9,10-二(苯亚甲基-硫亚甲基)蒽的合成及其对Cu2+的识别

荧光分子开关和分子识别是超分子化学的重要组成部分。蒽环作为一个优良的荧光基团被广泛应用于分子开关的设计及分子识别中。Resorci-narenes母体衍生物的合成研究中采用蒽环作为荧光基团已被报道多次[1-4],Luigi Fabbrizzi合成的多氨基蒽衍生物[5]对Zn2 具有良好的PET效应。蒽系荧光分子在分子逻辑门系统中日益受到了研究者的重视,de Silva等在研究中发现一蒽环化合物[6]在Mg2 作用存在OR逻辑行为。在后续研究中发现两类蒽环化合物在一定条件下分别存在AND[7]和NOR[8]逻辑行为。在分子识别的研究中,Shin-ichi Sasaki合成的含穴状…     

分子基逻辑材料*

在适当的条件下分子开关将输入的信息转换为输出信号,利用这一特点,可在分子体系根据二进位布尔逻辑规则实现信号转换。目前,用化学体系进行基本的布尔逻辑功能执行 (PASS、YES、NOT、AND、NAND、OR、NOR、XNOR和INH)都已成为可能。在此基础上,逻辑门的整合与编程,以及更进一步的复杂分子运算开始受到人们的关注。迄今为止,以高灵敏性的荧光输出信号为主,人们在分子水平上设计实现了多种复杂的逻辑电路,包括组合逻辑电路和时序逻辑电路等,并开始涉及信息处理的安全平台设计。本文主要介绍了近年来利用分子荧光开关体系模拟数字逻辑电路过程中所取得的最新进展,对分子逻辑电路研究的热点和问题进行了展望。     

基于N-(9-蒽甲基)-L-组氨酸的NOR荧光逻辑门

合成了一个新的组氨酸衍生物, N-(9-蒽甲基)-L-组氨酸(1), 并对其进行了元素分析、电喷雾电离质谱(ESI-MS)、核磁共振氢谱(1H-NMR)和碳谱(13C-NMR)等波谱表征. 考查了pH值及15种不同金属离子对其荧光强度的影响. 实验结果表明, 中性水溶液条件下, Zn2+和Cd2+能使体系荧光增强, 而Pb2+、Co2+、Hg2+、Ni2+和Cu2+等则使体系荧光有不同程度的猝灭.其中, Cu2+和Ni2+猝灭能力最强, 它们与化合物1均形成了物质的量比为1:2的配合物, 络合常数分别为2.88×10⁶和1.12×10⁶ L2·mol-2. Cu2+和Ni2+对化合物1的荧光猝灭为静态猝灭过程. 在此基础上, 以Cu2+和Ni2+作为两个输入信号, 以蒽的特征荧光发射作为输出信号, 构建了一个NOR荧光分子逻辑门.     

基于双控荧光开关的NOR和OR分子逻辑门

合成了L-精氨酸蒽衍生物1, 考察了碱土及过渡金属离子对主体分子1荧光光谱的影响, 结果发现, 在中性水溶液条件下只有Cu2＋能有效地猝灭其荧光. 另外, 通过OH－/H＋和Cu2＋/乙二胺四乙酸(EDTA)均能对化合物1的荧光强度进行可逆性调控. 在此基础上, 我们以化合物1水溶液作为起始状态, 以OH－和Cu2＋为两化学输入, 构建了一个“或非”(NOR)分子逻辑门; 以1-Cu2＋水溶液体系作为起始状态, 以H＋和EDTA为两化学输入, 构建了一个“或”(OR)分子逻辑门.     

用于监控过氧化氮的近红外荧光探针的光物理性质及PET机理

含有机硒的七甲川菁染料是基于光诱导电子转移(PET)的近红外(IR)荧光探针, 能在生理条件下高灵敏、高选择性地监控过氧化氮. 本文应用含时密度泛函理论(TD-DFT)计算方法研究其光物理性质和PET机理.结果表明, 在激发态, 荧光母体发生最高占有分子轨道(HOMO)到最低非占有分子轨道(LUMO)的电子跃迁, 识别基团上的HOMO轨道能级提高到荧光母体的单电子占据的HOMO轨道能级之上, 并向其转移一个电子, 使激发态电子回落过程受阻而导致荧光部分淬灭. 硒被氧化后, 识别基团上的HOMO轨道能级降低, PET过程被阻断, 荧光发射恢复. 研究进一步证明, PET效应来自于识别基团上苯胺N原子的p电子, 它的电子转移能力受到其对位苯硒基的氧化-还原状态的影响, 产生了荧光信号的“开-关”作用.     

