Rym Abidi

Piling Up Pillar[5]arenes To Self‐Assemble Nanotubes

New liquid-crystalline pillar[5]arene derivatives have been prepared by grafting first-generation Percec-type poly(benzylether) dendrons onto the macrocyclic scaffold. The molecules adopt a disc-shaped structure perfectly suited for self-organization into a columnar liquid-crystalline phase. In this way, the pillar[5]arene cores are piled up, thus forming a nanotubular wire encased within a shell of peripheral dendrons. The capability of pillar[5]arenes to form inclusion complexes has been also exploited. Specifically, detailed binding studies have been carried out in solution with 1,6-dicyanohexane as the guest. Inclusion complexes have also been prepared in the solid state. Supramolecular organization into the Colh mesophase has been deduced from X-ray diffraction data and found to be similar to that observed within the crystal lattice of a model inclusion complex prepared from 1,4-dimethoxypillar[5]arene and 1,6-dicyanohexane.

Hexa Schiff-base cryptands: solution thermodynamic and X-ray crystallographic studies of main group, transition and heavy metal ion complexes

The complexing properties of three hexaimino cryptands bearing furan (L1), pyridine (L2) and meta-xylyl (L3) groups towards alkali, alkaline earth, Co2+, Ni2+, Zn2+, Cu2+, Cu+, Cd2+ and Ag+ cations have been investigated in acetonitrile, by means of UV–VIS spectrophotometry and/or potentiometry. The formation of both mononuclear (1 : 1) and binuclear (2 : 1) complexes is ligand and cation dependent. L1 and L2 form predominantly 1 : 1 species. However, additional 2 : 1 complexes are found between Cu+ and both ligands and between Ag+ and L1, whereas only 2 : 1 species are formed with Mg2+. With L3, there is generally formation of both the mono- and the bi-nuclear species. The stoichiometries detected in solution are in agreement with those of the solid complexes when they could be isolated. The structures of the monosilver complex with L2 and the disilver complex with L1 are presented. The former shows the silver cation in an unexpected position, as being bonded to three pyridine nitrogen atoms as well as to two imine nitrogen atoms of one side of the macrocycle. The latter shows that the two silver cations are in close proximity [dAg-Ag= 3.115(2)A]. The stability of the complexes, which increases when going from alkali to alkaline earth, transition and heavy metal cations, is always lower than that found for the corresponding diazapolyoxa cryptates in the same medium. Although L2 shows a marked preference for Mg2+ over Ca2+ within the alkaline earths, a lack of selectivity is observed in each series of cations and even between alkaline earth and heavy metal ions, resulting from a remarkable enthalpy–entropy compensation effect demonstrated by the results of the calorimetric study of the complexation of Ca2+, Sr2+, Ba2+ and Ag+ by the two ligands L1 and L2. With regards to the formation of binuclear complexes, no positive cooperative effect has been observed, except for the Mg2+ complexes with L1 and L2 and the Cu+ complex with L3. The calorimetric study of the disilver complexes of L1 shows that there is actually a strongly positive enthalpic cooperatively which is completely offset by the entropic change.

Molecular tectonics: dimensionality and geometry control of silver coordination networks based on pyrazolyl appended thiacalixarenes

Combinations of six new coordinating tectons (3–8) tetrakis-pyrazolyl appended calix[4]arenes, blocked in 1,3-A conformation, based on 1 (tetrathiacalix[4]arene) and 2 (tetrathiatetramercaptocalix[4]arene) derivatives, with AgX salts (X = NO3−, BF4−, XF6− (X = P, As and Sb)) lead to nine new silver coordination networks. The flexible nature of tectons 3–8 (length of the spacer between the macrocycle and the pyrazolyl coordinating unit), their high number of potential coordinating sites and the loose coordination demand of Ag+ cation lead to the formation of a large variety of networks with different dimensionality: from 1D (5-AgSbF6, 5-AgBF4, 7-AgSbF6 and 8-AgNO3) to extended 2D (6-AgBF4 and 8-AgSbF6) and to a series of three isostructural porous diamond-like 3D architectures (6-AgXF6 (X = P, As and Sb)).

