Ulrich Ziener

Supramolecular Assemblies of a Bis(terpyridine) Ligand and of its [2×2] Grid-type ZnII and CoII Complexes on Highly Ordered Pyrolytic Graphite

The synthesis and characterisation of bis(terpyridine)-derived ligands which are capable of forming [2x2] grid-like complexes is presented. Additional pyridine substituents on these ligands do not interfere with the complexation process. Adsorbing one of the pure ligands on highly ordered pyrolytic graphite (HOPG) shows a highly ordered structure stabilised by additional weak intermolecular C-H...N hydrogen bonds partially through the extra-pyridines as could be shown by scanning tunneling microscopy (STM) investigations. Similar adsorption experiments with one of the corresponding [2x2] Co(II) grid-type complexes on graphite, led also to a well-organised structure with interdigitation of the extra-pyridine moieties.

Pickering-type stabilized nanoparticles by heterophase polymerization

The preparation of nanoparticles in a soap-free system is highly attractive, as surfactants may influence and deteriorate subsequent applications. Thereby, the assembly of solid particles on droplets/particles is well known as Pickering-type stabilization. The resulting hybrid nanocomposites offer in general a rough surface and are highly intriguing for potential drug delivery systems, coating applications, and so forth. This review highlights developments in production and application of Pickering-type nanoparticles synthesized via heterophase polymerization techniques in emulsion, miniemulsion, dispersion, and suspension. We will focus our discussion on systems, wherein stabilization of the final nanometer-sized hybrids is exclusively accomplished via particle stabilizers. In case surfactants are used during preparation, they only serve as pre-treating agents to modify the surface properties of the particle stabilizer, and not being employed for the purpose of droplet/particle stabilization.

Synthesis and optimization of gelatin nanoparticles using the miniemulsion process

A convenient synthetic route based on the concept of nanoreactors using the versatility of the miniemulsion technique to synthesize glutardialdehyde cross-linked gelatin nanoparticles with tailored properties is reported. It is demonstrated that, independent of the molecular weight distribution of the gelatin used, stable nanoparticles can be produced with a small amount of surfactant. The amount of gelatin and the cross-linking degree in the particle can be well controlled. Different types of gelatin have been used without purification or fractionation. The stability of the dispersion, particle size, and the efficiency of cross-linking have been studied. Such nanoparticles with varying gelatin concentration and cross-linking density have high potential to be used for drug delivery applications, as nanoenvironment or template for synthesizing inorganic materials.

Two-Level Self-Organisation of Arrays of [2×2] Grid-Type Tetranuclear Metal Complexes by Hydrogen Bonding

Here we report on the synthesis and characterisation of four new complexes of the [2×2] M4II grid-type (M = Co, Fe, Zn) with oligopyridine-derived ligands. The presence of aminopyrazine and aminopyrimidine moieties at the edge of the ligands potentially enables the formation of infinite hydrogen-bonded multi-grid networks. The ligands were synthesised by subsequent stannylations and Stille-type coupling reactions. The complexes were obtained by self-assembly of the ligand with the metal salt. The single-crystal X-ray structure was determined for the Co complex 7 containing aminopyrimidine as the hydrogen-bonding moiety [P1¯; a = 15.4976(4), b = 18.2114(6), c = 31.9538(10) A, α = 86.9809(13), β = 83.4137(18), γ = 67.2828(16)°]. The crystal structure reveals hydrogen bonding in one direction, thus forming infinite chains of grids, whereas in the second direction of a layer, only weak attractive interactions are found. Anions and solvent molecules are situated between the layers, thus inhibiting any direct interaction between them. Cocrystallisation of the complementary complexes should enable the recognition-controlled alternating arrangement of grids incorporating different metal ions in a chessboard-like manner.

Recognition‐Directed Supramolecular Assemblies of Metal Complexes of Terpyridine Derived Ligands with Self‐Complementary Hydrogen Bonding Sites

The synthesis and X-ray structures of three metal complexes with terpyridine-derived ligands that contain amino-pyrimidine and amino-pyrazine moieties are presented. They have been designed in view of directing their self-assembly into specific supramolecular arrays through molecular recognition interactions. The solid-state structures indeed reveal extensive hydrogen-bonded networks. The Co complex 4a with PF6- counterions builds a two-dimensional infinite interwoven grid through strong double hydrogen bonds (d(N-H-N) =2.918-3.018 A) between the amino groups and the N atoms of the rings, with all H-bonding sites saturated. Changing the anions to BF4- in 4b leads to a similar infinite but partially broken grid with a quarter of the H-bonding sites unsaturated (d(N-H-N)=2.984-3.206 A). In the case of the Zn complex 12 with triflate anions, half of the hydrogen bonds are formed. Only one of the two orthogonal ligands has hydrogen bonds (d(N-H-N) = 3.082, 3.096 A) to the neighbouring complexes and thus builds linear, supramolecular, polymeric chains. These structural differences are mainly attributed to crystal-packing effects caused by the different anions. The data presented here may also be regarded as a prototype for the generation of organised arrays through sequential self-assembly processes.

