Coordination Polymer Nanostructures

Metal-Organic Gels Derived from Iron(III) and Pyridine Ligands: Morphology, Self-Healing and Catalysis for Ethylene Selective Dimerization

Metal-organic gels showing potential application in catalysis have received much concern. In this work, we designed and synthesized two metal-organic gels based on coordination between Fe^III and pyridine ligands at room temperature. The gels were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to reveal their assembly structures and morphologies, and it was found the metal-organic gel derived from di-topic ligand was composed of three-dimensional network of nanofibers, while the gel derived from tri-topic ligand was constituted of sponge-like structure with amorphous phase. Rheological analysis showed the gel consisting of nanofiber networks displayed self-healing property. The gels were used as catalysts for selective ethylene dimerization, and the optimum catalysis results of the gel with nanofibers reached the maximal catalytic activity of 1.48×10⁵  g/(mol Fe⋅h) with C₄ yield more than 90 %, whereas the sponge-like gel only gave 38 % C₄ products at the same condition. The higher dimerization selectivity of the former Fe^III gel was attributed to its regular assembly structure and lower steric hindrance of the surface metal sites. Due to its catalytic activity, high selectivity and preparation simplicity, the Fe^III gel might be potentially applicable for the preparation of C₄ α-olefins.

A metal-organic gel based on Fe(iii) and bi-pyridine ligand for template synthesis of core/shell composite polymer nanowires

In this study, a novel self-assembled metal-organic gel was synthesized from ferric nitrate and a di-topic ligand, bis(3-pyridyl)terephthalate. The gel consisted of a three dimensional network of uniform nanofibers. The gelation exhibited high selectivity to Fe(iii) based on metal-ligand coordination. The molar ratio of Fe3+ to ligand had a large influence on the assembly process and the morphology of the gel. The metallogel displayed multi-stimuli responsiveness and excellent heat resistance, thus was further applied as a thermo-stable template for the polymerization of N,N'-methylene bisacrylamide to produce the core/shell polymer composite nanowires. Subsequently, the polymer nanotubes were obtained after ammonia post-treatment, comfirming the feasibility of the template synthesis strategy. According to the rheological measurements, the gel-like products of the composite nanowires exhibited better mechanical strength compared to the gel template.

Tubular Hybrids: A Nanoparticle-Molecular Network

We report here a new methodology for the formation of freestanding nanotubes composed of individual gold nanoparticles (NPs) cross-linked by coordination complexes or porphyrin molecules using WS₂ nanotubes (INT-WS₂) as a template. Our method consists of three steps: (i) coverage of these robust inorganic materials with monodispersed and dense monolayers of gold NPs, (ii) formation of a molecular AuNP network by exposing these decorated tubes to solutions containing a ruthenium polypyridyl complex or meso-tetra(4-pyridyl)porphyrin, and (iii) removal of the INT-WS₂ template with a hydrogen peroxide solution. Nanoindentation of the template-free AuNP tubes with atomic force microscopy indicates a radial elastic modulus of 4 GPa. The template-free molecular AuNP tubes are characterized using scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, and micro-Raman spectroscopy. The methodology provides a convenient and scalable strategy for the realization of molecular AuNP tubes with a defined length and diameter, depending on the dimensions of the template.

Sonochemical synthesis and characterization of microrod to nanoparticle of new mixed-ligand zinc(II) fumarate metal-organic polymer

Micro and nano-structures of a new mixed-ligand Zn(II) fumarate metal-organic polymer, {[Zn(tptz)(fum)].DMF}_n (1), (tptz=2,4,6-tris(2-pyridyl)-s-triazine, fum=fumarate, DMF=N,N-dimethylforamide), were synthesized by sonochemical method. These new micro and nano-structures were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), IR spectroscopy and elemental analyses. Compound 1 was structurally characterized by single-crystal X-ray diffraction and consists of the primary unit of [Zn(tptz)(fum)]. Self assembly between the units of [Zn(tptz)(fum)] from Zn-O bonds results in the formation of a one-dimensional zinc(II) coordination polymer. The Zn^II-ion in compound 1 has ZnO₂N₃ coordination sphere with a trigonal bipyramidal molecular geometry. Compound 1 was synthesized by ultrasound irradiation under different concentrations and times. The microrods structure of compound 1 with increasing of concentration and ultrasound radiation time were synthesized as nanoparticles structure successfully. So ultrasound radiation change morphology from microrods to nanoparticles.

Tunable Self-Assembly and Morphology-Dependent Photoconductivity of a Donor-Acceptor-Structured Diruthenium Complex

A donor-acceptor-structured diruthenium complex, 1(PF₆)₄, that contains an electron-deficient bridging ligand and electron-rich distal diarylamines modified with long aliphatic chains has been synthesized. By varying the solvent environments and assembly conditions, we obtained three different self-assembled nanostructures of 1(PF₆)₄, including zero-dimensional nanospheres, one-dimensional nanofibers, and thin films with interconnected nanowire networks. These structures were investigated by scanning electron microscopy, transmission electron microscopy, dynamic light scattering, X-ray diffraction, and atomic force microscopy (AFM) analysis. Conductive AFM analysis shows that the nanowire networks exhibit a high conductivity of 0.023 S/cm and an enhanced photoconductivity of 0.59 S/cm under visible light irradiation.

Synthesis, characterization and in vitro anticancer activity of the biomolecule-based coordination complex nanotubes

Biomolecule-based coordination complex nanoassemblies are a new type of functional materials that are attracting increasing attention. They could possess functionalities that are not readily attainable with other materials, and represent a promising research area that can be exploited in coordination chemistry and materials science. Using bioactive folic acid molecule as a linker, Ni-folate-hydrazine coordination complex nanotubes (CCNTs) have been effectively constructed using the solvothermal method. This is not only the first example of the CCNTs being formed using a nonpyridyl-based molecule as a linker, but also the first report on biomolecule-based CCNTs (BMB-CCNTs) with anticancer activity. It does not require any post treatment to achieve targeted delivery and biocompatible performance. The BMB-CCNTs are sufficiently stable at normal pH of 7.4 until it enters a tumor cell, subsequently it breaks open to release drug in the tumor cell. Furthermore, it overcomes the major limitations of antibody-drug and folate-drug conjugates and is a potential smart multi-functional nanomedicine system. The results of in vitro cytotoxicity assay reveal that the antitumor ability of BMB-CCNTs is similar to cisplatin (CDDP), while their cytotoxicity for normal cells is lower than the latter. Furthermore, BMB-CCNTs exhibit excellent performance as drug carriers and target agents for delivering drugs into tumor cells. Bio-TEM and confocal laser scanning microscope images trace the uptake process of CDDP-CCNTs by a tumor cell. CDDP-CCNTs exhibit dual anti-cancer effect.