The time resolved transient absorption property, kinetics and mechanism of electron transfer(ET) process of the fluorescence probe, N-(2-hydroxyethyl)-1,8-naphthalimide(NPI) were studied. The transient absorption sp...The time resolved transient absorption property, kinetics and mechanism of electron transfer(ET) process of the fluorescence probe, N-(2-hydroxyethyl)-1,8-naphthalimide(NPI) were studied. The transient absorption spectra of NPI in H 2O-CH 3CN solution were successfully detected upon pulsed excitation at 355 nm. 3NPI was proved as the primary excited state with lifetime of 147 μs. 3NPI underwent the T-T energy transfer with β-carotene and ET with triphenyl amine to produce NPI -·. In the absence of quenchers, the self-quenching of 3NPI by the ground states of NPI took place via ET. The ET from nucleosides to 3NPI was also explored. NPI showed a strong electron-accepting capability and the absorbance of 3NPI was strongly quenched by the nucleosides. The formation of NPI -· was facilitated to a great extent simultaneously. The bimolecular quenching rate constants of NPI by GUA and DGUA were determined as k 3=8.8×106 mol -1·L·s -1, k 4=2.1×107 mol·L·s -1. The ET between NPI and nucleosides was verified and the mechanism was proposed.展开更多
Photoinduced electron transfer (PET) processes between C 60-C 6H 8SO and Tetrathiafulvalene (TTF) have been studied by nanosecond laser photolysis. Quantum yields (Φ et) and rate constants of electron transfe...Photoinduced electron transfer (PET) processes between C 60-C 6H 8SO and Tetrathiafulvalene (TTF) have been studied by nanosecond laser photolysis. Quantum yields (Φ et) and rate constants of electron transfer (k et) from TTF to excited triplet state of fullerene-containing cyclic sulphoxide in benzonitrile (BN) have been evaluated by observing the transient absorption bands in the NIR region. With the decay of excited triplet state of fullerene-containing cyclic sulphoxide, the rise of radical anion of fullerene-containing cyclic sulphoxide is observed.展开更多
The oxidizing mechanism of podophyllotoxin and its derivatives by sodium persulfate has been studied by laser flash photolysis and pulse radiolysis. The formation and decay processes of transient species of podophyllo...The oxidizing mechanism of podophyllotoxin and its derivatives by sodium persulfate has been studied by laser flash photolysis and pulse radiolysis. The formation and decay processes of transient species of podophyllotoxin and its derivatives have been observed, and a series of rate constants for the formation and decay of transient species have been determined. It has been found that there is a light (UV) sensitive group on the C-4 of podophyllotoxin and two light (UV) sensitive groups on the C-4 and C-4’ of 4’-demethylepipodophyllotoxin.展开更多
Time-resolved laser flash photolysis and pulse radiolysis have been used to study the chemical activity of podophyllotoxin(PPT) and etoposide(VP-16). The mechanism of photoionization of etoposide and podophyllotoxin h...Time-resolved laser flash photolysis and pulse radiolysis have been used to study the chemical activity of podophyllotoxin(PPT) and etoposide(VP-16). The mechanism of photoionization of etoposide and podophyllotoxin has been confirmed and illustrated. It is demonstrated that VP-16 and PPT in aqueous solution can be photoionized at 248 nm to give hydrated electron and neutral radical resulting from rapid deprotonation of radical cation of VP-16 and PPT. The quantum yield for the photoionization of VP-16 and PPT with single-photo is 0.21 and 0.61, respectively. In addition, they can react with hydrated electron, hydrogen radical and hydroxyl radical. This will give chemists some advice on synthesizing new derivatives of podophyllotoxin in cancer treatment.展开更多