Recent advances in the preparation of hybrid nanoparticles in miniemulsions.

In this review, we summarize recent advances in the synthesis of hybrid nanoparticles in miniemulsions since 2009. These hybrid nanoparticles include organic-inorganic, polymeric, and natural macromolecule/synthetic polymer hybrid nanoparticles. They may be prepared through encapsulation of inorganic components or natural macromolecules by miniemulsion (co)polymerization, simultaneous polymerization of vinyl monomers and vinyl-containing inorganic precursors, precipitation of preformed polymers in the presence of inorganic constituents through solvent displacement techniques, and grafting polymerization onto, from or through natural macromolecules. Characterization, properties, and applications of hybrid nanoparticles are also discussed.

Preparation of Raspberry-like Nanocapsules by the Combination of Pickering Emulsification and Solvent Displacement Technique

Well-defined raspberry-like nanocapsules were prepared by the combination of Pickering emulsification and solvent displacement technique by using silica particles as stabilizer and hexadecane (HD) as soft template. The formation of the capsule morphology is caused by the phase separation of poly(styrene-co-4-vinyl pyridine) (poly(St-co-4-VP)) in the droplets due to the diffusion of good solvent for the (co)polymer to the aqueous continuous phase. The size of capsules was successfully reduced from tens of micrometers in the dispersion by simply stirring to the nanorange by the employment of sonication and Ostwald ripening. The formation of silica-particles-armored nanocapsules was confirmed by transmission electron microscopy (TEM), high-resolution scanning electron microscopy (HRSEM), dynamic light scattering (DLS), and zeta potential measurement. The colloidal stability and particle properties, including size and morphology, depend on the amount of HD, and copolymers, the sonication time, the dispersion pH value, the type of solvent, and the copolymer composition.

Solution-Processable Septithiophene Monolayer Transistor

Septithiophene with endgroups designed to form liquid crystalline phases and allows controlled deposition of an electrically connected monolayer. Field effect mobilies mobilities of charge carriers and spectroscopic properties of the monolayer provide evidence of sustainable transport and delocalization of the excitation through intermolecular interactions within the layer.

Preparation of Mesoporous Submicrometer Silica Capsules via an Interfacial Sol–Gel Process in Inverse Miniemulsion

Mesoporous silica capsules with submicrometer sizes were successfully prepared via the interfacial hydrolysis and condensation reactions of tetraethoxysilane (TEOS) in inverse miniemulsion by using hydrophilic liquid droplets as template. The inverse miniemulsions containing pH-controlled hydrophilic droplets were first prepared via sonication by using poly(ethylene-co-butylene)-b-poly(ethylene oxide) (P(E/B)-PEO) or SPAN 80 as surfactant. TEOS was directly introduced to the continuous phase of an inverse miniemulsion. The silica shell was formed by the deposition of silica on the surface of droplets. The formation of capsule morphology was confirmed by transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). The mesoporous structure was verified by nitrogen sorption measurements. The specific surface area could be tuned by the variation of the amount of cetyltrimethylammonium bromide (CTAB) and TEOS, and the pore size by the amount of CTAB. The influences of synthetic parameters on the particle size and morphology were investigated in terms of the amount of CTAB, pH value in the droplets, TEOS amount, surfactant amount, and type of solvent with low polarity. A formation mechanism of silica capsules was proposed.

Iron octaphenyltetraazaporphyrins: synthesis and characterization of the five-coordinate complexes of iron(III) (XFeIIIOPTAP; X=F, Cl, Br, I, HSO4)

Abstract Five-coordinate complexes of iron with octaphenyltetraazaporphine (H2OPTAP) containing halide or hydrosulfate as an axial acido-ligand (XFeIIIOPTAP; X=F, Cl, Br, I, HSO4) have been synthesized by treatment of the μ-oxo dimer, O(FeIIIOPTAP)2, or of the anionic dihydroxo complex [(HO)2FeIIIOPTAP]− with the corresponding acid HX. UV-Vis, IR, 1H NMR and Mossbauer spectroscopy methods and magnetic susceptibility measurements have been used for the characterization of these complexes. Magnetic moment (μeff=3.44 for chloro and 2.98 for bromo complex at r.t.), Mossbauer parameters (δFe=0.24−0.29 mm s−1 and ΔEQ=2.8-3.6 mm s−1 at 82 K) and the character of the paramagnetic shifts of the phenyl proton resonances (o-Ph 5.4–6.1 ppm, m-Ph 10.6–11.6 ppm and p-Ph 3.1–3.5 ppm in CHCl3 at r.t.) are consistent with an intermediate spin state ( S= 3 2 ) of iron in these complexes. The origin of the absorption bands in the UV-Vis and IR spectra is discussed and their assignment is proposed. A comparison with the corresponding five-coordinate complexes of porphyrins and phthalocyanine is made.