[Co(TPP)]-Catalyzed Formation of Substituted Piperidines

Radical cyclization via cobalt(III)-carbene radical intermediates is a powerful method for the synthesis of (hetero)cyclic structures. Building on the recently reported synthesis of five-membered N-heterocyclic pyrrolidines catalyzed by Co^II porphyrins, the [Co(TPP)]-catalyzed formation of useful six-membered N-heterocyclic piperidines directly from linear aldehydes is presented herein. The piperidines were obtained in overall high yields, with linear alkenes being formed as side products in small amounts. A DFT study was performed to gain a deeper mechanistic understanding of the cobalt(II)-porphyrin-catalyzed formation of pyrrolidines, piperidines, and linear alkenes. The calculations showed that the alkenes are unlikely to be formed through an expected 1,2-hydrogen-atom transfer to the carbene carbon. Instead, the calculations were consistent with a pathway involving benzyl-radical formation followed by radical-rebound ring closure to form the piperidines. Competitive 1,5-hydrogen-atom transfer from the β-position to the benzyl radical explained the formation of linear alkenes as side products.     

Generation of molecular diversity using a complexity-generating MCR-platform towards triazinane diones

Triazinane diones, readily generated by a recently reported multicomponent reaction, can be easily alkylated with various alkyl halides, allowing a wide variety of complexity-generating secondary reactions. Because of the high variability of the initial multicomponent reactions and the multiple possibilities for participation of substituents in the secondary reactions, a highly diverse set of complex products was obtained in short and efficient reaction sequences.     

Generalized Rouse model for a dilute solution of clustered polymers

A theory analogue to tha of Rouse is given, to describe the rheological behavior of dilute solutions consisting of clusters of crosslinked polymers. The frequency-dependent behavior of the dynamic moduli of these fluids differs substantially from that of the well-known Rouse-like fluid (GG^1/2). In our case the storage modulus becomes proportional to ^3/2, while the loss modulus is proportional to . The loss modulus dominates the dynamic behavior for frequencies smaller than the largest normal frequency of the clusters.     

Characterization of Defined Metal‐Containing Supramolecular Block Copolymers

The characterization of metal‐containing supramolecular polymers by gel permeation chromatography (GPC) or matrix‐assisted laser desorption ionisation time‐of‐flight mass spectrometry (MALDI‐TOF MS) is complicated because of the interaction of the charged materials with the GPC column material in the first case and fragmentation due to the applied laser energy in the latter case. In this contribution we report recent advances made for the characterization of supramolecular polymers based on terpyridine metal complexes utilizing GPC and MALDI‐TOF MS. In particular for GPC analysis, the choice of solvent and additive was found to be crucial for a successful characterization. Furthermore, MALDI‐TOF MS spectra of these compounds are not straightforward to interpret. Both aspects are discussed in detail with the result of a better understanding and improved analysis possibilities of the mentioned supramolecular polymers.

A GPC‐coupled in‐line diode array spectrum of one of the complexes investigated here.     

Synthesis and thermal properties of diblock copolymers utilizing non-covalent interactions

Diblock copolymers of poly(styrene) and poly(ethylene oxide) were prepared utilizing a bisterpyridine ruthenium complex as non-covalent interaction for the connection of the two blocks. Apart from the synthesis and characterization of four metallo-supramolecular block copolymers, first studies on the thermal properties of the block copolymers have been performed. A complex crystallization behavior was observed and is described in a qualitative fashion. The influence of the metal complex on the thermal stability of the metallo-supramolecular block copolymers remains a question for further investigation.