Zahl A, van Eldik R (2006)
Publication Type: Journal article, Original article
Publication year: 2006
Original Authors: Davis A., Fiedler D., Seeber G., Zahl A., Van Eldik R., Raymond K.
Publisher: American Chemical Society
Book Volume: 128
Pages Range: 1324-1333
Journal Issue: 4
DOI: 10.1021/ja056556+
Guest exchange in an ML supramolecular assembly was previously demonstrated to proceed through a nonrupture mechanism in which guests squeeze through apertures in the host structure and not through larger portals created by partial assembly dissociation. Focusing on the [Ga L] assembly {L = 1,5-bis(2′, 3′-dihydroxybenzamido)naphthalene}, the host-guest kinetic behavior of this supramolecular capsule is defined. Guest self-exchange rates at varied temperatures and pressures were measured to determine activation parameters, revealing negative ΔS‡ and positive ΔV‡ values {PEt: ΔH‡ = 74(3) kJ mol, ΔS‡ = -46(6) J mol K, k = 0.003 s; NEt: ΔH‡ = 69(2) kJ mol, ΔS‡ = -52(5) J mol K, k = 0.009 s; NMePr: ΔH‡ = 52(2) kJ mol, ΔS‡ = -56(7) J mol K, ΔV‡ = +13(1) cm mol, k = 4.4 s; NPr : ΔH‡ = 42(1) kJ mol, ΔS‡ = -102(4) J mol K, ΔV‡ = +31(2) cm mol, k = 1.4 s}. In PEt for NEt exchange reactions, egress of the initial guest (G1) is found to be rate determining, with increasing G1 and G2 (the displacing guest) concentrations inhibiting guest exchange. This inhibition is explained by the decreased flexibility of the host imparted by exterior, or exohedral, guest interactions by both the G1 and G2 guests. Blocking the exohedral host sites with high concentrations of the smaller NMe cation (a weak endohedral guest) enhances PEt for NEt guest exchange rates. Finally, guest displacement reactions also demonstrate the sensitivity of guest exchange to thermodynamic endohedral guest binding affinities. When the initial guest (G1) has a weaker affinity for the host, G2 concentration dependence is observed in addition to dependence on the G2 binding strength. © 2006 American Chemical Society.
APA:
Zahl, A., & van Eldik, R. (2006). Guest exchange dynamics in an M4L6 tetrahedral host. Journal of the American Chemical Society, 128(4), 1324-1333. https://doi.org/10.1021/ja056556+
MLA:
Zahl, Achim, and Rudi van Eldik. "Guest exchange dynamics in an M4L6 tetrahedral host." Journal of the American Chemical Society 128.4 (2006): 1324-1333.
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