Effect of Solvent and Molecular Structure on the Enhanced Fluorescence and Supramolecular Chirality of Schiff Bases in Organogels

The structures and properties of some Schiff base compounds doped in organogels were investigated. It was found that although individual Schiff bases could not form organogels with organic solvents, they can gel by mixing with an organogelator, N,N′-bisoctadecyl-L-Boc-glutamic-diamide, which formed transparent organogels in dimethyl sulfoxide (DMSO) or toluene (Tol). The enhancement of doping Schiff bases fluorescence in the organogel was observed in comparison with that of the corresponding solution. Furthermore, in the DMSO organogel, the induced chirality was obtained from the doping Schiff base with long alkyl chain. In contrast, the Schiff bases without long alkyl chain could not form supramolecular chiral assemblies in organogel. It was suggested that through gel formation the chirality of the gelator could be transferred to the Schiff base through hydrophobic interaction among the long alkyl chains.     

溶剂和分子结构对席夫碱分子在有机凝胶中的荧光增强和超分子手性的影响

研究了在有机胶凝剂中掺杂的席夫碱化合物的结构和性质. 实验发现, 虽然席夫碱分子单独不能在有机溶剂中形成凝胶, 当其与一种胶凝剂N,N’-双十八烷基-L-Boc-谷氨酸混合时, 它们在二甲基亚砜或甲苯中形成透明的有机凝胶. 与相应的溶液相比, 观察到在有机凝胶中的荧光增强现象, 并且这一增强与席夫碱的结构有密切关系. 在二甲基亚砜的有机凝胶中, 观察到带有长烷基链的席夫碱具有诱导手性. 表明通过凝胶的形成, 胶凝剂的手性能传递到带有长链的席夫碱上.     

1,5-二芳基-3-(2-羟基-4,6-二甲氧基苯基)-2-吡唑啉的合成及氟离子荧光探针行为

设计合成了8个1,5-二芳基-3-(2-羟基-4,6-二甲氧基苯基)-2-吡唑啉化合物4a~4h. 它们的结构经由IR、1H NMR、MS和元素分析确认. 测定了它们的紫外光谱和荧光光谱, 研究了它们对氟离子的选择性识别作用, 发现化合物4a,4c和4d均可选择性地识别氟离子, 其中4a和4c作为识别氟离子的荧光探针, 受常见离子干扰较小, 选择性较高.     

Organogelation‐Controlled Topochemical [2+2] Cycloaddition and Morphological Changes: From Nanofiber to Peculiar Coaxial Hollow Toruloid‐Like Nanostructures

Novel amphiphilic molecules composed of naphthylacryl and L ‐glutamide moieties (1‐NA and 2‐NA) have been designed and their organogel formation in various organic solvents as well as their self‐assembled nanostructures have been investigated. Both compounds formed organogels in many organic solvents, ranging from nonpolar to polar, and self‐assembled into essentially nanofiber structures, although some twist or belt structures could be observed in certain solvents. A gel of compound 2‐NA in ethanol initially self‐assembled into nanofibers and then these were transformed into a family of coaxial hollow toruloid‐like (CHTL) nanostructures under irradiation, in which various toroids and disks of different sizes were stacked coaxially. We have established that a topochemical [2+2] cycloaddition in the organogel triggers this transformation. When the gel was fabricated into xerogels in which no ethanol remained, such morphological changes could not happen. This might be the first report of an organogel, in which both organized nanofibers and solvent coexist, controlling a topochemical reaction as well as the self‐assembled nanostructures formed. Due to the formation of the toruloid‐like nanostructures, the gel collapsed to a precipitate. However, upon heating this precipitate with ethanol, it redissolved and then formed a gel and self‐assembled into nanofibers once more. Thus, a reversible morphological transformation between nanofibers and an unprecedented series of toruloid‐like nanostructures can be induced by alternately heating and irradiating the gel.     

Highly fluorescent supramolecular gels with chirality transcription through hydrogen bonding

A highly fluorescent organogel with transparency was formed through a hydrogen (H)-bonding interaction between a non-fluorescent and achiral 2-(3',5'-bis-trifluoromethyl-biphenyl-4-yl)-3-(4-pyridin-4-yl-phenyl)-acrylonitrile (CN-TFMBPPE) monomer and chiral sergeant l-tartaric acid (TA) (or d-TA), with gel formation being accompanied by a drastic fluorescence enhancement as well as chirality induction.     

