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Pardo, Emilio; Ruiz-García, Rafael; Cano, Joan; Ottenwaelder, Xavier; Lescouëzec, Rodrigue; Journaux, Yves; Lloret, Francesc; Julve, Miguel
doi: 10.1039/b801222apmid: 18478138
The aim and scope of this review is to show the general validity of the ‘complex-as-ligand’ approach for the rational design of metallosupramolecular assemblies of increasing structural and magnetic complexity. This is illustrated herein on the basis of our recent studies on oxamato complexes with transition metal ions looking for the limits of the research avenue opened by Kahn's pioneering research twenty years ago. The use as building blocks of mono-, di- and trinuclear metal complexes with a novel family of aromatic polyoxamato ligands allowed us to move further in the coordination chemistry-based approach to high-nuclearity coordination compounds and high-dimensionality coordination polymers. In order to do so, we have taken advantage of the new developments of metallosupramolecular chemistry and in particular, of the molecular-programmed self-assembly methods that exploit the coordination preferences of metal ions and specifically tailored ligands. The judicious choice of the oxamato metal building block (substitution pattern and steric requirements of the bridging ligand, as well as the electronic configuration and magnetic anisotropy of the metal ion) allowed us to control the overall structure and magnetic properties of the final multidimensional nD products (n = 0–3). These species exhibit interesting magnetic properties which are brand-new targets in the field of molecular magnetism, such as single-molecule or single-chain magnets, and the well-known class of molecule-based magnets. This unique family of molecule-based magnetic materials expands on the reported examples of nD species with cyanide and related oxalato and dithiooxalato analogues. Moreover, the development of new oxamato metal building blocks with potential photo or redox activity at the aromatic ligand counterpart will provide us with addressable, multifunctional molecular materials for future applications in molecular electronics and nanotechnology.
Wang, Yuanyuan; Lin, Ronger; Yip, John H. K.
doi: 10.1039/b802957apmid: 18478139
A nanoscopic pseudorotaxane (1)2⊃2 composed of the gold rectangle [Au4(μ-PAnP)2(μ-bipy)2](OTf)41 and the linear template 4,4′-bis(9″-anthryl)biphenyl 2 was assembled (PAnP = 9,10-bis(diphenylphosphino)anthracene); bipy = 4,4′-bipyridine).
Padmanabhan, M.; Joseph, James C.; Thirumurugan, A.; Rao, C. N. R.
doi: 10.1039/b718623apmid: 18478140
Reaction of a molecular Co(ii) maleate, [Co(Hmal)2(H2O)4], with pyridine yields a Co(ii) fumarate, [Co(fum)(H2O)4], with a chain structure and a chiral pyridylsuccinic acid zwitter ion, −OOC–CH(N+C5H5)–CH2–COOH, in almost quantitative yields, while the reaction of 4,4′-bipyridine (bipy) with the Co(ii) maleate, on the other hand, almost quantitatively generates a polylmeric Co(ii) maleate, [Co(mal)(bipy)]n·(n/2)H2O along with the adduct of fumaric acid with bipyridine.
Suresh, D.; Balakrishna, Maravanji S.; Rathinasamy, Krishnan; Panda, Dulal; Mobin, Shaikh M.
doi: 10.1039/b804026ppmid: 18478141
The newly synthesized water-soluble cyclodiphosphazane ligands and their gold(i) complexes inhibit HeLa cell proliferation by activating p53 protein and inducing apoptosis.
John, Alex; Shaikh, Mobin M.; Ghosh, Prasenjit
doi: 10.1039/b801496epmid: 18478142
A structural and functional mimic of the galactose oxidase (GOase) enzyme active-site by a copper complex supported over a sterically demanding ligand having [N2O2] donor sites is reported. Specifically, the binding of the histidine (496 and 581) and tyrosine (272 and 495) residues to the copper center in a square-pyramidal fashion in the active-site of galactose oxidase (GOase) enzyme has been modeled in a copper complex, {[(3-tert-butyl-5-methyl-2-hydoxybenzyl)(3′-tert-butyl-5′-methyl-2′-oxobenzyl)(2-pyridylmethyl)]amine}Cu(OAc)} (1b), stabilized over a sterically demanding ligand in which the two phenolate-O atoms mimicked the tyrosine binding while an amine-N and pyridyl-N atoms emulated the histidine binding to the metal center, similar to that in the enzyme active-site. Furthermore, the copper complex 1b is found to be an effective functional model of the enzyme as it efficiently catalyzed the chemoselective oxidation of primary alcohols to aldehydes in high turnover numbers under ambient conditions. An insight into the nature of the active-species was obtained by EPR and CV studies, which in conjunction with the DFT studies, revealed that the active-species is an anti-ferromagnetically coupled diamagnetic radical cation, 11b+, obtained by one electron oxidation at the equatorial phenolate-O atom of the ligand in the 1b complex.
Al-Ktaifani, Mahmoud M.; Hitchcock, Peter B.; Lappert, Michael F.; Nixon, John F.; Uiterweerd, Philip
doi: 10.1039/b800458gpmid: 18478143
Treatment of the cage compound P6C4tBu4 with M{N(SiMe3)2}2 (M = Ge or Sn) or Pb(C6H3(NMe2)2–2,6) at room temperature results in their specific insertion into the P–P bond connecting the two 5-membered P3C2tBu2 rings. The products were fully characterised by multinuclear NMR spectroscopy and single crystal X-ray diffraction studies.
Cordero, Beatriz; Gómez, Verónica; Platero-Prats, Ana E.; Revés, Marc; Echeverría, Jorge; Cremades, Eduard; Barragán, Flavia; Alvarez, Santiago
doi: 10.1039/b801115jpmid: 18478144
A new set of covalent atomic radii has been deduced from crystallographic data for most of the elements with atomic numbers up to 96. The proposed radii show a well behaved periodic dependence that allows us to interpolate a few radii for elements for which structural data is lacking, notably the noble gases. The proposed set of radii therefore fills most of the gaps and solves some inconsistencies in currently used covalent radii. The transition metal and lanthanide contractions as well as the differences in covalent atomic radii between low spin and high spin configurations in transition metals are illustrated by the proposed radii set.
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