电子给体-电子受体体系的合成及分子内光致电荷转移反应的研究

论文中设计,合成了以9,10-二甲氧基蒽(DMA)为电子给体,双酚A(BA)为连接体,连接不同的电子受体(对苯甲酸乙酯,对腈基苯,2,4-二氧苯,对硝基苯,蒽醌AQ,2,4-二硝基苯)的六种二元分子,测定了它们的氧化还原电位,吸收光谱,荧光光谱,荧光寿命等。研究了它们的分子内光致电子转移过程,研究了它们的分子内光致电子转移反应自由能的变化△G与电子转移速率常数K_q的关系。     

分子识别中质子客体的荧光传感和开关研究进展

分子识别是超分子化学的核心概念 ,而荧光开关PET体系又是分子识别中的重要组成部分 ,是超分子化学和光物理学科相结合的成就 ,作为一种全新的客体识别分析手段由于其独特的应用价值 ,近十年以惊人的速度在向前发展。本文综合 1 998年以前的文献对质子客体的荧光开关PET体系进行了全面介绍。     

基于光化学探针的分子键盘锁研究进展

分子键盘锁作为一类新型的分子逻辑器件,其信号输出依赖于特定顺序的信号输入组合,可以在分子水平上保护信息。光化学探针分子以其选择性好、灵敏度高、易于实现在线分析以及可通过目视比色识别和原位检测等特点成为目前研究的热点。本文介绍了基于光化学分子探针发展起来的分子键盘锁,根据信号输入类型主要有阳离子输入、阴离子输入和阳离子/阴离子混合输入等类型。最后,展望了分子键盘锁的发展趋势。     

异构的蒽乙烯单钌配合物:合成与表征、电化学、光谱性质及理论计算

通过9-蒽乙炔基及2-蒽乙炔基分别与有机金属氢化物羰基氯氢三(三苯基膦)钌(Ⅱ)[Ru HCl(CO)(PPh_3)_3]反应,再使用三甲基膦(PMe_3)交换配体,合成并表征了具有同分异构结构的蒽乙烯单钌配合物1和2,其中配合物2的结构还经X射线单晶衍射的确证,结合理论计算研究了其电学及光学性质。密度泛函理论(DFT)优化配合物1和2的电子结构显示,在两个异构体中钌乙烯基与蒽配体呈现明显不同的构型,前线分子轨道图显示最高已占分子轨道(HOMO)上电子离域于整个分子骨架,其中以配体蒽乙烯基所占比例为90%,表明蒽乙烯基配体参与该配合物氧化进程的比例很大。电化学实验结果表明,配合物1的氧化还原可逆性明显低于配合物2。配合物1和2及前体分子1b和2b的电子吸收光谱结果表明,配合物与前体分子相比光谱性质呈现明显变化,其在紫外区域的强吸收峰明显减弱,而在长波长方向均出现了弱而宽的吸收峰,该吸收峰已经通过含时密度泛函理论(TDDFT)计算将其归属于π→π*以及金属配位电荷转移(MLCT)跃迁吸收,均来自于HOMO→LUMO跃迁产生。荧光发射光谱揭示金属配位之后其荧光强度和荧光量子产率明显降低。CCDC:1488284,2。     

识别金属离子客体的荧光传感开关的研究进展

分子识别是超分子化学的核心概念,荧光开关PET(photoinduced electron transfer)体系又是分子识别中的重要组成部分,是超分子化学与光化学学科相结合的成就.荧光开关作为一种全新的客体识别和分析手段,由于其独特的应用价值,近10年来正以惊人的速度在向前发展.     

Photoinduced electron transfer (PET) based Zn2+ fluorescent probe: transformation of turn-on sensors into ratiometric ones with dual emission in acetonitrile

Ratiometric sensors for the detection of metal ions have gained increasing attention due to its self-calibration tendency for the environmental effects. In this context, we have synthesized and characterized a dual emitting ratiometric Zn(2+) probe (1) having acridinedione as a fluorophore and N,N-bis(2-pyridylmethyl)amine (BPA) as a receptor unit. Existence of two different conformation of the molecule with photoinduced electron transfer (PET) from amine moiety to the acridinedione fluorophore leads to dual emission, namely locally excited (425 nm) and anomalous charge transfer emission (560 nm) in aprotic solvents. In the presence of one equivalent of Zn(2+), a 15-fold fluorescence enhancement in the locally excited state together with the quenching of charge transfer emission is observed. The intensity changes at the two emission peaks allow a ratiometric detection of Zn(2+) under PET signaling mechanism. The utilization of PET process for the ratiometric fluorescence change will further signify the importance of PET mechanism in sensing action. Addition of Zn(2+) to 1 in acetonitrile/water mixtures shows a single emission peak with fluorescence enhancement.     

