New dinuclear cobalt(II) octaaza macrocyclic complexes with high oxidation redox potentials: Their crystal structure and unusual magnetic properties

Narayanan, Jayanthi; Peralta, Alejandro; Ugalde‐Saldívar, Víctor M.; Escudero, R.; Höpfl, Herbert; Sosa‐Torres, Martha E.

doi:10.1016/j.ica.2008.01.049

Cited by 24 publications

(25 citation statements)

References 39 publications

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“…By increasing the cobalt chloride content from 15 to 20 %, the magnetization of the CoCl 2 -filled polyimide film increased from 2.1 × 10 −2 to 5.1 × 10 −2 emu g −1 . These results confirm the weak ferromagnetic coupling between the Co 2+ ions at room temperature [32,33].…”

Section: The Magnetic Response Of Cobalt Chloride-filled Polyimide Filmssupporting

confidence: 81%

Insights into the physico-chemical behavior of CoCl2/polyimide hybrid materials

2016

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Hybrid fluorinated polyimide materials have been obtained by incorporation of various quantities of cobalt(II) chloride (CoCl 2 ) into polyimide matrix. Polycondensation reaction of equimolar amounts of 4,4′-diamino-3′3′-dimethyldiphenylmethane and 2,2′-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride has been carried out to produce in the first stage a polyamidic acid solution in which CoCl 2 × 6H 2 O has been placed. Further thermal treatment of this system led to the corresponding imide structure filled with the halide salt. An exhaustive study was directed to the influence of Co 2+ ions on the modified polyimide behavior as a function of its surroundings. To survey the functional properties of as-obtained Co 2+ -containing polyimide systems, several techniques such as FTIR, UV-vis and broadband dielectric spectroscopy, differential scanning calorimetry, and thermogravimetric and scanning electron microscopy were employed. A special concern was directed to the study of the optical properties induced by the addition of CoCl 2 into polymer solutions and films. The magnetic response of the polyimide was investigated in correlation with the salt quantity embedded in the PI film. The variation of the real and imaginary parts of the hybrid films' dielectric permittivity was registered in a broad frequency and temperature range, from 10 to 10 6 Hz and from −130 to 230°C, respectively.

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Section: The Magnetic Response Of Cobalt Chloride-filled Polyimide Filmssupporting

confidence: 81%

Insights into the physico-chemical behavior of CoCl2/polyimide hybrid materials

2016

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“…[13] The literature contains numerous other pyridyl pendant armed tetraazamacrocycles, indicating a general interest in the community and known synthetic techniques for adding pendant pyridyl donors. [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24]…”

Section: Introductionmentioning

confidence: 99%

Synthesis and structural studies of two pyridine-armed reinforced cyclen chelators and their transition metal complexes

et al. 2016

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Two novel pyridine pendant-armed macrocycles structurally reinforced by an ethyl bridge, either between adjacent nitrogens (for side-bridged) or non-adjacent nitrogens (for cross-bridged), have been synthesized and complexed with a range of transition metal ions (Co2+, Ni2+, Cu2+ and Zn2+). X-ray crystal structures of selected cross-bridged complexes were obtained which showed the characteristic cis-V configuration with potential labile cis binding sites. The complexes have been characterized by their electronic spectra and magnetic moments, which show the expected high spin divalent metal complex in most cases. Exceptions are the nickel side-bridged complex, which shows a mixture of high-spin and low spin, and the cobalt cross-bridged complex which has oxidized to cobalt(III). Cyclic voltammetry in acetonitrile was carried out to assess the potential future use of these complexes in oxidation catalysis. Selected complexes offer significant catalytic potential enhanced by the addition of the pyridyl arm to a reinforced cyclen backbone.

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“…Tpmc is a macrocyclic ligand well known for its ability to form stable complexes with transition metals in lower oxidation states, e.g., copper (II), cobalt (II) and nickel (II), among others. [6][7][8][9][10] In these binuclear complexes, the metal ion remained exocoordinated from the macrocycle, where tpmc can adopt either a chair or a boat conformation depending on the metal ion and the nature (mono or polydentate) of a secondary ligand bound to the metal centers. 6,7 Figure 1 shows the tetraazamacrocycle tpmc and its conformational structures adopted in binuclear compounds.…”

Section: Introductionmentioning

confidence: 99%

“…[6][7][8][9][10] In these binuclear complexes, the metal ion remained exocoordinated from the macrocycle, where tpmc can adopt either a chair or a boat conformation depending on the metal ion and the nature (mono or polydentate) of a secondary ligand bound to the metal centers. 6,7 Figure 1 shows the tetraazamacrocycle tpmc and its conformational structures adopted in binuclear compounds. Like other tetraazamacrocyclic ligands, tpmc coordinates each metal ion by the two cyclam ring nitrogens and by two donor atoms of the pendant groups, leaving one of the axial positions open for a secondary ligand, while the other position is sterically blocked by the pendant groups.…”

Section: Introductionmentioning

confidence: 99%