The excited state intramolecular proton transfer （ESIPT） coupled charge transfer of baicalein has been investigated using steady-state spectroscopic experiment and quantum chemistry calculations. The absence of the ...The excited state intramolecular proton transfer （ESIPT） coupled charge transfer of baicalein has been investigated using steady-state spectroscopic experiment and quantum chemistry calculations. The absence of the absorption peak from S1 excited state both in the experi-mental and calculated absorption spectra indicates that S1 is a dark state. The dark excited state S1 results in the very weak fluorescence of solid baicalein in the experiment. The fron- tier molecular orbital and the charge difference densities of baicalein show clearly that the S1 state is a charge-transfer state whereas the S2 state is a locally excited state. The only one stationary point on the potential energy profile of excited state suggests that the ESIPT reaction of baicalein is a barrierless process.展开更多
The intramolecular charge transfer dual fluorescence of p-dibutylaminobenzoic acid-b-cyclodextrin inclusion complex showed a substantially higher sensitivity toward aqueous solution pH variation when compared with tha...The intramolecular charge transfer dual fluorescence of p-dibutylaminobenzoic acid-b-cyclodextrin inclusion complex showed a substantially higher sensitivity toward aqueous solution pH variation when compared with that of p-dibutylaminobenzoic acid alone, which established a new principle for direct CT fluorescence sensing in aqueous solution by using the CT fluorophore-cyclodextrin inclusion complex.展开更多
Pentaerythrityl tetra(p-dimethylaminobenzoate) (PTDMAB) was synthesized and shown to emit in water-rich aqueous dioxane solutions the intramolecular charge transfer fluorescence that was sensitive to the presence of m...Pentaerythrityl tetra(p-dimethylaminobenzoate) (PTDMAB) was synthesized and shown to emit in water-rich aqueous dioxane solutions the intramolecular charge transfer fluorescence that was sensitive to the presence of metal ions.展开更多
Density functional theory and time-dependent density-functional theory have been used to investigate the photophysical properties and relaxation dynamics of dimethylaminobenzophe- none （DMABP） and its hydrogen-bonde...Density functional theory and time-dependent density-functional theory have been used to investigate the photophysical properties and relaxation dynamics of dimethylaminobenzophe- none （DMABP） and its hydrogen-bonded DMABP-MeOH dimer. It is found that, in non- polar aprotic solvent, the transitions from So to S1 and S2 states of DMABP have both n→π and π→π＊ characters, with the locally excited feature mainly located on the C=O group and the partial CT one characterized by electron transfer mainly from the dimethylaminophenyl group to the C=O group. But when the intermolecular hydrogen bond C=O…H-O is formed, the highly polar intramolecular charge transfer character switches over to the first excited state of DMABP-MeOH dimer and the energy difference between the two low- lying electronically excited states increases. To gain insight into the relaxation dynamics of DMABP and DMABP-MeOH dimer in the excited state, the potential energy curves for con- formational relaxation are calculated. The formation of twisted intramolecular charge trans- fer state via diffusive twisting motion of the dimethylamino/dimethylaminophenyl groups is found to be the major relaxation process. In addition, the decay of the Si state of DMABP-MeOH dimer to the ground state, through nonradiative intermolecular hydrogen bond stretching vibrations, is facilitated by the formation of the hydrogen bond between DMABP and alcohols.展开更多
