Germylyne complex [Cp*(OC)2Cr≡Ge{C(SiMe3)3}] (1) reacted with methyl vinyl ketone to give an η3-allyl complex 2 with an oxagermacyclopentenyl ring. An analogous η3-allyl complex 3 with a germacyclopentenyl ring was obtained by the reaction with butadiene, a non-polar conjugated molecule, under photoirradiation. These reactions are accompanied by cleavage of the Cr≡Ge triple bond. On the other hand, the reactions of complex 1 with alkynes under photoirradiation resulted in clean substitution of a CO ligand of 1 to afford (η2-alkyne)germylyne complexes, where the Cr≡Ge triple bond is intact.
Folic Acid‐Modified Nanoprobe for in Vivo Targeted Persistent Luminescence Imaging and pH‐Responsive Antibiotic Therapy of Bacterial Infection
Low antibiotic utilization and inability to achieve real-time monitoring of pathological status and treatment processes often result in unsatisfactory performance against bacterial infection. Developing a targeting antibacterial nanoprobe combining imaging with stimulus-response antibiotic release is a promising strategy to precisely recognize lesions and enhance therapeutic efficacy for bacterial infection. In this work, we report a pH-responsive theragnostic nanoplatform for targeted imaging and local drug release at the bacterial infection site. The nanoplatform consists of the core-shell structure with persistent luminescence nanoparticles (PLNPs) as the core for autofluorescence-free luminescence imaging and zeolitic imidazolate framework-8 as the shell (ZIF-8) to act as a carrier for antibiotics cefazolin. The core-shell nanostructure is further conjugated with folic acid to facilitate the uptake and accumulation of the nanoparticles, and realize the autofluorescence-free targeted imaging of the infection site. The acidic microenvironment at the bacterial infection site enables ZIF-8 to decompose for specific drug release improve the performance in bacterial infection treatment. The developed pH-responsive nanotheranostic probe is promising for autofluorescence-free targeted imaging and therapy of bacterial infection.
Theoretical Study on TiOOH Production over Au/TiO2 Catalyst — Support Dependency of Propylene Oxide Production—
Chemistry Letters, Ahead of Print.
Facile mechanochemical reduction and lithium‐ion doping of transition‐metal oxides
Transition-metal oxides (MOx) play essential roles in chemistry, catalysis, materials science and metallurgy. The MOx reduction and doping are two ubiquitous reactions in academic research and industrial manufacturing, but they are notoriously energy-demanding and require harsh conditions (high temperatures, long durations). In this work, facilitated by mechanochemical ball milling, we report a new route to conduct MOx reduction and doping at room temperature within 20 minutes enabled by mechanochemical ball milling and lithium metal.
On the coordination chemistry of triazolyl‐substituted diborane ligands, prepared by1,3‐dipolar cycloaddition reactions between diazido‐diboranes and alkynes
Metal-free cycloaddition reactions between a diazido-diborane and alkynes are used to synthesize new ditriazolyl-diborane molecules, a bis(ferrocenyl-1,2,3-triazolyl)-diborane and a bis(2-pyridyl-1,2,3-triazolyl)-diborane. Then, the bis(2-pyridyl-1,2,3-triazolyl)-diborane was used as polydentate ligand for the synthesis of larger architectures. Reaction with ditriflato-diborane yielded a tetracationic hexaboron compound, and reaction with metal salts yielded dicationic ring compounds with two hexacoordinate metal atoms and two integrated diborane units.
Synthetic approaches towards peptide‐conjugates of Pt(II) compounds with an (O,S) chelating moiety
Metal-containing peptide (bio-)conjugates have received continuous interest due to their enormous potential for bioinorganic and medicinal research. In many bioconjugates the chemical inertness of the metal-containing units facilitates synthesis e.g. by copper-catalyzed alkyne-azide cycloaddition or the formation of peptide bonds. However, when the metal complex contains labile ligands, which are often critical to their biological activity, the synthetic proceeding requires careful planning. Here, we report on the synthesis of a set of peptide bioconjugates with a platinum(II) core, coordinated through widely variable (O,S) chelating β-hydroxydithiocinnamic ester and two monodentate ligands. We have evaluated the synthetic applicability of metal-peptide bioconjugation techniques between the model peptide Leu5-enkephalin and differently functionalized (O,S)Pt units. Within this, the type and position of anchor used at the β-hydroxydithiocinnamic unit proved to be crucial for success, but equally important was the synthetic order of conjugation and complexation.
