Verhalten aromatischer Amine im angeregten Zustand in Lösung: Dihydrophenazin-Derivate

Intramolecular Charge Transfer and Ion Pairing inN,N-Diaryl Dihydrophenazine Photoredox Catalysts for Efficient Organocatalyzed Atom Transfer Radical Polymerization

“…In the absence of π* phenyl , such as in the case of 5,10-dimethyl-5,10dihydrophenazine, only one peak of exclusively LE character is observed at a blue-shifted λ max,abs of 337 nm. 25 After initial photon absorption, fast relaxation via internal conversion (IC) results in thermalization of the excited electron from S 2 (π LUMO+1 and π LUMO+7 ) to the lowest singlet excited state S 1 (π LUMO ), followed by ISC to the lowest triplet excited state (T 1 ) comprised of exclusively LE character (Figure 5A). The triplet quantum yield of PC 1 has been reported to be 0.26 at 77 K in 3-methylpentane.…”

“…The triplet quantum yield of PC 1 has been reported to be 0.26 at 77 K in 3-methylpentane. 25 Further, the electrostatic potential (ESP)-mapped electron density reveals minimal dipole moment (μ) change for PC 1 as it transitions from the ground state ( 1 PC) to 3 PC*, despite the slight increase in electron density on the core from δ = −0.68e to −0.80e (Figure 5A). Similar to PC 1, the initial photon absorption by PCs 2 and 3 consists of a combination of CT and LE character (Figures 4B and C).…”

Ultrafast Observation of a Photoredox Reaction Mechanism: Photoinitiation in Organocatalyzed Atom-Transfer Radical Polymerization

“…The quantum yield for PCH ISC was previously measured to be 0.26 in 3methylpentane solution at 77 K, supporting our assignment. 59 In the presence of MBP, a clear transient absorption from 2 MP • (D 1 ) was again observed (Figure S18) on time scales faster than 3 PCH*(T 1 ) growth, with a concentration dependence study affording an estimated bimolecular rate coefficient of k PET (PCH) = (3.6 ± 0.2) × 10 10 dm 3 mol −1 s −1 . As with PCF, electron transfer appears to occur from the first excited singlet state, 1 PCH*(S 1 ), under our experimental conditions.…”

“…The position of this feature is inconsistent with the absorption signature of the radical cation 2 PCH •+ (D 1 ), indicating that there is no PET from photoexcited PCH to DCM, and we instead assign the new feature to a triplet state, 3 PCH*­(T 1 ). The quantum yield for PCH ISC was previously measured to be 0.26 in 3-methylpentane solution at 77 K, supporting our assignment . In the presence of MBP, a clear transient absorption from 2 MP • (D 1 ) was again observed (Figure S18) on time scales faster than 3 PCH*­(T 1 ) growth, with a concentration dependence study affording an estimated bimolecular rate coefficient of k PET (PCH) = (3.6 ± 0.2) × 10 10 dm 3 mol –1 s –1 .…”

“Vibration induced emission” (VIE): <italic>N</italic>,<italic>N</italic>′-disubstituted- dihydrodibenzo[<italic>a</italic>,<italic>c</italic>]phenazines dual fluorescent mechanism

“…Huber 等 [47] 已经报道过一个具有较大 [43] ; 而 在固态时, 分子振动受限, 激发态分子仍是 V 型结构, 因此, 只表现出短波长蓝光发射, 这一预测与实验结 果相符. 另外, Yamaguchi 等 [49] 报道了一系列 9-苯基 蒽类化合物, 他们通过分子刚性化的修饰使其分子 平面化.…”