Singlet fission(SF)offers the potential to improve the efficiency of photovoltaic devices(PVs)by harnessing high-energy photons to produce doubled photocurrents.However,progress in SF-based PVs is hindered by limited ...Singlet fission(SF)offers the potential to improve the efficiency of photovoltaic devices(PVs)by harnessing high-energy photons to produce doubled photocurrents.However,progress in SF-based PVs is hindered by limited SF materials as a result of stringent requirements for atypical energetic arrangement and high ambient stability.Here we show that excited-state antiaromaticity(ESAA)relief can be used to simultaneously regulate the energy separation between T_(1) and S_(0) and design SF-capable materials with favorable energetic conditions and excellent stability.We achieve this by facilitatingπ-electron migration between the seven-and fivemembered rings in acepleiadylene(APD),which alleviates Baird’s antiaromaticity in the T_(1) state while maintaining Hückel’s aromaticity in S_(0).This leads to a lowered T_(1)’s energy relative to S_(0).Aromaticity index calculations reveal the aromaticity reversal and electron density redistribution between S_(0) and T_(1) to mitigate ESAA.This results in an energetic relationship suitable for SF,enabling a rapid fission process with an impressive yield of 165%.Moreover,ESAA relief endows APD with superior stability under ambient conditions.Our work not only introduces a new SF scaffold based on nonbenzenoid hydrocarbons,but it also provides valuable insights for the design of stable SF-active materials.展开更多
Nonbenzenoid polycyclic arenes have attracted great attention because of their unique topological structures and appealing properties;however,they are generally considered as poor luminescent materials due to the ring...Nonbenzenoid polycyclic arenes have attracted great attention because of their unique topological structures and appealing properties;however,they are generally considered as poor luminescent materials due to the ring puckering behavior of the nonhexagons.Acepleiadylene(APD),a nonbenzenoid isomer of pyrene,has been demonstrated as an excellent building block for optoelectronic applications,but its poor photoluminescence quantum yield(PLQY)has hampered its application in luminescent materials.Considering that the ring puckering character can be suppressed by increasing the rigidity of the nonhexagon rings,herein,we propose a novel strategy for enhancing the aromaticity of the nonhexagons to improve the PLQYs of APD derivatives.Electron-withdrawing cyano groups are introduced on the five-membered ring of APD to enhance the chargeseparated character and thus the aromaticity of the nonhexagons,endowing the cyano-substituted APDs(CNAPD and 2CNAPD)with better rigidity.Therefore,the cyano substitution successfully suppresses the nonradiative energy dissipation caused by the ring puckering,improving the PLQY from 2.4%for APD to 14%for CNAPD,and to 63%for 2CNAPD.In addition,the enhanced rigidity also suppresses the vibration sideband of the photoluminescence spectra,leading to an ultra-narrowband emission from 2CNAPD with a full-width at half-maximum(FWHM)of 13 nm(47 me V),which is a new record in organic molecules.These results demonstrate that APD derivatives have great potential in highly efficient luminescent materials with high color purity via the aromaticity regulation strategy,which provides a novel concept for designing nonbenzenoid luminescent materials.展开更多
Azulene, one of representative nonbenzenoid aromatic hydrocarbons, exhibits unique molecular structure and distinctive physical and chemical properties. Herein, azulenoisoindigo(Az II), an azulene-based isoindigo anal...Azulene, one of representative nonbenzenoid aromatic hydrocarbons, exhibits unique molecular structure and distinctive physical and chemical properties. Herein, azulenoisoindigo(Az II), an azulene-based isoindigo analogue, is designed and synthesized, which has a twisted molecular backbone and R/Sisomers in single crystals. Interestingly, Az II shows the characteristics of both isoindigo and azulene,such as reversible redox behavior and reversible proton responsiveness. UV-vis-NIR,^(1)H NMR and electron paramagnetic resonance(EPR) measurements were carried out to get insights into the possible mechanism of the proton-responsive property of Az II. The results demonstrated that only one azulenyl moiety of molecule of Az II was protonated and deprotonated, and the protonated Az II can be further oxidized to form azulenium cation radicals.展开更多
基金supported by the National Natural Science Foundation of China(grant nos.22173062,21833005,22090022,and 22275125)the Beijing Natural Science Foundation of China(grant nos.Z230019 and 2212005)the Youth Innovative Research Team of Capital Normal University.
