Flexible Pores of a Metal Oxide-Based Capsule Permit Entry of Comparatively Larger Organic Guests

详细信息    查看全文

• 作者：Ayala Ziv ; Alina Grego ; Sivil Kopilevich ; Leila Zeiri ; Pere Miro ; Carles Bo ; Achim Mller ; Ira A. Weinstock
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：May 13, 2009
• 年：2009
• 卷：131
• 期：18
• 页码：6380-6382
• 全文大小：165K
• 年卷期：v.131,no.18(May 13, 2009)
• ISSN：1520-5126

文摘

In zeolites and other rigid solid-state oxides, substrates whose sizes exceed the pore dimensions of the material are rigorously excluded. Now, using a porous 3 nm diameter capsule-like oxomolybdate complex [{Mo^VI₆O₂₁(H₂O)₆}₁₂{(Mo^V₂O₄)₃₀(OAc)₂₁(H₂O)₁₈}]³³⁻ as a water-soluble analogue of solid-state oxides (e.g., as a soluble analogue of 3 Å molecular sieves), we show that carboxylates (RCO₂⁻) can negotiate passage through flexible Mo₉O₉ pores in the surface of the capsule and that the rates follow the general trend R = 1° 2° > 3° phenyl (no reaction). Surprisingly, the branched alkanes (R = iso-Pr and tert-Bu) enter the capsule even though they are larger than the crystallographic dimensions of the Mo₉O₉ pores. Four independent lines of spectroscopic and kinetic evidence demonstrate that these organic guests enter the interior of the capsule through its Mo₉O₉ apertures and that no irreversible changes in the metal oxide framework are involved. This unexpected phenomenon likely reflects the greater flexibility of molecular versus solid-state structures and represents a sharp departure from traditional models for diffusion through porous solid-state (rigid) oxides.