pi-dimerization of pleiadiene radical cations at low temperatures revealed by UV-vis spectroelectrochemistry and quantum theory
| Autor: | František Hartl, Leonardus W. Jenneskens, Piet Th. van Duijnen, Carola Koper, Layo van het Goor, Remco W. A. Havenith |
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| Přispěvatelé: | Zernike Institute for Advanced Materials, Theoretical Chemistry |
| Jazyk: | angličtina |
| Rok vydání: | 2011 |
| Předmět: |
Quantum chemistry calculations
Dimer Photochemistry POLYCYCLIC AROMATIC-HYDROCARBONS chemistry.chemical_compound Ab initio quantum chemistry methods Electrochemistry Molecule General Materials Science CELL Electrical and Electronic Engineering ELECTRONIC-SPECTRA FIELD ACENAPHTHYLENE ROW ATOMS REDOX ION RADICALS Condensed Matter Physics Acenaphthylene Radical cation Dication Polarizable force fields Radical ion chemistry Absorption band Pleiadiene 2ND-ORDER PERTURBATION-THEORY DENSITY Pyrene pi-Dimerization Electronic absorption |
| Zdroj: | Journal of solid state electrochemistry, 15(10), 2107-2117 |
| ISSN: | 1432-8488 |
| Popis: | One-electron oxidation of the non-alternant polycyclic aromatic hydrocarbon pleiadiene and related cyclohepta[c,d]pyrene and cyclohepta[c,d]fluoranthene in THF produces corresponding radical cations detectable in the temperature range of 293-263 K only on the subsecond time scale of cyclic voltammetry. Although the EPR-active red-coloured pleiadiene radical cation is stable according to the literature in concentrated sulfuric acid, spectroelectrochemical measurements reported in this study provide convincing evidence for its facile conversion into the green-coloured, formally closed shell and, hence, EPR-silent pi-bound dimer dication stable in THF at 253 K. The unexpected formation of the thermally unstable dimeric product featuring a characteristic intense low-energy absorption band at 673 nm (1.84 eV; log epsilon (max) = 4.0) is substantiated by ab initio calculations on the parent pleiadiene molecule and the PF (6) (-) salts of the corresponding radical cation and dimer dication. The latter is stabilized with respect to the radical cation by 14.40 kcal mol(-1) (DFT B3LYP) [37.64 kcal mol(-1) (CASPT2/DFT B3LYP)]. An excellent match has been obtained between the experimental and TD-DFT-calculated UV-vis spectra of the PF (6) (-) salt of the pleiadiene dimer dication, considering solvent (THF) effects. |
| Databáze: | OpenAIRE |
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