Fluorescent and Electrochemical Sensing of Polyphosphate Nucleotides by Ferrocene Functionalised with Two ZnII(TACN)(pyrene) Complexes

The [Fc? bis{Zn^II(TACN)(Py)}] complex, comprising two Zn^II(TACN) ligands (Fc=ferrocene; Py=pyrene; TACN=1,4,7‐triazacyclononane) bearing fluorescent pyrene chromophores linked by an electrochemically active ferrocene molecule has been synthesised in high yield through a multistep procedure. In the absence of the polyphosphate guest molecules, very weak excimer emission was observed, indicating that the two pyrene‐bearing Zn^II(TACN) units are arranged in a trans‐like configuration with respect to the ferrocene bridging unit. Binding of a variety of polyphosphate anionic guests (PPi and nucleotides di‐ and triphosphate) promotes the interaction between pyrene units and results in an enhancement in excimer emission. Investigations of phosphate binding by ³¹P NMR spectroscopy, fluorescence and electrochemical techniques confirmed a 1:1 stoichiometry for the binding of PPi and nucleotide polyphosphate anions to the bis(Zn^II(TACN)) moiety of [Fc? bis{Zn^II(TACN)(Py)}] and indicated that binding induces a trans to cis configuration rearrangement of the bis(Zn^II(TACN)) complexes that is responsible for the enhancement of the pyrene excimer emission. Pyrophosphate was concluded to have the strongest affinity to [Fc? bis{Zn^II(TACN)(Py)}] among the anions tested based on a six‐fold fluorescence enhancement and 0.1 V negative shift in the potential of the ferrocene/ferrocenium couple. The binding constant for a variety of polyphosphate anions was determined from the change in the intensity of pyrene excimer emission with polyphosphate concentration, measured at 475 nm in CH₃CN/Tris‐HCl (1:9) buffer solution (10.0 mM , pH 7.4). These measurements confirmed that pyrophosphate binds more strongly (K_b=(4.45±0.41)×10⁶ M ^?1) than the other nucleotide di‐ and triphosphates (K_b=1–50×10⁵ M ^?1) tested.     

A Strategy for Dramatically Enhancing the Selectivity of Molecules Showing Aggregation‐Induced Emission towards Biomacromolecules with the Aid of Graphene Oxide

By intelligently utilizing the different interacting strengths between different moieties according to the displacement method, general biosensors with aggregation‐induced emission (AIE) characteristics for biomacromolecules without selectivity were converted to excellent, highly selective probes for one specific biomacromolecule with the aid of graphene oxide (GO) in an aqueous medium. Importantly, thanks to the different interactions between the AIE molecule and biomacromolecules, just by simply changing the AIE molecule the sensing system could detect different types of biomacromolecules, thereby providing a new approach to the development of AIE‐based sensors with high selectivity and sensitivity. More specifically, the complex of A₂HPS?HCl—a derivative of hexaphenylsilone (HPS) functionalized by two amino (A₂) groups (N(CH₂CH₃)₃)—and GO only gives an “off–on” response to DNA, with a detection limit of 2.3 μg mL^?1 toward DNA‐CT (calf thymus); interestingly, the complex of TPE‐N₂C₄ (1,2‐bis{4‐[4‐(N,N,N‐triethylammonium)butoxy]phenyl}‐1,2‐diphenylethene dibromide) and GO could only detect the presence of bovine serum albumin (BSA), whereas other biomacromolecules, including DNA, RNA, and even other proteins have very little influence.     

Tunable Aggregation-Induced Emission of Imidazole Hydrazones by pH and Anions

Aggregation-induced emission (AIE) materials have drawn great attention for applications as organic light-emitting diodes (OLED) and probes. The applications are, however, restricted by the complex syntheses and hydrophobic properties. Herein, a one-step synthesis of an AIE material based on imidazole hydrazone is assessed. Protonation of the imidazole-H leads to emission color change from yellow to green in the solid state. The emission color is recovered upon imidazole-H⁺ deprotonation. Moreover, the emission wavelength shifts from 532 to 572 nm by anion exchange. In addition, an enhanced emission (Φ_F up to 22.6 %) was obtained with the Br⁻ anion compared with NTf₂⁻, SbCl₅⁻, PF₆⁻, and OTf⁻ anions. X-ray crystallography studies together with theoretical calculations show that the enhanced emission of hydrazone salts arises from strong hydrogen bonding between the hydrazone proton and the halide ion (Cl⁻ or Br⁻).     

