Photo-induced intramolecular electron transfer （PIET） and intramolecular vibrational relaxation （IVR） dynamics of the excited state of rhodamine 6G （Rh6G＋） in DMSO are investigated by multiplex transient gratin...Photo-induced intramolecular electron transfer （PIET） and intramolecular vibrational relaxation （IVR） dynamics of the excited state of rhodamine 6G （Rh6G＋） in DMSO are investigated by multiplex transient grating. Two major compo- nents are resolved in the dynamics of Rh6G＋. The first component, with a lifetime τTPIET = 140 fs-260 fs, is attributed to PIET from the phenyl ring to the xanthene plane. The IVR process occurring in the range ZIVR = 3.3 ps-5.2 ps is much slower than the first component. The PIET and IVR processes occurring in the excited state of Rh6G＋ are quantitatively determined, and a better understanding of the relationship between these processes is obtained.展开更多
A novel triad system zinc phthalocyanine-viologen-ferrocene has been synthesized.Photoinduced intramolecular electron transfer in the new triad system was investigated by fluorescence quenching experiment and nanoseco...A novel triad system zinc phthalocyanine-viologen-ferrocene has been synthesized.Photoinduced intramolecular electron transfer in the new triad system was investigated by fluorescence quenching experiment and nanosecond flash photolysis technique,giving a final long-living charge- separated state.A mechanism of two-step charge separation was suggested.展开更多
Reproduction of ubiquitous metal-ligand cooperativity in copper-oxygen enzyme mimics is crucial for the comprehension of catalytic mechanisms in coppercontaining enzymes and copper-catalyzed chemical transformations.H...Reproduction of ubiquitous metal-ligand cooperativity in copper-oxygen enzyme mimics is crucial for the comprehension of catalytic mechanisms in coppercontaining enzymes and copper-catalyzed chemical transformations.Here we describe the synthesis and reduction behavior of a series of encapsulated dinuclear copper-oxygen species by systematically altering the size and geometric structure of peripheral macrocyclic ligands.Along with the occurrence of a single-electron reduction,these macrocycleencircled dicopper complexes show distinct electron transfer pathways as a function of differently sized and substituted macrocyclic ligands.Detailed structural characterization and density functional theory calculations reveal that a coupled metal-ligand and bimetallic cooperativity is involved in the singleelectron reductionof hydroxyl-bridged dicopper species within macrocyclic homologue ligands Py[7]Ph[1]and Py[7]Ph[1]-Me.The highly flexible configurations of macrocyclic ligands are conducive to stabilizing copper-oxygen intermediates with different valence states and facilitating an intramolecular electron transfer between macrocyclic ligands and the central copper-oxygen moiety.Correlation of biased electron transfer behaviors of copper-oxygen species with their peripheral macrocyclic ligands provides a new means of tuning redox properties of metal cluster species and opens a broader prospect on the mechanistic study of copper-containing enzymes and copper-catalyzed transformations.展开更多
Searching new structured black phosphorus(BP)and exploring intriguing functions and applications have become a hot topic so far.Here,we introduce a novel Iso-type black phosphorus heterostructure guided by first princ...Searching new structured black phosphorus(BP)and exploring intriguing functions and applications have become a hot topic so far.Here,we introduce a novel Iso-type black phosphorus heterostructure guided by first principle calculation,which features unique heterointerface and electronic coupling interaction via stacking assembly of exfoliated black phosphorus(EBP)and amine-functionalized EBP(N-EBP).Inspired by the theoretical results,we constructed the Iso-type heterostructure comprising of ultrathin exfoliated few-layered EBP and N-EBP,both of which were derived from identical bulk BP.The purposive amine-functionalization not only creates positively-charged P atoms on N-EBP as effective active sites via N-induced intramolecular electron transfer(IET)but also endows N-EBP with lower work function relative to EBP,while the unique EBP/N-EBP Iso-type heterostructure engenders directional heterointerfacial electron transfer(HET).The coupled IET/HET effects optimize the charge redistribution to afford favorable O_(2)adsorption.In this case,our unique strategy for the first time exploits the inherent catalytic capability of BP toward the oxygen reduction reaction(ORR)and enables the first use of BP as metal-free ORR catalysts for Zn-air cells.The newly-designed heterostructure facilitates a 4-e^(-)transfer ORR relative to inactive EBP or N-EBP.Importantly,the polymer-shielded heterostructure acts as efficient air electrodes to endow a primary Zn-air cell with high stability,large capacity and high energy density—superior to the commercial Pt/C-enabled cell.This study as the first report on metal-free BP-based ORR catalysts and air electrodes not only extends BP's application scopes but also renders new insight toward design of electronically-coupled superstructures for energy-related applications.展开更多
A series of polyads consisting of covalently-(CH2)4-linked fluorescein with carbazole and violger.Live been synthesized and characterized The studies of absorption,emission spectra and fluorescence lifetime quenching ...A series of polyads consisting of covalently-(CH2)4-linked fluorescein with carbazole and violger.Live been synthesized and characterized The studies of absorption,emission spectra and fluorescence lifetime quenching indicated that the intramolecular fluorescence quenching of fluorescein by violgen is mainly a static process through the formation of non emission complex (fluorescence quenching efficiency φQ=0.97,lifetime quenching efficiency φH 0,quenching efficiency of formation of non-emission complex φC=0.97); while the quenching by carbazole is mainly a dynamic electron transfer process (φQ=0.63,φET=0.63,φC=0).In the violgen-fluorescein-carbazole triads,φQ=0.97,Q ET=0.65,φC=0.32,which suggests that the photoinduced interaction of fluorescein-carbazole pair and that of violgen-fluorescein pair are in a competitive process,the dynamic electron transfer from carbazole to fluorecein is dominant in the process The free energy change of the photoinduced electron transfer and the back reac-tiorns展开更多
