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Complexation and DFT studies of lower rim hexahomotrioxacalix[3]arene derivatives bearing pyridyl groups with transition and heavy metal cations. Cone versus partial cone conformation
Author(s) -
Marcos Paula M.,
Teixeira Filipa A.,
Segurado Manuel A. P.,
Ascenso José R.,
Bernardino Raul J.,
Cragg Peter J.,
Michel Sylvia,
HubscherBruder Véronique,
ArnaudNeu Françoise
Publication year - 2013
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.3085
Subject(s) - chemistry , stability constants of complexes , acetonitrile , potentiometric titration , transition metal , dichloromethane , density functional theory , alkali metal , proton nmr , metal , inorganic chemistry , crystallography , computational chemistry , stereochemistry , solvent , organic chemistry , ion , aqueous solution , catalysis
The binding of representative alkali, alkaline earth, transition and heavy metal cations by 2‐pyridylmethoxy derivatives (1b, in cone and partial cone conformations) of p‐tert ‐butylhexahomotrioxacalix[3]arene was studied. Binding was assessed by extraction studies of the metal picrates from water into dichloromethane and by stability constant measurements in acetonitrile and methanol, using spectrophotometric and potentiometric techniques. Microcalorimetric studies of some selected complexes in acetonitrile were performed, as well as proton NMR titrations. Computational methods (density functional theory calculations) were also employed to complement the NMR data. The results are compared with those obtained with the dihomooxacalix[4]arene 2b and the calix[4]arene 3b derivative analogues. Partial cone‐1b is the best extractant for transition and heavy metal cations. Both conformers of 1b exhibit very high stability constants for soft and intermediate cations Pb 2+ , Cd 2+ , Hg 2+ , Zn 2+ and Ni 2+ , with cone‐1b the strongest binder (ML, log β ≥ 7) and partial cone‐1b the most selective. Both derivatives show a slight preference for Na + . Besides the formation of ML complexes, ML 2 and M 2 L species were also observed. The former complexes were, in general, formed with the transition and heavy metal cations, whereas the latter were obtained with Ag + and Hg 2+ and partial cone‐1b. In most cases, these species were corroborated by the proton NMR and density functional theory studies. Copyright © 2013 John Wiley & Sons, Ltd.