In Situ Generated 1:1 Zn(II)-Containing Polymer Complex Sensor for Highly Enantioselective Recognition of N-Boc-Protected Alanine

Chiral Binaphthol Fluorescent Materials Based on a Novel Click Reaction

Because of easy functionalization, low cost, and large-scale fabrication, pure organic fluorescent polymers are widely applied in light-emitting display, bio-fluorescence-enhanced imaging, explosive detection, and other fields. Among these applications, due to their unique optical rotation characteristics, chiral fluorescent polymer materials are part of fluorescent polymers which could be used in chiral molecular detection and separation, biological target detection, etc. In this work, we designed and synthesized the first chiral organic fluorescent polysulfate materials through sulfur fluoride exchange polymerization (new click chemistry) by asymmetric binaphthol molecular. The chiral fluorescent polysulfate were synthesized by R/S [1,1′-binaphthalene]-2,2′-diol(Binol.), propane-2,2-diylbis(4,1-phenylene) bis(sulfurofluoridate) (FO2S–BA–SO2F) and 4,4′-(propane-2,2-diyl)diphenol(BA.) through step-by-step polymerization reaction under alkali present. It was found that the local crystallization of pure bisphenol A polysulfate was broken by the asymmetric axial chiral BINOL molecule inserted in it and let the polymer into the amorphous state. Fluorescent chiral molecules are uniformly dispersed in the polymer; the 120 µm film prepared by the film scraper was transparent and had good luminescence characteristics under ultraviolet light. After fluorescence detection, the excitation wavelength is 450 nm, and the emission wavelength is 480 and 517 nm.

An air-stable organometallic polymer containing titanafluorene moieties obtained by the Sonogashira-Hagihara cross-coupling polycondensation

The synthesis of a polymer containing alternating titanafluorene and arylene ethynylene moieties is described. The polymerization of a 2,7-dibromo-9-titanafluorene derivative with 1,4-dioctyloxy-2,5-diethynylbenzene is carried out at 70 °C for 48 h in tetrahydrofuran (THF) in the presence of palladium dichloride/4,5-bis(diphenylphosphino)-9,9-dimethylxanthene as a catalyst and diisopropylamine as a base to produce a dark red polymer. The polymer thus obtained is soluble in organic solvents and stable towards both air and moisture. In the UV-vis absorption spectrum of the polymer, the absorption maxima (λ_max) are observed at 321 nm and 395 nm, which are bathochromically shifted compared to those of a model compound of the repeating unit, a 2,7-bis(phenylethynyl)titanafluorene derivative (λ_max = 309 nm and 364 nm). The optical band gap (E_g) of the polymer is estimated to be 2.8 eV on the basis of the absorption onset, which is narrower than that of the model compound (3.1 eV).

Solid-State Emissive Metallo-Supramolecular Assemblies of Quinoline-Based Acyl Hydrazone

Development of fluorescence-based sensory materials for metal elements is currently in the mainstream of research due to the simplicity and usability of fluorescence as a method of detection. Herein, we report a novel "bis"-quinoline-based acyl hydrazone-named bQH that could be synthesized by a facile, low-cost method through simple condensation of hydrazide with an aldehyde. This acyl hydrazone showed emissive properties through Zn selective binding, especially in its solid-state, as shown by experiments such as UV-Vis, photoluminescence (PL), nuclear magnetic resonance (NMR), and inductively-coupled plasma-optical emission spectroscopies (ICP-OES), and energy-dispersive X-ray spectroscopy (EDS) mapping. The binding modes in which bQH coordinates to Zn2+ was proved to consist of two modes, 1:1 and 1:2 (bQH:Zn2+), where the binding mode was controlled by the Zn2+ ion content. Under the 1:1 binding mode, bQH-Zn2+ complexes formed a polymeric array through the metallo-supramolecular assembly. The resulting bQH-Zn2+ complex maintained its fluorescence in solid-state and exhibited excellent fluorescence intensity as compared to the previously reported quinoline-based acyl hydrazone derivative (mQH).

Synthesis, chiroptical properties, and self-assembled nanoparticles of chiral conjugated polymers based on optically stable helical aromatic esters

By Suzuki coupling reaction, three pairs of chiral conjugated polymers with optically stable helical aromatic ester subunits as the main-chain were designed and synthesized. Polymers (+)-P-P1 and (-)-M-P1, (+)-P-P2 and (-)-M-P2 showed strong fluorescence emission, strong mirror image CD and circularly polarized luminescence (CPL) signals in THF. For polymers (+)-P-P3 and (-)-M-P3, containing the tetraphenylethene (TPE) moiety, they not only showed obvious aggregation induced enhancement emission (AIEE), but also exhibited mirror image CD signals and aggregation-induced enhancement CPL signals in THF-water mixtures. Moreover, (+)-P-P3 and (-)-M-P3 could also form chiral nanoparticles by solvent evaporation induced self-assembly. Interestingly, it was further found that the size of the nanoparticles could be controlled by the changing of THF/water ratio, and their CPL properties were also shown.

Polymer Amplified Enantioselectivity in the Fluorescent Recognition of Prolinol

A 1,1'-bi-2-naphthol (BINOL)-aldehyde-based polymer has been synthesized that exhibits enantioselective fluorescent enhancement toward prolinol. It is found that the polymer shows greatly amplified enantioselectivity over the parent small-molecule sensor under the same conditions. This is attributed to the photoinduced electron transfer processes between the BINOL units in the polymer chain as well as the different steric environment provided by the polymer.

