Synthesis and Characterization of P-tert-Butyl-calix[9, 10, 11 and 12]arenes.

The p-tert-butylcalix[n]arenes (n = 9, 10, 11, 12) have been co-synthesized in significant amounts from cyclocondensation reaction mixture of linear phenolic oligomers in basic conditions. They have been isolated and fully characterized.     

Selective Mono-Dealkylation of Tetra-p-tert-butyl-calix[4]arene at the Upper Rim

The tris-p-(tert-butyl)calix[4]arene has been synthesized by a reproducible selective esterification-dealkylation-saponification process.     

Palygorskite organophilic for dermopharmaceutical application

Due to the growing interest of the population in natural treatments, the clays represent a good alternative to the treatment of wounds. Its modification by organophilization happens when the same inorganic cations are exchanged for organic cations of the surfactant used in the process. Thus, the clay has the properties of its surface modified from being hydrophilic to hydrophobic, improving its functionality on the skin. In order to determine changes in surface palygorskite and to assess its healing action, this clay was organophilizated by two cationic surfactants: dimethyl benzyl ammonium chloride alkyl, and cetyl trimethyl ammonium chloride, and characterized by sieve analysis, property flow, test oil adsorption, and the techniques of X-ray fluorescence, X-ray diffraction, infrared Fourier transform, thermogravimetric analysis, scanning calorimetry—differential and histological of cutaneous wounds in rats. The results indicate that the attapulgite has good rheological properties, a high capacity of adsorption of oil, and the presence of clay minerals that reduce inflammation. The analysis by X-ray fluorescence is not observing any change in the crystal structure of palygorskite organophilizated but through infrared spectroscopy Fourier transform, verifying the interaction and incorporation of the clay ammonium salts, as well as thermoanalytical analysis also suggests that the organophilic process reduces the hydrophilic character of palygorskite. The histological analysis showed healing effect after topical application of natural and organophilizated clay in skin wounds in rats. These analyses favor a good prospect of its application in dermopharmaceuticals, because the use of palygorskite provides greater interaction with skin and heals wounds.     

Pinched-cone Calix[6]arene: New Synthesis of p- (1,1,3,3-tetramethylbutyl)calix[6]arene. Structure of its 1 : 3 Complex with Chloroform

A new method is described for the synthesis of p-(1,1,3,3-tetramethylbutyl)calix[6]arene isolated ina 30 % yield. For the first time the crystal structure isgiven. The crystals are monoclinic, space group C2/c,a = 24.144(5) Å, b = 14.093(3) Å,c = 26.972(5) Å, = 93.36(3)^circ, V = 9162(3) ų, Z = 4. The macrocycle with C2symmetry presents the pinched-cone conformation. It crystallizes with three chloroform molecules, two of them are positioned in the cones shaped by the phenol moieties; the third chloroform is located in the cavity near the hydroxyl groups; this solvent molecule is disordered around the 2 axis. The packing of the complex is described.     

Fluorescence Quenching of 2,2′-Bithiazole-Containing Calix[4]arenes by Copper(I). Access to the corresponding [ML2], [ML], and [M2L] copper(I) complexes

The complexing behaviour of 2,2′-bithiazole-containing calix[4]arenes towards Cu¹ was investigated. The extinction of the intrinsic blue fluorescence of the free ligands upon addition of stoichiometric amounts of the metallic salt was used as complexation probe. This extinction was directly related to the chelation of the metal and allowed the controlled synthesis of new mono- and dimetalic complexes which were fully characterized.     

Large Calixarenes: Structure and Conformation of a Calix[16]arene Complexed with Neutral Molecules

A crystal of an inclusion compound between a calix[16]arene and molecules ofacetonitrile and dichloromethane, used as solvents, has been obtained and its X-raystructure studied. The cell is monoclinic, space group C2/c with a = 38.508(8) Å,b = 21.593(4) Å, c = 26.625(5) Å and = 121.34(3)°.The macrocycle is in the form of two superimposed celtic torcs connected by theirextremities.¹ Two acetonitrile molecules are situated in the middleof this double torc, two dichloromethane molecules are encapsulated in the pseudocalix[4]arenes obtained on both extremities of the torcs by the folding of the lastfour phenolic rings. A disorder is observed for the other acetonitrile and dichloromethanemolecules situated outside the macrocycle.     

Synthesis,Conformational Analysis and Extraction Studies of p-isopropylcalix[n]arene Derivatives (n = 4, 6, 8). A New Family of Molecular Receptors

Abstract

Ethers, esters and ketones, derivatives of p-isopropylcalix[n]arenes (n = 4,6,8), have been prepared; 33 new molecular receptors have been isolated and fully characterized. ¹H NMR and ¹³C NMR measurements reveal that tetraester and tetraketone derivatives are in cone conformation at room temperature when hexa and octa derivatives look like flexible flattened cones. Extraction studies with metal picrates from aqueous solution into dichloromethane were used to assess the ionophoric activity of the p- isopropylcalix[n]arene derivatives. The better E% are obtained with tetrameric derivatives in cone conformation, fully functionalized on the phenolic oxygens by ester or ketonic groups. The tetraamide derivative is the most efficient binder; the E% values are around 100 for Li, Na, K, Rb, Cs, Ca and Ba.