Push-pull dyes

Hrobarik, P., Zahradnik, P., Fabian, W.M.F. Computational design of benzothiazole-derived push-pull dyes with high molecular quadratic hyperpolarizabiUties. Phys. Chem. Chem. Phys. 6, 495—501 (2004)... 

Figure 1.3. Examples of push-pull dyes used in PISs a) UV-vis absorption spectra and b) typical polymerization profiles for emission wavelength 473 nm...

Fig. 11 Zinc porphyrin complexes used for Push-Pull dye sensitizer...

The asymmetrical D-ji-A dyes, often referred to as push-pull polyenes, are an additional class of cyanine-like molecules of interest. Due to their dipolar nature, the linear and nonlinear optical properties of this series of dyes can be strongly influenced by solvent polarity [84]. The structures of a series of such dyes (G19,... 

Ros-Lis JV, Martmez-Manez R, Sancenon F et al (2007) Signalling mechanisms in anion-responsive push-pull chromophores the hydrogen-bonding, deprotonation and anion exchange chemistry of functionalized azo dyes. Eur J Org Chem 2449-2458... 

Electron withdrawing substituents such as aldehyde or imonium functions at the other end of the alkene or the 1,3-diene transform enamines and 1,3-dienamines into push-pull systems characteristic of dyes. Electron release (push) of the donor group shields the / , S, e,... carbons and electron withdrawal (pull) of the acceptor group (carbonyl oxygen or imonium nitrogen) deshields in the a, y,... position [343],... 

Based on the BOA theory, Barzoukas and Blanchard-Desce developed a two-state two-form model for the Pq of push-pull compounds [48]. The y o was expressed as a function of the newly defined parameter MIX, which is related to the degree of mixing between the neutral and zwitterionic resonance forms in the ground and excited state. This treatment has the advantage of conceptual simplicity and that it relies on a structural parameter that can be more easily used for other push pull molecular systems than polyenes. The evolution of y o observed with MIX is identical to that with BOA. The BOA theory was later also used to optimize the figure-of-merit of dyes for photorefractive applications [49, 50]. 

This system of equations shows, through even orders, that polarized light irradiation creates anisotropy and photo-orientation by photoisomerization. A solution to the time evolution of the cis and trans expansion parameters cannot be found without approximations this is when physics comes into play. Approximate numerical simulations are possible. 1 will show that for detailed and precise comparison of experimental data with the photo-orientation theory, it is not necessary to have a solution for the dynamics, even in the most general case where there is not enough room for approximations, i.e., that of push-pull azo dyes, such as DRl, because of the strong overlap of the linear absorption spectra of the cis and trans isomers of such chromophores. Rigorous analytical expressions of the steady-state behavior and the early time evolution provide the necessary tool for a full characterization of photo-orientation by photoisomerization. 

A similar behavior (not shown) was found for an azobenzene self assembled monolayer. The value of Q2 can be estimated by comparing reorientation measurements to Equation 3.28. In the next section, I discuss the photoorientation of push-pull azo dyes. 

Sekkat Zoufaeit Knoesen Andre, Lee Victor Y., and Miller Robert D. Observation of reversible photochemical blow out of the third-order molecular hypcrpolarizabilirt- of push-pull azo dye in high glass transition temperature./. Phys. Chem. B 1997, p. 4733-47.19. 

In this contribution we discuss mm based on pp chromophores, a very interesting class of molecules for applications in molecular photonics and electronics. Push-pull chromophores are both polar and polarizable and this makes the role of intermolecular interactions particularly important. The toy model we propose for clusters of pp chromophores neglects intermolecular overlap, just accounting for classical electrostatic intermolecular interactions, and describes each pp chromophore based on a two state model. The two-state model for pp chromophores has been discussed and validated via an extensive comparison with the spectroscopic properties of several dyes in solution [74, 75, 90], The emerging picture is safe and led to the definition of a reliable set of molecular parameters for selected dyes. This analysis then offers valuable information to be inserted into models for clusters of interacting chromophores, in a the bottom-up modeling strategy that was nicely exemplified in Ref. [90]. 

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