Nonconjugated Biocompatible Macromolecular Luminogens for Sensing and Removals of Fe(III) and Cu(II): DFT Studies on Selective Coordination(s) and On-Off Sensing

This work reports the design and synthesis of two nonaromatic biocompatible macromolecular luminogens, i.e., 2-(dimethylamino)ethyl methacrylate-co-2-(dimethylamino)ethyl 3-(N-(methylol)acrylamido)-2-methylpropanoate-co-N-(methylol)acrylamide/DMAEMA-co-DMAENMAMP-co-NMA (P1) and methacrylic acid-co-3-(N-(methylol)acrylamido)-2-methylpropanoic acid-co-N-(methylol)acrylamide/MEA-co-NMAMPA-co-NMA (P2), prepared through in situ anchored acrylamido-ester/DMAENMAMP and acrylamido-acid/NMAMPA third comonomers, respectively, in a facile polymerization of two non-luminous monomers in water medium to circumvent the drawbacks related to aggregation-caused quenching of aromatic luminogens. The structures of P1/P2, in situ anchored comonomers, fluorophores, N-branching associated n-π* interactions, and hydrogen bonding assisted aggregation-enhanced emissions are comprehended by nuclear magnetic resonance, Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible, thermogravimetric analysis (TGA), dynamic light scattering (DLS), transmission electron microscopy (TEM), fluorescence lifetime, and fluorescence imaging. P1 and P2 are appropriate for sensitive detections/exclusions of Fe(III)/Cu(II) and cell-imaging. The intrinsic fluorescence, on-off sensing, selective coordinations of Fe(III) and Cu(II) with fluorophores, emission quenching mechanisms, and removals of Fe(III) and Cu(II) are investigated by DFT/NTO analyses of P1/P2 and Fe(III)-P1 and Cu(II)-P2 complexes, XPS, and isotherms and kinetics parameters. The excellent biocompatibilities, comparable limit of detections, i.e., 1.70 × 10^-7 and 1.59 × 10^-7 [m], and higher adsorption capacities, i.e., 77.25 and 154.13 mg g^-1 , at low ppm; 303 K; and pH = 7 compel P1/P2 to be acceptable for multipurpose applications.

Synthesis of Biocompatible Aliphatic Terpolymers via In Situ Fluorescent Monomers for Three-in-One Applications: Polymerization of Hydrophobic Monomers in Water

Biocompatible, nonconventional, multifunctional, purely aliphatic, light-emitting terpolymers, i.e., acrylonitrile-co-3-(N-isopropylacrylamido)propanenitrile-co-N-isopropylacrylamide (AN-co-NIPAMPN-co-NIPA, 1) and acrylonitrile-co-3-(N-hydroxymethylacrylamido)propanenitrile-co-N-hydroxymethylacrylamide (AN-co-NHMAMPN-co-NHMA, 2), were designed and synthesized via N-H-functionalized C-C + N-C-coupled in situ protrusions/grafting of fluorophore monomers, i.e., NIPAMPN and NHMAMPN, by solution polymerization of two highly hydrophobic nonemissive monomers in water. These scalable and reusable 1 and 2 were suitable for high-performance three-in-one applications, such as Fe(III) sensors, imaging of Madin-Darby canine kidney (MDCK) and human lung cancer (A549) cells, and security inks. The structures of 1 and 2, N-C-coupled in situ attachments/grafting of third fluorophore monomers, grafting events, and aggregation-enhanced emissions (AEEs), were analyzed by ¹H and ¹³C NMR spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, thermogravimetric (TG) analysis, high-resolution transmission electron microscopy (HRTEM), dynamic light scattering (DLS), fluorescence imaging, and fluorescence lifetime. The geometries, electronic structures, and absorption/emission properties of 1 and 2 at optimized compositions were examined by density functional theory (DFT), time-dependent DFT (TDDFT), and natural transition orbital (NTO) analyses. The limits of detection were 3.20 × 10^-7 and 1.37 × 10^-7 M for 1 and 2, respectively. The excellent biocompatibility of 1 and 2 was confirmed by >95% retention of MDCK and A549 cell morphologies.

