AI Article Synopsis
- Hyperpolarization using ParaHydrogen Induced Polarization (PHIP) has gained traction but few experiments on symmetric molecules were done recently, focusing on an AA'BB' system.
- Calculations show that interactions between triplet and singlet proton states lead to hyperpolarization during PHIP experiments, particularly when parahydrogen protons are in specific sites.
- The study demonstrates how the hydrogenation of acetylene dicarboxylic acid dimethylester illustrates these principles, explaining signal enhancements under certain magnetic conditions, and this methodology can be applied to other AA'BB' molecule types.
Article Abstract
Hyperpolarization by means of ParaHydrogen Induced Polarization (PHIP) has found increasing applications since its discovery. However, in the last decade only a few experiments have been reported describing the hydrogenation of symmetric molecules. A general AA'BB' system is studied here. Calculations of the spin dynamics with the density matrix formalism support the experimental findings, providing profound understanding of the experiments in Cs-symmetric molecules. Level anti-crossings between states related to the triplet and the singlet state of one pair of the protons are identified as being responsible for hyperpolarization transfer in a PHIP experiment, when the former p-H(2) protons occupy the sites AA'. The hydrogenation of acetylene dicarboxylic acid dimethylester with parahydrogen is used to illustrate the case. The theoretical treatment applied to this particular reaction explains the signal enhancements in both groups of protons in the spectrum when the sample is placed in the proper magnetic field strength, including the phase inversion of the signal of the methyl group. The treatment described here can be extended to every molecule which can be approximated as an AA'BB' system.
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| http://dx.doi.org/10.1016/j.jmr.2012.03.020 | DOI Listing |
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