Complexation and Transport of Alkali and Alkaline Earth Metal Cations by p-tert-Butyldihomooxacalix[4]arene Tetraketone Derivatives

The binding properties of three p-tert-butyldihomooxacalix[4]arene tetraketone derivatives (tert-butyl 2b, adamantyl 2c and phenyl 2d) in the cone conformation and one derivative (methyl 2a) in a partial cone conformation, towards alkali and alkaline earth metal cations have been established by extraction studies of metal picrates from water into dichloromethane, stability constant measurements in methanol and acetonitrile, and by 1H NMR spectrometry. Transport experiments of metal picrates through a dichloromethane membrane were also performed. The results are compared to those obtained with closely-related calix[n]arene derivatives (n = 4 and 5) and discussed in terms of the substituents, size and conformational effects. Methylketone 2a is a poor binder for all the cations studied, due to its partial cone conformation. Ketones 2b, 2c and 2d show high extraction and complexation levels for the alkali cations, with similar profiles and preference for K+ and Na+ (plateau selectivity). Towards alkaline earth cations, these ketones show a strong peak selectivity for Ba2+ in extraction, but a plateau selectivity for Ca2+, Sr2+ and Ba2+ in complexation. The nature of the substituent attached to the ketone function has some influence on their binding properties, with phenylketone 2d being a slightly weaker binder than ketones 2b and 2c. 1H NMR titrations confirm the formation of 1:1 complexes between the ketones and the cations studied, also indicating that they should be located inside the cavity defined by the phenoxy and carbonyl oxygen atoms. Ketones 2b, 2c and 2d show transport rates that do not follow, in general, the same trends observed in extraction and complexation.

A Rotaxane Scaffold for the Construction of Multiporphyrinic Light-Harvesting Devices

A sophisticated photoactive molecular device has been prepared by combining recent concepts for the preparation of multifunctional nanomolecules (click chemistry on multifunctional scaffolds) with supramolecular chemistry (self-assembly to prepare rotaxanes). Specifically, a clickable [2]rotaxane scaffold incorporating a free-base porphyrin stopper has been prepared and functionalized with ten peripheral Zn(II)-porphyrin moieties. Electrochemical investigations of the final compound revealed a peculiar behavior resulting from the intramolecular coordination of the Zn(II) porphyrin moieties to 1,2,3-triazole units. Finally, steady state investigations of the compound combining Zn(II) and free-base porphyrin moieties have shown that this compound is a light-harvesting device capable of channeling the light energy from the peripheral Zn(II)-porphyrin subunits to the core by singlet-singlet energy transfer.

A correlation between Malva sylvestris extracts molecules and their corrosion inhibition capabilities

Experimental and quantum chemical investigations have been coupled in order to determine anticorrosion potential of Malva sylvestris extract molecules. The plant extract is a mixture of chemicals of which only four are abundant. Two groups of molecules are evidenced using quantum chemical parameters. The electrochemical investigation has classified the plant extract as a mixed-type inhibitor. The %EI has been only 54.5% due to antagonistic effects of the extract molecules.

Synthesis of para- and meta-imino- or -amino-methyl pyridyl-appended p-tert-butyl-calix[4]arene or p-tert-butyl-thiacalix[4]arene in 1,3-alternate conformation

Herein, the multistep synthesis of eight new ligands based on either calix[4]arene or thiacalix[4]arene backbone blocked in a 1,3-alternate conformation was achieved. Both types of backbones were functionalized with pyridyl coordinating units using either imino or amino junctions. The introduction of the pyridyl units was achieved using either the position 3 (meta) or 4 (para) of the aromatic moiety. Moreover, four out of the eight ligands were structurally investigated in the solid state via X-ray diffraction methods on single crystals.

Hybrid material based on clay and calixarenic derivatives

Hybrid nanocomposites were obtained in this study by solid–solid reaction based on calixarenic derivatives and natural Tunisian clay: clay-calixarene. For this purpose, two calixarenic derivatives were synthesized and their properties were studied. Results show their affinity towards bivalent mercury and lithium by complexation in a homogeneous medium and vis-a-vis the rubidium by extraction of water to dichloromethane. The clay was purified and characterized by means of X-ray diffraction, X-ray fluorescence, cation exchange capacity and BET techniques. Intercalation of the calixarenes in the interfoliar space of the clay has been demonstrated by the spacing of the basal space after reaction and the comparison of infrared spectra confirms that the reaction has taken place. In addition, these hybrids have developed important specific surfaces area. Both nanocomposites prepared are among the first synthesis of clay-calixarenic hybrids in solid state. According to the calixarenic structures, it is assumed that these materials were of class II hybrids.