Pyrene Moieties Research Articles

Simple and Rapid Endotoxin Recognition Using a Dipicolylamine-Modified Fluorescent Probe with Picomolar-Order Sensitivity.

Endotoxin is a lipopolysaccharide (LPS) that is found in the outer membrane of the cell wall of Gram-negative bacteria. Due to its high toxicity, the allowable endotoxin limit for water for injection is set at a very low value. Conventional methods for endotoxin detection are time-consuming and expensive and have low reproducibility. A previous study has shown that dipicolylamine (dpa)-modified pyrene-based probes exhibit fluorescence enhancement in response to LPS; however, the application of such probes to the sensing of LPS is not discussed. Against this backdrop, we have developed a simple and rapid endotoxin detection method using a dpa-modified pyrenyl probe having a zinc(II) center (Zn-dpa-C4Py). When LPS was added into Zn-dpa-C4Py solution, excimer emission of the pyrene moiety emerged at 470 nm. This probe can detect picomolar concentrations of LPS (limit of detection = 41 pM). The high sensitivity of the probe is ascribed to the electrostatic and hydrophobic interactions between the probe and LPS, which result in the dimer formation of the pyrene moieties. We also found that Zn-dpa-C4Py has the highest selectivity for LPS compared with other phosphate derivatives, which is probably caused by the co-aggregation of the probe with LPS. We propose that Zn-dpa-C4Py is a promising chemical sensor for the detection of endotoxin in medical and pharmaceutical applications.

Noncovalent functionalization of carbon nanotubes as a scaffold for tissue engineering

Tissue engineering is one of the hot topics in recent research that needs special requirements. It depends on the development of scaffolds that allow tissue formation with certain characteristics, carbon nanotubes (CNTs)-collagen composite attracted the attention of the researchers with this respect. However, CNTs suffer from low water dispersibility, which hampered their utilization. Therefore, we aim to functionalize CNTs non-covalently with pyrene moiety using an appropriate hydrophilic linker derivatized from polyethylene glycol (PEG) terminated with hydroxyl or carboxyl group to disperse them in water. The functionalization of the CNTs is successfully confirmed by TEM, absorption spectroscopy, TGA, and zeta potential analysis. 3T3 cells-based engineered connective tissues (ECTs) are generated with different concentrations of the functionalized CNTs (f-CNTs). These tissues show a significant enhancement in electrical conductivity at a concentration of 0.025%, however, the cell viability is reduced by about 10 to 20%. All ECTs containing f-CNTs show a significant reduction in tissue fibrosis and matrix porosity relative to the control tissues. Taken together, the developed constructs show great potential for further in vivo studies as engineered tissue.

Multi-dentate chelation induces fluorescence enhancement of pyrene moiety for highly selective detection of Fe(III).

Fluorescence enhancement has great advantages and various promising applications for a fluorescent molecular probe, which shows high sensitivity and high selectivity. In this report, a novel pyrene-based fluorescent probe with multidentate ligand (PPD) was synthesized for highly selective detection of Fe(III), which exhibited great fluorescence enhancement response upon the addition of Fe(III) in aqueous solution of pH 3.5 ~ 7.5, with a detection limit of 115nM. The probe also has good water solubility and photostability. Further fluorescence titration confirmed 1:1 stoichiometric ratio for the probe PPD-Fe(III), which can be applied for quantification of Fe(III). The probe was validated for ferric detection in real water samples by spike and recovery test.

A Fluorescence Study on Guest Release of Reduction-responsive Host-guest Conjugates Having a Disulfide Bond

Reduction-responsive and anionic cyclophane (1) having a fluorescent pyrene moiety with a cleavable disulfide linkage was synthesized as a host-guest conjugate covalently bound with both host (cyclophane) and guest (pyrene) components. Reduction of the disulfide bond of 1 by glutathione gave its reduced forms (thiolates) of cyclophane and released pyrene derivatives that led to a significant fluorescence response in an aqueous carbonate buffer. The fluorescence intensity originating from monomer emission of 1 considerably decreased, accompanying increase of excimer emission due to self-aggregation of the resulting amphiphilic thiolate of pyrene derivative.

