Picosecond Laser Photolysis Studies Research Articles

Picosecond laser photolysis studies on a photochromic oxidation polymer film consisting of diarylethene molecules

Picosecond laser spectroscopy was applied to the direct detection of photochromic reaction processes in a network polymer film prepared by oxidation polymerization of a diarylethene derivative. Both the coloration due to the cyclization and the decoloration via the cycloreversion took place in less than 30 ps. The time constants of both photochromic reactions were almost the same as those of diarylethene monomers obtained in the solutions, indicating that the oxidation polymer film system retains a similarly high response time as in the solution phase.

The Aryl Cation – the Trapping and Characterisation of a Hyper-Reactive Species

The article traces the development of the epr and optical spectroscopic characterisation and progressive theoretical understanding of the aryl cation, starting from the initial cryogenic epr study of 2,5-dialkoxyl-4-morpholinophenyl cation, which defined unambiguously its triplet state character, through simple MO, ab initio and DFT calculations on substituted aryl cations, to picosecond laser photolysis studies in fluorinated solvents, noting especially the early and vital contribution of Martyn Symons.

Picosecond laser photolysis studies on photoinduced electron transfer processes in poly(1-vinylpyrene) in solutions

The primary processes of photoinduced electron transfer (ET) dynamics in poly(1-vinylpyrene) (PVPy) doped with electron acceptors were investigated by means of picosecond transient absorption measurement in solutions with different polarities. The simple scheme (Scheme 1) based on a one-dimensional random walk model that the cation radical continuously migrates along pendant aromatic moieties in the polymer chain interprets the hole transfer (HT) dynamics in the longer delay time after the excitation. However, in the early stage, the deviation observed due to the dimer cation formation, which acts as a trap site for the cation and a very slow HT process occurred as a result of a detrapping process. By integrating the present results with the previous investigation on other aromatic vinyl polymers, the role of the dimer cation on the hole migration process along the polymer chain were discussed.

Picosecond laser photolysis studies of DMA–DMPP in solution

Picosecond transient absorption spectra of: 4-(4′- N,N-dimethylaminophenyl)–3,5-dimethyl-1,7-diphenyl-bis-pyrazolo-[3,4-b;4′,3′-e]-pyridine (DMA–DMPP), 3,5-dimethyl-1,7-diphenyl-bis-pyrazolo-[3,4-b;4′,3′-e]-pyridine (BPP) and 3,5-dimethyl-1,4,7-triphenyl-bis-pyrazolo-[3,4-b;4′,3′-e]-pyridine (H-DMPP) were measured in solvents of different polarity. The results revealed the previously postulated change of the character of the fluorescing state from a primary excited, low polar state in non-polar solvents to a CT state in highly polar ones. Transient absorption spectra in the equilibrium fluorescent state of DMA–DMPP in polar solvents comprised the band ascribable to the cation radical of the DMA moiety. The charge transfer process is fastest in methanol and acetonitrile; in the former it is not controlled by a dynamic Stokes shift.

Picosecond laser photolysis studies on a photochromic dithienylethene in solution and in crystalline phases

Picosecond transient absorption spectroscopy and fluorescence measurement were applied to the direct observation of photochromic reaction of 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene (DMTF) in solutions as well as in crystalline phase. In both phases, very rapid (⩽ ≈ 10 ps) reaction channel of the ring-closure was found. the mechanism of ultrafast reaction process was discussed by comparing the present result with those of other diarylethene derivatives.

