Hot Injection Processes in Optically Excited States: Molecular Design for Optimized Photocapture

2014 ◽  
Vol 118 (38) ◽  
pp. 21798-21805 ◽  
Author(s):  
Gil Katz ◽  
Mark A. Ratner ◽  
Ronnie Kosloff
Keyword(s):  
Excited States ◽  
Molecular Design ◽  
Hot Injection

Restriction of Access to Dark State: A New Mechanistic Model for Heteroatom-Containing AIE Systems

2019 ◽  
Author(s):  
Yujie Tu ◽  
Junkai Liu ◽  
Haoke Zhang ◽  
Qian Peng ◽  
Jacky W. Y. Lam ◽  
...  
Keyword(s):  
Excited States ◽  
Radiative Decay ◽  
Molecular Design ◽  
Mechanistic Model ◽  
Zinc Ion ◽  
Easy Access ◽  
Triplet States ◽  
Dark State ◽  
Ion Probe ◽  
Π State

Aggregation-induced emission (AIE) is an unusual photophysical phenomenon and provides an effective and advantageous strategy for the design of highly emissive materials in versatile applications such as sensing, imaging, and theragnosis. "Restriction of intramolecular motion" is the well-recognized working mechanism of AIE and have guided the molecular design of most AIE materials. However, it sometimes fails to be workable to some heteroatom-containing systems. Herein, in this work, we take more than one excited state into account and specify a mechanism –"restriction of access to dark state (RADS)" – to explain the AIE effect of heteroatom-containing molecules. An anthracene-based zinc ion probe named APA is chosen as the model compound, whose weak fluorescence in solution is ascribed to the easy access from the bright (π,π*) state to the closelying dark (n,π*) state caused by the strong vibronic coupling of the two excited states. By either metal complexation or aggregation, the dark state is less accessible due to the restriction of the molecular motion leading to the dark state and elevation of the dark state energy, thus the emission of the bright state is restored. RADS is found to be powerful in elucidating the photophysics of AIE materials with excited states which favor non-radiative decay, including overlap-forbidden states such as (n,π*) and CT states, spin-forbidden triplet states, which commonly exist in heteroatom-containing molecules.

Aza-substitution effect on the Q-band excitations of free-base porphin, chlorin, and bacteriochlorin: SAC-CI theoretical study

2005 ◽  
Vol 09 (05) ◽  
pp. 305-315 ◽  
Author(s):  
Jun-ya Hasegawa ◽  
Takayuki Kimura ◽  
Hiroshi Nakatsuji
Keyword(s):  
Dipole Moment ◽  
Excited States ◽  
Molecular Design ◽  
Decomposition Analysis ◽  
Substitution Effect ◽  
Transition Dipole Moment ◽  
Orbital Energy ◽  
Free Base ◽  
Transition Dipole ◽  
Near Degeneracy

Electronic structure of the excited states and absorption spectra of free-base azaporphins, azachlorin, and azabacteriochlorin were systematically investigated by SAC-CI calculations. Aza-substitution at the meso position affects the orbital energy of the next-HOMO, and the transition dipole moment enlarges as the number of the substitution increases. Some of the aza-substitutions dramatically affect the direction of the transition dipole, due to reduction of the molecular symmetry, which was studied in detail by a decomposition analysis of the transition dipole moment. Tetraza-substitution in chlorin and bacteriochlorin increases the oscillator strength more than that of tetrazaporphin. The mechanism underlying these changes originates mainly from the relaxation of near-degeneracy in the main configurations. These findings would be useful for the application to the molecular design of the excited states.

scholarly journals Fluorescence quantum yield rationalized by the magnitude of the charge transfer in π-conjugated terpyridine derivatives

2016 ◽  
Vol 18 (42) ◽  
pp. 29387-29394 ◽  
Author(s):  
Marie Humbert-Droz ◽  
Claude Piguet ◽  
Tomasz A. Wesolowski
Keyword(s):  
Dipole Moment ◽  
Charge Transfer ◽  
Quantum Yield ◽  
Excited States ◽  
Charge Separation ◽  
Fluorescence Quantum Yield ◽  
Molecular Design ◽  
Electron Hole ◽  
Two Measures

Two measures of charge separation in ground and excited states (length of the change in dipole moment and the electron–hole distance) provide a remarkable tool for the molecular design of a fluorescent polyaromatic antenna.

Restriction of Access to Dark State: A New Mechanistic Model for Heteroatom-Containing AIE Systems

2019 ◽  
Author(s):  
Yujie Tu ◽  
Junkai Liu ◽  
Haoke Zhang ◽  
Qian Peng ◽  
Jacky W. Y. Lam ◽  
...  
Keyword(s):  
Excited States ◽  
Radiative Decay ◽  
Molecular Design ◽  
Mechanistic Model ◽  
Zinc Ion ◽  
Easy Access ◽  
Triplet States ◽  
Dark State ◽  
Ion Probe ◽  
Π State

Aggregation-induced emission (AIE) is an unusual photophysical phenomenon and provides an effective and advantageous strategy for the design of highly emissive materials in versatile applications such as sensing, imaging, and theragnosis. "Restriction of intramolecular motion" is the well-recognized working mechanism of AIE and have guided the molecular design of most AIE materials. However, it sometimes fails to be workable to some heteroatom-containing systems. Herein, in this work, we take more than one excited state into account and specify a mechanism –"restriction of access to dark state (RADS)" – to explain the AIE effect of heteroatom-containing molecules. An anthracene-based zinc ion probe named APA is chosen as the model compound, whose weak fluorescence in solution is ascribed to the easy access from the bright (π,π*) state to the closelying dark (n,π*) state caused by the strong vibronic coupling of the two excited states. By either metal complexation or aggregation, the dark state is less accessible due to the restriction of the molecular motion leading to the dark state and elevation of the dark state energy, thus the emission of the bright state is restored. RADS is found to be powerful in elucidating the photophysics of AIE materials with excited states which favor non-radiative decay, including overlap-forbidden states such as (n,π*) and CT states, spin-forbidden triplet states, which commonly exist in heteroatom-containing molecules.

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