Hydrocarbon bridges

Williams R M, Koeberg M, Lawson J M, An Y-Z, Rubin Y, Paddon-Row M N and Verhoeven J W 1996 Photoinduced electron transfer to Cgg across extended 3- and 11 a-bond hydrocarbon bridges creation of a long-lived charge-separated state J. Org. Chem. 61 5055-62... 

We touch here on the distance dependence of the MMCT rate. This problem is widely under study at the moment [130]. This rate depends on the distance r according to exp( — fir). The value of p seems to be in between 1.1 and 1.4 A Elegant work has been performed by Hush, Paddon-Row and Verhoeven [131] who studied molecules in which the reactants are separated by rigid saturated hydrocarbon bridges of various lengths. 

Shephard MJ, Paddon-Row MN, Jordan KD (1993) Electronic coupling through saturated hydrocarbon bridges. Chem Phys 176 289-304... 

Concept The rates of long-range electron transfer (ET) and excitation energy transfer (EET) processes between a pair of chromo-phores (redox couple) may be strongly facilitated by the presence of an intervening non-conjugated medium, such as saturated hydrocarbon bridges, solvent molecules and n-stacks, e.g.,... 

Electron Transfer Mediated by Saturated Hydrocarbon Bridges... 

In summary, electron transfer dynamics, mediated through saturated hydrocarbon bridges and proteins, displays a surprisingly weak distance dependence behaviour (/J = 0.8-12 A 1), compared to that predicted for a pure through-space mechanism (P 3.0 A1). 

An important question remains to be answered although the phenomenological P value appears to be fairly insensitive to the nature of the hydrocarbon bridge, does it necessarily follow that Pei, for the distance dependence of the electronic coupling, Vd, should likewise display a similar insensitivity Extracting Vd values, and hence 3d, from experimental ET rate data is presently fraught with difficulties and uncertainties. An alternative approach to this problem is to calculate the couplings. A par-... 

R. M Williams, M Koebeig, J. M Lawson, Y. Z. An, Y. Rubin, M N. Paddon-Row, J. W. Verhoeven, Photoin-duced Electron Transfer to C-60 Across Extended 3-and 11-Bond Hydrocarbon Bridges - Creation of a Long-Lived Chaige-Separated State , J. Org. Chem 1996, 61,5055-5062... 

J. Kroon, A. M. Oliver, M. N. Paddon-Row, J. W. Verhoeven, Observation of a Remarkable Dependence of the Rate of Singlet-Singlet Energy Transfer on the Configuration of the Hydrocarbon Bridge in Bichromophoric Systems , J. Am Chem Soc 1990,112, 4868-4873. 

Fiereby, Vq refers to the maximal electronic coupling element and p is the decay coefficient factor (damping factor), which depends primarily on the nature of the bridging molecule. From the linear plot of In ETmax versus R the p value is obtained as 0.60 A [47]. This p value is located within the boundaries of nonadiabatic ET reactions for saturated hydrocarbon bridges (0.8-1.0 A ) and unsaturated phenylene bridges (0.4 A ) [1-4,54,55]. 

The relative concentrations of several types of hydrocarbon bridges, namely methylene(-CH2-), ethylene(-CH2-CH2-), methyl methylene (-CH(CH3)-), methyl ethylene(-CH(CH3)-CH2-), ethyl methylene (-CH(CH2CH3)-), and propyl methylene (-CH(CH2CH2CH3)-) in the fresh and oxidized San Juan coal are compared in Table... 

Air oxidation of coal causes a significant decrease in the concentration of aliphatic bridges as determined by acid-catalyzed transalkylation of coal with phenol. Infrared analysis of the raw and oxidized coals indicate that the hydrocarbon bridges are converted to carbonyl groups. Plausible explanations have been offered for the formation of carbonyl groups from aliphatic bridges. 

Disulfide-containing peptides still present a difficulty, in that there is the potential for the catalytic desulfuration of the disulfide bridge during the dehalogenation of the Phe(3,5-I2,4-NH2) residue 93 Replacement of the disulfide bridge by a hydrocarbon bridge, when tolerated, represents a plausible solution 31 ... 

The dinuclear complex (CpNiCO)2 is a source of NiCp fragments. Their addition to clusters occurs with Os3(CO),2 to form 88 (163) or with the hydrocarbon bridged ruthenium clusters 89 to form 90 (164). The clusters... 

Binding energy, pentacarbonyliron, 6, 3 Binuclear complexes bis-Cp titanium halides, 4, 522 with Ni-M and Ni-C cr-bonds heterometallic clusters, 8, 115 homometallic clusters, 8, 111 Binuclear dicarbonyl(cyclopentadienyl)hydridoiron complexes, with rand C5 ligands, 6, 178 Binuclear iridium hydrides, characteristics, 7, 410 Binuclear monoindenyl complexes, with Ti(IV), 4, 397 Binuclear nickel(I) carbonyl complexes, characteristics, 8, 13 Binuclear osmium compounds, with hydrocarbon bridges without M-M bonds, 6, 619... 

Binuclear ruthenium compounds, with hydrocarbon bridges without M-M bonds, 6, 619... 

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