Picosecond Laser Photolysis Studies on Chain-Length, Solvent and Temperature Dependences of the Intramolecular Photoreduction Process of Benzophenone by Diphenylamine

Abstract Photoinduced hydrogen abstraction (HA) processes of 1-(4-anilinophenyl)-2-(4-benzophenoxy)ethane, 1-(4-anilinophenyl)-3-4-benzophenoxy)propane, and 1-(4-anilinophenyl)-8-(4-benzophenoxy)octane (BP–O–(CH2)n–O–DPA: n = 2, 3, and 8) in benzene, acetonitrile, and N,N-dimethylformamide solutions were investigated by means of picosecond transient absorption spectroscopy. In benzene solution, apparent mechanism of the hydrogen abstraction reaction was “direct” process and no absorption spectrum of the charge separated state was observed. The decay of triplet benzophenone moiety (3BP*) was regulated by the dynamic rearrangement process of the mutual geometry between 3BP* and DPA to a more compact one. In polar solutions, the electron transfer (ET) from DPA to 3BP* moiety took place in addition to the direct HA from DPA by 3BP*. The rate of the ET reaction was regulated mainly by the distance between the reactant moieties. Moreover, the intra-ion pair (IP) proton transfer (PT) resulting in the HA product formation was observed, although such PT process in the IP state between the unlinked 3BP* and the secondary amine was not observed. By integrating the present results on the linked systems with those of the unlinked systems, the role of the ET or CT interaction in the HA process of 3BP* from the secondary amine was discussed.

Picosecond laser photolysis studies on photochromic reactions of 1,2-bis(2,4,5-trimethyl-3-thienyl)maleic anhydride in solutions

Picosecond laser photolysis and transient absorption spectroscopy were applied to the direct observation of the photochromic reactions, such as ring-closure and ring-opening processes, of 1,2-bis(2,4,5-trimethyl-3-thienyl)maleic anhydride in solutions. Both in the ring-closure and the ring-opening processes, very rapid ( < 10 ps) reaction channels were found. The mechanisms of ultrafast reaction processes and their solvent dependence were discussed.

Picosecond laser photolysis studies of a vitamin B12 model system.

Picosecond laser photolysis studies of a vitamin B12 model system.

Picosecond laser photolysis studies on the intramolecular photoreduction process of benzophenone by diphenylamine linked by spacers in acetonitrile solution

Photoinduced hydrogen abstraction (HA) processes of 1-(4-benzophenoxy)-3-[4-(phenyl-amino)phenoxy]propane (BP-O-(CH 2) 3-O-DPA) and 1-(4-benzophenoxy)-2-[4-(phenylamino)phenoxy]ethane (BP-O-(CH 2) 2-O-DPA) in acetonitrile solution were investigated by means of picosecond transient absorption spectroscopy. The stable ion pair (IP) formation followed by proton transfer (PT) resulting in the HA reaction was observed for the photoreduction of (BP-O-(CH 2) 2-O-DPA). On the other hand, in addition to inter-ionic PT in the stable IP, direct HA of excited triplet benzophenone ( 3BP*) moiety was observed for BP-O-(CH 2) 3-O-DPA. On the basis of the dependence of the apparent reaction mechanisms on the molecular conformation and by comparison with the intermolecular HA process, the role of the electron transfer or CT interaction in the HA process of 3BP* from the secondary amine was discussed.

Strongly exothermic electron-transfer reaction in the excited singlet state of alkylcarbazole-polynitrofluorene and -polynitrofluorenone bichromophoric systems. 1. Correlation between the probability of charge separation, photoactivity, and picosecond laser photolysis studies on the photoinduced charge recombination of ion pair state produced in some media

The present study was undertaken to investigate the parameters controlling the rate of forward and backward electron-transfer reactions in strongly exothermic bichromophoric systems of the alkylcarbazole-polynitrofluorene and -polynitrofluorenone type. Electronic absorption spectra of these bichromophoric systems in acetonitrile have shown the appearance of charge-transfer bands from which the electronic matrix elements for electron transfer is evaluated (∼40 meV). From the redox properties of the D-S-A couples the rates for charge separation (CS) is calculated using the semi-quantum-mechanical theory applied to these nonadiabatic electron-transfer reactions

Vibrational energy dissipation process in solution: picosecond laser photolysis studies of biphenylene

Biphenylene in various solvents is investigated by picosecond time-resolved absorption spectroscopy. The time dependence of the spectral shape of the vibrationally hot S n ←S 1 absorption was analyzed by using the Urbach relation. Vibrational energy flow to the solvent molecules in the surroundings from the higher vibrational state of S 1 was proportional to the excess vibrational energy.

