Cyclam (1,4,8,11-tetraazacyclotetradecane) with one methylphosphonate pendant arm: a new ligand for selective copper(ii) binding.
The new ligand, [(1,4,8,11-tetraazacyclotetradecan-1-yl)methyl]phosphonic acid (H(2)te1P, H(2)L), was synthesized and its complexing properties towards selected metal ions were studied potentiometrically. The ligand forms a very stable complex with copper(ii)(logbeta(CuL)= 27.34), with a high selectivity over binding of other metal ions (i.e. logbeta(ZnL)= 21.03). The crystal structures of the free ligand (in its protonated form with bromide as counter-ion) and two copper(ii) complexes (obtained by crystallization at various pH) were determined. The free ligand adopts the common conformation for such macrocycles with the protonated nitrogen atoms in the corners of a virtual rectangle. In the trans-Br,O-[Cu(Br)(Hte1P)].H(2)O species, the central metal ion is surrounded by four in plane nitrogen atoms, one oxygen atom of the pendant moiety in the apical position and a bromide anion positioned trans to the oxygen atom, forming a distorted octahedral coordination sphere. In the compound [Cu(H(2)te1P)][Cu(Hte1P)]Br(3).6H(2)O, obtained from a highly acidic solution, the bromide anions are placed further away from the copper(ii) ion and the coordination environment (N(4)O) is thus square-pyramidal. In both structures, the protons are associated with non-coordinated phosphonate oxygen atoms.
Füzerová
Silvia
S
Department of Inorganic Chemistry, Universita Karlova (Charles University), Hlavova 2030, Prague 2, 128 40, Czech Republic. petrh@natur.cuni.cz.
Kotek
Jan
J
Císarová
Ivana
I
Hermann
Petr
P
Binnemans
Koen
K
Lukes
Ivan
I