ISSN:
0018-019X
Schlagwort(e):
Chemistry
;
Organic Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
The protonation and deprotonation rates of the coordinated amide groups in the Cu2+-complexes of 1,8-diamino-3,6-diaza-2,7-octanedione (DED = L) have been studied by stopped-flow techniques. Starting at low pH from Cu2+ and DED the dimeric Cu2L24+-complex, fully formed within the mixing time of the stopped-flow instrument, reacts in two consecutive steps to yield the final product CuLH-2. The rate constants of the forward and backward reactions have been determined and are given in Table 1. The intermediate was identified as Cu2L2H-22+ by measuring its VIS.-absorption spectrum.The rate constants for the interconversion of the amide groups from the O- to the N-coordinated form in the Cu2+-complexes of DED, 2,10-dioxo-1, 4, 8, 11 tetraazaundecane (DANA) and triglycine (TRIGLY) are compared with each other. It is shown that these rate constants are similar, no matter whether the amide group is terminal or internal as long as the rotation is easily possible as is the case in the dimeric species Cu2L24+ and Cu2L2H-22+. However, for CuLH-2 the inter-conversion only takes place after opening of one of the chelate rings in a rapid protonation preequilibrium.
Zusätzliches Material:
5 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/hlca.19820650313
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