Light-Emitting Multifunctional Maleic Acid-co-2-(N-(hydroxymethyl)acrylamido)succinic Acid-co-N-(hydroxymethyl)acrylamide for Fe(III) Sensing, Removal, and Cell Imaging

The intrinsically fluorescent highly hydrophilic multifunctional aliphatic terpolymer, maleic acid (MA)-co-2-(N-(hydroxymethyl)acrylamido)succinic acid (NHASA)-co-N-(hydroxymethyl)acrylamide (NHMA), that is, 1, was designed and synthesized via C-C/N-C-coupled in situ allocation of a fluorophore monomer, that is, NHASA, composed of amido and carboxylic acid functionalities in the polymerization of two nonemissive MA and NHMA. The scalable and reusable intrinsically fluorescent biocompatible 1 was suitable for sensing and high-performance adsorptive exclusion of Fe(III), along with the imaging of Madin-Darby canine kidney cells. The structure of 1, in situ fluorophore monomer, aggregation-induced enhanced emission, cell-imaging ability, and superadsorption mechanism were studied via microstructural analyses using 1H/13C NMR, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, atomic absorption spectroscopy, ultraviolet-visible spectroscopy, thermogravimetric analysis, dynamic light scattering, high-resolution transmission electron microscopy, solid-state fluorescence, fluorescence lifetime, and fluorescence imaging, along with measuring kinetics, isotherms, and thermodynamic parameters. The location, electronic structures, and geometries of the fluorophore and absorption and emission properties of 1 were investigated using density functional theory and natural transition orbital analyses. The limit of detection and the maximum adsorption capacity were 2.45 × 10-7 M and 542.81 mg g-1, respectively.

Fluorescent Terpolymers via In Situ Allocation of Aliphatic Fluorophore Monomers: Fe(III) Sensor, High-Performance Removals, and Bioimaging

Herein, purely aliphatic intrinsically fluorescent terpolymers, i.e., 1 and 2, are synthesized through one-pot solution polymerization via N-H functionalized and multi C-C/C-N coupled in situ protrusion of fluorescent monomers using two nonemissive monomers. These scalable terpolymers are suitable for highly selective Fe(III) sensing, high-performance exclusion of Fe(III), logic function and the imaging of normal mammalian Madin-Darby canine kidney and human osteosarcoma cancer cell lines. The structures of terpolymers, in situ attachment of fluorescent monomers, clusteroluminescence, adsorption-mechanism, and cell-imaging abilities are understood via unadsorbed and/or adsorbed microstructural analyses using ¹ H/¹³ C NMR, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV-vis spectroscopy, atomic absorption spectroscopy, thermogravimetric analysis, high-resolution transmission electron microscopy, dynamic light scattering, fluorescence imaging, and fluorescence lifetime. The geometries, electronic structures, location of fluorophores, and singlet-singlet absorption and emission of terpolymers are examined using density functional theory (DFT) and time-dependent DFT. For the precise identification of fluorophores, transition from occupied natural transition orbitals (NTOs) to unoccupied NTOs is computed. For 1/2, limit of detection (LOD) values and adsorption capacities are 6.0 × 10^-7 /8.0 × 10^-7 m and 147.82/120.56 mg g^-1 at pH_i = 7.0 and 303 K, respectively. The overall properties of 1 are more advantageous compared to 2 in sensing, cell imaging, and adsorptive exclusion of Fe(III).

Novel Cyanostilbene-Based Fluorescent Chemoprobe for Hydroxyl Radicals and Its Two-Photon Bioimaging in Living Cells

A novel cyanostilbene derivative as a selective fluorescent chemoprobe for hydroxyl radicals was synthesized. The chemoprobe shows strong green emission in aqueous solution with the addition of hydroxyl radicals. Conversely, negligible emission changes are observed upon addition of other reactive oxygen species. The chemoprobe 1 shows high sensitivity, having the low detection limit of ∼1.0 × 10^-7 M. Furthermore, the fluorescent chemoprobe exhibits low cytotoxicity and is effectively applied to bioimaging of hydroxyl radicals by two-photon confocal microscopy in HeLa cells. These results indicate that the new chemoprobe has great potential for bioimaging in vivo and in vitro systems.

A fluorescent conjugated polymer photocatalyst based on Knoevenagel polycondensation for hydrogen production

An organic polymer photocatalyst (p-P) for hydrogen production was designed and synthesized through Knoevenagel condensation with a high yield.