Inter-and intramolecular quenching of zinc phthalocyanine fluorescence by anthraquinone has been studied.The diminutions of fluorescence quantum yield and life-time are due primarily to electron transfer.Apparent elec...Inter-and intramolecular quenching of zinc phthalocyanine fluorescence by anthraquinone has been studied.The diminutions of fluorescence quantum yield and life-time are due primarily to electron transfer.Apparent electron transfer rate constants were calculated depending on the chain length and solvent polarity.展开更多
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
ELECTRON transfer plays a crucial role in energy transformation of natural biological systemssuch as the photosynthetic process by which plants convert solar energy into chemical energy.This is achieved in photosynthe...ELECTRON transfer plays a crucial role in energy transformation of natural biological systemssuch as the photosynthetic process by which plants convert solar energy into chemical energy.This is achieved in photosynthesis by a series of electron transfers which occur after light is ab-sorbed. Among the various factors which influence the efficiency of electron transfer struc-tural effect is one of the important features to be considered. In recent years, numerous syn-thetic model dyads in which electron donor and electron acceptor are covalently linked by dif-ferent spacers have been designed and synthesized in an effort to understand how the展开更多
Photoinduced electron transfer process is a crucial step in photooxidation to obtain synthetic chemicals. How- ever, the driving forces of electron transfer as priority in all have been rarely studied in stepwise deta...Photoinduced electron transfer process is a crucial step in photooxidation to obtain synthetic chemicals. How- ever, the driving forces of electron transfer as priority in all have been rarely studied in stepwise detail. Herein, we report a series of BODIPY derivatives with an emphasis on the intramolecular charge transfer, enhancing the key step of photoinduced electron transfer process and photooxidation performances. A series of novel BODIPY photosensitizers （B-1--B-5） were prepared, wherein diethylamine amino of B-3 as charge injection group was conjugated to the 2,6-diiodo-styryl-BODIPY, and the electron transfer impetus was enhanced 1.6 times due to its more negative redox potentials. These results were also confirmed by the DFT/TDDFT calculation. Without pure oxygen, B-3 still can exhibit an exceptional performance in photoxidative aromatization of 1,4-DHP under mild condition. After irradiation for 28 rain, the conversion rate came to 98.2%.展开更多
pH titration of the fluorescence of N-(1-naphthyl)aminoacetic acid(NAA) was performed in aqueous solution over pH range of 1 5—12 5. Despite no shift in the fluorescence maximum wavelength, the titration curve showed...pH titration of the fluorescence of N-(1-naphthyl)aminoacetic acid(NAA) was performed in aqueous solution over pH range of 1 5—12 5. Despite no shift in the fluorescence maximum wavelength, the titration curve showed an Ω-shaped profile with increasing pH with two inflection points at pH 4 1 and pH 11 5, respectively. These values correspond to the excited-state pK *_a s of carboxylic group and ammonium cation, respectively, which are both higher than those of the corresponding ground-state pK_as of 2 64 and 11 83, of which the former changes more. The substantial weakening of the proton dissociation of carboxylic group in the excited state should be indicative of the decrease in the inductive +I-effect of the ammonium cation at the β-position due to the excited-state intramolecular charge transfer from naphthalene moiety to ammonium. The latter was also confirmed by the slight increase in the exited-state pK *_ a2. The fact that the increase in pK *_ a1 is larger than that in pK *_ a2 suggests that the effect of the intramolecular charge transfer on the involved moiety be weaker than that on a remote moiety in the same species. This could be taken into consideration for designing means of tuning the structures and properties of peptide and protein via photo-excitation. It was identified that the NAA zwitterion(Ⅱ) was the emissive species. The fluorescence quenching at high pH was assumed to be due to the photo-induced intramolecular electron transfer between carboxylate anion and the excited naphthalene moiety. The present case represents an example in which both intramolecular charge transfer and electron transfer occur to shape the pH titration profile.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21003033 and 21203047)the Guangxi Provincial Natural Science Foundation,China(Grant Nos.2012GXNSFBA053012 and 2014GXNSFAA118019)the Research Foundation of Education Bureau of Guangxi Zhuang Autonomous Region,China(Grant No.ZD2014127)
文摘Photo-induced intramolecular electron transfer （PIET） and intramolecular vibrational relaxation （IVR） dynamics of the excited state of rhodamine 6G （Rh6G＋） in DMSO are investigated by multiplex transient grating. Two major compo- nents are resolved in the dynamics of Rh6G＋. The first component, with a lifetime τTPIET = 140 fs-260 fs, is attributed to PIET from the phenyl ring to the xanthene plane. The IVR process occurring in the range ZIVR = 3.3 ps-5.2 ps is much slower than the first component. The PIET and IVR processes occurring in the excited state of Rh6G＋ are quantitatively determined, and a better understanding of the relationship between these processes is obtained.
