Jean Weiss

Synthesis and properties of double-calix[4]-arenes, doubly-crowned calix[4]-arenes, and double-calix-crowns

Syntheses of double-calix(4)arenes, doubly- crowned calix(4larenes, and double-calix-crowns have been achieved by reacting p-tert-butylcalix(4larene or a new mesitol based calixL41arene with various polyethylene glycol ditosylates in the presence of potassium carbonate in refluxing acetonitrile. Depending on the nature of the ditosylate and on the reaction times are differently obtained calixarene ligands. The complexation properties toward alkali cations are presented for the double-calix-crown derived of p-tert-butylcalix(4larene.

Quick synthesis of the first double porphyrin double calix[4]arene

Abstract The condensation of dipyrrylmethane and calix[4]arene 1,3 dialdehyde in dilute conditions afforded in very low yield the first double porphyrin linked by two calix[4]arene units.

Surface-Tuned Assembly of Porphyrin Coordination Oligomers

Two self-complementary phenanthroline-strapped porphyrins bearing imidazole arms and C 12 or C 18 alkyl chains were synthesized, and their surface self-assembly was investigated by atomic force microscopy (AFM) on mica and highly ordered pyrrolitic graphite (HOPG). Upon zinc(II) complexation, stable porphyrin dimers formed, as confirmed by DOSY (1)H NMR and UV-visible spectroscopy. In solution, the dimers formed J-aggregates. AFM studies of the solutions dip-coated onto mica or drop-casted onto HOPG revealed that the morphologies of the assemblies formed were surface-tuned. On mica, fiber-like assemblies of short stacks of J-aggregates were observed. The strong influence of the micas epitaxy on the orientation of the fibers suggested a surface-assisted assembly process. On HOPG, interactions between the alkyl chains and the graphite surface resulted in the stabilization and trapping of monomer species followed by their subsequent association into coordination polymers on the surface. Interdigitation of the alkyl chains of separate polymer strands induced lateral association of wires to form islands that grew preferentially upon drop-casting and slow evaporation. Clusters of laterally assembled wires were observed for the more mobile functionalized porphyrins bearing C 12 chains.

Zinc(II)-porphyrin Receptors in Multi-point Molecular Recognition: Recent Progress

The tremendous efforts made in order to control the coordination chemistry of hemoprotein models have considerably enhanced the synthesis of functionalized porphyrins, whose carefully designed architectures allowed for selective bindings of exogenic substrates. The common use of zinc(II) in place of pentacoordinated iron(II) has induced the use of zinc(II) porphyrins as building blocks for selective receptors. These receptors offer a convenient combination of multi-point recognition of substrates, and monitoring of the complexation due to the chromophoric nature of the tetrapyrrolic unit. This review is dedicated to recent progress made in the field of molecular recognition involving multi-point selective binding processes, in whichthe establishment of a strong coordination bond is finely tuned by one or more weak interactions adequately introduced in the architecture of a functionalized zinc(II)-porphyrin.

A self-assembling receptor for dicarboxylic acids

In this paper we describe a simle binding subunit that self-assembles in the presence of metal ions to form a receptor for dicarboxylic acids. The resultant binding site is chiral and strong complexation to dicarboxylic acids in CDCl3 can be detected by both NMR and UV-vis spectroscopies.

Interlocked macrocyclic ligands: a catenand whose rotation of one ring into the other is precluded by bulky substituents

Abstract A new highly rigid catenand has been synthesized. It contains two interlocked rings whose reciprocal motions are highly restricted, making the topography of the copper(I) catenate similar to that of the free ligand.

Efficient combination of calix[4]arenes and meso-diphenylporphyrins

Abstract The selective mono-alkylation of a calix[4]arene with a functionalized benzaldehyde followed by the condensation with dipyrrylmethane afforded in good yield a porphyrin substituted by two calix[4]arenes. The same multisite ligand was alternatively obtained by double monoalkylation of two calix[4]arenes with a functionalized porphyrin. The two calixarene units are in cone shape and thus can accomodate neutral organic guests. The efficiency of the fluorescence quenching of two porphyrins by benzoquinone has been evaluated and compared. In a first approximation, Stern-Volmer plots provide evidence for an enhanced quenching when calixarene hosts are bound to the porphyrin.

Spectroscopic, crystal structural and electrochemical studies of zinc(II)-Schiff base complex obtained from 2,3-diaminobenzene and 2-hydroxy naphthaldehyde.

Mononuclear zinc(II) complex, [Zn(II)L], where L is a dianionic ligand, has been synthesized and characterized by elemental analysis, electronic, IR and NMR [(1)H, (13)C, DEPT, (1)H-(1)H COSY, ROESY, HSQC and HMBC] spectroscopic techniques. Structural analysis of the complex by single crystal X-ray crystallography shows the presence of a distorted square planar coordination geometry (NNOO) of the metal center. The crystal of the title complex C28H18N2O2Zn belongs to the orthorhombic system with space group Pmn21. Electrochemical behavior of the Zn(II)L complex has been investigated by cyclic voltammetry on glassy carbon and platinum electrodes in DMF at 100 mV/s scan rate.

Highly linear self-assembled porphyrin wires.

An efficient noncovalent assembly process involving high geometrical control was applied to a linear bis(imidazolyl zinc porphyrin) 7Zn, bearing C(18) substitutents, to generate linear multiporphyrin wires. The association process is based on imidazole recognition within the cavity of the phenanthroline-strapped zinc porphyrin. In chlorinated solvents, discrete soluble oligomers were obtained after (7Zn)(n) was end-capped with a terminal single imidazolyl zinc porphyrin derivative 4Zn. These soluble species, as well as their destabilization in the presence of protic solvents, were studied by UV-visible and time-resolved luminescence. In the solid state, assemblies as long as 480 nm, which corresponds to 190 iterative units or a total of 380 porphyrins, were observed by atomic force microscopy measurements on mica. The length and linearity of the porphyrin wires obtained illustrate the potential of phenanthroline-strapped porphyrins for the directional control of self-assembly processes.

Cyclotriveratrylene as preorganizing matrix : a new tripole ligand.

Abstract The synthesis of a tripode ligand combining three pyridine rings arranged around a rigid derivative of cyclotriveratrylene is described.