Thermodynamic, spectroscopic, and structural studies of complexation of phenol- and pyridine-armed macrocyclic ligands with univalent metal ions
- Brigham Young Univ., Provo, UT (United States); and others
Log K, {Delta}H, and {Delta}S values for interactions of a series of pyridinoazacrown ethers each bearing a phenol arm (2-6) and two macrocycles each bearing a pyridine arm (7, 8) with Na{sup +}, K{sup +}, Tl{sup +}, and Ag{sup +} have been determined in absolute methanol at 25{degrees}C by calorimetric titration. In each case, the complex stability has the sequence Na{sup +} < K {sup +} < Tl{sup +} {much_lt} Ag{sup +}. The phenol-armed macrocycles exhibit selectivity of more than 4 orders of magnitude for Ag{sup +} over Na{sup +}, K{sup +}, and Tl{sup +}. Attachment of a pendant phenol arm having various substituents to parent macrocycle 1 increases the binding abilities of the resulting ligands. Substituents on the para position of the phenol arm have an appreciable effect on cation-binding constants. Good Hammett correlations are found by plotting log K values vs {sigma}{sub p} for interactions of five phenol-armed macrocyclic ligands (2-6) with Na{sup +}, K{sup +}, and Tl{sup +}. The complexation has been characterized by means of {sup 1}H NMR and UV-visible spectroscopic, and X-ray crystallographic methods. The study indicates that the phenol OH group of 2-6 is capable of forming an intramolecular hydrogen bond with the macroring nitrogen atom and that the complexation in absolute methanol generally does not deprotonate these phenols. In the crystal structure of the Na{sup +} -3 complex, the Na{sup +} is coordinated to all seven of the donor atoms of the ligand and two Na{sup +} -3 complexes join together to form a dimer. The dimer contains an intermolecular hydrogen bond formed between the phenol hydrogen atom of one ligand and the phenolate group of a centrosymmetrically related ligand and two {pi}-{pi} stacking interactions between the electron-deficient pyridine ring of one molecule and the electron-rich phenol ring of the other. 36 refs., 5 figs., 6 tabs.
- DOE Contract Number:
- FG02-86ER13463
- OSTI ID:
- 563604
- Journal Information:
- Inorganic Chemistry, Vol. 36, Issue 12; Other Information: PBD: 4 Jun 1997
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SODIUM
CHEMICAL BONDS
BOND ANGLE
BOND LENGTHS
ETHERS
SYNTHESIS
LIGANDS
STABILITY
STRUCTURAL CHEMICAL ANALYSIS
CRYSTAL STRUCTURE
THERMODYNAMIC PROPERTIES
MOLECULAR STRUCTURE
ATOMS
COMPLEXES
CRYSTALLOGRAPHY
NMR SPECTRA
HYDROGEN
METHANOL
NITROGEN
PHENOLS
PYRIDINE
TITRATION
ULTRAVIOLET SPECTROMETERS
DIMERS
METALS
IONS
ULTRAVIOLET SPECTRA