Intramolecular transfer of both singlet and triplet electronic excitation between the naphthalene moiety and the carbonyl group in 3β-(1-naphthyl)acetoxy-⊿~5-androsten-17-one was studied.Irradiation with 280 nm ligh...Intramolecular transfer of both singlet and triplet electronic excitation between the naphthalene moiety and the carbonyl group in 3β-(1-naphthyl)acetoxy-⊿~5-androsten-17-one was studied.Irradiation with 280 nm light selectively leads to excitation of the naphthalene moiety. Transfer of the singlet excitation from the naphthalene moiety to the carbonyl group occurs by dipole- dipole resonance interaction.The measured rates for such energy transfer in several solvents agree with that calculated from Frster equation.After efficient intersystem crossing,the carbonyl group transfers triplet excitation back to the naphthalene moiety via electron exchange mechanism.The combination of singlet and triplet energy transfer with the high efficiency of intersystcm crossing of carbonyl group results in the phosphorescence enhancement of naphthalene moiety.展开更多
The block correlated coupled cluster (BCCC) method, with the complete active-space self-consistent-field (CASSCF) reference function, has been applied to investigating the singlet-triplet gaps in several substituted c...The block correlated coupled cluster (BCCC) method, with the complete active-space self-consistent-field (CASSCF) reference function, has been applied to investigating the singlet-triplet gaps in several substituted carbenes including four halocarbenes (CHCl, CF2, CCl2, and CBr2) and two hydroxycar-benes (CHOH and C(OH)2). A comparison of our results with the experimental data and other theoretical estimates shows that the present approach can provide quantitative descriptions for all the studied carbenes. It is demonstrated that the CAS-BCCC method is a promising theoretical tool for calculating the electronic structures of diradicals.展开更多
通过Suzuki反应合成了三种基于三苯胺/二苯砜的热激活延迟荧光(TADF)材料(1–3),采用紫外-可见(UV-Vis)吸收光谱、时间分辨荧光发射光谱、循环伏安(CV)测试、理论计算、热重分析和差示扫描量热法,系统地研究了三种材料的光物理、电化学...通过Suzuki反应合成了三种基于三苯胺/二苯砜的热激活延迟荧光(TADF)材料(1–3),采用紫外-可见(UV-Vis)吸收光谱、时间分辨荧光发射光谱、循环伏安(CV)测试、理论计算、热重分析和差示扫描量热法,系统地研究了三种材料的光物理、电化学、延迟荧光性能和热稳定性.材料1–3均为基于分子内电荷转移(ICT)的双极性分子.三种材料在薄膜中的单线态-三线态能级差分别为0.46、0.39和0.29 e V.荧光量子效率和荧光寿命的测试结果表明,三种材料均能发射延迟荧光,其中材料3具有最佳的延迟荧光性能.材料1–3的最高占有分子轨道(HOMO)能级分别为–4.91、–4.89和–4.89 e V.结合UV-Vis吸收光谱中得到的能隙(Eg)值,我们得到材料1–3的最低未占分子轨道(LUMO)能级,分别为–1.74、–1.89和–1.94 e V.热分析的结果表明,材料1–3具有其较高的热分解温度(Td,失重5%时的温度),分别为436、387和310°C.展开更多
Dinitrogen activation under mild conditions is important but extremely challenging due to the inert nature of the N≡N triple bond evidenced by high bond dissociation energy(945 k J/mol) and large HOMOLUMO gap(10.8 e ...Dinitrogen activation under mild conditions is important but extremely challenging due to the inert nature of the N≡N triple bond evidenced by high bond dissociation energy(945 k J/mol) and large HOMOLUMO gap(10.8 e V). In comparison with largely developed transition metal systems, the reported main group species on dinitrogen activation are rare. Here, we carry out density functional theory calculations on methyleneboranes to understand the reaction mechanisms of their dinitrogen activation. It is found that the methyleneboranes without any substituent at the boron atom performs best on dinitrogen activation, which could be contributed to its small singlet-triplet gap. In addition, strong correlations are achieved on dinitrogen activation between the singlet-triplet energy gap and the reaction energies for the formation of the end-on products as well as the side-on ones. The principal interacting orbital analysis suggests that methyleneboranes can mimic transition metals to cleave the N≡N triple bond. Our findings could be helpful for experimental chemists aiming at dinitrogen activation by main group species.展开更多
