1277-43-6Relevant articles and documents
Birmingham et al.
, p. 96 (1955)
Cobaltocenium acetylsalicylate: synthesis and circular dichroism study of interactions with DNA
Snegur,Kaverin,Babievsky
, p. 1787 - 1790 (2019)
Cobaltocenium acetylsalicylate was synthesized and characterized for the first time. The concentration dependences observed in its interaction with the double helix of DNA have been studied by circular dichroism. In these spectra, changes in the positions and decrease in the intensities of the curves in the positive and negative regions are observed when adding in increasing concentrations of cobaltocenium acetylsalicylate to calf thymus DNA. The observed changes in the effects of Cotton were interpreted as local changes in the conformation of the DNA double helix caused by the interaction of positively charged metallocenium cations with phosphate DNA fragments.
Fast electron transfer across semiconductor-molecule interfaces: GaAs/Co(Cp)2+/0
Meier, Andreas,Selmarten, Donald C.,Siemoneit, Kerstin,Smith, Barton B.,Nozik, Arthur J.
, p. 2122 - 2141 (1999)
The kinetics of majority electron transfer in the dark from n-GaAs electrodes to cobaltocenium (Co(Cp)2+) acceptors in acetonitrile has been studied in detail, both experimentally and theoretically. The experimental results were obtained from electrochemical impedance spectroscopy, quartz crystal microbalance (QCM and EQCM) studies, and current-potential characteristics. The theoretical work involved calculating the adsorption energy and molecular configuration of the cobaltocenium acceptors at the GaAs surface using high level density functional theory (B3LYP and variations thereof) as well as semiempirical methods. The QCM experiments showed that both Co(Cp)2+ and Co(Cp)20 are physisorbed at GaAs surfaces, with adsorption energies of about 0.2 and 0.4 eV, respectively. The theoretical results are consistent with these experimental results. They indicate that adsorption of the Co(Cp)2+/0 redox system occurs on GaAs, with Co(Cp)20 somewhat more strongly adsorbed than Co(Cp)2+; the Co(Cp)2+/0 molecules were found to adsorb with the cyclopentadienyl rings parallel to the GaAs surface. A model for the overall electron-transfer process was developed that incorporates Co(Cp)2+ adsorption. Analysis of the detailed impedance spectra over the range of 1 Hz to 600 kHz showed that the sequential electron-transfer steps in the model (i.e., electron transfer from the GaAs conduction band to adsorbed Co(Cp)2+, followed by electron transfer from the adsorbed Co(Cp)20 to free Co(Cp)2+ in solution) are very fast and that the observed overall rate of electron transfer is limited by the rate of thermionic emission from the GaAs bulk region to the surface. The implications of these results for the theory of electron transfer at semiconductor-liquid interfaces, and the associated controversies surrounding theory and various experimental results for GaAs-metallocenium systems, are discussed.
The Orbital-Overlap Factor in Electron Transfer: Sensitivity of Homogeneous Self-Exchange Kinetics for Some Metallocenes to Electronic Structure
Nielson, Roger M.,Golovin, M. Neal,McManis, George E.,Weaver, Michael J.
, p. 1745 - 1749 (1988)
Rate constants, khex, for the electron self-exchange of cobaltocenium-cobaltocene, Cp2Co+/0, and for the decamethyl derivative, (Cp-Me5)2Co+/0, obtained by using the NMR line-broadening technique in acetonitrile and dimethyl sulfoxide are compared with corresponding data for the ferrocene couples Cp2Fe+/0 and (Cp-Me5)2Fe+/0 and for bis(benzene)chromium(I)/(0).The rate constants in a given solvent display a marked sensitivity to the reactant structure, the khex values being about tenfold larger for Cp2Co+/0 relative to Cp2Fe+/0; decamethyl substitution yields tenfold increases in khex for both these couples.A relationship is established between these ca. 100-fold rate variations and the nature of the donor and acceptor orbitals.In particular, the markedly slower self-exchange kinetics observed for Cp2Fe+/0 relative to Cp2Co+/0 are consistent with the much greater ligand-delocalized character of the 4elg orbital involved in the latter electron transfer as compared with the 4e2 or 8alg orbital for the former reaction.The same argument is likely to account for the similar relative rates for (Cp-Me5)2Fe+/0 versus (Cp-Me5)2Co+/0.These rate differences are very unlikely to be due to variations in nuclear reorganization factors since the molecular structures of these couples are virtually identical, and they feature only small differences (ca. 0.3 kcal mol-1) in the inner-shell barriers.The results therefore provide unusually clear evidence for the influence of donor-acceptor electronic coupling in outer-sphere redox reactivity.
