Electron intramolecular

Three dimensional X-ray diffraction data point to a largely planar structure in all of the molecules studied this ensures optimum conjugation (overlapping of the TT-electrons). Intramolecular hydrogen bonds probably contribute considerably towards supporting the planar conformation. 

At this stage any skepticism invoking a two-electron (intramolecular) concerted mechanism to explain the formation... 

The superconducting ability of [M(dmit)2] complexes, see Fig. 9, has prompted experimental and theoretical vibrational studies of [Ni(dmit)2]z and [Pd(dmit)2]z complexes (z is in the range 0-2—), in order to understand the mechanism of superconductivity in terms of electron-intramolecular and electron-intermolecular vibrational couplings (14, 21). These studies have... 

SO is found in various vertebrate liver tissues and catalyzes the two-electron oxidation of sulfite to sulfate coupled to the reduction of two molecules of oxidized Cyt c. It contains molybdopterin and b-heme cofactors in separate domains connected by a polypeptide bridge, analogous to Fcyt b. The smaller N-terminal heme domain resembles cytochrome b the C-terminal domain contains Mo(VI) and catalyzes sulfite oxidation coupled to oxo group transfer. Two one-electron intramolecular ET steps, each followed by ET to Cyt c, complete the catalytic cycle. 

The most systematic study of the effects of addition of redox groups to the periphery of porphyrin rings were reported by Anson and coworkers [97]. Their approach involved coordination of [Ru(NH3)5(OH2)]2+, an electron donor species with a relatively positive redox potential (see below), to each of the pyridyl groups in CoTPyP (see Figure 3.55), a species denoted as Ru(4)CoTPyP, to allow, in principle, injection of four electrons intramolecularly into 02 bound to the Co center to generate water as the product [98]. 

Kato, T. and Yamabe, T., Electron-intramolecular phonon coupling and possible superconductivity in negatively charged coronene and corannulene, J. Chem. Phys., 117, 2324, 2002. 

Kato, T. and Yamabe, T., Electron-intramolecular-vibration interactions in positively... 

The range of frequencies is determined by a number of factors that are now well understood in terms of the mass, geometric, electronic, intramolecular, and intermolecular effects (for an introductory discussion of these effects see Chapter 8W, IR section. Part III A). 

When attempts are made to be more quantitatively close to the experimental data the limitations of the quantum chemical methods so far used are immediately and disappointingly perceived. The disagreement between calculated and experimental data even for the simplest polyconjugated systems (e.g. polyenes and Polyacetylene) for basic quantities such as energy gap, band width, ionisation potentials and molecular conformations are remarkable and indicate that the present methods need to be improved to represent satisfactorily the electronic intramolecular phenomena. 

Tannor D J, Rice S A and Weber P M 1985 Picosecond CARS as a probe of ground electronic state intramolecular vibrational redistribution J. Chem. Phys. 83 6158... 

This is no longer the case when (iii) motion along the reaction patir occurs on a time scale comparable to other relaxation times of the solute or the solvent, i.e. the system is partially non-relaxed. In this situation dynamic effects have to be taken into account explicitly, such as solvent-assisted intramolecular vibrational energy redistribution (IVR) in the solute, solvent-induced electronic surface hopping, dephasing, solute-solvent energy transfer, dynamic caging, rotational relaxation, or solvent dielectric and momentum relaxation. 

In this chapter we shall first outline the basic concepts of the various mechanisms for energy redistribution, followed by a very brief overview of collisional intennoleciilar energy transfer in chemical reaction systems. The main part of this chapter deals with true intramolecular energy transfer in polyatomic molecules, which is a topic of particular current importance. Stress is placed on basic ideas and concepts. It is not the aim of this chapter to review in detail the vast literature on this topic we refer to some of the key reviews and books [U, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, and 32] and the literature cited therein. These cover a variety of aspects of tire topic and fiirther, more detailed references will be given tliroiighoiit this review. We should mention here the energy transfer processes, which are of fiindamental importance but are beyond the scope of this review, such as electronic energy transfer by mechanisms of the Forster type [33, 34] and related processes. 

Marzocchi M P, Mantini A R, Casu M and Smulevich G 1997 Intramolecular hydrogen bonding and excited state proton transfer in hydroxyanthraquinones as studied by electronic spectra, resonance Raman scattering, and transform analysis J. Chem. Phys. 108 1-16... 

So far we have exclusively discussed time-resolved absorption spectroscopy with visible femtosecond pulses. It has become recently feasible to perfomi time-resolved spectroscopy with femtosecond IR pulses. Flochstrasser and co-workers [M, 150. 151. 152. 153. 154. 155. 156 and 157] have worked out methods to employ IR pulses to monitor chemical reactions following electronic excitation by visible pump pulses these methods were applied in work on the light-initiated charge-transfer reactions that occur in the photosynthetic reaction centre [156. 157] and on the excited-state isomerization of tlie retinal pigment in bacteriorhodopsin [155]. Walker and co-workers [158] have recently used femtosecond IR spectroscopy to study vibrational dynamics associated with intramolecular charge transfer these studies are complementary to those perfomied by Barbara and co-workers [159. 160], in which ground-state RISRS wavepackets were monitored using a dynamic-absorption technique with visible pulses. 

Williams R M, Zwier J M and Verhoeven J W 1995 Photoinduced intramolecular electron transfer in a bridged Cgg (acceptor)-aniline (donor) system. Photophysical properties of the first active fullerene diad J. Am. Chem. See. 117 4093-9... 

Guldi D M, Maggini M, Scorrano G and Prato M 1997 Intramolecular electron transfer in fullerene/ferrocene based donor-bridge-acceptor dyads J. Am. Chem. See. 119 974-80... 

In Debye solvents, x is tire longitudinal relaxation time. The prediction tliat solvent polarization dynamics would limit intramolecular electron transfer rates was stated tlieoretically [40] and observed experimentally [41]. 

Early studies showed tliat tire rates of ET are limited by solvation rates for certain barrierless electron transfer reactions. However, more recent studies showed tliat electron-transfer rates can far exceed tire rates of diffusional solvation, which indicate critical roles for intramolecular (high frequency) vibrational mode couplings and inertial solvation. The interiDlay between inter- and intramolecular degrees of freedom is particularly significant in tire Marcus inverted regime [45] (figure C3.2.12)). 

Figure C3.2.12. Experimentally observed electron transfer time in psec (squares) and theoretical electron transfer times (survival times, Tau a and Tau b) predicted by an extended Sumi-Marcus model. For fast solvents tire survival times are a strong Emction of tire characteristic solvent relaxation dynamics. For slower solvents tire electron transfer occurs tlirough tire motion of intramolecular degrees of freedom. From [451.

Kosower E M and Huppert D 1983 Solvent motion controls the rate of intramolecular electron transfer Chem. Phys. Lett. 96 433-5... 

Minimal END has also been applied to a model system for intramolecular electron transfer. The small triatomic system LiHLi is bent C2v structure. But the linear structure presents an unrestricted Haiti ee-Fock (TJHF) broken symmetry solution with the two charge localized stmctures... 

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