Chiral donor photoinduced-electron-transfer (d-PET) boronic acid chemosensors for the selective recognition of tartaric acids, disaccharides, and ginsenosides

A modular approach was proposed for the preparation of chiral fluorescent molecular sensors, in which the fluorophore, scaffold, and chirogenic center can be connected by ethynyl groups, and these modules can easily be changed to other structures to optimize the molecular sensing performance of the sensors. This modular strategy to assembly chiral sensors alleviated the previous restrictions of chiral boronic acid sensors, for which the chirogenic center, fluorophore, and scaffold were integrated, thus it was difficult to optimize the molecular structures by chemical modifications. We demonstrated the potential of our new strategy by the preparation of a sensor with a larger scaffold. The photoinduced electron‐transfer (PET) effect is efficient even with a large distance between the N atom and the fluorophore core. Furthermore, the rarely reported donor‐PET (d‐PET) effect, which was previously limited to carbazole, was extended to phenothiazine fluorophore. The contrast ratio, that is, PET efficiency of the new d‐PET sensor, is increased to 8.0, compared to 2.0 with the previous carbazole d‐PET sensors. Furthermore, the ethynylated phenothiazine shows longer excitation wavelength (centered at 380 nm) and emission wavelength (492 nm), a large Stokes shift (142 nm), and high fluorescence quantum yield in aqueous solution (Φ=0.48 in MeOH/water, 3:1 v/v). Enantioselective recognition of tartaric acid was achieved with the new d‐PET boronic acid sensors. The enantioselectivity is up to 10 (ratio of the binding constants toward D ‐ and L ‐tartaric acid, k_D/k_L). A consecutive fluorescence enhancement/decrease was observed, thus we propose a transition of the binding stoichiometry from 1:1 to 1:2 as the analyte concentration increases, which is supported by mass spectra analysis. The boronic acid sensors were used for selective and sensitive recognition of disaccharides and glycosylated steroids (ginsenosides).     

Enzyme-free and DNA-based universal platform for the construction of various logic devices based on graphene oxide and G-quadruplex

In the fields of biocomputing and biomolecular, DNA molecules are applicable to be regarded as data of logical computing platform that uses elaborate logic gates to perform a variety of tasks. Graphene oxide (GO) is a type of novel nanomaterial, which brings new research focus to materials science and biosensors due to its special selectivity and excellent quenching ability. G-quadruplex as a unique DNA structure stimulates the intelligent application of DNA assembly on the strength of its exceptional binding activity. In this paper, we report a universal logic device assisted with GO and G-quadruplex under an enzyme-free condition. Integrated with the quenching ability of GO to the TAMRA (fluorophore, Carboxytetramethylrhodamine) and the enhancement of fluorescence intensity produced by the peculiar binding of G-quadruplex to the NMM (N-methylmesoporphyrin IX), a series of basic binary logic gates (AND. OR. INHIBIT. XOR) have been designed and verified through biological experiments. Given the modularity and programmability of this strategy, two advanced logic gates (half adder and half subtractor) were realized on the basis of the same work platform. The fluorescence signals generated from different input combinations possessed satisfactory results, which provided proof of feasibility. We believe that the proposed universal logical platform that operates at the nanoscale is expected to be utilized for future applications in molecular computing as well as disease diagnosis.     

A Cu protein cavity mimicking fluorescent chemosensor for selective Cu recognition: tuning of fluorescence quenching to enhancement through spatial placement of anthracene unit

Four new fluoroionophores possessing four ligating sites (2S+2N) and an essential hydrophobic environment, as prevailing in the plastocyanin and rusticyanin proteins, have been synthesized. In these PET fluoroionophores, the position of fluorophore anthracene moiety effectively modulates the Cu²⁺ induced emission properties (quenching vs enhancement) of the fluorophore. The addition of Cu²⁺ to solution of receptor with anthracene moiety in its center caused quenching in emission intensity through photoinduced fluorophore-to-metal electron transfer mechanism and in cases where anthracene is present at terminus nitrogen, the emission intensities increased by nearly 1000% due to inhibition of the photoinduced electron transfer from receptor-to-fluorophore in the presence of Cu²⁺ ions. The hydrophobic environment created by various aromatic rings clearly manifested the stability of fluorescence of these molecules above pH 2.0 and their Cu²⁺ complexes above pH 4. The application of such fluoroionophores has been elaborated for building OR and AND logic gates.     

