Mn(III) porphyrins immobilized on magnetic polymer nanospheres as biomimetic catalysts hydroxylating cyclohexane with molecular oxygen

Structural Regulation of Magnetic Polymer Microsphere@Ionic Liquids with an Intermediate Protective Layer and Application as Core-Shell-Shell Catalysts with High Stability and Activity

A novel ionic liquid immobilized on a magnetic polymer microsphere catalyst is reported in this paper. The obtained core-shell-shell catalyst consisted of magnetic nanoparticles (MNPs) as the core, catalytic inert St-co-DVB as the intermediate protective layer, and cross-linked polyaryl imidazole ionic liquids as the active catalytic layer located at the outermost [Im[OH]/MNPs@P(St-DVB)@P(VBC-DVB)]. This catalyst exhibited a high ion-exchange rate (64.65%), high saturation magnetic strength, and excellent acid and alkali corrosion resistance. In the catalyzed Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate, the conversion of benzaldehyde maintained at 92.1% during six times reuse. Optimizing the materials of the protective layer and regulating the thickness of the inert protective layer decreased the corrosion ratio of MNPs in acidic media from 44.82 to 0.44%. Adjusting the thickness of the catalytic layer realized excellent catalytic activity (97%) and high magnetic response performance. In summary, introducing an inert protective layer to the structure of ionic liquids immobilized on the magnetic polymer microsphere catalyst, regulating its thickness, and optimizing its structure achieved a catalyst with high activity, excellent stability, and easy magnetic separation.

Dynamic, multimodal hydrogel actuators using porphyrin-based visible light photoredox catalysis in a thermoresponsive polymer network

Hydrogels that can respond to multiple external stimuli represent the next generation of advanced functional biomaterials. Here, a series of multimodal hydrogels were synthesized that can contract and expand reversibly over several cycles while changing their mechanical properties in response to blue and red light, as well as heat (∼50 °C). The light-responsive behavior was achieved through a photoredox-based mechanism consisting of photoinduced electron transfer from a zinc porphyrin photocatalyst in its excited state to oligoviologen-based macrocrosslinkers, both of which were integrated into the hydrogel polymer network during gel formation. Orthogonal thermoresponsive properties were also realized by introducing N-isopropyl acrylamide (NIPAM) monomer simultaneously with hydroxyethyl acrylate (HEA) in the pre-gel mixture to produce a statistical 60 : 40 HEA : NIPAM polymer network. The resultant hydrogel actuators - crosslinked with either a styrenated viologen dimer (2V4+-St) or hexamer (6V12+-St) - were exposed to red or blue light, or heat, for up to 5 h, and their rate of contraction, as well as the corresponding changes in their physical properties (i.e., stiffness, tensile strength, Young's modulus, etc.), were measured. The combined application of blue light and heat to the 6V12+-St-based hydrogels was also demonstrated, resulting in hydrogels with more than two-fold faster contraction kinetics and dramatically enhanced mechanical robustness when fully contracted. We envision that the reported materials and the corresponding methods of remotely manipulating the dynamic hydrogels may serve as a useful blueprint for future adaptive materials used in biomedical applications.

The synthesis, characterization and catalytic application of manganese porphyrins bonded to novel modified SBA-15

In the presented research, a highly ordered mesoporous silica material (SBA-15) was functionalized with imidazole as a functionalizing reagent (SBA-TMSIm) and then characterized via FT-IR spectroscopy, thermogravimetric analysis (TGA), powder X-ray diffraction (XRD) and nitrogen adsorption/desorption isotherms.

Highly recyclable and magnetic catalyst of a metalloporphyrin-based polymeric composite for cycloaddition of CO2to epoxide

A highly recyclable and magnetic catalyst made of a metalloporphyrin-based polymeric composite efficiently promotes chemical fixation of CO₂to cyclic carbonate.

