NER: Immobilized Calixarenes as Nanomaterials for Selective Catalysis and Molecular Recognition

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This proposal was received in response to Nanoscience and Engineering initiative, NSF 03-043, category NER. This research addresses the design and synthesis of a new class of single-site materials for enantioselective adsorption and catalysis, which can be tailored on the nanoscale with an unprecedented level of detail. The materials consist of metallocalixarene structures grafted on the surface of silica. These grafted species have been recently shown to adsorb small organic molecules from vapor and liquid phases and to act as highly active and selective epoxidation catalysts. These properties include enantiospecific molecular recognition. The approach exploits recent advances in calixarene chemistry for upper rim functionalization, including the positioning of chiral functional groups to define an asymmetric pocket. For catalysis, recent success in epoxidation reactions will be extended by placing chiral groups in the immediate vicinity of and within dative bond contact (0.24 nm) of catalytically active centers, such as those in titano-calixarene structures. The materials synthesized in the course of the project should find broad use in the synthesis and separation of chiral molecules and in industrial applications within pharmaceutical, specialty monomer (for polymers and liquid crystal displays), and agrochemical sectors. These research activities broadly impact the training of scientists in emerging nanotechnology areas, with specific emphasis on the synthesis and structural characterization of materials with specific nanoscale connectivity and spatial arrangements. Graduate and undergraduate students will be trained in the design and synthesis of nanomaterials within a multi-disciplinary infrastructure, which includes expertise in synthetic chemistry of calixarenes and materials, their spectroscopic characterization, and the design of experimental apparatus for the assessment of adsorption and catalytic functions of grafted metallocalixarene materials. Research activities include an undergraduate laboratory component in which participation by women and minorities is actively sought.