The complexing of indium(III) by cysteine

The complex formation of the cysteine-In(III) system has been investigated by potentiometric titration and by PMR, IR, and UV spectroscopic measurements. The InL, InL2, and InLH species are predominantly formed at the metal concentration from 0.00025 to 0.0005 M. At higher concentrations of the metal ion (0.0025-0.005 M), however, the InL species is negligible and the InL2, InL3, InL(LH), and In(LH)2 species are predominant. The formation constants calculated with a non-linear, least-squares program were log β110=14.12, log β120=27.26, log β130=32.20, log βsub(11-1)=18.46, log βsub(12-1)=31.78, and log βsub(12-2)=35.74 for InL, InL2, InL3, InLH, InL(LH), and In(LH)2 respectively. The IR and UV spectra revealed that the amino group of the coordinating cysteine was protonated. The [In3L4(OH)(H2O)] complex was isolated. (auth.)