Nickel macrocyclic complexes properties

Although the electrochemistry and the electrocatalytic properties of nickel macrocyclic complexes, phthalocyanines and porphyrins have been well studied in various solvents, few data exist on their special and typical behaviour when electropolymerized films in aqueous alkaline solution. During the last decade, it has been shown that nickel tetraazamacrocyclic complexes (examples shown in Figure 8.20) can be easily deposited onto an electrode surface in alkaline solutions... 

Electric fleld gradient, 22 214-218 Electroabsorption spectroscopy, 41 279 class II mixed-valence complexes, 41 289, 291, 294-297 [j(jl-pyz)]=+, 41 294, 296 Electrocatalytic reduction, nickel(n) macro-cyclic complexes, 44 119-121 Electrochemical interconversions, heteronuclear gold cluster compounds, 39 338-339 Electrochemical oxidation, of iron triazenide complexes, 30 21 Electrochemical properties fullerene adducts, 44 19-21, 33-34 nickeljll) macrocyclic complexes, 44 112-113... 

Macrocyclic complexes (continued) nickel(II), 44 93-94 eatalysis, 44 119-125 configurational isomerization, 44 126 electrochemical properties, 44 112-113 electronic absorption spectra, 44 108-112 reactions, 44 118-119 square-planar and octahedral species, 44 116-118... 

Many new Ni(II) complexes of aza-type macrocycles have been synthesized, and their redox chemistries have been explored. In particular, complexes of macropolycyclic ligands and bismacrocyclic ligands have been prepared. Complexes with uncommon oxidation states of nickel (Nim and Ni1 complexes) have also been synthesized by employing a specially designed macrocycle, and their characteristic spectroscopic properties and X-ray structures reported. These nickel(II) complexes... 

Properties of nickel(II) complexes with unsaturated macrocycles 241... 

A summary of nickel(H) complexes formed by representative saturated polyaza macrocycles is reported in Table 103, together with a concise description of the synthetic procedures and some of their physicochemical properties. Most studies are concerned with nickel(II) complexes with tetraaza macrocycles, but examples of complexes with triaza and pentaaza macrocycles are not rare. 

The properties of nickel(II) complexes with unsaturated macrocycles which contain pyridyl groups are included in a very comprehensive review article.2626 The complexes are usually square planar with the exceptions of the trans octahedral NiX2(CR)2743 (CR = 2,12-dimethyl-3,7,ll,17-tetraazabicyclo[11.3.1]heptadeca-l(17),2,ll,13,l5-pentaene) and of the diamagnetic square pyramidal NiBr(CR)]Br-H20 (381).2747 The diamagnetic complexes Ni(CR)(C104)2 give rise to square planar octahedral equilibria in coordinating solvents,2744,2746 whereas... 

An extensive study of the redox properties of tetraaza macrocyclic complexes of nickel has been performed by Busch and co-workers.3056,3133,3134 Electrochemical data for selected Nim/Nin couples are reported in Table 117. From an analysis of the EPR spectra it has been found that acetonitrile, as well as other molecules or ions like Cl and S04, can coordinate in axial position to give six-coordinate complexes.3056,3141 The g values are indicative of a dj... 

The electrocatalytic activity of various nickel macrocycles in aqueous solution was studied. Cyclic voltammograms indicate that 7 / S -NiHTIM2+, NiMTC2+ and NiDMC + are better catalysts than Ni(cyclam)2+ in terms of more positive potentials and/or their larger catalytic currents [26], Bulk electrolyses with 0.5 mM Ni complexes confirm that these complexes are excellent catalysts for the selective and efficient CO2 reduction to CO. The macrocycles with equatorial substituents showed increased catalytic activity over those with axial substituents. These structural factors may be important in determining their electrode adsorption and CO2 binding properties. 

An extensive study of the redox properties of tetraaza macrocyclic complexes of nickel has been performed by Busch and co-workers. Electrochemical data for selected... 

In terms of its chemical properties, the isolated cofactor F43o resembles other nickel (II) complexes of tetraamine macrocycles with respect to redox and the binding of axial ligands. Me-Ni and RSNi derivatives of these macrocyclic complexes represent possible model intermediates for the C-S bond scission process [134]. 

Nickel(II) ion and complexes are often included in the study of the catalytic properties of metal ions (Chap. 6). Nickel(II) (and copper(II)) have a marked ability to promote ionization from coordinated amide and peptide likages (Sec. 6.3.2). Nickel(II) can also help assemble reactants in a specific fashion to produce macrocycles. 

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