Browsing by Author "Loeb, B"

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    Synthesis, crystal structure, molecular orbital calculations and electronic properties of 2,3-di(2-pyridyl)naphtho[2,3-f]quinoxaline-7,12-quinone (Aqdpp)
    (ROYAL SOC CHEMISTRY, 1998) Lopez, R; Boys, D; Loeb, B; Zuloaga, F
    The synthesis, characterization and crystal structure of 2,3-di(2-pyridyl)naphtho[2,3-f]quinoxaline-7,12-quinone (Aqdpp) are reported. Molecular orbital calculations have been carried out in order to characterize its reactivity and coordination properties. surface maps for the electronegativity, hardness and Fukui functions have been generated to identify local reactivity sites and the crystal structure has been compared with the optimized geometry with good correlation among them. The acceptor properties of the Aqdpp ligand are shown by the orbital map for the LUMO level contributed mainly by the quinonic region of the ligand.
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    Trans ruthenium(II) complexes with NH-bridged tetradentate symmetric and asymmetric polypyridyl ligands
    (2002) Concepción, J; Just, O; Leiva, AM; Loeb, B; Rees, WS
    NH-Bridged tetradentate ligands were synthesized to achieve stable trans Ru(II) bis(polypyridyl) complexes. The polypyridyl part of the ligand was either symmetric, as in N,N-bis(1,10-phenanthroline2-yl)amine (phen-NH-phen), or asymmetric, as in N-(1,10-phenanthroline-2-yl)-N-(6-yl-dipyridyl[2,3-a:2',3'-c]phenazine)amine (dppz-NH-phen). Protonation of phen-NH-phen with trifluoroacetic acid and the subsequent reaction with RuCl3 yield trans-[Ru(phen-NH-phen)Cl-2]. The chloro ligands in this compound can easily be replaced by stronger ligands, such as CH3CN and DMSO. In this way, complexes trans-[Ru(phen-NH-phen)(CH3CN)(DMSO)](PF6)(2) (1), trans-[Ru(phen-NH-phen)(DMSO)(2)](PF6)(2) (2), and trans-[Ru(phen-NH-phen)(CH3CN)(2)](PF6)(2) (3) were obtained. X-ray structures were determined for 1 and I Following a procedure similar to that used with phen-NH-phen, the complex trans-[Ru(dppz-NH-phen)(CH3CN)(2)](PF6)(2) (4) was obtained. To our knowledge, this is the first reported trans ruthenium(II) bis(polypyridyl) complex with two different polypyridyl ligands in the equatorial plane.
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    Tuning the excited states in fac-[Re(X2dppz)(CO)3(L)]
    (2004) López, R; Loeb, B; Striplin, D; Devenney, M; Omberg, K; Meyer, TJ
    Excited state lifetime measurements - emission, emission lifetime and Resonance Raman - have been conducted on the series fac-[Re(X(2)dppz)(CO)(3)(L)](0,+) (L = Cl-, 4-ethylpyridine (4-Etpy), 4,4'-bipyridine (4,4'-bpy)), with the X(2)dppz substituted dipyrido[3,2-a:2',3'-c] phenazine ligands (X = CH3 and Cl). The results are consistent with closely lying excited states, with pipi* lowest, but MLCT contributing significantly to excited state lifetimes for the neutral complexes. fac-[Re(Cl(2)dppz)(CO)(3)Cl] appears to undergo a crossover from lowest pipi* to lowest MLCT through the glass to fluid transition.