Spin-crossover complexes have potential applicability in information storage devices, sensors, and processing units. One of the biggest challenges is to integrate these molecules into devices while retaining their spin-crossover characteristics. To address this problem, modifications of the ligand backbone can be used to tune the molecular properties and adapt the complexes to the desired working environment. We report on a family of nitro & amino-derivative spin-crossover complexes based on the classic rigid air-stable bis(trispyrazolylborate)iron (II) framework. Direct exchange reactions between nitro-pyrazole and tetrabutylammonium trispyrazolylborate (Tp-) ligand or unfunctionalized [Tp2Fe] complexes were developed to synthesize a variety of nitro-Tp ligands and nitro-complexes. The amino-functionalized derivatives were obtained through reduction the nitro groups. All synthesized complexes maintain spin-crossover properties. We investigated the impact of the variation of the nature, position, and number of the functionalities on the electronic and steric effects properties of the ligands and their consequences on the spin-crossover properties of the complexes in the solid-state and in solution. Our systematic investigation including XRD, electrochemistry, IR, UV-vis spectrometry, SQUID and paramagnetic NMR of cobalt analogs helps disentangle the electronic and steric effects. Finally, amine derivatives further provide a point of entry for a variety of functionalizations, while the easy sublimation of all complexes is an advantage in their integration into thin-film devices.

Synthesis and characterization of functionalized trispyrazolylborate spin crossover complexes

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.