咪唑修饰萘酰亚胺与DNA的作用及其细胞毒性

设计合成了咪唑及其烷基化咪唑阳离子基团修饰的萘酰亚胺衍生物。利用紫外-可见吸收光谱、荧光光谱、圆二色谱和荧光共振能量转移等方法研究了它们与小牛胸腺DNA(CT DNA)和G-四链体DNA的相互作用。这些化合物对端粒DNA序列的G-四链体有很高的结合能力(K_α4×10~6 L·mol~(-1)),并能够稳定G-四链体。DNA粘度实验结果表明萘酰亚胺衍生物与CT DNA通过插入作用结合。Autodock分子对接模拟结果表明这些化合物通过疏水作用、静电作用或氢键等方式与人体端粒G-四链体的loop和沟槽部分结合。咪唑阳离子基团修饰的萘酰亚胺衍生物4a–c能够定位于细胞核,对肺癌细胞的细胞毒性要高于咪唑基团修饰的萘酰亚胺衍生物3。化合物4a和4b对肺癌细胞A549的细胞毒性明显高于正常人胚肺成纤维细胞MRC-5,表现出良好的抗癌活性。     

Gelation of a Highly Fluorescent Urea‐Containing Triarylmelamine Derivative: 2,4,6‐Tris(p‐N′‐Octadecylureido‐Anilino)Triazine in Organic Solvents

A new gelator of urea‐containing triazine derivatives was synthesized and tested in order to explore the gelation potential in different organic solvents. This compound has been found to form organogels with a variety of organic solvents such as decalin and other solvents. The resulting thermo‐reversible gel was characterized by using the dropping ball method and a number of other instruments. The melting temperature of the gel increased with the gel concentration. The intermolecular hydrogen bonding of gelation was demonstrated through an FT‐IR spectrometer. UV‐Vis and fluorescence analysis showed that the gel displayed various optical effects in different organic solvents. The blue fluorescence of the gel in decalin and the quenched effect of gel in CHCl³ were displayed, respectively. Morphological features in decalin and CHCl₃ were studied by applying atomic force microscopy (AFM), and the morphological features demonstrated that there were different aggregations in different solvents. In conductivity electrolyte experiments, the organogel electrolytes indicated high conductivity (σ) comparable to the corresponding NaClO₄/THF solution. The conductivity of gel electrolytes was increased with electrolyte salt.     

Amphiphilic Schiff base organogels: metal-ion-mediated chiral twists and chiral recognition

New amphiphilic gelators that contained both Schiff base and L-glutamide moieties, abbreviated as o-SLG and p-SLG, were synthesized and their self-assembly in various organic solvents in the absence and presence of metal ions was investigated. Gelation test revealed that o-SLG formed a thermotropic gel in many organic solvents, whilst p-SLG did not. When metal ions, such as Cu(2+), Zn(2+), Mg(2+), Ni(2+), were added, different behaviors were observed. The addition of Cu(2+) induced p-SLG to from an organogel. In the case of o-SLG, the addition of Cu(2+) and Mg(2+) ions maintained the gelating ability of the compound, whilst Zn(2+) and Ni(2+) ions destroyed the gel. In addition, the introduction of Cu(2+) ions caused the nanofiber gel to perform a chiral twist, whilst the Mg(2+) ions enhanced the fluorescence of the gel. More interestingly, the Mg(2+)-ion-mediated organogel showed differences in the fluorescence quenching by D- and L-tartaric acid, thus showing a chiral recognition ability.     

新型Cd(Ⅱ)-MOF的合成及对4-硝基苯胺的高效识别

采用新型1,3,5-三(1H-苯并[d]咪唑-2-基)苯(TBB)配体及2,5-二羟基对苯二甲酸(H₂dhtp)线性配体, 以Cd(Ⅱ)离子为中心节点, 构筑了具有新型拓扑结构(unj)的手性金属-有机框架材料[Cd(TBB)(dhtp) ](配合物1). 该配合物具有较强的光致发光性能, 可分散在溶液中荧光检测硝基配合物等污染物. 其中, 4-硝基苯胺对配合物1具有高效的荧光猝灭能力, 检测限可低至0.145 mg/L, 并具有较好的选择性.     

Pyrene-containing peptide-based fluorescent organogels: inclusion of graphene into the organogel

The N-terminally pyrene-conjugated oligopeptide, Py-Phe-Phe-Ala-OMe, (Py=pyrene 1-butyryl acyl) forms transparent, stable, supramolecular fluorescent organogels in various organic solvents. One of these organogels was thoroughly studied using various techniques including transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), Fourier-transform infrared (FTIR) spectroscopy, photoluminescence (PL) spectroscopy, and rheology. Unfunctionalized and non-oxidized graphene was successfully incorporated into this fluorescent organogel in o-dichlorobenzene (ODCB) to form a stable hybrid organogel. Graphene is well dispersed into the gel medium by using non-covalent π-π stacking interactions with the pyrene-conjugated gelator peptide. In the presence of graphene, the minimum gelation concentration (mgc) of the hybrid organogel was lowered significantly. This suggests that there is a favorable interaction between the graphene and the gelator peptide within the hybrid organogel system. This hybrid organogel was characterized using TEM, AFM, FTIR, PL, and rheological studies. The TEM study of graphene-containing hybrid organogel revealed the presence of both graphene sheets and entangled gel nanofibers. The AFM study indicated the presence of 3 to 4 layers in exfoliated graphene in ODCB and the presence of both graphene nanosheets and the network of gel nanofibers in the hybrid gel system. The rheological investigation suggested that the flow of the hybrid organogel had become more resistant towards the applied angular frequency upon the incorporation of graphene into the organogel. The hybrid gel is about seven times more rigid than that of the native gel.     

