Radical Cation and Dication Derived from 4,8-Diethylbenzo[1,2-d:4,5-d']-bis[1,2,3]trithiole [DEBBT]: Change of Electronic State from Singlet-State Dication DEBBT (2+)-S to Triplet-State Dimer 2DEBBT (2+)-T in D_2SO_4 and CD_3 CN Solutions

摘要

4,8-Diethylbenzo[1,2-d:4,5-d']bis[1,2,3] trithiole [DEBGT] was oxidized using concentrated D_2SO_4, leading to the generation of the radical cation DEBBT (.+) which was verified by ESR spectroscopy. DEBBT (.+) in the solution was further oxidized to produce the dication DEBBT(2+), as determined by ~1H and ~(13)C NMR spectroscopy. DEBBT (2+), was also prepared by treating DEBBT 1-oxide [DEBBT 1-O] with concentrated D_2SO_4, and was verified by ~1H and ~(13)C NMR spectroscopy. The ~(13)C NMR chemical shifts of DEBBT(2+), calculated by the density functional theoretical (DFT) method at the B3LYP6-31G level, correlated well with those obtained experimentally. The ESR signal of DEBBT(2+) generated from DEBBT 1-O was observed in solution, which implies that the singlet-state dication DEBBT(2+)-S isomerizes to the triplet-state dication DEBBT (2+)-S isomerizes to the triplet-state dication DEBBT (2+)-T, and that two molecules of DEBBT (2+)-T further form a spin pair at one trithiole ring with significant distance between the two radical centers, The oxidation of DEBBT with one or two equivalents of single-electron oxidizing reagents produced DEBBT (.+) and DEBBT (2+), and the salts were isolated in a stable form. However, the DEBBT (2+) that was prepared by oxidation with NOPF_6 proved silent for NMR in CD_3CN, while ESR was active. The stability, electronic state, and NMR and ESR spectroscopy of the dication are affected by solvation with D_2SO_4 and CD_3CN. The optimized structures and the total energy of the singlet- and triplet-state dication were calculated using the DFT method at the B3LYP6-31G level, which shows that the structures of the singlet- and triplet-state dications have a completely planar form with 1.7 kcal/mol as the total energy difference between them.