Kinetics and mechanism of formation and decomposition of copper(II) complexes with a binucleating hexaazamacrocycle

Synthesis, Protonation and CuII Complexes of Two Novel Isomeric Pentaazacyclophane Ligands: Potentiometric, DFT, Kinetic and AMP Recognition Studies

“…Thus, the experimental observation of different kinetics of decomposition for three species with the same set of donor atoms would reveal that the complex does not reorganise rapidly to the most stable conformation of [ The comparison of the actual values of the kinetic parameters obtained in the present work with those previously reported for related complexes requires a previous consideration of the intimate mechanism of decomposition. The mechanism widely accepted in the literature [30][31][32] for the decomposition of polyamine complexes of Cu II assumes that the acid attack on the Cu-N bond that is broken in the rate-determining step does not occur directly because it requires the previous formation of an activated intermediate "Cu-N" with partial breaking of the Cu-N bond [Equation (3)]. The complete dissociation of the metal-ligand bond can be achieved through two parallel pathways that involve solvent or acid attacks on this intermediate [Equations (4) and (5)].…”

Equilibrium and Kinetic Properties of CuII Cyclophane Complexes: The Effect of Changes in the Macrocyclic Cavity Caused by Changes in the Substitution at the Aromatic Ring

“…In this way, it is found that the conversion of CuL to HCuL 3+ (CuL 2+ + H + p CuHL 3+ ; logK = 7.19 and 6.09 for m-B232 and p-B232, respectively) occurs with constants higher than those corresponding to the protonation of H 2 L 2+ to give H 3 L 3+ (log K = 5.92 and 5.81 for m-B232 and p-B232, respectively), which clearly indicates that the first protonation of the metal complex occurs at a noncoordinated amine group. Moreover, as the log K values for the formation of the Cu(m-B232) 2+ and Cu(p-B232) 2+ species are close to those found for related polyamines acting as tridentate ligands, [17,23] it is reasonable to conclude that m-B232 and p-B232 coordinate to the metal centre in CuL 2+ using the two central and one of the benzylic amine groups, the other benzylic nitrogen remaining uncoordinated.…”

“…The quotient bc/a corresponds to the k H /k H 2 O ratio and provides information about the relative rates of decomposition through the parallel attacks by H + and H 2 O. [23] Unfortunately, the absence of curvature in the plots in Figure 6 precludes the estimation of the lability of the Cu-N bonds through the resolution of values for b. In any case, the values of the product bc for both steps is less than an order of magnitude different from the value for the complex with the noncyclic 232 ligand (17.5 mol -1 dm 3 s -1 ), which suggests that coordination of only three of the four amine groups in the m-B232 complex leads to a kinetic behaviour that resembles that of the acyclic ligands, a situation very different from that found for o-B232.…”

Correlation between the molecular structure and the kinetics of decomposition of azamacrocyclic copper(ii) complexes

“…However, to avoid complications caused by the existence of mixtures of species in solution, it is convenient to carry out the measurements starting with solutions containing a single complex species. 19 By using this strategy, it has been previously found that these studies not only provide information about the acid-promoted decomposition of the complex but also they can even reveal the existence of structural reorganizations. In the case of L1, the species distribution curves (Fig.…”