Zn(II)–D-(−)penicillamine complexes in aqueous solution. Zn-67 nuclear magnetic resonance study

D–(−)-Penicillamine interactions with Zn(II) have been studied in aqueous solutions as a function of pH, penicillamine concentration, and temperature, using Zn-67 nuclear magnetic resonance. Longitudinal and transverse relaxation rate measurements show the presence in solution of complexes in fast exchange with the aquated Zn(II) cation, and belonging to the extreme narrowing regime. Using equilibrium constant values from the literature, the relaxation behaviour was modelled. Characteristic Zn-67 line width values for the two complexes Zn(Pen) (v = (6200 ± 500) Hz) and [Zn(Pen H)]+ (v = (6000 ± 1000) Hz) were found. Equality of the two values is in agreement with zinc chelation by the sulfhydryl and the amino groups.