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Thermodynamic, Spectroscopic, and Structural Studies of Complexation of Phenol-and Pyridine-Armed Macrocyclic Ligands with Univalent Metal Ions

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Thermodynamic, Spectroscopic, and Structural Studies of Complexation of Phenol- and Pyridine-Armed Macrocyclic Ligands with Univalent Metal Ions

Zhang, Xian Xin and Bordunov, Andrei V. and Kou, Xiaolan and Dalley, N. Kent and Izatt, Reed M. and Mangum, John H. and Li, Du and Bradshaw, Jerald S. and Hellier, Paul C. (1997) Thermodynamic, Spectroscopic, and Structural Studies of Complexation of Phenol- and Pyridine-Armed Macrocyclic Ligands with Univalent Metal Ions. Inorganic Chemistry, 36 (12). pp. 2586-2593. ISSN 0020-1669.

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Abstract

Log K, ΔH, and ΔS 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^+, K^+, Tl^+, and Ag^+ have been determined in absolute methanol at 25 °C by calorimetric titration. In each case, the complex stability has the sequence Na^+ < K^+ < Tl^+ ≪ Ag^+. The phenol-armed macrocycles exhibit selectivity of more than 4 orders of magnitude for Ag^+ over Na^+, K^+, and Tl^+. 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 σ_p for interactions of five phenol-armed macrocyclic ligands (2−6) with Na^+, K^+, and Tl^+. The complexation has been characterized by means of ^1H NMR and UV−visible spectroscopic, and X-ray crystallographic methods. The crystal data for Na^+−3:  formula, [Na(C_(23)H_(28.5)N_3O_5)](ClO_4)_(0.5); space group, P^1̄; a = 9.400(9) Å, b = 11.467(10) Å, c = 12.281(11) Å, α = 77.22(7)°, β = 87.73(7)°, γ = 86.39(7)°, V = 1288(2) Å^3, and Z = 2. 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^+−3 complex, the Na^+ is coordinated to all seven of the donor atoms of the ligand and two Na^+−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 π−π stacking interactions between the electron-deficient pyridine ring of one molecule and the electron-rich phenol ring of the other.

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https://dx.doi.org/10.1021/ic961263q

DOI Article

https://pubs.acs.org/doi/suppl/10.1021/ic961263q

Publisher Supporting Information
Additional Information: © 1997 American Chemical Society.

Received October 16, 1996.

The authors thank the Department of Energy, Office of Basic Energy Sciences for financial support through Grant DE-FG02−86ER-13463. We appreciate valuable discussions with Dr. Alexander Y. Nazarenko concerning measurement of protonation constants.

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Funding Agency Grant Number
Department of Energy (DOE) DE-FG02-86ER-13463
Issue or Number: 12
Record Number: CaltechAUTHORS:20180529-111546971
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https://resolver.caltech.edu/CaltechAUTHORS:20180529-111546971

Official Citation: Thermodynamic, Spectroscopic, and Structural Studies of Complexation of Phenol- and Pyridine-Armed Macrocyclic Ligands with Univalent Metal Ions
Xian Xin Zhang, Andrei V. Bordunov, Xiaolan Kou, N. Kent Dalley, Reed M. Izatt, John H. Mangum, Du Li, Jerald S. Bradshaw, and Paul C. Hellier
Inorganic Chemistry 1997 36 (12), 2586-2593
DOI: 10.1021/ic961263q
Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code: 86664
Collection: CaltechAUTHORS
Deposited By: George Porter
Deposited On: 29 May 2018 19:35
Last Modified: 03 Oct 2019 19:46

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