LEAPS-MPS: Synthesis and Binding Thermodynamics of Three-fold Symmetric Organometallic Receptors for Inorganic Phosphates

Saint Mary'S College Of California, Moraga CA

Investigators

Abstract

In this project, funded by the MPS-LEAPS (Launching Early-Career Academic Pathways) Program and managed by the Broadening Participation Program in the Division of Chemistry (CHE-BP), Professor Wan-Yi Chu and her students at Saint Mary’s College of California will perform studies focused on the development of efficient receptors for aqueous inorganic phosphate anions. Phosphates are important fertilizer ingredients that are exhibiting a rapid decline in mineable reserves. Large amounts of phosphates are now accumulated in fresh water sources due to food consumption and agricultural runoffs. Extracting and recycling these phosphates from water is a challenging task due to its high hydration energy. Professor Chu and her students will develop a new family of organometallic receptors and evaluate their phosphate binding efficiency. The receptors are designed to overcome the large hydration energy of phosphates through metal-ligand cooperative interactions in a three-fold symmetric H-bond assembly. Their studies will contribute to the development of improved phosphate extraction technologies to ensure lasting food security. This work will be carried out by early college students and community college students, allowing them to gain research experiences in the lab and become better prepared for further professional development opportunities in the sciences. This work aims to elucidate the thermodynamic factors that influence metal-ligand cooperative binding of phosphates in organometallic complexes. The proposed complexes are designed to interact with phosphates through metal-ligand bonding with a metal center and H-bonds in the secondary coordination sphere. The H-bonds are assembled in a three-fold symmetric fashion to enhance the binding of tetrahedral phosphates through geometric recognition. Professor Chu and her students will first establish the syntheses of a series of structurally similar complexes that are promising as phosphate receptors. They will focus on metals with high Pearson’s hardness levels, such as Fe(III), Cu(II), and Zn(II). The ligand structures are systematically varied within the series to afford binding cavities that feature different sizes and rigidity. Professor Chu and her students will further measure the association equilibrium constants, enthalpies, and entropies of phosphate binding in these complexes. These thermodynamic values will be correlated with the structural variations in the organometallic series. These investigations of the relationships between receptor structure and phosphate binding efficiency will contribute to the establishment of a set of design criteria for selective organometallic phosphate receptors. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.