Synthesis, structure and anion binding properties of lower rim α-hydroxyamide calix[4]arene derivatives

A new family of p-tert-butylcalix[4]arenes functionalized at the lower rim with α-ketoamide or α-hydroxyamide functions has been prepared. The ¹H and ¹³C NMR spectra indicate that the macrocycles preferably adopt a cone conformation. X-ray crystal study of the α-ketoamide derivative 4a shows the flattened cone conformation in the solid state. Reduction of α-ketoamide 4ab has produced the α-hydroxyamide derivatives 6ab. The introduction of chiral moieties on the lower rim position of the calix[4]arene allowed the synthesis of the chiral derivatives 7 and 8. Host-guest complexation properties towards various anions of the chiral α-hydroxyamide 8 have been examined by ¹H NMR spectroscopy. This new receptor has shown promising selectivity for and N-tosyl-(L)-alaninate.     

Complexes in the Naphthoquinone Series: Crystal Structures,Electronic Structures,Stability

It is shown that the charge transfer is negligible in the ground state for organic charge transfer complexes between phenols and quinones. Our objective Is to determine the origin of the stability of the complexes. The geometric, electronic and energetic properties of these complexes were examined by three techniques, crystal structure determination by X-ray diffraction, spectrum and charge transfer calculation by quantum chemical methods, and lattice energy computation.     

Synthesis and Reductive Complexation Properties of a Cone-Configurated Tetra[p-(tert-butyl)]calix[4]arene incorporating bipyridyl and pyridine subunits. NMR characterization and crystal structure of its chiral copper(I) complex

The hetero-armed p(tert-butyl)calix[4]arene 1 was synthesized by a stepwise procedure. This ligand presented a very strong complexing behavior towards Cu¹, giving the chiral complex 2 and parent species when reacted with Cu^II salts. High-resolution NMR techniques were employed for the characterization of 2 , demonstrating notably exchange processes between its two enantiomeric forms. The racemic nature of 2 was confirmed by X-ray crystal-structure analysis.     

An efficient regio-specific synthetic route to multiply substituted acyl-sulphated β-cyclodextrins

The regio-specific synthesis of a series of novel amphiphilic β-cyclodextrins is described. We are able to check the degree of sulphatation at upper rim and the degree of acylation and over-acylation at lower rim by electrospray mass spectrometry. The 6-O-silyl-2,3-O-acyl-β-cyclodextrin is synthesised in large scale by one pot reaction from β-cyclodextrin. The products are generally mixtures with varying degrees of substitution. These amphiphilic cyclodextrin form micellar aggregates.     

Derivation of a nine variable model of a U-tube steam generator coupled with a three-element controller

In this work a U-Tube Steam Generator – UTSG model derivation is presented. This model was developed as test bed to build a complete power plant simulator. The UTSG is an ordinary component of most of the Pressurized Water Reactor – PWR. A proportional-integral three-element controller was also coupled with the UTSG model. This model is part of a library called SIMODIS – SImulation MODeling Integrated System (“SIstema MODular Integrado de Simulação”). A few transient results are presented as well. The developed simulation program was implemented in MATLAB.     

Synthesis and NMR conformational studies of p-tert-butyldihomooxacalix[4]-arene derivatives

Abstract

The tetramethyl (2) and tetraethyl (3) ethers, and the tetraacetate (4) derivatives of the p-tert-butyldihomooxacalix[4]arene were prepared. The mobility of these compounds studied by temperature-dependent ¹H NMR spectroscopy. For the tetraacetate derivative, at room temperature, 1,2- or 1,3-alternate conformations are suggested. Those conformations were confirmed by NOE difference and COSY spectra for the tetraethyl ether derivative in CDCl₃ at -20°C.