A density functional theory investigation of the stability,aromaticity, and photophysical behavior for the highly conjugated macrocycles containing 4 pyrroles |
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Authors: | Wei Wei Fu‐Quan Bai Bao‐Hui Xia Jian Wang Hong‐Xing Zhang |
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Institution: | 1. International Joint Research Laboratory of Nano‐Micro Architecture Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun, China;2. College of Chemistry, Jilin University, Changchun, China |
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Abstract: | Porphyrin ( Pr ), porphycene ( Pc ), and 22]porphyrin(2.2.2.2) ( P22] ) have been theoretically investigated. We design 2 highly conjugated macrocycles containing 4 pyrroles with different linkage bridges, which are named for 4 pyrrole ( Pf ) and methylene‐dipyrrolidine ( Pm ), as the theoretical model so as to investigate the stability, aromaticity, and photophysical behavior of these porphyrin derivatives, and the influence of getting or losing electron to the neutral molecule. The geometric structures of the molecules are optimized by density functional theory method. The absorptions are calculated by the time‐dependent density functional theory method. Based on the optimized structures, the nucleus‐independent chemical shifts (NICS) are calculated. The molecule with negative NICS value possesses larger highest occupied molecular orbital (HOMO)‐lowest occupied molecular orbital (LUMO) gap than that with positive NICS value, the molecule with bigger positive NICS value possesses smaller HOMO‐LUMO gap, and the molecule with bigger negative NICS value (in absolute value) possesses bigger HOMO‐LUMO gap. The current density indicates that the π‐electron delocalization is more effective in Pr and Pc than in Pf , Pm , and P22] and corresponds to the stability of molecules. The absorptions of the molecules are all in the UV‐visible and infrared regions. The major transitions for most of the molecules are all from HOMO to LUMO. Compared with Pf 2? , Pr 2? , Pc 2? , and P22] 2? , Pm 2? shows distinctive photophysical properties, which is due to the reduced HOMO‐LUMO gap, structural distortion, and strong antiaromaticity. |
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Keywords: | aromaticity photophysical behavior porphyrin derivatives stability |
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