EDA Systems Research Articles

Data translation between EDA and MCAD systems

Data translation between EDA and MCAD systems

Formation and Photodissociation of a Jet-Cooled Intramolecular Exciplex in the Bichromophoric EDA System: Multiconformations and Deuteration Effect

The intramolecular exciplex formation and photodissociation in a supersonic free jet have been studied for deuterated anthryl bichromophoric EDA systems 1-(9-anthryl-d8)-3-(m-(N,N-dimethylamino)phenyl)propanes (9-An-d-m-DMA) in comparison with the corresponding undeuterated compounds (9-An-m-DMA). Fluorescence hole burning depletion spectra in the anthryl deuterated 9-An-d-m-DMA suggests the presence of two distinct isomeric conformers. The S1 vibrational energy thresholds for the exciplex formation in the two isomeric forms of the deuterated compounds are considerably smaller than those of the respective undeuterated compounds. The photodissociation of the exciplex leading to the formation of the excited-state anthryl moiety was observed in the excitation of the transient absorption band of the jet-cooled exciplex (Sn−S1). The decay time of the photodissociation-induced anthryl fluorescence is shorter for 9-An-d-m-DMA than for 9-An-m-DMA. These deuteration effects of the anthryl moiety on the formation and photodissociation of the exciplex may be attributed to the role of the vibrational level density of the anthryl moiety in these excited-state reaction dynamics. The shorter decay time of the photodissociation-induced anthryl fluorescence of 9-An-d-m-DMA relative to 9-An-m-DMA is consistent with the conclusion that the emission originates from the vibrationally highly excited S1 anthryl moiety.

Photodissociation of Jet-Cooled Intramolecular Exciplex in 1-(9-Anthryl)-3-(p-(N,N-dimethylamino)phenyl)propane: Formation of Excited-State Anthryl and Deuteration Effect

The jet-cooled intramolecular exciplex formation and photodissociation were examined in deuterated anthryl bichromophoric EDA systems 1-(9-anthryl-d8)-3-(p-(N,N-dimethylamino)phenyl)propane (9-An-d-DMA) in comparison with the undeuterated compound (9-An-DMA) reported previously. The excess vibrational energy threshold for the exciplex formation in the former was considerably smaller than that of the latter. The photodissociation of the jet-cooled exciplex leading to the anthryl moiety fluorescence was observed in the excitation of the transient absorption band of the exciplex (Sn ← S1). It is noteworthy that very short decay times of anthryl fluorescence were observed upon photodissociation of the exciplex. The deuterated effect of the anthryl moiety on the formation and photodissociation of the exciplex may be attributable to the role of the vibrational level density of the anthryl in these excited-state reaction dynamics.

Intramolecular exciplex formation in jet-cooled bichromophoric chain molecules: torsional conformations and excess vibrational energy dependence

Intramolecular exciplex formation and excess vibrational energy dependence were investigated in the bichromophoric EDA systems of several 1-(4-(dialkylamino)phenyl-3-(1- and 9-anthryl)propanes in a supersonic free jet. Fluorescence excitation spectra suggest that two types of ground-state conformers are involved at low He backing pressure (750 Torr). These conformers were tentatively ascribed to trans (t) and gauche (g) conformers concerning the C 1 -C 2 conformation of trimethylene-substituted anthryl. Fluorescence excitation spectra of the t conformer show well-resolved vibrational structures of the S 1 state, while those of g were considerably congested

Exciplex and charge-transfer complex fluorescence in the inter- and intramolecular jet-cooled EDA systems

The exciplex fluorescence was observed in the excitation of the van der Waals complex between 9,10-dicyanoanthracene and naphthlene in supersonic expansion, where no significant vibrational energy dependence was obsreved in the transformation of the complex to the exciplex. In the jet-cooled intramoleculal EDA system of (9,10-dicyano-2-anthryl)(CH 2 ) 3 (1-naphthyl), very broad excitation and diffuse red-shiffed fluorescence spectra were observed

The pulse d.c. photoconductivity of nitrobenzenes in ethereal solutions

The pulse d.c. photoconductivity (PC) of nitrobenzene (NB), orthometa- and para-dinitrobenzenes and symmetric trinitrobenzene in tetrahydrofuran, ethyl ether and 1,4-dioxane has been examined. Measurements of the flash-induced PC revealed that the effects are caused by the monophotonic ionic photodissociation process in these n-π EDA systems and that their magnitude depends on both the polarity of the ethers and the electron acceptor properties of the nitrobenzenes. As expected, the stronger the acceptor and the more polar the ether were the more pronounced were the effects observed. The PC signals were quenched not only by oxygen but surprisingly also by the strong electron π donor pyrene, for which some preliminary results are presented.

Picosecond laser photolysis studies upon charge separation and intersystem crossing processes in some exciplex systems

Mechanisms of charge separation or ionic dissociation of some typical exciplex and excited EDA systems in polar solvents and also electron photoejection from relaxed fluorescence state of an amine molecule in polar solvents which has close connection with the exciplex ionic dissociation phenomena have been discussed on the bais of the results of picosecond laser photolysis studies. Moreover, mechanisms of ultra fast intersystem crossing from singlet charge transfer state to the local triplet state of electron donor or acceptor have been discussed in the case of some exciplex systems referring to the results of picosecond laser photolysis measurements. Simple models which explain these phenomena are proposed.

Radiation‐induced cationic dimerization and polymerization of styrene in methylene chloride solution. I

AbstractRadiation‐induced polymerization of styrene in methylene chloride solution or bulk system was investigated to explain the initiation mechanism of cationic polymerization. It was found that high energy radiation produces polymers and dimers. The main dimers were identified as trans‐1,2‐diphenylcyclobutane, 1‐phenyl‐1,2,3,4‐tetrahydronaphthalene, and 1‐phenyl‐1,2‐dihydronaphthalene. The dimerization procedure was cationic in a pattern similar to that obtained in photoexcited EDA systems. It was shown clearly by product analysis that the bonded dimer cation radical intermediate, which was assumed to be an initiating species of the cationic polymerization, was produced in a radiation‐induced polymerization system. The observed polymerization was composed of two types; cationic and radical, the latter initiated by radical species.