Copper-macrocycle complex square planar

The results obtained by cyclic voltammetry clearly show that upon oxidation or reduction of the central metal copper, the macrocycle is set in motion. Upon oxidation of 6(4)+, the resulting tetrahedrally coordinated Cu(II) is unstable as Cu(II) forms stable square planar complexes or higher coordination (five or six). Therefore, the macrocycle pirouettes around the axle permitting the restoration of a stable coordination, that is pentacoordination by the 2,2, 6 2"-terpyridine and 2, 2 -bipyridine... 

In the case of the purely aliphatic ligand 2,2,6,6-tetrakis(amino-methyl)-4-azaheptane (12), complex formation with copper appears to proceed in two steps, as elucidated by titration experiments with the fully protonated ligand (12 5 HC1). Three and two protons from (Hr,12) + are sequentially abstracted, and the predominant species after full deprotonation appears to be a dinuclear complex in which two copper(II) ions are coordinated, each in square planar fashion, by the l,3-diaminoprop-2-yl units of two molecules of pentaamine ligand, thus forming a macrocyclic complex of composition [Cu2(12)2]4+ (23). The UV/vis spectral data show an interesting solvent dependence, suggesting an equilibrium between [Cu2(12)2]4 + and two equivalents of mononuclear complex [Cu(12)]2+ under suitable conditions. ESR spectroscopic data are also compatible with the formulation of a dinuclear species. Further addition of base to an aqueous solution of [Cu2(12)2]4+ gives the mononuclear hydroxo complex [(12)Cu(OH)]+, as inferred from the UV/vis spectroscopic data. 

X-Ray Absorption Near Edge Structure Study and DV-Xa Calculations on Some Square-planar Copper(II) Complexes with Macrocyclic Ligands... 

The theoretical analysis of XANES by DV-Xa method has also been reported to be very useful for the structural investigation as well as study of chemical state and chemical bonding for the square-planar tetraaza and diazadioxa macrocyclic copper(II) complexes. ... 

Thus, in examples of synthesis of tetraazamacrocyclic compounds on nickel ions (mainly) and on copper(II), square-planar system assembling is realised [38,47-49]. Guanidium ion promotes building of 27-crown-9-ether [60]. o-Aminobenzaldehyde self-condensation on the copper ion as matrix results exclusively in forming a complex with TAAB [67]. When using nickel(II) or cobalt(II) as templates under the same conditions, two types of macrocyclic azomethine systems - TAAB and TRI - may be synthesised [67-71]. Macrocychsation of phthalonitrile on the anisotropic matrix 0=U=0 ends with obtaining the so-called superphthalocyanine product [U02(L29)] [72, 73], rather than with the isolation of the corresponding complex with the phthalocyanine (Pc), as observed for other metal ions (Eq. 1.18) [11,74]. 

Square planar nickel(II), cobalt(II), copper(II), palladium(II) and platinum(II) macrocyclic dioximates result from replacement of the hydrogen bonds in oxime complexes with boron bridging reagents (Eqs. 4.27 and 4.28) [98-109]. 

In a review of copper, silver and gold complexes [76], complex 64 (Figure 6.2) was the most active species, giving a 77C of 170% at a dose range of 6.25—12.5 mg/kg in B16 melanoma, (compare cisplatin with a mean TIC of 180% at a dose range of 0.15—20 mg/kg). Complex 64 is inactive in other screens, however [76]. The result is of interest because the macrocycle stabilizes the cuprous oxidation state, possibly because of extensive delocalization inducing a distorted square-planar condfiguration [76]. 

Properties of a relatively water-stable copper(iii) complex with a macrocyclic ligand have been reported. The ligand has four strong amide donors and is confined to a square-planar geometry. A p/fa at about pH 5 is attributed to deprotonation of an axially bound water molecule. 

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