文摘A novel triad system zinc phthalocyanine-viologen-ferrocene has been synthesized.Photoinduced intramolecular electron transfer in the new triad system was investigated by fluorescence quenching experiment and nanosecond flash photolysis technique,giving a final long-living charge- separated state.A mechanism of two-step charge separation was suggested.
基金Financial support by NSFC(22025105,91956125,and 21821001)the Shuimu Tsinghua Scholar Program is gratefully acknowledged.
文摘Reproduction of ubiquitous metal-ligand cooperativity in copper-oxygen enzyme mimics is crucial for the comprehension of catalytic mechanisms in coppercontaining enzymes and copper-catalyzed chemical transformations.Here we describe the synthesis and reduction behavior of a series of encapsulated dinuclear copper-oxygen species by systematically altering the size and geometric structure of peripheral macrocyclic ligands.Along with the occurrence of a single-electron reduction,these macrocycleencircled dicopper complexes show distinct electron transfer pathways as a function of differently sized and substituted macrocyclic ligands.Detailed structural characterization and density functional theory calculations reveal that a coupled metal-ligand and bimetallic cooperativity is involved in the singleelectron reductionof hydroxyl-bridged dicopper species within macrocyclic homologue ligands Py[7]Ph[1]and Py[7]Ph[1]-Me.The highly flexible configurations of macrocyclic ligands are conducive to stabilizing copper-oxygen intermediates with different valence states and facilitating an intramolecular electron transfer between macrocyclic ligands and the central copper-oxygen moiety.Correlation of biased electron transfer behaviors of copper-oxygen species with their peripheral macrocyclic ligands provides a new means of tuning redox properties of metal cluster species and opens a broader prospect on the mechanistic study of copper-containing enzymes and copper-catalyzed transformations.
基金financial support from the National Natural Science Foundation of China(Grant Nos.51973240,51833011 and 52003303)the China Postdoctoral Science Foundation(Grant Nos.2019M653176 and 2020M672932)+2 种基金the Guang-dong Provincial Basic and Applied Basic Research Fund Natural Science Foundation(Grant No.2020A1515111095)the Fundamental Research Funds for the Central Universities(Grant No.191-gpy117)the Guangdong YangFan Innovative&Entrepreneurial Research Team Program(Grant No.2016YT03C077)。
文摘Searching new structured black phosphorus(BP)and exploring intriguing functions and applications have become a hot topic so far.Here,we introduce a novel Iso-type black phosphorus heterostructure guided by first principle calculation,which features unique heterointerface and electronic coupling interaction via stacking assembly of exfoliated black phosphorus(EBP)and amine-functionalized EBP(N-EBP).Inspired by the theoretical results,we constructed the Iso-type heterostructure comprising of ultrathin exfoliated few-layered EBP and N-EBP,both of which were derived from identical bulk BP.The purposive amine-functionalization not only creates positively-charged P atoms on N-EBP as effective active sites via N-induced intramolecular electron transfer(IET)but also endows N-EBP with lower work function relative to EBP,while the unique EBP/N-EBP Iso-type heterostructure engenders directional heterointerfacial electron transfer(HET).The coupled IET/HET effects optimize the charge redistribution to afford favorable O_(2)adsorption.In this case,our unique strategy for the first time exploits the inherent catalytic capability of BP toward the oxygen reduction reaction(ORR)and enables the first use of BP as metal-free ORR catalysts for Zn-air cells.The newly-designed heterostructure facilitates a 4-e^(-)transfer ORR relative to inactive EBP or N-EBP.Importantly,the polymer-shielded heterostructure acts as efficient air electrodes to endow a primary Zn-air cell with high stability,large capacity and high energy density—superior to the commercial Pt/C-enabled cell.This study as the first report on metal-free BP-based ORR catalysts and air electrodes not only extends BP's application scopes but also renders new insight toward design of electronically-coupled superstructures for energy-related applications.