文摘Intramolecular transfer of both singlet and triplet electronic excitation between the naphthalene moiety and the carbonyl group in 3β-(1-naphthyl)acetoxy-⊿~5-androsten-17-one was studied.Irradiation with 280 nm light selectively leads to excitation of the naphthalene moiety. Transfer of the singlet excitation from the naphthalene moiety to the carbonyl group occurs by dipole- dipole resonance interaction.The measured rates for such energy transfer in several solvents agree with that calculated from Frster equation.After efficient intersystem crossing,the carbonyl group transfers triplet excitation back to the naphthalene moiety via electron exchange mechanism.The combination of singlet and triplet energy transfer with the high efficiency of intersystcm crossing of carbonyl group results in the phosphorescence enhancement of naphthalene moiety.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 20625309 and 20433020)the National Basic Research Program (Grant No. 2004CB719901)+1 种基金the Ministry of Education of China (Grant No. NCET-04-0450) Fok Ying Tong Education Foundation (Grant No. 91014)
文摘The block correlated coupled cluster (BCCC) method, with the complete active-space self-consistent-field (CASSCF) reference function, has been applied to investigating the singlet-triplet gaps in several substituted carbenes including four halocarbenes (CHCl, CF2, CCl2, and CBr2) and two hydroxycar-benes (CHOH and C(OH)2). A comparison of our results with the experimental data and other theoretical estimates shows that the present approach can provide quantitative descriptions for all the studied carbenes. It is demonstrated that the CAS-BCCC method is a promising theoretical tool for calculating the electronic structures of diradicals.
文摘通过Suzuki反应合成了三种基于三苯胺/二苯砜的热激活延迟荧光(TADF)材料(1–3),采用紫外-可见(UV-Vis)吸收光谱、时间分辨荧光发射光谱、循环伏安(CV)测试、理论计算、热重分析和差示扫描量热法,系统地研究了三种材料的光物理、电化学、延迟荧光性能和热稳定性.材料1–3均为基于分子内电荷转移(ICT)的双极性分子.三种材料在薄膜中的单线态-三线态能级差分别为0.46、0.39和0.29 e V.荧光量子效率和荧光寿命的测试结果表明,三种材料均能发射延迟荧光,其中材料3具有最佳的延迟荧光性能.材料1–3的最高占有分子轨道(HOMO)能级分别为–4.91、–4.89和–4.89 e V.结合UV-Vis吸收光谱中得到的能隙(Eg)值,我们得到材料1–3的最低未占分子轨道(LUMO)能级,分别为–1.74、–1.89和–1.94 e V.热分析的结果表明,材料1–3具有其较高的热分解温度(Td,失重5%时的温度),分别为436、387和310°C.
基金Financial support by the National Science Foundation of China (No. 22073079)the Top-Notch Young Talents Program of China is gratefully acknowledged。
文摘Dinitrogen activation under mild conditions is important but extremely challenging due to the inert nature of the N≡N triple bond evidenced by high bond dissociation energy(945 k J/mol) and large HOMOLUMO gap(10.8 e V). In comparison with largely developed transition metal systems, the reported main group species on dinitrogen activation are rare. Here, we carry out density functional theory calculations on methyleneboranes to understand the reaction mechanisms of their dinitrogen activation. It is found that the methyleneboranes without any substituent at the boron atom performs best on dinitrogen activation, which could be contributed to its small singlet-triplet gap. In addition, strong correlations are achieved on dinitrogen activation between the singlet-triplet energy gap and the reaction energies for the formation of the end-on products as well as the side-on ones. The principal interacting orbital analysis suggests that methyleneboranes can mimic transition metals to cleave the N≡N triple bond. Our findings could be helpful for experimental chemists aiming at dinitrogen activation by main group species.
