Coupling conjugated chains

The effects of metal-to-metal electronic coupling are observed for several complexes where a ferrocene moiety is bound to transition-metal complexes with a -conjugated chain, 68 (167), 69 (168), and 70 (169). Tertiary amine-ferrocene conjugated molecules, 71, show two-step le oxidation, and their monocationic forms exhibit strong LMCT bands at 600-700 nm (170). 

By extension one may say that the power laws (5-7) which determine the magnitude of the linear and nonlinear optical coefficients are consequences of this strong electron-lattice coupling. We now make the conjecture that the time response of these coefficients is severely affected by the dynamics of the electron-lattice coupling in conjugated chains when two or more resonant chemical structures can coexist this is the case for many of the organic chains of Figure 2. 

Copolymer 459, prepared by Stille coupling of dibromophenylene with 2,5-Mv(tributyl-stannyl)thiophene, represents another example of a phenylene-u/t-thiophene backbone, where the substituted phenylene unit forms an oligophenylene vinylene fragment that is not in the main conjugation chain [561]. A PLED fabricated with this polymer (ITO/459/A1) emitted green light (520 nm) with a turn-on voltage of ca. 9.5 V, but no other data on luminance or efficiency of the device were reported (Chart 2.111). 

However, in all these calculations, the conjugated chains bear H atoms only. As bulkier side groups are introduced, the overall interchain interaction decreases and it becomes more anisotropic. If chains form stacks, relatively strong two-dimensional coupling will persist and may still have consequences similar to those of three-dimensional coupling. The question remains open. But substituted CPs are generally even more disordered than the simple ones, and we shall see now that disorder will then have more important consequences than the details of interchain interaction. 

Monoazo dyes are obtained by a single diazotization and coupling sequence A > E, where A is the primary amine and E is the coupling component. The arrow means dia-zotized and coupled with . Color in part depends on the length of the conjugated chain. 

Having established a correlation between Raman dispersion and conjugation length, a better explanation of the experimental observation is required. The problem has been successfully and thoroughly studied by Horowitz et aL, in terms of the amplitude mode theory (AMT) [30]. The dispersion of the three Raman modes is accounted for, in the AMT, by a parameter X, which expresses the electron-phonon coupling in chains of a given conjugation... 

Since an in-depth discussion of the nature and magnitude of the reorganization energy has been presented in a recent review [9], we will focus in this chapter on the electronic coupling between adjacent ir-conjugated chains and describe some recent developments. 

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