Ferrocene‐tagged ionic liquid stabilized on silica‐coated magnetic nanoparticles: Efficient catalyst for the synthesis of 2‐amino‐3‐cyano‐4H‐pyran derivatives under solvent‐free conditions

An advanced novel magnetic ionic liquid based on imidazolium tagged with ferrocene, a supported ionic liquid, is introduced as a recyclable heterogeneous catalyst. Catalytic activity of the novel nanocatalyst was investigated in one‐pot three‐component reactions of various aldehydes, malononitrile and 2‐naphthol for the facile synthesis of 2‐amino‐3‐cyano‐4H‐pyran derivatives under solvent‐free conditions without additional co‐catalyst or additive in air. For this purpose, we firstly synthesized and investigated 1‐(4‐ferrocenylbutyl)‐3‐methylimidazolium acetate, [FcBuMeIm][OAc], as a novel basic ferrocene‐tagged ionic liquid. This ferrocene‐tagged ionic liquid was then linked to silica‐coated nano‐Fe₃O₄ to afford a novel heterogeneous magnetic nanocatalyst, namely [Fe₃O₄@SiO₂@Im‐Fc][OAc]. The synthesized novel catalyst was characterized using ¹H NMR, ¹³C NMR, Fourier transform infrared and energy‐dispersive X‐ray spectroscopies, X‐ray diffraction, and transmission and field emission scanning electron microscopies. Combination of some unique characteristics of ferrocene and the supported ionic liquid developed the catalytic activity in a simple, efficient, green and eco‐friendly protocol. The catalyst could be reused several times without loss of activity.     

13C and1H NMR study of molecular motion in the deoxycholic acid-ferrocene solid inclusion compound

Using solid-state ¹³ C NMR spectroscopy and also measurements of proton spin-lattice relaxation times T ₁ and second moments M ₂ , we have investigated molecular motion in solid inclusion compounds of deoxycholic acid with ferrocene in the interval 100–400 K. We have identified various dynamic processes occurring with participation of molecules of the matrix and the included molecules. We have shown that in addition to rapid reorientations of the cyclopentadienyl rings, the ferrocene molecules undergo 180° jumps about the C ₂ axis. We have determined the parameters for all the molecular motions. We discuss the conformational state of the included molecules.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, Moscow 117813. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 586–593, March, 1992.     

Alkynylgold(I) C3-Chiral Concave Complexes: Aggregation and Luminescence

Chiral gold(I) acetylide trinuclear complexes 1 – 3 based on the cyclotribenzylene platform and terminal PR₃ ligands (R=Ph, Et, and Cy, respectively), were characterized and their light emission studied. They exhibited long-lived blue phosphorescence in CHCl₃ and a weak fluorescence in the UV. In MeOH/CHCl₃ mixtures of >1:1 volume ratio, 1 and 2 exhibited a new emission band at ca. 540 nm that developed at the expense of the UV emission. DLS studies demonstrated the presence of molecular aggregates of Ø 30–80 nm. The green emission observed in MeOH-rich solvent mixtures was therefore induced by aggregation, and could originate from Au⋅⋅⋅Au interactions. The AIE spectrum of 3 was observed only in solutions containing 99 % of MeOH, and correlated with its solid state emission. The AIE profiles of the enantiomers of 1 differed from that of rac- 1 , suggesting that the latter is a true racemate.     