Bright molecules with sense, logic, numeracy and utility

Using cartoons as an organizational aid, we illustrate how the 'fluorophore-spacer-receptor' format of fluorescent PET (photoinduced electron transfer) sensors and switches can be logically extended in many different directions. These include emissive sensors for various chemical species and properties, and exploit various kinds of emission. Common sensing issues such as dynamic range, internal referencing, selectivity, mapping and space resolution are addressed. The sensory output function is also developed into more complex forms, molecular logic/computation being one such example. Molecular logic leads to molecular arithmetic. Real-life applications to physiological monitoring, medical diagnostics and molecular computational identification of small objects are included.     

Coumarin-strapped calix[4]pyrrole: a fluorogenic anion receptor modulated by cation and anion binding

A new strapped calix[4]pyrrole containing a fluorophore as part of the strap has been synthesized and characterized. Association constants with various anions have been determined using both fluorescence titration and isothermal titrations calorimetry (ITC). The two sets of association constants were found to be in good agreement with one another. The fluorescence emission properties of this new receptor could be controlled by addition of Na+ (or H2O) and anions. However, the fluorescence quenching by anions is only observed in the presence of Na+ (or H2O). All the experimental evidence is consistent with the notion that independent PET processes are modulated by separate cation and anion recognition events. As such, this system operates as an elementary logic gate wherein anion and cation concentrations serve as the input and fluorescence intensity changes provide the output.     

Fluorescent Molecular Logic Gates and Pourbaix Sensors in Polyacrylamide Hydrogels

Polyacrylamide hydrogels formed by free radical polymerisation were formed by entrapping anthracene and 4-amino-1,8-naphthalimide fluorescent logic gates based on photoinduced electron transfer (PET) and/or internal charge transfer (ICT). The non-covalent immobilisation of the molecules in the hydrogels resulted in semi-solid YES, NOT, and AND logic gates. Two molecular AND gates, examples of Pourbaix sensors, were tested in acidic aqueous methanol with ammonium persulfate, a strong oxidant, and displayed greater fluorescence quantum yields than previously reported. The logic hydrogels were exposed to aqueous solutions with chemical inputs, and the fluorescence output response was viewed under 365 nm UV light. All of the molecular logic gates diffuse out of the hydrogels to some extent when placed in solution, particularly those with secondary basic amines. The study exemplifies an effort of taking molecular logic gates from homogeneous solutions into the realm of solid-solution environments. We demonstrate the use of Pourbaix sensors as pE-pH indicators for monitoring oxidative and acidic conditions, notably for excess ammonium persulfate, a reagent used in the polymerisation of SDS-polyacrylamide gels.     

A dual role of phenylboronic acid as a receptor for carbohydrates as well as a quencher for neighboring pyrene fluorophore

A simple amino acid based compound (1) containing a phenyl boronic group and pyrene fluorophore showed an enhanced fluorescence in aqueous solutions at physiological pH through suppression of the photoinduced electron transfer from pyrene to boronic acid on carbohydrate binding. The compound exhibited an interesting fluorescence change depending on pH with decreased emission intensity at acidic pH but enhanced emission intensity at basic pH unlike the fluorescent carbohydrate chemosensors using a PET process with amine and aryl-boronic acid. We have characterized a dual role of phenylboronic acid as a receptor for carbohydrates as well as a quencher for the fluorescence of pyrene fluorophore.     

Theoretical study of the photophysical processes of a styryl-bodipy derivative eliciting an AND molecular logic gate response

We study, via density functional theory and time dependent DFT calculations, the photophysical processes of a styryl-bodipy derivative, which acts as a three metal-cation-receptor fluorophore in order to (a) gain information on the appropriate computational approach for successful prediction of molecular logic gate candidates, (b) rationalize the available experimental data and (c) understand how the given combination of three different receptors with the BODIPY fluorophore presents such interesting optoelectronic responses. The fluorophore ( 1 ), its monometallic complexes ( 1-Ca ²⁺ , 1-Zn ²⁺ , and 1-Hg ²⁺ ), and its trimetallic complex ( 2 ) are studied. The calculated λ_max values for absorption and emission are in excellent agreement with experimental data. It was found that the observed quenching of emission of 1 and of the monometallic complexes is attributed to the fact that their first excited state is a charge-transfer state whereas this does not happen for the complex 2 . It should be noted that for the correct ordering of the excited states, the inclusion of corrections to the excitation energies for nonequilibrium solvent effects is required; while in the case of 1-Ca ²⁺ , the additional explicit inclusion of the solvent is necessary for the quenching of the emission spectra.