The ground and excited state properties of the [60]fullerene, diphenylbenzothiadiazole-triphenylamine （PBTDP-TPA） dyad and fullerene-diphenylbenzothiadiazole-triphenylamine （fullerene-PBTDP-TPA） triad were investi...The ground and excited state properties of the [60]fullerene, diphenylbenzothiadiazole-triphenylamine （PBTDP-TPA） dyad and fullerene-diphenylbenzothiadiazole-triphenylamine （fullerene-PBTDP-TPA） triad were investigated theoretically using density functional theory with B3LYP functional and 3-21G basis set and time-dependent density functional theory with B3LYP functional and STO-3G basis set as well as 2D and 3D real space analysis methods. The 2D site representation reveals the electron-hole coherence on excitation. The 3D transition density shows the orientation and strength of the transition dipole moment, and the 3D charge difference density gives the orientation and result of the intramolecular charge transfer. Also photoinduced intermolecular charge transfer （ICT） in PBTDP-TPA-fullerene triad are identified with 2D and 3D representations, which reveals the mechanisms of ICT in donor-bridge-acceptor triad on excitation. Besides that we also found that the direct superexchange ICT from donor to acceptor （tunneling through the bridge） strongly promotes the ICT in the donor-bridge-acceptor triad.展开更多
Partial genetically encoded 4-hy-droxybenzylidene-imidazolinone(HBI)-type chromophores are new promising fluorescent probes,which are suitable for imaging and detection of living cells.How-ever,the lack of infrared ch...Partial genetically encoded 4-hy-droxybenzylidene-imidazolinone(HBI)-type chromophores are new promising fluorescent probes,which are suitable for imaging and detection of living cells.How-ever,the lack of infrared chro-mophores hinders the develop-ment seriously.Here more than 30 HBI-type chromophores with reg-ular structure modifications were employed and typical spectral redshift change laws and mechanisms were investigated by quantum methods.Results show that both one-photon spectrum(OPS,absorption/emission)and two-photon absorption(TPA)can achieve large redshift via either extending conjugated lengths of frag-3 or enlarging conjugated areas of frag-1 of HBI skeleton.Spectral redshifts of all chromophores are highly related to intramolecular charge transfer(ICT),but neutral ones are closely related to the total ICT or electron-accept-ing-numbers of frag-3,and the high correlative factor of anions is the aromaticity of frag-2 bridge.The frag-2 bridge with high aromaticity can open a reverse charge transfer channel in anion relative to neutral,obtaining significant redshift.Based on analysis,a new 6-hydroxyl-naphthalene-imidazolinone(HNI)series,which have larger conjugated area in frag-1,are pre-dicted.The OPS and TPA of anionic HNI ones acquire about 76−96 nm and 119−146 nm red-shift relative to traditional HBI series respectively as a whole.The longest emission of anionic HNI-4 realizes more 244 nm redshift relative to HBI-1.Our work clarifies worthy spectral reg-ularities and redshift mechanisms of HBI-type chromophores and provides valuable design strategy for infrared chromophores synthesis in experiment.展开更多
In this work, the optical properties of fluorescent probes used for detection of biothiol were studied by employing time-dependent density functional theory. By calculating the single photon absorption and emission pr...In this work, the optical properties of fluorescent probes used for detection of biothiol were studied by employing time-dependent density functional theory. By calculating the single photon absorption and emission properties of probe Mol.1, Mol.2 and Mol.3 before and after reaction with cysteine and homocysteine, we have investigated the effect of carboncarbon triple bond and benzene ring on the properties of fluorescent probes. It is found that the oscillator strength of probe molecules increases gradually with the improvement of the structure of the electron donor triphenylamine and the addition of carbon-carbon triple bonds, and better properties of fluorescence probes have also been demonstrated. At the same time, the effect of different number of side branches on the molecular properties of the probe was also studied. The results showed that compared with single-branched molecule Z1 and tribranched probe Mol.3, two side probe molecules Z2 had higher oscillator strength and better detection effect. In addition, the new single-branched probe Mol.4 with the addition of carbon-carbon triple bonds and benzene rings has better probe properties and simpler structure than the tribranched probe Mol.3.展开更多
Polydimethylsilylenes bearing pyrenyl groups exhibit emissions fromtwisted intramolecular charge transfer state between the aromatic ring and thesilicon backbone both in polar and nonpolar solvents.
