Kinetics of complex formation and stability constants of tetra-(2-hydroxpropyl) substituted cyclam (L-3) and cyclen (L-4) with copper(II) have been studied in aqueous solution at room temperature. These data are compared to the corresponding parent compounds (cyclam L-1 and cyclen L-2) in an attempt to define the effect of pendant arm upon kinetics and stability constants of the complexes. The kinetics were observed by stopped-flow measurements followed at multiwavelengths. These ligands were chosen to furnish information concerning effect of pendant groups and cavity size on the kinetics and stability of the complexes. Stopped-flow and spectrophotometric titration techniques were used for evaluation of the kinetics and stability constants, respectively. The apparent rate constants increase as CuL3 > CuL4 > CuL1 > CuL2. Activation parameters and stability constants of the complexes were estimated. The effect of cavity size on the rate of reaction can be observed in CuL3 > CuL4 and CuL1 > CuL2 and the effect of pendant groups in CuL3 > CuL1 and CuL4 > CuL2. Mechanism of the complex formation reaction is proposed. The enhanced stability of the copper(II) complexes formed with L-1 and L-2 macrocyclic ligands is compared to those formed with analogous pendant arm species.
Kinetics of complex formation and stability constants of tetra-(2-hydroxpropyl) substituted cyclam (L3) and cyclen (L4) with copper(II) have been studied in aqueous solution at room temperature. These data are compared to the corresponding parent compounds (cyclam L1 and cyclen L2) in an attempt to define the effect of pendant arm upon kinetics and stability constants of the complexes. The kinetics were observed by stopped-flow measurements followed at multiwavelengths. These ligands were chosen to furnish information concerning effect of pendant groups and cavity size on the kinetics and stability of the complexes. Stopped-flow and spectrophotometric titration techniques were used for evaluation of the kinetics and stability constants, respectively. The apparent rate constants increase as CuL3?>?CuL4?>?CuL1?>?CuL2. Activation parameters and stability constants of the complexes were estimated. The effect of cavity size on the rate of reaction can be observed in CuL3?>?CuL4 and CuL1?>?CuL2 and the effect of pendant groups in CuL3?>?CuL1 and CuL4?>?CuL2. Mechanism of the complex formation reaction is proposed. The enhanced stability of the copper(II) complexes formed with L1 and L2 macrocyclic ligands is compared to those formed with analogous pendant arm species
