Pichlmaier, Markus and Winter, Rainer F. and Zabel, Manfred and Zalis, Stanislav (2009) Electron Transfer Across Multiple Hydrogen Bonds: The Case of Ureapyrimidinedione-Substituted Vinyl Ruthenium and Osmium Complexes. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 131 (13). pp. 4892-4903. ISSN 0002-7863,
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Ruthenium and osmium complexes 2a,b and 3a,b featuring the N-4,6-dioxo-5,5-dibutyl- or the N-4,6-dioxo-5,5-di-(2-propenyl)-1,4,5,6-tetrahydropyrimidin-2-yl-N'(4-ethenylphenyl)-urea ligand dimerize by a self-complementary quadruply hydrogen-bonding donor/donor/acceptor/acceptor (DDAA) motif. We provide evidence that the dimeric structures are maintained in nonpolar solvents and in 0.1 M NBu4PF6/CH2Cl2 supporting electrolyte solution. All complexes are reversibly oxidized in two consecutive two-electron oxidations (Delta E-1/2 approximate to 500 mV) without any discernible potential splitting for the oxidation of the individual hydrogen-bridged redox active moieties. IR and UV/vis/NIR spectroelectrochemistry show a one-step conversion of the neutral to the dication without any discernible features of an intermediate monooxidized radical cation. Oxidation-induced IR changes of the NH and CO groups that are involved in hydrogen bonding are restricted to the styryl-bonded urea NH function. IR band assignments are aided by quantum chemical calculations. Our experimental findings clearly show that, at least in the present systems, the ureapyrimidinedione (Upy) DDAA hydrogen-bonding motif does not support electron transfer. The apparent reason is that neither of the hydrogen-bonding functionalities contributes to the occupied frontier levels. This results in nearly degenerate pairs of MOs representing the in-phase and out-of-phase combinations of the individual monomeric building blocks.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | DISTANCE DEPENDENCE; DELTA-E-1/2 VALUES; CRYSTAL-STRUCTURE; PHOTOSYSTEM-II; LOW-BARRIER; DELOCALIZATION; OXIDATION; SYSTEMS; PROBES; MODEL; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Anorganische Chemie > Alumni or Retired Professors > Arbeitskreis Prof. Dr. Rainer Winter |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 18 Sep 2020 06:37 |
| Last Modified: | 18 Sep 2020 06:37 |
| URI: | https://pred.uni-regensburg.de/id/eprint/29129 |
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