Sulfonatocalixarene Counterion Exchange Binding Model in Action: Metal‐Ion Catalysis Through Host‐Guest Complexation

Abstract

p-Sulfonatocalixarene water soluble macrocyclic host receptors are known to form cooperative ternary complexes with complementary organic guest and metal cations. This property may be explored to enhance the interaction of weak nitrogen ligands with metal cations in a confined space showing some resemblance to metal-containing enzymes. However, the best of our knowledge, catalytic potential of this property remains unexplored. In this work the Ni 2 + catalyzed hydrolysis of a picolinate ester (2,4-dinitrophenyl picolinate, 1) was used as a model reaction to evaluate the effect of sulfonatocalixarene macrocycles in the kinetics of this reaction. The results show that the host molecules promote the reaction through simultaneous complexation of the metal cation and the substrate and, in the case of the larger calixarenes containing more basic phenol groups, substantially higher rate enhancements are observed owing to additional assistance provided by base/ nucleophilic catalysis. However, due the ionic nature of these receptors auto-inhibition of the reaction is observed at higher concentrations due counterion (Na +) binding that competes with the catalytically active Ni 2 +-complexes.

Supramolecular Handshakes: Characterization of Urea‐Carboxylate Interactions Within Calixarene Frameworks

“…The ability of molecular capsule to host one or more guests opens the path towards many applications, justifying the subsequent research growth in this field. Namely, the role of molecular capsule as a nanoreactor or a drug delivery device implies two basic criteria with respect to the design of a capsular host: a larger cavity and the possibility of reversible opening and closing, followed by the release or capture of a desired cargo [2–6] . A tool that enables these prerequisites is provided by non‐covalent synthesis, where self‐assembly or hetero‐assembly of molecular monomers into a capsule is realized via intermolecular interactions such as metal‐ligand coordination bonds, [7–11] hydrogen bonds, [12–14] ionic interactions, [15] halogen [16] or chalcogen [17] bonds.…”

“…Namely, the role of molecular capsule as a nanoreactor or a drug delivery device implies two basic criteria with respect to the design of a capsular host: a larger cavity and the possibility of reversible opening and closing, followed by the release or capture of a desired cargo. [2][3][4][5][6] A tool that enables these prerequisites is provided by non-covalent synthesis, where self-assembly or hetero-assembly of molecular monomers into a capsule is realized via intermolecular interactions such as metal-ligand coordination bonds, [7][8][9][10][11] hydrogen bonds, [12][13][14] ionic interactions, [15] halogen [16] or chalcogen [17] bonds. The control over the association can be imposed by adjusting the physico-chemical properties of the solution (e. g. pH, [18,19] temperature, ionic strength).…”

Design and synthesis of piezochromic materials exploring intermolecular charge transfer: chalconoids bound to thep-sulfonatocalix[6]arene macrocycle

“…Recently, a p -sulfonatocalix[6]arene (SCX6) molecular container was studied by our group. 25–28 SCX6 finds diverse applications in optical sensors, 29 switches and drug delivery carriers. 30 In the present endeavour, we demonstrate that the SCX6 macrocycle can be explored for designing materials exhibiting mechanochromism.…”

Supraamphiphilic Systems Based on Metallosurfactant and Calix[4]resorcinol: Self-Assembly and Drug Delivery Potential

“…The use of calixarenes as a macrocyclic component is particularly attractive due to the possibility of modification by various functional groups on both sides of the macrocyclic platform. Moreover, calixarenes are capable of forming complexes with various ions and small organic molecules, which can enter the aromatic cavity of the calixarene framework. − The guest molecules can also be bonded by calixarene substituents located outside the macrocyclic cavity. Sulfonated calix[4]­arenes typically form supraamphiphiles with cationic surfactant molecules due to electrostatic interactions. ,,,− The complexation between the surfactant and the macrocycle in this case leads to a decrease in the critical aggregation concentration compared of the individual components.…”