In this paper the results of dynamic NMR studies on ethylmethylamino-tertiary-butyl-phenylborane (EMABPB) with or without light are reported. The NMR data were recorded on a Bruker 400 MHz NMR equipped with our custom...In this paper the results of dynamic NMR studies on ethylmethylamino-tertiary-butyl-phenylborane (EMABPB) with or without light are reported. The NMR data were recorded on a Bruker 400 MHz NMR equipped with our custom-made optical probe and with our custom-made 450 watts (W) monochromatic light sources. The molecular photochemistry including twisted intramolecular charge-transfer-excited-state (TICT) of the EMABPB in several solvents has been investigated. These results indicate that the aminoborane demonstrates multiple configurations in CD3Cl and CD2Cl2 resulting in the shifts of the signals of the alkyl groups on the nitrogen and boron. This indicates that there are some time-dependent changes at constant temperature over the irradiation interval. At ﹣60°C and the presence of light (λ = 265 nm), we observed a large change in the populations of the two sites, and this by itself indicates a modification in the rotation around the boron nitrogen bond in the excited state. By considering the existence of the TICT state, many important energy technologies may be developed with higher efficiency by controlling the back-electron transfer processes.展开更多
We theoretically investigate the excited state intramolecular proton transfer(ESIPT) behavior of the novel fluorophore bis-imine derivative molecule HNP which was designed based on the intersection of 1-(hydrazonometh...We theoretically investigate the excited state intramolecular proton transfer(ESIPT) behavior of the novel fluorophore bis-imine derivative molecule HNP which was designed based on the intersection of 1-(hydrazonomethyl)-naphthalene-2-ol and 1-pyrenecarboxaldehyde. Especially, the density functional theory(DFT) and time-dependent density functional theory(TDDFT) methods for HNP monomer are introduced. Moreover, the "our own n-layered integrated molecular orbital and molecular mechanics"(ONIOM) method(TDDFT:universal force field(UFF)) is used to reveal the aggregation-induced emission(AIE) effect on the ESIPT process for HNP in crystal. Our results confirm that the ESIPT process happens upon the photoexcitation for the HNP monomer and HNP in crystal, which is distinctly monitored by the optimized geometric structures and the potential energy curves. In addition, the results of potential energy curves reveal that the ESIPT process in HNP will be promoted by the AIE effect. Furthermore, the highest occupied molecular orbital(HOMO) and lowest unoccupied molecular orbital(LUMO) for the HNP monomer and HNP in crystal have been calculated. The calculation demonstrates that the electron density decrease of proton donor caused by excitation promotes the ESIPT process. In addition, we find that the variation of atomic dipole moment corrected Hirshfeld population(ADCH) charge for proton acceptor induced by the AIE effect facilitates the ESIPT process. The results will be expected to deepen the understanding of ESIPT dynamics for luminophore under the AIE effect and provide insight into future design of high-efficient AIE compounds.展开更多
Time-dependent density functional theory(TDDFT)method is used to investigate the details of the excited state intramolecular proton transfer(ESIPT)process and the mechanism for temperature effect on the Enol^(*)/Keto^...Time-dependent density functional theory(TDDFT)method is used to investigate the details of the excited state intramolecular proton transfer(ESIPT)process and the mechanism for temperature effect on the Enol^(*)/Keto^(*)emission ratio for the Me_(2)N-substited flavonoid(MNF)compound.The geometric structures of the S_(0) and S_(1) states are denoted as the Enol,Enol^(*),and Keto*.In addition,the absorption and fluorescence peaks are also calculated.It is noted that the calculated large Stokes shift is in good agreement with the experimental result.Furthermore,our results confirm that the ESIPT process happens upon photoexcitation,which is distinctly monitored by the formation and disappearance of the characteristic peaks of infrared(IR)spectra involved in the proton transfer and in the potential energy curves.Besides,the calculations of highest occupied molecular orbital(HOMO)and lowest unoccupied molecular orbital(LUMO)reveal that the electronegativity change of proton acceptor due to the intramolecular charge redistribution in the S_(1) state induces the ESIPT.Moreover,the thermodynamic calculation for the MNF shows that the Enol^(*)/Keto^(*)emission ratio decreasing with temperature increasing arises from the barrier lowering of ESIPT.展开更多
