Göbel Christoph, Klimm Ottokar, Puchtler Florian, Rosenfeldt Sabine, Förster Stephan, Weber Birgit
Inorganic Chemistry II, University of Bayreuth, Universitätsstr. 30, 95440 Bayreuth, Germany.
Inorganic Chemistry I, University of Bayreuth, Universitätsstr. 30, 95440 Bayreuth, Germany.
Beilstein J Nanotechnol. 2017 Jun 26;8:1318-1327. doi: 10.3762/bjnano.8.133. eCollection 2017.
Spin-crossover compounds are a class of materials that can change their spin state from high spin (HS) to low spin (LS) by external stimuli such as light, pressure or temperature. Applications demand compounds with defined properties concerning the size and switchability that are maintained when the compound is integrated into composite materials. Here, we report the synthesis of [Fe(L)(L)] coordination polymer (CP) nanoparticles using self-assembled polystyrene--poly(4-vinylpyridine) (PS--P4VP) block copolymer (BCP) micelles as template. Variation of the solvent (THF and toluene) and the rigidity of the axial ligand L (L = 1,2-di(pyridin-4-yl)ethane) (bpea), -1,2-di(pyridin-4-yl)ethene (bpee), and 1,2-di(pyridin-4-yl)ethyne) (bpey); L = 1,2-phenylenebis(iminomethylidyne)-bis(2,4-pentanedionato)(2-)) allowed the determination of the preconditions for the selective formation of nanoparticles. A low solubility of the CP in the used solvent and a high stability of the Fe-L bond with regard to ligand exchange are necessary for the formation of composite nanoparticles where the BCP micelle is filled with the CP, as in the case of the [FeL(bpey)] @BCP. Otherwise, in the case of more flexible ligands or ligands that lead to high spin complexes, the formation of microcrystals next to the CP-BCP nanoparticles is observed above a certain concentration of [Fe(L)(L)] . The core of the nanoparticles is about 45 nm in diameter due to the templating effect of the BCP micelle, independent of the used iron complex and [Fe(L)(L)] concentration. The spin-crossover properties of the composite material are similar to those of the bulk for FeL(bpea)] @BCP while pronounced differences are observed in the case of [FeL(bpey)] @BCP nanoparticles.
自旋交叉化合物是一类材料，它们可以通过光、压力或温度等外部刺激将其自旋状态从高自旋（HS）转变为低自旋（LS）。应用需要具有明确尺寸和可切换性的化合物，这些特性在化合物集成到复合材料中时仍能保持。在此，我们报告了使用自组装的聚苯乙烯-聚（4-乙烯基吡啶）（PS-P4VP）嵌段共聚物（BCP）胶束作为模板合成[Fe(L)(L)]配位聚合物（CP）纳米颗粒。通过改变溶剂（四氢呋喃和甲苯）以及轴向配体L（L = 1,2-二（吡啶-4-基）乙烷）（bpea）、-1,2-二（吡啶-4-基）乙烯（bpee）和1,2-二（吡啶-4-基）乙炔）（bpey）的刚性；L = 1,2-亚苯基双（亚氨基次甲基）-双（2,4-戊二酮酸根）（2-），可以确定选择性形成纳米颗粒的前提条件。对于形成BCP胶束填充有CP的复合纳米颗粒，如[FeL(bpey)]@BCP的情况，CP在所用溶剂中的低溶解度以及Fe-L键相对于配体交换的高稳定性是必要的。否则，在配体更灵活或导致高自旋配合物的配体的情况下，在[Fe(L)(L)]的一定浓度以上会观察到CP-BCP纳米颗粒旁边形成微晶。由于BCP胶束的模板效应，纳米颗粒的核心直径约为45nm，与所用的铁配合物和[Fe(L)(L)]浓度无关。对于FeL(bpea)]@BCP，复合材料的自旋交叉特性与本体材料相似，而在[FeL(bpey)]@BCP纳米颗粒的情况下观察到明显差异。
