Arnedo-Sánchez Leticia, Bhowmik Sandip, Hietala Sami, Puttreddy Rakesh, Lahtinen Manu, De Cola Luisa, Rissanen Kari
University of Jyvaskyla, Department of Chemistry, Nanoscience Center, Survontie 9 B, Jyväskylä, FI-40014, Finland.
Dalton Trans. 2017 Jun 6;46(22):7309-7316. doi: 10.1039/c7dt00983f.
Simple ML [M = Fe(ii), Co(ii), Ni(ii)] complexes obtained from a perfluoroalkylamide derivative of 4-aminophenyl-2,2',6,2'-terpyridine spontaneously, yet anion selectively, self-assemble into gels, which manifest an unprecedented rapid gel strength recovery, viz. self-healing, and thermal rearrangement in aqueous dimethyl sulfoxide. The key factor for gelation and rheological properties emerges from the fluorine-fluorine interactions between the perfluorinated chains, as the corresponding hydrocarbon derivative did not form metallogels. The perfluoro-terpyridine ligand alone formed single crystals, while its Fe(ii), Co(ii) or Ni(ii) complexes underwent rapid gelation leading to highly entangled fibrillar networks visualized by electron microscopy. The thermodynamic parameters of gelation based on variable temperature NMR H and F resonances showed that gelation was enthalpically favourable and entropically disfavourable. The step strain rheological experiments revealed that the gels undergo rapid self-healing and the morphological features, thermal stability and mechanical properties were found to depend on the nature of the metal ion.
由4-氨基苯基-2,2',6,2'-三联吡啶的全氟烷基酰胺衍生物制得的简单ML（M = Fe(ii)、Co(ii)、Ni(ii)）配合物能自发但阴离子选择性地自组装成凝胶，该凝胶表现出前所未有的快速凝胶强度恢复，即自修复能力，以及在二甲基亚砜水溶液中的热重排现象。凝胶化和流变性质的关键因素源自全氟链之间的氟-氟相互作用，因为相应的烃类衍生物并未形成金属凝胶。仅全氟三联吡啶配体形成了单晶，而其Fe(ii)、Co(ii)或Ni(ii)配合物则迅速凝胶化，形成了通过电子显微镜观察到的高度缠结的纤维状网络。基于变温核磁共振氢谱和氟谱共振的凝胶化热力学参数表明，凝胶化在焓上是有利的，而在熵上是不利的。阶跃应变流变实验表明，这些凝胶具有快速自修复能力，并且发现其形态特征、热稳定性和机械性能取决于金属离子的性质。
