NMR and parity nonconservation. Experimental requirements to observe a difference between enantiomer signals

Abstract

The possibility of observing a difference in the high-resolution NMR spectra of two enantiomers as due to parity nonconservation is discussed. Proposals to minimize the NMR linewidths are presented. It is concluded that, using the ultra- high-resolution technique, a difference could be observed with high Z value spin one- half nuclei such as Pt, T1, Xe. Other nuclei can also be considered.

The Search for Parity Violation in Chiral Molecules

“…In 1986, Barra, Robert, and Wiesenfeld discussed the possibility of measuring PV in NMR observables such as the nuclear magnetic shielding, the nuclear spin-spin coupling, and the spin-rotation coupling [107][108][109][110][111]. From relativistic extended H€ uckel calculations, they estimated that PV shifts in the nuclear magnetic shielding are in the mHz range for chiral molecules containing heavy elements [107,108].…”

Wie wichtig ist Paritätsverletzung für die molekulare und biomolekulare Chiralität?

“…[20,31,32] Wegen der Parit‰tsverletzung werden die entsprechenden ‹bergangsenergien hn S und hn R als geringf¸gig verschieden erwartet. F¸r die Verwirklichung solcher Experimente im Radiofrequenzbereich wurde die NMR-Spektroskopie diskutiert, [60,61] und im Mikrowellenbereich wurden ‹berschallstrahlen von CHFClBr bei niedriger effektiver Temperatur T untersucht, wobei eine bescheidene Doppler-begrenzte Schranke von Dn D /n 9 7 Â 10 À7 T=K=m=u p f¸r die Abwesenheit parit‰tsverletzender Aufspaltungen ermittelt wurde. [62] Des Weiteren wurde f¸r eine IR-Bande von CHFClBr, die Koinzidenzen mit CO 2 -Laserlinien zeigt, eine erste vollst‰ndige Rotationsanalyse gegeben, weshalb die ultrahochauf-lˆsende Sub-Doppler-Spektroskopie an diesem System vorgeschlagen wurde.…”

Parity violation in nuclear magnetic resonance frequencies of chiral tetrahedral tungsten complexes NWXYZ (X, Y, Z = H, F, Cl, Br or I)

“…[32][33][34][35][36] Experimental detection of nuclear magnetic resonance (NMR) frequency shifts is considered to be a feasible route towards a first observation of PV in chiral molecules. 16,17,19,21,22 In contrast to nuclear spin-independent molecular PV effects aimed for in high-resolution vibrational spectroscopy, which may face difficulties in achieving an accuracy superior to high-precision atomic experiments on heavy elements such as cesium, [37][38][39][40] a successful measurement of nuclear spin-dependent PV effects promises to give insight into hadronic weak interactions inside the nucleus. 41 The reason for this is that for most nuclei the dominant contribution to the nuclear spin-dependent weak interaction between electrons and nuclei 16,42 comes from the nuclear anapole moment, [43][44][45] which is caused by parity violating interactions within the nucleus and which has only been measured once before in 133 Cs by Wieman and co-workers.…”

“…1-5 Proposed experimental schemes to detect parity violation (PV) shifts in properties of chiral molecules range from Mössbauer spectroscopy 6 to vibrational spectroscopy, 5, 7-13 electron paramagnetic resonance (EPR) spectroscopy, 14,15 rotational spectroscopy, 8 nuclear magnetic resonance (NMR) spectroscopy [16][17][18][19][20][21][22][23] including nuclear spinspin couplings, 24,25 quantum beats in optical rotation, 26 and finally tunneling dynamics of chiral molecules. [27][28][29][30][31] Despite some great efforts to measure such tiny PV effects in chiral molecules, which are expected to lie in the μHz to Hz region, all experiments have to be considered unsuccessful or unconvincing so far, despite occasional claims to the contrary (for a detailed discussion see Ref.…”