一种含咔唑基团的混配型钌(II)配合物的合成、表征和酸碱性质研究

合成了钌(II)配合物cis-[Ru(HL)(Hdcbpy)(NCS)₂]^－•[N(C₄H₉)₄]^＋ (HL＝2-(9-乙基-9H-3-咔唑基)-1H-咪唑[4,5-f] [1,10]邻菲啰啉, H₂dcbpy＝4,4'-二羧酸-2,2'-联吡啶). 采用元素分析、核磁共振氢谱、红外光谱、紫外-可见吸收光谱、质谱(MS)对配合物进行了表征. 通过紫外-可见吸收光谱和稳态荧光光谱, 研究了该配合物的基态和激发态酸碱性质. 结果表明该配合物在基态时能发生5步质子化/去质子化反应, 表现出基于光致发光强度和激发态能量转移途径的质子化/去质子化诱导的分子开关性质.     

Solid State Confinement of Ferrocene by Calixarenes

Combinations of ferrocene with unsubstituted calix [n]arenes, n =4 and 5, in toluene afford crystalline inclusion complexes (calix[4]arene) ₃ (ferrocene) [hexagonal, a =14.7797(4), c =18.4400(4) Å, P6M₃/m , ρ = 1.389 g.cm ^?1 , Z =2, R ₁ =0.0963 (on 1401 observed data [ I >2 σ ( I )])] as a lattice-type inclusion complex, and (calix[5]arene)(toluene) _0.55 (ferrocene) _0.45 [monoclinic, a =9.6908(8), b =15.069(1), c =22.957(1) Å, β = 90.155(5)°, P2₁/m , ρ =1.318 g.cm ^?1 , Z =4, R ₁ =0.1005 (on 3130 observed data [ I >2 σ ( I )])], that shows endo -cavity complexation of ferrocene by the calixarene.     

Synthesis,X‐ray Structure of Ferrocene Bearing Bis(Zn‐cyclen) Complexes and the Selective Electrochemical Sensing of TpT

The new ligand, [Fc(cyclen)₂] ( 5 ) (Fc=ferrocene, cyclen=1,4,7,10‐tetraazacyclododecane), and corresponding Zn^II complex receptor, [Fc{Zn(cyclen)(CH₃OH)}₂](ClO₄)₄ ( 1 ), consisting of a ferrocene moiety bearing one Zn^II‐cyclen complex on each cyclopentadienyl ring, have been designed and prepared through a multi‐step synthesis. Significant shifts in the ¹H NMR signals of the ferrocenyl group, cf. ferrocene and a previously reported [Fc{Zn(cyclen)}]²⁺ derivative, indicated that the two Zn^II‐cyclen units in 1 significantly affect the electronic properties of the cyclopentadienyl rings. The X‐ray crystal structure shows that the two positively charged Zn^II‐cyclen complexes are arranged in a trans like configuration, with respect to the ferrocene bridging unit, presumably to minimise electrostatic repulsion. Both 5 and 1 can be oxidized in 1:4 CH₂Cl₂/CH₃CN and Tris‐HCl aqueous buffer solution under conditions of cyclic voltammetry to give a well defined ferrocene‐centred (Fc^0/+) process. Importantly, 1 is a highly selective electrochemical sensor of thymidilyl(3′‐5′)thymidine (TpT) relative to other nucleobases and nucleotides in Tris‐HCl buffer solution (pH 7.4). The electrochemical selectivity, detected as a shift in reversible potential of the Fc^0/+ component, is postulated to result from a change in the configuration of bis(Zn^II‐cyclen) units from a trans to a cis state. This is caused by the strong 1:1 binding of the two deprotonated thymine groups in TpT to different Zn^II centres of receptor 1 . UV‐visible spectrophotometric titrations confirmed the 1:1 stoichiometry for the 1 :TpT adduct and allowed the determination of the apparent formation constant of 0.89±0.10×10⁶ M ^?1 at pH 7.4.     

Spectral Characteristics of Bicalutamide Drug in Different Solvents and β-Cyclodextrin

Absorption and fluorescence spectra of bicalutamide (BCA) in different solvents and aqueous β-cyclodextrin (β-CD) solutions are reported. The solid inclusion complex of BCA with β-CD is prepared and investigated by FT-IR, ¹H NMR, differential scanning colorimetry (DSC) and scanning electron microscopy (SEM). The Stokes shift of BCA is correlated with various solvent polarity scales like E _T(30), BK and f(D,n). β-CD studies show that (i) the absorption and emission maxima of BCA are shifted to red, (ii) the absorbance is slightly decreased whereas emission intensity is increased largely with an increasing β-CD concentration, (iii) BCA forms 1:1 inclusion complex with β-CD and (iv) intramolecular charge transfer (ICT) emission is present in the excited state.     