文摘Singlet fission(SF)offers the potential to improve the efficiency of photovoltaic devices(PVs)by harnessing high-energy photons to produce doubled photocurrents.However,progress in SF-based PVs is hindered by limited SF materials as a result of stringent requirements for atypical energetic arrangement and high ambient stability.Here we show that excited-state antiaromaticity(ESAA)relief can be used to simultaneously regulate the energy separation between T_(1) and S_(0) and design SF-capable materials with favorable energetic conditions and excellent stability.We achieve this by facilitatingπ-electron migration between the seven-and fivemembered rings in acepleiadylene(APD),which alleviates Baird’s antiaromaticity in the T_(1) state while maintaining Hückel’s aromaticity in S_(0).This leads to a lowered T_(1)’s energy relative to S_(0).Aromaticity index calculations reveal the aromaticity reversal and electron density redistribution between S_(0) and T_(1) to mitigate ESAA.This results in an energetic relationship suitable for SF,enabling a rapid fission process with an impressive yield of 165%.Moreover,ESAA relief endows APD with superior stability under ambient conditions.Our work not only introduces a new SF scaffold based on nonbenzenoid hydrocarbons,but it also provides valuable insights for the design of stable SF-active materials.
基金supported by the National Natural Science Foundation of China (22071120,92256304,22221002)the National Key R&D Program of China (2020YFA0711500)the Fundamental Research Funds for the Central Universities。
文摘Nonbenzenoid polycyclic arenes have attracted great attention because of their unique topological structures and appealing properties;however,they are generally considered as poor luminescent materials due to the ring puckering behavior of the nonhexagons.Acepleiadylene(APD),a nonbenzenoid isomer of pyrene,has been demonstrated as an excellent building block for optoelectronic applications,but its poor photoluminescence quantum yield(PLQY)has hampered its application in luminescent materials.Considering that the ring puckering character can be suppressed by increasing the rigidity of the nonhexagon rings,herein,we propose a novel strategy for enhancing the aromaticity of the nonhexagons to improve the PLQYs of APD derivatives.Electron-withdrawing cyano groups are introduced on the five-membered ring of APD to enhance the chargeseparated character and thus the aromaticity of the nonhexagons,endowing the cyano-substituted APDs(CNAPD and 2CNAPD)with better rigidity.Therefore,the cyano substitution successfully suppresses the nonradiative energy dissipation caused by the ring puckering,improving the PLQY from 2.4%for APD to 14%for CNAPD,and to 63%for 2CNAPD.In addition,the enhanced rigidity also suppresses the vibration sideband of the photoluminescence spectra,leading to an ultra-narrowband emission from 2CNAPD with a full-width at half-maximum(FWHM)of 13 nm(47 me V),which is a new record in organic molecules.These results demonstrate that APD derivatives have great potential in highly efficient luminescent materials with high color purity via the aromaticity regulation strategy,which provides a novel concept for designing nonbenzenoid luminescent materials.
基金financially supported by the National Natural Science Foundation of China (Nos. 21790362, 22075310 and21522209)the “Strategic Priority Research Program of Chinese Academy of Sciences”(No. XDB12010100)+1 种基金the Science and Technology Commission of Shanghai Municipality (Nos. 19XD1424700 and18JC1410600)SIOC. An early preprint of this work appeared on Chem Rxiv [47]。
文摘Azulene, one of representative nonbenzenoid aromatic hydrocarbons, exhibits unique molecular structure and distinctive physical and chemical properties. Herein, azulenoisoindigo(Az II), an azulene-based isoindigo analogue, is designed and synthesized, which has a twisted molecular backbone and R/Sisomers in single crystals. Interestingly, Az II shows the characteristics of both isoindigo and azulene,such as reversible redox behavior and reversible proton responsiveness. UV-vis-NIR,^(1)H NMR and electron paramagnetic resonance(EPR) measurements were carried out to get insights into the possible mechanism of the proton-responsive property of Az II. The results demonstrated that only one azulenyl moiety of molecule of Az II was protonated and deprotonated, and the protonated Az II can be further oxidized to form azulenium cation radicals.
