Extension of the ⪡model⪢ approach to the study of coordination chemistry of vit. B12 group compounds

Bigotto, Adriano; Costa, G.; Mestroni, G.; Pellizer, Giorgio; Puxeddu, A.; Reisenhofer, E.; Stefani, Laura; Tauzher, G.

doi:10.1016/0073-8085(70)80011-0

Cited by 127 publications

(57 citation statements)

References 36 publications

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“…1. The fit is reasonably satisfrictory, suggesting that the process observed is indeed The experimentally observed and calculated syminetrical collapse of the triplet is consistent with [2] being rate-determining, as unsymmetrical collapse would be expected if [3] were not rapid. The 1: 1 and 2: 1 species would probably exhibit difTerent methyl chemical shifts, and collapse would be expected to a position intermediate to these two values if significant amounts of the 1 : 1 complex existed in solution.…”

Section: Proto11 N~iclem Mrrgtzetic Reso~icr~zce Sl~ectrcisupporting

confidence: 56%

Tertiary phosphine complexes of the cobalt(III) NN′-ethylenebis(salicylideneiminato) and bisdimethylglyoximato systems

Smith¹,

Loon²,

Baird³

1976

Can. J. Chem.

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Complexes of the types [CosalenPR3]X, [Cosalen(PR3)2]X, [Co(DH)2PPh3X], and [Co(DH)2(PR3)2]ClO4, many of them new, have been prepared and characterized with respect to 1H nmr spectra, ligand field parameters, and equilibrium constants for the formation of the 2:1 salen complexes. 1H chemical shifts appear to be dominated by anisotropic rather than inductive effects, while the relative tertiary phosphine ligand field strengths appear to correlate with the steric requirements of the phosphines as well as their expected σ donor strengths. Ease of formation of the 2:1 salen complexes is determined largely by steric effects, as are trans effects in the DH systems.

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Section: Proto11 N~iclem Mrrgtzetic Reso~icr~zce Sl~ectrcisupporting

confidence: 56%

Tertiary phosphine complexes of the cobalt(III) NN′-ethylenebis(salicylideneiminato) and bisdimethylglyoximato systems

Smith¹,

Loon²,

Baird³

1976

Can. J. Chem.

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“…Cobalt complexes of tetradentate Schiff-base ligands have been investigated as mimics of vitamin B 12 coenzymes and certain Co III Schiff-base complexes are known to have antiviral, antibacterial, and antitumor properties (15,16). The Schiff-base ligands coordinate to Co II or Co III ions through two amine nitrogen atoms and two phenolic oxygen atoms.…”

Section: Resultsmentioning

confidence: 99%

Cellular Up-regulation of Nedd4 Family Interacting Protein 1 (Ndfip1) using Low Levels of Bioactive Cobalt Complexes

Schieber

Howitt

Putz

et al. 2011

Journal of Biological Chemistry

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The delivery of metal ions using cell membrane-permeable metal complexes represents a method for activating cellular pathways. Here, we report the synthesis and characterization of new [ Transition metals are essential for many important chemical processes in biological systems. Most of these metal-related processes occur by interactions with nucleic acids and proteins. Within the cell, metal ions can stabilize, destabilize, or modulate DNA and proteins by introducing conformational changes and by creating centers of activity. Although the use of metals as structural elements within the cell is well known, emerging evidence now recasts metals as signaling molecules able to activate critical cellular pathways. For example, metals such as iron, copper, and cobalt can produce reactive oxygen species that lead to the activation of redox-sensitive transcription factors including NF-B, AP-1, and p53. Metals have also been suggested to affect the upstream regulatory components of the MAP kinase and the PI3K/Akt/mTor pathway (1, 2). Thus the levels and regulation of metals in a cell can have a direct role on cell function and survival.Metal ions such as Co II and Fe II can stimulate the expression of the neuroprotective protein Nedd4 family interacting protein 1 (Ndfip1) 4 in the brain (3). Ndfip1 is a transmembrane protein that is localized to the Golgi and post-Golgi vesicles such as endosomes (4, 5). Ndfip1 functions as an adaptor protein for the Nedd4 family of ubiquitin ligases that target proteins for both degradation and trafficking (4). The metal-induced up-regulation of Ndfip1 results in the activation of the ubiquitin proteasome pathway. Ndfip1 recognizes and interacts with divalent metal transporter 1 (DMT1), this recruits the E3 ligase Nedd4 -2 resulting in degradation of DMT1, preventing iron overload within the cell (3). Other targets for Ndfip1 have also been identified, including the transcription factor JunB that is regulated by Ndfip1 in association with the E3 ligase Itch (6). In the adult brain, Ndfip1 is endogenously present in cortical neurons at low levels, however it is up-regulated in a subset of neurons upon activation by injury or stress (7). Importantly, this up-regulation of Ndfip1 has been shown to be neuroprotective, and neurons with up-regulated Ndfip1 do not undergo apoptosis.Whereas high levels of exogenous Co II and Fe II are toxic to cells, our previous results show they also stimulate Ndfip1 via still unknown mechanisms. Barring the effects of metal toxicity, this finding introduces an opportunity to harness the capacity of metal ions to up-regulate Ndfip1 for neuroprotective purposes. In the present study, we investigate the utility of nontoxic metal complexes for controlled intracellular delivery of cobalt to stimulate Ndfip1 expression. This was based on the premise that the reactivity of metal ions can be modulated by the formation of coordination complexes, with a complexed 4 The abbreviations used are: Ndfip1, Nedd4 family interacting protein 1; DMT1, divalent metal transporte...

