Nicolai D. Knöfel

Platinum(II)-Crosslinked Single-Chain Nanoparticles: An Approach towards Recyclable Homogeneous Catalysts

We introduce the synthesis and in-depth characterization of platinum(II)-crosslinked single-chain nanoparticles (PtII -SCNPs) to demonstrate their application as a recyclable homogeneous catalyst. Specifically, a linear precursor copolymer of styrene and 4-(diphenylphosphino)styrene was synthesized via nitroxide-mediated polymerization. The triarylphosphine ligand moieties along the backbone allowed for the intramolecular crosslinking of single chains via the addition of [Pt(1,5-cyclooctadiene)Cl2 ] in dilute solution. The successful formation of well-defined PtII -SCNPs was evidenced by size exclusion chromatography, dynamic light scattering, nuclear magnetic resonance (1 H, 31 P{1 H}, 195 Pt), and diffusion-ordered spectroscopy. Finally, the activity of the PtII -SCNPs as homogeneous, yet recyclable catalyst was successfully demonstrated using the example of the amination of allyl alcohol.

Single-Chain Nanoparticles as Catalytic Nanoreactors

The need for efficient, tailor-made catalysts has inspired chemists to fuse the design principles of natural enzymes with synthetic macromolecular architectures. A highly interesting pathway mimics a metallo-enzymes tertiary structure via the target placement of metal-ions in a tailor-made polymeric framework, resulting in catalytically active single-chain nanoparticles. Initial studies reveal unusual and promising effects, regarding both new catalyst characteristics and a high impact on product formation. These multifunctional nanoreactors, constructed from simple folded polymer chains, will lead to advanced bioinspired catalytic systems. As found in enzymes, their impact lies specifically within the defined construction of a polymeric pocket around the catalytic active cores for substrate recognition.

Dimolybdenum Paddlewheel as Scaffold for Heteromultimetallic Complexes: Synthesis and Photophysical Properties

A diphenylphosphine functionalized benzoic acid was applied for the synthesis of a homoleptic dimolybdenum-based metalloligand, exhibiting four symmetrically placed phosphine donor sites. This allowed subsequent treatment with gold(I), rhodium(I), and iridium(I) precursors to obtain early-late heterometallic complexes as well as Lewis acid-base adducts with BH3. The compounds were in-depth investigated by spectroscopic techniques, single-crystal X-ray diffraction, and femtosecond laser spectroscopy. The coordination of different metal fragments to the dimolybdenum metalloligand leads to a fine-tuning of the systems optical properties, which correlates well with fluorescence quantum yield measurements. Nevertheless, triplet dynamics still remain the dominating channel in these systems with an intersystem crossing time constant below 1 ps.