Mechanical Activation of Terpyridine Metal Complexes in Polymers

A Terpyridine Based 1,2,3-Triazol-1,4-diyl-Fluoroionophore-A Fluorometric Study Towards 3d Metal Ions in Acetonitrile

In this paper, we report on the sensing role of the 1,2,3-triazol unit in a 1,4-diyl arrangement in a fully π-conjugated fluorescent probe 1 (cf. Scheme 1) towards the fluorometric detection of 3d metal ions. The 1,2,3-triazol-1,4-diyl-fluoroionophore 1 was designed in a donor(D)-acceptor(A) arrangement with a 1,2,3-triazol unit as a π-linker between a terpyridine (A) ionophore and a diethylaminocoumarin (D) fluorophore to study the fluorescence behavior towards the divalent 3d metal ions Mn2+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+. This fluoroionophore 1 is based on an intramolecular charge transfer (ICT) and shows a moderate quantum yield (φf) of 0.508 in acetonitrile. A modulation of the ICT process in 1 through Fe2+, Co2+, Cu2+, Ni2+ and Zn2+ leads to a small red shift of the lowest energetically lying absorption UV/Vis absorption band and to a very strong 3d metal ion induced fluorescence quenching. It should be considered, that the installation of a 1,2,3-triazole unit as a fully π-linker in ICT probes originates no ratiometric fluorescence response towards Fe2+, Co2+, Cu2+, Ni2+ and Zn2+.

Synthesis and Characterization of Metallopolymer Networks featuring Triple Shape-Memory Ability Based on Different Reversible Metal Complexes

This study presents the synthesis and characterization of metallopolymer networks with a triple shape-memory ability. A covalently crosslinked polymer network featuring two different additional ligands in its side chains is synthesized via free radical polymerization (FRP). The subsequent addition of different metal salts leads to the selective formation of complexes with two different association constants (Ka), proven via isothermal titration calorimetry (ITC). Those two supramolecular crosslinks feature different activation temperatures and can act as two individual switching units enabling the fixation and recovery of two temporary shapes. The presented samples were investigated in a detailed fashion via differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and FT-Raman spectroscopy. Furthermore, thermo-mechanical analyses (TMA) revealed excellent dual and triple shape-memory abilities of the presented metallopolymer networks.

New pectin derivatives with antimicrobial and emulsification properties via complexation with metal-terpyridines

Pectin is widely used in food and pharmaceutical industries. However, due to its polysaccharide nature it lacks antimicrobial activity. In the current work, new pectin derivatives with interesting optical and antimicrobial properties were prepared via supramolecular chemistry utilizing Fe- or Cu-terpyridine (Tpy-Fe and Tpy-Cu) motifs. To proof derivatization of pectin, ultraviolet-visible spectroscopy (UV-Vis) and Fourier Transform infrared (FTIR) were used. In addition, the prepared pectin derivatives retained the known emulsification activity of the non-modified sugar beet pectin as seen from the particle size analysis of oil-in-water emulsions. The prepared derivatives showed antibacterial activity toward selected Gram-positive and Gram-negative bacteria. In addition, cytotoxicity test showed that the Tpy-Fe-pectin derivative was non-toxic to cells of human hepatocarcinoma, breast adenocarcinoma MCF7, and colorectal carcinoma cells at concentrations up to 100 μg/ml, while Tpy-Cu-pectin had moderate toxicity toward the aforementioned cells at the same concentration levels. The prepared derivatives could have potential applications in emulsions with antibacterial activity.

Shape-Memory Metallopolymer Networks Based on a Triazole-Pyridine Ligand

Shape memory polymers represent an interesting class of stimuli-responsive polymers. With their ability to memorize and recover their original shape, they could be useful in almost every area of our daily life. We herein present the synthesis of shape-memory metallopolymers in which the switching unit is designed by using bis(pyridine-triazole) metal complexes. The polymer networks were synthesized via free radical polymerization of methyl-, ethyl- or butyl-methacrylate, tri(ethylene glycol) dimethacrylate and a methacrylate moiety of the triazole-pyridine ligand. By the addition of zinc(II) or cobalt(II) acetate it was possible to achieve metallopolymer networks featuring shape-memory abilities. The successful formation of the metal-ligand complex was proven by Fourier transform infrared (FT-IR) spectroscopy and by 1H NMR spectroscopy. Furthermore, the shape-recovery behavior was studied in detailed fashion and even triple-shape memory behavior could be revealed.