N,N-二(8-黄酮甲基)香叶胺类化合物的合成及生理活性

设计合成了4个N,N-二（8-黄酮甲基）香叶胺类化合物,所有目标化合物的结构均经1H NMR、MS和元素分析测试技术确证。采用MTT法考察了目标化合物对K562（白血病细胞）和SMMC7721（肝癌细胞）2种肿瘤细胞的体外抑制活性,结果表明,所测化合物对2种肿瘤细胞都有体外抑制活性,其中N,N-二(3′,4′-二甲氧基-8-黄酮甲基）香叶胺(1c)的活性最好,IC50值分别为5.78和3.85 μmol/L,N,N-二（4′-氟-8-黄酮甲基）香叶胺(1a)和化合物1c对K562（白血病细胞）的体外抑制活性明显优于商品药物美法仑(Melphalan)。以溴化乙锭(EB)为荧光探针测定了化合物1c与鲱魚精DNA有较强的相互作用。     

Carbazole-based organogel as a scaffold to construct energy transfer arrays with controllable fluorescence emission

A diaryldiketopyrrolopyrrole derivative functionalized with phenothiazine moieties (DPPP) was synthesized and introduced into the ordered 4-(3,6-di-tert-butyl-9H-carbazol-9-yl)benzamide (TBCB) organogel system. It was found that TBCB-based gel became a scaffold to make DPPP molecules line up along the gel fibers, resulting in new self-assembled arrays, whose XRD patterns were quite different from those of the neat TBCB gel and DPPP crystal. In the composite gel, the occurrence of a partial energy transfer from the excited light-harvesting antenna of TBCB to the DPPP acceptor was confirmed on the basis of time-dependent and time-resolved fluorescence investigations. Remarkably, the composite gel could emit intense red light or purplish white light by tuning the excitation wavelength. Such ordered soft materials with color-tunable emission may possess potential applications in sensor and photonic devices.     

Use of a self-assembling organogel as a reverse template in the preparation of imprinted porous polymer films

The concept of reverse templating of an organogel to form imprinted porous divinylbenzene polymer films with submicrometer channels is demonstrated. The organogel comprising a 1:1 molar ratio of two organogelators, that is, bis(2-ethylhexyl) sodium sulfosuccinate and 4-chlorophenol, was formed in divinylbenzene. The gel was cast as a thin film before UV polymerization of the solvent, and the organogelators were later removed by simple washing with water and isooctane. The integrity of the fiber bundles of the organogel was preserved during polymerization, and an exact hollow replica was obtained after the organogelators were leached away. It is easily possible to imprint gel fiber bundle structures into polymeric films through this technique. The gel can also be formed on macroporous substrates to yield supported thin porous polymeric films. With the incorporation of functional nanoparticles in AOT inverse micelles and hence the organogel, nanoparticle-containing porous polymer films exhibiting luminescence or magnetic properties are envisioned.     

A Synthetic Amino Acid Residue Containing A New Oligopeptide‐Based Photosensitive Fluorescent Organogel

A synthetic amino acid (with a stilbene residue in the main chain) containing a tripeptide‐based organogelator has been discovered. This peptide‐based synthetic molecule 1 self‐assembles in various organic solvents to form an organogel. The gel has been thoroughly characterized by using various microscopic techniques including field‐emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X‐ray diffraction (XRD), UV‐visible and fluorescence spectroscopy, and rheology. Morphological investigations using FESEM and AFM show a nanofibrillar network structure. Interestingly, the organogel is photoresponsive and a gel–sol transition occurred by irradiating the gel with UV light of 365 nm for 2 h as shown by the UV and fluorescence study. This photoresponsive fluorescent gel holds promise for new peptide‐based soft materials with interesting applications.     

