The relaxation spectra of nickel(II) and cobalt(II) arginine complexes

✍ Scribed by G. Davies; K. Kustin; R. F. Pasternack

• Publisher: John Wiley and Sons
• Year: 1969
• Tongue: English
• Weight: 524 KB
• Volume: 1
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550010106

✦ Synopsis

The temperature-jump method has been used to determine the nickel(I1)-and cobalt(rr)arginine complexation kinetics. In the p H range studied, the neutral form of the ligand, HL, is the attacking, as well as the complexed, ligand species. T h e reactions reported on are of the type

where n = 1, 2, 3 and M is Ni or Co. At 25" and ionic strength 0.1M the association rate constants are: for nickel(I1) k, = 2.3 x lo3( *20%), k, = 2.4 x lo4( &2O%), k, = 3.5 x lo4( *40%) M-l sec-l;

for cobalt(r1) kl = 1.5 x lo5( *2O%), k, = 8.7 x 105(rt20%), k , = 2.0 x lO5( +40%) M-1 sec-'. Arginine binds to metal ions less well than homologous chelating agents due to the electrostatic repulsion arising from the positively charged terminus of the zwitterion. Kinetically, the effect appears in the association rate constants with nickel reactions more strongly influenced than cobalt.