Self-Assembled Triphenylphosphonium-Conjugated Dicyanostilbene Nanoparticles and Their Fluorescence Probes for Reactive Oxygen Species

We report self-assembled novel triphenylphosphonium-conjugated dicyanostilbene-based as selective fluorescence turn-on probes for ¹O₂ and ClO-. Mono- or di-triphenylphosphonium-conjugated dicyanostilbene derivatives 1 and 2 formed spherical structures with diameters of ca. 27 and 56.5 nm, respectively, through π-π interaction between dicyanostilbene groups. Self-assembled 1 showed strong fluorescent emission upon the addition of ¹O₂ and ClO- compared to other ROS (O₂-, •OH, NO, TBHP, H₂O₂, GSH), metal ions (K⁺, Na⁺), and amino acids (cysteine and histidine). Upon addition of ¹O₂ and ClO-, the spherical structure of 1 changed to a fiber structure (8-nm wide; 300-nm long). Upon addition of ¹O₂ and ClO-, the chemical structural conversion of 1 was determined by FAB-Mass, NMR, IR and Zeta potential analysis, and the strong emission of the self-assembled 1 was due to an aggregation-induced emission enhancement. This self-assembled material was the first for selective ROS as a fluorescence turn-on probe. Thus, a nanostructure change-derived turn-on sensing strategy for ¹O₂ or ClO- may offer a new approach to developing methods for specific guest molecules in biological and environmental subjects.

Four new metal–organic frameworks based on diverse secondary building units: sensing and magnetic properties

Four new metal–organic frameworks based on diverse secondary building units were assembled and 1 showed high selectivity in the detection of CrO₄²⁻, Cr₂O₇²⁻, MnO₄⁻ and Fe³⁺.

Seven luminescent metal–organic frameworks constructed from 5-(triazol-1-yl)nicotinic acid: luminescent sensors for CrVI and MnO4− ions in an aqueous medium

Seven new luminescent metal–organic frameworks were assembled and complex 2 shows high selectivity and sensitivity for CrO₄²⁻, Cr₂O₇²⁻ and MnO₄⁻ ions with low detection limits.

Design and synthesis of a new class of 2,4-thiazolidinedione based macrocycles suitable for Fe3+sensing

Three 2,4-thiazolidinedione based macrocycles, which are very good Fe³⁺sensors in aqueous-ethanol medium, have been synthesized. X-ray crystallography, DFT calculations and MEP analysis have been used for their structural confirmation and for understanding their behavior towards Fe³⁺.

Rational synthesis of a luminescent uncommon (3,4,6)-c connected Zn(ii) MOF: a dual channel sensor for the detection of nitroaromatics and ferric ions

A 3D (3,4,6)-c connected net constructed using a rigid tetracarboxylate ligand and sensing studies to detect nitroaromatics and ferric ion performed.

N-Benzoyl dithieno[3,2-b:2',3'-d]pyrrole-based hyperbranched polymers by direct arylation polymerization

BACKGROUND

Although poly(N-acyl dithieno[3,2-b:2',3'-d]pyrrole)s have attracted great attention as a new class of conducting polymers with highly stabilized energy levels, hyperbranched polymers based on this monomer type have not yet been studied. Thus, this work aims at the synthesis of novel hyperbranched polymers containing N-benzoyl dithieno[3,23,2-b:2',3'-d]pyrrole acceptor unit and 3-hexylthiophene donor moiety via the direct arylation polymerization method. Their structures, molecular weights and thermal properties were characterized via 1H NMR and FTIR spectroscopies, GPC, TGA, DSC and XRD measurements, and the optical properties were investigated by UV-vis and fluorescence spectroscopies.

RESULTS

Hyperbranched conjugated polymers containing N-benzoyl dithieno[3,23,2-b:2',3'-d]pyrrole acceptor unit and 3-hexylthiophene donor moiety, linked with either triphenylamine or triphenylbenzene as branching unit, were obtained via direct arylation polymerization of the N-benzoyl dithieno[3,23,2-b:2',3'-d]pyrrole, 2,5-dibromo 3-hexylthiophene and tris(4-bromophenyl)amine (or 1,3,5-tris(4-bromophenyl)benzene) monomers. Organic solvent-soluble polymers with number-average molecular weights of around 18,000 g mol-1 were obtained in 80-92% yields. The DSC and XRD results suggested that the branching structure hindered the stacking of polymer chains, leading to crystalline domains with less ordered packing in comparison with the linear analogous polymers. The results revealed that the hyperbranched polymer with triphenylbenzene as the branching unit exhibited a strong red-shift of the maximum absorption wavelength, attributed to a higher polymer stacking order as a result of the planar structure of triphenylbenzene.

CONCLUSION

Both hyperbranched polymers with triphenylamine/triphenylbenzene as branching moieties exhibited high structural order in thin films, which can be promising for organic solar cell applications. The UV-vis absorption of the hyperbranched polymer containing triphenylbenzene as branching unit was red-shifted as compared with the triphenylamine-containing polymer, as a result of a higher chain packing degree.

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.