The triplet state of naphthalimide was investigated by nanosecond laser flash photolysis technique. The quenching of the triplet state of naphthalimide unit by ferrocene were observed for the naphthalimide ferrocene d...The triplet state of naphthalimide was investigated by nanosecond laser flash photolysis technique. The quenching of the triplet state of naphthalimide unit by ferrocene were observed for the naphthalimide ferrocene dyad systems and the mixture of naphthalimide and ferrocene in acetonitrile. The results indicated that there exist the effective triplet energy transfer processes from naphthalimide to ferrocene.展开更多
文摘The time resolved transient absorption property, kinetics and mechanism of electron transfer(ET) process of the fluorescence probe, N-(2-hydroxyethyl)-1,8-naphthalimide(NPI) were studied. The transient absorption spectra of NPI in H 2O-CH 3CN solution were successfully detected upon pulsed excitation at 355 nm. 3NPI was proved as the primary excited state with lifetime of 147 μs. 3NPI underwent the T-T energy transfer with β-carotene and ET with triphenyl amine to produce NPI -·. In the absence of quenchers, the self-quenching of 3NPI by the ground states of NPI took place via ET. The ET from nucleosides to 3NPI was also explored. NPI showed a strong electron-accepting capability and the absorbance of 3NPI was strongly quenched by the nucleosides. The formation of NPI -· was facilitated to a great extent simultaneously. The bimolecular quenching rate constants of NPI by GUA and DGUA were determined as k 3=8.8×106 mol -1·L·s -1, k 4=2.1×107 mol·L·s -1. The ET between NPI and nucleosides was verified and the mechanism was proposed.
基金ProjectsupportedbytheNationalNaturalScienceFoundationofChina (No .2 0 0 710 12 ) ,ResearchFundfortheYoungTeacherPro gramofHigherEducationofChina (No .2 0 0 0 6 5 )andtheNaturalScienceFoundationofGuangdongProvince (No .0 0 0 70 0 )
文摘Photoinduced electron transfer (PET) processes between C 60-C 6H 8SO and Tetrathiafulvalene (TTF) have been studied by nanosecond laser photolysis. Quantum yields (Φ et) and rate constants of electron transfer (k et) from TTF to excited triplet state of fullerene-containing cyclic sulphoxide in benzonitrile (BN) have been evaluated by observing the transient absorption bands in the NIR region. With the decay of excited triplet state of fullerene-containing cyclic sulphoxide, the rise of radical anion of fullerene-containing cyclic sulphoxide is observed.
文摘The oxidizing mechanism of podophyllotoxin and its derivatives by sodium persulfate has been studied by laser flash photolysis and pulse radiolysis. The formation and decay processes of transient species of podophyllotoxin and its derivatives have been observed, and a series of rate constants for the formation and decay of transient species have been determined. It has been found that there is a light (UV) sensitive group on the C-4 of podophyllotoxin and two light (UV) sensitive groups on the C-4 and C-4’ of 4’-demethylepipodophyllotoxin.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 39700029).
文摘Time-resolved laser flash photolysis and pulse radiolysis have been used to study the chemical activity of podophyllotoxin(PPT) and etoposide(VP-16). The mechanism of photoionization of etoposide and podophyllotoxin has been confirmed and illustrated. It is demonstrated that VP-16 and PPT in aqueous solution can be photoionized at 248 nm to give hydrated electron and neutral radical resulting from rapid deprotonation of radical cation of VP-16 and PPT. The quantum yield for the photoionization of VP-16 and PPT with single-photo is 0.21 and 0.61, respectively. In addition, they can react with hydrated electron, hydrogen radical and hydroxyl radical. This will give chemists some advice on synthesizing new derivatives of podophyllotoxin in cancer treatment.
文摘The triplet state of naphthalimide was investigated by nanosecond laser flash photolysis technique. The quenching of the triplet state of naphthalimide unit by ferrocene were observed for the naphthalimide ferrocene dyad systems and the mixture of naphthalimide and ferrocene in acetonitrile. The results indicated that there exist the effective triplet energy transfer processes from naphthalimide to ferrocene.