Preparation and characterization of novel magnetic nanocomposite-bonded metalloporphyrins as biomimetic nanocatalysts

In this work, novel magnetic nanocomposite-bonded metalloporphyrins were synthesized by an effective silanation approach between 3-aminopropyltriethoxysilane derivatized metalloporphyrins and silica-coated magnetic Fe3O4 nanoparticles. The initial metalloporphyrin derivatives were synthesized by the amidation reaction of metalloporphyrin acyl chloride with 3-aminopropyltriethoxysilane. After the metalloporphyrin derivatives were adsorbed on the surface of silica-coated magnetic Fe3O4 nanoparticles, the solid mixture was heated under vacuum at 110 °C for 3 h and then thoroughly washed with chloroform. The obtained magnetic nanocomposite-bonded metalloporphyrins were characterized by elemental analyzer, low-temperature N2 adsorption (BET method), transmission electron microscopy, UV-vis spectroscopy, and infrared spectroscopy. Interestingly, using this particular silanation method, metalloporphyrins could be quantitative-immobilized in magnetic nanocomposites by controlling the input ratio of metalloporphyrins and silica-coated magnetic Fe3O4 nanoparticles. The excellent catalytic activity and recyclability of the magnetic nanocomposite-bonded metalloporphyrins were demonstrated in the cyclohexane oxidation with iodosylbenzene.

{meso-Tetra-kis[p-(hept-yloxy)phen-yl]-porphyrinato}silver(II)

The title compound, [Ag(C₇₂H₈₄N₄O₄)], crystallizes with the Ag^II cation on a centre of symmetry. The macrocyclic 24-membered ring core is planar with a mean deviation of 0.0311 (15) Å and the four-coordinate Ag^II cation fits into its center, at 2.0814 (19) and 2.0872 (19) Å, from the surrounding pyrrole-N atoms, in agreement with what is found in related compounds. The p-heptyl­oxyphenyl groups are rotated 75.51 (5) and 84.45 (8)° with respect to the porphyrin mean plane, due to steric hindrance with the pyrrole-H atoms of the macrocycle.

Manganese Kβ X-ray emission spectroscopy as a probe of metal-ligand interactions

A systematic series of high-spin mononuclear Mn(II), Mn(III), and Mn(IV) complexes has been investigated by manganese Kβ X-ray emission spectroscopy (XES). The factors contributing to the Kβ main line and the valence to core region are discussed. The Kβ main lines are dominated by 3p-3d exchange correlation (spin state) effects, shifting to lower energy upon oxidation of Mn(II) to Mn(III) due to the decrease in spin state from S = 5/2 to S = 2, whereas the valence to core region shows greater sensitivity to the chemical environment surrounding the Mn center. A density functional theory (DFT) approach has been used to calculate the valence to core spectra and assess the contributions to the energies and intensities. The valence spectra are dominated by manganese np to 1s electric dipole-allowed transitions and are particularly sensitive to spin state and ligand identity (reflected primarily in the transition energies) as well as oxidation state and metal-ligand bond lengths (reflected primarily in the transition intensities). The ability to use these methods to distinguish different ligand contributions within a heteroleptic coordination sphere is highlighted. The similarities and differences between the current Mn XES study and previous studies of Fe XES investigations are discussed. These findings serve as an important calibration for future applications to manganese active sites in biological and chemical catalysis.

Performance of a biomimetic oxidation catalyst immobilized on silicon wafers: comparison with its gold congener

With the aim of extending the usefulness of an existing biomimetic catalytic system, cobalt porphyrin catalytic units with thiol linkers were heterogenized via chemical grafting to silicon wafers and utilized for the catalytic oxidation of hydroquinone to p-benzoquinone. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to analyze the morphology and composition of the heterogeneous catalyst. The results of the catalytic oxidation of hydroquinone obtained with porphyrins grafted on silicon were compared with those obtained earlier with the same catalyst in homogeneous phase and immobilized on gold. It was found that the catalysis could run over 400 h, without showing any sign of deactivation. The measured catalytic activity is at least 10 times higher than that measured under homogeneous conditions, but also 10 times lower than that observed with the catalytic unit immobilized on gold. The reasons of this discrepancy are discussed in term of substrate influence and overlayer organization. The silicon-immobilized catalyst has potential as an advanced functional material with applications in oxidative heterogeneous catalysis of organic reactions, as it combines long-term relatively high activity with low cost.