FLASH-VACUUM PYROLYSIS OF η5-CYCLOPENTADIENYLDICARBONYLCOBALT. FORMATION OF COBALTOCENE
Fiaud, Jean-Claude,Chauvin, Remi,Bloch, Robert
, p. C32 - C34 (1986)
Flash-vacuum pyrolysis (350 deg C, 0.1 Torr) of cyclopentadienyldicarbonylcobalt afforded cobaltocene (85percent yield) at the end of the pyrolysis tube.This compound is formed in a bimolecular reaction in the hot zone of tube between species from which CO ligands have been lost.
Direct synthesis of an anionic 13-vertex closo-cobaltacarborane cluster
Maier, Thomas M.,Coburger, Peter,Van Leest, Nicolaas P.,Hey-Hawkins, Evamarie,Wolf, Robert
supporting information, p. 15772 - 15777 (2019/11/11)
Reaction of 1,2-bis(diphenylphosphino)-ortho-carborane (L) with [K(thf){(MesBIAN)Co(η4-cod)}] (1, MesBIAN = bis(mesityliminoace-naphthene)diimine, cod = 1,5-cyclooctadiene) affords an anionic 13-vertex closo-cobaltacarborane cluster (2) in one step. The mechanism of this transformation has been studied by experimental and quantum chemical techniques, which suggest that a series of outer-sphere electron transfer and isomerisation processes occurs. This work shows that low-valent metalate anions are promising reagents for the synthesis of anionic metallacarborane clusters.
Direct probing of photoinduced electron transfer in a self-assembled biomimetic [2Fe2S]-hydrogenase complex using ultrafast vibrational spectroscopy
Li, Ping,Amirjalayer, Saeed,Hartl, Frantisek,Lutz, Martin,Bruin, Bas De,Becker, Rene,Woutersen, Sander,Reek, Joost N. H.
, p. 5373 - 5383 (2014/06/09)
A pyridyl-functionalized diiron dithiolate complex, [μ-(4-pyCH 2-NMI-S2)Fe2(CO)6] (3, py = pyridine (ligand), NMI = naphthalene monoimide) was synthesized and fully characterized. In the presence of zinc tetraphenylporphyrin (ZnTPP), a self-assembled 3·ZnTPP complex was readily formed in CH2Cl2 by the coordination of the pyridyl nitrogen to the porphyrin zinc center. Ultrafast photoinduced electron transfer from excited ZnTPP to complex 3 in the supramolecular assembly was observed in real time by monitoring the (C≡O) and (C=O)NMI spectral changes with femtosecond time-resolved infrared (TRIR) spectroscopy. We have confirmed that photoinduced charge separation produced the monoreduced species by comparing the time-resolved IR spectra with the conventional IR spectra of 3?- generated by reversible electrochemical reduction. The lifetimes for the charge separation and charge recombination processes were found to be τCS = 40 ± 3 ps and τCR = 205 ± 14 ps, respectively. The charge recombination is much slower than that in an analogous covalent complex, demonstrating the potential of a supramolecular approach to extend the lifetime of the charge-separated state in photocatalytic complexes. The observed vibrational frequency shifts provide a very sensitive probe of the delocalization of the electron-spin density over the different parts of the Fe2S2 complex. The TR and spectro-electrochemical IR spectra, electron paramagnetic resonance spectra, and density functional theory calculations all show that the spin density in 3?- is delocalized over the diiron core and the NMI bridge. This delocalization explains why the complex exhibits low catalytic dihydrogen production even though it features a very efficient photoinduced electron transfer. The ultrafast porphyrin-to-NMI-S2-Fe2(CO)6 photoinduced electron transfer is the first reported example of a supramolecular Fe2S2-hydrogenase model studied by femtosecond TRIR spectroscopy. Our results show that TRIR spectroscopy is a powerful tool to investigate photoinduced electron transfer in potential dihydrogen-producing catalytic complexes, and that way to optimize their performance by rational approaches.
