Effect of sequential deuteriation upon the solution electron affinity of benzene

Relative Solution Electron Affinities of Selectively Deuteriated Pyrenes: Correlations between Voltammetric, Electron Paramagnetic Resonance, and Semiempirical PM3 Data

“…2,4,5,7,9,. The potassium reduction of our synthesized 2,4,5,7,9,10-d 6 -pyrene (pyrene ) PY) in THF yields an anion radical solution that exhibits the expected EPR pattern from the desired 2,4,5,7,9,10-d 6 -PY •-, but this anion radical only accounts for 74.6% of the spectral intensity. It is necessary to include an 18.6% 1,2,4,5,7,9,10-d 7 -PY •-and a 6.8% 2,4,5,7,9-d 5 -PY •-contribution (in accordance with Table 1) to obtain a simulation that is a good representation of the real EPR spectrum (see Figure 1; the a H 's and a D 's are given in Table 2).…”

“…Thus, the mixtures of PY and 2,4,5,7,9,10-d 6 -PY were biased heavily toward the deuteriated system in terms of relative concentrations. This allows good resolution of the 2,4,5,7,9,10-d 6 -PY •-spectrum while unperturbed hyperfine components from PY •-can be found outside of the spectral region of 2,4,5,7,9,10-d 6 -PY •- (Figure 2).…”

“…A mixture of 79.3 mg of our (isotopically impure) 2,4,5,7,9,10-d 6 -PY sample (79.3 × 0.746/208 ) 0.284 mmol of 1f) and 1.1 mg (0.005 45 mmol) of PY in 20 mL of THF was reduced with a very deficient amount of potassium metal and further diluted with THF. Upon EPR analysis (173 K), the resulting anion radical solution exhibited both expected anion radicals along with the impurity anion radicals mentioned above.…”

“…Upon EPR analysis (173 K), the resulting anion radical solution exhibited both expected anion radicals along with the impurity anion radicals mentioned above. The EPR spectrum ( Figure 2) is best simulated with the ratio of the PY and 2,4,5,7,9,10-d 6 -PY anion radicals being [2,4,5,7,9,10-d 6 - Upper: low-field half (a 12 G scan is shown) of the EPR spectrum of our sample of 2,4,5,7,9,10-d6-pyrene at 173 K reduced with K in THF. Middle: computer simulation of the EPR spectrum for 2,4,5,7,9,10-d6-PY •-(coupling constants shown in Table 2).…”

“…The magnitude of the effect is dependent on the number of isotopically substituted sites. 6 For example, the more deuteriums on the benzene ring, the more positive is the reaction enthalpy for electron transfer from the benzene anion radical to deuteriated benzene. 6 The magnitude of the effect has also been linked to the spin and charge density at the isotopically substituted carbon atom.…”