Highly Luminescent Inks: Aggregation‐Induced Emission of Copper–Iodine Hybrid Clusters

Aggregation‐induced emission (AIE) is an attractive phenomenon in which materials display strong luminescence in the aggregated solid states rather than in the conventional dissolved molecular states. However, highly luminescent inks based on AIE are hard to be obtained because of the difficulty in finely controlling the crystallinity of AIE materials at nanoscale. Herein, we report the preparation of highly luminescent inks via oil‐in‐water microemulsion induced aggregation of Cu–I hybrid clusters based on the highly soluble copper iodide‐tris(3‐methylphenyl)phosphine (Cu₄I₄(P‐(m‐Tol)₃)₄) hybrid. Furthermore, we can synthesize a series of AIE inks with different light‐emission colors to cover the whole visible spectrum range via a facile ligand exchange processes. The assemblies of Cu–I hybrid clusters with AIE characteristics will pave the way to fabricate low‐cost highly luminescent inks.     

Synthesis, characterization and antitumor activity of 1,2-disubstituted ferrocenes and cyclodextrin inclusion complexes

Seven different ferrocene derivatives have been tested in vitro against Ehrlich ascites tumor cells. Neither ferrocene nor the monosubstituted derivative N,N-dimethylaminomethylferrocene showed cytotoxic activity (IC₅₀ > 1000 μM for 3 h treatments). Better results were obtained with 1,2-disubstituted derivatives. The IC₅₀ values ranged from 376.6 μM for 1,2-diformylferrocene to 71.2 μM for racemic 2-(N,N-dimethylaminomethyl)ferrocenecarboxamide. The latter derivative was also encapsulated in native β-cyclodextrin (CD), heptakis-2,3,6-tri-O-methyl-β-CD (TRIMEB) and 2-hydroxypropyl-β-CD (HPβCD) to give 1:1 (host:guest) inclusion compounds. The existence of true inclusion complexes in the solid state was confirmed by a combination of powder X-ray diffraction, thermogravimetric analysis, FTIR and ¹³C CP MAS NMR spectroscopy. The IC₅₀ value for the β-CD inclusion compound was identical to that obtained for the nonincluded ferrocene derivative. By contrast, the inclusion compounds comprising TRIMEB and HPβCD yielded IC₅₀ values of 25.2 and 20.0 μM, respectively. No obvious relationship could be established between the redox behavior of the compounds determined by cyclic voltammetry and the biochemical data.     

Luminescent core–shell nanoparticles with crosslinked aggregation-induced emission core structures: Emission both in solution and solid states

Luminescent core–shell nanoparticles (NPs) with crosslinked aggregation-induced emission (AIE) core structures, which exhibited excellent emission independent of the dispersion state of the NPs, have been developed by a facile one-pot method based on the self-assembly of an amphiphilic block copolymer poly(PEGMA)-b-poly(DB3VT). Core–shell micelles with a poly(DB3VT) core were formed from poly(PEGMA)-b-poly(DB3VT) in tetrahydrofuran (THF)/H₂O condition, and the crosslinked AIE-based structure was selectively incorporated into the core by the Suzuki coupling reaction between poly(DB3VT) blocks and tetraphenylethylene (TPE)-based coupling monomers at the same time. This method afforded a uniform NP with a crosslinked TPE-based AIE core structure. The obtained NP exhibited excellent emission both in diluted solution and solid states. This result indicated that the formed TPE-based AIE core structure was always aggregated regardless of NP dispersion owing to the crosslinking as we expected. The crosslinked TPE-based AIE core structure, which was related to the emission property, was readily tuned by the selection and combination of coupling monomers in the Suzuki coupling reaction. By incorporating electron-deficient units into the core, the emission color could be successfully tuned from yellow-green to orange and red while maintaining the emission property independent of the state of the NP dispersion. These results demonstrated that NPs with the crosslinked AIE core structures are a promising luminescent material design motif to realize emission independent on molecular dispersion.     

