{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,14]],"date-time":"2025-10-14T08:11:45Z","timestamp":1760429505638,"version":"build-2065373602"},"reference-count":72,"publisher":"Wiley","issue":"16","license":[{"start":{"date-parts":[[2008,10,10]],"date-time":"2008-10-10T00:00:00Z","timestamp":1223596800000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["chemistry-europe.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["ChemPhysChem"],"published-print":{"date-parts":[[2008,11,10]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>Addition of \u201cinert\u201d tetrabutylammonium hexafluorophosphate (Bu<jats:sub>4<\/jats:sub>NPF<jats:sub>6<\/jats:sub>) to a solution of <jats:bold>TMDO\/DDQ<\/jats:bold> in dichloromethane (where <jats:bold>TMDO=<\/jats:bold>2,2,6,6\u2010tetramethylbenzo[1,2\u2010d;4,5\u2010d]bis[1,3]\u2010dioxole, donor, and <jats:bold>DDQ=<\/jats:bold>diclorodicyano\u2010p\u2010benzoquinone, acceptor) is accompanied by drastic changes in the electronic spectrum, which are related to the appearance of the <jats:bold>DDQ<\/jats:bold><jats:sup><jats:bold>\u2212<\/jats:bold>.<\/jats:sup> and <jats:bold>TMDO<\/jats:bold><jats:sup>+.<\/jats:sup> ion radicals and a decrease in the concentration of the neutral molecules and the charge\u2010transfer complex [<jats:bold>TMDO,DDQ<\/jats:bold>]. These changes point to a considerable rise (of about three orders of magnitude) in the apparent electron\u2010transfer equilibrium constant (<jats:italic>K<\/jats:italic><jats:sub>ET<\/jats:sub>) for this donor\/acceptor pair upon increasing the electrolyte concentration from 0 to 0.5\u2009<jats:sc>M<\/jats:sc>. Accordingly, the ion\u2010radical fractions and <jats:italic>K<\/jats:italic><jats:sub>ET<\/jats:sub> values are higher in dichloromethane, at high electrolyte concentrations, than in acetonitrile (where the effect of Bu<jats:sub>4<\/jats:sub>NPF<jats:sub>6<\/jats:sub> is less pronounced). Similar trends of the apparent equilibrium constants are observed for the tetramethyl\u2010p\u2010phenylenediamine\/tetracyanoethylene pair. Electron\u2010transfer equilibrium constants for both donor\/acceptor dyads obtained from spectral measurements are related to those derived from the redox potentials of the reactants. The effects of media variations on the electron\u2010transfer equilibria are discussed within the ion\u2010pairing and ionic\u2010activity frameworks.<\/jats:p>","DOI":"10.1002\/cphc.200800470","type":"journal-article","created":{"date-parts":[[2008,10,11]],"date-time":"2008-10-11T02:43:20Z","timestamp":1223693000000},"page":"2406-2413","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":13,"title":["Spectroscopic and Electrochemical Evaluation of Salt Effects on Electron\u2010Transfer Equilibria between Donor\/Acceptor and Ion\u2010Radical Pairs in Organic Solvents"],"prefix":"10.1002","volume":"9","author":[{"given":"Sergiy V.","family":"Rosokha","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Duoli","family":"Sun","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jeffrey","family":"Fisher","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jay K.","family":"Kochi","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2008,10,31]]},"reference":[{"key":"e_1_2_7_1_2","unstructured":"\u00a0"},{"volume-title":"Salt effects in organic and organometallic chemistry","year":"1992","author":"Loupy A.","key":"e_1_2_7_2_2"},{"key":"e_1_2_7_3_2","doi-asserted-by":"publisher","DOI":"10.1021\/cr00014a001"},{"volume-title":"Vols. 1 and 2","year":"1972","author":"reactions ion pairs in organic","key":"e_1_2_7_4_2"},{"key":"e_1_2_7_5_2","unstructured":"\u00a0"},{"volume-title":"Introduction to physical organic chemistry","year":"1968","author":"Kosower E. M.","key":"e_1_2_7_6_2"},{"volume-title":"Radical ions","year":"1968","author":"Kaiser