Friday, February 17, 2017

Using signal amplification by reversible exchange (SABRE) to hyperpolarise 119Sn and 29Si NMR nuclei


Olaru, A.M., et al., Using signal amplification by reversible exchange (SABRE) to hyperpolarise 119Sn and 29Si NMR nuclei. Chem Commun (Camb), 2016. 52(100): p. 14482-14485.


The hyperpolarisation of the 119Sn and 29Si nuclei in 5-(tributylstannyl)pyrimidine (ASn) and 5-(trimethylsilyl)pyrimidine (BSi) is achieved through their reaction with [IrCl(COD)(IMes)] (1a) or [IrCl(COD)(SIMes)] (1b) and parahydrogen via the SABRE process. 1a exhibits superior activity in both cases. The two inequivalent pyrimidine proton environments of ASn readily yielded signal enhancements totalling approximately 2300-fold in its 1H NMR spectrum at a field strength of 9.4 T, with the corresponding 119Sn signal being 700 times stronger than normal. In contrast, BSi produced analogous 1H signal gains of approximately 2400-fold and a 29Si signal that could be detected with a signal to noise ratio of 200 in a single scan. These sensitivity improvements allow NMR detection within seconds using micromole amounts of substrate and illustrate the analytical potential of this approach for high-sensitivity screening. Furthermore, after extended reaction times, a series of novel iridium trimers of general form [Ir(H)2Cl(NHC)(mu-pyrimidine-kappaN:kappaN')]3 precipitate from these solutions whose identity was confirmed crystallographically for BSi.