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Abstract:In order to construct bimetallic organometallic donor-acceptor complexes with nonlinear optical (NLO) properties, the bimetallic sesquifulvalene com-

Reaction of the ynamine MeC⋮CNEt2 with the pentatetraenylidene complexes [(CO)5MCCCCC(NMe2)2] (M = Cr (3a), W (3b)) at room temperature affords the new heptapentaenylidene complexes [(CO)5MCCCCC(NEt2)C(Me)C(NMe2)2] (M = Cr (5a), W (5b)) in good yield. The spectroscopic data and the X-ray structural analysis of 5a indicate that these amino-substituted metallacumulenes are best described as hybrids of a cumulene and several strongly polarized alkynyl structures. For 5a and the related metallacumulenes [(CO)5MCCC(NMe2)2] (M = Cr (1a), W (1b)), [(CO)5CrCCC(NEt2)C(H)C(NMe2)2] (2a), and 3a,b the molecular first hyperpolarizability β was determined by hyper-Rayleigh scattering experiments. The insertion of a cumulated C2 unit into a metallacumulene quadruples β, while the insertion of a conjugated C2 unit results in only slight enhancement of the second harmonic generation response. Substitution of tungsten for chromium has only a minor effect on β. All observed β values are reasonably high compared with those of other organometallic compounds.

The syntheses of methyl 2,3-diamino-4,6-Obenzylidene-2,3-dideoxy-α-D-hexopyranosides of glucose, mannose, gulose, and talose and methyl 2-amino-4,6-benzylidene-2,3-dideoxy-3-tosylamido-α-D-glucopyranoside are exhaustively presented, as well as their application as ligands in halfsandwich ruthenium(II), rhodium(III), and iridium(III) complexes. The complex formation occurs highly diastereoselectively, creating a stereogenic metal center. The molecular structures of the ligands and their complexes were investigated by X-ray structure analysis, NMR spectroscopy, polarimetry, and DFT methods. The diamino monosaccharide complexes have been subjected to antitumor activity studies. In vitro tests of a few ruthenium complexes against different cancer cell types showed antiproliferative activities 4−10 times lower than that of cisplatin.

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Magnetic sandwich complexes are of particular interest for molecular spintronics. Using scanning tunneling microscopy, we evidence the successful deposition of 1,3,5-tris(η-borabenzene-η-cyclopentadienylcobalt) benzene, a molecule composed of three connected magnetic sandwich units, on Cu(111). Scanning tunneling spectra reveal two distinct spatial-dependent narrow resonances close to the Fermi level for the trimer molecules as well as for molecular fragments composed of one and two magnetic units. With the help of density functional theory, these resonances are interpreted as two Kondo resonances originating from two distinct nondegenerate d-like orbitals. These Kondo resonances are found to have defined spatial extents dictated by the hybridization of the involved orbitals with that of the ligands. These results opens promising perspectives for investigating complex Kondo systems composed of several "Kondo" orbitals.

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The donor‐acceptor complexes with a vinylogue monohydro sesquifulvalene and sesquifulvalene backbone of the type [(η5‐C5H5)Ru{µ‐(η5‐C5H4)C2H2(η6‐C7H7)}ML](PF6)n [n = 0: ML = none (1), Cr(CO)3 (2); n = 1: ML = Ru(η5‐C5H5) (3a), Ru(η5‐C5Me5) (3b)] and [(η5‐C5H5)Ru{µ‐(η5‐C5H4)C2H2(η7‐C7H6)}ML](PF6)n [n = 1: ML = none (4), Cr(CO)3 (5); n = 2: ML = Ru(η5‐C5H5) (6a), Ru(η5‐C5Me5) (6b)], respectively, have been synthesised, and spectroscopically and structurally characterised. A charge‐shift correlation was carried out by means of 1H NMR spectroscopic studies and an increased ground‐state donor‐acceptor interaction in the order 5 < 6b < 4 < 6a was found. The corresponding donor‐acceptor interaction in 3a and 3b varies by an insignificant amount. Hyper‐Rayleigh scattering (HRS) was applied to determine the first hyperpolarisability β of the mono‐ and dicationic complexes 3a−6b. The β values obtained for the cationic sesquifulvalene complexes 4−6b are among the largest ever measured for ruthenocenyl containing complexes due to a strong resonance enhancement: the sesquifulvalene complexes 4−6a, 6b show first hyperpolarisabilities which range between 360 and 700 × 10−30 esu, whereas β for the monohydrosesquifulvalene complexes are considerably lower (75 and 162 × 10−30 esu). For the latter complexes the first hyperpolarisability doubles on going from Ru(η5‐C5Me5) (3b) to Ru(η5‐C5H5) (3a) in the acceptor unit. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)