E. T.","key":"e_1_2_7_7_2"},{"key":"e_1_2_7_8_2","doi-asserted-by":"publisher","DOI":"10.1021\/cr990410"},{"key":"e_1_2_7_9_2","doi-asserted-by":"publisher","DOI":"10.1021\/cr0300439"},{"key":"e_1_2_7_10_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja01638a093"},{"key":"e_1_2_7_11_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja01534a045"},{"key":"e_1_2_7_12_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja01016a002"},{"key":"e_1_2_7_13_2","doi-asserted-by":"publisher","DOI":"10.1021\/jp9834457"},{"key":"e_1_2_7_14_2","unstructured":"\u00a0"},{"key":"e_1_2_7_15_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja037098c"},{"key":"e_1_2_7_16_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja034831r"},{"key":"e_1_2_7_17_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja026417h"},{"key":"e_1_2_7_18_2","doi-asserted-by":"publisher","DOI":"10.1021\/jp046078"},{"key":"e_1_2_7_19_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja016335d"},{"key":"e_1_2_7_20_2","unstructured":"\u00a0"},{"key":"e_1_2_7_21_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja00386a063"},{"key":"e_1_2_7_22_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja00066a035"},{"key":"e_1_2_7_23_2","doi-asserted-by":"publisher","DOI":"10.1021\/ar0681124"},{"key":"e_1_2_7_24_2","unstructured":"\u00a0"},{"key":"e_1_2_7_25_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja00259a035"},{"key":"e_1_2_7_26_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja00300a060"},{"key":"e_1_2_7_27_2","doi-asserted-by":"publisher","DOI":"10.1039\/p29940001901"},{"key":"e_1_2_7_28_2","doi-asserted-by":"publisher","DOI":"10.1111\/j.1751-1097.1998.tb02503.x"},{"key":"e_1_2_7_29_2","doi-asserted-by":"publisher","DOI":"10.1039\/b106798b"},{"key":"e_1_2_7_30_2","unstructured":"\u00a0"},{"key":"e_1_2_7_31_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0065-3160(08)60077-5"},{"key":"e_1_2_7_32_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0065-3160(00)35014-6"},{"key":"e_1_2_7_33_2","unstructured":"For the salt effects on related redox equilibria see:"},{"key":"e_1_2_7_34_2","doi-asserted-by":"publisher","DOI":"10.1039\/c39890000813"},{"key":"e_1_2_7_35_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja00047a064"},{"key":"e_1_2_7_36_2","first-page":"39","volume":"16","author":"Bockman T. M.","year":"1992","journal-title":"New J. Chem."},{"key":"e_1_2_7_37_2","unstructured":"For the systems with donor\/acceptor potential differences \u0394E>0.5 V the ratios of the product\u2010to\u2010reactant concentrations (or vice versa) are higher than 108 which hinders the experimental measurements of all the components of Equation (1).[12]"},{"key":"e_1_2_7_38_2","unstructured":"\u00a0"},{"volume-title":"Organic chemistry of electrolyte solutions","year":"1975","author":"Gordon J. E.","key":"e_1_2_7_39_2"},{"volume-title":"Physical chemistry of electrolytic solutions","year":"1958","author":"Harned H. S.","key":"e_1_2_7_40_2"},{"key":"e_1_2_7_41_2","unstructured":"\u00a0"},{"key":"e_1_2_7_42_2","doi-asserted-by":"publisher","DOI":"10.1002\/cphc.200500640"},{"key":"e_1_2_7_43_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja051063q"},{"key":"e_1_2_7_44_2","doi-asserted-by":"publisher","DOI":"10.1002\/chem.200701420"},{"key":"e_1_2_7_45_2","unstructured":"\u00a0"},{"key":"e_1_2_7_46_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja058171x"},{"key":"e_1_2_7_47_2","doi-asserted-by":"publisher","DOI":"10.1021\/om051101e"},{"key":"e_1_2_7_48_2","unstructured":"\u00a0"},{"key":"e_1_2_7_49_2","doi-asserted-by":"publisher","DOI":"10.1021\/jp068994o"},{"key":"e_1_2_7_50_2","unstructured":"Note that {D+.+A\u2212.} represent herein (either in contact or separated) ion pairs or solvated \u201cfree\u201d ion radicals."},{"key":"e_1_2_7_51_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja069149m"},{"key":"e_1_2_7_52_2","unstructured":"\u00a0"},{"volume-title":"Computation of solution equilibria","year":"1988","author":"Meloun M.","key":"e_1_2_7_53_2"},{"volume-title":"The determination and use of stability constants","year":"1988","author":"Martel A. E.","key":"e_1_2_7_54_2"},{"key":"e_1_2_7_55_2","unstructured":"These (concentration\u2010based) \u201capparent\u201d constants must be distinguished from the activity\u2010based (and media\u2010independent) \u201cthermodynamic\u201d equilibrium constants.