The positional effect of arylamines on pyrene core in a blue fluorescent dopant significantly affecting the performance of organic light emitting diodes

New blue fluorescent dopant materials based on pyrene moieties were synthesized by variation of the positions of N-phenylnaphthalene-1-amine functional groups to minutely control the molecular geometry and photophysical properties. A blue dopant with the functional groups at the 1, 6 position exhibited the highest photoluminescence quantum yield. 3,8-Diisopropyl-N1,N6-di(naphthalen-1-yl)-N1,N6-diphenylpyrene-1,6-diamine (DI-1,6-DAP) exhibited the best performances with a current efficiency of up to 6.89 cd/A and external quantum efficiency of 5.45% among the new synthetic dopants prepared in this study. In terms of color purity, the case of substituting arylamine groups at the 1,7 position of the pyrene core unit [N1,N7-di(naphthalen-1-yl)-N1,N7-diphenylpyrene-1,7-diamine (1,7-DAP)] was superior to the case of attaching them at the 1,6 position of the same core unit [N1,N6-di(naphthalen-1-yl)-N1,N6-diphenylpyrene-1,6-diamine (1,6-DAP)] (y < 0.098).

The New Di-Gold Metallotweezer Based on an Alkynylpyridine System.

We developed a simple method to prepare one gold-based metallotweezer with two planar Au-pyrene-NHC arms bound by a 2,6-bis(3-ethynyl-5-tert-butylphenyl)pyridine unit. This metallotweezer is able to bind a series of polycyclic aromatic hydrocarbons through the π-stacking interactions between the polyaromatic guests and the pyrene moieties of the NHC ligands. The metallotweezer was also used as a host for the encapsulation of planar metal complexes, such as the Au(III) complex [Au(C^N^C)(C≡CC6H4-OCH3-p)], for which there is a large binding constant of 946 M−1.

Exploration of nonlinear optical enhancement and interesting optical behavior with pyrene moiety as the conjugated donor and efficient modification in acceptor moieties

Herein, a series of new pyrene based hexylcyanoacetate derivatives (HPPC1–HPPC8) with A–π–D–π–D configuration were designed by end-capped modeling of non-fullerene acceptors on the structure of reference compound named dihexyl 3,3'-(pyrene-1,6-diylbis(4,1-phenylene))(2E,2'E)-bis(2-cyanoacrylate) HPPCR. Quantum chemical calculations of HPPCR and HPPC1–HPPC8 were accomplished at M06/6-31G(d, p) level. The stability of molecules due to the strongest hyper conjugative interactions in HPPCR and HPPC1–HPPC8 was estimated through NBO study. Interestingly, HOMO–LUMO band-gap of HPPC1–HPPC8 was found smaller than HPPCR which resulted in large NLO response. Among all the investigated compounds, HPPC7 showed the larger NLO response due to the presence of four cyanide (CN) groups which strengthens the bridge conjugation, and its band gap was found to be 2.11 eV, smaller as compared to band gap of HPPCR (3.225 eV). The absorption spectra of HPPC1–HPPC8 compounds showed maximum absorption wavelengths (483–707 nm) than HPPCR (471.764 nm). The designed compounds showed high NLO response than HPPCR. Amazingly, highest amplitude of linear polarizability < α > , first hyperpolarizability (βtotal) and second hyperpolarizability < γ > for HPPC7 were achieved to be 1331.191, 200,112.2 and 4.131 × 107 (a.u), respectively. NLO response showed that the HPPC1–HPPC8 might be potential candidates for NLO applications.Graphical abstract

Host–Guest Complexation‐Induced Aggregation Based on Pyrene‐Modified Cyclodextrins for Improved Electronic Circular Dichroism and Circularly Polarized Luminescence

AbstractSeveral γ‐cyclodextrin (CD) derivatives mono‐ or di‐substituted by pyrenes at the primary rim of the CD were demonstrated to aggregate into nano‐strips in aqueous solutions, with the pyrene moieties interpenetrating into γ‐CD cavities. The hydrophobic complexation‐induced aggregation provides a rigid chiral environment for the pyrenes and leads to significant electronic circular dichroism (ECD) and circularly polarized luminescence (CPL) activities, giving unprecedently highgabsandglumvalues up to 4.3×10−2and 5.3×10−2, respectively. The aggregates lead to excimer emission with high quantum yields and showBCPLandBiCPLup to 338. 6 M−1 cm−1and 169.3 M−1 cm−1, respectively.

