Art and chemistry: the topochemical principle and Las Meninas of Vel��zquez

The present paper is intended to expose an example of similarity in chemistry and in painting not based on shape or common origin but rather on the concepts they involve. I partly wrote this text in the 1980s. I was then learning solid state chemistry at the Weizmann Institute in Israel. At that time, it became evident to me that there was a possible link between a reaction in the crystalline state and one of the many interpretations of Las Meninas of Velázquez. More precisely, I asked myself if a relation might be found between an organic reaction in a crystal governed by the topochemical principle and the interpretation given by the French philosopher, Michel Foucauld, in his book The Order of Things, of Las Meninas in terms of the topology the gazes of the depicted figures.     

Calix[4]azacrowns as novel molecular scaffolds for the generation of visible and near-infrared lanthanide luminescence

Two calix[4]azacrowns, capped with two aminopolyamide bridges, were used as ligands for the complexation of lanthanide ions [Eu(III), Tb(III), Nd(III), Er(III), La(III)]. The formation of 1:2 and 1:1 complexes was observed, and stability constants, determined by UV absorption and fluorescence spectroscopy, were found to be generally on the order of log beta(11) approximately 5-6 and log beta(12) approximately 10. The structural changes of the ligands upon La(III) complexation were probed by 1H NMR spectroscopy. The two ligands were observed to have opposite fluorescence behaviors, namely, fluorescence enhancement (via blocking of photoinduced electron transfer from amine groups) or quenching (via lanthanide-chromophore interactions) upon metal ion complexation. Long-lived lanthanide luminescence was sensitized by excitation in the pi,pi band of the aromatic moieties of the ligands. The direct involvement of the antenna triplet state was demonstrated via quenching of the ligand phosphorescence by Tb(III). Generally, Eu(III) luminescence was weak (Phi(lum) 相似文献   

Novel C3v-symmetrical N7-Hexahomotriazacalix[3]cryptand: a highly efficient receptor for halide anions

[structure: see text] We report the synthesis of a novel C(3)(v)()-symmetrical N(7)-hexahomotriazacalix[3]cryptand (1). Compound 1 was shown to be in a fixed cone conformation by (1)H NMR spectroscopy and X-ray single-crystal structure determination. Complexation studies showed that 1 is a selective receptor for halide ions. The effects of zinc metal cation on the receptor (1-Zn(2+)) upon anion recognition are also shown.     

Complexation chemistry. Double- and multi-1,3-alternate-calixcrowns

Metal ion complexation behavior in calix[4]crown multimers (mono, di, trimer) have been investigated through X-ray crystallography, two-phase extraction, and ¹H NMR measurement.     

Water-soluble para-Sulfonated 1,2;3,4-Calix[4]arene-biscrowns in the 1,2-Alternate Conformation

The preparation of a series of p-sulfonated 1,2;3,4-calix[4]arene-biscrowns in the 1,2-alternate conformation is reported. These compounds are of two types:symmetrical p-sulfonated 1,2;3,4-calix[4]arene-biscrowns in which the two crown loops are the same and unsymmetrical p-sulfonated1,2;3,4-calix[4]arene-biscrowns in which the two crown loops are different. The X-ray structures of two synthetic intermediates are given. Preliminary complexation studies showed the ligands to present pronounced Cs⁺/Na⁺ selectivities.     

Thiophilic reaction of t-butyllithium on cyclic thioethers

The attack of t-butyllithium on the S atom of cyclic thioethers as 2,2-diphenyl thiacyclohexane and bicyclic analogues is described. The structure of the products are proved by physical data and synthesis. The driving factor for this reaction seems to be the stability of the carbanion formed.     

Synthesis and binding properties of calix[4]arenes with [2 + 2'] mixed ligating functional groups

A series of mixed [2 + 2'] p-tert-butylcalix[4]arene have been synthesised by selective 1,3-dialkylation of phenolic groups using various alkylating agents such as benzyl bromide, methyl iodide, ethyl bromoacetate, and 2-methoxyethyl tosylate. The extraction and complexation properties of the synthesized calixarenes towards alkali and alkaline earth metal cations have been investigated in acetonitrile by means of UV spectrophotometry and 1H NMR spectroscopy. The results show the formation of ML and/or ML2 species depending on the ligand and the cation. The enthalpies and entropies of complexation of alkali metal cations by a tetraglycol, diglycol-dibenzyl and diglycol-diester derivatives have been obtained from calorimetric measurements. The results revealed that the formation of ML species is controlled by enthalpy while the formation of ML2 from ML is entropy driven.