Synthesis and properties of oligo[n]cruciforms: nanosized sterically encumbered tetraethynylphenyl-homologated fluorophores.

A series of nanosized phenyleneethynylenes have been prepared which are sterically insulated from the surrounding environment by multiple functionalization with triisopropylsilyl (TIPS) substituents. The phenyleneethynylenes comprise oligo[n]cruciforms 1-4 (n = 3-5) and a dehydrotribenzo[12]annulene 5, the former of which possess para-acyclic and the latter ortho-cyclic electronic conjugation pathways. All compounds were characterized by (1)H and (13)C NMR, IR, and mass spectroscopic techniques. The X-ray crystal structure of 1 confirmed the sterically isolating properties of the TIPS substituents. A comparison of the physical properties of these electronically differing systems revealed that they were all luminescent upon UV irradiation displayed negligible aggregation in dilute solution and that particular members of the series studied were electrochemically active, undergoing facile reversible reductions. The phenyleneethynylenes also exhibited significantly enhanced thermal stability by virtue of the presence of the TIPS substituents. The properties of 1-5 suggest that they are promising building blocks for the construction of materials for novel molecular electronics applications.

Arranging up to six ferrocene carboxamides around metal centres.

Ferrocene carboxamide, FcCONH(2), forms homo- and heteroleptic complexes with Co(II), Ni(II) and Cu(II) via coordination of its carbonyl group. Whereas for both Co(II) and Ni(II), hexaferrocenyl complexes are obtained in the presence of BF(4)(-) anion, in the case of Cu(II) a tetraferrocenyl species is observed in the presence of triflate anion.

Direct orthoruthenation of planar prochiral pyridine derivatives by C-H bond activation with [Ru(CO)2Cl2]n and its unexpected stereoselectivity.

The treatment of planar prochiral pyridine derivatives with d6 [Ru(CO)2Cl2]n stereoselectively and efficiently produces new dimeric ortho-ruthenated complexes.

New manganese-scaffolded organic triple-deckers based on quinoxaline, pyrazine and pyrimidine cores.

The thermolytic coupling of Ph(2)CN(2) and (t-Bu)(Ph)CN(2) with doubly cyclomanganated 2,5-diphenylpyrazine and 4,6-diphenylpyrimidine afforded substantial amounts of new triple decker compounds of either C(i) and C(2) symmetry respectively containing, in both series, two eta(3)-bonded Mn(CO)(3) fragments which intervene as scaffolds sustaining the helical non-conjugated triaryl backbone. The molecular structures of two pyrazine derivatives show a typical non-parallel stacking of the aromatic rings and the encapsulation of the central pyrazyl fragment with interplanar centroid-to-centroid distances of ca. 3.5 A. The stacking of the aromatics in the triple-decker pyrimidine derivatives has been assessed by (1)H NMR experiments at low temperature. All the triple-decker-type compounds are electroactive. Pyrimidine triple-deckers can reversibly be electrochemically reduced to the corresponding anions.

Novel heteroleptic cis-(C--N)2Pd(II) chelates for the preparation of enantiopure planar chiral cyclopalladated 2-[tricarbonyl(eta6-phenyl)chromium]pyridine.

In the presence of large amounts of [Me4N]Cl, the reaction of ortho-chloromercurated 2-[(eta6-phenyl)tricarbonylchromium]pyridine with mu-chloro cyclopalladated aromatic compounds yields a series of new heteroleptic heterodinuclear cis-(C--N)2Pd(II) complexes, which are valuable precursors of planar chiral cyclopalladated (eta6-arene)Cr(CO)3 complexes.

Expression of the prohelicity of bis-cyclomanganated 2,3-diphenylquinoxaline through reactions with diaryldiazomethanes.

The reactions of bis-cyclomanganated 2,3-diphenylquinoxaline with diazodiphenylmethane and 9-diazofluorene allowed the formation of a new oligomeric and dinuclear manganospiralene and the ready preparation of a pentacyclic helix comprising two (eta 5-fluorenyl)Mn(CO)3 fragments, whose helicity can be locked upon one-dimensional linear coordination to silver cation.

Design of 3-D coordination networks: topology and metrics.

Using 4,4',4"-tricyanotriphenylmethanol 1 as a heterotetradentate tecton with C3v symmetry bearing three CN and one OH group, under self-assembly conditions a 3-D coordination network was obtained in the presence of Ag+ cations acting as a tetrahedral metallic tecton; due to the metrics of 1 (three long and one short distance between the central C atom and N and O coordination sites, respectively), the 3-D network is of pseudo-diamondoid type with different cavity sizes; although a two-fold homo-interpenetration is observed for the 3-D networks, the remaining space is occupied by CHCl3, MeOH solvent molecules and SbF6- anions.

Koilands from thiophiles: mercury(II) clusters from thiacalixarenes.

Tetra- and hexa-nuclear mercury(II) complexes have been obtained from tetrathiacalix[4]arene and tetramercaptotetrathiacalix[4]arene, respectively, and structurally characterised in the solid state; the complexes provide new digonal and trigonal receptors of the koiland type.

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!

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 .

Effect of a Phosphazene Base on the Diastereoselectivity of Addition of alpha-Sulfonyl Carbanions to Butyraldehyde and Isopropylideneglyceraldehyde.

The effect of tBuP4, a strong and cation-free base, on the yield and diastereoselectivity of additions of thus formed "naked" alpha-sulfonyl carbanions to achiral butyraldehyde and chiral isopropylideneglyceraldehyde was studied. It has been found that with tBuP4 a reasonable yield ( approximately 55%) and a slightly better diastereoselectivity (72% of the anti diastreomer) are obtained with achiral and nonfunctionalized butyraldehyde while with isopropylideneglyceraldehyde the use of tBuP4 allowed us to greatly increase the yields (up to 95-100%) and the diastereoselectivities (83-89% of a single diastereomer over the four possible diastereomers). It was also shown that the extra oxygen atom in the alpha-position plays a determinant role in this effect.