Host-Guest Complexation-Induced Aggregation Based on Pyrene-Modified Cyclodextrins for Improved Electronic Circular Dichroism and Circularly Polarized Luminescence.

Several γ-cyclodextrin (CD) derivatives mono- or di-substituted by pyrenes at the primary rim of the CD were demonstrated to aggregate into nano-strips in aqueous solutions, with the pyrene moieties interpenetrating into γ-CD cavities. The hydrophobic complexation-induced aggregation provides a rigid chiral environment for the pyrenes and leads to significant electronic circular dichroism (ECD) and circularly polarized luminescence (CPL) activities, giving unprecedently high gabs and glum values up to 4.3×10-2 and 5.3×10-2 , respectively. The aggregates lead to excimer emission with high quantum yields and show BCPL and BiCPL up to 338. 6 M-1 cm-1 and 169.3 M-1 cm-1 , respectively.

Spectroscopic, computational and mechanistic studies on regio- and stereoselectivity of the 1,3-dipolar cycloaddition reaction in the synthesis of dispiro[indoline-3,2′-pyrrolidine-3′,3"-indolines] festooned with pyrene moiety

• Novel polyheterocyclic pyrene-grafted dispiro-pyrrolidine oxindolines have synthesized. • 1D and 2D-NMR spectroscopy found to be excellent tool for confirmation of the regio- and stereochemistry of the cycloadducts. • The regioselectivity were studied by evaluating global and local electrophilicity and nucleophilicity descriptors. • local descriptors Parr functions proposed by Domingo is promising indices to explain the regioselectivity of cycloaddition processes. An efficient and catalyst-free multicomponent sequence for synthesizing fused new polyheterocyclic pyrene-grafted dispiro-pyrrolidine oxindolines through 1,3-dipolar cycloaddition reaction mediated by non-stabilized azomethine ylides is reported herein. The regio- and stereochemistry of the cycloadducts were determined on the basis of one-dimensional (1D) and two-dimensional (2D) homonuclear and heteronuclear correlation NMR spectroscopy. The mechanism of the cycloaddition reaction, as well as regioselectivity were discussed by evaluating global and local electrophilicity and nucleophilicity descriptors at B3LYP/6-31G level of theory. The findings suggested that the polarity and charge transfer flow between azomethine ylides (dipole) and 5-chloro-3-(2-oxo-2-(pyren-1-yl)ethylidene)indolin-2-ones (dipolarophiles) was consistent with the global reactivity descriptors and substitutional pattern. These outcomes based on local descriptors Parr functions proposed by Domingo were found to be quite promising indices for the study of organic reactivity and to explain the regioselectivity of cycloaddition processes.

Binaphthyl-Bridged Pyrenophanes: Intense Circularly Polarized Luminescence Based on a D2 Symmetry Strategy.

A series of D2 -symmetric macrocycles composed of alternately linked pyrene and binaphthyl moieties (binaphthyl-bridged pyrenophanes) have been synthesized. Among them, a pyrenophane possessing ether linkers at the 2,7-positions of the pyrenes exhibited intense circularly polarized luminescence (CPL) with a |glum | value of 0.053. This value is by far the highest for excimers and was not sensitive to temperature, solvent, or concentration. The CPL originated from a twisting pyrene excimer, with the (R)-binaphthyl moieties producing a left-handed twist excimer, which exhibited (-)-CPL. The electric and magnetic transition dipole moments are perfectly parallel, which is the best relationship for strong CPL.

Binaphthyl‐Bridged Pyrenophanes: Intense Circularly Polarized Luminescence Based on aD2Symmetry Strategy

AbstractA series ofD2‐symmetric macrocycles composed of alternately linked pyrene and binaphthyl moieties (binaphthyl‐bridged pyrenophanes) have been synthesized. Among them, a pyrenophane possessing ether linkers at the 2,7‐positions of the pyrenes exhibited intense circularly polarized luminescence (CPL) with a |glum| value of 0.053. This value is by far the highest for excimers and was not sensitive to temperature, solvent, or concentration. The CPL originated from a twisting pyrene excimer, with the (R)‐binaphthyl moieties producing a left‐handed twist excimer, which exhibited (−)‐CPL. The electric and magnetic transition dipole moments are perfectly parallel, which is the best relationship for strong CPL.

