Richard Sarah, Le Duc Gaëtan, Le Poul Nicolas, Le Mest Yves, Reinaud Olivia, Rebilly Jean-Noël
CNRS UMR 8601, Laboratoire de Chimie et de Biochimie pharmacologiques et toxicologiques, Université Paris Descartes, Sorbonne Paris Cité, 75006 Paris, France.
Dalton Trans. 2017 Nov 14;46(44):15249-15256. doi: 10.1039/c7dt03375c.
A new calix[6]arene scaffold bearing a tris-imidazole binding site at the small rim and three tetradentate aza ligands at the large rim was synthesized. The system binds three Cu ions at the large rim sites and is unable to bind a fourth one, which remains in solution. The charge repulsion between the complexes, together with the flexibility of the scaffold, disorganizes the small rim site for binding and prevents its use for host-guest studies. Although the presence of MeCN or DMF guests does not alter this state, the addition of a heptylamine guest, which further displays Brønsted basicity, restores its receptor ability by stabilizing the extra Cu ion at the tris-imidazole site with concomitant guest encapsulation and binding of an exo hydroxo ligand. This chemoselective nuclearity switch yields a tetranuclear complex in which the guest backbone is preorganized in front of three potentially reactive Cu(ii) complexes, reminiscent of polynuclear Cu enzyme active sites.
合成了一种新型杯[6]芳烃支架，其小环带有三咪唑结合位点，大环带有三个四齿氮杂配体。该体系在大环位点结合三个铜离子，无法再结合第四个铜离子，第四个铜离子留在溶液中。配合物之间的电荷排斥以及支架的柔韧性，使小环结合位点无序化，无法用于主客体研究。尽管乙腈或二甲基甲酰胺客体的存在不会改变这种状态，但加入具有布朗斯台德碱性的庚胺客体，通过将额外的铜离子稳定在三咪唑位点，同时包封客体并结合一个外羟基配体，恢复了其受体能力。这种化学选择性核开关产生了一种四核配合物，其中客体主链在三个潜在的活性铜（II）配合物前预先排列，让人联想到多核铜酶活性位点。
