【作者】 陆欣宇；

【导师】 朱为宏；

【作者基本信息】 华东理工大学 ， 应用化学， 2011， 博士

【摘要】 基于分子识别的光化学探针和自组装是超分子化学研究领域的两个重要发展分支。光化学探针具备灵敏度高和选择性好等优点,同时提供了方便、快捷和廉价的分析检测金属离子等物种的手段,因此在环境化学、分析化学和生物医学等领域深受重视。目前,大部分荧光化学探针在生物应用中主要障碍是其较短的发射波长,易受自发荧光或背景荧光干扰,并对活体组织或生物体存在光毒性,而当发射波长延伸到近红外区,将显著削弱这些因素的不利影响。因此,开发近红外长波长的新型荧光染料和荧光探针,对于生物体内或体外检测具有很高的应用价值。与发展相当成熟的键合型探针相比,基于不可逆化学反应的反应型探针具有检测对象专一、吸收光谱和颜色多变(肉眼易于识别)的特点,因此近年来此类探针受到越来越多的关注。此外,超分子自组装是微观领域“积小为大”合成途径的关键。小分子通过氢键、π-π堆积等非共价作用可以自发组织形成形态优美的更大尺寸的纳米结构。特别是手性小分子构筑单元的精确设计,这对实现超分子螺旋形貌必不可少。本论文首先创新性地合成了一系列萘四酰亚胺类长波长荧光染料,随后设计合成了基于这类新型萘四酰亚胺和花酰亚胺类染料的近红外荧光探针和反应型汞离子探针,并进一步研究了以花酰亚胺为构筑单元的手性可控自组装行为。第一章择要介绍了光化学探针的基本原理,并对近红外荧光探针、反应型汞离子探针和具有螺旋结构的超分子自组装的重要进展进行综述；提出本论文的研究内容。第二章通过杂环胺类对二溴萘四酰亚胺(DBI)的亲核反应,设计合成了8个未见报道的基于萘四酰亚胺母体(NDIs)的新型单取代或双取代荧光染料,其结构均得到了很好的表征。系统性光谱研究表明,胺类的推电子作用差异可以很好地调控这些化合物的吸收和荧光,使之成为一类性能良好的可见或近红外荧光染料(最大吸收：509～580nm；最大发射：565～638 nm；荧光量子效率：0.21～0.54；斯托克斯位移：36～77 nm),这对长波长荧光染料的扩充和应用很有意义。第三章设计、合成了两个母体结构新颖的近红外荧光增强型锌离子探针PND和PNT。其设计思想是以哌啶取代的萘四酰亚胺作为近红外荧光团,研究发现由于配体DPEA和TPEA的结构差异,导致离子探针PND和PNT的荧光机制发生明显的差异,即PND主要遵循光诱导电子转移(PET)机制,而PNT则是分子内光电荷转移(ICT)为主导机制。PND与锌离子以三配位形式结合,吸收与荧光光谱位移基本不变,但荧光增强约4倍,属于典型的PET特征。相比之下,PNT与锌离子以更稳定的五配位形式结合,吸收与荧光均明显蓝移,具有明显的ICT现象。由于配位模式差异,PND对锌离子的选择性优于PNT,而PNT敏感性则优于PND。分别实现了PND和PNT对KB活细胞内锌离子的荧光成像,表明两个探针都具有很好的膜渗透性和低毒性。这是首例基于萘四酰亚胺荧光染料的近红外光化学探针,对发展母体结构新颖的近红外探针具有重要意义。第四章巧妙地利用萘四酰亚胺母体推拉电子变化易于调控其光谱的特点,创新地设计、合成了三个母体结构新颖、含不同硫脲反应基团的比色型汞离子化学探针(PN1、PN2和PN3),发现其中含有给电子苯基硫脲反应基团的PNl对汞离子识别过程最快。PN1和PN3与Hg2+作用后,颜色均从蓝色变为酒红色(其最大吸收波长分别产生25和44nm的蓝移),完全适合肉眼比色识别,其对汞离子的比色检测限达5μM。此外,采用PN3制作了快速定性检测试纸,可检测出水中浓度低至10μM的汞离子。这对发展母体结构新颖的反应型探针及其在环境监测等方面的应用有着重要的意义。第五章发现一种醋酸汞促1,3-二取代硫脲的N-乙酰化反应。机理研究表明,反应先后经历脱硫形成碳二亚胺中间体及其N-乙酰化重排的过程。据此巧妙地设计了以花酰亚胺为荧光团,苯基硫脲衍生物为反应基团的荧光增强型汞离子探针P3。在醋酸根辅助下,P3仅对Hg2+表现出荧光增强,有效克服了Ag+和Cu2+等亲硫原子的干扰,这对发展反应新颖、具有良好选择性和敏感性的反应型探针很有意义。第六章已报道的花酰亚胺氢键自组装多基于N-H...O作用,因此设计、合成了8个花酰亚胺母体含有不同取代基,亚胺部分引入手性羧酸(酯)基团的花酰亚胺类化合物,独辟蹊径地研究了基于O-H...O作用的花酰亚胺氢键自组装过程。螺旋形花酰亚胺超分子结构则多基于分子间堆积作用构建,巧妙地将对甲酚引入花酰亚胺母体以克服分子间π-π堆积作用,使之通过分子间羧酸氢键作用实现了新颖的超分子螺旋形结构,并进一步通过核磁氢和CD谱得到验证。通过改变温度、浓度和溶剂极性等参数能够可逆或者破坏性地调控超分子螺旋的自组装过程。螺旋方向可以通过花酰亚胺中的氨基酸残基调控,也就是说,L-或D-型光学异构可以分别诱导构筑单元形成P-(右手)或M-(左手)方向的螺旋。有趣的是,AFM图片显示其还能在HOPG的表面聚集形成空心圆球形态。更多还原

【Abstract】 Based on the molecular recognition principles, optial chemosensors and self-assembly have become two important branches of supramolecular chemistry. Optial chemosensors are highly valuable in a variety of fields such as environmental chemistry, analytic chemistry and bio-medicinal science because they can provide accurate, on-line, and low-cost detection of toxic heavy metal ions with high selectivity and sensitivity. Unfortunately, the main application problems with most biolocal fluorescent sensors are short emission wavelength strongly disturbed by the auto-and/or background-fluorescence and harmful to the living tissues and biomass. Since the remarkable near-infrared (NIR) emission can eliminate the influence of above-mentioned disadvantages, the exploiture of NIR biological dyes and NIR fluorescent chemosensors has been of great value for both in vitro and in vivo biological applications.Compared to the relatively well-developed coordination-based chemosensors, irreversible-chemical-reaction-based chemodosimeters