T. Pauwels, W. Lippens, P. Smet
Feb 12, 1999
Citations
0
Influential Citations
25
Citations
Journal
Polyhedron
Abstract
Abstract The hexaaza macrocyclic ligand 3,6,9,17,20,23-hexaazatricyclo[23.3.1.111,15]triaconta-1(29),11(30),12,14,25,27-hexaene (L), which forms strong dinuclear Cu(II) complexes, can act as a host for several anionic guests. The guests under investigation are the amino acids alanine, valine, leucine, norleucine, norvaline and serine. The host–guest interactions were investigated by conventional potentiometric pH-metry, by spectrophotometric titrations in 2:1:1 molar ratio for Cu(II), L and guest and by IR spectroscopy. In aqueous solution three ternary species are formed as a result of coordinate bonding, Coulombic attraction and hydrogen bond formation between the host and guest. The stability constants as well as the calculated equilibrium constants for the species are reported. It was found that the norleucine anion has the largest affinity for the dinuclear Cu(II) complex. The large inductive effect and the linear structure of its side chain is suggested to be responsible.