15546-75-5Relevant articles and documents
Excited-State Conformational/Electronic Responses of Saddle-Shaped N, N ′-Disubstituted-Dihydrodibenzo[ a, c ]phenazines: Wide-Tuning Emission from Red to Deep Blue and White Light Combination
Zhang, Zhiyun,Wu, Yu-Sin,Tang, Kuo-Chun,Chen, Chi-Lin,Ho, Jr-Wei,Su, Jianhua,Tian, He,Chou, Pi-Tai
, p. 8509 - 8520 (2015)
A tailored strategy is utilized to modify 5,10-dimethylphenazine (DMP) to donor-acceptor type N,N′-disubstituted-dihydrodibenzo[a,c]phenazines. The representative compounds DMAC (N,N′-dimethyl), DPAC (N,N′-diphenyl), and FlPAC (N-phenyl-N′-fluorenyl) reveal significant nonplanar distortions (i.e., a saddle shape) and remarkably large Stokes-shifted emission independent of the solvent polarity. For DPAC and FlPAC with higher steric hindrance on the N,N′-substituents, normal Stokes-shifted emission also appears, for which the peak wavelength reveals solvent-polarity dependence. These unique photophysical behaviors are rationalized by electronic configuration coupled conformation changes en route to the geometry planarization in the excited state. This proposed mechanism is different from the symmetry rule imposed to explain the anomalously long-wavelength emission for DMP and is firmly supported by polarity-, viscosity-, and temperature-dependent steady-state and nanosecond time-resolved spectroscopy. Together with femtosecond early dynamics and computational simulation of the reaction energy surfaces, the results lead us to establish a sequential, three-step kinetics. Upon electronic excitation of N,N′-disubstituted-dihydrodibenzo[a,c]phenazines, intramolecular charge-transfer takes place, followed by the combination of polarization stabilization and skeletal motion toward the planarization, i.e., elongation of the π-delocalization over the benzo[a,c]phenazines moiety. Along the planarization, DPAC and FlPAC encounter steric hindrance raised by the N,N′-disubstitutes, resulting in a local minimum state, i.e., the intermediate. The combination of initial charge-transfer state, intermediate, and the final planarization state renders the full spectrum of interest and significance in their anomalous photophysics. Depending on rigidity, the N,N′-disubstituted-dihydrodibenzo[a,c]phenazines exhibit multiple emissions, which can be widely tuned from red to deep blue and even to white light generation upon optimization of the surrounding media.
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Root et al.
, p. 778 (1978)
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MECHANISM OF BROMINATION OF SOME AROMATIC AMIDES BY N-BROMOSUCCINIMIDE
Koshechko, V. G.,Inozemtsev, A. N.
, p. 315 - 318 (2007/10/02)
It was established that in polar organic solvents N-bromosuccinimide acts as a one-electron oxidizing agent for tertiary aromatic amines and N,N-substituted dihydrophenazines.Depending on the structure of the amines and the nature of the medium, the maximum current concentration of the radical-cations in these reactions amounts to 90percent of the initial amine.It was shown that the intermediate radical-cations of the substituted amines can then be transformed into the bromination products by reaction with the bromide ion formed during dissociation of the bromosuccinimide radical- anion.The mechanism of the investigated reactions in the light and in the dark is discussed.