β-cyclodextrin (β-CD) induced aggregation and micelle formation of cetyltrimethylam-mnium broAnde (CTMAB) in aqueous solution is demonstrated by the dual fluorescence of p-N, N-dAnethyladrinobenzoic acid (DMABOA) ty...β-cyclodextrin (β-CD) induced aggregation and micelle formation of cetyltrimethylam-mnium broAnde (CTMAB) in aqueous solution is demonstrated by the dual fluorescence of p-N, N-dAnethyladrinobenzoic acid (DMABOA) typical of the twisted intramolecular charge transfer (TICT). The locally excited (LE) state of DMABOA is proved to have the characteristic of intramolecular charge transfer (ICT) with a polarity higher than that of ground state but lower than that of TICT state. The peak positions of the two fluorescence bands and theiI intensity ratio are employed to probe the interaction of β-CD with CTMAB. It is conc1uded that β-CD induces CTMAB aggregation as well as Ancelle formation and may change Ancelle structure. The results also indicate that TICT in aqueous solution may be affected by the anisotropy or viscosity of the medium,increasing viscosity disadvantaging the TICT process.展开更多
Two new diarylamine-substituted 1, 8-naphthalimide derivatives are synthesized by Cu I/18-crown-6/K2CO3 catalyst system and characterized by Fourier transform infrared （FT- IR）, ^1H-NMR and elemental analyses. The U...Two new diarylamine-substituted 1, 8-naphthalimide derivatives are synthesized by Cu I/18-crown-6/K2CO3 catalyst system and characterized by Fourier transform infrared （FT- IR）, ^1H-NMR and elemental analyses. The UV-vis absorption and photoluminescent （PL）spectra of the systems in n-hexane, tetrahydrofuran（THF）, and CH2Cl2 are investigated. These naphthalimide molecules have an absorption band centered at about 450 nm, which is assigned to an intramolecular chargetransfer （ICT）transition, and they emit light at 492, 501 nm in a nonpolar solvent such as n-hexane, and at 600, 620 nm in a polar solvent such as CH2Cl2. From the Lippert-Mataga equation, the difference of the dipole moment between the excited state and the ground state is estimated to be 9.2 and 9.8 D for 4- （ diphenylamine ）-N-（ 2-methoxyphenyl ）-1, 8-naphthalimide （ DMN-1 ） and 4-（ 2-naphthylphenylamine ）-N-（ 2- methoxyphenyl）-1, 8-naphthalimide （DMN-2）, respectively. This large change in the dipole moment upon excitation is typical for photoinduced ICT processes.展开更多
The donor–acceptor(D–A)copolymers,which exhibit wide broad absorption and intensified light-harvesting,are highly captivating for applications in solar conversion and optoelectronics.However,designing a polymer stru...The donor–acceptor(D–A)copolymers,which exhibit wide broad absorption and intensified light-harvesting,are highly captivating for applications in solar conversion and optoelectronics.However,designing a polymer structure that can achieve these photophysical properties simultaneously remains a challenge.Herein,we report two novel cyanated units 4-cyanobenzo[1,2-b:6,5-b′:3,4-c″]trithiophene(CBT)and 4,6-dicyanobenzo[1,2-b:6,5-b′:3,4-c″]trithiophene(C2BT)and their corresponding polymers,PCBT and PC2BT.Very interestingly,the PC2BT exhibited a broad absorption band with full width at half maxima(FWHM)of its absorption spectra,almost twice wider than PCBT and benchmark polymers PM6 and D18.Moreover,the PC2BT demonstrated intensified light-harvesting and long-lived exciton.Our in-depth investigation unveiled that the presence of dicyano substitutions induced a strong intramolecular charge transfer(ICT),which,in turn,resulted in the formation of favorable photophysical properties.Therefore,PC2BT-based polymer solar cells(PSCs)exhibited an efficiency of 18.06%,which was a record-setting efficiency for cyanated polymers.This study suggests an efficient strategy for enhancing ICT to design polymers toward favorable photophysical properties and excellent photovoltaic performance.展开更多
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.61137005 and No.10974023）, the Program for Liaoning Excellent Talents in University （No.LJQ2012002）, and the Program for New Century Excellent Talents in University （No.NCET-12-0077）.
文摘The excited state intramolecular proton transfer （ESIPT） coupled charge transfer of baicalein has been investigated using steady-state spectroscopic experiment and quantum chemistry calculations. The absence of the absorption peak from S1 excited state both in the experi-mental and calculated absorption spectra indicates that S1 is a dark state. The dark excited state S1 results in the very weak fluorescence of solid baicalein in the experiment. The fron- tier molecular orbital and the charge difference densities of baicalein show clearly that the S1 state is a charge-transfer state whereas the S2 state is a locally excited state. The only one stationary point on the potential energy profile of excited state suggests that the ESIPT reaction of baicalein is a barrierless process.
基金This work was support by NNSF of China through grants No.29975023 and No.20175020.
文摘The intramolecular charge transfer dual fluorescence of p-dibutylaminobenzoic acid-b-cyclodextrin inclusion complex showed a substantially higher sensitivity toward aqueous solution pH variation when compared with that of p-dibutylaminobenzoic acid alone, which established a new principle for direct CT fluorescence sensing in aqueous solution by using the CT fluorophore-cyclodextrin inclusion complex.
文摘Pentaerythrityl tetra(p-dimethylaminobenzoate) (PTDMAB) was synthesized and shown to emit in water-rich aqueous dioxane solutions the intramolecular charge transfer fluorescence that was sensitive to the presence of metal ions.
