Emission behavior of naphthalimide-coumarin cassette

ABSTRACT

In this contribution, a dye (C₈-alkyl substituted Naphthalimide-Coumarin, CNC) with naphthalimide and coumarin incorporated together with -NHN = bridge unit. The compound was fully characterized by NMR and HRMS spectroscopic techniques. Highly emissive character was investigated in detail in various polar environments. The emission maximum varied from 430 to 470 nm. In polycarbonate film, CNC is also highly emissive with 560 nm emission peak. While in sold, the emission maximum was further shifted to 580 nm due to the more tightly packing mode than that in film. The C₈-alkyl substitution enhances the solubility of CNC and also contributes most to its solid emission.     

CO2-fixation into carbonate anions for the construction of 3d-4f cluster complexes with salen-type Schiff base ligands: from molecular magnetic refrigerants to luminescent single-molecule magnets

Six new carbonate-bridged Zn₂Ln₂ cluster complexes derived from salen-type Schiff base ligands [H₂L^a = N, N′-bis(3-methoxysalicylidene)-1,3-diaminopropane and H₂L^b = N, N′-bis(3-methoxysalicylidene)- 1,2-diaminoethane] have been synthesized. The bis-imine chain in Schiff base ligands have an obvious influence on the cluster complexes' structures, magnetic and luminescence properties. The carbonate bridging ligand exactly comes from autoimmobilization of carbon dioxide, which may mediate ferromagnetic coupling between Ln³⁺ ions, favoring magnetocaloric effects and single molecule magnet (SMM) properties. Complexes Zn₂Dy₂(μ³-CO₃)₂(L^a)₂(NO₃)₂(MeOH)₂ ( 1 ) and [Zn₂Dy₂(μ³-CO₃)₂(L^b)₂(NO₃)₂]·2MeOH ( 2) show field-induced SMM properties; complexes Zn₂Tb₂(μ³-CO₃)₂(L^a)₂(NO₃)₂(MeOH)₂ ( 3 ) and [Zn₂Tb₂(μ³-CO₃)₂(L^b)₂(NO₃)₂]·2MeOH ( 4 ) display both luminescence and field-induced SMM behaviors; while complexes [Zn₂Gd₂(μ³-CO₃)₂(L^a)₂(NO₃)₂]·2MeOH ( 5 ) and [Zn₂Gd₂(μ³-CO₃)₂(L^b)₂(NO₃)₂]·2MeOH ( 6 ) exhibit medium magnetic entropy changes, which are candidates for cryogenic molecular magnetic refrigerants.     

Euphorbia polygonifolia extract assisted biosynthesis of Fe3O4@CuO nanoparticles: Applications in the removal of metronidazole,ciprofloxacin and cephalexin antibiotics from aqueous solutions under UV irradiation

In this study, a new, economical and green method was reported for synthesizing Fe₃O₄@CuO nanoparticles without adding any surfactants using Euphorbia polygonifolia extract as a renewable, mild and safe reducing agent and effective stabilizer. The green synthesized NPs were analyzed by various methods such as XRD, FESEM, FT-IR, EDS, VSM, UV–visible, DRS, BET and TGA-DTA. Based on the BET analysis, the Fe₃O₄@CuO NP had a surface area of 69.20 m²/g. The FTIR analysis verified the existence of different functional groups of phytochemicals from Euphorbia polygonifolia extract which were accountable for the NPs formation. The catalytic performance of the catalyst for the degradation of metronidazole, ciprofloxacin and cephalexin antibiotics was examined in aqueous mediums at room temperature. The results showed an extraordinary catalytic performance, easy reusability and long-term stability of the composite for reducing antibiotic pollution. In this process, the effects of environmental conditions such as initial pH of the environment, initial concentration of antibiotics, the concentration of modified photocatalyst and reaction time were studied. According to the results, at the optimal conditions, the highest removal efficiency for metronidazole, ciprofloxacin and cephalexin antibiotics using Fe₃O₄@CuO nanoparticles, were 89%, 94%, and 96%, respectively. Also, it was observed that even after recycling, the NPs presents good nanocatalytic stability for the degradation of antibiotics. Using the NPs for five cycles did not significantly alter the photocatalyst efficiency, showing that the photocatalytic stability of the NPs was excellent.     

Promising new catalytic properties of a Co (II)-carboxamide complex and its derived Co3O4 nanoparticles for the Mizoroki-Heck and the Epoxidation reactions

The new Co(II) - carboxamide complex ( 1 ) and Co₃O₄ nanoparticles ( 2 ), by way of thermal decomposition of ( 1 ) have been efficiently synthesised in the environment-friendly. X-ray diffraction reveals a slightly distorted octahedral coordination of cobalt (four nitrogens and two oxygens) in ( 1 ) and regular octahedral or tetrahedral ones (oxygens only) in ( 2 ). The investigation of ( 1 ) and ( 2 ) in the Mizoroki-Heck and epoxidation of alkens reactions showed them both to be powerful, green and inexpensive catalysts.     

