能力最强的染料表现出最有效的分子内PET,荧光量子产率最小。当这个染料取代基上的氨基被乙酰化或与重金属离子、质子结合,染料的荧光都会增强。这个结果有效验证了分子内PET的存在,并为设计基于这类染料的近红外荧光PET探针奠定基础。 将母体染料的中位氯原子用氨基试剂亲核取代,衍生合成了五个中位仲胺七甲川菁染料。发现这类衍生染料具有大的斯托克斯位移。其中,中位烷基氨基取代的三个衍生染料在水溶液中的斯托克斯位移大于140nm,并且荧光强度比普通菁染料强两倍以上。说明这类染料分子在激发态可能存在分子内电荷转移(ICT)现象。利用荧光粘度实验和质子化荧光滴定实验跟踪伴随ICT激发态产生时发生的分子构像变化,验证了ICT激发态的存在。 此外,论文还合成了两个中位叔胺七甲川菁染料染料,它们也具有大的斯托克斯位移,排除了染料分子发生激发态分子间质子转移的可能,进一步证明了ICT激发态的存在。 对中位衍生的新染料的光稳定性进行了深入的研究。根据中位硫、氮衍生染料的光稳定性研究结果,发现取代基的供电性能对光稳定性和荧光量子产率产生直接影响。更多还原

【Abstract】 Heptamethine cyanine dyes employed as fluorescence labels and sensors of biomolecules in vivo have attracted immense interest because their spectra reach the near-infrared (NIR) region, where a biological matrix exhibits the least absorption and autofluorescence background. Much research work has been carried out with the aim of improving their photostability and spectral properties.A new heptamethine indocyanine dye with good photostability and water-solubility was synthesized in this thesis. Then a series of derivative dyes were obtained by an apparent nucleophilic reaction at the central chlorine atom of the parent dye. The synthesis and spectral properties of these derivative dyes are the main part of the thesis. A great improvement in dyes’ Stokes shift (from 25 nm to 140 nm) is the most important innovation to the NIR heptamethine cyanine dyes.Two benzyl groups were introduced to the two N atoms at the two 3H-indo rings of the new heptamethine cyanine dye respectively. Compared with another dye with N-ethyl group, the new parent dye was found better photostability, which indicates that N-benzyl group can improve photostability for its rigid and bulk structure. In additional, it is found that dyes in water solutions are easier to photo-bleach than in alcohol solutions. A reasonable mechanism was proposed to explain the phenomenon. The reaction condition of the parent dye was improved by replacing benzene by toluene as the solvent. The parent dye was purified by recrystalling in water easily for derivative reactions.Four new dyes with thio group substitution in the central position were synthesized from the parent dye by nucleophilic substitution reaction. Photoinduced electron transfer (PET) was found to exist between the substituents and the fluorophore. Moreover, PET can be tuned by changing the electron-donating ability of the substituents. This effect is seldom seen for near-infrared fluorescent dyes. Among these derivative dyes, a dye with4-aminophenylthio-substitution exhibits the most efficient PET and the lowest fluorescence quantum yield. The acetylation, protonation or transition metal cation coordination of the amino group can recover fluorescence greatly via suppressing the PET. This result suggests that it is feasible to design MR fluorescence cation probe based on this kind of heptamethine cyanine dyes.Five derivative dyes from the parent dyes were obtained by similar nucleophilic substitution reaction in which five primary amines were employed as the nucleophilic reagent. Some particular spectral properties were found in the new dyes. Three of these dyes with alkyl secondary amino group at the central position were found to exhibit a large Stokes shift (>140 nm) and strong fluorescence. They were suggested to be a new paradigm for excited-state intramolecular charge transfer (ICT). The configuration change of the bridgehead amine accompanying ICT was investigated in different viscosity and pH media.To clarify the mechanism of the excited state of dyes with amino group, two more dyes in which alkyl tertiary amino replaces the chlorine atom were prepared from the parent dye. The two new dyes also possess a large Stokes shift, which can exclude one possible mechanism of excited-state intermolecular proton transfer.Finally, the photostabilities of these derivative dyes were investigated. Those dyes with good photostabilities were found to have poor fluorescence. It is attributed to the strong electron-donating ability of their substituents at the central position. An efficient PET may be easy to take place in those dyes, which make them photostable and no fluorescence at the same time.更多还原