Cyclam copper complex

Figure 6-23. The greater stability of the macrocyclic complex means that when the copper(n) complex of an open-chain tetraamine ligand is reacted with cyclam, the copper(n) complex of cyclam is formed.

KEYWORDS Copper(II)-cyclam complex, XANES, DV-Xa method, electronic transition probability... 

Structures of l,4,8,ll-tetraazacyclotetradecanecopper(II) complexes ([Cu(cyclam)] ) with F", Cl, and Br" have been determined in crystals (1-3). The effect of solvents on the axial ligation constants of (C-meso- (C) and C-rac-5,5,7,12,12,14-hexamethyl-cyclam (L ) )copper(II) complexes with Cl and Br have been studied in water and in methanol, suggesting an interesting... 

In the present study, we synthesized dibromo(l,4,8,ll-tetraazacyclotetradecane)copper(II) ([CuBr2(cyclam)]) and diaqua(l,4,8,ll-tetraazacyclotetradecane)copper(II) difluoride four hydrate ([Cu(cyclam)-(H20)2]F2 4H20) complexes and performed single crystal structure analysis and X-ray absorption near-edge structure (XANES) measurements in crystals and in aqueous solution. Furthermore, DV-Xa molecular orbital calculations have been made for models based on these results, and the structures and electronic states of the [Cu(cyclam)] complexes in crystals and in aqueous solution are discussed, in particular, on the axial coordination to Cu(II). 

Formation kinetics for eight tetraaza macrocycles of the cyclam type reacting with copper(II) have been analyzed in terms of rate constants for reaction with [Cu(OH)3] and with [Cu(OH)4]2. There is a detailed discussion of mechanism and of specific steric effects (292). Complex formation from cyclam derivatives containing -NH2 groups on the ring -CH2CH2CH2- units proceeds by formation followed by kinetically-distinct isomerization. The dramatic reactivity decreases consequent on... 

The formation of Cu(cyclam) by reaction of cyclam with a large variety of copper complexes (CuL"+) is interesting ... 

The Ni(II) complex of the hexaaza macrocyclic ligand 1 is reported to show a high activity for the electrocatalytic reduction of C02 to CO when a rotating copper disc electrode is used (85). In addition, water-soluble Niu-azacyclam complexes, 3a-3g, where R = carboxamide or sulfonamide, either aliphatic or aromatic, are found to be active in the electrocatalytic reduction of C02 at a mercury cathode. The efficiency is comparable to that of [Ni(cyclam)]2+ (14). 

Scheme 5.2 Synthesis of tetra (hydroxy propyl) cyclam (5.21) via Michael addition followed by reduction, and X-ray crystal structure of its 1 1 copper(II) acetate complex.19...

Mixed aza-thiamacrocyclic derivatives of ferrocene 71 and 72 have also been prepared and the X-ray crystal structures of 72 and its copper complex reported [90]. Electrochemical studies revealed that the redox couples of 71 and 72 were perturbed to more positive potentials by 60 and 40 mV, respectively, on coordination with Cu ", even though the X-ray structure of the complex with 72 showed square planar coordination of the Cu " by the four sulfur atoms rather than by nitrogen. The cyclam ligand 73 derived from ferrocene has also been prepared and shown to recognise Ni and cations electrochemically [90]. 

Thus, the two tetramine receptors cyclam and tren were linked by a 1, 4-xylyl spacer to give system 14, tren-cyclam. The heterodimetallic complex [Cu(II)(tren)-Ni(II)(cyclam]4+ operates chloride anion translocation between copper and nickel centers, through the Ni(II)/Ni(III) couple, in an MeCN solution [36]. In particular, when 1 equivalent of CP is added to an MeCN solution of the heterodimetallic complex [with the nickel center in the Ni(II) state], the anion goes on the Cu(II) ion. In particular, since the log K value for the 1 1 adduct formation equilibrium is 5.7, in a lO-3 M solution of the heterodimetallic complex, 95% of the CP ion is bound to Cu(II), while the remaining 5% is dispersed in the solution. The solution has a blue-green color, due to an absorption band centered at 460 nm, pertinent to the [Cu(II)(tren]2+ fragment of the heterodimetallic complex [Cl-to-Cu(II) CT transition). If in an... 

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