A calorimetric study of ligand interactions with protons and metal ions in the 100 to 400 C range

R. M. Izatt, J. L. Oscarson, S. E. Gillespie, X. Chen, P. Wang, G. D. Watt
1995 Pure and Applied Chemistry  
The thermodynamic quantities (log K , AH, &Y, and ACp) associated with the interactions of protons and metal ions with ligands in aqueous solutions are strongly influenced by the structure and properties of water. These quantities, especially AS and AH, reflect the decrease in hydrogen bonding in water as temperature increases. The magnitude and the sign of AS and AH for proton interaction with amino acid and nucleotide anions are indicative of the interaction of charged species with water, the
more » ... ies with water, the number of water molecules replaced upon complexation, and intra-molecular interactions. The interaction of 18-crown-6 with Kf, Sr2+, and Ba2+ produces AS and AH values of opposite sign to those expected from other neutral molecule-cation interactions. This result probably derives from the ability of 18-crown-6 to form a hydrophobic barrier to water molecules attracted by the metal cation. The resulting build-up of water molecules causes a more ordered system and the observed anomalous AS and AH values.
doi:10.1351/pac199567040543 fatcat:rxtktk3oqndsnnqpturjppzgty