Diarylamine‐Fused Subporphyrins: Proof of Twisted Intramolecular Charge Transfer (TICT) Mechanism

Abstract

Diarylamine-fused subporphyrins 1 a and 1 b were synthesized from β,β-diiodo-meso-chloro subporphyrin 2 through a one-pot procedure involving nucleophilic aromatic substitution and S 1-type intramolecular fusion reaction as the first example of meso-nitrogen-embedded subporphyrin. While non-fused counterparts 3 b and 4 b display effective fluorescence quenching due to twisted intramolecular charge transfer (TICT) in CH Cl at room temperature, 1 b emits fluorescence with Φ =0.18 under the same conditions, because conformational twisting is not allowed due to the fused structure. In addition, the oxidative titration with tris(4-bromophenyl)ammoniumyl hexachloroantimonate gave cation radical 7 for 1 a and cation radical and dication for 1 b. Actually, cation radical 7 was isolated through separation over silica gel column but was found to slowly decompose in concentrated solutions.

Photoexcited Intramolecular Charge Transfer in Dye Sensitizers: Predictive In Silico Screening for Dye-Sensitized Solar Cell Devices

“…The presence of fused groups is known to affect ICT and reorganization energies owing to less distorted structures. However, they are also known to sometimes hinder the ICT process . To address the effect of the presence and absence of fused groups at the donor and π-spacer sites (see Table ), we analyze the structural changes in the different parts of the dye molecules followed by the photoexcitation and removal of electrons simultaneously identifying the ICT pathway and extent of π-conjugation.…”

Synthesis of Meso-Diarylaminocorroles via SNAr Reactions

“…The emission peaks of 6H were slightly red-shifted in polar solvents with Stokes shifts of 1050–2236 cm −1 , while the emission peaks of 7H were almost unchanged with Stokes shifts of 1066–1354 cm −1 , which indicated that the structural reorganization in the excited state was more significant in 6H . Nevertheless, they were unlikely to exhibit twisted intramolecular charge transfer (TICT)-like behaviors as seen in the meso -nitrocorroles 3H and 3Ga , and meso -arylaminosubporphyrins [27,38,39,40]. The optical properties of 4 to 8 are summarized in Table 1.…”

“…Heteroatom-embedded π-extended porphyrinoids have shown more perturbed electronic and optical properties as compared with heteroatom-substituted analogs. Thus, the next target may be heteroatom-embedded fused corroles [32,40,41,42,43,44]. Along with this line, diphenylamine-substituted corrole 6H was subjected to the conditions previously reported to synthesize diphenylamine-fused porphyrins, but all the attempts to obtain fused products failed.…”

Recent Advances in Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds

“… Reagents and conditions: (a) 595 318.2a or 318.2b (3 equiv), NaO t -Bu (12 equiv), DMF, 100 °C, 15 min; (b) 595 318.2a (3 equiv), DMF, rt, 30 min; (c) 595 NaO t -Bu (12 equiv), DMF, 100 °C, 10 min; (d) 596 318.2a or 318.2c (2.5 equiv), NaO t -Bu (10 equiv), DMF, 100 °C; (e) 596 BAHA (6.0 equiv), DCM, rt, 10 min; (f) 596 BAHA (6.0 equiv), DCM, rt, 15 min, then H 2 NNH 2 ·H 2 O. …”

“…Structurally related diarylamine-fused subporphyrins 318.4a – b were synthesized by the Osuka group through a one-pot procedure involving nucleophilic aromatic substitution followed by electron-transfer-mediated intramolecular C–H/C–I coupling (Scheme ). Of these two compounds, 318.4b showed a more red-shifted absorption attributed to the effective conjugation between the electron-donating dimethylamino group and the subporphyrin core. The fluorescence quantum yields (Φ f ) of 318.4a and 318.4b were found to be 0.21 and 0.18, respectively.…”