Progress in the synthesis and characterization of a covalently assembled resorcin[4]arene based molecular heterocapsule is reported.  In 2006, our group published a covalently assembled capsule with temperature-dependent conformational flexibility.  Guest encapsulation was not observed in this capsule, likely due to the flexibility of its tetraquinoxaline-like base.  Thus, we hypothesize that rigidification of the capsular design will promote guest encapsulation.  We propose rigidification of the capsule’s base through the replacement of a two-carbon bridge to a one-carbon bridge in one of the adjacent hydroxyls in the resorcin[4]arene framework.  Previous attempts to synthesize our rigidified capsule were met with difficulty.  We predict that templation will facilitate the synthesis of our capsule by driving its formation because of favorable interactions with the template molecule that stabilizes the capsule.  Our capsule will be synthesized from two different resorcin[4]arene cavitands, a diquinoxaline monomethylene-bridged cavitand and a monoquinoxaline dimethylene-bridged cavitand, linked by a tetraazaanthracene bridge.  Capsule precursors were characterized by proton nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry.  We expect the rigidified capsule to maintain some flexibility to reversibly open and close in response to changes in temperature or pH in order to allow the control of capture and release of guest molecules.  Studies on the physical properties of our capsule will provide information that will give us insight on how to control the capsule’s guest selectivity.

Synthesis and characterization of a covalently assembled molecular capsule for guest encapsulation

249th National Meeting (2015)

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