André De Cian

Thiacalixarenes: Synthesis and structural analysis of thiacalix[4]arene and of p-tert-butylthiacalix[4]arene

The synthesis of tetrathiacalix[4]arene was achieved by the detertiobutylation of p-tert-butyltetrathiacalix[4]arene. X-ray diffraction studies revealed that in the solid state whereas p-tert-butyltetrathiacalix[4]arene forms inclusion complexes with solvent molecules, tetrathiacalix[4]arene undergoes self-inclusion leading to trimeric units. The same behaviour in the crystalline phase was also demonstrated for calix[4]arene.

Versatile Ligands for Palladium‐Catalyzed Asymmetric Allylic Alkylation

Palladium complexes of the chiral diphosphanes 1 and 2 which possess a rigid backbone and a large bite angle catalyze the alkylation of allyl compounds with both high enantioselectivities and reaction rates, particularly with less sterically demanding substrates. 1: R=Me, X=S; 2: R=H, X=C(CH3 )2 .

Further insight into the mechanism of the palladium induced carbocyclisation of aryl rings.

Abstract The depalladation of several cyclopalladated compounds, containing two inserted diphenlacetylenes in the PdC bond has been acheived by treatment with either a neutral coordinating ligand such as pyridine, triphenylphosphine or maleic anhydride. This has afforded carbocyclic compounds where one or two of the aryl groups of the butadienyl chain have been annulated as a result of CC bond formation. These demetallation reactions could be performed under rather mild conditions which enabled the characterisation of an intermediate which in turn provided valuable information about the mechanism of the palladium mediated carbocyclisation reaction.

Synthesis and solid state structural analysis of conformers of tetrakis((ethoxycarbonyl)methoxy)tetrathiacalix[4]arene

The role of alkaline metal cations in the synthesis and in determining the conformer distribution of tetrakis((ethoxycarbonyl)methoxy)tetrathiacalix[4]arene obtained by treatment of tetrathiacalix[4]arene 1 in acetone by ethyl bromoacetate in the presence of M 2 CO 3 was systematically investigated. Among the four possible conformers, the cone, partial cone and 1,3-alternate conformers were obtained, purified and structurally characterised by X-ray analysis in the solid state. Although for Li + no tetra substituted derivative was observed, for Na + the cone conformer was exclusively formed while for both K + and Cs + a mixture of partial cone and 1,3-alternate conformers was obtained.

Charge-assisted N–H(+)···O(−) and O–H···O(−) hydrogen bonds control the supramolecular aggregation of ferrocenedicarboxylic acid and bis-amidines

Directional N–H···O and O–H···O hydrogen bonds reinforced by charge assistance in the presence of anion–cation interactions have been used to design and synthesise a whole family of new organic-organometallic supramolecular salts. The compounds [C5H16N4]2+[(η5-C5H4COO)2Fe]2−·2C2H5OH, 1, [C5H16N4]2+{[(η5-C5H4COOH)(η5-C5H4COO)Fe]2}2−, 2, [C7H20N4]2+[(η5-C5H4COO)2Fe]2−·4H2O, 3, [C7H20N4]2+{[(η5-C5H4COOH)(η5-C5H4COO)Fe]2}2−, 4, and [C7H18O2N4]2+[(η5-C5H4COO)2Fe]2− ·4H2O, 5, have been obtained by reacting [(η5-C5H4COOH)2Fe] with the bis-amidines [C5H14N4], [C7H18N4] and [C7H16O2N4]. The self-assembly between singly and doubly deprotonated acids and the protonated cations is controlled by the stoichiometric ratio and by the choice of solvent. The effect of charge assistance on the N–H···O interactions is discussed on the basis of a CSD analysis.

Tetrasulfinylcalix[4]arenes: Synthesis and solid state structural analysis

The synthesis of two tetrasulfinylcalix[4]arene was achieved by partial oxidation of tetrathiacalix[4]arene precursors. In both cases, the 1,3-alternate conformation of the calix units and the alternate orientation of the sulfoxide groups were demonstrated by X-ray diffraction studies in the solid state. In the case of tetrasulfinylcalix[4]arene, a 3-D network based on stacking interactions between the aromatic groups was observed.

