Intramolecular excitation energy

Valeur B. (1989) Intramolecular Excitation Energy Transfer in Bichromophoric Molecules, in Jameson D. and Reinhart G. D. (Eds), Fluorescent Biomolecules,... 

The number of delocalizable electrons can be increased. This is possible because the activation energy of the dark conduction, like the intramolecular excitation energy of the electrons, decreases with increasing number N of delocalizable electrons in agreement with the electron gas theory. Hence, if the relationship between and N for the open [Eq. (48)] and cyclic [Eq. (49)] electron systems is represented graphically, the values obtained from conductivity measurements will generally lie between the two curves see e.g. 13>64>. 

Valeur B. Intramolecular excitation energy transfer in bichro-mophoric molecules-fundamental aspects and applications. In Fluorescence Biomolecules Methodologies and Applications. Jameson DM, Reinhart GD, eds. 1989. Plenum Press, New York, pp. 269-303. 

Figure 2.11 Potential energy surface for an ( -l)-dimensional seam of intersection in the intramolecular excitation-energy transfer of BOD.

Behr etal. studied the photoreaction of tetracyclic trienedione 139, which was prepared by the thermal addition of o-benzoquinone to barrelene (15%). Irradiation of 139 in deoxygenated methylcy-clohexane (MCH) or chloroform with benzophenone at 366 nm afforded the cage compound 140 (25%). The first step of this cycloaddition may be the formation of a biradical by a pathway similar to that of the oxa-di-Jt-methane rearrangement from the lowest (n 71 ) state (Scheme 25). Since the excitation energy of the a-dicarbonyl unit in 139 [EA (biacetyl) = 0.72 eV] is similar to that of 2-cyanonaphthalene, intramolecular excitation energy transfer from dione to diene similar to that from 2-cyanonaphthalene... 

Callegari A, Rebstein J, Muenter J S, Jost R and Rizzo T R 1999 The spectroscopy and intramolecular vibrational energy redistribution dynamics of HOCI in the u(OH) = 6 region, probed by infrared-visible double resonance overtone excitation J. Chem. Phys. 111 123-33... 

Haas, E. and Steinberg, I. (1984). Intramolecular dynamics of chain molecules monitored by fluctuations in efficiency of excitation energy transfer. Biophys. J. 46, 429-37. 

M. Kupryszewska, I. Gryczynski, and A. Kawski, Intramolecular donor-acceptor separations in methionine- and leucine-enkephalin estimated by long-range radiationless transfer of singlet excitation energy, Photochem. Photobiol. 36, 499-502 (1982). 

In order to avoid complications caused by excitation energy transfer between tryptophan residues, most investigations have been performed with proteins containing one tryptophan residue per molecule. When studying protein solutions, there are difficulties in separating the effects of rotation of entire protein molecules and of the chromophores themselves relative to their environment in the protein matrix. It is usually assumed that intramolecular motions are more rapid and manifest themselves as short-lived components of anisotropy decay curves or in depolarization at short emission lifetimes. 

A number of cyano-bridged complexes are included here even though they strictly do not fall in the general family-type defined for the section. The syntheses and photophysical properties of [(NC)(bpy)2Ru(/r-NC)Cr(CN)5] and [(NC)5Cr(Ai-CI Ru(bpy)2(M-NC)Cr(CN)5] have been described. Absorption of visible light by the Ru(bpy)2 unit results in phosphorescence from the Cr(CN)g luminophore, and the results evidence fast intramolecular exchange energy transfer from the MLCT state of the Ru(bpy)2 chromophore to the doublet state of the Cr -based unit. Time-resolved resonance Raman and transient UV-vis absorption spectroscopies have been employed to investigate the MLCT excited states of [(NC)(bpy)2Ru(//-CN)Ru (bpy)2(CN)], [(NC)(bpy)2Ru(//-CN)Ru(phen)2(CN)]+, [(NC)(phen)2Ru(//-CN)Ru (bpy)2(CN)]+, [(NC)(bpy)2... 

Thus several groups of slow electrons subsequently appear despite a continuous increase in the energy of the incident photons. This can only mean that at definite values of the photon energy, a substantial part of it is spent in an intramolecular excitation process (Table III). 

The intramolecular excitation of a sequence of definite electronic levels in the positive ion is the most probable explanation of the appearance of slow electrons. The differences between the electron kinetic energies for the subsequent maxima in the distribution curves are a measure of the discrete values of the excitation energy absorbed by the molecule in the process of photoionization. Table III gives a summary of these values. 

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