Nonlinear optical properties of pyrene-based chalcone: (E)-1-(4′-bromo-[1,1′-biphenyl]-4-yl)-3-(pyren-1-yl)prop-2-en-1-one, a structure-activity study

The presence of C-H…O and π … π stacking, which form a head to tail and face to face arrangement chain along the b-axis, was shown by single crystal analysis. The small dihedral angle between the pyrene and bromo-biphenyl rings increases the overall molecule's conjugation, and the low dihedral angles between the enone group (acceptor) and both pyrene and bromo-biphenyl moieties (donors) show the molecule's high ICT characteristic. Theoretical studies were conducted utilising density functional theory (DFT) at the B3LYP,6-311++G (d,p) basis set. ICT transfer from pyrene and bromo biphenyl moieties to carboxyl group was observed using HOMO-LUMO diagrams and Hirshfeld surfaces analysis, generating a D-π-A-π-D type push-pull system. Z-scan open and closed aperture plots were used to obtain nonlinear optical characteristics of BBPP. The self-defocusing reaction is visible in the Z-scan results, which indicate a negative nonlinear refractive index. The optical limiting behavior of the crystal is also promising. The titled crystal is a promising material for NLO devices based on the NLO characteristics of BBPP.

Synthesis and manifold but controllable emission switching of stilbene-appended polyaromatic terpyridine derivatives via aggregation and trans–cis isomerization

We designed in this work a new series of stilbene-appended terpyridine systems covalently coupled with anthracene, naphthalene and pyrene moieties which can exhibit multiple yet controllable photo-switching behaviors under divergent conditions. Upon aggregation, these emissive compounds display either remarkable blue-shifted emission enhancement or emission quenching with red-shift, depending upon the nature of solvent. Both free- as well as aggregated forms of the compounds undergo trans → cis isomerization upon treating with visible light, accompanied with significant alteration in their spectral behaviors. The reverse cis → trans process is achieved on keeping the photolyzed solutions in dark. Hence, ‘on-off’ and ‘off-on’ emission switching is feasible upon successive exposure to light and keeping in dark. A gradual decrease in rate constant and quantum yield of photoisomerisation was observed with increase in extent of aggregation. Additionally, DFT and TD-DFT calculations are also carried out to interpret experimental spectral bands of the compounds.

Dynamic rotaxane-branched dendrimers with precisely arranged luminogens for efficient light harvesting

Although the development of artificial light-harvesting systems (LHSs) has attracted increasing attention, the construction of novel artificial LHSs with co-existed various types of precisely arranged luminogens has been still a major challenge. Herein, starting from [2]rotaxane building blocks AN-R or TPE-R functionalized with either anthracene or tetraphenylethene (TPE) moiety, a family of novel rotaxane-branched dendrimers containing two types of energy donors on the branches and one pyrene moiety at the central core as energy acceptor have been successfully constructed through a facile, efficient, and controllable divergent approach. Notably, attributed to the solvent-induced switching feature of the rotaxane branches, the integrated rotaxane-branched dendrimers displayed an interesting dynamic feature. More importantly, as revealed by fluorescence spectra, the resultant rotaxane-branched dendrimers displayed enhanced antenna effects along with the increase of dendrimer generation. Therefore, these rotaxane-branched dendrimers described herein could serve as not only promising platforms for light harvesting but also excellent candidates for the construction of smart supramolecular materials for practical applications.

An excimer ‘ON[sbnd]OFF’ switch based on telomeric G-quadruplex and rGO for trace thrombin detection

In the recent decade, GO has emerged as an amazing 2D nanomaterial for developing DNA-based biosensors due to its fluorescence quenching properties, whereas similar research based on rGO was reported rarely. Herein, a novel multi-pyrene functionalized G-rich DNA probe based on the screened rGO showed much higher fluorescence quenching efficiency and excimer emission than that of universal GO. Different from the universal thrombin detection of the G4-forming aptamer-TBA(GGTTGGTGTGGTTGG), the original telomeric sequence is used in this study. The excimer emission “ON-OFF” switch amplified the response of thrombin detection is as low as 50 units. Furthermore, for four pyrene moieties that are sited in a crowded steric circumstance, the melting temperature (Tm) values and molecular dynamics simulations showed a positive effect on duplex G-quadruplex or GDNA·cDNA stability, without disturbing its helix structure.

