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Here we developed a new family of Zn-containing magnetic oxides of different structures by thermal decomposition of Zn(acac)2 in the reaction solution of preformed magnetite nanoparticles (NPs) stabilized by polyphenylquinoxaline. Upon an increase of the Zn(acac)2 loading from 0.15 to 0.40 mmol (vs 1 mmol of Fe(acac)3), the Zn content increases, and the Zn-containing magnetic oxide NPs preserve a spinel structure of magnetite and an initial, predominantly multicore NP morphology. X-ray photoelectron spectroscopy (XPS) of these samples revealed that the surface of iron oxide NPs is enriched with Zn, although Zn species were also found deep under the iron oxide NP surface. For all the samples, XPS also demonstrates the atom ratio of Fe(3+)/Fe(2+) = 2:1, perfectly matching Fe3O4, but not ZnFe2O4, where Fe(2+) ions are replaced with Zn(2+). The combination of XPS with other physicochemical methods allowed us to propose that ZnO forms an ultrathin amorphous layer on the surface of iron oxide NPs and also diffuses inside the magnetite crystals. At higher Zn(acac)2 loading, cubic ZnO nanocrystals coexist with magnetite NPs, indicating a homogeneous nucleation of the former. The catalytic testing in syngas conversion to methanol demonstrated outstanding catalytic properties of Zn-containing magnetic oxides, whose activities are dependent on the Zn loading. Repeat experiments carried out with the best catalyst after magnetic separation showed remarkable catalyst stability even after five consecutive catalytic runs.

For the first time we report syntheses of a family of functional polyphenylenepyridyl dendrons with different generations and structures such as focal groups, periphery, and a combination of phenylene and pyridyl moieties in the dendron interior using a Diels−Alder approach and a divergent method. The dendron structure and composition were confirmed using NMR spectroscopy, MALDI-TOF mass spectrometry, FTIR, and elemental analysis. As a proof of concept that these dendrons can be successfully used for the development of nanocomposites, synthesis of iron oxide nanoparticles was carried out in the presence of thermally stable dendrons as capping molecules followed by formation of Pd NPs in the dendron shells. This resulted in magnetically recoverable catalysts exhibiting exceptional performance in selective hydrogenation of dimethylethynylcarbinol (DMEC) to dimethylvinylcarbinol (DMVC).

The A6 + B2 approach to hyperbranched polymers based on the dendrimer (A6) as a multifunctional monomer and bis(cyclopentadienone)s (B2) holds promise for the one-pot synthesis of well-defined polymers with perfect dendritic fragments in the backbone.

We report the formation of multicore iron oxide mesocrystals using the thermal decomposition of iron acetyl acetonate in the presence of the multifunctional and rigid poly(phenylenepyridyl) dendron and dendrimer. We thoroughly analyze the influence of capping molecules of two different architectures and demonstrate for the first time that dendron/dendrimer self-assembly leads to multicore morphologies. Single-crystalline ordering in multicore NPs leads to cooperative magnetic behavior: mesocrystals exhibit ambient blocking temperatures, allowing subtle control over magnetic properties using a minor temperature change.

A new family of Ni-, Co-, and Cr-doped Zn-containing magnetic oxide nanoparticles (NPs) stabilized by polyphenylquinoxaline (PPQ) and hyperbranched pyridylphenylene polymer (PPP) has been developed. These NPs have been synthesized by thermal decomposition of Zn and doping metal acetylacetonates in the reaction solution of preformed magnetite NPs, resulting in single-crystal NPs with spinel structure. For the PPQ-capped NPs, it was demonstrated that all three types of metal species (Fe, Zn, and a doping metal) reside within the same NPs, the surface of which is enriched with Zn and a doping metal, while the deeper layers are enriched with Fe. The Cr-doped NPs at the high Cr loading are an exception due to favored deposition of Cr on magnetite located in the NP depth. The PPP-capped NPs exhibit similar morphology and crystallinity; however, the detailed study of the NP composition was barred due to the high PPP amount retained on the NP surface. The catalyst testing in syngas conversion to methanol demonstrated outstanding catalytic properties of doped Zn-containing magnetic oxides, whose activities are dependent on the doping metal content and on the stabilizing polymer. The PPP stabilization allows for better access to the catalytic species due to the open and rigid polymer architecture and most likely optimized distribution of doping species. Repeat experiments carried out after magnetic separation of catalysts from the reaction mixture showed excellent catalyst stability even after five consecutive catalytic runs.

Here we report control of iron oxide and palladium nanoparticle (NP) formation via stabilization with polyphenylenepyridyl dendrons of the second and third generations with dodecyl periphery. These nanomaterials are developed as magnetically recoverable catalysts. To accurately assess the influence of the dodecyl exterior for the same dendron generation, we also designed a second generation dendron with partial dodecyl periphery. For all dendrons studied, the multicore iron oxide mesocrystals were formed, the sizes and morphology of which were controlled by the dendron generation. Analysis of the static and dynamic magnetic properties, in combination with transmission electron microscopy observations, demonstrate that magnetism is sensitive on the structure-directing capabilities of the type of the dendron which was employed for the mesocrystal stabilization. Close proximity of single cores in such multicore mesocrystals promotes the coupling of the neighboring magnetic moments, thus boosting their magnetization and allowing easy crossover between superparamagnetic and ferrimagnetic behaviors at room temperature. The particularly dramatic role of the dendron structure was also witnessed via the Pd NP formation, which was found to depend on both the dendron generation and its dodecyl periphery. In the case of the catalyst based on the second generation dendron with full dodecyl periphery, no Pd NPs were observed by TEM indicating that these species are of a subnanometer size and are not visible on or near the iron oxide NPs. For the catalyst based on the second generation dendron with partial dodecyl periphery, hydrogen reduction leads to much larger Pd NPs (2.7 nm) due to an unimpeded exchange of Pd species between dendrons and nondense dendron coating with asymmetrical dendrons. The third generation dendron with full dodecyl periphery allows nearly monodisperse 1.2 nm Pd NPs in the shells of iron oxide mesocrystals and the best catalytic properties in selective hydrogenation of dimethylethynylcarbinol. This study suggests a robust approach to control NP formation in magnetically recoverable catalysts for a wide variety of catalytic reactions using dendrons combining rigidity and flexibility in one molecule.

Water-soluble cationic polypyridylphenylene dendrimers (wPPPDs) of different generations and various contents of pyridyl and phenylene moieties were synthesized. Interaction of wPPPDs with DNA resulted in the formation of polyelectrolyte complexes stable at physiological pH and ionic strength. Noticeable contribution of hydrophobic interactions provided by phenylene groups of the dendrimer in the complex stability was ascertained. Data obtained by turbidimetry and a sedimentation assay, as well as ζ-potential measurements, strongly implied the inaccessibility of positively charged pyridinium groups situated in the inner part of the dendrimer molecules for interaction with the rigid double helix. Positively and negatively charged water-soluble nonstoichiometric polyelectrolyte complexes were prepared and phase separations in their water-salt solutions were investigated. According to DLS measurements supported by the sedimentation assay, the addition of wPPPD in DNA solution in a wide range of the mixture composition (before phase separation) led to two coexisting populations of nanoparticles related to the soluble DNA/ wPPPDs complex and practically unbound DNA. The revealed spontaneous formation of nanoparticles of the positively charged soluble DNA/wPPPDs complexes stable at ionic strength close to the physiological one is extremely encouraging for the development of the wPPPD vehicle to deliver gene materials to the cell.