have recently emerged as a research area of significant importance due to its highly analyte-specific property and providing signaling changes in both the absorption wavelength and color, which can be detected by the naked eye. Furthermore, supramolecular self-assembly is one of the key techniques for the "bottom-up" approach in nanotechnology, by which small molecules from well-defined larger nanostructures via multiple non-covalent intermolecular forces, including hydrogen-bonding,π-πstaking and so on. In particular, the precise control of chiral building blocks is essential to supramolecular helical performance.The aim of this thesis is to develop new fluorescent chemosensors and chemodosimeters based on novel naphthalene diimide (NDI) and perylene bisimides (PBI) dyes. Additionally, perylene-bisimide-based self-assemblies are also discussed.In Chapter 1, the major sensing principles of optical chemosensors are introduced, and the progress in NIR fluorescent chemosensors, chemodosimeters for Hg2+, and supramolecular helical self-assemblies is reviewed.In Chapter 2, eight highly colored and photoluminescent mono-or di-core-substituted naphthalene diimide (NDIs) have been rationally designed and synthesized from 2,6-dibromonaphthalene diimide (DBI) by means of a stepwise nucleophilic substitution of two bromine atoms by heterocyclic secondary amines, which have been characterized by a wide range of spectroscopic methods. Electronic absorption and fluorescence studies revealed that the amine substituents with different electron-donating abilities leads to the NDIs with tuneable absorption and emission properties, falling in the preferable region to NIR (λabsmax: 509～580 nm;λemmax:565～638 nm;ΦF:0.21～0.54; Stokes shift:36～77nm).In Chapter 3, two novel NIR fluorescent "turn-on" chemosensors (PND and PNT) for Zn2+ based on NDI fluorophore have been designed, synthesized and optimized as well. Our strategy was to choose NDI as a novel NIR fluorophore, and DPEA or TPEA as the receptor, respectively, so as to improve the selectivity to Zn2+. In the case of PND, The nearly 4-fold fluorescence enhancement and the negligible shift in absorption and emission spectra of PND with Zn2+ titration are dominated with a typical photoinduced electron-transfer (PET) process, resulting in the formation of a three-coordinate Zn2+-PND complex. In contrast, the distinct blueshift in both absorbance and fluorescence is indicative of a combination of PET and ICT processes, giving a more stable five-coordinate Zn2+-PNT complex. Due to the differential binding mode caused by the ligand effect, PND shows excellent selectivity to Zn2+ over other metal ions but lower sensitivity when compared with PNT. Also both PND and PNT were successfully used to image intracellular Zn2+ ions in the living KB cells, indicating high cell-permeability and low toxicity. To our best knowledge, this is the first report of NIR cation chemosensors based on NDI as fluorophore, which may be helpful to tailor NDI as reporter groups to be specific for the other NIR cation chemosensors.In Chapter 4, three novel NDI derivatives (PN1, PN2 and PN3) with