Femtosecond–Picosecond Laser Photolysis Studies on Reduction Process of Excited Benzophenone with Tertiary Aromatic Amines in Acetonitrile Solution

Abstract Photoreduction processes of benzophenone (BP)-N,N-diethylaniline (DEA) system in acetonitrile solution were studied by means of femtosecond–pecosecond laser photolysis and time resolved transient absorption spectroscopy. The reaction processes including the formation of geminate ion pairs (IP) by electron transfer (ET) between BP* and DEA at encounter followed by intra-IP proton transfer giving the ketyl radical (BPH·) were clearly observed in both triplet and singlet excited state, while the IP produced by excitation of the CT complex between BP and amine formed easily in more or less concentrated solutions did not give BPH·. In addition to the detailed investigations on the BP-DEA system, we made comparative studies on BP–tertiary aromatic amine systems including N,N-diethyl-p-toluidine, N,N-dimethylaniline, and N-methyldiphenylamine. We observed clearly the characteristic tendency that the proton transfer rate in the 3IP decreased with decrease of the oxidation potential of the amine. This result was interpreted as due to the increase of the inter-ionic distance in the 3IP with increase of the free energy gap for the charge separation at encounter.

Picosecond laser photolysis studies on the electron transfer and charge shift processes in flavin mononucleotide-cytochrome c-EDTA molecular organization

Photoinduced electron transfer (ET) and charge shift (CS) processes in a flavin mononucleotide (FMN)-cytochrome c (cyt c)-EDTA solid film have been investigated by means of picosecond-transient-absorption and fluorescence spectroscopy. Rapid electron transfer between the excited singlet state of FMN and EDTA, followed by the CS process from the reduced form of FMN to cyt c, have been observed. In addition, the excited state dynamics of cyt c and its reaction with EDTA in the solid film are also revealed.

Picosecond laser photolysis studies on the photorepair of pyrimidine dimers by DNA photolyase. 1. Laser photolysis of photolyase-2-deoxyuridine dinucleotide photodimer complex

Picosecond laser photolysis studies on the photorepair of pyrimidine dimers by DNA photolyase. 1. Laser photolysis of photolyase-2-deoxyuridine dinucleotide photodimer complex

ChemInform Abstract: Picosecond 266‐nm Multiphoton Laser Photolysis Studies on Liquid Alkane Solution of Aromatic Hydrocarbons: Ultrafast Solute Triplet Formation

ChemInformVolume 21, Issue 33 Physical Organic Chemistry ChemInform Abstract: Picosecond 266-nm Multiphoton Laser Photolysis Studies on Liquid Alkane Solution of Aromatic Hydrocarbons: Ultrafast Solute Triplet Formation H. MIYASAKA, H. MIYASAKA Dep. Chem., Fac. Eng. Sci., Osaka Univ., Toyonaka, Osaka 560, JapanSearch for more papers by this authorH. MASUHARA, H. MASUHARA Dep. Chem., Fac. Eng. Sci., Osaka Univ., Toyonaka, Osaka 560, JapanSearch for more papers by this authorN. MATAGA, N. MATAGA Dep. Chem., Fac. Eng. Sci., Osaka Univ., Toyonaka, Osaka 560, JapanSearch for more papers by this author H. MIYASAKA, H. MIYASAKA Dep. Chem., Fac. Eng. Sci., Osaka Univ., Toyonaka, Osaka 560, JapanSearch for more papers by this authorH. MASUHARA, H. MASUHARA Dep. Chem., Fac. Eng. Sci., Osaka Univ., Toyonaka, Osaka 560, JapanSearch for more papers by this authorN. MATAGA, N. MATAGA Dep. Chem., Fac. Eng. Sci., Osaka Univ., Toyonaka, Osaka 560, JapanSearch for more papers by this author First published: August 14, 1990 https://doi.org/10.1002/chin.199033036Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume21, Issue33August 14, 1990 RelatedInformation

Picosecond laser photolysis studies on the photochromism of a furylfulgide

Photo-induced cyclization process of a furylfulgide, 2-[1-(2,5-dimethyl-3-furyl)-2-methylpropylidene]-3-isopropylidenesuccinic anhydride, in polymer films were studied by picosecond transient absorption spectroscopy. Polymers used were poly(methyl methacrylate), polystyrene and nitrocellulose. On irradiation with ultraviolet light, the open form of the fulgide was cyclized to give a colored form with a time constants of ≈ 10 ps, which was almost independent of the film materials used in this study.

