Jason B. English, A. Martell, R. Motekaitis
May 30, 1997
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Influential Citations
78
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Journal
Inorganica Chimica Acta
Abstract
Abstract The unsymmetrical hexabasic macrocyclic ligand 1,13-dioxa-4,7,10,16,20,24-hexaazacyclohexacosane ([26]aneN 6 O 2 , OBISDIPEN) forms an assortment of cationic species including mono- through hexaprotonated forms of ther macrocyclic ligand in the absence of metal ions as well as mononuclear and dinuclear Cu(II) complexes. These mononuclear and dinuclear Cu(II) complexes also form protonated and hydroxylated species. The cationic hosts combine with certain molecules and anions (guests) which have the requisite size, shape and donor groups. A bidentate guest molecule or anion can bridge the two metal ions and coordinate them simultaneously. This paper describes the reactions of OBISDIPEN and of its six mononuclear and four dinuclear Cu(II) complexes with the pyrophosphate bridging group to form complexes which exist in a variety of protonated conformations. The binding in these complexes consists of coulombic forces, hydrogen bonds and coordinate metal-donor bonds. The equilibrium constants were obtained by potentiometric titration at 25.0 ± 0.1°C and μ = 0.1 M KCl. These constants are compared to those of the analogous ligand 4,7,10,16,19,22-hexaaza-1,13-dioxacyclotetracosane (OBISDIEN).