文摘Density functional theory and time-dependent density-functional theory have been used to investigate the photophysical properties and relaxation dynamics of dimethylaminobenzophe- none （DMABP） and its hydrogen-bonded DMABP-MeOH dimer. It is found that, in non- polar aprotic solvent, the transitions from So to S1 and S2 states of DMABP have both n→π and π→π＊ characters, with the locally excited feature mainly located on the C=O group and the partial CT one characterized by electron transfer mainly from the dimethylaminophenyl group to the C=O group. But when the intermolecular hydrogen bond C=O…H-O is formed, the highly polar intramolecular charge transfer character switches over to the first excited state of DMABP-MeOH dimer and the energy difference between the two low- lying electronically excited states increases. To gain insight into the relaxation dynamics of DMABP and DMABP-MeOH dimer in the excited state, the potential energy curves for con- formational relaxation are calculated. The formation of twisted intramolecular charge trans- fer state via diffusive twisting motion of the dimethylamino/dimethylaminophenyl groups is found to be the major relaxation process. In addition, the decay of the Si state of DMABP-MeOH dimer to the ground state, through nonradiative intermolecular hydrogen bond stretching vibrations, is facilitated by the formation of the hydrogen bond between DMABP and alcohols.
基金This work was supported by the National Natural Science Foundation of China （No.10374040, No.20703064, and No.10505001） and the Postdoctoral Science Foundation of China （No.20060390017）.
文摘The ground and excited state properties of the [60]fullerene, diphenylbenzothiadiazole-triphenylamine （PBTDP-TPA） dyad and fullerene-diphenylbenzothiadiazole-triphenylamine （fullerene-PBTDP-TPA） triad were investigated theoretically using density functional theory with B3LYP functional and 3-21G basis set and time-dependent density functional theory with B3LYP functional and STO-3G basis set as well as 2D and 3D real space analysis methods. The 2D site representation reveals the electron-hole coherence on excitation. The 3D transition density shows the orientation and strength of the transition dipole moment, and the 3D charge difference density gives the orientation and result of the intramolecular charge transfer. Also photoinduced intermolecular charge transfer （ICT） in PBTDP-TPA-fullerene triad are identified with 2D and 3D representations, which reveals the mechanisms of ICT in donor-bridge-acceptor triad on excitation. Besides that we also found that the direct superexchange ICT from donor to acceptor （tunneling through the bridge） strongly promotes the ICT in the donor-bridge-acceptor triad.
基金supported by the National Natural Sci-ence Foundation of China(No.U1904196,No.82073699)the Natural Science Foundation of Henan(No.222300420055).
文摘Partial genetically encoded 4-hy-droxybenzylidene-imidazolinone(HBI)-type chromophores are new promising fluorescent probes,which are suitable for imaging and detection of living cells.How-ever,the lack of infrared chro-mophores hinders the develop-ment seriously.Here more than 30 HBI-type chromophores with reg-ular structure modifications were employed and typical spectral redshift change laws and mechanisms were investigated by quantum methods.Results show that both one-photon spectrum(OPS,absorption/emission)and two-photon absorption(TPA)can achieve large redshift via either extending conjugated lengths of frag-3 or enlarging conjugated areas of frag-1 of HBI skeleton.Spectral redshifts of all chromophores are highly related to intramolecular charge transfer(ICT),but neutral ones are closely related to the total ICT or electron-accept-ing-numbers of frag-3,and the high correlative factor of anions is the aromaticity of frag-2 bridge.The frag-2 bridge with high aromaticity can open a reverse charge transfer channel in anion relative to neutral,obtaining significant redshift.Based on analysis,a new 6-hydroxyl-naphthalene-imidazolinone(HNI)series,which have larger conjugated area in frag-1,are pre-dicted.The OPS and TPA of anionic HNI ones acquire about 76−96 nm and 119−146 nm red-shift relative to traditional HBI series respectively as a whole.The longest emission of anionic HNI-4 realizes more 244 nm redshift relative to HBI-1.Our work clarifies worthy spectral reg-ularities and redshift mechanisms of HBI-type chromophores and provides valuable design strategy for infrared chromophores synthesis in experiment.