A New Polymer-Based Fluorescent Chemosensor Incorporating Propane-1,3-Dione and 2,5-Diethynylbenzene Moieties for Detection of Copper(II) and Iron(III)

A novel conjugated polymer (PDBDBM) was developed by the polymerization of 1,4-dioctyloxy-2,5-diethynylbenzene with 1,3-bis(4-bromophenyl)propane-1,3-dione based on Pd-catalyzed Sonogashira-coupling reaction. The obtained polymer PDBDBM exhibited bright green photoluminescence under UV irradiation. According to the metal ion titration experiments, PDBDBM showed high sensitivity and selectivity for detection of Cu2+ and Fe3+ over other metal ions. The fluorescent detection limits of PDBDBM were calculated to be 5 nM for Cu2+ and 0.4 μM for Fe3+ and the Stern⁻Volmer quenching constant for Cu2+ and Fe3+ were found to be 1.28 × 10⁸ M-1 and 2.40 × 10⁴ M-1, respectively. These results indicated that the polymer can be used as a potential probe for Cu2+ and Fe3+ detection.

Conjugated polymer-enhanced enantioselectivity in fluorescent sensing

A new strategy to use conjugated polymers to conduct fluorescent enhancement sensing has been developed.

A new strategy to use conjugated polymers to conduct fluorescent enhancement sensing has been developed. Chiral 1,1′-bi-2-naphthol-based binding sites are linked by p-phenylene units to construct a conjugated polymer whose fluorescence is quenched by the aldehyde groups introduced at each binding site. Interaction of this polymer with chiral amino alcohols in the presence of Zn(ii) leads to highly enantioselective fluorescent enhancement. It is found that the chiral conjugated polymer shows greatly enhanced enantioselectivity over the corresponding small molecular sensor under the same conditions. This work provides the first example that a conjugated polymer is used to greatly increase the enantioselectivity of a small molecular sensor in chiral recognition. Simultaneous determination of the concentration and enantiomeric composition of chiral substrates by a fluorescent measurement has been achieved by combining the polymer with salicylaldehyde in the assay.

Salen-based enantiomeric polymers for enantioselective recognition

In a simple way, the spatial arrangement of the building blocks in a main chain polymer determines its recognition properties.

Synthesis and fluorescence study of conjugated polymers based on 2,4,6-triphenylpyridine moieties

Three novel 2,4,6-triphenylpyridine-based conjugated polymers showed strong fluorescence emission with large Stokes' shifts, tunable band gaps and high quantum yields.

Synthesis of a multifunctional poly(p-phenylene ethynylene) scaffold with clickable azide-containing side chains for (bio)sensor applications

Clickable poly(p-phenylene ethynylene) (PPE) copolymers were designed and synthesized towards (bio)sensor applications.

Ternary system based on fluorophore-surfactant assemblies--Cu²⁺ for highly sensitive and selective detection of arginine in aqueous solution

A new cationic dansyl derivative-based (DIlSD) fluorescence probe was designed and synthesized. Its combination with anionic surfactant SDS assemblies shows enhanced fluorescence intensity and blue-shifted maximum wavelength. Its fluorescence can be slightly quenched by Cu(2+); however, the fluorescence quenching efficiency by Cu(2+) is highly increased upon titration of arginine (Arg). As a result, the ternary system containing the cationic fluorophore, anionic surfactant, and Cu(2+) functions as a highly sensitive and selective sensor to Arg. The optimized sensor system displays a detection limit of 170 nM, representing the highest sensitivity to Arg in total aqueous solution by a fluorescent sensor. Control experiments reveal that the imidazolium groups in the fluorophore, the anionic surfactant, and Cu(2+) all play important roles in the process of sensing Arg. The electrostatic interaction between the cationic fluorophore and anionic surfactants facilitates the binding of imidazolium rings with Cu(2+), the surfactant surface-anchored Cu(2+) is responsible for further binding of Arg, and the electrostatic interaction between anionic surfactants and positively charged amino acids accounts for the selective responses to Arg.

Synthesis, spectral characterization and biological activity of metal(II) complexes with 4-aminoantipyrine derivatives

Novel metal(II) complexes derived from furfurylidene-4-aminoantipyrine and 2-aminobenzothiazole were synthesized and characterized by spectroscopic (IR, (1)H NMR, UV-Vis., ESR and DART-MS) and other analytical methods. IR spectral studies indicate the binding sites of the ligand with the metal ion. Molar conductance data and magnetic susceptibility measurements provide evidence for monomeric and neutral nature of the complexes. The X band ESR spectrum of the Cu(II) complex at 300 and 77K was recorded. The electrochemical behaviour of the complexes in MeCN at 298 K was studied. Thermal studies of the ligand and its complexes show the presence of coordinated water in the complexes. The grain size of the complex was calculated by Scherrer formula using powder XRD. The surface morphology of the complexes was studied using SEM. The in vitro biological screening of the ligand and its complexes were tested against bacterial species S. aureus, E. coli, K. pneumoniae, P. vulgaris and P. aeruginosa and fungal species A. niger, R. stolonifer, A. flavus, R. bataicola and C. albicans. The DNA binding and cleavage activity of the ligand and its complexes were studied. Super oxide dismutase (SOD) activities of the ligand and its complexes have also been measured.