title: Aqueous NMR Signal Enhancement by Reversible Exchange in a Single Step Using Water-Soluble Catalysts.
abstract: Two synthetic strategies are investigated for the preparation of water-soluble iridium-based catalysts for NMR signal amplification by reversible exchange (SABRE). In one approach, PEGylation of a variantN-heterocyclic carbene provided a novel catalyst with excellent water solubility. However, while SABRE-active in ethanol solutions, the catalyst lost activity in >50% water. In a second approach, synthesis of a novel di-iridium complex precursor where the cyclooctadiene (COD) rings have been replaced by CODDA (1,2-dihydroxy-3,7-cyclooctadiene) leads to the creation of a catalyst [IrCl(CODDA)IMes] that can be dissolved and activated in water-enabling aqueous SABRE in a single step, without need for either an organic cosolvent or solvent removal followed by aqueous reconstitution. The potential utility of the CODDA catalyst for aqueous SABRE is demonstrated with the ∼(-)32-fold enhancement of1H signals of pyridine in water with only 1 atm of parahydrogen.
authors.affiliation: Department of Chemistry and Biochemistry, and Materials Technology Center, Southern Illinois University , Carbondale, Illinois 62901, United States.
authors.forename: Fan
authors.initials: F
authors.lastname: Shi
authors.affiliation: Department of Chemistry and Biochemistry, and Materials Technology Center, Southern Illinois University , Carbondale, Illinois 62901, United States.
authors.forename: Ping
authors.initials: P
authors.lastname: He
authors.affiliation: Department of Chemistry and Biochemistry, and Materials Technology Center, Southern Illinois University , Carbondale, Illinois 62901, United States.
authors.forename: Quinn A
authors.initials: QA
authors.lastname: Best
authors.affiliation: Department of Chemistry and Biochemistry, and Materials Technology Center, Southern Illinois University , Carbondale, Illinois 62901, United States.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Groome
authors.affiliation: Department of Radiology, Vanderbilt University Institute of Imaging Science , Nashville, Tennessee 37232, United States.
authors.forename: Milton L
authors.initials: ML
authors.lastname: Truong
authors.affiliation: Department of Radiology, Vanderbilt University Institute of Imaging Science , Nashville, Tennessee 37232, United States.
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Coffey
authors.affiliation: Department of Chemistry and Biochemistry, and Materials Technology Center, Southern Illinois University , Carbondale, Illinois 62901, United States.
authors.forename: Greg
authors.initials: G
authors.lastname: Zimay
authors.affiliation: Department of Radiology, Vanderbilt University Institute of Imaging Science , Nashville, Tennessee 37232, United States.
authors.forename: Roman V
authors.initials: RV
authors.lastname: Shchepin
authors.affiliation: Department of Radiology, Vanderbilt University Institute of Imaging Science , Nashville, Tennessee 37232, United States.
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Waddell
authors.affiliation: Department of Radiology, Vanderbilt University Institute of Imaging Science, Nashville, Tennessee 37232, United States; Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee 37235, United States; Vanderbilt-Ingram Cancer Center, Nashville, Tennessee 37232, United States; Russian Academy of Sciences, Leninskiy Prospekt 14, Moscow, 119991, Russia.
authors.forename: Eduard Y
authors.initials: EY
authors.lastname: Chekmenev
authors.affiliation: Department of Chemistry and Biochemistry, and Materials Technology Center, Southern Illinois University, Carbondale, Illinois 62901, United States; Department of Chemistry and Biochemistry, and Materials Technology Center, Southern Illinois University, Carbondale, Illinois 62901, United States.
authors.forename: Boyd M
authors.initials: BM
authors.lastname: Goodson