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Metal Complexes with Macrocyclic Ligands, VI . The role of substituents on the complexation rate of transition metal ions with several 1,4,7,10‐tetraazacyclotridecanes
Author(s) -
Steinmann Willi,
Kaden Thomas A.
Publication year - 1975
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19750580514
Subject(s) - chemistry , octahedron , metal , ligand (biochemistry) , transition metal , crystallography , metal ions in aqueous solution , nitrogen , ion , stereochemistry , oxygen , absorption (acoustics) , absorption spectroscopy , copper , medicinal chemistry , inorganic chemistry , crystal structure , organic chemistry , catalysis , quantum mechanics , acoustics , biochemistry , receptor , physics
12,12‐Dimethyl‐1,4,7,10‐tetraazacyclotridecane (I), 11,13‐dimethyl‐1,4,7,10‐tetraazacyclotridecane (II), 11,11,13‐trimethyl‐1,4,7,10‐tetraazacyclotridecane (III) and 1,4,7,10,12,12‐hexamethyl‐1,4,7,10‐tetraazacyclotridecane (IV) have been synthesized and their properties are described. While the Ni 2+ and Cu 2+ complexes of I–III have square planar geometries, those of IV are pentacoordinate according to their absorption spectra. Similarly, while the Co 2+ complex of I is octahedral and readily oxygenated, the analogous complex with IV is pentacoordinate and not sensitive to oxygen. The rate of complexation of these ligands with Cu 2+ and Ni 2+ decreases in the order I > II > III ≫ IV, indicating that the number as well as the position of the methyl groups are important. Finally for Cu 2+ the formation of the thermodynamic stable end product is slown down by methyl substitution in α‐position to the coordinating nitrogen atoms (ligand II and III) so that an intermediate can be observed, whereas with I Cu 2+ directly forms the end product.