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An investigation is conducted to elucidate the photoinduced electron-transfer kinetics and charge-transfer emission spectra of two U-shaped DBA molecules in various aromatic solvents of varying polarities by measuring electron-transfer rates. The empirical outcomes exhibit the operation of the through-pendant-group mechanism of electron transfer in the pendant-containing U-shaped systems of the U-shaped DBA molecules.

The electron-transfer rate constant is measured in two U-shaped donor-bridge-acceptor molecules over a wide range of temperature in acetonitrile and N-methylacetamide (NMA). The electron-transfer rate at high temperature can be well described by a nonadiabatic model of the reaction but at low temperatures the rate in NMA becomes controlled by the solvent.

The electron transfer is a basic chemical process that has a lot of scientific significance and studies are conducted to evaluate the electron tunneling efficiency between electron donor and acceptor groups using noncovalent molecular contacts. Experimental electron transfer rate constants and reaction free energies are used to calibrate a molecular based model that defines the solvation energy.

Photoinduced charge separation and recombination in a giant U-shaped tetrad is discussed.

C60 unit undergoes Diels-Alder reaction with 1,3-dienes to form the ball-and-chain system having C60 and donor-substituted aryl chromophores linked through a rigid saturated polynorbornane-bicyclo(2.2.0)hexane hydrocarbon bridge. A similar reaction of bis(diene) forms soluble dumb-bell system having two C60 chromophores. The norbornylogous bridge transfers electrons and energy by a strong through-bond coupling mechanism. Ab initio, semi-empirical, and molecular mechanics show that activation barriers between folded and extended conformers have a consistent value.

Exciton interactions in rigidly linked dinaphthyl molecules were evaluated basing on through-space and through-bond effects. Resonance splitting of naphthalene was shown and found to be greater than predicted by the usual dipole-dipole model. The role of the through-space interchromophore orbital was found to be insignificant while the through-bond interaction exerts an important role in the efficient delocalization of the excitation observed.

Investigations aimed at designing a unique kind of derivative of C60 by building 'ball-and-chain' mechanisms, where the C60 unit and another functional group, G, are connected to a rigid polycyclid chain or bridge, used the Diels-Alder reaction between C60 and the unique bridge diene 6 to synthesize a 'ball-and-chain' molecule (2) where the chain consists of a rigid polynorbornyl-bicyclo(2.2.0)hexyl bridge used in the building of many donor-bridge-acceptor mechanisms. The rational construction of unique molecular electronic equipment could use the photophysical, chemical and electrical characteristics of these 'ball-and-chain' bichromophoric systems as materials.

Presents a study on intramolecular electron and energy transfer using the synthesis of bichromorphic ball and chain systems based on buckminsterfullerene. Analogous reaction affords soluble dumbbell system; Discussion on reduction potential shift of the systems.

The electron-transfer rate constant is measured in two U-shaped donor-bridge-acceptor molecules over a wide range of temperature in acetonitrile and N-methylacetamide (NMA). The electron-transfer rate at high temperature can be well described by a nonadiabatic model of the reaction, but at low temperatures the rate in NMA becomes controlled by the solvent. The results are discussed in terms of theoretical models for the change in reaction mechanism and its dependence on the solute-solvent frictional coupling. [ABSTRACT FROM AUTHOR]

This work explores electron transfer through nonbonded contacts in two U-shaped DBA molecules 1DBA and 2DBA by measuring electron-transfer rates in organic solvents of different polarities. These molecules have identical U-shaped norbornylogous frameworks, 12 bonds in length and with diphenyldimethoxynaphthalene (DPMN) donor and dicyanovinyl (DCV) acceptor groups fused at the ends. The U-shaped cavity of each molecule contains an aromatic pendant group of different electronic character, namely p-ethylphenyl, in 1DBA, and p-methoxyphenyl, in 2DBA. Electronic coupling matrix elements, Gibbs free energy, and reorganization energy were calculated from experimental photophysical data for these compounds, and the experimental results were compared with computational values. The magnitude of the electronic coupling for photoinduced charge separation, ∣VCS∣ in 1DBA and 2DBA were found to be 147 and 274 cm-1, respectively, and suggests that the origin of this difference lies in the electronic nature of the pendant aromatic group and charge separation occurs by tunneling through the pendant group, rather than through the bridge. 2DBA, but not 1DBA, displayed charge transfer (CT) fluorescence in nonpolar and weakly polar solvents, and this observation enabled the electronic coupling for charge recombination, ∣VCR∣ in 2DBA to be made, the magnitude of which is ∼ 500 cm-1, significantly larger than that for charge separation. This difference is explained by changes in the geometry of the molecule in the relevant states; because of electrostatic effects, the donor and acceptor chromophores are about 1 Å closer to the pendant group in the charge-separated state than in the locally excited state. Consequently the through-pendant-group electronic coupling is stronger in the charge-separated state—which controls the CT fluorescence process—than in the locally excited state—which controls the charge separation process. The magnitude of ∣VCR∣ for 21DBA is almost 2 orders of magnitude greater than that in DMN-12-DCV, having the same length bridge as for the former molecule, but lacking a pendant group. This result unequivocally demonstrates the operation of the through-pendant-group mechanism of electron transfer in the pendant-containing U-shaped systems of the type 1DBA and 2DBA. [ABSTRACT FROM AUTHOR]

U-shaped donor–bridge–acceptor molecules with different electronic couplings have been investigated as a function of temperature in solvents with slow polarization relaxation, in particular, N-methylacetamide (NMA) and N-methylpropionamide (NMP). At high temperature, the electron-transfer rate is well described by a nonadiabatic model; however, the rate at low temperature is controlled by the solvent friction. The change of the electron-transfer mechanism is discussed and compared with theoretical models. [ABSTRACT FROM AUTHOR]