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Carbazolyl Nitrenium Ion: Electron Configuration And Antiaromaticity Assessed By Laser Flash Photolysis, Trapping Rate Constants, Product Analysis, And Computational Studies, Arthur Winter, Harry H. Gibson, Daniel E. Falvey
Carbazolyl Nitrenium Ion: Electron Configuration And Antiaromaticity Assessed By Laser Flash Photolysis, Trapping Rate Constants, Product Analysis, And Computational Studies, Arthur Winter, Harry H. Gibson, Daniel E. Falvey
Arthur Winter
Laser flash photolysis of 1-(carbazol-9-yl)-2,4,6-trimethylpyridinium tetrafluoroborate generates the carbazolyl nitrenium ion (τ = 333 ns, kobs = 3.0 × 106 M-1s-1) having absorption bands at 570 and 620 nm in CH3CN. The nitrenium ion is found to have reactivity comparable to structurally similar closed-shell diarylnitrenium ions, but spectroscopic evidence favors an open-shell singlet diradical assignment for the observed nitrenium ion. The carbazolyl nitrenium ion is also more reactive than diarylnitrenium ions as a likely result of antiaromatic character. Ab initio and hybrid DFT calculations were performed to address the degree of antiaromaticity in this and similar nitrenium ions through analysis …
Benzylic Cations With Triplet Ground States: Computational Studies Of Aryl Carbenium Ions, Silylenium Ions, Nitrenium Ions, And Oxenium Ions Substituted With Meta Π Donors, Arthur Winter, Daniel E. Falvey, Christopher J. Cramer, Benjamin F. Gherman
Benzylic Cations With Triplet Ground States: Computational Studies Of Aryl Carbenium Ions, Silylenium Ions, Nitrenium Ions, And Oxenium Ions Substituted With Meta Π Donors, Arthur Winter, Daniel E. Falvey, Christopher J. Cramer, Benjamin F. Gherman
Arthur Winter
Density functional theory (B3LYP/6-31G(d,p)) was used to predict the effect of meta substitution on aryl cationic (Ar−X+) species, including aryloxenium ions, arylsilylenium ions, arylnitrenium ions, and arylcarbenium ions. Multireference second-order perturbation theory (CASPT2) calculations were used to benchmark the quantitative accuracy of the DFT calculations for representative systems. Substituting the meta positions on these species with π donors stabilizes a π,π* diradical state analogous to the well-known m-xylylene diradical. Notably, the 3,5-bis(N,N-dimethylamino)benzyl cation is predicted to have a triplet ground state by 1.9 kcal/mol by DFT and to have essentially degenerate singlet−triplet states at the CASPT2(10,9) level of theory. Adding …