different isothiocyanate substituents as dosimeter units via the specific Hg2+ -induced desulfurization have been synthesized for developing colorimetric chemodosimeters to Hg+. The distinct response is dependent on the electron-donating effect of isothiocyanate substituents, that is, the stronger in the electron-donating capability of isothiocyanate substituents, the faster in the Hg2+ -promoted cyclization. Both PN1 and PN3 with Hg2+ exhibit color changes from blue to wine-red (with blue shifts of 25 and 44nm in absorption, respectively), fully meeting "naked-eye" colorimetric changes with a detection limit of 5μM. In addition, PN3 also successfully developed as Hg2+ test kits with a discernible concentration of 10μM.Chapter 5 describes an unprecedented Hg(OAc)2-induced N-acetylation of 1,3-disubstituted thioureas, involving the intermediate of carbodiimide. Accroding to the mechanism of Hg(OAc)2-induced N-acetylation of 1,3-disubstituted thioureas, a novel chemosensor P3 based on perylenebisimide (PBI) as signaling moiety and thiourea as reactive moiety has been designed and synthesized as a turn-on fluorescent chemodosimeter towards highly sensitivity and selectivity for Hg2+ among common metal ions, in an acetate aqueous medium.Little attention has been paid to the O-H...O hydrogen bonding interactions in the PBI system although the conventional hydrogen bonding in carboxylic acids is particularly strong in solutions, on surface and in crystal with high sensitivity to various environmental factors. In Chapter 6, our motivation is focused on borrowing the help of O-H...O hydrogen bonding interactions to realize the control in chiral self-assembly. For this purpose, we construct the target chiral a-amino acid system based on PBI system with the following considerations:i) to obtain PBIs bearing the self-assembly unit of carboxylic groups, chiral a-amino acid is an obviously good choice to the building block with an easy imidation to incorporate carboxylic groups and retain the original chiral center of amino acid; ii) incorporating the substitute of 4-methylphenoxy to their bay-region at PBI to prevent the competitive H- or J-aggregation during the interaction process of hydrogen bonding; iii) attempting to realize helical arrangement via the chiral center control with two exact enantiomers of L- and D-phenylalanine. The combination of optical, 1H NMR and CD spectra allows the observation of chirality-controlled helical superstructure in a self-assembled perylene bisimide system via intermolecular hydrogen-bonding. Interestingly, the chiral carboxylic acid-functionalized PBI systems are found to be spontaneously self-assembled into supramolecular helices, which are strongly dependent upon several factors, such as solvent polarity, concentration and temperature. Moreover, the supramolecular helical chirality can be well controlled by the chiral amino acid residues in PBI system, that is, the assembled clockwise (Plus, P) or anticlockwise (Minus,M) helices can be induced by L-or D-isomers, respectively, which also further assemble into hollow nanospheres in the solid state (AFM study).更多还原