2,3,7,8-Tetramethoxythianthrene. A novel ground state triplet dication, the neutral photogenerated triplet, and the radical cation

Abstract

25) That the type 2 transition (see Figure 4) for QNO•is divided into the 2.17and 1.90-eV bands (see Table I) and mixes greatly with the 7 -9 transition (type A) should be noted. ( 26) It Is noted that the orbital energy change of MO 10 and 11 (see Figure 4) of ANO•by introducing the N atom at the 8 position (see Table I) is quite small, since the symmetry of these orbitals is a2, having the nodal plane through the C2 axis, so that the atomic orbital coefficient at the atoms along the C2 axis is zero. We can find the same relation as the above in anthracene and naphthalene, too. The atomic orbital coefficients at the 1 and 8 positions of the anthracene anion radical and at the 1, 4, 6, and 9 positions of the naphthalene anion radical are zero for the lowest vacant MO and the next higher MO of the former, and almost are zero for the lowest vacant MO of the latter. The orbital energies of these MO's are therefore insensitive to the replacement of the carbon atoms by nitrogen. (27) In the case of pyrazine di-W-oxide this fact was confirmed by analysis of photoelectron spectra.24 (28) (a) J.

Photoinduced Charge Migration in the Picosecond Regime for Thianthrene-Linked Acridinium Ions

“…The thianthrene ring system ( 1 ) has a novel redox chemistry that has been the subject of study for three decades. The sulfur heterocycle undergoes a reversible one-electron oxidation ( E 1/2 = 1.23 vs SCE, CH 3 CN), yielding a radical cation species ( 2 ) that is stable enough to be isolated for independent investigation; magnetic resonance studies on the cation have included ESR, ENDOR, and CIDEP measurements . Photoinduced electron transfer involving thianthrene (TH) as an electron donor has been studied, including a report of trapping of the radical cation .…”

Tuning Spin-State Preference by Substituents: A Case Study of Thianthrene Dication

“…In 1976, Goldberg et al investigated the spin state for the dication of a derivative of thianthrene (1), 2,3,7,8-tetramethoxythianthrene (2). 14 The EPR measurements supported the triplet ground state of 2 2+ . Since then, however, reinvestigations about the spin state of 2 2+ have never been carried out.…”

“…These results are inconsistent with the conclusion from the previous EPR analysis for 2 2+ in frozen solution. 14 1,4,6,9-Tetramethoxythianthrene. When methoxy groups are substituted at the 2,3,7,8-positions, the 4b 1u and 2b 2g orbitals of 1 are perturbed by the out-of-phase orbital interactions.…”

1,4-Dithiin annelated with bicyclo[2.2.2]octene units: experimental and theoretical evidence for the aromaticity in 1,4-dithiin dication

“…The 1 H NMR spectra of this dication showed broad signals at room temperature 2 while the Dm = 2 transition was observed by EPR at low temperature. 3 From the EPR experiments, it was concluded that this dication is ground state triplet and the energy gap between the singlet and triplet states is < 1 kcal mol 21 . 3 These results are consistent with the X-ray structure of 1 2+ (SbCl 6 2 ) 2 , in which it was interpreted that this dication is divided into two cyanine subunits with each pdelocalization more favored than the cyclic p-conjugation as a whole.…”

“…3 From the EPR experiments, it was concluded that this dication is ground state triplet and the energy gap between the singlet and triplet states is < 1 kcal mol 21 . 3 These results are consistent with the X-ray structure of 1 2+ (SbCl 6 2 ) 2 , in which it was interpreted that this dication is divided into two cyanine subunits with each pdelocalization more favored than the cyclic p-conjugation as a whole. 4 Is the triplet state of non-expanded 1,4-dithiin dication itself also more stable than the singlet state which might have an aromatic stabilization?…”