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Nowadays there is a high demand for specialized functional materials for specific applications in sensors or biomedicine (e.g. fMRI). For their implementation in devices, nanostructuring and integration in a composite matrix are indispensable. Spin crossover complexes are a highly promising family of switchable materials where the switching process can be triggered by various external stimuli. In this work, the synthesis of nanoparticles of the spin crossover iron(ii) coordination polymer [Fe(L)(bipy)] (with L = 1,2-phenylenebis(iminomethylidyne)bis(2,4-pentanedionato)(2-) and bipy = 4,4'-bipyridine) is described using polystyrene-poly-4-vinylprididine blockcopolymer micelles as the template defining the final size of the nanoparticle core. A control of the spin crossover properties can be achieved by precise tuning of the crystallinity of the coordination polymer via successive addition of the starting material Fe(L) and bipy. By this we were able to synthesize nanoparticles with a core size of 49 nm and a thermal hysteresis loop width of 8 K. This is, to the best of our knowledge, a completely new approach for the synthesis of nanoparticles of coordination polymers and should be easily transferable to other coordination polymers and networks. Furthermore, the use of blockcopolymers allows a further functionalization of the obtained nanoparticles by variation of the polymer blocks and an easy deposition of the composite material on surfaces via spin coating.

The reactivity of the carbenoid group 13 metal ligands ECp* (E = Al, Ga) toward low valent transition metal complexes [TM(btsa)] (TM = Fe, Co, Zn; btsa = bis(trimethylsilyl)amide) was investigated, revealing entirely different reaction patterns for E = Al and Ga. Treatment of [Co(btsa)] with AlCp* yields [Cp*Co(μ-H)(Al(κ-(CHSiMe)NSiMe)(btsa))] (1) featuring an unusual heterometallic bicyclic structure that results from the insertion of AlCp* into the TM-N bond with concomitant ligand rearrangement including C-H activation at one amide ligand. For [Fe(btsa)], complete ligand exchange gives FeCp*, irrespective of the employed stoichiometric ratio of the reactants. In contrast, treatment of [TM(btsa)] (TM = Fe, Co) with GaCp* forms the 1:1 and 1:2 adducts [(GaCp*)Co(btsa)] (2) and [(GaCp*)Fe(btsa)] (3), respectively. The tendency of AlCp* to undergo Cp* transfer to the TM center appears to be dependent on the nature of the TM center: For [Zn(btsa)], no Cp* transfer is observed on reaction with AlCp*; instead, the insertion product [Zn(Al(η-Cp*)(btsa))] (4) is formed. In the reaction of [Co(btsa)] with the trivalent [Cp*AlH], transfer of the amide ligands without further ligand rearrangement is observed, leading to [Co(μ-H)(Al(η-Cp*)(btsa))] (5).

Nanoparticles of the spin‐crossover coordination polymer [FeL(bipy)]n were synthesized by confined crystallization within the core of polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) diblock copolymer micelles. The 4VP units in the micellar core act as coordination sites for the Fe complex. In the bulk material, the spin‐crossover nanoparticles in the core are well isolated from each other allowing thermal treatment without disintegration of their structure. During annealing above the glass transition temperature of the PS block, the transition temperature is shifted gradually to higher temperatures from the as‐synthesized product (T1/2↓=163 K and T1/2↑=170 K) to the annealed product (T1/2↓=203 K and T1/2↑=217 K) along with an increase in hysteresis width from 6 K to 14 K. Thus, the spin‐crossover properties can be shifted towards the properties of the related bulk material. The stability of the nanocomposite allows further processing, such as electrospinning from solution.