[17a b]"},{"volume-title":"Electrochemical methods. Fundamentals and applications","year":"1980","author":"Bard A. J.","key":"e_1_2_7_56_2"},{"key":"e_1_2_7_57_2","doi-asserted-by":"publisher","DOI":"10.1007\/978-94-011-0691-7"},{"key":"e_1_2_7_58_2","unstructured":"Note that \u201cformal\u201d redox potentials represent experimentally measured values related to the concentrations of oxidized and reduced species Eexp=E+(RT\/nF)ln([Ox]\/[Red]) where [Ox] is either [D+.] or [A] and [Red] is [D] or [A\u2212.]. Such potentials must be distinguished from \u201cstandard\u201d redox potentials Eo which are based on the activities of the redox species (see discussion in refs. [17a] and [17b])."},{"key":"e_1_2_7_59_2","unstructured":"Note that theKCTandKETconstants (and the changes of their apparent values with the ionic strength) are independent and the material balance for tree\u2010state equilibrium in Equation (2) includes also neutral species. These facts imply an independence of the variations in the charge\u2010transfer complex and the ion\u2010radical\u2010pair concentrations (e.g. the absorption of the [TMDO DDQ] complex decreases while that of theDDQ\u2212.anion radicals exhibits saturation at high concentrations of Bu4NPF6 see Figure 3)."},{"key":"e_1_2_7_60_2","unstructured":"The changes in the charge\u2010transfer equilibrium constants with the electrolyte also contribute to the spectrally measured equilibrium shifts but theKCTvariation with the solvent\/salt (see Table 1) is much less pronounced. Therefore the following discussion will concentrate on theKETvalues."},{"key":"e_1_2_7_61_2","unstructured":"\u00a0"},{"key":"e_1_2_7_62_2","doi-asserted-by":"publisher","DOI":"10.1021\/cr040087x"},{"key":"e_1_2_7_63_2","unstructured":"Note that ion pairing and ionic activities are strongly correlated and their separation is rather arbitrary; for example the choice of interionic separation below which the species are considered as ion pairs depends on an arbitrary convention.[20a]"},{"volume-title":"Physical Chemistry","year":"1998","author":"Atkins P.","key":"e_1_2_7_64_2"},{"key":"e_1_2_7_65_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja01249a028"},{"key":"e_1_2_7_66_2","unstructured":"The values calculated from the spectral data are somewhat higher than those estimated from the differences in the redox potentials for Bu4NPF6concentrations between about 0.02 and about 0.2\u2009M especially for theTMPD\/TCNEpair. This result indicates that under such conditions the electron\u2010transfer equilibria might be noticeably affected by interactions between oppositely charged ion radicals (and\/or neutral donors and acceptors)."},{"key":"e_1_2_7_67_2","doi-asserted-by":"publisher","DOI":"10.1021\/jo011068f"},{"key":"e_1_2_7_68_2","unstructured":"\u00a0"},{"key":"e_1_2_7_69_2","doi-asserted-by":"publisher","DOI":"10.1021\/jp991381"},{"key":"e_1_2_7_70_2","doi-asserted-by":"publisher","DOI":"10.1139\/v05-262"},{"key":"e_1_2_7_71_2","doi-asserted-by":"publisher","DOI":"10.1007\/s10953-007-9121-x"},{"key":"e_1_2_7_72_2","doi-asserted-by":"publisher","DOI":"10.1002\/jcc.1161"}],"container-title":["ChemPhysChem"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/api.wiley.com\/onlinelibrary\/tdm\/v1\/articles\/10.1002%2Fcphc.200800470","content-type":"unspecified","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/chemistry-europe.onlinelibrary.wiley.com\/doi\/pdf\/10.1002\/cphc.200800470","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,14]],"date-time":"2025-10-14T07:32:23Z","timestamp":1760427143000},"score":1,"resource":{"primary":{"URL":"https:\/\/chemistry-europe.onlinelibrary.wiley.com\/doi\/10.1002\/cphc.200800470"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2008,10,31]]},"references-count":72,"journal-issue":{"issue":"16","published-print":{"date-parts":[[2008,11,10]]}},"alternative-id":["10.1002\/cphc.200800470"],"URL":"https:\/\/doi.org\/10.1002\/cphc.200800470","archive":["Portico"],"relation":{},"ISSN":["1439-4235","1439-7641"],"issn-type":[{"type":"print","value":"1439-4235"},{"type":"electronic","value":"1439-7641"}],"subject":[],"published":{"date-parts":[[2008,10,31]]},"assertion":[{"value":"2008-07-24","order":0,"name":"received","label":"Received","group":{"name":"publication_history","label":"Publication History"}},{"value":"2008-10-31","order":3,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}]}}