Browsing by Author "Arancibia, A"
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- ItemAn ALMA survey of submillimeter galaxies in the COSMOS field : Multiwavelength counterparts and redshift distribution(2017) Brisbin, D; Miettinen, O; Aravena, M; Smolcic, V; Delvecchio, I; Jiang, C; Magnelli, B; Albrecht, M; Arancibia, A; Padilla, Nelson; Aussel, H; Baran, N; Bertoldi, F; Bethermin, M; Capak, P; Casey, C
- ItemFe(II)-Fe(III) electronic and magnetic interaction through a thiopyridine bridge.(2000) Díaz, C; Spodine, E; Moreno, Y; Arancibia, AReaction of CpFe(dppe)I with dithiopyridine in methanol and in presence of NH,PF, affords the new mixed valence complex {[CpFe(dppe)](2)-mu-S-Py}(PF6)(2) (1). Observation of an intervalence electron transfer affords the Hush parameters that permit to classify this compound as a type II Robin Day complex. The electron transfer across the pyridinethiolate ligand occurs at a rate estimated to be about 10(6) seg(-1). Variable - temperature magnetic susceptibility measurements have been carried out in the range of 5-300 degrees K. Results can be interpreted as principally due to weak intermolecular antiferromagnetic interactions between Fe (II) - Fe (III) dimers in the solid state.
- ItemIntervalence electron transfer through a thiolate bridge ligand(2000) Díaz, C; Arancibia, AThe reaction of Cp(dppe)FeI with the ligands 2,2'- and 4,4'-dithiobispyridine (S-2(Py)(2)) give the mononuclear or binuclear complexes of the type [Cp(dppe)Fe-S-2(Py)(2)]PF6, [Cp(dppe)Fe-SPy]PF6 or [{Cp(dppe)Fe}(2)-mu -SPy](PF6)(2) depending on the reaction condition. Reaction of Cp(dppe)FeI with dithiobispyridines in presence of TIPF6 as halide abstractor and using CH2Cl2 as a solvent gives the complexes [Cp(dppe)Fe-4.4'-S-2(Py)(2))(2)]PF6 (1) and [CpFe(dppe)-2,2'-S-2(Py)(2)]PF6 (2) whereas the same reaction using CH3OH as a solvent and NH4PF6 as the halide abstractor leads to the formation of the Fe-III-thiolate complex [Cp(dppe)Fe-2,2'-SPy]PF6 (3) and the mixed-valence complex [Cp(dppe)Fe-III-mu SPy-Fe-II(dppe)Cp](PF6)(2) (4). Magnetic and ESR measurements are in agreement with one unpaired electron delocalized between them. Mossbauer data indicate clearly the presence of two different iron sites, each one of the N-bonded and S-bonded iron atoms, with intermediate oxidation state Fe-II-Fe-III. An electron transfer intervalence absorption was observed for this complex at 780 nm (in CH2Cl2). By applying the Hush theory the intervalence parameters were obtained; alpha = 0.028, H-ab = 361 cm(-1) which indicate Class II Robin-Day. Estimation of the rate electron transfer affords a value k(th) = 6.5 x 10(6) s(-1). Solvent effect on the intervalence transition follow the Hush prediction for high dielectric constants solvents which permit the evaluation of the outer and inner-sphere reorganizational parameters, which were analyzed and discussed. The electronic interaction parameters compare well with those found for electron transfer in metalloproteins. (C) 2000 Elsevier Science B.V. All rights reserved.
- ItemTCNE and TCNQ ligands as efficient bridges in mixed-valence complexes containing iron-cyclopentadienyl and other organometallic systems(2000) Diaz, C; Arancibia, AReaction between the pi-accepting tetracyanoeethene (TCNE) or tetracyano-p-quinodimethane (TCNQ) ligands and the rr-electron-rich organometallic species Cp(dppe)Fe+ results in the formation of the complexes [{Cp(dppe)Fe}(n){eta(n)-TCNX}](PF6)(n) (n = 1, 2 and 4). Infrared spectroscopy, magnetic moment measurements, electron-spin resonance (ESR) and cyclic voltammetry data indicate a net transfer of one rr electron to the TCNX acceptor ligand. The polynuclear complexes have an intense intervalence electron transfer absorption band in the near-infrared region. The values for the intervalence parameters alpha = 0.02-0.06 and V-ab = 200-600 cm(-1) indicate that these complexes can be classified as class II according to Robin-Day. Estimation of the rate of electron transfer affords values in the order of 10(8) s(-1), which are compared and discussed with values estimated for other polynuclear systems containing TCNE and TCNQ ligands as bridges. The solvent effect on the intervalence transition follows Hush's prediction for highly polar solvents, thereby permitting evaluation of the reorganizational energy. For the related series [{Cp(dppe)Fe}(n)-(mu-X)] (PF6)(n), the reorganization energy appears to depend mainly on the inner reorganization energy through changes to vibrational modes of the bridge. Reorganizational energy is not as important in determining the electron transfer rate as the activation energy, E-a. A linear relationship is found between the rate constant ln(k(et)) and the activation energy. These results can be discussed within the Marcus theory of electron transfer. The fast and efficient electron transfer between the metal fragments is discussed using molecular orbital arguments. (C) 2000 Elsevier Science Ltd All rights reserved.