Ion-Bearing Propellers: Alkali Metal Complexes of Tris(2-alkoxyphenyl)amine Ionophores

Scott J. Stoudt, Prakash Gopalan, Alexei Bakulin, Bart Kahr, James E. Jackson

Research output: Contribution to journalArticlepeer-review

Abstract

NMR spectroscopic studies reveal that binding of Na+ by tris(2-methoxyphenyl)amine (3) brings two of these tripod ethers together about the metal ion; the related double-tripod-ether ionophore 1,2-bis[2-(bis(2-methoxyphenyl)amino)phenoxy]ethane (4), in which two triarylamines are covalently attached, binds LiI, LiBPh4, NaI, NaBPh4, and KB(4-ClPh)4. Dynamic NMR puts lower limits on binding free energies of 4 for Na+ (71.8 kJ mol-1) and K+ (66.8 kJ mol-1) ions. X-ray studies of 32·NaBPh4, 4·NaBPh4, 4·NaB(4-ClPh)4, and 4·KB(4-ClPh)4·CH3NO2 show eight-coordinate M+ ions bound between crystallographically independent, homochiral triarylamine tripod ethers in structures reminiscent of alkali metal [2.2.2] cryptates. Complexes crystallize as follows: 32·NaBPh4, monoclinic, P21/c, Z = 4, a = 10.701(3) Å, b = 37.593(3) Å, c = 13.774(2) Å, and β= 98.24(2)°; 4·NaBPh4, triclinic, P1̄, Z = 2, a = 12.157(1) Å, b = 14.811(1) Å, c = 15.860(2) Å, α = 105.400(8)°, β = 91.594(9)°, and γ = 95.354(8)°; 4·NaB(4-ClPh)4, monoclinic, P21/n, Z = 4, a = 13.652(5) Å, b = 18.75(1) Å, c = 22.805(5) Å, and β = 92.21(5)°; 4·KB(4-ClPh)4·CH3NO2, monoclinic, Pn, Z = 2, a = 13.663(4) Å, b = 12.228(3) Å, c = 18.712(8) Å, and β= 91.45(3)°. They show variable N-M-N angles; 32·NaBPh4 is surprisingly bent (ZN-Na-N = 154.5°), while the 4·M+ complexes are normal: nearly linear for Na+ (ZN-Na-N = 178.6, 178.1°) and again bent with the larger K+ (ZN-K-N = 164.5°). Finally, free 4 is structurally similar to 3; it crystallizes in the triclinic space group P1̄, with Z = 2, a = 8.068(1) Å, b = 14.599(2) Å, c = 16.475(3) Å, α = 115.43(1)°, β= 92.51(1)°, and γ = 90.40(1)°.

Original languageEnglish (US)
Pages (from-to)6614-6621
Number of pages8
JournalInorganic Chemistry
Volume35
Issue number22
DOIs
StatePublished - 1996

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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