Figure 3.

SABRE studies with the PEGylated Ir catalyst (7/14) in various deuterated ethanol/water mixtures. (a) Thermally polarized reference ¹H NMR scan from a D₂O/d₆-ethanol (∼13%/87% v/v) solution following activation; the spectrum is vertically scaled 5-fold compared to panel b, which shows the successful observation of SABRE enhancement of substrate (py) ¹H resonances after 1 min of bubbling with 5.1 atm of pH₂ at ∼11 mT, then transfer to 9.39 T for high-field acquisition; enhancements up to ∼40-fold were observed with 3.5 mM catalyst and the given conditions. Changing the D₂O/d₆-ethanol fraction to ∼43%/57% v/v (c and d) and 63%/37% v/v (inset) significantly impacted the magnitude of the SABRE enhancement; the SABRE spectrum in panel d showed less than an ∼10-fold enhancement compared to the corresponding thermal spectrum (c), and no observed SABRE enhancement was observed in the 63%/37% solution.