Inthasot Alex, Brunetti Emilio, Lejeune Manuel, Menard Nicolas, Prangé Thierry, Fusaro Luca, Bruylants Gilles, Reinaud Olivia, Luhmer Michel, Jabin Ivan, Colasson Benoit
Laboratoire de Chimie Organique, Université Libre de Bruxelles (U.L.B.), Avenue F.D. Roosevelt 50, CP160/06, 1050, Brussels, Belgium.
Laboratoire de Résonance Magnétique Nucléaire Haute Résolution, Université Libre de Bruxelles (U.L.B.), Avenue F.D. Roosevelt 50, CP160/08, 1050, Brussels, Belgium.
Chemistry. 2016 Mar 24;22(14):4855-62. doi: 10.1002/chem.201505057. Epub 2016 Feb 24.
The Huisgen thermal reaction between an organic azide and an acetylene was employed for the selective monofunctionalization of a X6 -azacryptand ligand bearing a tren coordinating unit [X6 stands for calix[6]arene and tren for tris(2-aminoethyl)amine]. Supramolecular assistance, originating from the formation of a host-guest inclusion complex between the reactants, greatly accelerates the reaction while self-inhibition affords a remarkable selectivity. The new ligand possesses a single amino-leg appended at the large rim of the calixarene core and the corresponding Zn(2+) complex was characterized both in solution and in the solid state. The coordination of Zn(2+) not only involves the tren cap but also the introverted amino-leg, which locks the metal ion in the cavity. Compared with the parent ligand deprived of the amino-leg, the affinity of the new monofunctionalized X6 tren ligand 6 for Zn(2+) is found to have a 10-fold increase in DMSO, which is a very competitive solvent, and with an enhancement of at least three orders of magnitude in CDCl3 /CD3 OD (1:1, v/v). In strong contrast with the fast binding kinetics, decoordination of Zn(2+) as well as transmetallation appeared to be very slow processes. The monofunctionalized X6 tren ligand 6 fully protects the metal ion from the external medium thanks to the combination of a cavity and a closed coordination sphere, leading to greater thermodynamic and kinetic stabilities.
有机叠氮化物与乙炔之间的惠斯根热反应被用于对带有三（2 - 氨乙基）胺配位单元（tren）的X6 -氮杂穴醚配体进行选择性单官能化（X6代表杯[6]芳烃）。源自反应物之间形成主客体包合物的超分子辅助极大地加速了反应，而自抑制作用则提供了显著的选择性。新配体在杯芳烃核的大边缘处连接有单个氨基臂，并且相应的Zn(2+)配合物在溶液和固态下均得到了表征。Zn(2+)的配位不仅涉及tren帽，还涉及内向的氨基臂，这将金属离子锁定在腔内。与不含氨基臂的母体配体相比，发现新的单官能化X6 tren配体6对Zn(2+)的亲和力在二甲基亚砜（一种竞争非常激烈的溶剂）中增加了10倍，在CDCl3 /CD3 OD（1:1，v/v）中至少增强了三个数量级。与快速的结合动力学形成强烈对比的是，Zn(2+)的解配位以及金属转移似乎是非常缓慢的过程。由于腔和封闭配位球的结合，单官能化的X6 tren配体6使金属离子完全免受外部介质的影响，从而导致更大的热力学和动力学稳定性。
