Chemical speciation of copper(II) diaminediamide derivative of pentacycloundecane—a potential anti-inflammatory agent

Formation constants of copper(II), zinc(II) and calcium(II) with 3,5-diaminodiamido-4-oxahexacyclododecane (cageL) has been studied by glass electrode potentiometry at 25 °C and an ionic strength of 0.15 mol dm⁻³. Copper(II) forms more stable complexes with cageL than zinc(II) and calcium(II). Metal ion complexation promotes deprotonation and coordination of the amide nitrogens resulting in overall tetragonal coordination of Cu²⁺ suggested by the UV-visible electronic spectra. Speciation calculations using a blood plasma model suggest that zinc(II) and calcium(II) are good competitors of copper(II) in vivo. Bio-distribution experiments using ⁶⁴Cu-labelled Cu(II)-cageL show that about 50% dose of the complex is retained in the body after 24 h.