A MARY study of radical anions of fluorinated benzenes

Simple rules for resolved level crossing spectra in magnetic field effects on reaction yields

“…al, 1985) that specifically explored level crossings in nonzero fields for radical pairs with equivalent nuclei in only one pair partner, and gave explicit expression for their position determined by the hyperfine coupling (HFC) constant. Such lines were later indeed experimentally observed in several systems by two teams 35 (Stass et al, 1995b;Saik et al, 1995;Grigoryants et al, 1998;Kalneus et al, 2006a). Furthermore, in a subsequent paper (Tadjikov et al, 1996) it was suggested and demonstrated in numerical simulations for several systems of simple structure, and confirmed in a proof-of-principle experiment, that hyperfine structure of the second pair partner may be revealed at the level crossing lines.…”

“…Although nuclei with spins 3 2 and higher, like 35,37 Cl ( 3 2 ) (Bagryansky et al, 1998), 27 Al ( 5 2 ), 69,71 Ga( 3 2 ), 113,115 In ( 92 ) (Sergey et al, 2012), 73 Ge( 92 ) (Shokhirev et al, 1991;Borovkov et al, 2003) occasionally occur in magnetic field effect experiments, so far the only resolved lines in multiple fields of Eq. (7) have been reported for systems containing sets of equivalent spin-1 2 nuclei, either protons or fluorines (Stass et al, 1995b;Saik et al, 1995;Grigoryants et al, 1998;Kalneus et al, 2006a). The best results making them promising for such applications were obtained 185 for radical anions of either hexafluorobenzene (six fluorines with a=13.7 mT) or octafluorocyclobutane (eight fluorines with a=15.1 mT) paired with a narrow partner radical cation.…”

“…Although the case of an even number of driving spins-1 2 is the most convenient, it is not the only possible one. Still staying with equivalent nuclei, one experimental case of three spins-1 2 has been reported, for the radical anion of 1,3,5trifluorobenzene complemented with a partner with a narrow ESR spectrum (Kalneus et al, 2006a). The only level-crossing 230 line here comes from the effective total spin 3 2 I = for three fluorines, as expected, and could in principle be used as a vehicle to obtain the ESR spectrum of the partner.…”

Simple rules for resolved level-crossing spectra in magnetic field effects on reaction yields

“…Several experimental reports of the resolved MARY spectra for systems with nonequivalent nuclei with large HFC constants, in all cases fluorines, have been published. These include radical anions of 1,2,3-trifluorobenzene (Kalneus et al, 2007), pentafluorobenzene (Kalneus et al, 2006b), and recently several fluorosubstituted diphenylacetylenes (Sannikova et al, 2019), again complemented with a radical cation with a narrow ESR spectrum. The spectra featured well-defined lines that were reproduced in simulations and were traced to clusters of level crossings in the spin system of the pair.…”

MARY spectroscopy in the presence of coordination compound Zn(hfac)2(PPO)2

“…The method was formulated for organic radical ions, and has proved useful in detecting several important classes of hitherto unseen radical ions with lifetimes of just several nanoseconds, such as primary solvent radical cations (holes) in irradiated alkanes [3] and radical ions of several fluorinated [4] and methylated [5] benzenes. The method is also useful for studies of reactions involving short-lived radical ions, such as the reactions of ion-molecular charge transfer [6,7], dimerization and higher aggregation [8], and monomolecular chemical decay [9].…”