%0 Journal Article %1 Hilgers.1994 %A Hilgers, Frank %A Kaim, Wolfgang %A Schulz, Andreas %A Zalis, Stanislav. %D 1994 %J Journal of the Chemical Society, Perkin Transactions 2: Physical Organic Chemistry %K UV absorption cation cation;transition cation;vibrational dialkyldihydrodiazinium dimerization electronic pi radical stable structure %N 1 %P 135--138 %T Electronic absorption spectroscopy of some exceptionally stable 1,4-dialkyl-1,4-dihydro-1,4-diazinium radical cations: Assignment of transitions, vibrational structure and effects of p-p dimerization %X UV-VIS Absorption spectroscopy of the unusually stable and structurally characterized radical cations 1,4-diethyl-1,4-dihydropyrazinium (1.bul.+), 1,4-diethyl-1,4-dihydroquinoxalinium monomer (2.bul.+) and p-p dimer (2.bul.+)2, 1,4,6,7-tetramethyl-1,4-dihydroquinoxalinium (3.bul.+) and 5,10-diethyl-5,10-dihydrophenazinium (4.bul.+) reveals low-energy p$\rightarrow$p* transitions with different intensities and partial vibrational structuring. The spectra of the radical cations and of the corresponding dications (12+-42+) have been analyzed with the help of INDO/S calcns.; the resulting assignments could also be rationalized using HMO theory. Both higher sym. systems 1.bul.+ and 4.bul.+ exhibit vibrationally split long-wavelength bands. The addnl. long-wavelength absorption of the p-p dimer (1.bul.+)22 (KD ca. 4 $\times$ 103) is assigned to a charge transfer transition, similar to that of methylviologen radical dimer. on SciFinder(R)

@article{Hilgers.1994, abstract = {UV-VIS Absorption spectroscopy of the unusually stable and structurally characterized radical cations 1,4-diethyl-1,4-dihydropyrazinium (1.bul.+), 1,4-diethyl-1,4-dihydroquinoxalinium monomer (2.bul.+) and \textgreek{p}-\textgreek{p} dimer [(2.bul.+)2], 1,4,6,7-tetramethyl-1,4-dihydroquinoxalinium (3.bul.+) and 5,10-diethyl-5,10-dihydrophenazinium (4.bul.+) reveals low-energy \textgreek{p}$\rightarrow$\textgreek{p}* transitions with different intensities and partial vibrational structuring. The spectra of the radical cations and of the corresponding dications (12+-42+) have been analyzed with the help of INDO/S calcns.; the resulting assignments could also be rationalized using HMO theory. Both higher sym. systems 1.bul.+ and 4.bul.+ exhibit vibrationally split long-wavelength bands. The addnl. long-wavelength absorption of the \textgreek{p}-\textgreek{p} dimer (1.bul.+)22 (KD ca. 4 $\times$ 103) is assigned to a charge transfer transition, similar to that of methylviologen radical dimer. [on SciFinder(R)]}, added-at = {2022-06-15T11:26:56.000+0200}, author = {Hilgers, Frank and Kaim, Wolfgang and Schulz, Andreas and Zalis, Stanislav.}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/25767125e082a2e256cf94d3f9c3c7f17/huebleriac}, interhash = {c3770b0d4c17884f0f9441d6617c2013}, intrahash = {5767125e082a2e256cf94d3f9c3c7f17}, issn = {0300-9580}, journal = {Journal of the Chemical Society, Perkin Transactions 2: Physical Organic Chemistry}, keywords = {UV absorption cation cation;transition cation;vibrational dialkyldihydrodiazinium dimerization electronic pi radical stable structure}, number = 1, pages = {135--138}, timestamp = {2022-06-15T09:26:56.000+0200}, title = {Electronic absorption spectroscopy of some exceptionally stable 1,4-dialkyl-1,4-dihydro-1,4-diazinium radical cations: Assignment of transitions, vibrational structure and effects of \textgreek{p}-\textgreek{p} dimerization}, year = 1994 }