Structural reinforcement of a large macrocyclic ligand. A structural, molecular mechanics, and thermodynamic study
- 1 January 1990
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 2,p. 483-488
- https://doi.org/10.1039/dt9900000483
Abstract
The complex of the macrocycles L5(1,10-dioxa-4,7,13,16-tetra-azacyclo-octadecane), L6(4,13-dioxa-1,7,10,16-tetra-azabicyclo[14.2.2] eicosane) and L7(4,13-dioxa-1,7,10,16-tetra-aza-tricyclo[14.2.2.27,10]docosane) have been synthesized and their complex formation constants determined with Cu2+, Ni2+, Zn2+, Cd2+, and Pb2+; the ions Sr2+ and Ba2+ were found not to complex with the ligands. The successive insertion of ethylene bridges into the 1,4-diaminoethane units in L5 enhances the selectivity of the ligand for large metal ions, with L7 binding only to Pb2+. The selectivity of these ligands and the depression of the formation constants with all metal ions upon successive insertion of the ethylene bridges are rationalised with the aid of molecular mechanics calculations. The crystal structure of the free ligand of L7 has been determined: space group P21/n, monoclinic, with a= 6.053(2), b= 14.190(8), c= 10.346(6)Å and β= 106.82(4)°, and Z= 2. The final conventional R factor was 0.0627.This publication has 0 references indexed in Scilit: