A Calix(4)arene Pyridine Derivative and Its Monomeric Component:  Structural and Thermodynamic Aspects of Their Complexation with Metal Cations

Abstract

The interaction of a calix(4)arene derivative, namely 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra[2-(4-pyridyl)methoxy]calix(4)arene, 1a, and its monomeric component, p-tert-butylphenoxy-4-pyridine, 1b, with metal cations has been investigated in acetonitrile and methanol. (1)H NMR measurements carried out in CD(3)CN show the primary role played by the pyridyl nitrogens in their complexation with metal cations. Conductance measurements demonstrated that for all cations (except mercury) the composition of the metal ion complexes of 1a is 1:1 (ligand:metal cation). However, 1a hosts two mercury cations per unit of ligand. For the monomer 1b, complexes of 2:1 (ligand:metal cation) stoichiometries are formed with the exception of Pb(2+) (1:1 composition). The thermodynamics of complexation of these systems are reported in acetonitrile. Data in methanol are limited to stability constant values for mercury(II) and these ligands. This paper demonstrates for the first time that thermodynamic data for the complexation of the monomeric component of the ligand and metal cations contribute significantly to the interpretation of systems involving cation-calixarene interactions in solution.

Calixpyrrole chemistry: a study of a new ditopic receptor highlighting some fundamental concepts in assessing thermodynamic selectivity

“…No changes in the molar conductance are observed after the break at the 1 : 1 ([1]/[M n+ ]) stoichiometry, suggesting that one cation is hosted per unit of 1. The molar conductance value at infinite dilution for mercury perchlorate investigated in acetonitrile was found to be within the range expected, as compared with the L 0 m value reported in the literature, 8 which was 342.17 S cm 2 mol À1 .…”

“…Thus, the results obtained from this investigation are compared with those for calix [4]pyrrole, 2, 4 an analogous derivative, 3, 7 and a calix [4]arene ketone derivative, 4, previously reported by our group. 8…”

Coordination chemistry of calix[4]arene derivatives with lower rim functionalisation and their applications

“…Her work in this area, prior to 2000, has been extensively reviewed [57]. She has published a number of detailed studies, since 2000, on a range of calix [4]arene derivatives including complexation studies of calix [4]arene ketone derivatives with sodium ions [58,59], complexation of calix [4]arene ester, ketone and acetamide derivatives with lanthanides [60], complexation of calix [4]arene pyridine derivatives with lead and mercury cations [61], complexation of calix [4]arene amines and amides with lanthanides [62], complexation of a partially substituted calix [4]arene aminophosphate derivative with a range of cations [63], complexation of calix [4]arene ester and ketone derivatives with lead and cadmium ions [64], complexation of calix [4]arene with mixed pendant arms (di-functionalised with ethylethanoate and ethylthioethoxy groups) with a range of cations [65,66]. Many of these studies offered a comprehensive investigation into the role of solvation of host and guest species in a given medium, and indeed medium effects feature as one of the main areas of focus of investigation in all of these studies.…”

Three‐Dimensional Network Structures Based on Pyridyl‐Calix[4]Arene Metal Complexes

“…Pyridine units have been used widely to obtain multidentate systems; the covalent connection between the macrocyclic cavity and these monodentate ligands is a key factor for effective design . Pyridyl‐calix[4]arenes have often been synthesized as tetradentate ligands by introducing 2‐ or 4‐pyridylmethyl moieties at the lower rim of the tert ‐butyl‐calix[4]arenes; in all cases, the interaction between the ligand and the metal center does not involve the calixarene cavity, and no evidence of the formation of polymeric or 3 D network structures has ever been reported …”