基金Project supported by the National Natural Science Foundation of China (No. 59333072)
文摘A series of polyads consisting of covalently-(CH2)4-linked fluorescein with carbazole and violger.Live been synthesized and characterized The studies of absorption,emission spectra and fluorescence lifetime quenching indicated that the intramolecular fluorescence quenching of fluorescein by violgen is mainly a static process through the formation of non emission complex (fluorescence quenching efficiency φQ=0.97,lifetime quenching efficiency φH 0,quenching efficiency of formation of non-emission complex φC=0.97); while the quenching by carbazole is mainly a dynamic electron transfer process (φQ=0.63,φET=0.63,φC=0).In the violgen-fluorescein-carbazole triads,φQ=0.97,Q ET=0.65,φC=0.32,which suggests that the photoinduced interaction of fluorescein-carbazole pair and that of violgen-fluorescein pair are in a competitive process,the dynamic electron transfer from carbazole to fluorecein is dominant in the process The free energy change of the photoinduced electron transfer and the back reac-tiorns
文摘Inter-and intramolecular quenching of zinc phthalocyanine fluorescence by anthraquinone has been studied.The diminutions of fluorescence quantum yield and life-time are due primarily to electron transfer.Apparent electron transfer rate constants were calculated depending on the chain length and solvent polarity.
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.
文摘ELECTRON transfer plays a crucial role in energy transformation of natural biological systemssuch as the photosynthetic process by which plants convert solar energy into chemical energy.This is achieved in photosynthesis by a series of electron transfers which occur after light is ab-sorbed. Among the various factors which influence the efficiency of electron transfer struc-tural effect is one of the important features to be considered. In recent years, numerous syn-thetic model dyads in which electron donor and electron acceptor are covalently linked by dif-ferent spacers have been designed and synthesized in an effort to understand how the
基金We thank the support of National Natural Science Foundation of China （Grant 21302224, 51172285, 21176259, 51303212, 51303202）, China Postdoctoral Science Foundation （2014M560590, 2015T80758）, Fundamental Research Funds for the Central Universities （15CX05010A）, Shandong Provincial Natural Science Foundation （ZR2013BQ028, ZR2013EMQ013）, Project of Science and Technology Program for Basic Research of Qingdao （14-2-4-47-jch） and the State Key Laboratory of Fine Chemicals （KF 1203）.
文摘Photoinduced electron transfer process is a crucial step in photooxidation to obtain synthetic chemicals. How- ever, the driving forces of electron transfer as priority in all have been rarely studied in stepwise detail. Herein, we report a series of BODIPY derivatives with an emphasis on the intramolecular charge transfer, enhancing the key step of photoinduced electron transfer process and photooxidation performances. A series of novel BODIPY photosensitizers （B-1--B-5） were prepared, wherein diethylamine amino of B-3 as charge injection group was conjugated to the 2,6-diiodo-styryl-BODIPY, and the electron transfer impetus was enhanced 1.6 times due to its more negative redox potentials. These results were also confirmed by the DFT/TDDFT calculation. Without pure oxygen, B-3 still can exhibit an exceptional performance in photoxidative aromatization of 1,4-DHP under mild condition. After irradiation for 28 rain, the conversion rate came to 98.2%.
文摘pH titration of the fluorescence of N-(1-naphthyl)aminoacetic acid(NAA) was performed in aqueous solution over pH range of 1 5—12 5. Despite no shift in the fluorescence maximum wavelength, the titration curve showed an Ω-shaped profile with increasing pH with two inflection points at pH 4 1 and pH 11 5, respectively. These values correspond to the excited-state pK *_a s of carboxylic group and ammonium cation, respectively, which are both higher than those of the corresponding ground-state pK_as of 2 64 and 11 83, of which the former changes more. The substantial weakening of the proton dissociation of carboxylic group in the excited state should be indicative of the decrease in the inductive +I-effect of the ammonium cation at the β-position due to the excited-state intramolecular charge transfer from naphthalene moiety to ammonium. The latter was also confirmed by the slight increase in the exited-state pK *_ a2. The fact that the increase in pK *_ a1 is larger than that in pK *_ a2 suggests that the effect of the intramolecular charge transfer on the involved moiety be weaker than that on a remote moiety in the same species. This could be taken into consideration for designing means of tuning the structures and properties of peptide and protein via photo-excitation. It was identified that the NAA zwitterion(Ⅱ) was the emissive species. The fluorescence quenching at high pH was assumed to be due to the photo-induced intramolecular electron transfer between carboxylate anion and the excited naphthalene moiety. The present case represents an example in which both intramolecular charge transfer and electron transfer occur to shape the pH titration profile.
