The acid dissociation
kinetics of the mono-copper complexes of 1,4,7-triazacyclononane, znn; 1,4,7-triazacyclodecane, zdn;
1,4,8-triazacycloundecane, zud;
1,5,9-triazacyclododecane, zdd;
2,2,4-trimethyl-1,5,9-triazacyclododecane, tmzdd;
1,5,9-triazacyclotridecane, ztd; and cyclohexane-
r-1,c-3,c-5 triamine, ccha,
were studied in aqueous solution over a range of acid concentrations (0.025-0.5
mol dm-3), I 1.0 (NaN03). A variety of
kinetic behaviour is observed. Cu(znn)2+,
Cu(zdn)2+ and Cu(zud)2+
display a first-order dependence upon [H+] with kH (298 K) 51 dm3
mol-1 s-1 (znn), 17 dm3
mol-1 s-1 (zdn), and 5.6 dm3
mol-1 s-1 (zud). Cu(zdd)2+, Cu(ztd)2+
and Cu(ccha)2+ show a dependence on [H+]
at low acid concentrations but become acid-independent at high concentrations.
The acid-independent rate constants are k1 (298 K) 2.2 s-1
(zdd), 15.4 s-1 (ztd)
and k1 (283 K) 75 s-1 (ccha).
Cu(tmzdd)2+ shows a rate law of the form
rate = k+kH[H+] with
k (298 K) 1.8×10 s-1 and kH
(298 K) 2.0×10-3 dm3 mol-1 s-1.
Activation parameters have been determined in all cases except Cu(ccha)2+ which was studied at 10�C. The results
are compared with other macrocyclic complex systems,
and a general mechanism for these reactions is discussed.
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