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Cavitand-based molecular hosts: hemicarceplexes, double carceplexes and large carceplexes

University of British Columbia

This thesis discusses the synthesis and study of molecular hosts derived from cavitand molecules, and is divided into two parts. Part I of this thesis presents a study of template effects on the formation of hemicarceplex 25»guest from triol cavitand 24. Competition experiments using various guest molecules revealed that the driving forces for the formation of hemicarceplex 25 are the same as those for the formation of previously studied carceplex 23 from tetrol cavitand 22. Part II of the thesis describes the design, synthesis and study of larger closed surface molecular hosts derived from cavitands. A survey of the literature revealed very few examples of molecular receptors having both closed surfaces and large cavities. Chapter 4 outlines the various strategies used in the attempted synthesis of a large "super-carceplex" and the synthesis of several new compounds such as cyclic trimer 135, and cyclic tetramer 136 are described. The final chapter of Part II discusses the uses of cyclic trimer 135 and cyclic tetramer 136 for the creation of novel hosts. Bis-carceplex 137»2pyrazines, a dumbell-shaped molecule comprised of two covalently linked carceplexes, was synthesized from cyclic tetramer 136 in 74% yield and the dynamics of this host molecules (137) were studied via variable temperature ] H NMR spectroscopy and MM2 calculations. The structurally related bis-complex 138#2guests was also formed from cyclic tetramer 138, and guest binding studies of the bis-complex (138) are presented. Cyclic trimer 135 was used to create trimer-carceplex 143#3DMF in 36% yield, demonstrating the unprecedented incarceration of three guest molecules within a carceplex. Variable temperature NMR and FT-IR spectroscopy measurements on trimer-carceplex 143»3DMF revealed unique properties of the incarcerated DMF guests as compared to the bulk DMF solvent, and MM2 calculations suggested a preferred orientation of the guest molecules within the capsule. [Abstract includes diagram]

Thesis/Dissertation

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2009-04-03

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http://hdl.handle.net/2429/6782

Chemistry

University of British Columbia

UBCV

DSpace