Light-Induced Electron Transfer in Pyropheophytin−Anthraquinone Dyads:  Vectorial Charge Transfer in Langmuir−Blodgett Films

Tkachenko, Nikolai V.; Tauber, Andrei Y.; Hynninen, Paavo H.; Sharonov, and A. Y.; Lemmetyinen, Helge

doi:10.1021/jp983766i

Cited by 31 publications

(36 citation statements)

References 34 publications

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“…This kind of knowledge is important for a proper interpretation and understanding of the ET reaction occurring in the DA compounds incorporated into LB films (cf. the accompanying paper 18 ).…”

Section: Introductionmentioning

confidence: 89%

Light-Induced Electron Transfer in Pyropheophytin−Anthraquinone and Phytochlorin−Anthraquinone Dyads: Influence of Conformational Exchange

et al. 1999

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Novel types of donor-acceptor (DA) molecules, consisting of covalently linked pyropheophytin-anthraquinone (PQ and ZnPQ) and phytochlorin-anthraquinone (PCQ and ZnPCQ) dyads and their diastereomers were studied by means of steady-state and time-resolved fluorescence and absorption spectroscopies. Conformational properties were found to play an important role in understanding the observed photochemical behavior of the flexible diastereomers PQ1,2 and ZnPQ1,2 DA dyads. The more compact conformers undergo fast (in a few picoseconds or less) light-induced electron transfer (ET) from the singlet excited state. The most extended conformers, however, possess a separation between the donor and acceptor, which is too long to allow relaxation of the singlet exited state via ET. A fast conformational exchange between the open and folded conformers was observed in a variety of solvents and was found to be crucial for the observed electron-transfer properties of the flexible DA dyads studied. The more rigid DA systems, PCQ and ZnPCQ, exhibited electron-transfer properties that could well be elucidated in the frame of the Marcus theory.

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Section: Introductionmentioning

confidence: 89%

Light-Induced Electron Transfer in Pyropheophytin−Anthraquinone and Phytochlorin−Anthraquinone Dyads: Influence of Conformational Exchange

et al. 1999

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“…47 Although the samples showed clear photovoltage signals, the lifetimes and profiles of the signals depended strongly on the deposition direction and the concentration of the dyad in the matrix material. A similar irrational behavior was observed in fluorescence experiments as well.…”

Section: Photovoltage Studies Of Electron Transfer In Single D-a Pairmentioning

confidence: 97%

“…41,43,47,50,[55][56][57][58] The method is based on measurements of the Maxwell displacement charge by placing the molecular layer into a flat capacitor. 59,60 The molecular film layer or layers are deposited upon a semitransparent electrode, such as indium tin oxide (ITO), and covered by a top electrode, which can be a drop of a liquid metal, e.g.…”

Section: Photovoltage Studies Of Electron Transfer In Single D-a Pairmentioning

confidence: 99%

Photoinduced intra- and intermolecular electron transfer in solutions and in solid organized molecular assemblies

Lemmetyinen

Tkachenko

Efimov

et al. 2011

Phys. Chem. Chem. Phys.

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The present paper highlights results of a systematic study of photoinduced electron transfer, where the fundamental aspects of the photochemistry occurring in solutions and in artificially or self-assembled molecular systems are combined and compared. In photochemical electron transfer (ET) reactions in solutions the electron donor, D, and acceptor, A, have to be or to diffuse to a short distance, which requires a high concentration of quencher molecules and/or long lifetimes of the excited donor or acceptor, which cannot always be arranged. The problem can partly be avoided by linking the donor and acceptor moieties covalently by a single bond, molecular chain or chains, or rigid bridge, forming D-A dyads. The covalent combination of porphyrin or phthalocyanine donors with an efficient electron acceptor, e.g. fullerene, has a two-fold effect on the electron transfer properties. Firstly, the electronic systems of the D-A pair result in a formation of an exciplex intermediate upon excitation both in solutions and in solid phases. The formation of the exciplex accelerates the ET rate, which was found to be as fast as >10(12) s(-1). Secondly, the total reorganization energy can be as small as 0.3 eV, even in polar solvents, which allows nanosecond lifetimes for the charge separated (CS) state. Molecular assemblies can form solid heterogeneous, but organized systems, e.g. molecular layers. This results in more complex charge separation and recombination dynamics. A distinct feature of the ET in organized assemblies is intermolecular interactions, which open a possibility for a charge migration both in the acceptor and in the donor layers, after the primary intramolecular exciplex formation and charge separation in the D-A dyad. The intramolecular ET is fast (35 ps) and efficient, but the formed interlayer CS states have lifetimes in microsecond or even second time domain. This is an important result considering possible applications.

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“…Thin films of these materials find technological applications in the field effect transistors, light-emitting diodes and photo-voltaic devices [5,6]. For such applications, the molecules must be well ordered in the thin film [7], since the structure and morphology of the film are important in fabricating the devices. Amphiphilic organic molecules can self-assemble at air-water interface to yield well ordered monolayer known as Langmuir monolayer.…”

Section: Introductionmentioning

confidence: 99%

Transition in nanoscale electrical conductivity in the Langmuir-Blodgett film of a novel liquid crystalline oligomer

et al. 2020

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We have studied the nanoscale electrical conductivity of a monolayer film of a novel star shaped liquid crystalline molecule, hexatriphenylene substituted anthraquinone (AQD6). The molecule has a central core of electron deficient anthraquinone moiety connected to six electron rich triphenylene moieties by flexible alkyl chains. The monolayer formed at air-water interface was transferred onto the solid substrates by Langmuir-Blodgett (LB) technique and its surface topography was imaged using an atomic force microscope (AFM). The limiting area obtained from the surface pressure-area per molecule isotherm and the topography of the AFM images suggest that the anthraquinone moiety of the AQD6 molecule is organized in face-on configuration on the substrate and the triphenylene moieties are in edge-on configuration extended away from the substrate. We have studied the electrical conductivity of the AQD6 monolayer deposited on gold coated silicon substrate using a current sensing AFM. Analysis of current (I)−voltage (V ) characteristics of the metal-monolayer film-metal junction showed a transition from direct tunneling to an injection tunneling. Further, we have estimated the barrier height and the effective mass of electron in the metal-monolayer film-metal junction.

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Light-Induced Electron Transfer in Pyropheophytin−Anthraquinone Dyads: Vectorial Charge Transfer in Langmuir−Blodgett Films

Cited by 31 publications

References 34 publications

Light-Induced Electron Transfer in Pyropheophytin−Anthraquinone and Phytochlorin−Anthraquinone Dyads: Influence of Conformational Exchange

Light-Induced Electron Transfer in Pyropheophytin−Anthraquinone and Phytochlorin−Anthraquinone Dyads: Influence of Conformational Exchange

Photoinduced intra- and intermolecular electron transfer in solutions and in solid organized molecular assemblies

Transition in nanoscale electrical conductivity in the Langmuir-Blodgett film of a novel liquid crystalline oligomer

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