Two o-carboranyl compounds containing 1,2,4-triazole groups,each appended with an N-aryl ring(either N-phenyl or N-diisopropylphenyl),were strategically designed and prepared to elucidate the relationship between thei...Two o-carboranyl compounds containing 1,2,4-triazole groups,each appended with an N-aryl ring(either N-phenyl or N-diisopropylphenyl),were strategically designed and prepared to elucidate the relationship between their structural orientation(planarity)and intramolecular charge transfer(ICT)-based radiative decay.The photophysical analysis of both compounds shows that the N-phenyl appended com-pound shows a much higher quantum yield and larger radiative decay constant for ICT-based emission in the rigid state(solution at 77 K and film)than those of the N-diisopropylphenyl appended compound,even exhibiting an additional ICT-based emission in solution at 298 K.Theoretical calculations on their ground and excited states indicate that the planarity of the N-aryl appended triazole moiety affects the efficiency of radiative decay for the ICT transition.These findings firmly establish a strong relationship between the planarity of the appended aryl groups relative to the triazole ring and ICT-based radiative decay in these o-carboranyl luminophores.展开更多
Herein,we compared the optical properties of four compounds with an o-carborane cage linked to 1H-phenanthro[9,10-d]imidazole at the ortho-(oPC),meta-(mPC),or para-position(pPC)of the 2-phenyl ring or at the C2-positi...Herein,we compared the optical properties of four compounds with an o-carborane cage linked to 1H-phenanthro[9,10-d]imidazole at the ortho-(oPC),meta-(mPC),or para-position(pPC)of the 2-phenyl ring or at the C2-position(PC)of the phenanthroimidazole moiety.In the solid state,pPC and PC exhibited intense intramolecular charge transfer(ICT)-based emission centred at∼560 nm,while oPC and mPC exhibited dual emission in high-energy(λ_(em)≈385 nm)and low-energy(λ_(em)≈580 nm)regions due to a locally excited transition and ICT-based emission,respectively.Thus,the quantum efficiency and radiative decay constant of ICT-based emission in the film state were much higher for pPC and PC than for oPC and mPC.Analysis of solid-state molecular structure revealed a notable geometric difference between these two pairs,showing that the C-C bond axis of the o-carborane was orthogonal to the plane of the appended aromatic group for pPC and PC but not for oPC and mPC.Theoretical modelling of the low-energy transition in the first excited states of pPC and PC upon the rotation of the o-carborane cage verified that the above orthogonality plays an important role in the maximisation of ICT-based luminescence.Our findings suggest that the molecular geometry around the o-carborane cage is a major factor determining the efficiency of ICT-based radiative decay in o-carboranyl-substitutedπ-conjugated fluorophores.展开更多
Three closo-o-carborane-functionalised pyrene compounds(1CB,2CB,and 4CB)were synthesised and fully characterised.The molecular structures of all compounds exhibited perpendicularity between the C-C bond of the o-carbo...Three closo-o-carborane-functionalised pyrene compounds(1CB,2CB,and 4CB)were synthesised and fully characterised.The molecular structures of all compounds exhibited perpendicularity between the C-C bond of the o-carborane and the pyrene groups.The three compounds displayed major absorption bands assignable to π-π*transitions within the pyrene group,as well as weak intramolecular chargetransfer(ICT)transitions between the o-carborane units and the pyrene moieties.While 1CB and 4CB displayed strong ICT-based emissions involving the o-carborane moiety(λ_(em)=500-700 nm)in THF at 298 K,2CB showed less intense LE-based emissions centred at λ_(em)=407 nm.Although the PL spectra of all compounds demonstrated enhanced ICT-based emission via inhibition of C-C bond variance within the o-carborane in rigid states(THF at 77 K and films),the quantum efficiency of 2CB in films(Φ_(em)=5%)did not significantly increase compared to that in THF at 298 K,while the values for 1CB and 4CB in films were dramatically enhanced to 75%and 62%,respectively.The radiative decay constants of each ICTbased emission showed that non-radiative decay processes were significantly larger for 2CB than in 1CB and 4CB.The relative energies of the various S0 conformations as the dihedral angle between the o-carborane cage and pyrene unit was changed indicated that the o-carborane cages in 2CB could rotate more easily than those in 1CB and 4CB.Furthermore,the involvement of the o-carborane moiety in the LUMO level of 2CB was significantly affected by this dihedral angle.These results suggest that the free rotation of the o-carborane cage of 2CB interrupted its ICT transitions,with experimental and theoretical findings confirming that large structural variations around the o-carborane cage for 2CB also induced ICT-based non-radiative decay processes associated with the o-carborane,further blocking the ICT transition itself.展开更多
基金supported by the National Research Foundation of Korea(NRF)grant(NRF-2020R1A2C1006400 and NRF-2016M3A7B4909246 for K.M.Lee and 2020R1I1A1A01073381 for J.H.Lee)funded by the Ministry of Science and ICT and the Ministry of Education.
