Rate and Driving Force for Protonation of Aryl Radical Anions in Ethanol

Abstract

Aryl radical anions created in liquid alcohols decay on the microsecond time scale by transfer of protons from the solvent. This paper reports a 4.5 decade range of rate constants for proton transfer from a single weak acid, ethanol, to a series of unsubstituted aryl radical anions, Ar-*. The rate constants correlate with free energy change, DeltaG(o), despite wide variations in the two factors that contribute to DeltaG(o): (a) the reduction potentials of the aryls and (b) the Ar-H* bond strengths in the product radicals. For aryl radical anions containing CH2OH substituents, such as 2,2'-biphenyldimethanol*- which is protonated with a rate constant of 3x10(9) s(-1), the faster rates do not fit well in the free energy correlation, suggesting a change in mechanism.

Intercalated metal–organic frameworks with high electronic conductivity as negative electrode materials for hybrid capacitors

“…0.1 V lower than that of the 2,6-Naph (COOLi) 2 electrode (ca. 0.8 V vs. Li/Li + ), as shown in Supplementary Figure 2c and agrees well with the prediction from the reduction potential of the aromatic unit shown in the above concept 26 . Next, the reversible specific capacity was determined from the galvanostatic charge-discharge measurement.…”

“…Although some reports have focused on the iMOF electrode with high-rate capability 18,23 , the high-rate performance at temperatures lower than 0°C and its mechanism of the highrate performance remain to be elucidated. To design an iMOF electrode that provides low resistance and favorable lowtemperature characteristics, we selected a dicarboxylate lithium salt containing a biphenyl (Bph) framework 10,11 based on the following characteristics: (i) stepwise formation of a stable complex with one and two lithium atoms per unit (Li − Bph − and Li 2− Bph 2− , respectively) 24 ; (ii) further stabilization of lithium through coordination with oxygen 24,25 ; and (iii) expectation of a lower reduction potential of the biphenyl dicarboxylate lithium salt than that of the naphthalene because biphenyl exhibits a lower reduction potential than naphthalene (0.45 V vs. Li/Li + for biphenyl compared to 0.51 V vs. Li/Li + for naphthalene) 26 . The electrochemical behavior of this material has already been reported as a preliminary step 23 .…”

Sensitized triplet–triplet annihilation upconversion in water and its application to photochemical transformations

“… 42 Furthermore, the spectra clearly show that photoinduced electron transfer reactions do not compete with the desired TTET, because the former would manifest themselves by intense absorption signals of the anthracene radical ions in the red. 43 , 44 Triplet anthracene spectra of ACA and MAMA are independent of the sensitizer used, but in the case of APA , we could only employ Rubpy as the sensitizer, because the bichromophoric triplet energy donors are almost completely insoluble in the presence of APA , which most likely serves as a crystallization-inducing counterion. These observations illustrate some of the difficulties in identifying water-soluble sensitizer-acceptor/annihilator couples.…”

Controlling Spin‐Correlated Radical Pairs with Donor–Acceptor Dyads: A New Concept to Generate Reduced Metal Complexes for More Efficient Photocatalysis

“…AS tern-Volmer analysis of the purely dynamic quenching yieldedarate constant of 3.6 10 8 m À1 s À1 .T he transient absorption spectrumr ight after the quenching process (inset of Figure 3a)d oes not show the absorption bands derived from the initial quenching product, i.e.,t he anthracene radical anion A À (maximaa t~700 nm and 360 nm). [75,76] However,t he spectroscopics ignatures of the reduced metal complex M À (Ru(bpy) 3 + )a re clearlyo bservable, with characteristic bipyridine radical anion bands at 505 nm and 360 nm (superimposed by the ascorbate radical anion) [77] as well as the bleach of the MLCT absorption band of the parentr uthenium(II) complex. [30,78] These results can be rationalized by af ast intramoleculare lectron transfer from the anthracener adical anion to the metal complex unit of the dyad (step 4i nS cheme 2b).…”