Cation binding and conformation of octafunctionalized calix[4]resorcinarenes

Abstract

Abstract:The preparations of four calix [4]resorcinarene esters and two calix [4]resorcinarene amides are reported. The logarithms of association constants have been determined by the picrate extraction method for a variety of metal cations, including alkali metal, alkaline earth, lanthanum, and silver cations. Strong binding toward silver ion, and selectivity amongst the alkaline earth cations, was observed for the octa-a-(diethyl acetamide) 3c. Flattened cone conformations have been established for both C-undecylcalix[4]resorcinarene octa-a-(methyl acetate), 3a, and octa-a-(diethyl acetamide), 3c, in chloroform solutions at 200 K. Dynamic nuclear magnetic resonance was used to identify rapid conformational interconversions of both 3a and 3c corresponding to pseudorotation between flattened cone conformations. The silver complex of 3c also exhibits pseudorotation; however, the activation barrier was observed to increase from 42 W mol-I in the free ligand to 49 kJ mol-' in the complex. The NMR data indicate that the metal cation binding occurs in a symmetrical fashion using two pairs of binding sites that are disposed across the macrocyclic ring from one another. Considering these data it is concluded that four carbonyl functions are involved in the binding of a metal cation in a 1: 1 complex with the ligand. variCtC de cations metalliques, y compris ceux de l'argent, des mCtaux alcalins et alcalino-terreux et de la sene des lanthanides. Avec I'octa-a-(diethyl acCtamide), 3c, on aobservk que lesions de l'argent sont fortement fixes et qu'il existe une grande sClectivitC parmi les cations des alcalino-terreux. On a Ctabli que, en solutions dans le chloroforme a 200 K, le C-und6cylcalix[4]r6sorcinarbne octa-a-(acetate de mCthyle), 3a, ainsi que I'octa-a-(dikthyl acCtamide), 3c, ont tous les deux des conformations coniques aplaties. On a utilisC la resonance magnetique nuclCaire dynamique pour identifier les interconversions conformationnelles rapides des deux composCs 3a et 3c qui correspondent 2 la pseudorotation entre des conformations coniques aplaties. Le complexe de l'argent avec le compose 3c prksente aussi de la pseudorotation; toutefois, on a observe que la barribre d'activation augmente de 42 W mol-I dans le coordinat libre i 49 W mol-' dans le complexe. Le donnCes de la RMN indiquent que le cation mCtallique se fixe d'une f a~o n symCtrique en utilisant deux paires de sites de fixation disposes l'un en face de l'autre de chaque cGtC du macrocycle. Sur la base de ces donnCes, on en conclut que les quatre fonctions carbonyles sont impliquees dans la fixation d'un cation mttallique dans un complexe 1 : 1 avec le coordinat.

Evaluation of the Radical Scavenging Activity of Resorcinarenes by DPPH• Free Radical Assay

“…Compound 1 was obtained by the acid-catalysed condensation of resorcinol and acetaldehyde. 20 It was then reacted to yield its aminomethylated, 21 dansylated 22 and ester 23 derivatives (see Scheme 1) whose chemical and physical characteristics tallied well with those reported in the cited literature. Compound 3 has been prepared for the first time as a yellow solid in 50% yield and has been characterized by recording its Scheme 1 Structures of resorcinarene derivatives and the reference compounds investigated in the present study.…”

Effect of ligand on the synthesis of star polymers by resorcinarene‐based ATRP initiators

“…Resorcinarenes, like calixarenes, tend to adopt a crown‐shaped conformation in their unsubstituted form owing to the circular array of hydrogen bonds between the hydroxylic groups 29. Derivatization of these macrocycles, and particularly their upper rim holding the phenolic hydroxyl groups, alters their conformational and complexing properties,30, 31 which was also observed for our multifunctional initiators by different NMR techniques and molecular modeling 28…”

Phosphorylated Aminoacetal in the Synthesis of New Acyclic, Cyclic, and Heterocyclic Polyphenol Structures

“…Compound 5 was synthesized from the rccc ‐isomer of calix[4]resorcinol 4 , which, according to the literature data, does not transform into another isomer even at high temperature . In our case, the reaction proceeds at room temperature and this transformation is even less possible.…”