基金supported by the National Natural Science Foundation of China (No.11604185 and No.11804196)the Taishan Scholar Program of Shandong Province of China
文摘In this work, the optical properties of fluorescent probes used for detection of biothiol were studied by employing time-dependent density functional theory. By calculating the single photon absorption and emission properties of probe Mol.1, Mol.2 and Mol.3 before and after reaction with cysteine and homocysteine, we have investigated the effect of carboncarbon triple bond and benzene ring on the properties of fluorescent probes. It is found that the oscillator strength of probe molecules increases gradually with the improvement of the structure of the electron donor triphenylamine and the addition of carbon-carbon triple bonds, and better properties of fluorescence probes have also been demonstrated. At the same time, the effect of different number of side branches on the molecular properties of the probe was also studied. The results showed that compared with single-branched molecule Z1 and tribranched probe Mol.3, two side probe molecules Z2 had higher oscillator strength and better detection effect. In addition, the new single-branched probe Mol.4 with the addition of carbon-carbon triple bonds and benzene rings has better probe properties and simpler structure than the tribranched probe Mol.3.
文摘Polydimethylsilylenes bearing pyrenyl groups exhibit emissions fromtwisted intramolecular charge transfer state between the aromatic ring and thesilicon backbone both in polar and nonpolar solvents.
文摘In this paper the results of dynamic NMR studies on ethylmethylamino-tertiary-butyl-phenylborane (EMABPB) with or without light are reported. The NMR data were recorded on a Bruker 400 MHz NMR equipped with our custom-made optical probe and with our custom-made 450 watts (W) monochromatic light sources. The molecular photochemistry including twisted intramolecular charge-transfer-excited-state (TICT) of the EMABPB in several solvents has been investigated. These results indicate that the aminoborane demonstrates multiple configurations in CD3Cl and CD2Cl2 resulting in the shifts of the signals of the alkyl groups on the nitrogen and boron. This indicates that there are some time-dependent changes at constant temperature over the irradiation interval. At ﹣60°C and the presence of light (λ = 265 nm), we observed a large change in the populations of the two sites, and this by itself indicates a modification in the rotation around the boron nitrogen bond in the excited state. By considering the existence of the TICT state, many important energy technologies may be developed with higher efficiency by controlling the back-electron transfer processes.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574115 and 11704146)
文摘We theoretically investigate the excited state intramolecular proton transfer(ESIPT) behavior of the novel fluorophore bis-imine derivative molecule HNP which was designed based on the intersection of 1-(hydrazonomethyl)-naphthalene-2-ol and 1-pyrenecarboxaldehyde. Especially, the density functional theory(DFT) and time-dependent density functional theory(TDDFT) methods for HNP monomer are introduced. Moreover, the "our own n-layered integrated molecular orbital and molecular mechanics"(ONIOM) method(TDDFT:universal force field(UFF)) is used to reveal the aggregation-induced emission(AIE) effect on the ESIPT process for HNP in crystal. Our results confirm that the ESIPT process happens upon the photoexcitation for the HNP monomer and HNP in crystal, which is distinctly monitored by the optimized geometric structures and the potential energy curves. In addition, the results of potential energy curves reveal that the ESIPT process in HNP will be promoted by the AIE effect. Furthermore, the highest occupied molecular orbital(HOMO) and lowest unoccupied molecular orbital(LUMO) for the HNP monomer and HNP in crystal have been calculated. The calculation demonstrates that the electron density decrease of proton donor caused by excitation promotes the ESIPT process. In addition, we find that the variation of atomic dipole moment corrected Hirshfeld population(ADCH) charge for proton acceptor induced by the AIE effect facilitates the ESIPT process. The results will be expected to deepen the understanding of ESIPT dynamics for luminophore under the AIE effect and provide insight into future design of high-efficient AIE compounds.
基金Project supported by the National Basic Research Program of China(Grant No.2013CB922204)the National Natural Science Foundation of China(Grant Nos.11574115 and 11704146)the Natural Science Foundation of Jilin Province,China(Grant No.20150101063JC)
文摘Time-dependent density functional theory(TDDFT)method is used to investigate the details of the excited state intramolecular proton transfer(ESIPT)process and the mechanism for temperature effect on the Enol^(*)/Keto^(*)emission ratio for the Me_(2)N-substited flavonoid(MNF)compound.The geometric structures of the S_(0) and S_(1) states are denoted as the Enol,Enol^(*),and Keto*.In addition,the absorption and fluorescence peaks are also calculated.It is noted that the calculated large Stokes shift is in good agreement with the experimental result.Furthermore,our results confirm that the ESIPT process happens upon photoexcitation,which is distinctly monitored by the formation and disappearance of the characteristic peaks of infrared(IR)spectra involved in the proton transfer and in the potential energy curves.Besides,the calculations of highest occupied molecular orbital(HOMO)and lowest unoccupied molecular orbital(LUMO)reveal that the electronegativity change of proton acceptor due to the intramolecular charge redistribution in the S_(1) state induces the ESIPT.Moreover,the thermodynamic calculation for the MNF shows that the Enol^(*)/Keto^(*)emission ratio decreasing with temperature increasing arises from the barrier lowering of ESIPT.
