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Complexes of TRI‐ and tetraprotonated forms of 1,4,7,10,13‐pentaazacyclopentadecane with various mono‐ and divalent anions in aqueous media
Author(s) -
Gelb Robert I.,
Alper Joseph S.,
Schwartz Marietta H.
Publication year - 1992
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610050804
Subject(s) - chemistry , potentiometric titration , solvation , divalent , aqueous solution , inorganic chemistry , iodide , dissociation (chemistry) , enthalpy , hydrogen bond , acid dissociation constant , titration , dissociation constant , ion , organic chemistry , molecule , biochemistry , physics , receptor , quantum mechanics
Abstract Acid dissociation and anion complexation properties of 3+ and 4+ forms of 1,4,7,10,13‐pentaazacyclopentadecane were investigated by pH potentiometry, conductometric titration and 13 C NMR experiments. The 3+ and 4+ species form complexes with a variety of mono‐ and divalent anions, and their complexation constants can be determined by pH potentiometric methods. However, no iodide complexes are detected and neither is a pentaprotonated species. Enthalpy and entropy changes for the acid dissociation of the 3+ ligand and for its complexation with chloride are estimated. The complexation and acid dissociation properties of the ligand are discussed in terms of internal hydrogen bonding interactions and solvation effects.