Phospholipase D Immobilization on Lignin Nanoparticles for Enzymatic Transformation of Phospholipids
Lignin nanoparticles (LNPs) are promising components for various materials, given their controllable particle size and spherical shape. However, their origin from supramolecular aggregation has limited the applicability of LNPs as recoverable templates for immobilization of enzymes. In this study, we show that stabilized LNPs are highly promising for the immobilization of phospholipase D (PLD), the enzyme involved in the biocatalytic production of high-value polar head modified phospholipids of commercial interest, phosphatidylglycerol, phosphatidylserine and phosphatidyl-ethanolamine. Starting from hydroxymethylated lignin, LNPs were prepared and successively hydrothermally treated to obtain c-HLNPs with high resistance to organic solvents and a wide range of pH values, covering the conditions for enzymatic reactions and enzyme recovery. The immobilization of PLD on c-HLNPs (PLD-c-HLNPs) was achieved through direct adsorption. We then successfully exploited this new enzymatic preparation in the preparation of pure polar head modified phospholipids with high yields (60-90%). Furthermore, the high PLD-c-HLNPs stability allows its recycling for a number of reactions with appreciable maintenance of its catalytic activity. Thus, PLD-c-HLNPs can be regarded as a new, chemically stable, recyclable and user-friendly biocatalyst, based on a biobased inexpensive scaffold, to be employed in sustainable chemical processes for synthesis of value-added phospholipids.
Design of 3‐phenylcoumarins and 3‐thienylcoumarins as potent xanthine oxidase inhibitors: synthesis, biological evaluation and docking studies
Coumarin scaffold has proven to be promising in the development of bioactive agents, such as xanthine oxidase (XO) inhibitors. Novel hydroxylated 3-arylcoumarins were designed, synthesized, and evaluated for their XO inhibition and antioxidant properties. 3-(3’-Bromophenyl)-5,7-dihydroxycoumarin (compound 11) proved to be the most potent XO inhibitor, with an IC50 of 91 nM, being 162 times better than allopurinol, one of the reference controls. Kinetic analysis of compound 11 and compound 5 [3-(4’-bromothien-2’-yl)-5,7-dihydroxycoumarin], the second-best compound within the series (IC50 of 280 nM), has been performed, and both compounds showed a mixed-type inhibition. Both compounds present good antioxidant activity (ability to scavenge ABTS radical) and are able to reduce reactive species oxygen (ROS) levels in H2O2-treated cells. In addition, they proved to be non-cytotoxic in a Caco-2 cells viability assay. Molecular docking studies have been carried out to correlate the compounds’ theoretical and experimental binding affinity to the XO binding pocket.
An Indacenopicene‐based Buckybowl Catcher for Recognition of Fullerenes
A novel buckybowl catcher with an extended π-surface has been synthesized via cross-coupling of two bowl shaped bromoindacenopicene moieties with a tolyl linker. The obtained catcher has been unambiguously characterized by 2D-NMR and mass spectrometry. DFT calculations indicate that the curved shape of the receptor moieties is favourable for binding fullerenes. Effective binding was confirmed for interactions with C60 and C70 utilizing NMR spectroscopy and isothermal titration calorimetry (ITC). The resulting binding values show a higher affinity of the catcher towards C70 over C60. The designed catcher demonstrated the fundamental possibility of creating sensors for spherical aromaticity.
Electron paramagnetic resonance, electronic ground state, and electron spin relaxation of seven lanthanide ions bound to lanmodulin and the bioinspired chelator, 3,4,3‐LI(1,2‐HOPO)
The electron paramagnetic resonance (EPR) spectra of lanthanide(III) ions besides Gd(III), bound to small-molecule and protein chelators, are uncharacterized. Here, we systematically investigated the EPR properties of 7 lanthanide(III) ions bound to the natural lanthanide-binding protein, lanmodulin (LanM), and the synthetic small-molecule chelator, 3,4,3-LI(1,2-HOPO) (“HOPO”). Echo-detected pulsed EPR spectra reveal intense signals from ions for which the normal continuous-wave first-derivative spectra are negligibly different from zero. Spectra of Kramers lanthanide ions Ce3+, Nd3+, Sm3+, Er3+, and Yb3+, and non-Kramers Tb3+ and Tm3+, bound to LanM are more similar to the ions in dilute aqueous:ethanol solution than to those coordinated with HOPO. Lanmodulins from two bacteria, with distinct metal-binding sites, had similar spectra for Tb3+ but different spectra for Nd3+. Spin-echo dephasing rates (1/Tm) are faster for lanthanides than for most transition metals and limited detection of echoes to temperatures below ~6 to 12 K. Dephasing rates were environment dependent and decreased in the order water:ethanol > LanM > HOPO, which is attributed to decreasing librational motion. Our results demonstrate that the EPR spectra and relaxation times of lanthanide(III) ions are sensitive to coordination environment, motivating wider application of these methods for characterization of both small-molecule and biomolecule interactions with lanthanides.