文摘β-cyclodextrin (β-CD) induced aggregation and micelle formation of cetyltrimethylam-mnium broAnde (CTMAB) in aqueous solution is demonstrated by the dual fluorescence of p-N, N-dAnethyladrinobenzoic acid (DMABOA) typical of the twisted intramolecular charge transfer (TICT). The locally excited (LE) state of DMABOA is proved to have the characteristic of intramolecular charge transfer (ICT) with a polarity higher than that of ground state but lower than that of TICT state. The peak positions of the two fluorescence bands and theiI intensity ratio are employed to probe the interaction of β-CD with CTMAB. It is conc1uded that β-CD induces CTMAB aggregation as well as Ancelle formation and may change Ancelle structure. The results also indicate that TICT in aqueous solution may be affected by the anisotropy or viscosity of the medium,increasing viscosity disadvantaging the TICT process.
基金The Ph.D.Programs Foundation of Ministry of Educa-tion of China(No.20030286012)the High Technology Research and De-velopment Program of Jiangsu Province(No.BG2005034)
文摘Two new diarylamine-substituted 1, 8-naphthalimide derivatives are synthesized by Cu I/18-crown-6/K2CO3 catalyst system and characterized by Fourier transform infrared （FT- IR）, ^1H-NMR and elemental analyses. The UV-vis absorption and photoluminescent （PL）spectra of the systems in n-hexane, tetrahydrofuran（THF）, and CH2Cl2 are investigated. These naphthalimide molecules have an absorption band centered at about 450 nm, which is assigned to an intramolecular chargetransfer （ICT）transition, and they emit light at 492, 501 nm in a nonpolar solvent such as n-hexane, and at 600, 620 nm in a polar solvent such as CH2Cl2. From the Lippert-Mataga equation, the difference of the dipole moment between the excited state and the ground state is estimated to be 9.2 and 9.8 D for 4- （ diphenylamine ）-N-（ 2-methoxyphenyl ）-1, 8-naphthalimide （ DMN-1 ） and 4-（ 2-naphthylphenylamine ）-N-（ 2- methoxyphenyl）-1, 8-naphthalimide （DMN-2）, respectively. This large change in the dipole moment upon excitation is typical for photoinduced ICT processes.
基金supported by the National Natural Science Foundation of China(grant nos.22179076 and 22225504)the Department of Education of Guangdong Province,China(grant no.2021KCXTD032)+2 种基金the Natural Science Foundation of Guangdong Province,China(grant no.2022A1515011803)the Science and Technology Innovation Fund for College students in Guangdong Province,China(grant no.2020329105600A000003)Guangdong Provincial Key Laboratory of Catalysis,China(grant no.2020B121201002).
文摘The donor–acceptor(D–A)copolymers,which exhibit wide broad absorption and intensified light-harvesting,are highly captivating for applications in solar conversion and optoelectronics.However,designing a polymer structure that can achieve these photophysical properties simultaneously remains a challenge.Herein,we report two novel cyanated units 4-cyanobenzo[1,2-b:6,5-b′:3,4-c″]trithiophene(CBT)and 4,6-dicyanobenzo[1,2-b:6,5-b′:3,4-c″]trithiophene(C2BT)and their corresponding polymers,PCBT and PC2BT.Very interestingly,the PC2BT exhibited a broad absorption band with full width at half maxima(FWHM)of its absorption spectra,almost twice wider than PCBT and benchmark polymers PM6 and D18.Moreover,the PC2BT demonstrated intensified light-harvesting and long-lived exciton.Our in-depth investigation unveiled that the presence of dicyano substitutions induced a strong intramolecular charge transfer(ICT),which,in turn,resulted in the formation of favorable photophysical properties.Therefore,PC2BT-based polymer solar cells(PSCs)exhibited an efficiency of 18.06%,which was a record-setting efficiency for cyanated polymers.This study suggests an efficient strategy for enhancing ICT to design polymers toward favorable photophysical properties and excellent photovoltaic performance.
