Open AccessAqueous NMR Signal Enhancement by Reversible Exchange in a Single Step Using Water-Soluble Catalysts
Author(s) -
Fan Shi,
Ping He,
Quinn A. Best,
Kirsten A. Groome,
Milton L. Truong,
Aaron M. Coffey,
Greg Zimay,
Roman V. Shchepin,
Kevin W. Waddell,
Eduard Y. Chekmenev,
Boyd M. Goodson
Publication year - 2016
Publication title -
journal of physical chemistry. c./journal of physical chemistry. c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.401
H-Index - 289
eISSN - 1932-7455
pISSN - 1932-7447
DOI - 10.1021/acs.jpcc.6b04484
Subject(s) - catalysis , aqueous solution , chemistry , iridium , pyridine , solvent , cyclooctadiene , photochemistry , organic chemistry
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 variant N -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 In a second approach, synthesis of a novel di-iridium complex precursor where the cyclooctadiene (COD) rings have been replaced by CODDA (1,2-dihydroxy-3,7-cyclooctadiene) leads to the creation of a catalyst [IrCl(CODDA)IMes] that can be dissolved and activated in water-enabling aqueous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 of 1 H signals of pyridine in water with only 1 atm of parahydrogen.