ISSN:
1572-901X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The acidity of the free base (H2–P(X)) forms of the tetra- (N-methyl-4–(3 or 2)pyridyl)porphyrins were studied in basic solutions at 25 C, I=0.50. Equilibrium constants for both the H2– P(X)=P(X)2−+2H+ and the Li++ P(X)2−=Li- P(X)− reactions are reported. Log (KS) values for the Mn++P(4)2−=M- P(4)(n−2) reactions are 2.6 for Li+, 17.6 for Cd2+, 17.8 for Pb2+, 19.6 for (OH)2Hg, 25.9 for Zn2+ and 19.6 for the formation of Hg2–P(4)2+. Zn(OH)3− shows similar kinetic reactivity with both H2–P(4) and P(4)2− to form Zn- P(4) and HO-Zn- P(4)−,whileZn(OH)42− is unreactive with either species. For Zn2+, Zn(OH)+ and Zn(OH)3− with H2–P(4) the relative kinetic order for this tetrapositive macrocycle was ca. 1:300:20,000, while the trend Zn(OH)+〉Zn2+〉Zn(OH)3− is the usual pattern for peripherally negatively charged porphyrins.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1006959607483
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