Sulfonic acid-functionalized Fe3O4-supported magnetized graphene oxide quantum dots: A novel organic-inorganic nanocomposite as an efficient and recyclable nanocatalyst for the synthesis of dihydropyrano[2,3-c]pyrazole and 4H-chromene derivatives

In this research, the main emphasis has been focused on the preparation of a novel Fe₃O₄-supported propane-1-sulfonic acid-grafted graphene oxide quantum dots (Fe₃O₄@GOQD-O-(propane-1-sulfonic acid)) that it was readily synthesized via a five-step procedure as a hitherto unreported magnetic nanocatalyst. This newly prepared Fe₃O₄@GOQD-O-(propane-1-sulfonic acid) nanocomposite was structurally well-established by different analytical techniques including Fourier transform infrared (FT-IR), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), thermal gravimetric analysis (TGA), field emission gun-scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometer (VSM) analyses. The high catalytic performance of this nanocomposite was exhibited in one-pot synthesis of dihydropyrano[2,3-c]pyrazole and 4H-chromene derivatives under mild conditions. Low reaction times, excellent yields of the products, benignity of the catalyst, easy reaction work-up and magnetic recyclability of the catalyst are the main advantages of the present protocol. Also, our research indicated that the Fe₃O₄@GOQD-O-(propane-1-sulfonic acid) could be reused up to five times without considerable loss of catalytic activity.     

Local atomic and electronic structure in the LiVPO4(F,O) tavorite-type materials from solid-state NMR combined with DFT calculations

⁷Li, ³¹P, and ¹⁹F solid-state nuclear magnetic resonance (NMR) spectroscopy was used to investigate the local arrangement of oxygen and fluorine in LiVPO₄F_1-yO_y materials, interesting as positive electrode materials for Li-ion batteries. From the evolution of the 1D spectra versus y, 2D ⁷Li radiofrequency-driven recoupling (RFDR) experiments combined, and a tentative signal assignment based on density functional theory (DFT) calculations, it appears that F and O are not randomly dispersed on the bridging X position between two X–VO₄–X octahedra (X = O or F) but tend to segregate at a local scale. Using DFT calculations, we analyzed the impact of the different local environments on the local electronic structure. Depending on the nature of the VO₄X₂ environments, vanadium ions are either in the +III or in the +IV oxidation state and can exhibit different distributions of their unpaired electron(s) on the d orbitals. Based on those different local electronic structures and on the computed Fermi contact shifts, we discuss the impact on the spin transfer mechanism on adjacent nuclei and propose tentative signal assignments. The O/F clustering tendency is discussed in relation with the formation of short V^IVO vanadyl bonds with a very specific electronic structure and possible cooperative effect along the chain.     

Monofluoroalkene-Isostere as a 19F NMR Label for the Peptide Backbone: Synthesis and Evaluation in Membrane-Bound PGLa and (KIGAKI)3

Solid-state ¹⁹F NMR is a powerful method to study the interactions of biologically active peptides with membranes. So far, in labelled peptides, the ¹⁹F-reporter group has always been installed on the side chain of an amino acid. Given the fact that monofluoroalkenes are non-hydrolyzable peptide bond mimics, we have synthesized a monofluoroalkene-based dipeptide isostere, Val-Ψ[(Z)-CF=CH]-Gly, and inserted it in the sequence of two well-studied antimicrobial peptides: PGLa and (KIGAKI)₃ are representatives of an α-helix and a β-sheet. The conformations and biological activities of these labeled peptides were studied to assess the suitability of monofluoroalkenes for ¹⁹F NMR structure analysis.     

Cobalt(II)-Catalyzed [4+2] Annulation of Picolinamides with Alkynes via C−H Bond Activation

A cobalt(II)-catalyzed [4+2] annulation of picolinamides with alkynes via C−H bond activation has been developed. The operationally simple annulation reaction allows for the synthesis of acyl-substituted 1H-benzoquinoline bearing multiple aromatic rings (up to 96 % yield) without co-oxidant or other oxidation factors under mild conditions. Several control experiments were carried out. This practical [4+2] annulation provides an efficient route to access highly functionalized compounds.     

One Terminal Guanosine Flip of Intramolecular Parallel G-Quadruplex: Catalytic Enhancement of G-Quadruplex/Hemin DNAzymes

Numerous studies have shown compelling evidence that incorporation of an inversion of polarity site (IPS) in G-rich sequences can affect the topological and structural characteristics of G-quadruplexes (G4s). Herein, the influence of IPS on the formation of a previously studied intramolecular parallel G4 of d(G₃TG₃TG₃TG₃) (TTT) and its stacked higher-order structures is explored. Insertion of 3′–3′ or 5′–5′ IPS did not change the parallel folding pattern of TTT. However, both the species and position of the IPS in TTT have a significant impact on the G4 stability and end-stacking through the alteration of G4–G4 interfaces properties. The data demonstrate that one base flip in each terminal G-tetrad can stabilize parallel G4s and facilitate intermolecular packing of monomeric G4s. Such modifications can also enhance the fluorescence and enzymatic performances by promoting interactions between parallel G4s with N-methyl mesoporphyrin IX (NMM) and hemin, respectively.     

Switching the Switch: Ligand Induced Disulfide Formation in HDAC8

Human histone deacetylase 8 is a well-recognized target for T-cell lymphoma and particularly childhood neuroblastoma. PD-404,182 was shown to be a selective covalent inhibitor of HDAC8 that forms mixed disulfides with several cysteine residues and is also able to transform thiol groups to thiocyanates. Moreover, HDAC8 was shown to be regulated by a redox switch based on the reversible formation of a disulfide bond between cysteines Cys₁₀₂ and Cys₁₅₃. This study on the distinct effects of PD-404,182 on HDAC8 reveals that this compound induces the dose-dependent formation of intramolecular disulfide bridges. Therefore, the inhibition mechanism of HDAC8 by PD-404,182 involves both, covalent modification of thiols as well as ligand mediated disulfide formation. Moreover, this study provides a deep molecular insight into the regulation mechanism of HDAC8 involving several cysteines with graduated capability to form reversible disulfide bridges.