8-（3-或4-氟苯甲酰基）-7-羟基-4-甲基香豆素的合成、晶体结构、抑菌活性、抗氧化活性及其与牛血清白蛋白的相互作用

设计并合成了两个新的氟代香豆素化合物8-（3-氟苯甲酰基）-7-羟基-4-甲基香豆素（3a）和8-（4-氟苯甲酰基）-7-羟基-4-甲基香豆素（3b）,其结构通过元素分析、IR和1HNMR进行了表征,通过X-射线单晶衍射测定了化合物3b的晶体结构,单晶结构分析表明,化合物3b的晶体属于单斜晶系.体外抑菌试验结果显示,目标化合物对大肠杆菌（E.coli）、枯草杆菌（B.subtilis）和金色葡萄球菌（S.aureus）有不同程度的抑制作用;体外抗氧化实验显示,目标化合物对超氧阴离子自由基（O2-·）和二苯代苦味肼基自由基（DPPH·）均有良好的清除能力;运用荧光光谱法研究了不同温度下目标化合物与牛血清白蛋白（BSA）的相互作用,结果表明,目标化合物对BSA的荧光猝灭均属于静态猝灭,相关热力学参数表明,化合物3a（H〈0,S〈0,G〈0）与BSA二者之间主要以氢键或范德华力相结合,化合物3b（H〉0,S〉0,G〈0）与BSA二者之间主要靠疏水作用力相结合;依据Fster＇s非辐射能量转移理论,求得BSA与化合物3a和化合物3b间的距离（r）分别为2.53和2.65nm,说明两个化合物与BSA之间可能发生了非辐射能量转移.     

新型4-羟基香豆素衍生物的微波合成及其光谱性质

以4-羟基香豆素(a)为原料微波辐射合成了具有独特的生理活性和荧光性能的3,3′,3″,3′″-亚乙四基-4-羟基香豆素(b)、3,3′-苯亚甲基-双-4-羟基香豆素(c)和4-羟基香豆素-1,4-萘醌(d)系列4-羟基香豆素衍生物, 采用元素分析、红外光谱、核磁共振及质谱表征了产物的结构, 并对其紫外-可见吸收光谱及荧光光谱性质进行了研究, 探索了化合物的微观结构与其光学性能之间的关系. 研究结果表明, 具有“近平面”、大π共轭和对称型结构的化合物b具有较大的摩尔吸光系数及强荧光特性, 且浓度在0.50~1.50×10^-4 mol/L范围时, 其荧光强度随着浓度的降低而呈线性增加; 在pH=1.81~6.09时, 荧光强度随pH降低而减弱, 在pH 8.36~11.98时, 荧光强度随pH升高而减弱. 此外, 牛血清白蛋白(BSA)及脱氧核糖核酸(DNA)可与该化合物发生相互作用, 进而敏化增强该分子的内源荧光.     

Reverse Thermal Organogelation of Poly(ethylene glycol)‐Polypeptide Diblock Copolymers in Chloroform

Most organogel formation has been observed at low temperatures and the gel melts as the temperature increases. As an opposite case to traditional organogels, we report a reverse thermal gelation of methoxy‐aminopoly(ethylene glycol)‐homopolypeptide block‐copolymer chloroform solutions that undergo a sol‐to‐gel transition as the temperature increases. A series of methoxy‐aminopoly(ethylene glycol)‐homopolypeptide block copolymers showing reverse thermal gelation in chloroform was synthesized and we prove that the secondary structure of the polypeptide determines the morphology of the organogel.

     

Enantioselective Esterification of 2-Methylpentanoic Acid Catalised via Immobilized Lipases in Chrysotile and Microemulsion-Based Gels

Immobilized lipases in chrysotile and microemulsion-based gel (MBG) or organogel were used in the resolution of racemic 2-methylpentanoic acid that is a valuable synthetic intermediate for the preparation of, among other compounds, a number of steriochemically pure insect pheromones.     

Amphiphilic Schiff Base Organogels: Metal‐Ion‐Mediated Chiral Twists and Chiral Recognition

New amphiphilic gelators that contained both Schiff base and L ‐glutamide moieties, abbreviated as o‐SLG and p‐SLG, were synthesized and their self‐assembly in various organic solvents in the absence and presence of metal ions was investigated. Gelation test revealed that o‐SLG formed a thermotropic gel in many organic solvents, whilst p‐SLG did not. When metal ions, such as Cu²⁺, Zn²⁺, Mg²⁺, Ni²⁺, were added, different behaviors were observed. The addition of Cu²⁺ induced p‐SLG to from an organogel. In the case of o‐SLG, the addition of Cu²⁺ and Mg²⁺ ions maintained the gelating ability of the compound, whilst Zn²⁺ and Ni²⁺ ions destroyed the gel. In addition, the introduction of Cu²⁺ ions caused the nanofiber gel to perform a chiral twist, whilst the Mg²⁺ ions enhanced the fluorescence of the gel. More interestingly, the Mg²⁺‐ion‐mediated organogel showed differences in the fluorescence quenching by D ‐ and L ‐tartaric acid, thus showing a chiral recognition ability.