文摘Two o-carboranyl compounds containing 1,2,4-triazole groups,each appended with an N-aryl ring(either N-phenyl or N-diisopropylphenyl),were strategically designed and prepared to elucidate the relationship between their structural orientation(planarity)and intramolecular charge transfer(ICT)-based radiative decay.The photophysical analysis of both compounds shows that the N-phenyl appended com-pound shows a much higher quantum yield and larger radiative decay constant for ICT-based emission in the rigid state(solution at 77 K and film)than those of the N-diisopropylphenyl appended compound,even exhibiting an additional ICT-based emission in solution at 298 K.Theoretical calculations on their ground and excited states indicate that the planarity of the N-aryl appended triazole moiety affects the efficiency of radiative decay for the ICT transition.These findings firmly establish a strong relationship between the planarity of the appended aryl groups relative to the triazole ring and ICT-based radiative decay in these o-carboranyl luminophores.
基金supported by the National Research Foundation of Korea(NRF)grant(NRF-2020R1A2C1006400 and NRF-2021M3H4A1A02055684 for K.M.Lee)funded by the Ministry of Science and ICT.
文摘Herein,we compared the optical properties of four compounds with an o-carborane cage linked to 1H-phenanthro[9,10-d]imidazole at the ortho-(oPC),meta-(mPC),or para-position(pPC)of the 2-phenyl ring or at the C2-position(PC)of the phenanthroimidazole moiety.In the solid state,pPC and PC exhibited intense intramolecular charge transfer(ICT)-based emission centred at∼560 nm,while oPC and mPC exhibited dual emission in high-energy(λ_(em)≈385 nm)and low-energy(λ_(em)≈580 nm)regions due to a locally excited transition and ICT-based emission,respectively.Thus,the quantum efficiency and radiative decay constant of ICT-based emission in the film state were much higher for pPC and PC than for oPC and mPC.Analysis of solid-state molecular structure revealed a notable geometric difference between these two pairs,showing that the C-C bond axis of the o-carborane was orthogonal to the plane of the appended aromatic group for pPC and PC but not for oPC and mPC.Theoretical modelling of the low-energy transition in the first excited states of pPC and PC upon the rotation of the o-carborane cage verified that the above orthogonality plays an important role in the maximisation of ICT-based luminescence.Our findings suggest that the molecular geometry around the o-carborane cage is a major factor determining the efficiency of ICT-based radiative decay in o-carboranyl-substitutedπ-conjugated fluorophores.
基金supported by the National Research Foundation of Korea(NRF)grant(2019R1A2C1009969 for M.H.Park,2020R1I1A1A01073381 for J.H.LeeNRF-2020R1A2C1006400 and NRF-2016M3A7B4909246 for K.M.Lee)funded by the Ministry of Science and ICT,and the Ministry of Education.
文摘Three closo-o-carborane-functionalised pyrene compounds(1CB,2CB,and 4CB)were synthesised and fully characterised.The molecular structures of all compounds exhibited perpendicularity between the C-C bond of the o-carborane and the pyrene groups.The three compounds displayed major absorption bands assignable to π-π*transitions within the pyrene group,as well as weak intramolecular chargetransfer(ICT)transitions between the o-carborane units and the pyrene moieties.While 1CB and 4CB displayed strong ICT-based emissions involving the o-carborane moiety(λ_(em)=500-700 nm)in THF at 298 K,2CB showed less intense LE-based emissions centred at λ_(em)=407 nm.Although the PL spectra of all compounds demonstrated enhanced ICT-based emission via inhibition of C-C bond variance within the o-carborane in rigid states(THF at 77 K and films),the quantum efficiency of 2CB in films(Φ_(em)=5%)did not significantly increase compared to that in THF at 298 K,while the values for 1CB and 4CB in films were dramatically enhanced to 75%and 62%,respectively.The radiative decay constants of each ICTbased emission showed that non-radiative decay processes were significantly larger for 2CB than in 1CB and 4CB.The relative energies of the various S0 conformations as the dihedral angle between the o-carborane cage and pyrene unit was changed indicated that the o-carborane cages in 2CB could rotate more easily than those in 1CB and 4CB.Furthermore,the involvement of the o-carborane moiety in the LUMO level of 2CB was significantly affected by this dihedral angle.These results suggest that the free rotation of the o-carborane cage of 2CB interrupted its ICT transitions,with experimental and theoretical findings confirming that large structural variations around the o-carborane cage for 2CB also induced ICT-based non-radiative decay processes associated with the o-carborane,further blocking the ICT transition itself.
