Electrochemical and spectroscopic studies on copper(II) complexes of macrocyclic ligands as models for square-pyramidal metal active sites of copper(II) complexes of bleomycin and glutathione

A New Diazacyclooctane Dihydroxamate as a Siderophore Analogue − Synthesis and Equilibrium Studies of Iron(III) and Copper(II) Complexes

“…The quite low protonation constant of the second nitrogen atom of DACODMAHA (log K 4 ϭ 2.22) supports the existence of such a strong hydrogen bond network, namely between the ammonium proton and the amine N atom (ϾN ϩ -H···NϽ) as well as between the deprotonated amine nitrogen atom and the adjacent hydroxamic proton (ϾN···HOϪ). The remaining protonation constants (log K 2 ϭ 8.91, log K 3 ϭ 7.45) agree with the expected values for hydroxamate groups (log K ϭ 8Ϫ10), [20] although their values are slightly lowered by inductive/electrostatic effects of the α-amino/ammonium groups.…”

XAS, ESR and Potentiometric Studies of Three DinuclearN,N′‐para‐Xylylenebis(tetraazamacrocycle)copper(II) Complexes − X‐ray Crystal Structure of [N,N′‐p‐Xylylenebis(cyclen)]copper(II)

“…The obtained spectroscopic parameters g || and A || are very close to those of complexes formed with cyclam or cyclen [19] [b] Ref. [19] ( Table 2).…”

“…The obtained spectroscopic parameters g || and A || are very close to those of complexes formed with cyclam or cyclen [19] [b] Ref. [19] ( Table 2). For ratios R smaller than 1, the obtained ESR spectra each show a signal with seven equidistant lines, characteristic of the formation of dinuclear species.…”

“…The four nitrogen atoms of the macrocycle form the base of each pyramid, whereas a water molecule occupies the fifth position. [19] For the complex formed with paracyclam, the position of the band (λ ϭ 528 nm) is similar to those in complexes formed with different ligands derived from cyclam (512 nm Ͻ λ Ͻ 550 nm). [19,21] This value is typical of the squareplanar CuN 4 chromophore with a strong ligand field.…”

Spectroscopy and Redox Behaviour of Dicopper(II) and Dinickel(II) Complexes of Bis(cyclen) and Bis(cyclam) Ligands

“…[12] The lack of absorption at about 650 nm [13] ) the UV/Visible spectra are indicative of octahedral coordination for the nickel in solution, solvent molecules occupying the free positions of the octahedron (chromophore NiN 4 S 2 ). [14] Two bands are observed for both complexes in water and in acetonitrile corresponding to the predicted 3 A 2g Ǟ 3 T 2g (950-800 nm) and 3 A 2g Ǟ 3 T 1g (F) (560-500 nm) transitions for a d 8 metal ion under octahedral symmetry, the third transition 3 A 2g Ǟ 3 T 1g (P) (300-400 nm) being hidden by the stronger absorbance of the ligand (λ Ͻ 300 nm).…”