Remote Effect from Boron Cluster: Tunable Photophysical Properties of o-Carborane-Based Luminogens

We proposed a new molecular design strategy that the o-carboranyl group is attached as “an innocent unit” to the remote side of luminogens to tune photophysical properties. To verify this strategy, two o-carborane-based compounds with asymmetric molecular geometry were designed and synthesized. Photophysical properties of o-carborane-based luminogens were investigated on the basis of UV-Vis spectra, photoluminescence spectra, crystal structure analysis and theoretical calculations. The results indicate that the o-carboranyl group has a slight effect on the energy gap between the ground state (S₀) and the first excited state (S₁) in the solution state but a significant effect on the energy gap between S₀ and S₁ in the solid state. Besides, the radiative and non-radiative transition processes are modulated by the o-carboranyl unit. This leads to emission quenching in the solution state but an enhanced luminous efficiency in the aggregate state with a typical aggregation-induced emission (AIE) property.     

A novel Hg2+ fluorescence sensor TPE-TSC based on aggregation-induced emission

Abstract

A fluorescent sensor TPE-TSC with aggregation induced emission (AIE) characteristic is synthesized for detecting Hg²⁺ by attaching thiosemicarbazide (TSC) unit into tetraphenylethylene (TPE) group. TPE-TSC exhibits intense green emission in DMSO/H₂O (V:V?=?1:9) solution with the formation of the aggregation. TPE-TSC shows outstanding fluorescence quenching toward Hg²⁺ over other metal ions due to the formation of complex TPE-TSC/Hg²⁺ with a 2:1 binding ratio. The detection limit of TPE-TSC for Hg²⁺ is 1?×?10^?5 mol·L^?1.     

Synthesis and characterization of fluorescence active G4-quartet and direct evaluation of self-assembly impact on emission

Fluorescence (FL) active 8-aryl guanosine derivatives were prepared and applied for cation mediated self-assembly to form the H-bonded G₈-quadruplexes. The p-cyano (p-CN) and 8-anthracene (8-An) substituted guanosines were identified to give the strongest fluorescence with the formation of G₈-octamers (G₈) both in solution (NMR) and solid state (X-ray). This well-defined G₈-octamer system has provided the first direct evidence on the self-assembled G-quadruplex fluorescence emission with aggregation-induced emission (AIE), which could be applied as the foundation for FL molecular probe design toward G-quadruplex recognition.     

Multifunctional AuI-based AIEgens: Manipulating Molecular Structures and Boosting Specific Cancer Cell Imaging and Theranostics

Gold(I) N-heterocyclic carbene (Au^I-NHC) complexes have emerged as potential anticancer agents owing to their high cytotoxicity and stability. Integration of their above unique functions with customized aggregation-induced emission (AIE) luminogens to achieve specific bioimaging and efficient theranostics to cancer is highly desirable but is rarely studied. Now, a series of novel Au^I-NHC compounds were developed with AIE characteristics. A complex with a PPh₃ ligand was selected out as it could achieve both prominent specific imaging of various cancer cells and efficient inhibition of their growth with negligible toxic effects on normal cells due to the targeting binding and strong inhibition towards thioredoxin reductase. This complex could also act as a powerful radiosensitizer to boost the anticancer efficacy with performance superior to that of popularly used auranofin. It holds great potential as a specific and effective theranostic drug in cancer diagnosis and precise therapy.     

Insight into the strong aggregation-induced emission of low-conjugated racemic C6-unsubstituted tetrahydropyrimidines through crystal-structure–property relationship of polymorphs

