We developed a family of spin-crossover complexes based on the classic bis(trispyrazolylborato)iron(II) ([Tp2Fe]) framework and bearing nitro groups on the pyrazole backbone. Reduction of the nitro function yields the corresponding amine derivatives such as [Fe(3-NH2Tp)2] (figure 1). Further reaction at the amine site was demonstrated. All complexes maintained spin-crossover properties, while variation of the nature, position and number of the functionalities allowed the investigation of the electronic and steric effects of the ligand modification on the spin-crossover in the solid and in solution. Amide bond formation between the amine-functionalized complexes and an oxidized carbon nanotube opens the possibility of spin state detection by low temperature transport measurements. We demonstrated this possibility on a system incorporating a different, tetranuclear, complex bound to a carbon nanotube by direct coordination of a carboxylate from the tube's wall to one of the metal centers. Low temperature conductivity measurements on a single nanotube functionalized with a few molecules demonstrated ballistic transport in the three terminal device (figure 2) and the possibility to use current intensity as a readout of the spin state.

Functionalized trispyrazolylborate spin crossover complexes: towards single molecule spin state detection

2019 Spring National Meeting

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