Search results for "macrocycles"

Chiral hemicucurbit[8]uril as an anion receptor: selectivity to size, shape and charge distribution

2017

A novel eight-membered macrocycle of the hemicucurbit[n]uril family, chiral (all-R)-cyclohexanohemicucurbit[8]uril (cycHC[8]) binds anions in a purely protic solvent with remarkable selectivity. The cycHC[8] portals open and close to fully encapsulate anions in a 1 : 1 ratio, resembling a molecular Pac-Man™. Comprehensive gas, solution and solid phase studies prove that the binding is governed by the size, shape and charge distribution of the bound anion. Gas phase studies show an order of SbF6− ≈ PF6− > ReO4− > ClO4− > SCN− > BF4− > HSO4− > CF3SO3− for anion complexation strength. An extensive crystallographic study reveals the preferred orientations of the anions within the octahedral cav…

Bis-urea macrocycles with a deep cavity.

2015

Two configurational isomers of bis-urea macrocycles have been synthesized, and their neutral molecule recognition was studied by X-ray crystallography and (1)H NMR experiments. Cooperative action between the deep cavity and the urea groups and the influence of dipole alignments on molecular recognition are discussed.

Bis-urea macrocycles with a deep cavity

2015

Solid state halogen bonded networks vs. dynamic assemblies in solution: explaining N⋯X interactions of multivalent building blocks

2015

Tetrapyridine functionalized resorcinarene macrocycles were used as multivalent building blocks for the construction of halogen bonded networks with aryl halide linkers. In the solid state, resorcinarene macrocycles and aryl halide linker molecules assembled into interpenetrated, multidimensional halogen bonded networks with porous structure caused by the 3D block scaffold of the resorcinarenes. 19F NMR spectroscopy proved halogen bond formation also in solution, as either upfield or downfield shifts were observed depending on the bivalent or monovalent halogen bond binding mode. The binding mode in solution was explained by density functional theory computations. peerReviewed

Guest-Induced Folding and Self-Assembly of Conformationally Adaptive Macrocycles into Nanosheets and Nanotubes

2017

A conformationally adaptive macrocycle is presented, namely zorb[4]arene, which exists in multiple conformations in the uncomplexed state. The binding cavity of zorb[4]arene is concealed, either due to a collapsed conformation or by self-inclusion. The zorb[4]arene with long alkyl chains manifests itself with surprisingly low melting point and thus exist as an oil at room temperature. Binding of a guest molecule induces the folding and conformational rigidity of zorb[4]arene and leads to well-defined three-dimensional structures, which can further self-assemble into nanosheets or nanotubes upon solvent evaporation, depending on guest molecules and the conformations they can induce.

Selective recognition of aromatic hydrocarbons by endo-functionalized molecular tubes via C/N-H⋅⋅⋅π interactions

2018

Abstract Molecular recognition of aromatic hydrocarbons by four endo -functionalized molecular tubes has been studied by 1 H NMR spectroscopy, computational methods, and single crystal X-ray crystallography. The binding selectivity is rationalized by invoking shape complementarity and dipole alignment. The non-covalent interactions are proved to predominantly be C/N-H⋅⋅⋅ π interactions.

Synthèse et étude physico-chimique de ligands macrocycliques, macrobicycliques et macrotricycliques dérivés du 5,12-dioxocyclame

2002

The synthesis and the physico-chemical studies of macropolycyclic ligands based on 5,12-dioxocyclam L1 are presented. The first part of this dissertation presents the structural and physico-chemical properties of L1 and its N-substituted derivatives L2 and L3. A potentiometric study reveald a cooperative protonation of the two macrocyclic ligands L1 and L2 whereas the study of the macrotricycle L3 in a methanol-water mixture revealed a sequential cooperative diprotonation of the four tertiary amines. The square planar nickel and copper complexes were synthesized and characterized using infrared, UV-vis and ESR spectgroscopy. The spectroscopic studies showed the presence of intermolecular hy…

Selective recognition of aromatic hydrocarbons by endo-functionalized molecular tubes via C/N-H⋅⋅⋅π interactions

2018

Molecular recognition of aromatic hydrocarbons by four endo-functionalized molecular tubes has been studied by 1H NMR spectroscopy, computational methods, and single crystal X-ray crystallography. The binding selectivity is rationalized by invoking shape complementarity and dipole alignment. The non-covalent interactions are proved to predominantly be C/N-H⋅⋅⋅π interactions. peerReviewed

Azonia spiro polyaza macrocycles containing biphenyl subunits as anion and cation receptors

2011

Abstract The reaction of N-Boc triprotected cyclam with bis(chloromethyl)biphenyl followed by the corresponding deprotection of the nitrogen atoms allows the preparation of receptor 3 containing an azonia spiro subunit. This receptor shows slightly increased basicity than cyclam, in particular for the formation of the appropriate triply charged species as a consequence of the reduced capacity of the structure present in 3 to stabilize the species with lower protonation degrees through the formation of intramolecular hydrogen bonds. The properties of 3 as a receptor for Cu2+ and Zn2+ and the anions derived from PO 4 3 − ( Pi ) , P 2 O 7 4 − ( PPi ) , P 3 O 10 5 − ( TPP ) and ATP have been st…

An Off-On-Off Fluorescent Sensor for pH Windows Based on the 13aneN4-Zn 2+ System

2016

International audience; The new ligand L was prepared and features a 13-membered tetraaza macrocyclic ring with a 1,8-naphthalimide fluorophore appended to a C atom of its backbone. The protonation constants of L as well as its complexation constants with Zn2+ ions were determined in 1:1 water/methanol solutions by potentiometric titrations. Fluorimetric pH titrations were performed with L alone and L in the presence of Zn2+ ions (1:1), and the species distributions (%) versus pH were compared. A window-shaped fluorescence trend was observed with pH for the L/Zn2+ system, which behaves as an off-on-off pH sensor. The on window is centred in the 6.5-7.5 pH range, in correspondence with the f…