title: Entasis through hook-and-loop fastening in a glycoligand with cumulative weak forces stabilizing Cu(I).
abstract: The idea of a possible control of metal ion properties by constraining the coordination sphere geometry was introduced by Vallee and Williams with the concept of entasis, which is frequently postulated to be at stake in metallobiomolecules. However, the interactions controlling the geometry at metal centers remain often elusive. In this study, the coordination properties toward copper ions—Cu(II) or Cu(I)—of a geometrically constrained glycoligand centered on a sugar scaffold were compared with those of an analogous ligand built on an unconstrained alkyl chain. The sugar-centered ligand was shown to be more preorganized for Cu(II) coordination than its open-chain analogue, with an unusual additional stabilization of the Cu(I) redox state. This preference for Cu(I) was suggested to arise from geometric constraints favoring an optimized folding of the glycoligand minimizing steric repulsions. In other words, the Cu(I) d(10) species is stabilized by valence shell electron pair repulsion (VSEPR). This idea was rationalized by a theoretical noncovalent interactions (NCI) analysis. The cumulative effects of weak forces were shown to create an efficient buckle as in a hook-and-loop fastener, and fine structural features within the glycoligand reduce repulsive interactions for the Cu(I) state. This study emphasizes that monosaccharide platforms are appropriate ligand backbones for a delicate geometric control at the metal center, with a network of weak interactions within the ligand. This structuration availing in glycoligands makes them attractive for metallic entasis.
authors.affiliation: Ecole Normale Supérieure-PSL Research University , Département de Chimie, 24 rue Lhomond, F-75005 Paris, France.
authors.forename: Ludivine
authors.initials: L
authors.lastname: Garcia
authors.forename: Federico
authors.initials: F
authors.lastname: Cisnetti
authors.forename: Natacha
authors.initials: N
authors.lastname: Gillet
authors.forename: Régis
authors.initials: R
authors.lastname: Guillot
authors.forename: Magali
authors.initials: M
authors.lastname: Aumont-Nicaise
authors.forename: Jean-Philip
authors.initials: JP
authors.lastname: Piquemal
authors.forename: Michel
authors.initials: M
authors.lastname: Desmadril
authors.forename: François
authors.initials: F
authors.lastname: Lambert
authors.forename: Clotilde
authors.initials: C
authors.lastname: Policar
mesh_terms: D002241:Carbohydrates / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*
chemical_list: D002241:Carbohydrates; D008024:Ligands; D009942:Organometallic Compounds; D003300:Copper