Photochemical pump and NMR probe to monitor the formation and kinetics of hyperpolarized metal dihydrides

Abstract

Pulsed-laser experiments validate photochemical pump-NMR probe spectroscopy for monitoring the rate of rapid H2 oxidative addition to a metal centre.

Probing the Hydrogenation of Vinyl Sulfoxides Using para-Hydrogen

“…24,25 SABRE has been used to make low concentration species visible either in mixtures 26 or in chemical reactions. 27 Hence, SABRE has been used to track and gain mechanistic insight into chemical reactivity. 28…”

Towards measuring reactivity on micro-to-millisecond timescales with laser pump, NMR probe spectroscopy

“…[34][35][36][37] Due to the large excess of p-H 2 in solution, we treat the subsequent oxidative addition of p-H 2 to the unsaturated intermediate using a pseudo-rst-order kinetic model. Accordingly, we write down the following differential equation (eqn (11)) to describe the time-dependence of the concentration of the This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.…”

“…Laser-pump, NMR probe spectroscopy has also been used previously to measure the rate of reaction of IrI(CO)(PPh 3 ) 2 with p-H 2 to form Ir(H) 2-I(CO)(PPh 3 ) 2 . 11 The difference in chemical shi between the hydrides in Ir(H) 2-I(CO)(PPh 3 ) 2 is 3840 Hz (6.4 ppm) at 14 T and 295 K. By contrast, the rate of H 2 addition is on the order of 2-5 s À1 over the range of H 2 pressures studied. These rates correspond to a dephasing parameter of 3 $ 3 Â 10 5 degrees.…”

“…The photochemical pump, NMR probe experiment has been shown previously to be highly reproducible [9][10][11] and the use of p-H 2 hyperpolarisation provides high SNR values. Furthermore, while single-shot experiments are desirable, signal averaging could be used to boost SNR in the usual way, if necessary.…”

“…NMR ow methods, which access faster reaction timescales in a manner similar to ow UV, have also been demonstrated for applications such as rapid-injection protein unfolding [3][4][5][6][7] and metabolomics studies. 8 Recently, we demonstrated a new method for monitoring reactivity by NMR spectroscopy using a pump-probe approach, [9][10][11] which has also been implemented by Yurkovskaya and co-workers. 12 This method is analogous to that used with optical detection methods such as UV/vis, 13,14 IR 15 and Raman spectroscopy, [16][17][18] and shares many features with time-resolved EPR spectroscopy, which is used to probe photoexcited paramagnetic species at nanosecond and longer timescales.…”