Photoinduced electrochromism

PHOTOINDUCED ELECTROCHROMISM IN LB FILMS CONTAINING ION-PAIR CHARGE-TRANSFER COMPLEXES... 

Optical waveguide detection of photoinduced electrochromism in ultra-thin films... 

Figure 28 Schematic representa- Figure 29 Changes in the OWG absorbance of PV2+(TFPB )2 tion of the OWG system for detect- thin films of various thickness during IPCT excitation ing photoinduced electrochromism (a) 10.0, (b) 40.4, (c) 64.9, (d) 955, and (e) 179.6 nm. of ultrathin films (S) in the evacuation chamber shown in an inset.

IV. PHOTOINDUCED ELECTROCHROMISM OF ION-PAIR CHARGE-TRANSFER COMPLEXES IN VARIOUS MICROENVIRONMENTS... 

Steady-state photoinduced electrochromism was achieved in organic solutions [34,35], microcrystals [36,37], LB films [7,8,38,39], and polymer films [40- 48] which was due only to the photoinduced electron transfer reaction via the excited state of specific IPCT complexes [49,50], The photochemical coloring and the thermal fading due to the reverse electron transfer were highly reversible in a deaerated atmosphere in all systems [7,8,34 18], The lifetime of colored (blue)... 

Figure 12 Schematic representation of photoinduced electrochromism in 4,4,-bipyri-dinium IPCT salts.

B. Optical Waveguide Detection of Photoinduced Electrochromism in Ultrathin Films... 

Figure 17 Schematic representation of the OWG system for detecting photoinduced electrochromism of ultrathin films (S) in the evacuation chamber shown in the inset.

Polyacrylamide gel films containing Fe(III) dipyridinium complex as an electrochromic component were usefiil as the substrate for the formation of photographic images when coated on a CdSe film [48]. Poly-Re (CO) 3 (vbpy)Cl-coa ted n-MoSc2 also allowed photoinduced electrochromic recordings in the coated polymer layer under anodic bias [49]. The images produced are easily erased by applying the reverse bias to the polymer-coated semiconductor electrodes. 

Kinetics of the Q Qb QaQb reaction. The kinetics of electron transfer from to Qg following a single laser flash were determined in chromatophores by following the photoinduced electrochromic shift of the L-side bacteriopheophytin, observed at 760 nm [19]. Figure 2 shows these transients measured in chromatophores of the wild-type and revertant strains, corrected for the instantaneous rise and slow decay of P" " (Tiede and Hanson, this volume). The transients detected following formation of the initial P Qa state in the double mutant differed dramatically from those shown in Figure 2. TTie relatively slow rise and decay detected in the double mutant suggested forward and back rate constants of about 110 s and 50 s" respectively, for the Q Qb Qa b equilibrium. It is difficult to be certain that the transients measured in the double mutant are due to electron transfer between the quinones because the time scale of these transients is comparable to that for protein relaxation events associated with the P Q state (Tiede and Hanson, this volume), and the kinetics were not sensitive to inhibitors such as < -phenanthroline or atrazine. However, the loss of sensitivity to inhibitors may be a consequence of the amino acid replacements in the Qg site. A lower sensitivity to inhibitors was also seen for some of the revertant strains. In addition, the transient spectra associated with these kinetics were consistent with to Qg electron transfer. 

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