Racemic C6-unsubstituted tetrahydropyrimidines (THPs) are a series of fluorophores with a strong aggregation-induced emission (AIE) effect. However, they do not possess the structural features of conventional AIE compounds. In order to understand their AIE mechanism, here, the influences of the molecular packing mode and the conformation on the optical properties of THPs were investigated using seven crystalline polymorphs of three THPs (1–3). The racemic THPs 1–3 have low-conjugated and highly flexible molecular structures, and hence show practically no emission in different organic solvents. However, the fluorescence quantum yields of their polymorphs are up to 93%, and the maximum excitation (λ _ex) and emission (λ _em) wavelengths of the polymorphs are long at 409 and 484 nm, respectively. Single-crystal structures and theoretical calculation of the HOMOs and LUMOs based on the molecular conformations of these polymorphs indicate that the polymorphs with the shortest λ _ex and λ _em values possess a RS-packing mode (R- and S-enantiomers self-assemble as paired anti-parallel lines) and a more twisted conformation without through-space conjugation between the dicarboxylates, but the polymorphs with longer λ _ex and λ _em values adopt a RR/SS-packing mode (R- and S-enantiomers self-assemble as unpaired zigzag lines) and a less twisted conformation with through-space conjugation between the dicarboxylates. The molecular conformations of 1–3 in all these polymorphs are stereo and more twisted than those in solution. Although 1–3 are poorly conjugated, the radiative rate constants (k _r) of their polymorphs are as large as conventional fluorophores (0.41–1.03 × 10⁸ s^–1) because of improved electronic conjugation by both through-bond and through-space interactions. Based on the obtained results, it can be deduced that the strong AIE arises not only from the restriction of intramolecular motion but also from enhanced electronic coupling and radiatively-favored inter-crossed local excitation (LE) and intramolecular charge transfer (ICT) excitation states. The abnormal molecular structures, easily-controllable self-assembly of the R- and S-enantiomers, and the strong AIE effect make THPs very useful fluorophores for applications and theoretical research.     

Coordination‐Driven Self‐Assembly of Carbazole‐Based Metallodendrimers with Generation‐Dependent Aggregation‐Induced Emission Behavior

A new family of 120° carbazole‐based dendritic donors D1 – D3 have been successfully designed and synthesized, from which a series of novel supramolecular carbazole‐based metallodendrimers with well‐defined shapes and sizes were successfully prepared by [2+2] and [3+3] coordination‐driven self‐assembly. The structures of newly designed rhomboidal and hexagonal metallodendrimers were characterized by multinuclear NMR (¹H and ³¹P) spectroscopy, ESI‐TOF mass spectrometry, FTIR spectroscopy, and the PM6 semiempirical molecular orbital method. The fluorescence emission behavior of ligands D1 – D3 , rhomboidal metallodendrimers R1 – R3 , and hexagonal metallodendrimers H1 – H3 in mixtures of dichloromethane and n‐hexane with different n‐hexane fractions were investigated. The results indicated that D1 – D3 featured typical aggregation‐induced emission (AIE) properties. However, different from ligands D1 – D3 , metallodendrimers R1 – R3 and H1 – H3 presented interesting generation‐dependent AIE properties. Furthermore, evidence for the aggregation of these metallodendrimers was confirmed by a detailed investigation of dynamic light‐scattering, Tyndall effect, and SEM. This research not only provides a highly efficient strategy for constructing carbazole‐based dendrimers with well‐defined shapes and sizes, but also presents a new family of carbazole‐based dendritic ligands and rhomboidal and hexagonal metallodendrimers with interesting AIE properties.     

Excimer emission of caffeine with α- and β-cyclodextrins: spectral and molecular modelling studies

Excimer emission of caffeine with α-CD and β-CD were studied by UV-visible, fluorescence, time-resolved fluorescence, FTIR, ¹H NMR and molecular modelling techniques. Changes in the absorbance and fluorescence and lifetime of the caffeine with cyclodextrin (CD) solutions indicate (i) caffeine shows dual emission in the CD solutions, (ii) normal emission originates from a monomer and the longer wavelength emission is due to excimer and (iii) in both CDs caffeine forms 1:2 inclusion complex. Carbonyl stretching frequency moved to higher wave numbers and broadening of the N–H stretching band indicated the formation of inclusion complex. The resonance of the methyl protons of caffeine show remarkable upfield or downfield shift in the ¹H NMR, which indicates imidazole ring of the caffeine entrapped in the CD cavities. Investigations of energetic, thermodynamic and electronic properties of PM3 computational calculations confirmed the stability of the inclusion complex.