Strong emission of excimers realized by dense packing of pyrenes in tailored bola-amphiphile nano assemblies

Pyrene is known for the quenched emission of excimers, especially in aqueous solution. Here, we report strong emission of pyrene excimers realized in amphiphile assemblies by controlling the face-to-face distance between the pyrene planes. We find that both the self-assembly behavior and emission properties of a cationic pyrene-containing amphiphile (denoted by PRB) are altered by exchanging the counterions. Upon the addition of sodium mesitylenesulfonate (Na MtS), the excimer emission of pyrene in self-assembled aggregates of PRB is greatly enhanced in aqueous solution. Concomitantly, the disk-like assemblies of PRB are converted to spherical particles, in which the repulsive interactions of the head groups are screened by replacing the counterions of the PRB molecules. The quantum yield of PRB increases from 0.5% to 16.6%, which is attributed to the dense packing of pyrene moieties in the aggregates. This study demonstrates that controlling supramolecular interactions is a feasible avenue to enhance the emission of pyrene excimers in amphiphile assemblies. The face-to-face distance between neighboring pyrenes is reduced The excimer emission of pyrene derivatives was boosted in the aggregated state The quantum yield increases by 2 orders of magnitude to >16% Pyrene is known for the quenched emission of excimers, especially in aqueous solution. Zhao et al. report the enhanced excimer emission of pyrene derivatives by controlling the intermolecular interactions in the aggregated state of assemblies, whereby the quantum yield increased by 2 orders of magnitude to >16%.

Synthesis and Excimer Formation Properties of Electroactive Polyamides Incorporated with 4,5-Diphenoxypyrene Units.

A new dietherpyrene-cored diamine monomer, namely, 4,5-bis(4-aminophenoxy)pyrene, was successful synthesized and formed a series of electroactive polyamides with an aryloxy linkage in a polymer main chain and bearing pyrene chromophore as a pendent group using conventional one-pot polycondensation reactions with commercial aromatic/aliphatic dicarboxylic acids. The resulting polyamides exhibited good solubility in polar organic solvents and, further, can be made into transparent films. They had appropriate levels of thermal stability with moderately high glass-transition values. The dilute NMP solutions of these polyamides exhibited pyrene characteristic fluorescence and also showed a remarkable additional excimer emission peak centered at 475 nm. Electrochemical studies of these polymer films showed that these polyamides have both p- and n-dopable states as a result of the formation of radical cations and anions of the electroactive pyrene moieties.

The synthesis and crystal structure of pH-sensitive fluorescent pyrene-based double aza- and diaza[4]helicenes.

Novel pyrene-based double aza- and diaza[4]helicenes have been prepared through a five-step synthetic sequence in overall good yields. Commercially available 2,3-dihaloazines (2,3-dibromopyridine, 2,3-dichloropyrazine and 2,3-dichloroquinoxaline) were used as starting materials. The synthesis employs electrophile-induced cyclizations of ortho-alkynyl bihetaryls as the key steps, leading to the formation of a helical skeleton. To discern the effect of merging azine and pyrene moieties within a helical skeleton, the X-ray structures, UV-vis absorption and fluorescence spectra of the helicenes were investigated and compared with those of the parent [4]helicene, aza- and diaza[4]helicenes. It was found that the emission properties of the synthesized helicenes can be modulated as a function of pH. The basicity of pyrene-based double aza[4]helicenes was estimated by the direct fluorimetric titration method; the pKa value was found to be equal to 1.4.

Smartly engineered “off-on” switchable probe: For the recognition of toxic analytes in semi-aqueous medium

The pyrene moiety successfully serves as a source of ratiometric changes as well as electron acceptor. Thus pyrene ring has been introduced to phenanthroimidazole to the optical response towards different metal ions and anions. Phenanthroimidazole derivative bearing pyrene group found to be a ratiometric sensor for Hg2+/Al3+ ions. Hg2+ ions and Al3+ ions having least detection limit of 10 μM and F− ions having least detection limit value of 0.5 μM. Interestingly, probe exhibited a selective, enhanced ratiometric fluorescence change, colrometric change and “off- on” behavior with F- ions among the different anions in semi aqueous media and contribute to the formation of AND gate.