Spincrossover complexes with long-lived excited high spin states stabilized by changing coordination number

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In line with the ongoing miniaturization in the electronic industry, the design of molecular switches and data storage devices is going to become a key technology. Spincrossover complexes are able to serve as such devices. Spincrossover complexes can have two distinct spin states (high spin state and low spin state) which are addressable with light with exceptional high quantum yields. Unfortunately, for many possible applications the activation energy for the thermally activated conversion between the two states is far too low. In this project, this problem is going to be attacked by a change in the coordination number from six (low spin state) to seven (high spin state). The design starts with Fe2+ complexes employing strong NHC and polypyridyl ligands that are found in a very stable low spin state. The low spin complexes are tuned to spincrossover complexes by introduction of a sterically active substituent that at the same time includes a seventh donor. The magnetic properties are going to be investigated by variable temperature UV/Vis spectroscopy, proton NMR spectroscopy, as well as laser flash photolysis and measurement of the magnetic properties on a SQUID. This to date only rarely used principle of N6/N7 coordination change should allow the observation of long lived excited spin states.