Push-pull chromophores

Polymers and supermolecules modified using electron push-pull chro-mophores are also of particular interest for nonlinear optics (NLO) [10-15]. NLO material has attracted much interest over the past 20 years and has been widely applied in various field (telecommunications, optical data storage, information processing, microfabrication, etc.). Chemists have developed ways to introduce NLO chromophores into many type of polymers, such as Hnear polymers, cross-linked polymers, and branched polymers, and have demonstrated their performance in NLO appHcations. 

Sutherland RL, Brant MC, Heinrichs J, Rogers JE, Slagle JE, McLean DG, Fleitz PA (2005) Excited-state characterization and effective three-photon absorption model of two-photon-induced excited-state absorption in organic push-pull charge-transfer chromophores. J Opt... 

Push-push/pull-pull chromophores 118 and 119 have exhibited material properties to show their prospect for several applications particularly in the fields of two-photon microscopy and optical power limitation <1999CC2055, 2002SM17>. 

A synthesis and physicochemical characterization, including molecular second-order nonlinear optical properties, of new push-pull-based chromophores 170 properly functionalized for polymerization and containing oxadiazole rings were reported <2002J(P2)1791>. 

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... 

The ultraviolet absorption spectra of a number of untwisted and twisted compounds of the types 5, 6 and 7 have been studied43,45 and found to be compatible with the chromophore in the acceptor part. The same was found for the photoelectron spectra of a series of more or less twisted simple push-pull ethylenes56. 

Organometallic systems such as porphyrines have been investigated because of the possibility to fine tune their response by functionalization[105-107]. Systems of increased the dimensionality have been of particular interest [108-111], Concomitant to the large effort to establish useful structure-to-properties relationships, considerable effort has now been put to investigate the environmental effects on TPA[112-114], For example, the solvent effect has been studied for a small linear push-pull chromophore using a self-consistent reaction field (homogeneous solvation) method employing a spherical cavity and an internal force field (IFF) method[l 12] in another study the polarizable continuum model has been employed to calculate the relevant quantities to obtain the TPA cross-section in the limit of a two-state model[113] Woo et al. made a critical study of experimental comparison of TPA cross-sections in different solvents[114]. 

Aminovinylnitrothiophenes 84, a novel type of push-pull chromophores, were closely investigated with respect to their NLO and thermal properties [82]. Hyper-Rayleigh scattering (HRS) measurements at a fundamental of 1500 nm re-... 

Furthermore, selected push-pull chromophores 84 were investigated by differential scanning calorimetry (DSC), revealing relatively low glass transition temperatures, Tg, a favorable property for composites in photorefractive materials [83],... 

One-pot, three-component synthesis of the push-pull chromophore 87e by a Sonogashira coupling-aminovinylation sequence [84]... 

Density functional theory (DFT) calculations of two types of push-pull chromophores built around thiophene-based 7t-conjugating spacers rigidified by either covalent bonds or noncovalent intramolecular interactions (Figure 6) have been carried out to assign the relevant electronic and vibrational features and to derive useful information about the molecular structure of these NLO-phores <2003CEJ3670>. 

Wu lY, Lin JT, Li CS, Wang WC, Huang TH, Wen YS, Chow T, Tsai C (1999) Preparation of push-pull type chromophores via nitrothiophene induced Michael type reaction of aUcynes. Tetrahedron 55 13973-13982... 

Karpov AS, Rominger F, Miiller TJJ (2003) Facile one-pot coupling-aminovinylation approach to push-pull chromophores - alkyne activation by sonogashira-coupling. J Org Chem 68 1503-1511... 

Shavaleev, N.M., Scopelliti, R., Gumy, R, andBunzli, J.C.G. (2008) Visible-light excitation of infrared lanthanide luminescence via intra-ligand charge-transfer state in 1,3-diketonates containing push-pull chromophores. European Journal of Inorganic Chemistry, (9), 1523-1529. 

Section 3.2 of this chapter recalls the pure photochemical point of view of photoisomerization of azobenzene derivatives. Section 3.3 discusses the theory of photo-orientation by photoisomerization and gives analytical expressions for the measurement of coupled photoisomerization and photo-orientation parameters. Sections 3.4 and 3.5 review observations of photo-orientation in azobenzene and push-pull azobenzene derivatives, respectively. Among other things, these sections address photo-orientation in both cis and trans isomers and discuss the effect of trans<->cis cycling, i.e., the photochemical quantum yields, on photo-orientation. Section 3.6 discusses the effect of the symmetry of photochemical transitions on photo-orientation in spiropyran and diarylethene-type chromophores. Finally, I make some concluding observations in Section 3.7. 

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. 

Kobko, N., Masunov, A., Trehak, S. CalculaUons of the third-order nonUnear optical responses in push-pull chromophores with a hme-dependent density functional theory. Chem. Phys. Lett. 392, 444 51 (2004)... 

The paper is organized as follows. Section 2 shortly introduces the exciton model and its approximations. Section 3 reviews calculations of ground state properties (mainly the polarization and polarizability) paying special attention to the mean-field approximation. Push-pull chromophores, the special family of polar and polarizable molecules studied in this contribution, are presented in Section 4, with a brief discussion of their properties in solution and of relevant models. In Section 5 we present a model for interacting push-pull chromophores that will be the basis for the discussion of collective and cooperative effects in relevant materials. Static susceptibilities of clusters of push-pull chromophores are discussed in Section 6, focusing attention on cooperative effects in tlie ground state. Excited state properties are addressed in Section 7, with special emphasis to systems where intermolecular interactions lead to extreme consequences. Section 8 finally summarizes main results. 

PUSH-PULL CHROMOPHORES AN INTERESTING FAMILY OF POLAR AND (HYPER-)POLARIZABLE MOLECULES... 

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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