Nanosecond transient absorption spectroscopy was used to measure back-electron-transfer rate constants kb in the series [(4,4'-(X)2bpy'-)Re1(CO)3(py-PTZ'+)]+ with X = C02Et, C(O)NEt2, H, Me, MeO, NH2 and also the 2,2'-bipyrazine (bpz) and 3,4,7,&tetramethyl-1,lO-phenanthroline (Medphen) complexes in propylene carbonate (PC). These states are formed following Re' -(4,4'-(X)zbpy) excitation and -PTZ -Re" electron transfer. The reactions occur in the Marcus inverted region and In kb varies linearly with AGO as predicted by the energy gap law. In the complexes with X = Me, MeO, and Me4phen, weak, ground-state absorption bands corresponding to ligand-to-ligand charge transfer (LLCT) transitions between py-PTZ and 4,4'-(X)2bpy or Me4phen were detected. These bands are not present in the spectra of the corresponding 4-ethylpyridine model complexes. From the Hush analysis of the ground state absorption bands, the electron-transfer matrix elements Hat, are 44 cm-l (X = Me), 51 cm-l (X = MeO), and 61 cm-l (Me4phen) with A,-,' = 0.4 eV in PC.XO' is the sum of the solvent reorganizational energy and the coupled low frequency vibrations treated classically. By combining Hab, A,-,' , and kinetic parameters obtained in the kinetic study, it is possible to calculate kb from a form of the energy gap law. The calculated values for kb are within a factor of 10 of the experimental values, e.g., kb = 3.1 X lo's-l, kb(ca1c) = 3.0 X lo8 s-l for x = Me. These results point to the feasibility of using absorption band measurements routinely to calculate electron-transfer rate constants in the inverted region.Hush has shown1 that in mixed-valence complexes and, more generally, for donor-acceptor pairs, quantitative relationships exist between optical and thermal electron transfer. In the classical limit with weak electronic coupling, the free energy of activation (AG*) is related to the absorption band energy ea^), thereorganizational energy (A), and the freeenergychange (AGO) bylJ The delocalization energy (Hab) from electronic coupling between donor and acceptor is related to the integrated absorption band intensity. For a Gaussian band, this relationship is given by' where e, , , is the molar absorptivity coefficient, ; , , , is the absorption maximum in cm-1, A i 1 p is the full width at halfheight in cm-I, and r is the distance separating the redox sites in angstroms. In principle, these relationships allow simple absorption band measurements to be used to calculate rate constants for electron transfer. This has been tested experimentally3 in a few cases in the normal region by comparing absorption band measurements with direct observation of electron transfer rate constants. Gould et al.3e have used emission spectra and quantitative measurement of radiative decay to calculate back electron transfer rate constants following photoexcitation of donor-acceptor pairs. We report here an application of the Hush approach to electron transfer in the inverted region in a molecular assembly.In earlier papers4 the role of driving force, solvent,...

Competitive energy and electron transfer occur following excitation of the chromophore-biquencher [Re I (MebpyCH 2 OCH 2 An)(CO) 3 (MQ + )](PF 6 ) 2 (MebpyCH 2 OCH 2 An is 4-[(9-anthrylmethoxy)methyl]-4′-methyl-2,2′-bipyridine; MQ + is N-methyl-4,4′,-bipyridinium ion). Following excitation with a 392-nm, 4-ns laser pulse in 1,2-dichloroethane (DCE), the initial excited state energy is distributed in a ∼2:1 ratio between 3 An* and the lower lying Re II (MQ ‚ ) metal-to-ligand charge transfer (MLCT) excited state. The appearance of the two states was monitored by transient absorption spectroscopy, which detected the triplet-triplet band for 3 An* at λ max ) 420 nm (τ ) 35 ( 2 µs, k ) (2.9 ( 0.2) × 10 4 s -1 ) and a π f π* band of MQ • at 610 nm (τ ) 37 ( 2 ns, k ) (2.7 ( 0.2) × 10 7 s -1 ). These states result from a competitive partitioning in the initial excited state or states. They do not interconvert to any significant degree on the time scale of the shorter lived, higher energy Re II (MQ*) state.

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In this paper, an intelligent electric power steering system is proposed to replace a traditional hydraulic power steering system and implemented in a real light hybrid electric vehicle. An intelligent fuzzy control algorithm is applied to yield basic assist logic, return compensation logic, damping compensation logic, and inertia compensation logic in an assist steering system. According to steering wheel angle and vehicle speed, the proposed fuzzy inference logic can provide needed assist motor current. Under experts' knowledge of fuzzy control, the electric power steering system can satisfy smooth driving. In addition, four driving modes are designed to complete the control strategy. Different driving modes have corresponding fuzzy inference strategies to complete the assist and compensation logic. Finally, the intelligent electric power steering system with a new 12V/500W EPS motor is applied in a real light hybrid electric vehicle. Experimental results demonstrate that the proposed method is reasonable and feasible.

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