Comparative formation constants for metal ions with macrocycles based on 1,4,8,11-tetraazacyclotetradecane and carrying diamine, dicarboxylate or amine-carboxylate pendants
Y Baran, GA Lawrance, EN Wilkes
article (Uluslararası, Hakemli) | Yazar(lar): Y Baran, GA Lawrance, EN Wilkes | Yıl: 1997 | Dergi/Kurum: POLYHEDRON | İndeks: WOS.SCI | Anahtar Kelimeler: macrocycles, metal complexes, formation constants — Özet: Acid dissociation constants for the newly isolated dihydrogen anti-1,4,8,11-tetraazacyclotetradecane-6,13-d
Acid dissociation constants for the newly isolated dihydrogen anti-1,4,8,11-tetraazacyclotetradecane-6,13-dicarboxylate (diacmac), as well as for hydrogen anti-6-methyl-1,4,8,11-tetraazacyclotetradecane-6-amine-13-carboxylate (acammac) and anti-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine (diammac) are reported. The ligands differ somewhat in their selection of metal ions, which is reflected in the formation constants for complexation (log K-ML, 25 degrees C) which have been determined for the d(10) metal ions Zn2+ (diammac, 14.9; acammac, 14.7; diacmac, 26.3), Cd2+ (diammac, 10.6; acammac, 16.7; diacmac, 15.9), Hg2+ (diammac, 10.5; acammac, 17.3; diacmac, 21.8) and Pb2+ (diammac, 10.8; acammac, 10.7; diacmac, 19.0); and the d(5) Mn2+ ion (diammac, 6.2; acammac, 12.0; diacmac, 18.3). Differences arise in part from the increasing availability of potential O donors versus N donors in stepping from diammac to diacmac, and imply a clear role for the pendants in binding metal ions. Copyright (C) 1996 Elsevier Science Ltd