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JP14

Theoretical MO study on electronic spectra of cycl[3.2.2]azine

○Yasuhiro Shigemitsu（Material Science Section, Industrial Tec. Center of Nagasaki），Yoshinori Tominaga（Faculty of Environmental Science, Nagasaki University）

Cyclazines, of which unique tricyclic structures and perfectly conjugated perimeters of sp2 hybridized carbon atoms, have attracted much attentions from theoretical chemists in analyzing the essential nature of aromaticity/anti aromaticity. Among a series of peripheral conjugated compounds, cycl[3.2.2]azine has been taken as an ideal [10]pai perimeter model bearing an isoelectronic system with [10]-anulene, aimed to assess its aromaticity from a topological viewpoint. Its physicochemical properties as well as chemical reactivity, however, have not yet satisfactory elucidated. In particular, the UV/Vis absorption bands have not fully analyzed in a theoretical way. Here we report the novel synthesis of cycl[3.2.2]azine derivatives and their electronic spectra, followed by a series of molecular orbital calculations (TD-DFT and MS-CASPT2) aimed to characterize the intense absorption peaks. Our results have shown that the absorption peak position associated with the lowest pai-pai excitation has been correctly predicted with both TD-DFT and MS-CASPT2. The corresponding oscillator strength, however, has been considerably underevaluated using TD-DFT. This abnormality has been corrected using highly accurate MS-CASPT2.