Directed Positioning of Organometallic Fragments Inside a Calix[4]arene Cavity

A hemispherical diphosphane based on a calixarene allows encapsulation of reactive M-R fragments (M=transition metal; R=H, alkyl, CO) inside the calixarene cavity. The ruthenium complex 1 has an unprecedented sandwich structure that contains a CO ligand confined between two phosphane-substituted phenyl rings. The separation between the CO segment and the two aromatic rings is only 2.75 Å!

Photophysical, Electrochemical and Electrochromic Properties of Copper-Bis(4,4'-dimethyl,6,6'-diphenyl-2,2'- bipyridine) Complexes

Abstract The synthesis, solution and solid state structural characterization, photophysical and electrochemical properties of two redox forms of an electrochromic copper-bis(4,4′-dimethyl-6,6′-diphenyl-2,2′-bipyridine) complex, [Cu(3)2]n (n=+1, +2), are presented. Both complexes were characterized in the solid state by X-ray diffraction methods on single-crystals showing that both forms exist in a pseudo-tetrahedral coordination, and a comparison with other structures was made. Like most copper(I) complexes, the red [Cu(3)2]+ complex shows a rather weak emission (Φem=2.7×10−4, dichloromethane). The lifetime of the emitting MLCT state is 34±1 ns, as observed with time resolved emission, and transient absorption (in deoxygenated dichloromethane). Typical emission and transient absorption spectra are presented. The transient absorption spectra indicate that the MLCT state absorbs stronger than the ground state, which is relatively uncommon for metal bipyridine complexes, i.e. no ground state bleaching is observed. The green [(3)2Cu]2+ complex does not show any observable emission or transient absorption, which is a common feature for Cu(II) complexes of this type. The electronic absorption spectra of the chemically and electrochemically produced copper(I/II) complexes are identical. The repeated electrochemical conversion of the Cu(I) center into Cu(II) and vice versa does not cause any decomposition. This is consistent with a fully reversible Cu(I)/Cu(II) redox couple in the corresponding cyclic voltammogram, (E1/2 (Cu(I)/Cu(II))=+0.68 V vs. SCE=+0.23 V vs. Fc/Fc+). These observations indicate that no large structural reorganization occurs upon electrochemical timescales (sub second), and that the different ways of generating the complexes does not effect their final structure, apart from the small differences observed in the X-ray structures of both forms. These characteristics make these complexes rather well suited for their incorporation into an electrochromic display configuration.

Addition compounds of dichlorodioxomolybdenum(VI) with sulfoxides. Molecular structure of [MoO2Cl2(Me2SO)2]

Abstract MoO2Cl2L2 (L=dimethyl sulfoxide (Me2SO), deuterated dimethyl sulfoxide (Me2SO-d6), di-n-buthyl sulfoxide (Bu2SO), tetramethylene sulfoxide (C4H8SO), dibenzyl sulfoxide (Bz2SO), diphenyl sulfoxide (Ph2SO), di-p-tolyl sulfoxide (p-Tol2SO), di-p-chloro-phenyl sulfoxide (p-Cl-Ph2SO) and methyl phenyl sulfoxide (MePhSO)) have been prepared by reacting a solution of MoO2Cl2(H2O)2 in diethyl ether with the respective ligand. The molecular structure of MoO2Cl2(Me2SO)2 has been established by X-ray diffraction analysis. The ability of representative complexes to work as oxotransfer catalysts has been tested.

Multicavitands I: Synthesis and X-ray crystal structure of a bis p-tert-butylcalix[4]arene fused by two silicon atoms

Abstract The synthesis of a receptor possessing two divergent hydrophobic cavities was achieved by fusing two p-tert-butylcalix[4]arene units in cone conformation using silicon atoms. Crystal structure analysis and NMR studies proved the centrosymetric nature of the compound with a 3.75 A distance between the two tetra-coordinated silicon atoms.