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“…The hexacoordinate complexes derived from acacen and mesalen have octahedral configurations and, as observed in several studies [6], exhibit a marked tendency to pentacoordination. Considering the relatively low temperatures at which the hexacoordinate complexes derived from the acacen and mesalen ligands begin to lose the axial base, it may be said that in effect these complexes are easily converted into pentacoordinate ones which show an appreciable stability Moreover, by observing the temperatures at which decompositions begin, one can see that the stability of the cobalt-axial base bond for both types of complexes decreases in the following order:…”

Section: Discussionmentioning

confidence: 81%

Thermal analysis of pentafluorophenyl organo complexes of cobalt(III) with Schiff bases

Royo

Sancho

1977

Journal of Thermal Analysis

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A series of complexes of the type (C6Fs)CoL4B with tetradentate ligands (L4 = acacen (N,N'-ethylene-bis acetylacetoneiminate dianion), mesalen (N,N'-ethylene-bis-7, 7'-dimethylsalicylideneiminate dianion); B -= H~O, NHs,py,ba, pip,3 monoanion), B = = Br, I, CN) has been studied, using TG and DTA methods to obtain information concerning the decomposition mechanism and the influence of the ligands on the thermal stabilities of cobalt-carbon and cobalt-axial base bond.The elimination of the axial base leads to the formation of pentacoordinate complexes (C6Fs)CoL 4 (when L 4 = acacen, mesalen) and their subsequent decomposition involves cobalt-carbon bond rupture to form COL4. In contrast, the latter reaction occurs first when the tetradentate ligand is dotnH.It has been observed that the stability of the cobalt-carbon bond is related to the nature of the equatorial ligands, and decreases in the order: mesalen > acaceni> dotnH.Many organometallic complexes of cobalt(III) with Schiff bases have been described, and numerous data concerning their preparation, structure and chemical behaviour are known [1,2].However, the thermal behaviour of this type of complex is almost unknown, because systematic~thermal analysis has not been carried out and only qualitative observations have been described.As regards the several organic substituents used, the 7r-acceptor capacity or the higher electronegativity of the group C6F5 leads to stabilization of the metal-carbon bond and the complexes containing this substituent can be more easily studied.Following our work on organometallic complexes of the perfluoro organic group C6F5, we have recently described [3 -5] complexes of the type (C6F~)CoL4B, La being the tetradentate acacen and mesalen dianions or the dotnH monoanion, and B a Lewis base. These complexes are all octahedral, with the tetradentate ligand occupying the four equatorial positions and the base B and the C~F 5 group situated in the two trans axial positions. They are particularly appropriate for the study of simple processes such as the breaking of the cobalt-carbon and the cobaltaxial base bonds, as the intermediate products are sufficiently stable to be observed.

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Extension of the ⪡model⪢ approach to the study of coordination chemistry of vit. B12 group compounds

Cited by 127 publications

References 36 publications

Tertiary phosphine complexes of the cobalt(III) NN′-ethylenebis(salicylideneiminato) and bisdimethylglyoximato systems

Tertiary phosphine complexes of the cobalt(III) NN′-ethylenebis(salicylideneiminato) and bisdimethylglyoximato systems

Cellular Up-regulation of Nedd4 Family Interacting Protein 1 (Ndfip1) using Low Levels of Bioactive Cobalt Complexes

Thermal analysis of pentafluorophenyl organo complexes of cobalt(III) with Schiff bases

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