Issue 22, 1976

Ring-size effects of macrocyclic ligands on complex stabilities. Mercury(II) complexes of twelve- to fifteen-membered cyclic tetra-amines

Abstract

A polarographic method has been used to study the equilibria of complex formation of mercury(II) ion with linear and 12–15-membered cyclic tetra-amines: 1,4,7,10-tetra-azacyclododecane(L1) 1,4,7,10-tetra-azacyclotride-cane(L2), 1,4,8,11-tetra-aracyclotetradecane(L3), and 1,4,8,12-tetra-azacyclopentadecane(L4). The stability constants are 1025.5, 1025.3, 1023.0, and 1023.7(at 25 °C. I= 0.20 mol dm–3) far the 1 : 1 complexes, respectively, indicating no special cavity selectivities. The constants are a little greater than those for related open-chain tetraamines(1024.5 for 3,6-diaraoctane-1,8-diamine and 1022.1 for 3,7-diazanonane-1,9-diamine). Ligand cyclizationin general causes mercury(II) complexes to undergo enthalpy loss which outweighs the normal compensation of the entropy terms, thus preventing an occurrence of the large macrocyclic effect seen for smaller metal ions. However, a unique macrocyclic ring-sire effect towards HgII occurs with the 14-membered ring, where the large negative enthalpy contribution outweighs the unfavourable entropy effect, a trend opposite to those in other macrocyclic systems.

Article information

Article type
Paper

J. Chem. Soc., Dalton Trans., 1976, 2335-2338

Ring-size effects of macrocyclic ligands on complex stabilities. Mercury(II) complexes of twelve- to fifteen-membered cyclic tetra-amines

M. Kodama and E. Kimura, J. Chem. Soc., Dalton Trans., 1976, 2335 DOI: 10.1039/DT9760002335

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Spotlight

Advertisements