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Titolo: ELECTRONTRANSFER AND ENERGYTRANSFER THROUGH BRIDGED SYSTEMS .3. TIGHTBINDING LINKAGES WITH ZERO OR NONZERO ASYMPTOTIC BANDGAP
Autore: REIMERS JR; HUSH NS;
 Indirizzi:
 UNIV SYDNEY,DEPT PHYS & THEORET CHEM SYDNEY NSW 2006 AUSTRALIA UNIV SYDNEY,DEPT BIOCHEM SYDNEY NSW 2006 AUSTRALIA
 Titolo Testata:
 Journal of photochemistry and photobiology. A, Chemistry
fascicolo: 13,
volume: 82,
anno: 1994,
pagine: 31  46
 SICI:
 10106030(1994)82:13<31:EAETBS>2.0.ZU;2Q
 Fonte:
 ISI
 Lingua:
 ENG
 Soggetto:
 BROOKER POLYMETHINECYANINE CATIONS; NEGATIVEDEFECT TRANSPOLYACETYLENE; TUNNELING MATRIXELEMENTS; THROUGHBOND INTERACTIONS; CHARGEDENSITY WAVE; BIS(PENTAAMMINERUTHENIUM) COMPLEXES; FINITELENGTH; SOLITONS; MOLECULES; PROTEINS;
 Tipo documento:
 Article
 Natura:
 Periodico
 Settore Disciplinare:
 Science Citation Index Expanded
 Citazioni:
 37
 Recensione:
 Indirizzi per estratti:



 Citazione:
 J.R. Reimers e N.S. Hush, "ELECTRONTRANSFER AND ENERGYTRANSFER THROUGH BRIDGED SYSTEMS .3. TIGHTBINDING LINKAGES WITH ZERO OR NONZERO ASYMPTOTIC BANDGAP", Journal of photochemistry and photobiology. A, Chemistry, 82(13), 1994, pp. 3146
Abstract
The simplest analytical model for bridgeassisted electron or hole transfer processes is that of McConnell. It gives an approximate solution for nonresonant transfer through a bridge described by a simple Huckel hamiltonian embodying no asymptotic band gap. We investigate the analytical solution of this problem, recently obtained by Evenson and Karplus, for the weak donor/acceptortobridge coupling limit. Exponential falloff of the coupling with increasing bridge length is predictedto occur in all regions of the parameter space, except that which is extremely close to or within the resonance region; this result is consistent with McConnell's equation, but applies far more generally, and new and more accurate limits for the validity of the McConnell equation are derived. The analysis is extended to consider bridges described by a Huckel hamiltonian containing two different intrabridge nearestneighbour coupling parameters, as is appropriate for a sigmabonded bridge or a pibonded bridge with alternating single and double bonds. Such systems contain a finite asymptotic band gap between occupied and virtual bridge orbitals, and possibly also one or two nonbonding levels. Resonance conditions are obtained, as are analytical solutions for the coupling when the donor and acceptor levels lie either outside theoccupied and virtual bands or within the band gap; exponential falloff is again predicted away from the resonances, but this may be difficult to achieve inside a narrow band gap. Analogous equations to McConnell's are derived and the effects of all approximations used, includingthat of an effective twolevel hamiltonian, are considered numerically. Bridges with an odd number of functions are shown to contain one eigenstate, a nonbonding level, at the centre of the band gap, and resonance with this level must also be avoided in order to obtain regular exponential falloff. However, rather than to avoid such situations, our ultimate goal is to design systems which are resonant or nearly resonant in which the coupling decreases slowly or even oscillates with increasing bridge length. Oddlength bridges such as Brookerdye ions, with their extra nonbonding level and necessarily smaller band gaps, are thus expected to conduct considerably better than systems studied so far which always tend to be evenlength bridges.
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Documento generato il 24/11/20 alle ore 11:27:10