Femtosecond-picosecond laser photolysis studies on the dynamics of excited charge-transfer complexes in solution. 2. Ion pair formation processes in the excited states of 1,2,4,5-tetracyanobenzene-aromatic hydrocarbon complexes in polar solvents

Femtosecond and picosecond laser photolysis and time-resolved transient absorption spectral studies have been made-to elucidate the photoinduced charge separation (CS) process in the 1,2,4,5-tetracyanobenzene (TCNB)-aromatic hydrocarbon charge-transfer (CT) complexes in various polar solvents. We have confirmed that, in a polar solvent such as acetonitrile, solvent reorientation can induce CS with a time constant shorter than 1 ps to a considerable extent but not completely. Moreover, we have demonstrated that, for the complete CS leading to the ion-pair formation, further intracomplex structural change and solvation, which take place with a time constant (τ CS ) of several picoseconds to 30 ps depending on the natures of the electron-donating aromatic hydrocarbon and the polar solvent, are necessary

Picosecond 266-nm multiphoton laser photolysis studies on liquid alkane solution of aromatic hydrocarbons: ultrafast solute triplet formation

Triplet formation of aromatic hydrocarbon solute in aliphatic hydrocarbon solution in the picosecond to a few nanosecond time region induced by multiphoton excitation with 266-nm picosecond laser pulse is demonstrated. Mechanisms of the rapid triplet state formation, especially the contribution of the ionized state of solvent molecule to it, are discussed by comparing the results of picosecond laser photolysis studies with those of pulse radiolysis studies on nonpolar solutions of aromatic hydrocarbons, where a rapid solute triplet formation in the subnanosecond region has been observed rather frequently.

Femtosecond-picosecond laser photolysis studies on the photoinduced charge separation and charge recombination of a produced ion pair state of some typical intramolecular exciplex compounds in alkanenitrile solvents

Femtosecond and picosecond laser photolysis and time-resolved absorption spectral studies have been made to observe directly the photoinduced charge separation (CS) and charge recombination (CR) of a produced CS state of aromatic amine (D) and aromatic hydrocarbon (A) combined systems: p-(CH 3 ) 2 N-Ph-(CH 2 ) n -(1-pyrenyl) (P n , n=1, 2, 3) and p-(CH 3 ) 2 N-Ph-(CH 2 ) n -(9-anthryl) (A n , n=0, 1, 2, 3), in alkanenitrile solvents

Picosecond Laser Photolysis Studies on the Photoreduction of Excited Benzophenone by Diphenylamine in Solutions

Abstract The mechanism of photoreduction of benzophenone (BP) by diphenylamine (DPA) in isooctane as well as acetonitrile and other polar solvents has been investigated by means of picosecond laser photolysis and time-resolved transient absorption spectral measurements. The results of measurements have demonstrated clearly that the hydrogen abstraction and charge transfer (CT) or ion pair (IP) state formation by electron transfer are competing at encounter between triplet benzophenone (3BP*) and DPA both in nonpolar and polar solvent, and the CT or IP state relaxed with respect to the donor acceptor configurations and solvation does not contribute to the ketyl radical formation. It has been concluded that the very short-lived CT state at encounter between 3BP* and DPA plays a crucial role in the hydrogen abstraction reaction, i.e. the mutual orientation of 3BP* and DPA in this very short-lived CT state at encounter will determine the successive process, the formation of the ketyl radical or relaxed CT or IP state.