In this work, two iron(II) coordination compounds with a N 2 O 2 coordinating Schiff base-like ligand bearing a redox active tetrathiafulvalene (TTF) unit and pyridine or trans-1,2-bis(4-pyridylethylene) as an axial ligand are synthesized. Crystals suitable for single X-ray structure analysis were obtained for the new ligand. The complexes were characterized by magnetic susceptibility measurements, T-dependent UV−vis spectroscopy, and cyclic voltammetry. Both complexes display spin transition behavior below room temperature with T 1/2 values of 146 and 156 K. The mononuclear iron(II) complex [Fe TTF L(py) 2 ] is relatively stable up to 400 K compared to similar complexes, showing no loss of axial ligands upon heating. Temperature dependent Mossbauer spectroscopy was conducted for the coordination polymer {[Fe TTF L(bpee)]} n to get more information regarding the origin of the stepwise spin crossover (SCO) behavior observed in the magnetic measurements. The change of the spin state is accompanied by a change of the optical properties, which can be monitored by VT−UV−vis spectroscopy for the mononuclear complex and has been analyzed in theoretical studies. The redox behavior of the iron(II) complexes reveals three reversible redox steps which are located at the iron center and at the TTF unit of the ligand. Oxidation of the TTF unit induces characteristic changes in the UV−vis spectrum that can be followed by spectroelectrochemical UV−vis spectroscopy. Addressing the potential of the ironcentered redox process results in similar changes in the UV−vis spectrum, which indicates an electronic coupling of the redox active unit with the metal center under certain circumstances.

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An amphiphilic iron(II) spin crossover complex with relatively short octyl chains was synthesised and the crystal structures of the high spin and the low spin state could be determined. In further reactions, a second modification of the hexa-coordinated complex and two different penta-coordinated complexes could be obtained and characterised by X-ray structure analysis. The examples demonstrate an influence of the alkyl chains on the stoichiometry of the final product. Different arrangements of the alkyl chains were observed in the crystal packing. Despite those differences, the spin transition of the hexacoordinated complexes is always gradual and comparable to that observed in solution.

New iron(II) coordination polymers with solvent-dependent spin-crossover behaviour have been synthesised by using an N 2 O 2 Schiff base like ligand and 4,4′-dipyridylethyne as the bridging axial ligand in different solvents. The effects of different solvents and preparation methods (temperature, concentration) on the magnetic properties have been investigated.

The synthesis of bio‐based and biodegradable plastics is a hot topic in research due to growing environmental problems caused by omnipresent plastics. As a result, polylactide, which has been known for years, has seen a tremendous increase in industrial production. Nevertheless, the manufacturing process using the toxic catalyst Sn(Oct) 2 is very critical. As an alternative, five zinc acetate complexes have been synthesized with Schiff base‐like ligands that exhibit high activity in the ring‐opening polymerization of non‐purified lactide. The systems bear different side arms in the ligand scaffold. The influence of these substituents has been analyzed. For a detailed description of the catalytic activities, the rate constants k app and k p were determined using in‐situ Raman spectroscopy at a temperature of 150 °C. The polymers produced have molar masses of up to 71 000 g mol −1 and are therefore suitable for a variety of applications. Toxicity measurements carried out for these complexes proved the nontoxicity of the systems.